Response of intertidal sandy-beach macrofauna to human trampling: An urban vs. natural beach system approach

Do recreational activities affect macrofauna distribution pattern in Amazonian macrotidal sandy beaches?

Recreational activities are important source of disturbance on sandy beaches and have a negative effect on benthic communities as they alter species abundance, diversity, and/or distribution. Here, we report for the first time the effects of the recreational activities on the distribution pattern of macrobenthic communities of Amazonian sandy beaches. Sampling was performed during three consecutive months with different beach use intensity in 2017 (before, during vacation, and one month after the vacation period) on two contrasting beaches regarding disturbance (Urban: Atalaia; and Protected: Corvinas) in the intertidal zone along two equidistant transects at seven equidistant sampling stations: from the high-tide water mark to the swash zone. At each sampling station, four biological and sediment samples were randomly collected. Also, in each station, the sediment compaction was determined using a manual penetrometer. Physical sediment variables remained constant over time in both beaches, whereas differences were found in sediment compaction over the periods. Sediment compaction was considered the most important factor for the differences observed in macrobenthic community structure in the study beaches, and it was related to intensity of recreational activities. Variations in density and changes in richness between periods and sampling stations were observed in Atalaia beach. On the other hand, Corvinas beach remained the same throughout the study. Overall, three faunal zones were distinguished: upper intertidal, intermediate intertidal, and low-intertidal, whereas in the vacation period, only two faunal zones were distinguished: upper-intertidal and intermediate-low intertidal.

The efficacy of benthic indices to evaluate the ecological quality and urbanization effects on sandy beach ecosystems

Benthic indices have been widely used across different coastal ecosystems to assess ecological quality and detect anthropic impacts, but very few studies investigated their effectiveness on sandy beaches. Here, we evaluated and compared the efficacy of 12 assemblage-based benthic indices in assessing ecological quality in beaches, across a gradient of anthropic pressure and natural variability in 90 sandy beach sites. Overall, when sandy beaches were considered collectively, benthic indices had a poor performance in identifying decreases in ecological quality with increasing urbanization. However, when each morphodynamic type was evaluated separately, a few indices, especially those that were calibrated by reference conditions (i.e., M-AMBI, BAT, and BEQI-2), showed promising results for dissipative, and to a lesser extent, intermediate beaches. For reflective beaches, indices performed poorly, likely a reflection of the stronger natural disturbance these beaches are subjected to. Among functional indices, richness was found to be lower in urbanized beaches, but only in dissipative ones. Overall, our results show that benthic indices have the potential to be incorporated in sandy beach management and monitoring programs, especially for dissipative and intermediate beaches. For reflective beaches, given the early stage of studies with benthic indices in beaches, more research is needed to corroborate the observed patterns.

Evaluation of the effects of urbanization and environmental features on sandy beach macrobenthos highlights the importance of submerged zones

To assess how sandy beach biodiversity is influenced by the effects of environmental features and urbanization, we sampled the macrofauna in the whole across-shore gradient of 90 beach sites in Southeast Brazil. We found that morphodynamic features were the main drivers of macrobenthos, but urbanization-related variables, such as number of beachgoers and number of constructions on the upper shore, decreased species richness and biomass. We also found that submerged zones sustained the highest number of species and biomass in the across-shore gradient, but were the most impacted by human activities. By demonstrating the ecological importance of submerged zones, our results show that beach management practices, which are mainly focused on the upper shore, are missing important components of beach biodiversity. To secure the sustainability of beach ecosystems, management initiatives should include both their social and ecological components and consider the entire Littoral Active Zone as the proper management unit.

Assessing the benthic quality status of three fine sand tropical beaches from the Andaman Islands through the application of marine biotic indices

The rapid coastal development in the Andaman Islands has resulted in littoral habitat degradation. Understanding the performances of marine biotic indices and the interpretation and translation of those results into coastal health assessment could become an integral tool in future monitoring and management policies. In this line of efforts, the ecological quality status of three sandy beaches, two urban and one nonurban, was evaluated by using three marine biotic indices. The faunal community belonged to moderately well-sorted fine sand biocenosis. The relatively high species richness (15.9 ± 0.80 taxa sample^-1) and moderate abundance (563 ± 38.8 ind.m^-2) were features of the benthic fauna. The urban beaches (Aberdeen Bay and Carbyn's Cove) corresponded to tolerant benthic communities. Malacoceros indicus, Grandidierella megnae and Scolelepis squamata (tolerant species), and Ampelisca diadema (indifferent species) were the major constituents of urban beaches, while Scoloplos capensis, Urothoe grimaldii, and Urothoe platydactyla (sensitive species) were important at the nonurban beach (Wandoor). The high-good quality status prevailed across the spatial and temporal scales except for Carbyn's cove beach, where good-poor status was noticed. The M-AMBI appeared to be the most robust measure in distinguishing the impact between the urban and nonurban beaches. The constrained ordinations revealed a gradient of disturbance across the beaches. The distinct patterns of sample segregation were the result of the ecological response. This attempt should be considered a comprehensive measure of quality assessment of beaches under human pressure and draw a parallel line of evidence to global studies on sandy beaches.

