The Early Shorebird Will Catch Fewer Invertebrates on Trampled Sandy Beaches

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.

Spatially associated or composite life traces from Holocene paleosols and dune sands provide evidence for past biotic interactions

Biotic interactions (e.g., predation, competition, commensalism) where organisms directly or indirectly influenced one another are of great interest to those studying the history of life but have been difficult to ascertain from fossils. Considering the usual caveats about the temporal resolution of paleontological data, traces and trace fossils in the sedimentary record can record co-occurrences of organisms or their behaviours with relatively high spatial fidelity in a location. Neoichnological studies and studies on recently buried traces, where direct trophic links or other connections between tracemakers are well-known, may help interpret when and where overlapping traces represented true biotic interactions. Examples from Holocene paleosols and other buried continental sediments in Poland include the tight association between mole and earthworm burrows, forming an ichnofabric representing a predator-prey relationship, and that of intersecting insect and root traces demonstrating the impact of trees as both ecosystem engineers and the basis for food chains. Trampling by ungulates, which leaves hoofprints and other sedimentary disturbances, may result in amensal or commensal effects on some biota in the short term and create heterogeneity that later trace-making organisms, such as invertebrate burrowers, can also respond to in turn, though such modified or composite traces may be challenging to interpret.

General macro-litter as a proxy for fishing lines, hooks and nets entrapping beach-nesting birds: Implications for clean-ups

Fishing lines, hooks and nets represent a sub-category of macro-litter potentially entrapping plover birds nesting on sandy beaches. Here, during a winter period, the accumulation pattern of both general beach litter and fishing lines, hooks and nets was analysed on four central Italy beaches. Despite the active monthly litter removal by clean-ups, there was not a decrease in its density during the winter period, due to the continuous accumulation by frequent winter storms. However, the entrapping litter was very low (<2.5 % of the general litter) and appeared directly correlated to the general litter density. Following a DPSIR approach, the general litter can act as an indirect pressure indicator (proxy) of the amount of entrapping litter. Therefore, an increase in general macro-litter should alarm those involved in the conservation of entanglement-sensitive bird species, such as plovers, suggesting that they should implement high-frequency clean-up activities aimed at removing it.

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.

Options for shorebird-exclusion devices for pitfall traps on sandy shores

Abstract ContextPitfall trapping is a standard technique for indexing surface active invertebrates on beaches, and underpins the study of sandy shore ecology. However, pitfall traps may pose a risk to the flightless young of beach-nesting birds, which may fall into such traps and potentially die. AimThe aim of the present study was to compare the invertebrates captured in standard pitfall traps with those captured in pitfall traps fitted with one of three potential shorebird exclusion devices. Ideally, the traps with exclusion devices would perform similarly to the standard traps (to enable inter-study comparability) and would detect ecological gradients, such as those evident in invertebrate assemblages between the beach and foredune. MethodsA systematic array was deployed, using 64 pitfall traps of four types: three types with bird-exclusion devices (a mesh cover, a fence around the rim and a low roof); and a standard pitfall trap with no exclusion device. Pitfall traps were stratified across two habitat types (upper beach and foredune) and were simultaneously deployed to control for environmental and other variables. ResultsEach trap type was broadly comparable in terms of the assemblage of invertebrates recorded, with two exceptions: (1) there was a slightly lower species diversity in mesh than in roofed traps; and (2) the assemblage captured differed between roofed and fenced traps, with the former trapping more isopods and amphipods. No trap type differed from control traps, and all differentiated an ecological gradient between beach and foredune. Thus, any trap design option we tested met our criteria. Conclusions and implicationsThe present study shows that bird-exclusion devices for pitfall traps need not compromise trap performance, comparability or utility.

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.

