Restoring fish ecological quality in estuaries: Implication of interactive and cumulative effects among anthropogenic stressors

Towards ecosystem-based techniques for tipping point detection

An ecosystem shifts to an alternative stable state when a threshold of accumulated pressure (i.e. direct impact of environmental change or human activities) is exceeded. Detecting this threshold in empirical data remains a challenge because ecosystems are governed by complex interlinkages and feedback loops between their components and pressures. In addition, multiple feedback mechanisms exist that can make an ecosystem resilient to state shifts. Therefore, unless a broad ecological perspective is used to detect state shifts, it remains questionable to what extent current detection methods really capture ecosystem state shifts and whether inferences made from smaller scale analyses can be implemented into ecosystem management. We reviewed the techniques currently used for retrospective detection of state shifts detection from empirical data. We show that most techniques are not suitable for taking a broad ecosystem perspective because approximately 85% do not combine intervariable non-linear relationships and high-dimensional data from multiple ecosystem variables, but rather tend to focus on one subsystem of the ecosystem. Thus, our perception of state shifts may be limited by methods that are often used on smaller data sets, unrepresentative of whole ecosystems. By reviewing the characteristics, advantages, and limitations of the current techniques, we identify methods that provide the potential to incorporate a broad ecosystem-based approach. We therefore provide perspectives into developing techniques better suited for detecting ecosystem state shifts that incorporate intervariable interactions and high-dimensionality data.

Integrating AI and climate change scenarios for multi-risk assessment in the coastal municipalities of the Veneto region

Global climate is experiencing exceptional warming, leading to a rise in extreme events worldwide. Coastal regions are particularly vulnerable to climate change (CC), due to dense populations, interconnected economies, and fragile ecosystems. These areas face escalating risks as CC intensifies the severity and frequency of extreme weather phenomena, like heavy precipitation, sea-level rise (SLR), storm surges. Integrated approaches are crucial to assess the combined impacts of atmospheric and marine hazards at the land-sea interface. Machine Learning (ML) offer innovative solutions to analyse multi-risk events, leveraging large and heterogeneous datasets and modelling complex, non-linear interactions. This study introduces a two-tier ML approach to estimate risks associated with extreme weather events for the Veneto coastal municipalities under current and future scenarios. The model, tested and validated with present-day data, showed satisfactory performance (error margin ∼20 %). The model was applied to mid-term (until 2045) and long-term (until 2100) periods under different CC scenarios, represented by various Representative Concentration Pathways (RCP). Mid-term analysis reveals an increasing risk trend, driven by SLR under RCP8.5, underscoring the significance of considering non-linear interactions between multiple marine and atmospheric hazards. Long-term analysis highlights how future risks depend mainly on precipitation and SLR across the analysed CC scenarios (RCP2.6/4.5/8.5). Results indicate a gradual increase in the expected annual risk trend, with RCP8.5 scenario showing the most severe outcomes. By 2100, the risks under RCP8.5 are projected to be ten times higher than those observed during the historical period, highlighting the importance of developing effective strategies to address these challenges.

Freshwater fish in mid and northern German rivers - Long-term trends and associated species traits

To understand biodiversity change and support conservation decision-making, estimates of species' long-term population trends at regional and national scales are essential. However, such estimates are missing for many freshwater taxa, despite the diverse range of threats that they face. For this study, we mobilised monitoring data on riverine freshwater fish abundance collected across different regions of Germany. We applied generalized mixed effect models to estimate the population trends for 55 native species and 11 non-native species between 2004 and 2020. In addition, we used boosted regression trees to identify trait-based predictors of species trends and assessed their predictive ability. We found evidence of increasing abundance trends for 14 species and decreasing trends for 15 species; while the remaining species were mostly stable (26 species). Native species were more typically decreasing than increasing (14 vs 10 species); while non-native species were more often increasing (4 vs 1 species). Important traits associated with trends were maximum length, spawning temperature, and water quality tolerance, with small species, those spawning at high temperatures, and those preferring unpolluted waters, being most likely to have positive trends. Despite these associations, overall trait-based models showed limited power to predict trends in terms of direction as well as magnitude. Our results highlight the ongoing change in riverine fish communities and the importance of on-going species-level monitoring. The trait-based associations also indicate climate change and invasive species as important drivers of change in European freshwater rivers.

Linking wastewater treatment plant effluents to water quality and hydrology: Effects of multiple stressors on fish communities

Wastewater treatment plants (WWTPs) are essential for maintaining a good water quality of surface waters. However, WWTPs are also associated with water quality deterioration and hydro-morphological alteration. Riverine communities respond to these stressors with changes in their community structure, abundance and diversity. In this study, we used a dataset of 94 monitoring sites across North Rhine-Westphalia, Germany to investigate the influence of WWTPs on the water quality and hydro-morphological quality in river sections downstream of WWTP effluents. More specifically, we analyzed the effects of the percentage of WWTP effluents (in relation to median base flow) on four stressor groups (physico-chemistry, micropollutants, hydrological and morphological alteration) using Linear Mixed Models (LMM). Furthermore, we assessed the impact of a selection of twelve ecologically relevant stressor variables reflecting water quality deterioration and hydro-morphological alteration on reference fish communities using Canonical Correspondence Analysis (CCA). The percentage of WWTP effluents was correlated with water quality, especially with toxic units of a wide range of pharmaceuticals including diclofenac, venlafaxine and sulfamethoxazole (R² up to 0.54) as well as specific pesticides (e.g., terbutryn: R² = 0.33). The correlation of percent WWTP effluents with hydro-morphological alteration was weaker and most pronounced for the frequency of high flow (R² = 0.24) and flow variability (R² = 0.19). About 40 % of the variance in the fish community structure were explained by 12 stressor variables in the CCA models. Water quality and hydrological, but not morphological stressors showed strong albeit highly variable effects on individual fish species. The results indicate that water quality degradation and hydrological alteration are important factors determining the ecological status of fish communities. In this context, WWTP effluents can impose relevant point sources of pollution that affect water quality but also cause alterations of the hydrological regime. Further management measures addressing both stressor groups are needed to improve the ecological status.

Investigating the effects of underwater noise from two vessels on the behaviour of short-finned pilot whales

Multiple whale-watching vessels may operate around cetaceans at any one time, and targeted animals may experience underwater noise effects. We hypothesised that the cumulative noise of two vessels with low source levels (SLs) will elicit lower behavioural disturbance in short-finned pilot whales (Globicephala macrorhynchus) compared to a single vessel with a higher SL. We measured the behaviour of whales during 26 controls (stationary vessel >300 m) and 44 treatments off Tenerife (Canary Islands, Spain). Treatments consisted of vessel approaches mimicking whale-watch scenarios (distance ∼60 m, speed 1.5 kn). Approaches with two simultaneous vessels, with maximum cumulative mid and low-frequency (0.2-110 kHz) weighted source levels (SLsMF-LF) 137-143 dB, did not affect mother-calf pairs' resting, nursing, diving, respiration rate or inter-breath interval. However, a louder single vessel approach with twin petrol engines at SLsMF-LF 139-151 dB significantly decreased the proportion of time resting for the mother. The results suggest that if a single or two vessels are present, if the cumulative SL is < 143 dB, the behavioural disturbance on the whales will be negligible. By examining noise effects from multiple vessels on the behaviour of pilot whales, the importance of incorporating a noise threshold into whale-watching guidelines was emphasised.

Spatial and ontogenetic modulation of fatty acid composition in juvenile European sea bass (Dicentrarchus labrax) from two French estuaries

This study evaluated how estuary of origin and ontogenetic stage influence the fatty acid (FA) composition in the tissues of wild European sea bass juvenile. We evidenced tissue-specific patterns, with the brain exhibiting a distinct FA composition from the liver and muscle. Ontogenetic stage and estuary influenced the general FA profile, and particularly the essential FA (EFA) like docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and arachidonic acid (ARA) in all tissues. The data also revealed the ability of wild sea bass to modulate, at the molecular level, FA biosynthesis pathways and suggest a potential dietary DHA limitation in the natural environment. The distribution of FA within tissues might reflect shifts in diet, metabolic demands, or adaptations to environmental conditions. This study provides insights about FA dynamics in euryhaline fish during juvenile life stage, improving our understanding of the metabolism need and EFA trophic availability in a changing environment.