Cumulative stressors impact macrofauna differentially according to sandy beach type: A meta-analysis

Many studies have demonstrated human impacts on sandy beach macroinvertebrates. However, little is known about causative drivers among multiple co-occurring stressors and how these interact with natural habitat conditions to yield specific faunal responses. We performed a global meta-analysis to shed light on how interactions between human disturbances and beach morphodynamics shape macroinvertebrate populations. We found that supralittoral forms (Talitridae and Ocypodidae) responded more negatively to the Human Modification Metric (a proxy for urbanization) on dissipative beaches, whereas intertidal organisms (Hippidae and Cirolanidae) showed more negative responses on non-dissipative beaches. Based on these findings we propose the Cumulative Harshness Hypothesis (CHH), which predicts higher sensitivity of beach macroinvertebrates to human disturbances when inhabiting a harsher physical environment according to their life histories. Secondly, we compared the response of macroinvertebrates to urbanization levels from local to larger scales (from 500 to 50000 m). Supralittoral families responded more negatively to local urbanization, which leads to habitat loss due to removal or reduction of upper beach zones. Conversely, intertidal organisms with planktonic larval stages were more affected by urbanization at the largest spatial scales, which we hypothesize disrupts metapopulation dynamics by impacting the supply of larvae that could colonize human-disturbed beaches. The differential effects of human disturbances on macroinvertebrates according to beach morphodynamics suggest that the efficiency of these ecological indicators for beach monitoring is context-dependent. Focusing on multiple stressors rather than on a single one is also critical to mitigate human impacts on these threatened ecosystems.

Recreational activities trigger changes in meiofauna and free-living nematodes on Amazonian macrotidal sandy beaches

Sandy beaches are key economic assets worldwide, however, recreational activities are an important source of disturbance in these ecosystems. Intensive human use of beaches has a negative effect on benthic communities as it alters species abundance, diversity, and/or distribution. Here, we report the impacts of recreational activities (trampling and vehicles) on meiobenthic communities and nematode assemblages on Amazonian sandy beaches for the first time. For this purpose, samples were carried out in four consecutive months encompassing a period of high visitation peak (one month Before Vacation, During Vacation, and two months After Vacation) on three contrasting beaches regarding disturbances (Urban: Atalaia; Intermediary: Farol-Velho; and Protected: Corvinas) at seven equidistant sampling stations (50 m apart) from the high tide water mark to the swash zone. At each sampling station, three biological samples and sediments samples were collected haphazardly. Also, in each station, the sediment compaction was determined using a manual penetrometer. Overall, physical sediment variables (grain size, sorting) were constant over time in all beaches, whereas differences in intensity of recreational activities and sediment compaction were found between beaches and months. Sediment compaction was considered the most important factor for the differences observed in meiofauna community structure in the study areas, and it was related to intensity of recreational activities. Variations in density and changes in richness between periods were observed in Atalaia and Farol-Velho beaches. On the other hand, Corvinas beach remained the same throughout the study. In the first month after vacation, density and richness were similar to those in the period before vacation, thus indicating that the beaches had recovered in one month. Furthermore, vulnerabilities of Tardigrada and Copepoda, as well as of the Nematoda genera Daptonema, and Chromadorita, indicate that they might be potential indicators of recreational activities.

How do red deer react to increased visitor numbers? A case study on human-deer encounter probability and its effect on cortisol stress responses

The numbers of visitors to greenspaces in the United Kingdom has increased over the last few years as the health benefits of spending time in greenspaces have become better known. This has led to problems for conservation ecologists due to increased numbers of reported human-wildlife encounters. Deer are often found in public spaces and are of particular concern. Previous research suggests elevated levels of stress hormones (e.g., cortisol) in deer is a result of increased human activity. This has been linked to several negative effects on the deer’s health. From a practitioner’s point of view, it is therefore important to implement effective management strategies that are based on scientific evidence to help ensure the welfare of managed deer populations. In an effort to identify the impact of visitor numbers on faecal cortisol concentrations, samples from 2 red deer (Cervus elaphus) herds in Lyme Park (Cheshire), United Kingdom, were collected and analysed. A predictive spatial model was developed based on logistic regression to identify areas within the park of low and high human-deer encounter probability. The faecal cortisol levels were found to be significantly higher on days with a high number of visitors. In addition, landscape features such as buildings and roads increased the probability of human-deer encounters, whereas woodland and scrub decreased the probability. However, human-deer encounter probability changed with distance to the features. By providing local park managers with this scientific data, these findings can directly inform current management efforts to reduce deer stress levels in Lyme Park. In addition, the spatial modelling method has the capacity to be implemented in other parks across the country with minimal cost and effort.

