Beach Ecosystems Research Articles

Economic contribution of beach resources and their sustainable development in China

Beach ecosystem provides services that produce substantial economic value. Different functions of beach resources (recreation and tourism, amenity, coastal protection, biodiversity, etc.) perform inherently different characteristics and contribute diversely to human welfare and fortune. Yet, there have been rare quantification estimations for economic contributions of beaches to human life. Here, framework of beach ecosystem services based on key functions is established, then a series of integrated quantification methods are summarized by published literature and a few novel estimations. Economic contributions of beach resources are obtained through application in fifty-nine coastal cities of China in recent ten years. Spatial added values in real estate benefiting from beaches are separated out economically for the first time. In China, beach resources of 3100 km generate an economic value of at least ¥4.00 × 1012 ($579.60 × 109) during the time interval 2010–2019. Furthermore, legislation, international tourism competitiveness, beach nourishment and restoration issues are discussed; dynamic pattern and healthy-recycled beach economy are creatively proposed according to the needs of sustainable development. This study explores the interface between ecosystem services and economics for beach resources, provides straight recognition upon beaches' economic contribution (least estimation), and promotes understanding of social and natural impacts on China's beach economy.

Uptake of polycyclic aromatic hydrocarbons via high-energy water accommodated fraction (HEWAF) by beach hoppers (Amphipoda, Talitridae) using different sandy beach exposure pathways

Sandy beach ecosystems are highly dynamic coastal environments subject to a variety of anthropogenic pressures and impacts. Pollution from oil spills can damage beach ecosystems through the toxic effects of hydrocarbons on organisms and the disruptive nature of large-scale clean-up practices. On temperate sandy beaches, intertidal talitrid amphipods are primary consumers of macrophyte wrack subsidies and serve as prey for higher trophic level consumers, such as birds and fish. These integral organisms of the beach food web can be exposed to hydrocarbons by direct contact with oiled sand through burrowing and by the consumption of oiled wrack. We experimentally evaluated the primary polycyclic aromatic hydrocarbon (PAH) exposure pathway via high-energy water accommodated fraction (HEWAF) for a species of talitrid amphipod (Megalorchestia pugettensis). Our results indicated that tissue PAH concentrations in talitrids were six-fold higher in treatments that included oiled sand compared to those with only oiled kelp and the controls.

Modeling approach for coastal dune habitat detection on coastal ecosystems combining very high‐resolution UAV imagery and field survey

AbstractEarth observation (EO) data, derived from remote sensing and unmanned aerial vehicle (UAV), have been recently demonstrated to be essential tools for the ecosystem monitoring and habitat mapping, combining high technological and methodological procedures for applied ecology. However, research based on EO data analyses often tend to focus on image processing techniques, neglecting the development of a detailed sampling design scheme needed for an exhaustive habitat detection. This paper shows the results of a novel approach for mapping coastal dune habitats at a fine scale, using a supervised machine learning model, through the combination of vegetation plot sampling scheme, synergic use of multi‐sensor spectral imagery (UAV‐VHR) and environmental predictors (e.g., LiDAR), object‐based image analysis, and landscape metrics analysis. Proposed approach was tested in a protected area, established to preserve notable habitats along the Italian Tyrrhenian coast. A detailed sampling scheme was designed and carried out during spring and summer of 2019, combining simultaneously UAV flight acquisition and field vegetation survey data, collected at high precision positioning. The calibrated classification model achieved an overall accuracy of 78.6% (standard error 4.33), allowing us to accurately classify and map five coastal habitats, according to EUNIS (European Nature Information System) classification, which were further verified through a fully independent validation field survey. Results demonstrate that VHR imageries, combined with specific field survey schemes, can be exploited to train classification models used for the detection of plant communities (i.e., meso‐habitat) and plant species at local scale. Our findings demonstrate that UAV‐VHR data is a valid tool to produce high spatial resolution information in sand beach ecosystems, giving ecology research a new way for responsive, timely, and cost‐effective ecosystem monitoring.

