Differences in biological traits composition of benthic assemblages between unimpacted habitats

Assessing the Impact of Anthropic Pressures on Aquatic Macroinvertebrates: A Functional Trait Approach in the Irtysh River Watershed

Little is known about how changes in the biodiversity and functional traits of macroinvertebrates in rivers respond to the responses of anthropic pressures and their driving factors. Macroinvertebrates were sampled at 17 sites in the Irtysh River Basin and classified macroinvertebrates into 10 traits and 38 categories between May and August 2022. Then, we performed R-mode linked to Q-mode (RLQ) analysis and calculated functional richness, evenness, divergence, and Rao's quadratic entropy (RaoQ) for each site and community-weighted means for each trait category. Our results indicated that there were pronounced alterations in species variability in the urban region. Functional divergence indicated fierce competition among species and considerable niche overlap in the urban region. Functional evenness indicated that species abundance distribution and interspecific functional distance were not uniform in the urban region. Functional richness indicated that the urban region was the strongest region in terms of niche occupation, resource utilization, and buffering capacity for environmental fluctuations. Rao's quadratic entropy showed that the trait difference of macroinvertebrates was the largest in all regions, which was caused by the gradient environmental difference. Research has revealed that urbanization significantly influences the evolutionary trajectory of macroinvertebrate fauna, culminating in an upsurge in pollution-tolerant species and a convergence of functional traits. We recommend strengthening the control of urban and industrial pollution and wise planning and management of land and water resources to mitigate the impact of anthropogenic destruction on habitat fragmentation in the Irtysh River Basin.

Potential marine benthic colonisers of offshore wind farms in the English channel: A functional trait-based approach

Offshore wind farms (OWFs) have gained attention as a promising alternative to conventional energy sources. However, their installation and operation may have multiple ecological impacts on the marine environment, including the "reef effect". The reef effect is the colonisation of wind turbines and other artificial substrates by benthic organisms, which has a major impact on marine biodiversity as it changes community assemblages and ecosystem functioning. We conducted a two-step study to predict the reef effect of a future OWF (Dunkirk, northern France). First, we explored similarities between colonisers of existing OWFs and those of other hard substrates (oil and gas platforms (O&GP) and hard substrates in the English Channel (HSEC)). We then analysed functional traits to determine a trait profile of potential colonisers of Dunkirk's OWF. Statistical analyses revealed that OWF and O&GP communities were more similar to each other than to that of HSEC. Comparing the three communities revealed that they shared 157 taxa, which could be potential colonisers of Dunkirk's future OWF. The functional profile revealed that OWF colonisers were species ranging from 10 to 100 mm in size, with gonochoric reproduction, pelagic and planktotrophic larvae, a life span of less than 2 years or 5-20 years, were sessile, and were carnivores or suspension feeders. Functional trait analysis revealed that during their intermediate stage of development, OWF benthic communities have a functional richness and diversity (0.68 and 0.53, respectively) similar to those of HSEC communities (0.54 and 0.50, respectively). However, based on using O&GP as a long-term view of the colonisation of OWFs, functional richness and diversity could decrease during the climax stage (0.07 and 0.42, respectively).

Benthic community resilience in two differently impacted tropical estuaries: Taxonomic vs functional approaches

Estuaries experience incessant modifications due to various stressors causing shifts in the benthic species community structure and ecosystem functioning. Two tropical estuaries along Northwest India, exposed to varied intensities of anthropogenic perturbations, were sampled seasonally for two consecutive years. Specific aims were to assess, compare and link the macroinvertebrate taxonomic and functional structures, to evaluate the resilience of estuarine benthic ecosystems by employing the multiple-trait approach and to identify major influencing environmental drivers for patterns discerned. Taxonomic and functional compositions in both the estuaries produced varied segregations along the estuarine zones, driven primarily by natural estuarine gradients like salinity and sediment grain size, despite extant anthropogenic stressors. Multiple traits contributed to the variance in benthic functioning. The Biological Trait Analysis (BTA) revealed that both the estuaries had similar trait compositions in the lower zones, while the middle and upper zones of each estuary presented different permutations of traits. The functional complexity at different estuarine sections was influenced by the variability in taxonomic composition and species dominance. However, relationships between Functional Diversity (FD) and species diversity were equivocal, signifying that taxonomic diversity may not be an efficient proxy for benthic functioning. As the zones had differential stressors and disturbance acts as a filter, discrete functional trait profiles of opportunistic traits were visualized along the potentially impacted zones. Thus, the less impacted lower zones had multiple traits, while the mid-upper zones that were subject to both anthropogenic and natural stressors had fewer traits. A more consistent functional structure, higher functional redundancy and substantial proportion of recolonisation traits (small-sized, short-lived, motile forms) suggested better resilience in one study estuary than the other one. Our study advocates that the inclusion of both taxonomical and functional metrics can provide in-depth inferences related to the macrobenthic community resilience and this coupled approach is imperative for effective future management programs.

