Experimental Change of the Orientation of Two Populations of Talitrus saltator (Crustacea Amphipoda Talitridae) from Cap Bon (North‐Eastern Tunisia)

The orientation of sandhopper populations is adapted to the direction of the shoreline of the sandy beaches where they live; this behaviour was shown to be inherited in some Mediterranean populations. The question was open whether this behaviour could be adaptively modified in case of changing shoreline or passive transfer to a new differently oriented shoreline. The Cap Bon beaches in north‐eastern Tunisia are particularly interesting because they belong to two different Mediterranean Basins, the central and the eastern one, and their supra‐tidal populations do not come together. This work verified the effect of experimental change of the shoreline direction in two populations of Talitrus saltator from Cap Bon (north‐eastern Tunisia) through a displacement experiment. We transferred samples of T. saltator from two different localities (Korba and Ratiba) from their original beach to the familiar one and tested their solar and landscape orientation on the new beach that had an almost opposite direction with respect to the previous one. The comparisons of the results on the home beach and the new one confirmed the use of the solar compass in both populations, as well as the importance of landscape view and optical local sky factor in adjusting the escape direction. In both populations, an increase of scatter was observed on the new beach, especially when individuals could see the landscape. Also, a clear behavioural difference between the two populations was recorded, being Ratiba population not significantly oriented to the shoreline when tested on the unfamiliar beach, while Korba population maintained its home direction also on the new beach.     

Comparing methods used in estimating biodiversity on sandy beaches: Pitfall vs. quadrat sampling

We compared the two most commonly used sampling methods, pitfall trapping and quadrat sieving, to study community diversity and talitrid abundance on sandy beaches. They are both widely used methods, however they are related to different behaviors: surface activity (pitfall traps) and burrowing in the substrate (quadrat sieving). To detect bias intrinsically generated by the use of different sampling methods, we applied both methods on a set of five beaches in New South Wales, Australia. The set included non-contiguous beaches, exposed and sheltered, more or less affected by recreational use. The results indicated a high fluctuation in biodiversity features. However, the most human-frequented beaches were grouped together by Multi Dimensional Scaling, and substrate-modifiers talitrid amphipods (sand-hoppers), played a major role in this scaling. The analysis of similarities (ANOSIM) indicated the roles of exposure and human recreational use in shaping the community, while the methods (quadrats vs. traps) resulted in higher fluctuation within samples than between, and informative outliers. Generalized Linear Models developed to estimate the probability of capture of talitrids by sampling method pointed to a higher probability to capture both sand-hoppers and beach-hoppers with the quadrat method. We finally suggest: (1) the comparative use of both sampling methods whenever possible, to capture multiple information and avoid bias in biodiversity estimates; and (2) an ad-hoc strategy when dealing with target populations. In particular, attention should be paid when targeting co-occurring talitrid species characterized by different ecology and behavioral traits: sand-hoppers (substrate modifiers) appeared to be more sensitive than beach-hoppers (non-substrate modifiers) to the impacts considered. In terms of biodiversity assessment the methods were equal, but for talitrid sampling quadrat sieving was more efficient.     

Sandy beaches at the brink

Sandy beaches line most of the world's oceans and are highly valued by society: more people use sandy beaches than any other type of shore. While the economic and social values of beaches are generally regarded as paramount, sandy shores also have special ecological features and contain a distinctive biodiversity that is generally not recognized. These unique ecosystems are facing escalating anthropogenic pressures, chiefly from rapacious coastal development, direct human uses — mainly associated with recreation — and rising sea levels. Beaches are increasingly becoming trapped in a 'coastal squeeze' between burgeoning human populations from the land and the effects of global climate change from the sea. Society's interventions (e.g. shoreline armouring, beach nourishment) to combat changes in beach environments, such as erosion and shoreline retreat, can result in severe ecological impacts and loss of biodiversity at local scales, but are predicted also to have cumulative large-scale consequences worldwide. Because of the scale of this problem, the continued existence of beaches as functional ecosystems is likely to depend on direct conservation efforts. Conservation, in turn, will have to increasingly draw on a consolidated body of ecological theory for these ecosystems. Although this body of theory has yet to be fully developed, we identify here a number of critical research directions that are required to progress coastal management and conservation of sandy beach ecosystems.     