Rice-based integrated farming system improves the soil quality, bacterial community structure and system productivity under sub-humid tropical condition

Rice-based integrated farming system improves the productivity and profitability by recycling resources efficiently. In the sub-humid tropics, rice production without sufficient nutrient replenishment often leads to soil health and fertility degradation. There has been very limited research on soil health and fertility after adopting a multi-enterprising rice-based integrated farming system (IFS), notably in the rice-fish-livestock and agroforestry system, when compared to a conventional farming system (CS). Therefore, the present study analyzed the dynamics of soil properties, soil bacterial community structure and their possible interaction mechanisms, as well as their effect on regulating soil quality and production in IFS, IFSw (water stagnant area of IFS) and CS. The results indicated that soil nutrient dynamics, bacterial diversity indices (Shannon index, Simpson index, Chao 1, ACE and Fisher index) and system productivity were higher in IFSw and IFS compared to CS. Moreover, relative operational taxonomic units of dominant bacterial genera (Chloroflexi, Acidobacteria, Verrucomicrobia, Planctomycetes, Cyanobacteria, Crenarchaeota and Gemmatimonadetes) were also higher in IFSw and IFS compared to CS. Mean soil quality index (SQI) was highest in IFSw (0.780 ± 0.201) followed by IFS (0.770 ± 0.080) and CS (0.595 ± 0.244). Moreover, rice equivalent yields (REY) and rice yields were well correlated with the higher levels of soil biological indices (SQIBiol) in IFS. Overall, our results revealed that rice-based IFS improved the soil health and fertility and ensuing crop productivity through positive interaction with soil bacterial communities and nutrient stoichiometry leading to agroecosystem sustainability.

Growth of Pacific staghorn sculpin (Leptocottus armatus) is reduced at contaminated sites in the Lower Duwamish River, Washington

The Lower Duwamish River is a highly industrialized waterway flowing into the densely urbanized Puget Sound waterfront of Seattle, Washington, USA. The river has been profoundly altered from its natural state following more than a century of channelization, recurrent dredging, shoreline armoring, and pollution discharges. As part of a Natural Resource Damage Assessment addressing historical pollution at three designated Superfund sites (i.e., the assessment area), juvenile Pacific staghorn sculpin (Leptocottus armatus) were sampled throughout the lower river in order to evaluate injury from exposure to polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDTs), and butyltins (BTs). Sculpin live in close association with the river sediments within and upriver of the assessment area. Fish were collected for analysis of contaminant concentrations in composited whole bodies and stomach contents, as well as individual fish health metrics including daily somatic growth rates measured from otoliths. Sediment contaminant concentrations were also measured at sites near to fishing locations. Fish growth rates varied from 0.65 to 1.05 mm/day, and were significantly lower at unremediated downriver sites compared to upriver and remediated locations. Sculpin growth rates were negatively correlated with concentrations of PCBs in fish bodies, PAHs in stomach contents, as well as PCBs, DDTs and PAHs in sediment. Mixed effects models for whole-body and stomach content contaminants showed positive correlations between growth rate and water temperature. Temperature was not a significant confounding variable for the relationship between growth rate and sediment contaminants. Overall, these results show that juvenile sculpin are harmed by contaminant exposure in the Lower Duwamish River. Furthermore, this study demonstrates the utility of using paired biological and chemical indicators of pollutant-induced injury in a resident fish to inform a complex Natural Resource Damage Assessment and associated restoration efforts.

What Makes A Bank A Bank? Differences and Commonalities in Credit Calculation, Application, and Risks in Mitigation Banks Targeting Freshwater Fish Species and Associated Ecosystems

Mitigation banking is part of the ever-expanding global environmental market framework that aims to balance negative approved anthropogenic impacts versus third-party provided ecosystem benefits, sold in the form of credits. Given the need to conserve freshwater biodiversity and habitat, banking has received great traction for freshwater species and systems. While extensive reviews and studies have been conducted on evaluating if equivalency between impacts and offset can be achieved, there is almost no research being done on the way credits are being generated and banks are managed to inform future best practice and policy. Synthesizing banking data through cluster analyzes from 26 banks in the United States generating credits for freshwater species and associated systems, we show two generalizable approaches: removing barriers and targeting whole communities. Both address crucial freshwater conservation needs but come with their risks and caveats. Using common characteristics and management practices founded in federal and district level guidance within these two groups, we showcase and conclude that credit generation via barrier removal can be at risk of granting credit generation for too large of an area, leading to over-crediting. Banks targeting whole freshwater communities and accounting for landscape-level interactions and influences can potentially be detrimental for species on an individual level and large-scale credit availability as well as transfer can incentivize non-compliance with the mitigation hierarchy.

Cumulative effects of multiple stressors impact an endangered seagrass population and fish communities

Coastal ecosystems are becoming increasingly threatened by human activities and there is growing appreciation that management must consider the impacts of multiple stressors. Cumulative effects assessments (CEAs) have become a popular tool for identifying the distribution and intensity of multiple human stressors in coastal ecosystems. Few studies, however, have demonstrated strong correlations between CEAs and change in ecosystem condition, questioning its management use. Here, we apply a CEA to the endangered seagrass Posidonia australis in Pittwater, NSW, Australia, using spatial data on known stressors to seagrass related to foreshore development, water quality, vessel traffic and fishing. We tested how well cumulative effects scores explained changes in P. australis extent measured between 2005 and 2019 using high-resolution aerial imagery. A negative correlation between P. australis and estimated cumulative effects scores was observed (R2 = 22 %), and we identified a threshold of cumulative effects above which losses of P. australis became more likely. Using baited remote underwater video, we surveyed fishes over P. australis and non-vegetated sediments to infer and quantify how impacts of cumulative effects to P. australis extent would flow on to fish assemblages. P. australis contained a distinct assemblage of fish, and on non-vegetated sediments the abundance of sparids, which are of importance to fisheries, increased with closer proximity to P. australis. Our results demonstrate the negative impact of multiple stressors on P. australis and the consequences for fish biodiversity and fisheries production across much of the estuary. Management actions aimed at reducing or limiting cumulative effects to low and moderate levels will help conserve P. australis and its associated fish biodiversity and productivity.

Stressors of emerging concern in deep-sea environments: microplastics, pharmaceuticals, personal care products and deep-sea mining

Although most deep-sea areas are remote in comparison to coastal zones, a growing body of literature indicates that many sensitive ecosystems could be under increased stress from anthropogenic sources. Among the multiple potential stressors, microplastics (MPs), pharmaceuticals and personal care products (PPCPs/PCPs) and the imminent start of commercial deep-sea mining have received increased attention. Here we review recent literature on these emerging stressors in deep-sea environments and discuss cumulative effects with climate change associated variables. Importantly, MPs and PPCPs have been detected in deep-sea waters, organisms and sediments, in some locations in comparable levels to coastal areas. The Atlantic Ocean and the Mediterranean Sea are the most studied areas and where higher levels of MPs and PPCPs have been detected. The paucity of data for most other deep-sea ecosystems indicates that many more locations are likely to be contaminated by these emerging stressors, but the absence of studies hampers a better assessment of the potential risk. The main knowledge gaps in the field are identified and discussed, and future research priorities are highlighted to improve hazard and risk assessment.