Functional traits of polychaetes change between different types of Posidonia oceanica habitats

Meadows of Posidonia oceanica harbor rich biodiversity and ecosystem functions, yet Biological Traits Analysis on the resident benthic communities are lacking. This study aims to provide insight on the functional diversity of polychaetes communities, a dominant benthic group, between the different habitat types of P. oceanica (plain meadow, strips/patches and dead matte), as well as pilot indicators of habitat modification. The results showed how specific traits relate to the different habitat types. Plain meadow was different to strips/patches and dead matte in functional composition, diversity and thus, the ecosystem functions involved. However, an overlap was observed in functional composition between dead matte and living P. oceanica, due to the remaining matte structure. This highlights the importance of the former on ecosystem functioning and the serious consequences of its current exclusion from conservational legislation. In addition, the classification of species to ecosystem engineering types showed interesting potential as an indicator.

Linking Species Functional Traits to Specific Biogeochemical Processes under Trawling Pressure

Simple Summary

Bottom trawls when fishing move over large areas with different parts of the gears physically impacting the sea bottom, including the trawling wires, doors, ground rope and net. In this way, the trawl nets remove animals from bottom waters, the sediment surface and shallow sub-surface. The animals that live in the sea bottom with their activities and lifestyle play an important role in major ecosystem processes such as nutrient cycling. In this study, we investigated the relationship between species functional characteristics and ecosystem functions under trawling pressure. Our results indicated that under trawling, more opportunistic lifestyles and deposit feeders were associated with the ecosystem processes while in the undisturbed areas these processes were connected with bioturbating and burrowing species. Finding these links helps scientists and policy makers to better predict the impact of fishing disturbance on marine environment and set appropriate thresholds for marine ecosystem impacts.

Abstract

The impact of otter trawling on the relationship between functional traits of benthic invertebrates and specific biogeochemical processes were investigated in the oligotrophic Cretan Sea. The fishery is managed through a seasonal closure during the summer. During two seasons (winter and summer) replicate samples were taken from the field from a commercial trawl ground and an adjacent control area. Environmental parameters related to sediment biogeochemistry were measured including particulate organic carbon, sedimentary organic carbon, bottom water and sedimentary chlorophyll a and phaeopigment concentrations as well as benthic oxygen consumption. A significant impact of trawling was recorded only for bottom water chlorophyll and sedimentary organic carbon. Furthermore, the links between species traits and specific ecosystem processes were affected by trawling, highlighting the importance of unique functional modalities on ecosystem functioning. The traits that mostly influenced benthic biogeochemistry in the control sites were related to bioturbation and burrowing activities. In contrast, in the trawled sites, the associated traits were related to more opportunistic lifestyles and deposit feeding species that do not act as bioturbators. Thus, under trawling disturbance, this shift can decouple the species-sediment relations and affect nutrient cycling.

Biological traits of marine benthic invertebrates in Northwest Europe

Biological traits analysis (BTA) provides insight into causes and consequences of biodiversity change that cannot be achieved using traditional taxonomic approaches. However, acquiring information on biological traits (i.e., the behavioural, morphological, and reproductive characteristics of taxa) can be extremely time-consuming, especially for large community datasets, thus hindering the successful application of BTA. Here, we present information on ten key biological traits for over a thousand marine benthic invertebrate taxa surveyed in Northwest Europe (mainly the UK shelf). Scores of 0 to 3 are provided to indicate our confidence that taxa exhibit each possible mode of trait expression. The information was acquired over a decade through an extensive appraisal of relevant sources, including peer-reviewed papers, books, online material and, where necessary, professional judgement. These data may be inspected, used, and augmented by fellow researchers, thus assisting in the wider application of BTA in marine benthic ecology.