Talitrid and Tylid crustaceans bioecology as a tool to monitor and assess sandy beaches’ ecological quality condition

In the last decades, the sharp increase of human activities on sandy beaches has introduced several detrimental impacts on these ecosystems, highlighting the importance of developing environmental quality assessments and sustainable management and protection plans for these environments. The study of key species at the population level represents an adequate and important approach to the ecosystem's ecological quality if the impacts of environmental disturbances, namely derived from human activities, are to be assessed. Talitrid and Tylid crustaceans often form abundant populations in temperate exposed sandy beaches, and might represent the bulk of the macrofaunal communities. In the present case study, the comparison of distinct Talitrid and Tylid populations on Atlantic (Portugal) and Mediterranean (Italy and Tunisia) beaches allowed to assess the adaptation of these animals on local and macro scale scenarios and evaluate the importance of bioecological studies as auxiliary tools in environmental monitoring and in the ecological quality assessment of sandy beaches. The results revealed that Talitrid and Tylid populations have a strong plasticity over geographic gradients and to local environments, presenting a high degree of variation on population ecology, namely latitudinal clines on several life history traits. Also, since the studies were performed on sandy beaches with similar degrees of exposure to wave action and low degrees of human disturbance, the present work may play a relevant role as reference knowledge in environmental monitoring studies and as an ecological quality assessment tool that might be used to evaluate the impacts of environmental disturbances on sandy beach ecosystems, namely from human origin.     

Sub-lethal effects of off-road vehicles (ORVs) on surf clams on sandy beaches

Ecological impacts of vehicle traffic are a significant environmental management issue on many sandy shores. Impacts usually focus on lethal effects of vehicles to organisms, but sub-lethal effects which could reduce the fitness of macrofauna populations are equally possible but unknown. Consequently, we measured changes in body condition and burrowing performance of the beach clam Donax deltoides subjected to vehicle traffic on sandy shores in eastern Australia. Body mass index of clams on beaches open to traffic was 16% lower, but gonadosomatic index and relative valve thickness were not consistently linked to vehicle access to beaches. By contrast, off-road vehicles significantly impaired the burrowing performance of clams. After experimental exposure to ORV traffic (30 passes) and dislodgement from the sediment, the time taken for clams to re-bury into the sand doubled irrespective of the vehicle weight used. Because burrowing is such a critical function in the behavioural repertoire of sandy beach animals, the traffic-induced changes to organisms' performance found in this study may increase mortality by causing displacement to less favourable habitats by swash, and by intensifying the risk of predation and desiccation. When assessing the ecological impacts of vehicles on beach fauna, it is thus important to consider both lethal and sub-lethal effects.     

A molecular phylogenetic study of the freshwater talitrid amphipod Orchestia cavimana (Crustacea).

In this paper we performed a molecular phylogenetic study of Orchestia cavimana, the sole talitrid amphipod inhabiting beaches of European freshwater lakes and rivers. For that purpose, we have PCR amplified and sequenced regions of the mitochondrial cytochrome oxidase subunit I (COI) gene, basing our analysis on both nucleotide and amino acid sequences and considering also structural classes of the COI enzyme. Phylogenetic analyses were conducted by neighbour-joining (NJ) and maximum-parsimony (MP) methods comparing homologous sequences of talitrids and other Crustacea. In both NJ and MP trees, O. cavimana shows a basal placement with respect to other talitrid amphipods.     

Simple estimate of filtration rates on a sandy beach

A new, simple and inexpensive method is proposed to determine the rate of water filtration in the swash zone of lakeshore beaches. Rates of water filtration on a sandy beach were determined by measuring the residue of a tracer injected into several cylinders buried vertically in the sandy layer at various locations from the shoreline to the tip of the swash zone. This methodology enabled the separate estimation of mean infiltration and exfiltration rates. The results obtained for seashore beaches were in accordance with previous data obtained by more conventional methods. The filtration rate results for lakeshore sandy beaches were almost equivalent to seashore sandy beaches, despite a shorter swash length. This paper indicates that this is caused by a larger grain size and shorter wave period. This method presents an easy approach to determine rates of water filtration in sandy beaches and is expected to further promote studies in this field.     