Evaluating the combined effect of climate and anthropogenic stressors on marine coastal ecosystems: Insights from a systematic review of cumulative impact assessment approaches

Cumulative impacts increasingly threaten marine and coastal ecosystems. To address this issue, the research community has invested efforts on designing and testing different methodological approaches and tools that apply cumulative impact appraisal schemes for a sound evaluation of the complex interactions and dynamics among multiple pressures affecting marine and coastal ecosystems. Through an iterative scientometric and systematic literature review, this paper provides the state of the art of cumulative impact assessment approaches and applications. It gives a specific attention to cutting-edge approaches that explore and model inter-relations among climatic and anthropogenic pressures, vulnerability and resilience of marine and coastal ecosystems to these pressures, and the resulting changes in ecosystem services flow. Despite recent advances in computer sciences and the rising availability of big data for environmental monitoring and management, this literature review evidenced that the implementation of advanced complex system methods for cumulative risk assessment remains limited. Moreover, experts have only recently started integrating ecosystem services flow into cumulative impact appraisal frameworks, but more as a general assessment endpoint within the overall evaluation process (e.g. changes in the bundle of ecosystem services against cumulative impacts). The review also highlights a lack of integrated approaches and complex tools able to frame, explain, and model spatio-temporal dynamics of marine and coastal ecosystems' response to multiple pressures, as required under relevant EU legislation (e.g., Water Framework and Marine Strategy Framework Directives). Progress in understanding cumulative impacts, exploiting the functionalities of more sophisticated machine learning-based approaches (e.g., big data integration), will support decision-makers in the achievement of environmental and sustainability objectives.

Decoupling carry-over effects from environment in fish nursery grounds

Life-history trait expression not only depends on the current environmental constraints, but also on the past ones that shaped traits expressed earlier in life. Such an effect, named carry-over, can occur in fish nursery grounds when juvenile performances after settlement are influenced by their larval traits in combination with conditions experienced in nurseries. To date, the impacts of environmental and human stressors on post-settlement traits have been assessed, but independently from larval traits, so that the contributions of environmental versus carry-over constraints remain unquantified. Here, we used a reconstructive approach based on otolith microstructure to investigate how carry-over and environment affect life-history traits of the European seabass, Dicentrarchus labrax. In the northeast Atlantic Ocean, seabass juveniles were collected in six French estuarine nursery areas with contrasted environmental conditions (water temperature, salinity, food availability, and anthropogenic impacts), and five of their life-history traits across ontogenetic stages were measured (pelagic growth, larval duration, size at settlement, post-settlement growth and body condition). Piecewise structural equation model emphasized the strong co-variation of larval traits in response to food availability and temperature in the pelagic environment, stressing that fast growing larvae are characterized by shorter pelagic larval duration, but larger size at recruitment. However, the magnitude of carry-over effects greatly varied between traits, revealing that larval trait impacts on post-settlement traits remained minor as compared to the nursery environment. In estuarine nurseries, our findings suggest that resource allocation results from a trade-off between somatic growth and energy storage. Fish juveniles exposed to anthropogenic stress or risk of food limitation tended to predominantly invest in storage, whereas individuals in favourable conditions allocated their resources in somatic growth. These findings highlight the importance of heterogeneity in pelagic and nursery environments in understanding trait variations and population dynamic of estuarine dependent fish.

Sparus aurata and Lates calcarifer skin microbiota under healthy and diseased conditions in UV and non-UV treated water

Background

The welfare of farmed fish is influenced by numerous environmental and management factors. Fish skin is an important site for immunity and a major route by which infections are acquired. The objective of this study was to characterize bacterial composition variability on skin of healthy, diseased, and recovered Gilthead Seabream (Sparus aurata) and Barramundi (Lates calcarifer). S. aurata, which are highly sensitive to gram-negative bacteria, were challenged with Vibrio harveyi. In addition, and to provide a wider range of infections, both fish species (S. aurata and L. calcarifer) were infected with gram-positive Streptococcus iniae, to compare the response of the highly sensitive L. calcarifer to that of the more resistant S. aurata. All experiments also compared microbial communities found on skin of fish reared in UV (a general practice used in aquaculture) and non-UV treated water tanks.

Results

Skin swab samples were taken from different areas of the fish (lateral lines, abdomen and gills) prior to controlled infection, and 24, 48 and 72 h, 5 days, one week and one-month post-infection. Fish skin microbial communities were determined using Illumina iSeq100 16S rDNA for bacterial sequencing. The results showed that naturally present bacterial composition is similar on all sampled fish skin sites prior to infection, but the controlled infections (T₁ 24 h post infection) altered the bacterial communities found on fish skin. Moreover, when the naturally occurring skin microbiota did not quickly recover, fish mortality was common following T₁ (24 h post infection). We further confirmed the differences in bacterial communities found on skin and in the water of fish reared in non-UV and UV treated water under healthy and diseased conditions.

Conclusions

Our experimental findings shed light on the fish skin microbiota in relation to fish survival (in diseased and healthy conditions). The results can be harnessed to provide management tools for commercial fish farmers; predicting and preventing fish diseases can increase fish health, welfare, and enhance commercial fish yields.

Supplementary Information

The online version contains supplementary material available at 10.1186/s42523-022-00191-y.

The impact of cumulative stressor effects on uncertainty and ecological risk

To enable environmental management actions to be more effectively prioritized, cumulative effects between multiple stressors need to be accounted for in risk-assessment frameworks. Ecological risk and uncertainty are generally high when multiple stressors occur. In the face of high uncertainty, transparent communication is essential to inform decision-making. The impact of stressor interactions on risk and uncertainty was assessed using generalized linear models for additive and multiplicative effect of six anthropogenic stressors on the abundance of estuarine macrofauna across New Zealand. Models that accounted for multiplicative stressor interactions demonstrated that non-additive effects dominated, had increased explanatory power (6 to 73 % relative increase between models), and thereby reduced the risk of unexpected ecological responses to stress. Secondly, 3D-plots provide important insights in the direction, magnitude and gradients of change, and aid transparency and communication of complex stressor effects. Notably, small changes in a stressor can cause a disproportionally steep gradient of change for a synergistic effect where the tolerance to stressors are lost, and would invoke precautionary management. 3D-plots were able to clearly identify directional shifts where the nature of the interaction changed from antagonistic to synergistic along increasing stressor gradients. For example, increased nitrogen load and exposure caused a shift from positive to negative effect on the abundance of a deposit-feeding polychaete (Magelona). Assessments relying on model coefficient estimates, which provide one effect term, could not capture the complexities observed in 3D-plots and are at risk of mis-identifying interaction types. Finally, visualising model uncertainty demonstrated that although error terms were higher for multiplicative models, they better captured the uncertainty caused by data availability. Together, the steep gradients of change identified in 3D-plots and the higher uncertainty in model predictions in multiplicative models urges more conservative limits to be set for management that account for risk and uncertainty in multiple stressor effects.

Considering the influence of land use/land cover on estuarine biotic richness with Bayesian hierarchical models

The composition of land use/land cover (LULC) in coastal watersheds has many implications for estuarine system ecological function. Land use/land cover can influence allochthonous inputs and can enhance or degrade the physical characteristics of estuaries, which in turn affects estuaries' ability to support local biota. However, these implications for estuaries are often poorly considered when assessing the value of lands for conservation. The focus of research regarding terrestrial and estuarine interfaces often evaluates how LULC may stress estuarine ecosystems, but in this study we sought to understand how LULC may both positively and negatively affect estuaries using measures of observed biotic richness as proxies for estuarine function. We investigated the influence of LULC on estuarine biotic richness with Bayesian hierarchical models using multiple geospatial data sets from 33 estuaries and their associated watersheds along the Gulf of Mexico coastal region of the United States. We designed the hierarchical models with observed species richness of three functional groups (FGs) (i.e., pelagic fishes, forage fishes, and shrimp) from fishery-independent trawl surveys as response variables. We then set salinity and water temperature as trawl-specific covariates and measures of influence from six LULC classes as estuary-specific covariates and allowed the models to vary by estuary, trawl program, salinity, and temperature. The model results indicated that the observed richness of each FG was both positively and negatively associated with different LULC classes, with estuarine wetlands and forested lands demonstrating the strongest positive influences on each FG. The results are generally consistent with past studies, and the modeling framework provides a promising way to systematically quantify LULC linkages with the biotic health of estuaries for the purposes of potentially valuing the estuarine implications of land conservation.