The effect of water level rise on coastal wave Overwash and Inundation of dunes in laboratory

Beach responses to sea level rise are investigated experimentally in laboratory wave flume by detecting the beach profile continuously using video cameras in high space and time resolution. Experiments are conducted to discuss the profile response in three scenarios of water level rise: a step-change in water level, continuous water level rise as well as extremely high water levels to find out the intensification and dissipation of swash motion waves in overwash and inundation hydrodynamic and the retreat of the shoreline due to water level rise. The sediment transport rates are estimated from the detailed monitoring of the beach profiles, from which the responses of the shoreline to the water level rise are examined.The morphological characteristics of the dunes caused by sea-level rise are discussed and it is noted that sea-level rise leads to an increase of more than 40% in sediment loss from sand dunes, while extreme solitary wave conditions are less affected by water level changes. The characteristics of shoreline retreat for different sea levels and wave conditions are analyzed from the experiment data. The developments of shoreline and beach response prediction model using the laboratory experiment data to the sea level rise are discussed for better estimation of the shoreline change to the sea level rise. Meanwhile, the trend of wave energy is consistent with the frequency of profile change as the water level continues to rise. When the water level is high enough close to the dune crest, partially broken waves in nearshore areas transmitted landward with large wave energy quickly destroy the dunes, which is a great threat to the beach ecosystem. There is an inhibitory effect on the morphological changes of the dunes as the water level is high in the back of the dunes.

Local scale high frequency monitoring of seaweed strandings along an intertidal shore of the English Channel (Luc-sur-Mer, Normandy France) – Effect of biotic and abiotic factors

Seaweed strandings on Luc-sur-Mer beach (Bay of Seine, English Channel, France) were monitored from March 2017 to October 2018 once or twice a week to investigate the wrack deposit dynamics linked to biotic and environmental parameters. The extent of stranded seaweed, algal biomass and composition of algal wrack were monitored through 99 field surveys. Forty-seven macroalgae taxa (14 Phaeophyta, 28 Rhodophyta, and 5 Chlorophyta) were identified in strandings. Almost 83% of the 35 taxa (8 Phaeophyta, 23 Rhodophyta, and 4 Chlorophyta) inventoried on the nearby intertidal rocky shore during the same period were also identified in the wrack deposits, suggesting their local origin. Analysis of wrack composition revealed the dominance of sheet-like species and annual algae mainly represented by Ulva in spring and summer, and by perennial and brown seaweeds in winter. The same stranding dynamics was observed in the two years with largest deposits in spring and summer but strandings occurred earlier in 2017, due to contrasted environmental parameters in the two years. Large wrack deposits (> 4.5 Ha) were mainly observed in spring when the wind speed was greater than 2.6 m.s−1 and the predicted tide height greater than 6.8 m. Most deposits were associated with WSW winds (38%) and SSW winds (26%) winds. These data will help develop a tool to assess the risk of algal bloom in sandy beach ecosystem. The knowledge acquired about the availability and composition of the macroalgae strandings will also help promote the use of this bio-resource which is under-exploited in Normandy.

Tri Hita Karana Perspective in Waste Disposal from a Seaweed Processing Factory Eucheuma cottonii at Jumpai Beach, Bali

The name Tri Hita Karana comes from Sanskrit: Tri means three, Hita means happiness/prosperity, and Karana means cause. Seaweed is one of the abundant natural resources of Indonesia. In the processing which can significantly affect the quality of the final product obtained. The results of this research observed effluent waste was observed to be discharged freely from a pipe exiting the rear factory wall directly onto the beach, or into the sea at high tide. This material was collected and analysed. The processing of seaweed (Eucheuma cottonii) in this factory uses ≥90% Potassium hydroxide (KOH) as a raw material (as evidenced by the numerous empty sacks of KOH 90% strewn around the site, as well as direct reports from workers). This concentrated KOH is highly hazardous and is used to boil the seaweed with water. The average of a continuous concentration in different time (three hours) of K+ detected were 1000 ppm or 1% and 939 ppm or 0.939%, while the concentration of other elements detected was Cl with an average of a continuous concentration in different time (three hours) were 759.3 ppm or 0.759% and 581 ppm or 0.581%. This indicates that this factory waste contains KOH and has the potential to pollute the environment, especially sea water and the adjacent beach ecosystem. The results showed that the pH of the waste-water was 10.34 and 9.25. This indicates an alkaline pH almost certainly due to factory processing with KOH in the factory, exceeding the ideal pH value for sea water. A high concentration of KOH will cause the pH of the waste-water to shift towards alkaline and kill marine life and poison the beach ecosystem. This is worrying as the area supports a rural population who depend on fishing for much of their livelihood. The researcher concluded that the waste-water contains KOH and has highly potential to pollute the environment, especially sea water and it has not in accordance with the Balinese people, especially the Palemahan and this study indicate that the waste management process at the Jumpai Beach has not fully implemented the Laws and Regulations concerning waste management.