Keynote papers on sandhopper orientation and navigation

This article analyses the relevant studies that have made sandhoppers a model subject for the study of orientation, and traces the development of the paradigm through innovative hypotheses and empirical evidence. Sandhoppers are able to maintain their direction without sensorial contact with the goal, which is their burrowing zone extended along the beach, but very narrow across it. They actively determine the direction of their movements, according to their internal state and the environmental features encountered. Each population shows an 'innate directional tendency' adapted to the shoreline of origin, and the inexpert laboratory-born young behave in a similar way to the adults. Genetic differences have been demonstrated between, as well as within natural populations. The question of the calibration of the sun compass to orientation on a particular shoreline implies a redundancy of mechanisms of orientation. Orientation mechanisms may involve environmental cues perceived through diverse sensory modalities, and range from simple orientation reflexes to sun compass navigational systems. These include scototaxis and geotaxis, and the response to the silhouette of the dune, in addition to sun and moon orientation, which is dependent on the time of the day and orientates daily migrations on the beach. Different modalities of orientation may operate singly, or in conjunction with each other, and their ecological significance may vary according to the habitat and lifestyle of the animals. Taken collectively, the orientation behaviour of the group appears to be a most accommodating phenotype, with considerable adaptive potential. The evidence from comparative studies of different populations promotes consideration of behavioural plasticity as an adaptation to changing coastlines.     

Climate‐change impacts on sandy‐beach biota: crossing a line in the sand

Sandy ocean beaches are iconic assets that provide irreplaceable ecosystem services to society. Despite their great socioeconomic importance, beaches as ecosystems are severely under‐represented in the literature on climate‐change ecology. Here, we redress this imbalance by examining whether beach biota have been observed to respond to recent climate change in ways that are consistent with expectations under climate change. We base our assessments on evidence coming from case studies on beach invertebrates in South America and on sea turtles globally. Surprisingly, we find that observational evidence for climate‐change responses in beach biota is more convincing for invertebrates than for highly charismatic turtles. This asymmetry is paradoxical given the better theoretical understanding of the mechanisms by which turtles are likely to respond to changes in climate. Regardless of this disparity, knowledge of the unique attributes of beach systems can complement our detection of climate‐change impacts on sandy‐shore invertebrates to add rigor to studies of climate‐change ecology for sandy beaches. To this end, we combine theory from beach ecology and climate‐change ecology to put forward a suite of predictive hypotheses regarding climate impacts on beaches and to suggest ways that these can be tested. Addressing these hypotheses could significantly advance both beach and climate‐change ecology, thereby progressing understanding of how future climate change will impact coastal ecosystems more generally.     

Local scale processes drive long‐term change in biodiversity of sandy beach ecosystems

Evaluating impacts to biodiversity requires ecologically informed comparisons over sufficient time spans. The vulnerability of coastal ecosystems to anthropogenic and climate change‐related impacts makes them potentially valuable indicators of biodiversity change. To evaluate multidecadal change in biodiversity, we compared results from intertidal surveys of 13 sandy beaches conducted in the 1970s and 2009–11 along 500 km of coast (California, USA). Using a novel extrapolation approach to adjust species richness for sampling effort allowed us to address data gaps and has promise for application to other data‐limited biodiversity comparisons. Long‐term changes in species richness varied in direction and magnitude among beaches and with human impacts but showed no regional patterns. Observed long‐term changes in richness differed markedly among functional groups of intertidal invertebrates. At the majority (77%) of beaches, changes in richness were most evident for wrack‐associated invertebrates suggesting they have disproportionate vulnerability to impacts. Reduced diversity of this group was consistent with long‐term habitat loss from erosion and sea level rise at one beach. Wrack‐associated species richness declined over time at impacted beaches (beach fill and grooming), despite observed increases in overall intertidal richness. In contrast richness of these taxa increased at more than half (53%) of the beaches including two beaches recovering from decades of off‐road vehicle impacts. Over more than three decades, our results suggest that local scale processes exerted a stronger influence on intertidal biodiversity on beaches than regional processes and highlight the role of human impacts for local spatial scales. Our results illustrate how comparisons of overall biodiversity may mask ecologically important changes and stress the value of evaluating biodiversity change in the context of functional groups. The long‐term loss of wrack‐associated species, a key component of sandy beach ecosystems, documented here represents a significant threat to the biodiversity and function of coastal ecosystems.     