Impacts of chemical stress, season, and climate change on the flounder population of the highly anthropised Seine estuary (France)

The main objective of this study was to improve our knowledge on the responses of fish populations to multistress (diffuse pollution and warming waters) in estuaries. Adult flounders were caught in two estuaries in the Eastern English Channel: the heavily polluted Seine estuary vs the moderately contaminated Canche estuary. Fish samplings were conducted in January just before the reproduction period, and in July when gonads were at rest. The overall rise in coastal winter water temperatures detected over the Channel impairs the flounder's phenology of reproduction in the two estuaries, inducing a delay of maturation process and probably also spawning. The higher liver histopathology index in Seine vs Canche could be the consequence of the fish exposition to a complex cocktail of contaminants in a strongly industrialized estuary. Higher levels of neurotoxicity, gill lipid peroxidation, and liver EROD activity were observed in Seine vs Canche. Furthermore, a possible impairment in mitochondrial metabolism was suggested in the Seine flounder population. We confirmed in this study the potential role of two membrane lipids (sphingomyelin and phosphatidylserine) in the resistance towards oxidative stress in Seine and Canche. Finally, we suggest that the Seine flounder population (and possibly the connected Eastern English Channel flounder populations over the French Coast) could be seriously impacted in the future by multistress: higher winter temperatures and chemical contamination.

Temporal scope influences ecosystem driver-response relationships: A case study of Lake Erie with implications for ecosystem-based management

Understanding environmental driver-response relationships is critical to the implementation of effective ecosystem-based management. Ecosystems are often influenced by multiple drivers that operate on different timescales and may be nonstationary. In turn, contrasting views of ecosystem state and structure could arise depending on the temporal perspective of analysis. Further, assessment of multiple ecosystem components (e.g., biological indicators) may serve to identify different key drivers and connections. To explore how the timescale of analysis and data richness can influence the identification of driver-response relationships within a large, dynamic ecosystem, this study analyzed long-term (1969-2018) data from Lake Erie (USA-Canada). Data were compiled on multiple biological, physical, chemical, and socioeconomic components of the ecosystem to quantify trends and identify potential key drivers during multiple time intervals (20 to 50 years duration), using zooplankton, bird, and fish community metrics as indicators of ecosystem change. Concurrent temporal shifts of many variables occurred during the 1980s, but asynchronous dynamics were evident among indicator taxa. The strengths and rank orders of predictive drivers shifted among intervals and were sometimes taxon-specific. Drivers related to nutrient loading and lake trophic status were consistently strong predictors of temporal patterns for all indicators; however, within the longer intervals, measures of agricultural land use were the strongest predictors, whereas within shorter intervals, the stronger predictors were measures of tributary or in-lake nutrient concentrations. Physical drivers also tended to increase in predictive ability within shorter intervals. The results highlight how the time interval examined can filter influences of lower-frequency, slower drivers and higher-frequency, faster drivers. Understanding ecosystem change in support of ecosystem-based management requires consideration of both the temporal perspective of analysis and the chosen indicators, as both can influence which drivers are identified as most predictive of ecosystem trends at that timescale.

Prioritizing the Effects of Emerging Contaminants on Estuarine Production under Global Warming Scenarios

Due to non-linear interactions, the effects of contaminant mixtures on aquatic ecosystems are difficult to assess, especially under temperature rise that will likely exacerbate the complexity of the responses. Yet, under the current climatic crisis, assessing the effects of water contaminants and temperature is paramount to understanding the biological impacts of mixtures of stressors on aquatic ecosystems. Here, we use an ecosystem model followed by global sensitivity analysis (GSA) to prioritize the effects of four single emerging contaminants (ECs) and their mixture, combined with two temperature rise scenarios, on the biomass production of a NE Atlantic estuary. Scenarios ran for 10 years with a time-step of 0.1 days. The results indicate that macroinvertebrate biomass was significantly explained by the effect of each single EC and by their mixture but not by temperature. Globally, the most adverse effects were induced by two ECs and by the mixture of the four ECs, although the sensitivity of macroinvertebrates to the tested scenarios differed. Overall, the present approach is useful to prioritize the effects of stressors and assess the sensitivity of the different trophic groups within food webs, which may be of relevance to support decision making linked to the sustainable management of estuaries and other aquatic systems.

Evaluation of a popular spatial cumulative impact assessment method for marine systems: A seagrass case study

Human activities put stress on our oceans and with a growing global population, the impact is increasing. Stressors rarely act in isolation, with the majority of marine areas being impacted by multiple, concurrent stressors. Marine spatial cumulative impact assessments attempt to estimate the collective impact of multiple stressors on marine environments. However, this is difficult given how stressors interact with one another, and the variable response of ecosystems. As a result, assumptions and generalisations are required when attempting to model cumulative impacts. One fundamental assumption of the most commonly applied, semi-quantitative cumulative impact assessment method is that a change in modelled cumulative impact is correlated with a change in ecosystem condition. However, this assumption has rarely been validated with empirical data. We tested this assumption using a case study of seagrass in a large, inverse estuary in South Australia (Spencer Gulf). We compared three different seagrass condition indices, based on survey data collected in the field, to scores from a spatial cumulative impact model for the study area. One condition index showed no relationship with cumulative impact, whilst the other two indices had very small, negative relationships with cumulative impact. These results suggest that one of the most commonly used methods for assessing cumulative impacts on marine systems is not robust enough to accurately reflect the effect of multiple stressors on seagrasses; possibly due to the number and generality of assumptions involved in the approach. Future methods should acknowledge the complex relationships between stressors, and the impact these relationships can have on ecosystems. This outcome highlights the need for greater evaluation of cumulative impact assessment outputs and the need for data-driven approaches. Our results are a caution for marine scientists and resource managers who may rely on spatial cumulative impact assessment outputs for informing policy and decision-making.

Assessing Chlorophyll a Spatiotemporal Patterns Combining In Situ Continuous Fluorometry Measurements and Landsat 8/OLI Data across the Barataria Basin (Louisiana, USA)

The acquisition of reliable and accurate data to assess environmental changes over large spatial scales is one of the main limitations to determine the impact of eutrophication, and the effectiveness of management strategies in coastal systems. Here, we used a continuous in situ Chl-a fluorometry sensor and L8/OLI satellite data to develop an algorithm and map Chl-a spatial distribution to assess the impact of freshwater diversions and associated high nutrient loading rates in the Barataria Basin (BB) complex, a coastal system in the northern Gulf of Mexico. We collected water quality samples at 24 sampling stations and high-frequency continuous fluorometry in situ [Chl-a] data along a ~87 km transect from 2019–2020. Field [Chl-a] values were highly correlated (r = 0.86; p < 0.0001) with continuous in situ [Chl-a] fluorometry values. These continuous in situ [Chl-a] values were significantly related to a surface reflectance ratio ([B1 + B4]/B3) estimated using L8/OLI data (exponential model; R2 = 0.46; RMSE = 4.8, p < 0.0001). The statistical model replicated [Chl-a] spatial patterns across the BB complex. This work shows the utility of high-frequency continuous Chl-a fluorometry sampling coupled with L8/OLI image analysis to increase the frequency and number of field data sets to assess water quality conditions at large spatial scales in highly dynamic deltaic regions.