Main Anthropogenic Impacts on Benthic Macrofauna of Sandy Beaches: A Review

Sandy beaches provide several ecosystem services such as coastal protection and resilience, water filtration and nutrient mineralization. Beaches also represent a hub for social, cultural and economic relationships as well as educational activities. Increasing urbanization, recreational activities and mechanical beach cleaning represent major anthropogenic disturbances on sandy beaches leading to loss of biodiversity as well as good and services. Information about the impacts of anthropogenic pressures on benthic macrofaunal communities could be useful to assess the environmental status of sandy beaches and to promote a sustainable use of beach ecosystem. Here, scientific articles about three major anthropogenic impacts on sandy beach macrofauna were reviewed to provide the state of knowledge about these impacts, to highlight gaps, to supply considerations about the methodologies and the used indicators and to give insights for future studies. The stressors considered in our review are: 1) trampling, 2) breakwater barriers, 3) mechanical beach cleaning. This review underlined that there are few studies regarding individual human disturbances on sandy beach macrofauna and specifically, there is a lack of sufficient indicator species for the assessment of such stressors. Similarly, the researches have covered specific regions, highlighting the need for such studies in other parts of the world. In particular, the impacts of breakwater barriers on surrounding communities has been found to be given less attention in the literature and there is enough that could be explored.

Human access impacts biodiversity of microscopic animals in sandy beaches

Whereas most work to understand impacts of humans on biodiversity on coastal areas has focused on large, conspicuous organisms, we highlight effects of tourist access on the diversity of microscopic marine animals (meiofauna). We used a DNA metabarcoding approach with an iterative and phylogeny-based approach for the taxonomic assignment of meiofauna and relate diversity patterns to the numbers of tourists accessing sandy beaches on an otherwise un-impacted island National Park. Tourist frequentation, independently of differences in sediment granulometry, beach length, and other potential confounding factors, affected meiofaunal diversity in the shallow “swash” zone right at the mean water mark; the impacts declined with water depth (up to 2 m). The indicated negative effect on meiofauna may have a consequence on all the biota including the higher trophic levels. Thus, we claim that it is important to consider restricting access to beaches in touristic areas, in order to preserve biodiversity.

Martínez et al. use DNA metabarcoding and a phylogeny-based approach to demonstrate the effects of tourist access on meiofauna diversity of beaches in Asinara National Park. Their results show that tourist frequentation decreases meiofaunal diversity at the shallow “swash” zone, and can be used to inform tourist access and management of beaches.

Functional responses of intertidal bivalves to repeated sub-lethal, physical disturbances

In coastal habitats, physical disturbances of benthic organisms can be caused by natural events like wave-born objects and human activity like trampling, and these disturbances can be sub-lethal (e.g., resulting in the organism's displacement). We know little of how sessile organisms respond to physical disturbances such as displacements. Using Mytilaster minimus, a mussel that is native to the Mediterranean Sea, we tested how byssus production and oxygen uptake rates changed in response to different frequencies of disturbance events (10-60 events h^-1). Mussels increased oxygen uptake rates but not byssus production with increasing disturbance frequencies (50-60 events h^-1). Our results show that sub-lethal, physical disturbances can cause increased physiological rates in mussels if disturbances repeat rapidly. Therefore, sub-lethal, physical disturbances can have negative consequences for benthic organisms even if they do not cause immediate damage or mortality.

To clean or not to clean? A critical review of beach cleaning methods and impacts

Cleaning is a fundamental concern of beach managers in many destinations as well as an important requirement in beach quality awards. However, it has been largely neglected in the literature. This paper provides an overview of empirical studies on beach cleaning and analyzes cleaning-related requirements of 11 beach awards that generate controversy in the literature. This study comments on key aspects of beach cleaning, resolves various misconceptions, and provides new perspectives by integrating related topics drawn from a wide range of literature. The arguments based on both the ecological and tourism managerial perspectives are presented, indicating the gaps and proposing research solutions. The paper calls for empirical studies with regard to the efficiency of different cleaning approaches on beaches with varying levels of use intensity and for methodological designs that separate the impacts of mechanical grooming from those of trampling, dune destruction, shore armoring, artificial lighting, among others.