Measurement(s)	body size • body morphology • lifespan • egg development location • larva development location • living habit • sediment position • feeding mode • mobility • bioturbation mode
Technology Type(s)	literature review • professional judgement
Sample Characteristic - Organism	benthic invertebrates
Sample Characteristic - Environment	marine environment
Sample Characteristic - Location	Northwest Europe

Trawl impacts on the relative status of biotic communities of seabed sedimentary habitats in 24 regions worldwide

Bottom trawling is widespread globally and impacts seabed habitats. However, risks from trawling remain unquantified at large scales in most regions. We address these issues by synthesizing evidence on the impacts of different trawl-gear types, seabed recovery rates, and spatial distributions of trawling intensity in a quantitative indicator of biotic status (relative amount of pretrawling biota) for sedimentary habitats, where most bottom-trawling occurs, in 24 regions worldwide. Regional average status relative to an untrawled state (=1) was high (>0.9) in 15 regions, but <0.7 in three (European) regions and only 0.25 in the Adriatic Sea. Across all regions, 66% of seabed area was not trawled (status = 1), 1.5% was depleted (status = 0), and 93% had status > 0.8. These assessments are first order, based on parameters estimated with uncertainty from meta-analyses; we recommend regional analyses to refine parameters for local specificity. Nevertheless, our results are sufficiently robust to highlight regions needing more effective management to reduce exploitation and improve stock sustainability and seabed environmental status-while also showing seabed status was high (>0.95) in regions where catches of trawled fish stocks meet accepted benchmarks for sustainable exploitation, demonstrating that environmental benefits accrue from effective fisheries management. Furthermore, regional seabed status was related to the proportional area swept by trawling, enabling preliminary predictions of regional status when only the total amount of trawling is known. This research advances seascape-scale understanding of trawl impacts in regions around the world, enables quantitative assessment of sustainability risks, and facilitates implementation of an ecosystem approach to trawl fisheries management globally.

Taxonomic and functional diversity of benthic macrofauna associated with rhodolith beds in SE Brazil

Rhodoliths are free-living and morphologically diverse marine calcareous algae commonly distributed over the continental shelf seafloor. They increase the seabed structural complexity and are of potential value as feeding and reproductive grounds for a myriad of marine fauna. The higher structural seabed complexity within rhodolith beds may also increase benthic diversity by creating microhabitats, but this relationship has been rarely explored within rhodolith beds worldwide. Here we compared benthic macrofaunal (>500 µm) structure on rhodolith beds (nodule epifauna) and within unconsolidated sediments (sediment infauna) under high and low-density beds to test whether rhodolith bed density and nodule morphology influenced macrofaunal assemblages. We observed that macrofaunal density on nodules (2538 ± 288.7 ind·m-2) was 15-fold higher when compared to sediments under those beds (166 ± 38.8 ind·m-2). Rhodolith bed density was positively related to macrofaunal density, composition, and functional diversity on the rhodoliths. Low-density beds (61 ± 27.1 nodules·m-2) with discoid-shape nodules were dominated by peracarid crustaceans whereas high-density beds (204 ± 18.7 nodules·m-2) with spheroidal nodules were dominated by Annelid polychaetes. The sediment macrofauna was also positively influenced by the density of rhodolith nodules, which increased sediment carbonate and organic quality (protein and lipids) under high-density beds. Macrofaunal functional diversity was generally higher on rhodoliths, with low similarity (low nestedness) and high taxa turnover between macrofaunal assemblages of rhodoliths and sediments. These findings indicate that rhodolith beds provide an unique habitat for benthic macrofaunal communities, with exclusive functional and taxonomic richness that are likely not typical in the unconsolidated sediment below these beds in SE Brazil. This study highlights the importance of protecting rhodolith beds from multiple sources of anthropogenic disturbance and exploration on continental shelves.

Marine macrofaunal traits responses to dredged material disposal

Currently, our understanding of the mechanisms for, and potential functional implications of, changes in seabed assemblages resulting from dredged material disposal is relatively unknown. Based on empirical data from 17 disposal sites, we address this by quantifying the nature and magnitude of shifts in the relative composition of response and effects traits within disposal site assemblages relative to their reference assemblages. Differing shifts in both response and effects traits were observed across sites, regardless of the trait composition of the reference assemblages. Notable differences in the magnitude of traits changes were also observed for both trait types. Traits shifts are difficult to predict as they appear to reflect both environmental conditions and disposal regime. Temporal data revealed that some sites display relatively consistent responses while others presented large inter-annual variability. These findings are discussed in relation to dredged material monitoring and with respect to conservation objectives of marine protected areas.