Evaluation of Environmental Quality of Mediterranean Coastal Lagoons Using Persistent Organic Pollutants and Metals in Thick-Lipped Grey Mullet

The evaluation of past and present anthropogenic impacts affecting the ecological quality status of transitional ecosystems is crucial from the perspective of protecting them from further deterioration, and to evaluate remediation and restoration measures. Contamination patterns of thick-lipped grey mullet from two Mediterranean coastal lagoons within a protected area in Italy were assessed and compared in order to evaluate their overall quality status and to collect information that can provide useful feedback on management choices aimed at enhancing environmental quality and biodiversity conservation. The quality status of the two lagoons was evaluated by an environmental assessment methodology based on indicators of direct and indirect human pressures, while a broad range of analyses were carried out to determine the presence and concentration of persistent organic pollutants (POPs) and metals in fish muscle tissue. A good quality status resulted for both lagoons, and an overall limited anthropogenic impact in the surrounding area. This could account for POPs and metal contamination levels found in mullet, although limited, and relating to their patterns. The overlap of results achieved with the two evaluation approaches can provide support for management choices in Mediterranean lagoon environments, especially for those committed to the protection and conservation of biodiversity.

Advances in forecasting harmful algal blooms using machine learning models: A case study with Planktothrix rubescens in Lake Geneva

The development of anthropic activities during the 20th century increased the nutrient fluxes in freshwater ecosystems, leading to the eutrophication phenomenon that most often promotes harmful algal blooms (HABs). Recent years have witnessed the regular and massive development of some filamentous algae or cyanobacteria in Lake Geneva. Consequently, important blooms could result in detrimental impacts on economic issues and human health. In this study, we tried to lay the foundation of an HAB forecast model to help scientists and local stakeholders with the present and future management of this peri-alpine lake. Our forecast strategy was based on pairing two machine learning models with a long-term database built over the past 34 years. We created HAB groups via a K-means model. Then, we introduced different lag times in the input of a random forest (RF) model, using a sliding window. Finally, we used a high-frequency dataset to compare the natural mechanisms with numerical interaction using individual conditional expectation plots. We demonstrate that some HAB events can be forecasted over a year scale. The information contained in the concentration data of the cyanobacteria was synthesized in the form of four intensity groups that directly depend on the P. rubescens concentration. The categorical transformation of these data allowed us to obtain a forecast with correlation coefficients that stayed above a threshold of 0.5 until one year for the counting cells and two years for the biovolume data. Moreover, we found that the RF model predicted the best P. rubescens abundance for water temperatures around 14°C. This result is consistent with the biological processes of the toxic cyanobacterium. In this study, we found that the coupling between K-means and RF models could help in forecasting the development of the bloom-forming P. rubescens in Lake Geneva. This methodology could create a numerical decision support tool, which should be a significant advantage for lake managers.

European aquatic ecological assessment methods: A critical review of their sensitivity to key pressures

The European Union has embarked on a policy which aims to achieve good ecological status in all surface waters (i.e. rivers, lakes, transitional and coastal waters). In theory, ecological status assessment methods should address the effects of all relevant human pressures. In this study, we analyze the degree to which methods European countries use to assess ecological status tackle various pressures affecting European waters. Nutrient pollution is by far the best-covered pressure for all four water categories. Out of total of 423 assessment methods, 370 assess eutrophication and pressure-specific relationships have been demonstrated for 212 of these. "General degradation" is addressed by 238 methods, mostly validated by relationships to combined pressure indices. Other major pressures have received significantly less effort: hydromorphological degradation is assessed by 160 methods and pressure-specific relationships have been demonstrated for just 40 of these. Hydromorphological pressures are addressed (at least by one BQE) only by 25% countries for coastal waters and 70-80% for lakes and transitional waters. Specific diagnostic tools (i.e. single-pressure relationships) for hydromorphology have only been developed by a few countries: only 20% countries have such methods for lakes, coastal and transitional waters and less than half for rivers. Toxic contamination is addressed by 90 methods; however, pressure-specific relationships have been demonstrated for just eight of these. Only two countries have demonstrated pressure-specific acidification methods for rivers, and three for lakes. In summary, methods currently in use mostly address eutrophication and/or general degradation, but there is not much evidence that they reliably pick up the effects of other significant pressures such as hydromorphology or toxic contamination. Therefore, we recommend that countries re-examine: (1) those pressures which affect different water categories in the country; (2) relevant assessment methods to tackle those pressures; (3) whether pressure-response relationships have been developed for each of these.

Spatial-temporal genome damaging in the blue crab Cardisoma guanhumi as ecological indicators for monitoring tropical estuaries

In this study, to better our understanding of the current state of conservation of Cardisoma guanhumi and its habitats, we evaluated the potential spatio-temporal genomic damage of this species across five estuaries in Brazil. The experiment was performed over two consecutive years, and the sampling was performed in the winter and summer seasons. Two genetic tests - micronucleus test and comet assay - were used to quantify the DNA damage. Unlike in the summers and in the winter of 2013, in the winter of 2012 a significant increase was noted in the frequency of micronucleated cells and genomic damage index. The occurrence of genomic damage coincided with the arrival of the harsh winter of 2012 as the water sourced from the coastal rivers significantly affected the estuarine species under study. Our results confirmed that this species was resilient to the atypical climatic conditions, which facilitated the generation of excessive waste.

Relative impacts of multiple human stressors in estuaries and coastal waters in the North Sea-Baltic Sea transition zone

The objectives of this study are 1) to map the potential cumulative impacts of multiple human activities and stressors on the ecosystems in the transition zone between the North Sea and Baltic Sea, for Danish waters 2) to analyse differences in stressor contribution between the European Union's Marine Strategy Framework Directive (MSFD, off-shore waters) and Water Framework Directive (WFD, coastal waters), and 3) to assess the local relative importance of stressors for 14 areas along a land-sea gradient, from inner fjords or coastal areas to offshore waters. The mapping of cumulative impacts is anchored in 35 datasets describing a broad range of human stressors and 47 ecosystem components ranging from phytoplankton over benthic communities to fish, seabirds and marine mammals, which we combined by means of a widely used spatial human impact model. Ranking of the stressor impacts for the entire study area revealed that the top five stressors are: 'Nutrients', 'Climate anomalies', 'Non-indigenous species', 'Noise' and 'Contaminants'. The gradient studies showed that some stressors (e.g. 'Nutrients', 'Shipping' and 'Physical modification') have a relatively higher impact within the fjord/estuarine systems whilst others (e.g. 'Fisheries', 'Contaminants' and 'Noise') have relatively higher impact in the open waters. Beyond mapping of cumulative human impacts, we discuss how the maps can be used as an analytical tool to inform ecosystem-based management and marine spatial planning, using the MSFD and WFD as examples.

Using cumulative human-impact models to reveal global threat patterns for seahorses

Understanding threats acting on marine organisms and their conservation status is vital but challenging given a paucity of data. We studied the cumulative human impact (CHI) on and conservation status of seahorses (Hippocampus spp.)-a genus of rare and data-poor marine fishes. With expert knowledge and relevant spatial data sets, we built linear-additive models to assess and map the CHI of 12 anthropogenic stressors on 42 seahorse species. We examined the utility of indices of estimated impact (impact of each stressor and CHI) in predicting conservation status for species with random forest (RF) models. The CHI values for threatened species were significantly higher than those for nonthreatened species (category based on International Union for Conservation of Nature Red List). We derived high-accuracy RF models (87% and 96%) that predicted that 5 of the 17 data-deficient species were threatened. Demersal fishing practices with high bycatch and pollution were the best predictors of threat category. Major threat epicenters were in China, Southeast Asia, and Europe. Our results and maps of CHI may help guide global seahorse conservation and indicate that modeling and mapping human impacts can reveal threat patterns and conservation status for data-poor species. We found that for exploring threat patterns of focal species, species-level CHI models are better than existing ecosystem-level CHI models.