Mortalities caused by off-road vehicles (ORVs) to a key member of sandy beach assemblages,the surf clam <Emphasis Type="Italic">Donax deltoides</Emphasis>

Sandy beaches are prime recreational areas, but human use of beaches is not without ecological consequences. Driving of off-road vehicles on beaches for recreational pursuits is perhaps the physically most severe form of direct anthropogenic disturbance on sandy shores. Potential management and conservation interventions lack, however, data on how sensitive beach species are to vehicle impacts. We therefore experimentally quantified the link between beach traffic and lethal damages caused by vehicles to sandy shore invertebrates, using surf clams (Donax deltoides) as the biological response variable. Although clams had some tolerance against vehicles at low traffic volumes (5 vehicle passes), more than half of them were killed at higher traffic volumes (75 passes) in situations where cars traversed soft sand and turned across the beach face. Overall, both traffic volume and driver behaviour (i.e. straight vs. turning vehicle tracks) determined the incidence of direct crushing of clams under vehicles. Our data demonstrate that recreational use of ORVs is a source of mortality for beach invertebrates, but equally caution against extrapolating impact data from hard-shelled clams to potentially more sensitive soft-bodied species. Robust management interventions that seek to mitigate ecological damage from beach traffic will therefore require information on the functional relationship between the form, intensity and frequency of human disturbance and the biological responses for entire faunal assemblages on sandy shores. Handling editor: T. P. Crowe     

Sandy beach macrofaunal assemblages as indicators of anthropogenic impacts on coastal dunes

Ocean sandy beaches are iconic recreational assets to society and have undergone rapid degradation caused by both natural and anthropogenic pressures. A major effect of urbanisation on biota stems from artificial structures placed in aquatic systems. While the installation of these structures has been widespread, our understanding of how they impact shoreline habitats and fauna is relatively limited. On the sandy Leirosa Beach, on the European Atlantic coast (Portugal), a decade of cumulative impacts was recorded, with disruption of the frontal dune, dune nourishment and the incorporation of geotextiles to reconstruct the dune and maintain it as an artificial structure. Two years after the dune rehabilitation process at Leirosa Beach, seasonal sampling campaigns (from spring 2010 to winter 2011) were carried out to assess the effects of the artificial dune (and the first signs of its eventual disruption) on macrofauna compared to a natural dune on the same beach. During the study period, the rehabilitated foredune maintained the average slope, with similar sediment characteristics (finer sediments) when compared with the natural dune system, with no physical significant differences being appreciated between the two sites. The macrofaunal assemblages were represented especially by crustaceans (amphipods and isopods), with similar mean total density, taxon richness and diversity between sites. Special attention was given to the supralittoral species, and the results revealed that the natural zone harboured a significantly higher density of sandhopper Talitrus saltator with respect to the artificial zone. PERMANOVA results detailed the significant difference that occurred, particularly during the warmer seasons (spring and summer 2010), the recruitment period described for this species along this coast. In fact, SIMPER analysis revealed that T. saltator accounted for 46% of the dissimilarities between the natural and artificial dune sites. The presence of geotextiles extending across the supralittoral zone appeared, on the one hand, to allow for the presence of talitrids, but the application of textiles around the area prevented them from burrowing, thus causing them to avoid the rehabilitated area. The results highlighted the potentially negative effects of this artificial dune system if textile disruption continues, and the usefulness of T. saltator as an effective and reliable ecological indicator for these ecosystems. Thus, evaluating the risks and magnitude of human interventions is a major challenge for sandy beach ecologists, and baseline information is required if we are to better understand how resident macrofaunal species deal with future impact scenarios.     

Orientation of Phalerisida maculata Kulzer (Coleoptera, Tenebrionidae) in sandy beaches of the Chilean coast. Orientation of Phalerisida maculata in sandy beaches

The orientation stimuli of adult individuals of the beetle Phalerisida maculata Kulzer (Coleoptera, Tenebrionidae) over the beach surface, were studied at two sandy beaches of the chilean coast approximately 1300 km apart, Apolillado (ca. 29 degrees S) and Playa Universitaria de Mehuín (ca. 39 degrees S). Phalerisida maculata did not orient by astronomic cues such as the sun and moon, nor by the terrestrial magnetic field. Both populations showed positive scototaxis, and oriented downward on slopes with dry sediments, and upwards on slopes with wet sediments.     