What we know and what we think we know: Revealing misconceptions about coastal management for sandy beaches along the U.S. Atlantic Seaboard

Management of coastal areas is necessary to maintain and protect existing permanent structures. Coastal erosion management falls into soft and hard shoreline stabilization options with the United States tending to favor hard. However, post-Hurricane Sandy 2012, soft dune and beach replenishment have become more favorable in the U.S. with support being necessarily contingent upon an understanding of the pros, cons, and concepts surrounding each management strategy. Misconceptions could thus lead to a halt in progress and poor decisions with implications for community safety. We sought to gain a better understanding of current knowledge surrounding best practices in coastal management communities. Our assumption was that misconceptions in one coastal area, New Jersey, are likely echoed in other coastal areas in the U.S. and internationally. We employed a two-phase research design with an exploratory phase using semi-structured interview guidelines to collect data from a quota sample of 53 local residents and then tested the distribution of knowledge about coastal management facts by asking a convenience sample of 300 residents a structured set of 15 questions. Study participants identify differences in how beaches are managed and how protected they conversely consider an area to be. Dunes are generally preferred over hard engineering and replenishment. However, many key concepts regarding how dunes function naturally, with regards to the role of vegetation and fencing, are poorly understood suggesting a need for greater education surrounding these topics. Participants support continued tax investment in coastal areas to avoid retreat but recognize a tragedy of the commons in such actions for future generations. Learning who knows what, may contribute to more fruitful dialogues among stakeholders to pave the way for the adoption of suitable and sustainable management practices for better protected shorelines.

Optimizing conservation benefits for threatened beach fauna following severe natural disturbances

Wildlife on sandy beaches is often constrained by transformation of natural areas for human use, and opportunities for acquiring or restoring new habitat are rare. Storms can often force changes in land use naturally by re-shaping coastal landforms, thereby creating high quality habitat; yet, wildlife requirements are seldom considered in post-storm recovery planning, and conservation practitioners lack suitable evidence to argue for the protection of habitats freshly formed by storms. Here we used a maximum-likelihood spatial modeling approach to quantify impacts of Hurricane Sandy (mid-Atlantic United States, October 2012) on nesting habitat of four bird species of conservation concern: American oystercatchers, black skimmers, least terns and piping plovers. We calculated the immediate storm-created changes (loss, persisting, gained) in nesting habitat under two levels of conservation protections: the current regulatory framework, and a scenario in which all potential habitats were under conservation protection. Hurricane Sandy resulted in apparent large gains for least terns (+181 ha) and piping plovers (+289 ha). However, actual gains were reduced to 16 ha for plovers and reversed for least terns (net loss of 6.4 ha) because newly formed habitat occurred outside existing reserve boundaries. Similarly, under the current management framework, black skimmer nesting habitat decreased by ~164 ha. We also tested whether birds benefited from newly created nesting habitat by identifying nest and colony locations for three years following Hurricane Sandy. All species overwhelmingly nested in habitat that existed prior the storm (76-98% of all nests/colonies); only a small percentage (≤17% for all species) occupied newly created habitat. We conclude that static spatial conservation efforts fail to capitalize on potentially large gains resulting from storms for several species and recommend flexible spatial conservation investments as a key input in post-storm recovery planning.

Managing birds of conservation concern on sandy shores: How much room for future conservation actions is there?

Resource limitations often prevent the active management required to maintain habitat quality in protected areas. Because restrictions in access or allowable public activities are the sole conservation measure in these locations, an important question to consider is whether species of conservation concern truly benefit from parcels that are shielded from human disturbance. Here, we assess the conservation benefit of protecting birds from human recreation on over 204 km of sandy beaches by (a) estimating the total area of beach-nesting bird habitat that has been created by conservation protections; (b) quantifying the change in nesting habitat extent should further conservation protections be implemented; and (c) providing data to inform future protected area expansion. We use a maximum entropy species distribution modeling approach to estimate the extent and quality of suitable habitat for four beach-nesting bird species of conservation concern under the existing management regime and compare it to scenarios in which the entire study area is either unprotected of fully protected from human disturbance. Managing humans has dramatic conservation returns for least terns and piping plovers, creating extensive nesting habitat that otherwise would not exist. There is considerable scope for conservation gains, potentially tripling the extent of nesting areas. Expanding conservation footprints for American oystercatchers and black skimmers is predicted to enhance the quality of existing nesting areas. The work demonstrates the utility of modeling changes in habitat suitability to inform protected area expansion on ocean beaches and coastal dunes.