Infralittoral-sublittoral (submerged zone) macroinfauna community structure of high-impact, medium-impact and non-impact beaches on the Gulf of Cádiz coast (SW Spain). Evaluation of anthropogenic alterations: Nourishments, human impact and urbanization

Beaches are dynamic transitional environments subject to numerous natural and anthropic alterations. In these ecosystems, the infralittoral-sublittoral macrofauna communities play a key role in the food web. The objective of this study was to compare macrofauna communities on six beaches on the Gulf of Cádiz coast, which were classified according to the anthropic alterations they support, and evaluate the influence of abiotic factors on the species distribution. Sampling was done in the infralittoral-sublittoral zone of each beach using a modified manual dredge. Five perpendicular transects of 25 m, each separated by 10 m, were performed per beach, with a total sample area of 43.75 m² per beach. A total of 27 species were found, of which Donax trunculus, Diogenes pugilator, and Tritia grana were the most abundant. Anthropogenic effects are appreciable in the infralittoral-sublittoral although they are areas that are permanently submerged and less exposed than the intertidal. Beach nourishments carried out with large volumes of sand can alter the grain size, the most influential parameter on the distribution of the species, and consequently, affect the macrofauna community that inhabits these beaches.

Heavy metal contamination in sandy beach macrofauna communities from the Rio de Janeiro coast, Southeastern Brazil

We evaluated concentrations of eight heavy metals Cr, Zn, Pb, Ni, Cu, Cd, Co and V, in tissues of representative macrofauna species from 68 sandy beaches from the coast of Rio de Janeiro state. The links between contamination levels and community descriptors such as diversity, evenness, density and biomass, were also investigated. Metal concentrations from macrofaunal tissues were compared to maximum permissible limits for human ingestion stipulated by the Brazilian regulatory agency (ANVISA). Generalized linear models (GLM's) were used to investigate the variability in macrofauna density, richness, eveness and biomass in the seven different regions. A non-metric multidimensional scaling analysis (n-MDS) was used to investigate the spatial pattern of heavy metal concentrations along the seven regions of Rio de Janeiro coast. Variation partitioning was applied to evaluate the variance in the community assemblage explained by the environmental variables and the heavy metal concentrations. Our data suggested high spatial variation in the concentration of heavy metals in macrofauna species from the beaches of Rio de Janeiro. This result highlighted a diffuse source of contamination along the coast. Most of the metals concentrations were under the limits established by ANVISA. The variability in community descriptors was related to morphodynamic variables, but not with metal contamination values, indicating the lack of direct relationships at the community level. Concentration levels of eight heavy metals in macrofauna species from 68 sandy beaches on Rio de Janeiro coast (Brazil) were spatially correlated with anthropogenic activities such as industrialization and urbanization.

The Early Shorebird Will Catch Fewer Invertebrates on Trampled Sandy Beaches

Many species of birds breeding on ocean beaches and in coastal dunes are of global conservation concern. Most of these species rely on invertebrates (e.g. insects, small crustaceans) as an irreplaceable food source, foraging primarily around the strandline on the upper beach near the dunes. Sandy beaches are also prime sites for human recreation, which impacts these food resources via negative trampling effects. We quantified acute trampling impacts on assemblages of upper shore invertebrates in a controlled experiment over a range of foot traffic intensities (up to 56 steps per square metre) on a temperate beach in Victoria, Australia. Trampling significantly altered assemblage structure (species composition and density) and was correlated with significant declines in invertebrate abundance and species richness. Trampling effects were strongest for rare species. In heavily trafficked plots the abundance of sand hoppers (Amphipoda), a principal prey item of threatened Hooded Plovers breeding on this beach, was halved. In contrast to the consistently strong effects of trampling, natural habitat attributes (e.g. sediment grain size, compactness) were much less influential predictors. If acute suppression of invertebrates caused by trampling, as demonstrated here, is more widespread on beaches it may constitute a significant threat to endangered vertebrates reliant on these invertebrates. This calls for a re-thinking of conservation actions by considering active management of food resources, possibly through enhancement of wrack or direct augmentation of prey items to breeding territories.

Responses of ghost crabs to habitat modification of urban sandy beaches

Sandy beaches in highly urbanised areas are subject to a wide range of human impacts. Ghost crabs are a commonly used ecological indicator on sandy beaches, as they are key consumers in these systems and counting burrow openings allows for rapid assessment of population size. This study assessed the pressures of urbanisation on sandy beaches in the highly urbanised estuary of Sydney Harbour. Across 38 beaches, we examined which physical beach properties, management practices and human induced habitat modification best predicted ghost crab distributions. Of all variables measured, the frequency of mechanical beach cleaning was the most important predictor of crab abundance, with low burrow densities at the highest cleaning frequency and the highest densities at beaches cleaned at the intermediate frequency (≤3 times per week). These results indicate that ghost crab populations in Sydney Harbour are more robust to the impacts of urbanisation than previously thought.