After decades of stressor research in urban estuarine ecosystems the focus is still on single stressors: A systematic literature review and meta-analysis

Natural systems are threatened by a variety of anthropogenic stressors and so understanding the interactive threats posed by multiple stressors is essential. In this study we focused on urban stressors that are ubiquitous to urban estuarine systems worldwide: elevated nutrients, toxic chemical contaminants, built infrastructure and non-indigenous species (NIS). We investigated structural (abundance, diversity and species richness) and functional endpoints (productivity, primary production (chlorophyll-a) and metabolism) commonly used to determine responses to these selected stressors. Through a systematic review of global literature, we found 579 studies of our selected stressors; 93% measured responses to a single stressor, with few assessing the effects of multiple stressors (7%). Structural endpoints were commonly used to measure the effects of stressors (49% of the total 579 studies). Whereas, functional endpoints were rarely assessed alone (10%) but rather in combination with structural endpoints (41%). Elevated nutrients followed by NIS were the most studied single stressors (43% and 16% of the 541 single stressor studies), while elevated nutrients and toxic contaminants were overwhelmingly the most common stressor combination (79% of the 38 multiple stressor studies); with NIS and built infrastructure representing major gaps in multi-stressor research. In the meta-analysis, structural endpoints tended to decrease, while functional endpoints increased and/or decreased in response to different types of organisms or groups. We predicted an antagonistic effect of elevated nutrients and toxic contaminants based on the opposing enriching versus toxic effects of this stressor combination. Of note, biodiversity was the only endpoint that revealed such an antagonistic response. Our results highlight the continuing paucity of multiple stressor studies and provide evidence for opposing patterns in the responses to single and interacting stressors depending on the measured endpoint. The latter is of significant consequence to understanding relevant impacts of stressors in coastal monitoring and management.

Establishing nutrient thresholds in the face of uncertainty and multiple stressors: A comparison of approaches using simulated datasets

Various methods have been proposed to identify threshold concentrations of nutrients that would support good ecological status, but the performance of these methods and the influence of other stressors on the underlying models have not been fully evaluated. We used synthetic datasets to compare the performance of ordinary least squares, logistic and quantile regression, as well as, categorical methods based on the distribution of nutrient concentrations categorised by biological status. The synthetic datasets used differed in their levels of variation between explanatory and response variables, and were centered at different positions along the stressor (nutrient) gradient. In order to evaluate the performance of methods in "multiple stressor" situations, another set of datasets with two stressors was used. Ordinary least squares and logistic regression methods were the most reliable when predicting the threshold concentration when nutrients were the sole stressor; however, both had a tendency to underestimate the threshold when a second stressor was present. In contrast, threshold concentrations produced by categorical methods were strongly influenced by the level of the stressor (nutrient enrichment, in this case) relative to the threshold they were trying to predict (good/moderate in this instance). Although all the methods tested had limitations in the presence of a second stressor, upper quantiles seemed generally appropriate to establish non-precautionary thresholds. For example, upper quantiles may be appropriate when establishing targets for restoration, but not when seeking to minimise deterioration. Selection of an appropriate threshold concentration should also attend to the regulatory regime (i.e. policy requirements and environmental management context) within which it will be used, and the ease of communicating the principles to managers and stakeholders.

MODELPlastics workshop - Modelling Ocean Plastic Litter in a Changing Climate: Gaps and future directions

Here we summarize the overarching issues that emerged from a workshop held to discuss scientific challenges and future directions on the use of numerical models to predict the amount, distribution and effects of plastic pollution on marine ecosystems. The need for multi-disciplinary approaches, standardized protocols for plastic quantification and analyses, using realistic contaminant concentrations in laboratorial experiments and targeting early-life stages of marine organisms were pointed out as needs to improve data accuracy. Participants also enumerated a list of gaps that include, identification of indicator organisms of plastic contamination, selection of biomarkers and the role of extreme events on plastic dynamics. Responding to these gaps will contribute to improve data quantity and quality and, thus, allow developing more reliable models. A crucial role is foreseen for modelling tools as they can incorporate the cumulative impacts of multiple stressors, including the individual-level effects of plastics, to the population- and ecosystem level.

Food deprived largemouth bass (Micropterus salmoides) are inactive and stressed, but do not show changes in lure inspections

Coping style traits, including physiology and behavior, can be used to predict if fish are vulnerable to capture by hook-and-line angling. Typically, fish with proactive coping styles are selectively captured, but effects of environmental influences, such as food availability, on the completion of each step leading to a successful angling capture (i.e., activity rates, encountering a lure, lure inspection, lure-striking, and ingestion) have not been quantified. Therefore, the objective of this study was to quantify the effects among activity behavior, stress (cortisol) responsiveness, and food availability on lure inspection behaviors of largemouth bass. No relationships were found between activity, stress responsiveness, and food availability to determine lure inspections. However, food deprivation decreased activity rates and increased baseline cortisol concentrations of largemouth bass. Additionally, after feeding treatments, fish with low baseline cortisol concentrations were more likely to inspect lures in both the fed and food deprived treatments. Results further discuss the implications of study findings to help fisheries managers predict the evolutionary impacts of angling.

Synergistic Effects of Climate Change and Marine Pollution: An Overlooked Interaction in Coastal and Estuarine Areas

Coastal areas have been increasingly affected by human activities, marine pollution and climate change are among the most important pressures affecting these environments. Human-induced pressures occur in a cumulative way and generate additive, antagonistic or synergistic effects. Knowledge on synergistic effects is crucial to coastal zone management, since they may imply a change in human uses of these systems, as well as dedicated action plans in order to reduce hazards and environmental risks. In this work, we provide an overview of the available literature on synergistic effects between climate change and chemical pollution, and discuss current knowledge, methodological approaches, and research gaps and needs. Interactions between these two pressures may be climate change dominant (climate change leads to an increase in contaminant exposure or toxicity) or contaminant-dominant (chemical exposure leads to an increase in climate change susceptibility), but the mechanistic drivers of such processes are not well known. Results from a few meta-analyses studies and reviews showed that synergistic interactions tend to be more frequent compared to additive and antagonistic ones. However, most of the studies are individual-based and assess the cumulative effects of a few contaminants individually in laboratory settings together with few climate variables, particularly temperature and pH. Nevertheless, a wide diversity of contaminants have already been individually tested, spanning from metals, persistent organic pollutants and, more recently, emergent pollutants. Population and community based approaches are less frequent but have generated very interesting and more holistic perspectives. Methodological approaches are quite diverse, from laboratory studies to mesocosm and field studies, or based on statistical or modelling tools, each with their own potential and limitations. More holistic comparisons integrating several pressures and their combinations and a multitude of habitats, taxa, life-stages, among others, are needed, as well as insights from meta-analyses and systematic reviews.

Expected Shifts in Nekton Community Following Salinity Reduction: Insights into Restoration and Management of Transitional Water Habitats

A restoration project is planned to take place in the northern Venice lagoon (northern Adriatic Sea, Italy), aiming at introducing freshwater into a confined shallow water lagoon area and recreating transitional water habitats. This work describes the shifts in the nekton (fish and decapods) community structure to be expected following the future salinity decrease in the restoration area. Nekton was sampled at a series of natural shallow water sites located along salinity gradients in the Venice lagoon. A multivariate GLM approach was followed in order to predict species biomass under the salinity and environmental conditions expected after restoration. Biomass of commercially important species, as well as species of conservation interest, is predicted to increase following salinity reduction and habitat changes. From a functional perspective, an increase in biomass of hyperbenthivores-zooplanctivores, hyperbenthivores-piscivores and detritivores is also expected. This study emphasises the efficacy of a predictive approach for both ecological restoration and ecosystem management in transitional waters. By providing scenarios of community structure, the outcomes of this work could be employed in future evaluations of restoration success in the Venice lagoon, as well as to develop management tools to forecast the effects of alterations of salinity regimes in coastal lagoons due to climate change.