Common patterns of functional and biotic indices in response to multiple stressors in marine harbours ecosystems

Evaluating the effects of anthropogenic pressure on the marine environment is one of the focal objectives in identifying strategies for its use, conservation and restoration. In this paper, we assessed the effects of chemical pollutants, grain size and plastic litter on functional traits, biodiversity and biotic indices. The study was conducted on the benthic communities of three harbours in the central Mediterranean Sea: Malta, Augusta and Syracuse, subjected to different levels of anthropogenic stress (high, medium and low, respectively). Six traits were considered, subdivided into 22 categories: reproductive frequency, environmental position, mobility, life habit, feeding habit and bioturbation. Functional diversity indices analysed were: Functional Divergence, Quadratic Entropy, Functional Evenness and Functional Richness. To assess the trait responses to environmental gradients, we applied RLQ analysis, which considers simultaneously the relationship between three components: environmental data (R), species abundances (L) and species traits (Q). From our analyses, significant relationships (P-value = 0.0018 for permutation of samples, and P-value = 0.00027 for permutation of species) between functional traits and environmental data were highlighted. The trait categories significantly influenced by environmental variables were those representing feeding habits and mobility. In particular, the first category was influenced by chemical pollutants (organotin compounds and polycyclic aromatic hydrocarbons) and grain size (silt and sand), while the latter category was influenced only by chemical pollutants. Pearson correlations performed for functional vs biotic and diversity indices confirmed the validity of the chosen conceptual framework for harbour environments. Finally, linear models assessing the influence of stressors on functional parameters underlined the link between environmental data vs benthic and functional indices. Our results highlight the fact that functional trait analysis provides a useful and fast method for detecting in greater depth the effects of multiple stressors on functional diversity in marine ecosystems.

Species interactions and environmental context affect intraspecific behavioural trait variation and ecosystem function

Functional trait-based approaches are increasingly adopted to understand and project ecological responses to environmental change; however, most assume trait expression is constant between conspecifics irrespective of context. Using two species of benthic invertebrate (brittlestars Amphiura filiformis and Amphiura chiajei), we demonstrate that trait expression at individual and community levels differs with biotic and abiotic context. We use PERMANOVA to test the effect of species identity, density and local environmental history on individual (righting and burrowing) and community (particle reworking and burrow ventilation) trait expression, as well as associated effects on ecosystem functioning (sediment nutrient release). Trait expression differs with context, with repercussions for the faunal mediation of ecosystem processes; we find increased rates of righting and burial behaviour and greater particle reworking with increasing density that are reflected in nutrient generation. However, the magnitude of effects differed within and between species, arising from site-specific environmental and morphological differences. Our results indicate that traits and processes influencing change in ecosystem functioning are products of both prevailing and historic conditions that cannot be constrained within typologies. Trait-based study must incorporate context-dependent variation, including intraspecific differences from individual to ecosystem scales, to avoid jeopardizing projections of ecosystem functioning and service delivery.

A multimetric approach to evaluate offshore mussel aquaculture effects on the taxonomical and functional diversity of macrobenthic communities

A multimetric approach was used to detect structural, compositional, and functional shifts in the underlying macrobenthic communities of an offshore mussel (Mytilus galloprovincialis) farm in a Portuguese Aquaculture Production Area. Sampling stations distributed inside and outside this area were used to evaluate sediment descriptors and macrobenthic samples collected before (April and September 2010) and after (June and September 2014) the initiation of mussel farming. Sediment fine fraction, organic matter content, and trace element concentrations were found to increase with depth, independently from the mussel farm. Moreover, the structure and composition of the macrobenthic communities were likewise structured by depth. Turnover was the dominant temporal and spatial pattern of beta diversity for all communities. Furthermore, the functional diversity of these communities was unaffected by the mussel farm. These results suggested that an offshore profile allowed hydrodynamic conditions to weaken the impact of mussel farming and highlighted the importance of conducting an integrative multimetric analysis when studying aquaculture impacts on benthic communities.