Short-term tourism alters abundance, size, and composition of microplastics on sandy beaches

Microplastics have become a global threat to sandy beach ecosystems. To efficiently manage this threat, potential sources of microplastics should be deeply understood, which requires direct evidence as this is always a challenging task. Previous studies have reported various sources; however, the topic still needs attention to identify other potential sources of microplastics on sandy shores. Therefore, the abundance, size, color, shape, and polymer type of microplastics on nine sandy shores of the Turkish Coast of the Black Sea were examined before and after the regular tourism season to understand whether short-term tourism might be an important source. A total of 3402 microplastic items from 270 sand samples were obtained and examined. Both the abundance and the average size of the microplastics increased after the tourism season associated with the potential number of visitors and beach cleaning efforts. Further, the color, shape, and polymer type of microplastics varied between sampling times. Beach cleaning seemed to be an efficient way to minimize the adverse effect of short-term tourism influence. This study clearly identifies short-term tourism as an important source of microplastics on sandy shores and beach cleaning as an important tool to minimize microplastic abundance. The results of this study are important insights into current literature by identifying another source of microplastics on sandy shores, which should be useful for the potential management actions to reduce the harm of these global pollutants.

Effects of natural and anthropogenic storm-stranded debris in upper-beach arthropods: Is wrack a prey hotspot for birds?

Storm-stranded debris (i.e., wrack) are important components for the functioning of beach ecosystems. With the current increase in extreme storm events, beached wrack is expected to change globally. However, little is known about how different types of wrack can affect beach biodiversity. Here, we hypothesized that natural debris (algae and land–plant debris) would optimize the short-term aggregation of benthic arthropods on the beach ecosystem, while anthropogenic debris (plastics) would not perform this function. We also expected that short-term aggregations of arthropods in the natural debris would create a transient prey hotspot (i.e., points of high prey concentration) for birds on the beach. Thus, we performed manipulative field experiments with debris addition and predator exclusion by cage on a short temporal scale (maximum 20 days). We found that natural debris aggregated higher community abundances than anthropic debris and treatments without debris, while community richness was not affected by wrack. No differences were noted when comparing the community aggregation on plastic debris and treatments without debris. The coleopterans were the group responsible for this aggregation, mainly represented by Phaleria testacea, which aggregated on natural debris with abundances five times greater than those on plastic debris. Nevertheless, we did not find any evidence of increased predation by birds on the coleopterans aggregated in the natural debris. We conclude that arthropod aggregation in the wrack is a phenomenon primarily associated with natural debris, not occurring in plastic debris, although the role of this faunal aggregation as a prey hotspot for birds was not evident in the short term. These results showed that the wrack type matters in terms of consequences for beach arthropods, creating concerns against beach cleaning methods that are adopted indiscriminately, also signaling the need for long-term studies to proceed with investigating the wrack functions for top predators on sandy beaches.

Effects of beach wrack on the fate of mercury at the land-sea interface – A preliminary study

Since the 1970s, the amount of aquatic plants and algae debris, called beach wrack (BW), has increased along the shores of industrialised regions. The strong ability of primary producers to accumulate pollutants can potentially result in their deposition on the beach along with the BW. Despite that, the fate and impact of such pollutants on sandy beach ecosystems have not been investigated so far. This study examines the fate of neurotoxic mercury and its labile and stable fractions in BW on sandy beaches of the Puck Bay (Baltic Sea). In addition to BW, beach sediments and wrack-associated macrofauna were also analysed. Rough estimations showed that Puck Bay beaches (58.8 km) may be a temporary storage of 0.2–0.5 kg of mercury, deposited on them along with the BW annually. A large proportion of Hg (89 ± 16%) in a BW was labile and potentially bioavailable. The contribution of Hg fractions in the BW was conditioned by the degree of its decomposition (molar C:N:P ratio). With the progressive degradation of BW, a decrease in the contribution of Hg adsorbed on its surface with a simultaneous increase in the proportion of adsorbed (intracellular), mercury was observed. BW accumulation decreased oxygen content and redox potential and increased methylmercury content in underlying sediments, indicating methylation. Hg concentrations in the studied fauna were up to 4 times higher than in the BW. The highest values occurred in a predatory sand bear spider and the lowest in a herbivorous sand hopper. Regardless of trophic position, most of Hg (92–95%) occurred as an absorbed fraction, which indicates about a 30% increase in relation to its share of BW. These findings suggest the significant role of BW as a mercury carrier in a land-sea interface and increased exposure of beach communities to the adverse effects of mercury in coastal ecosystems.