Protecting and restoring Europe's waters: An analysis of the future development needs of the Water Framework Directive

The Water Framework Directive (WFD) is a pioneering piece of legislation that aims to protect and enhance aquatic ecosystems and promote sustainable water use across Europe. There is growing concern that the objective of good status, or higher, in all EU waters by 2027 is a long way from being achieved in many countries. Through questionnaire analysis of almost 100 experts, we provide recommendations to enhance WFD monitoring and assessment systems, improve programmes of measures and further integrate with other sectoral policies. Our analysis highlights that there is great potential to enhance assessment schemes through strategic design of monitoring networks and innovation, such as earth observation. New diagnostic tools that use existing WFD monitoring data, but incorporate novel statistical and trait-based approaches could be used more widely to diagnose the cause of deterioration under conditions of multiple pressures and deliver a hierarchy of solutions for more evidence-driven decisions in river basin management. There is also a growing recognition that measures undertaken in river basin management should deliver multiple benefits across sectors, such as reduced flood risk, and there needs to be robust demonstration studies that evaluate these. Continued efforts in 'mainstreaming' water policy into other policy sectors is clearly needed to deliver wider success with WFD goals, particularly with agricultural policy. Other key policy areas where a need for stronger integration with water policy was recognised included urban planning (waste water treatment), flooding, climate and energy (hydropower). Having a deadline for attaining the policy objective of good status is important, but even more essential is to have a permanent framework for river basin management that addresses the delays in implementation of measures. This requires a long-term perspective, far beyond the current deadline of 2027.

Water resource management and public preferences for water ecosystem services: A choice experiment approach for inland river basin management

The concept of ecosystem services provides a valuable approach for linking humans and nature and for supporting the protection of natural ecosystems. River water services, which influence public health and daily routines, have both social and ecological benefits to a surrounding area. However, river networks and their services have suffered extensive destruction due to urbanization and industrialization, especially in China. An assessment of river system benefits and recognition of public preferences are crucial for sustainable river management and effective river system restoration. The objective of this study was to assess a household's willingness to pay using a choice experiment (CE) with mixed logit and multinomial logit models. This technique was applied to evaluate a respondent's preferences regarding water service attributes such as upper basin, middle basin and lower basin ecological water distribution; water quality; and payment and the possible source of heterogeneity in these attributes. The estimated likelihood ratio test demonstrated that random parameter logit model (RPL) models had considerably more explanatory power than multinomial logit (MNL) models. It was also revealed that the RPL-II model was the most powerful among all the models, demonstrating the capability of that model to predict the choices of the respondents. Furthermore, the findings show that water quality was the most preferred river attribute, and households were willing to pay more for the water quality attribute that derives the highest marginal value. Household income level, residential location, education level, and sex were the main factors influencing willingness to pay. These assessments provide guidance, policy recommendations and a reference for researchers and policy makers to improve and enhance current river water services in the future.

Understanding multiple stressors in a Mediterranean basin: Combined effects of land use, water scarcity and nutrient enrichment

River basins are extremely complex hierarchical and directional systems that are affected by a multitude of interacting stressors. This complexity hampers effective management and conservation planning to be effectively implemented, especially under climate change. The objective of this work is to provide a wide scale approach to basin management by interpreting the effect of isolated and interacting factors in several biotic elements (fish, macroinvertebrates, phytobenthos and macrophytes). For that, a case study in the Sorraia basin (Central Portugal), a Mediterranean system mainly facing water scarcity and diffuse pollution problems, was chosen. To develop the proposed framework, a combination of process-based modelling to simulate hydrological and nutrient enrichment stressors and empirical modelling to relate these stressors - along with land use and natural background - with biotic indicators, was applied. Biotic indicators based on ecological quality ratios from WFD biomonitoring data were used as response variables. Temperature, river slope, % of agriculture in the upstream catchment and total N were the variables more frequently ranked as the most relevant. Both the two significant interactions found between single hydrological and nutrient enrichment stressors indicated antagonistic effects. This study demonstrates the potentialities of coupling process-based modelling with empirical modelling within a single framework, allowing relationships among different ecosystem states to be hierarchized, interpreted and predicted at multiple spatial and temporal scales. It also demonstrates how isolated and interacting stressors can have a different impact on biotic quality. When performing conservation or management plans, the stressor hierarchy should be considered as a way of prioritizing actions in a cost-effective perspective.

Habitat risk assessment for regional ocean planning in the U.S. Northeast and Mid-Atlantic

Coastal habitats provide important benefits to people, including habitat for species targeted by fisheries and opportunities for tourism and recreation. Yet, such human activities also can imperil these habitats and undermine the ecosystem services they provide to people. Cumulative risk assessment provides an analytical framework for synthesizing the influence of multiple stressors across habitats and decision-support for balancing human uses and ecosystem health. To explore cumulative risk to habitats in the U.S. Northeast and Mid-Atlantic Ocean Planning regions, we apply the open-source InVEST Habitat Risk Assessment model to 13 habitats and 31 stressors in an exposure-consequence framework. In doing so, we advance the science priorities of EBM and both regional planning bodies by synthesizing the wealth of available data to improve our understanding of human uses and how they affect marine resources. We find that risk to ecosystems is greatest first, along the coast, where a large number of stressors occur in close proximity and secondly, along the continental shelf, where fewer, higher consequence activities occur. Habitats at greatest risk include soft and hard-bottom nearshore areas, tidal flats, soft-bottom shelf habitat, and rocky intertidal zones-with the degree of risk varying spatially. Across all habitats, our results indicate that rising sea surface temperatures, commercial fishing, and shipping consistently and disproportionally contribute to risk. Further, our findings suggest that management in the nearshore will require simultaneously addressing the temporal and spatial overlap as well as intensity of multiple human activities and that management in the offshore requires more targeted efforts to reduce exposure from specific threats. We offer a transparent, generalizable approach to evaluating cumulative risk to multiple habitats and illustrate the spatially heterogeneous nature of impacts along the eastern Atlantic coast and the importance of spatial scale in estimating such impacts. These results offer a valuable decision-support tool by helping to constrain the decision space, focus attention on habitats and locations at the greatest risk, and highlight effect management strategies.

Can we assess the ecological status of estuaries based on larval fish assemblages?

Fish larvae of four SE Brazilian estuaries were investigated to assess if the larval fish assemblages reflect the ecological status of estuaries. All samples were collected in the same water mass to guarantee similar natural water parameters, assuring that major differences among estuaries were related to anthropogenic pressures. Water temperature, oxygen, pH, chlorophyll a, faecal coliforms, nutrient load and total particulate matter were obtained at each sampling area. A pressure index was used to assess the overall anthropogenic pressures acting in each estuary. Results showed that fish larvae were sensitive to water contamination, reducing the diversity and especially exhibiting a high dominance of few species. Furthermore, this study reinforced the idea that the high sensitivity of fish larvae can increase the accuracy of the environmental assessments when tackling short-time events of hydrological controls (physical barriers and control of the freshwater input), representing an advance in the water ecological quality assessments.

Human pressures and ecological status of European rivers

Humans have increased the discharge of pollution, altered water flow regime and modified the morphology of rivers. All these actions have resulted in multiple pressures on freshwater ecosystems, undermining their biodiversity and ecological functioning. The European Union has adopted an ambitious water policy to reduce pressures and achieve a good ecological status for all water bodies. However, assessing multiple pressures on aquatic ecosystems and understanding their combined impact on the ecological status is challenging, especially at the large scale, though crucial to the planning of effective policies. Here, for the first time, we quantify multiple human pressures and their relationship with the ecological status for all European rivers. We considered ecological data collected across Europe and pressures assessed by pan-European models, including pollution, hydrological and hydromorphological alterations. We estimated that in one third of EU’s territory rivers are in good ecological status. We found that better ecological status is associated with the presence of natural areas in floodplains, while urbanisation and nutrient pollution are important predictors of ecological degradation. We explored scenarios of improvement of rivers ecological status for Europe. Our results strengthen the need to halt urban land take, curb nitrogen pollution and maintain and restore nature along rivers.