A spatial risk approach towards integrated marine spatial planning: A case study on European hake nursery areas in the North Alboran Sea

Europe's Blue Growth strategy promotes the intensification of human activities at sea and increases the environmental risk such as the decline of the provision of key ecosystem services and potential conflicts among human activities. The fishing sector, in the Alboran Sea, is economically and culturally one of the most important and relies on overexploited target species such as European hake (Merlucius merlucius). Here we identified and quantified the impact of human pressures on the capacity of marine habitats to support the provision of food as an important ecosystem service. We modelled the spatial distribution of nursery areas of European hake in the Alboran Sea, using General Additive Models (GAM) and overlaid those with European Nature Information System (EUNIS) habitats. A sensitivity analysis of hake nursery areas to cumulative human impacts identified the Bay of Malaga as the most sensitive area with trawling frequencies up to 60 times higher than the habitats recovery time. Further, we identified an increased conflict potential among human activities such as trawling and extraction with the presence of Marine Protected Areas (MPAs), which provide MPAs a high vulnerability similar to that found in unprotected areas. Future scenarios considering the increase of renewable energy and alternative food production show conflicts between aquaculture and MPAs as well as offshore wind farms and offshore shipping. Hence, our results show strong arguments for an integrated spatial management approach, including benthic trawling. We also suggest restricting trawling activities inside MPAs to safeguard the habitats capacity to support ecosystem services. Our spatially explicit assessment framework is transparent and transferable to other Mediterranean regions. Thus, it can function as a model on how to incorporate cumulative effect assessments in marine spatial planning processes.

Community bioirrigation potential (BIPc), an index to quantify the potential for solute exchange at the sediment-water interface

BIOIRRIGATION: the animal-induced exchange of solutes between pore water and overlying water - is a key process in sediments with profound implications for biogeochemical processes such as nutrient cycling and organic matter regeneration at the sediment water interface. There is an urgent need to understand how a changing environment will affect the irrigation activity of macrofauna and vice versa. A shift in species composition (e.g. from deep burrowing species to smaller, more opportunistic and shallow burrowing species) will have large effects on bioirrigation and thus on ecosystem function (such as benthic pelagic coupling). Considering the difficulties to determine area-covering rates of bioirrigation (e.g. in terms tracer-based fluxes) and the complexity of interactions of multiple species in the community that prohibit a direct measure of bioirrigation attributable to each species, a mechanistically-based approach is needed to predict relative intensities of bioirrigation activity based on the fundamental functional traits. We propose a conceptual framework to develop an index of bioirrigation that takes into account the biological mechanisms of bioirrigation and provides a simplified, yet functionally based approach to quantify the bioirrigation potential of benthic communities. We developed the community bioirrigation potential (BIP_c) that provides a biomass- and abundance-weighted scoring system considering functional traits related to pore water and solute exchange. It may be used as a supplement to established methods to assess the function of marine soft sediments related bioirrigation. In analogy to the particle-related community bioturbation potential of Solan et al. (2004), context dependent organismal traits that affect ventilation and bioirrigation (feeding type, morphology of burrows, and burrowing depth) are combined with the data on abundance and biomass of the respective species. These are subsequently summed up to a community bioirrigation potential (BIP_c). This review considers ecological traits relevant for bioirrigation and their classification into a bioirrigation index. Furthermore the necessary simplifications in the index (e.g. limiting its applicability to interfacial nutrient fluxes) are discussed. We also provide a working example from the southwestern Baltic Sea to illustrate the practical application of the index and a compilation of key species related to this area containing their classification into the considered bioirrigation traits.

Global analysis of depletion and recovery of seabed biota after bottom trawling disturbance

Bottom trawling is the most widespread human activity affecting seabed habitats. Here, we collate all available data for experimental and comparative studies of trawling impacts on whole communities of seabed macroinvertebrates on sedimentary habitats and develop widely applicable methods to estimate depletion and recovery rates of biota after trawling. Depletion of biota and trawl penetration into the seabed are highly correlated. Otter trawls caused the least depletion, removing 6% of biota per pass and penetrating the seabed on average down to 2.4 cm, whereas hydraulic dredges caused the most depletion, removing 41% of biota and penetrating the seabed on average 16.1 cm. Median recovery times posttrawling (from 50 to 95% of unimpacted biomass) ranged between 1.9 and 6.4 y. By accounting for the effects of penetration depth, environmental variation, and uncertainty, the models explained much of the variability of depletion and recovery estimates from single studies. Coupled with large-scale, high-resolution maps of trawling frequency and habitat, our estimates of depletion and recovery rates enable the assessment of trawling impacts on unprecedented spatial scales.