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.

Seasonal changes in beach resilience along an urbanized barrier island

Beach width, dune height, and vegetation coverage are key parameters to assess beach resistance and resilience to storms. However, coastal development often causes beach ecosystem degradation due to poor coastal management. We propose a Coastal Resilience Index from Remote Sensors (CRIfRS) for urbanized coasts based on aerial photogrammetry. The study area, located along a 7.8 km stretch of coast on a barrier island, is characterized by persistent alongshore sediment transport and the presence of coastal structures and beach-front houses. Contrary to previous studies, we focus on anthropogenic perturbations (coastal urbanization and coastal structures), instead of hydrodynamic conditions (storms), since erosion in this region is mainly associated with alongshore sediment transport gradients induced by coastal structures. Thus, the CRIfRS is based on the relation of three indicators that affect the beach functionality for coastal protection: beach width, coastal structure influence area, and vegetation coverage. The CRIfRS was divided into five categories: Very Low resilience (VL), Low resilience (L), Medium resilience (M), High resilience (H), and Very High resilience (VH). The CRIfRS presented an important spatial and temporal variability due to changing environmental conditions and the deployment of new coastal structures. For the study period, the percentage of the coast within the VL and L resilience classification increased, whereas the percentage of the coast classified as M, H, and VH resilience decreased. During the winter storm season, the resilience increased mainly due to the cross-shore transport whilst during mean wave conditions (i.e., sea-breeze conditions) the long-shore transport becomes more persistent and thus the coastal structures play an important role interrupting the sediment flux. Additionally, the CRIfRS trajectory shows an overall increase of the L resilience and an overall decrease of the H resilience values. This study highlights the important role of anthropogenic perturbations on the assessment of coastal resilience for highly urbanized coasts. The CRIfRS can help to improve the coastal management by assessing the coastal protection capability of beaches considering both natural and anthropogenic factors.

Storm accelerated subsurface Escherichia coli growth and exports to coastal waters

Storm significantly deteriorates coastal water fecal pollution now and beyond. Questions relating to storm exerting on coastal water safety are often intertwined with both surface water and subsurface processes. Stormwater runoff is a vital metric for coastal water fecal pollution under current cognition, while the controls of subsurface system remain unclear. Here, this study leveraged two time-series field data collected in a sandy beach during storm and non-storm periods to probe subsurface Escherichia coli (E. coli) growth and exports to coastal waters under storm events. Results demonstrated that storm events can not only stimulate subsurface E. coli growth, but also accelerate subsurface E. coli exports into the receiving water. Storm-intensified rainfall injected more oxygenous rainwater in the shallow groundwater, subsequently stimulating subsurface E. coli growth. Storm-strengthened wave energy was responsible for accelerating subsurface E. coli exports through enhanced wave-induced recirculated seawater. This study proposes a new insight for the stress of storm events on microbial pollution in coastal waters. The findings are constructive to the prevention of beach ecosystem pollution and can pave the way for coastal safety management to future extreme weather.

Dogs suppress a pivotal function in the food webs of sandy beaches

Domestic dogs are the most abundant carnivore globally and have demonstrable negative impacts to wildlife; yet, little evidence regarding their functional roles in natural food webs exists. Adding dogs to food webs may result in a net loss (via suppression of naturally occurring species), net gain (via mesopredator release), or no change (via functional replacement) to ecosystem function. Scavenging is a pivotal function in ecosystems, particularly those that are energetically supported by carrion. Dogs also scavenge on animal carcasses, but whether scavenging by dogs influences the structural and functional properties of food webs remains unclear. Here we used camera traps baited with carrion to test the effect of dogs on the composition and diversity of the vertebrate scavenger guild, as well as carrion detection and consumption rates. We conducted this work in sandy beach ecosystems, which rely on the import of marine organic matter (i.e. stranding of dead marine animals). Diversity of the scavenger community was similar on beaches without dogs. Dogs increased the time it took for carcasses to be detected and decreased the proportion of carrion consumed. This ‘dog suppression effect’ on scavenging was stronger for nocturnal mammalian scavengers, presumably being driven by indirect trait-mediated effects, which raises further questions about the broader ecological consequences of domestic dogs in natural systems.

The role of inputs of marine wrack and carrion in sandy-beach ecosystems: a global review.