Assessing the cumulative environmental effects of marine renewable energy developments: Establishing common ground

Assessing and managing the cumulative impacts of human activities on the environment remains a major challenge to sustainable development. This challenge is highlighted by the worldwide expansion of marine renewable energy developments (MREDs) in areas already subject to multiple activities and climate change. Cumulative effects assessments in theory provide decision makers with adequate information about how the environment will respond to the incremental effects of licensed activities and are a legal requirement in many nations. In practise, however, such assessments are beset by uncertainties resulting in substantial delays during the licensing process that reduce MRED investor confidence and limit progress towards meeting climate change targets. In light of these targets and ambitions to manage the marine environment sustainably, reducing the uncertainty surrounding MRED effects and cumulative effects assessment are timely and vital. This review investigates the origins and evolution of cumulative effects assessment to identify why the multitude of approaches and pertinent research have emerged, and discusses key considerations and challenges relevant to assessing the cumulative effects of MREDs and other activities on ecosystems. The review recommends a shift away from the current reliance on disparate environmental impact assessments and limited strategic environmental assessments, and a move towards establishing a common system of coordinated data and research relative to ecologically meaningful areas, focussed on the needs of decision makers tasked with protecting and conserving marine ecosystems and services.

An integrated assessment framework for the analysis of multiple pressures in aquatic ecosystems and the appraisal of management options

The contribution illustrates an integrated assessment framework aimed at evaluating the relationships between multiple pressures and water body status for the purposes of river basin management. The framework includes the following steps. (1) Understanding how the different pressures affect the status of water bodies. This entails the characterization of biophysical state variables and the definition of a causal relationship between pressures and status. Therefore this step involves interaction between experts bearing ecological understanding and experts providing models to represent the effect of pressures. (2) Identifying the relevant pressures to be addressed through appropriate measures to improve the status of water bodies. (3) Evaluating reduction targets for the relevant pressures identified in a river basin, by weighting the effort associated to reducing individual pressures and the potential benefits in terms of water body status. (4) Designing management measures through a creative process and political discussion of alternative options, balancing costs, benefits and effectiveness based on engineering and economic analysis. (5) Simulating scenarios of implementation of a programme of measures in order to check their effectiveness and robustness against climate and land use change. We discuss the five steps of the assessment framework, and particularly the interaction between science and policy at the different stages. We review the assessment tools required at each step and, for setting optimal pressure reduction targets (step 3), we propose and illustrate a simplified multicriteria approach based on semi-quantitative assessment, which produces frontiers of optimal trade-offs between effort spent on measures, and achievements.

Untangling the effects of multiple human stressors and their impacts on fish assemblages in European running waters

This work addresses human stressors and their impacts on fish assemblages at pan-European scale by analysing single and multiple stressors and their interactions. Based on an extensive dataset with 3105 fish sampling sites, patterns of stressors, their combination and nature of interactions, i.e. synergistic, antagonistic and additive were investigated. Geographical distribution and patterns of seven human stressor variables, belonging to four stressor groups (hydrological-, morphological-, water quality- and connectivity stressors), were examined, considering both single and multiple stressor combinations. To quantify the stressors' ecological impact, a set of 22 fish metrics for various fish assemblage types (headwaters, medium gradient rivers, lowland rivers and Mediterranean streams) was analysed by comparing their observed and expected response to different stressors, both acting individually and in combination. Overall, investigated fish sampling sites are affected by 15 different stressor combinations, including 4 stressors acting individually and 11 combinations of two or more stressors; up to 4 stressor groups per fish sampling site occur. Stressor-response analysis shows divergent results among different stressor categories, even though a general trend of decreasing ecological integrity with increasing stressor quantity can be observed. Fish metrics based on density of species 'intolerant to water quality degradation' and 'intolerant to oxygen depletion" responded best to single and multiple stressors and their interactions. Interactions of stressors were additive (40%), synergistic (30%) or antagonistic (30%), emphasizing the importance to consider interactions in multi-stressor analyses. While antagonistic effects are only observed in headwaters and medium-gradient rivers, synergistic effects increase from headwaters over medium gradient rivers and Mediterranean streams to large lowland rivers. The knowledge gained in this work provides a basis for advanced investigations in European river basins and helps prioritizing further restoration and management actions.

'The past is the future of the present': Learning from long-time series of marine monitoring

Using a long-term (1995-2014) monitoring network, from 51 sampling stations in estuaries and coasts of the Basque Country (Bay of Biscay), the objective of this investigation was to assess the responsiveness of 83 variables in water (18), sediments (27), biota (26), phytoplankton (2), macroinvertebrates (5) and fishes (5) to different human pressures and management actions. We used a total of 3247 series of data to analyse trends of improvement and worsening in quality. In a high percentage of the cases, the management actions taken have resulted in positive effects in the environment, as shown by the trend analysis in this investigation. Overall, much more trends of improvement than of worsening have been observed; this is true for almost all the media and biological components studied, with the exception of phytoplankton; and it applies as well to almost all the stations and water bodies, with the exception of those corresponding to areas with water treatment pending of accomplishment. In estuaries with decreasing human pressures during the period, the percentage of series showing quality improvement was higher (approx. 30%) than those showing worsening of quality (12%). Moreover, in those water bodies showing an increase of pressure, variables which can be considered indicators of anthropogenic effects showed negative trends (quality worsening). On the other hand, some of the variables analysed were more affected by natural variability than by changes in pressures. That was the case of silicate, nitrate and suspended solids, which followed trends correlated to salinity, which, in turn, was related to the rainfall regime during the study period.

Native fishes in the Truckee River: Are in-stream structures and patterns of population genetic structure related?

In-stream structures are recognized as significant impediments to movement for freshwater fishes. Apex predators such as salmonids have been the focus of much research on the impacts of such barriers to population dynamics and population viability however much less research has focused on native fishes, where in-stream structures may have a greater impact on long term population viability of these smaller, less mobile species. Patterns of genetic structure on a riverscape can provide information on which structures represent real barriers to movement for fish species and under what specific flow conditions. Here we characterize the impact of 41 dam and diversion structures on movement dynamics under varying flow conditions for a suite of six native fishes found in the Truckee River of California and Nevada. Microsatellite loci were used to estimate total allelic diversity, effective population size and assess genetic population structure. Although there is spatial overlap among species within the river there are clear differences in species distributions within the watershed. Observed population genetic structure was associated with in-stream structures, but only under low flow conditions. High total discharge in 2006 allowed fish to move over potential barriers resulting in no observed population genetic structure for any species in 2007. The efficacy of in-stream structures to impede movement and isolate fish emerged only after multiple years of low flow conditions. Our results suggest that restricted movement of fish species, as a result of in-stream barriers, can be mitigated by flow management. However, as flow dynamics are likely to be altered under global climate change, fragmentation due to barriers could isolate stream fishes into small subpopulations susceptible to both demographic losses and losses of genetic variation.

A multistressor, multitrait approach to assessing the effects of wind and dust on Eucalyptus tereticornis

PREMISE OF THE STUDY

Plants are routinely subjected to multiple environmental stressors, and the ability to respond to these stressors determines species survival and ecological breadth. Despite stressors such as wind and dust significantly influencing plant development, morphology, and chemistry, the combined influence of these factors is yet to be investigated.

METHODS

We used a manipulative glasshouse approach to compare the morphological, physiological, and biomechanical responses of Eucalyptus tereticornis to the independent and combined effects of wind and dust.

KEY RESULTS

Wind decreased both E. tereticornis height and stem flexural stiffness. Additionally, wind had no effect on leaf physiology, nor did dust have any significant effect on any of the traits measured.

CONCLUSIONS

Our results suggest that wind and dust in combination may have an additive effect on several plant traits and provide new insight into the effects and importance of studying wind, dust, and different stress combinations.