Sensitivity of a cirolanid isopod to human pressure

Cirolanid isopods are conspicuous members of the supralittoral and intertidal fringes of sandy beaches around the world, being dominant in terms of number or biomass. Excirolana braziliensis is one of the most abundant species on exposed sandy beaches, both urbanized and preserved, of Rio de Janeiro in southeast Brazil. Considering the negative effects of urbanization and human pressure on sandy beaches, this study aimed to analyze the population structure and reproductive aspects of E. braziliensis in different stretches of Barra da Tijuca beach (Rio de Janeiro, Brazil), which differ with respect to urbanization and occupation by bathers. Monthly samplings of E. braziliensis were conducted throughout 12 months within urbanized and preserved stretches, including measurements of beach parameters and human pressure. The anthropogenic effect seems to be a relevant factor in explaining the variability in the population structure of this species. Negative significant correlations were found between the species density and the number of visitors, who massively occupies the urbanized stretches. Similar life history strategies were observed for different populations of E. braziliensis. Although high fecundity rates were reported to all stretches, the probability of eggs/embryos survival under the adverse conditions provided by the Barra da Tijuca beach is not clearly known. According to the results of this study, it could be inferred that the human pressure over Barra da Tijuca beach affects the populations: (1) directly, through human trampling and/or natural habitat jeopardizing; or (2) indirectly, by the isolation of individuals in the preserved stretch, located between environments subjected to intense disturbance. In such case, the species strategy to thrive in a protected area of restricted size, within a highly urbanized and occupied area by bathers does not appear to be the best conservation measure for peracarid species, as in E. braziliensis. Nevertheless, E. braziliensis turned out to be a good monitoring species of impacts due to its high resistance to environmental stress, persisting in highly urbanized areas dominated by bathers.     

Variation of the locomotor activity rhythms in three species of Talitrid amphipods, Talitrus saltator, Orchestia montagui, and O. gammarellus, from various habitats

The expression of biological rhythms was investigated in five populations of three different species of talitrid amphipods from various habitats in the Maremma Regional Park, Grosseto, Italy: Talitrus saltator (from a sandy beach and a canal), Orchestia montagui (form a Posidonia banquette), and O. gammarellus (from a cave entrance and a river bank). Locomotor activity rhythms were recorded in individual animals over 21 days in constant dark at a temperature of 18 degrees +/-1 degrees C. A high variability in rhythm expression was evident, not only among species and populations but also within populations and the activity pattern of individuals. Activity rhythms of T. saltator and O. montagui were similar, with a good definition and precise circadian periodicity, whereas O. gammarellus showed a high variability and low definition of the circadian rhythm. Significant differences were also observed between two populations of O. gammarellus and T. saltator from different habitats. Within the O. gammarellus species, a significantly higher percentage of active animals (p<0.001) was observed in the cave than the river-bank population; within T. saltator, a significantly lower percentage of active animals (p<0.01) and higher percentage of periodic animals (p<0.05) was found in the canal than the sandy beach population. With reference to environmental stability and variability, the differences observed are explained as a need for plasticity to adapt to environmental changes.     

Latitudinal patterns in abundance and life-history traits of the mole crab Emerita brasiliensis on South American sandy beaches

Demographic and life‐history attributes of the mole crab Emerita brasiliensis were analysed along 2700 km of the Atlantic coast of South America, including sandy beaches at the southernmost limit (Uruguay) and at the core of its geographical range (Brazil). Population features varied markedly within this range and exhibited systematic geographical patterns of variation. Abundance significantly increased from temperate to subtropical beaches, and the same held true for the asymptotic weight of males. Conversely, length at maturity and asymptotic weight of females increased from subtropical to temperate beaches, being inversely related to sea water temperature. Macroecological patterns in abundance and body weight showed the first large‐scale evidence of scaling of population density to body size for a sandy beach population. Mortality rates (both sexes) followed a nonlinear increase from low‐density temperate beaches to high‐density subtropical beaches. The effect of habitat quality and availability could explain discontinuities in the species distribution within its range, and also differential responses in life‐history attributes at a local scale. Asymmetries and converse latitudinal trends between sexes suggest that there is not a single general factor determining large‐scale patterns in life‐history traits of this species. Our results reinforce the view that density‐dependent and environmental factors operating together regulate sandy beach populations. The need to develop macroecological studies in sandy beach ecology is highlighted, as knowledge acquired from local to large spatial scales throws light on population structure and regulation mechanisms.     