Sandy beaches are iconic interfaces that functionally link the ocean with the land via the flow of organic matter from the sea. These cross-ecosystem fluxes often comprise uprooted seagrass and dislodged macroalgae that can form substantial accumulations of detritus, termed 'wrack', on sandy beaches. In addition, the tissue of the carcasses of marine animals that regularly wash up on beaches form a rich food source ('carrion') for a diversity of scavenging animals. Here, we provide a global review of how wrack and carrion provide spatial subsidies that shape the structure and functioning of sandy-beach ecosystems (sandy beaches and adjacent surf zones), which typically have little in situ primary production. We also examine the spatial scaling of the influence of these processes across the broader land- and seascape, and identify key gaps in our knowledge to guide future research directions and priorities. Large quantities of detrital kelp and seagrass can flow into sandy-beach ecosystems, where microbial decomposers and animals process it. The rates of wrack supply and its retention are influenced by the oceanographic processes that transport it, the geomorphology and landscape context of the recipient beaches, and the condition, life history and morphological characteristics of the macrophyte taxa that are the ultimate source of wrack. When retained in beach ecosystems, wrack often creates hotspots of microbial metabolism, secondary productivity, biodiversity, and nutrient remineralization. Nutrients are produced during wrack breakdown, and these can return to coastal waters in surface flows (swash) and aquifers discharging into the subtidal surf. Beach-cast kelp often plays a key trophic role, being an abundant and preferred food source for mobile, semi-aquatic invertebrates that channel imported algal matter to predatory invertebrates, fish, and birds. The role of beach-cast marine carrion is likely to be underestimated, as it can be consumed rapidly by highly mobile scavengers (e.g. foxes, coyotes, raptors, vultures). These consumers become important vectors in transferring marine productivity inland, thereby linking marine and terrestrial ecosystems. Whilst deposits of organic matter on sandy-beach ecosystems underpin a range of ecosystem functions and services, they can be at variance with aesthetic perceptions resulting in widespread activities, such as 'beach cleaning and grooming'. This practice diminishes the energetic base of food webs, intertidal fauna, and biodiversity. Global declines in seagrass beds and kelp forests (linked to global warming) are predicted to cause substantial reductions in the amounts of marine organic matter reaching many beach ecosystems, likely causing flow-on effects for food webs and biodiversity. Similarly, future sea-level rise and increased storm frequency are likely to alter profoundly the physical attributes of beaches, which in turn can change the rates at which beaches retain and process the influxes of wrack and animal carcasses. Conservation of the multi-faceted ecosystem services that sandy beaches provide will increasingly need to encompass a greater societal appreciation and the safeguarding of ecological functions reliant on beach-cast organic matter on innumerable ocean shores worldwide.

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.

Large Wood Debris Contributes to Beach Ecosystems but Colombian Beachgoer’s Do Not Recognize It

Large Woody Debris (LWD) accumulation serves essential ecological functions and benefits society’s coastal ecosystems (e.g., beaches). Thus far, the ecosystem services perspective has paid little attention to LWD. Therefore, we aim to contrast social perceptions on LWD and its ecological significance in Puerto Velero beach, Caribbean, Colombia. In consequence, the contribution of LWD to the conformation and creation of Puerto Velero beach was analyzed, as well as how beachgoers perceive the importance of LWD and if they were willing to pay to remove LWD in this beach. To achieve this, a quantitative convergent approach was then proposed using GIS analysis and remote sensing to understand the contributions of LWD to the Puerto Velero beach ecosystem; and in addition, a survey was performed to determine how beachgoers perceived LWD and how they valued the phenomenon. Results indicate that LWD contributed to beach maintenance; nevertheless, most people neglected LWD values because of its lack of visual attractiveness. As such, ecosystem services targets become conflicted because people positively perceived ecosystem services provided by beaches, but they did not assign importance to the beach dynamics they deemed unattractive, regardless of their vast importance.

Predicted Sea‐Level Rise‐Driven Biogeomorphological Changes on Fire Island, New York: Implications for People and Plovers

AbstractForecasting biogeomorphological conditions for barrier islands is critical for informing sea‐level rise (SLR) planning, including management of coastal development and ecosystems. We combined five probabilistic models to predict SLR‐driven changes and their implications on Fire Island, New York, by 2050. We predicted barrier island biogeomorphological conditions, dynamic landcover response, piping plover (Charadrius melodus) habitat availability, and probability of storm overwash under three scenarios of shoreline change (SLC) and compared results to observed 2014/2015 conditions. Scenarios assumed increasing rates of mean SLC from 0 to 4.71 m erosion per year. We observed uncertainty in several morphological predictions (e.g., beach width, dune height), suggesting decreasing confidence that Fire Island will evolve in response to SLR as it has in the past. Where most likely conditions could be determined, models predicted that Fire Island would become flatter, narrower, and more overwash‐prone with increasing rates of SLC. Beach ecosystems were predicted to respond dynamically to SLR and migrate with the shoreline, while marshes lost the most area of any landcover type compared to 2014/2015 conditions. Such morphological changes may lead to increased flooding or breaching with coastal storms. However—although modest declines in piping plover habitat were observed with SLC—the dynamic response of beaches, flatter topography, and increased likelihood of overwash suggest storms could promote suitable conditions for nesting piping plovers above what our geomorphology models predict. Therefore, Fire Island may offer a conservation opportunity for coastal species that rely on early successional beach environments if natural overwash processes are encouraged.

Effects of COVID-19 lockdowns on shorebird assemblages in an urban South African sandy beach ecosystem

Human pressures are pervasive in coastal ecosystems, but their effect magnitudes are masked by methodological limitations. Government lockdowns associated with the global COVID-19 pandemic can address this gap since lockdowns are effectively manipulations of human presence in ecosystems at scales unachievable otherwise. We illustrate this using a study on shorebirds in an urban South African sandy beach ecosystem. Data collected prior to (2019) and during the COVID-19 (2020) pandemic indicated an inverse relationship between shorebird and human numbers, but this was stronger in 2020. In 2020, human exclusion resulted in a six-fold increase in shorebird abundance relative to 2019. Following easing of lockdowns, shorebird abundance declined by 79.6% with a 34.1% increase in human density. Our findings highlight the sensitivity of shorebirds to recreational disturbance, the potential for current methodological approaches to underestimate repercussions of disturbance and the capacity for COVID-19 lockdowns to refine understanding of human-induced stress in ecosystems.

Disentangling patterns in population parameters of the wedge clam Donax hanleyanus from sandy beaches of Argentina: The role of environmental variability

The concurrent role of morphodynamics and estuarine gradients in shaping population patterns in sandy beach macrofauna has not been adequately assessed. Here, we analyze the effects of beach morphodynamics, salinity, sea surface temperature, and chlorophyll-a (chl-a) on life-history traits of the wedge clam Donax hanleyanus in four sandy beaches located along the estuarine gradient generated by the Río de la Plata (RdlP, Argentina) over a 13-month period. A general linear model showed that chl-a and salinity were positively correlated with the abundance of D. hanleyanus, whereas between-beach differences in individual size, population structure, and growth performance were mainly explained by salinity fluctuations. These results indicate that the estuarine gradient of the RdlP plays a critical role in shaping life-history traits, population structure, and abundance of D. hanleyanus at local to regional scales, overriding the effects of local characteristics of the habitat. The study highlights the importance of conducting multi-scale studies that integrate environmental factors to elucidate the main physical drivers of population patterns in sandy beach ecosystems.

Activity patterns of Cybotus estriatus (LeConte, 1878) (Coleoptera: Tenebrionidae) on a Caribbean beach

Sandy beach ecosystems are extreme environments in which darkling beetles (Tenebrionidae) have been usually reported as a dominant component of the fauna. The abundance and richness of tenebrionids in arid zones is facilitated by specific physiological, morphological, and behavioural traits, such as limited activity patterns or the use of suitable microhabitats. Activity patterns of tenebrionid beetles have been investigated mainly in large-size species, but the response of small species remains basically unknown. Considering this, we developed a study in a Caribbean beach in Costa Rica with the aim of identifying daily activity patterns of Cybotus estriatus (LeConte, 1878), a darkling beetle of 2–3 mm in length relatively frequent in the circum-Caribbean beaches. In addition, we assessed how vegetation cover influences the abundance of this small tenebrionid species. Observations were performed between 7:00 h to 18:30 h, within a range of temperatures from 28°C to 47°C. Cybotus estriatus exhibits a bimodal activity pattern similar to those observed for other tenebrionids. It remains active at a temperature range of 35°C to 44°C, but shows a higher activity around 10:00 h and 15:30 h, at temperatures between 38°C and 42°C. We also found a strong dependence of C. estriatus on beach vegetation, providing the first data on the effect of vegetation cover in small tropical beetles inhabiting sand beaches. Our results suggest that body size may not be the critical factor determining activity in tenebrionids, and that preserving the natural vegetation in sandy beaches is essential to maintain the biodiversity of these ecosystems.