Effects of Fishing and Fishing Closures on Beach Clams: Experimental Evaluation across Commercially Fished and Non-Fished Beaches before and during Harvesting

Management responses to reconcile declining fisheries typically include closed areas and times to fishing. This study evaluated this strategy for a beach clam fishery by testing the hypothesis that changes in the densities and size compositions of clams from before to during harvesting would differ between commercially fished and non-fished beaches. Sampling was spatially stratified across the swash and dry sand habitats on each of two commercially fished and two non-fished beaches, and temporally stratified across three six-week blocks: before, early and late harvesting. Small-scale spatio-temporal variability in the densities and sizes of clams was prevalent across both habitats and the components of variation were generally greatest at the lowest levels examined. Despite this, differences in the densities and sizes of clams among individual beaches were evident, but there were few significant differences across the commercially fished versus non-fished beaches from before to during harvesting. There was no evidence of reduced densities or truncated size compositions of clams on fished compared to non-fished beaches, contrasting reports of some other organisms in protected areas. This was probably due to a combination of factors, including the current levels of commercial harvests, the movements and other local-scale responses of clams to ecological processes acting independently across individual beaches. The results identify the difficulties in detecting fishing-related impacts against inherent levels of variability in clam populations. Nevertheless, continued experimental studies that test alternate management arrangements may help refine and determine the most suitable strategies for the sustainable harvesting of beach clams, ultimately enhancing the management of sandy beaches.     

Polarotaxis and scototaxis in the supratidal amphipod Platorchestia platensis

Talitrid amphipods use many cues for orientation during forays between temporary burrows and feeding areas, and for locating beaches when submerged, with visual cues being particularly important. Little evidence exists for polarized light among these visual cues despite extensive orientation by celestial and underwater polarized light in other crustaceans and in insects. We used electroretinography to assess spectral sensitivity in the eye of the beach flea Platorchestia platensis, and behavioral studies to test whether linearly polarized light serves as an orientation cue. Two spectral classes were present in the P. platensis eye with maxima at 431 and 520 nm. Non-uniform orientation of amphipods in the laboratory arena required either light/dark or polarized cues. Scototactic movements depended on arena conditions (day/night, wet/dry), while orientation under linearly polarized light was wavelength-dependent and parallel to the e-vector. Subsequent tests presented conflicting and additive scototactic and polarotactic cues to differentiate among these responses. In dry conditions, orientation parallel to the polarization e-vector overcame a dominant negative scototaxis, confirming that polarotaxis and scototaxis are separate orientation responses in this species. These behavioral results demonstrate talitrid amphipods can perceive and orient to linearly polarized light, and may use it to orient toward preferred zones on beaches.     

Temporal and spatial patterns of organic carbon are linked to egg deposition by beach spawning horseshoe crabs (<Emphasis Type="Italic">Limulus polyphemus</Emphasis>)

The spring spawning by the American horseshoe crab (Limulus polyphemus L.) results in temporally and spatially discrete inputs of eggs onto sandy beaches in Delaware Bay, USA. We tested the hypothesis that seasonal patterns of sediment organic carbon on Delaware Bay beaches is linked to this pulsed input of horseshoe crab eggs. At a location with minimal horseshoe crab spawning activity (Higbee Beach), there was little seasonal variation in sediment organic carbon, no distinction between organic carbon levels as a function of shoreline position or sediment depth, and no significant correlation between the abundance of crab eggs and percent organic carbon. Conversely, at a prime horseshoe crab spawning habitat (North Beach), organic carbon levels were seasonally pulsed and were correlated with egg abundance. Moreover, the strongest evidence of seasonality was seen at the middle foreshore location at the 15–20 cm depth, consistent with the highest input of horseshoe crab eggs. Although some of the organic carbon contributed by horseshoe crab eggs in May–June leaves the beach in the form of hatched larvae later in the year, there is a net input of organic carbon to the system in the form of unfertilized and/or dead eggs, egg membranes, and embryonic molts. We suggest that the inputs of eggs from horseshoe crabs and other beach spawning animals, such as grunion and capelin, make significant contributions to the energy budget of sandy beaches.