A study of the endogenous activity rhythms of the marine isopod Exosphaeroma truncatitelson

The endogenous activity rhythms of the South African endemic isopod Exosphaeroma truncatitelson were explored. Isopods were collected on days coinciding with either a neap or spring tide. High- and low-energy beaches, which vary in the intensity of wave action, were selected as study sites. Isopods, in groups of 10–30, were placed in glass tanks with different experimental conditions: darkness + no sand, darkness with sand and natural ambient light (no sand). Activity of the isopods was measured for 50 h by recording the number of isopods swimming actively during a 30-s period. These isopods exhibited an endogenous activity rhythm which coincided with the tidal cycle even though removed from their natural habitat. Cosine curves were fitted to the observed activity data and statistical differences across variables were investigated. Peak activity was shown to occur shortly after high tide. Similar activity cycles were observed for both neap and spring tides and for different times of the year. Results also indicated that the activity cycles at both low- and high-energy beaches were similar. Two survival advantages of this rhythm are proposed: prevention of stranding on high shores and competitive avoidance with other local isopod species.     

The genus Eurydice on the west coast of India

An ecological survey of the sandy beaches of the west coast of India revealed an important population of eurydicid isopods ( Eurydice peraticis Jones; E. indicis sp. nov.) of which one species is new to science. The systematics of these isopods are described, and their distribution on the Arabian Sea coast and the Indian beaches is discussed. Differences in their horizontal and vertical distribution on the beaches are explained in relation to the prevailing environmental conditions, of which exposure is the most important.     

Swimming ability and burrowing time of two cirolanid isopods from different levels of exposed sandy beaches

Most of the macroinfauna from sandy beaches is highly mobile, emerging out of the sediment when the tide rises, and using the swash to migrate up and down the beach face or feed (searching for prey or carrion). After swash excursions, they usually burrow back into the sediment, maintaining zonation at low tide. Therefore, the different species abilities to emerge, move around and burrow under different swash climates and sediment conditions are expected to influence observed distribution patterns. Nonetheless, few attempts have been made to understand behavioral mechanisms of these organisms in moving fluids.In this study, we used a flume tunnel to investigate the orientation, swimming ability and burrowing time of two similar species of cirolanid isopods, Excirolana armata Dana and Excirolana braziliensis Richardson, under current velocities ranging from 5 to 30 cm·s⁻¹. E. armata inhabits middle levels of dissipative to intermediate beaches, while E. braziliensis is found towards the upper level of a wider range of beach states. Both species oriented countercurrent above a threshold velocity, which turned out to be significantly lower for E. armata than for E. braziliensis. E. armata proved to be a stronger swimmer as shown by the higher velocities surmounted, and the less drags experienced at the highest current velocity. E. armata also burrowed faster than E. braziliensis. Burrowing time was affected by sediment grain size and water content, but not by water flow. Once organisms managed to begin burrowing under different flow conditions, they were not affected by current velocity. Nonsaturated sand precluded burial, while coarse sand retarded it. Differences in the observed patterns of across-beach distribution may thus be the result of species-specific behavioral responses to swash climate, manifested in swimming ability, burying and orientation in directional flows.     

Exotic oniscideans (Crustacea: Isopoda) in coastal salt marshes: first record of the families Halophilosciidae and Platyarthridae in Continental Chile

We report two new exotic introduced isopods in Chile: Halophiloscia couchii of the family Halophilosciidae and Niambia capensis of the family Platyarthridae. This report provides first evidence of the presence of these species in the Southeastern Pacific. These species were found in several salt marshes and beaches spanning nearly 2000?km of the Chilean coast. With the data reported here, the percentage of exotic oniscidean isopods in Chile is 28%.     

Competitive interactions in macroinfaunal animals of exposed sandy beaches

The influence of biotic interactions in structuring macroinfaunal communities of exposed sandy beaches, an unstable habitat characterized by strong physical forces, is generally considered negligible. We investigated the hypothesis that competitive interactions during burrowing could potentially affect the intertidal distribution and abundance of macroinfaunal animals of sandy beaches using two species of invertebrates, a hippid crab, Emerita analoga, and a bivalve, Mesodesma donacium, common along the coast of Chile. Spatial overlap in the intertidal distributions of these species was dynamic, varying with abundance, location, time of year and tide. Highest density zones of each species were often distinctly separated at low tide and spatial overlap in their distributions decreased significantly with increasing density, suggesting density dependence of the interactions. Negative relationships between densities of the two species at the smallest spatial scale examined also suggested active interactions among individuals. Over a tidal cycle, peak densities of the two species overlapped suggesting that interactions could occur frequently. Burrowing performance of E. analoga varied between size classes in three experimental densities of clams (5, 10 and 15 clams 0.008 m^-2) and in controls with no clams. Burrowing times of large crabs were significantly longer (~twofold) in all densities of clams than in controls, while those of small crabs did not differ significantly among treatments and controls. Large crabs also displaced clams from the sand while burrowing suggesting that two mechanisms of direct interference can occur, both of which could increase exposure of individuals involved to active swash and transport across or along the beach with potentially negative consequences. Our results suggest that competitive interactions capable of affecting zonation and population and community biology on a number of scales can occur among burrowing macroinfauna on exposed sandy beaches. Those interactions could be more ecologically significant than previously appreciated and may contribute to patterns observed in community structure and zonation on sandy beaches. Our results illustrate the potential importance of negative biological interactions in a physically stressful environment.     

Taxonomy,natural history and zoogeography of sand beach isopods from the coast of Southern Chile

Seven species of marine isopods were collected on sandy beaches of Southern Chile (from about 37° S until 42° S). From these, Excirolana hirsuticauda Menzies, Excirolana monodi Carvacho, Chaetilia paucidens Menzies, Macrochiridothea setifer Menzies and M. mehuinensis Jaramillo are known only from the Chilean coasts. Another species, Excirolana braziliensis Richardson, is known from other areas of American coasts. One species is identified here as Macrochiridothea aff. lilianae by its resemblance with M. lilianae Moreira from Southern Brazil. All these species are here briefly described and some aspects of their ecology added. Also Zoogeographic characterization of the studied area is discussed in relation to the distributional patterns of isopods living in them.     

Ovoviviparity in the genus Excirolana (Crustacea: Isopoda)

Studies on the intertidal sand-beach isopod, Excirolana chiltoni , have shown the species to be ovoviviparous. Large yolk-filled eggs are deposited into paired uteri of the female where they remain throughout gestation. Intrauterine development progresses through five stages and terminates upon birth of the manca which is morphologically similar to the adult but lacks the eighth pair of thoracic legs. The oostegites while present are much reduced and form a genital operculum rather than a brood pouch as they do in the majority of free living isopods. Six other species of Excirolana examined in the course of this investigation show evidence of internal incubation. Ovoviviparity thus appears to be characteristic of the entire genus, members of which live on exposed sand beaches throughout tropical and warm temperate regions of the world. Internal retention of embryonic stages provides protection against a number of environmental stresses peculiar to this sort of habitat.     

Parasitism by isopods in sandy beach fish assemblages: role of urbanization and environmental characteristics

Parasitism by isopods is a common phenomenon in marine fishes and may induce negative effects, especially in juvenile stages. The surf-zones of sandy beaches are an important nursery habitat for many fish species, including commercially important ones, and are structured by beach characteristics and human activities, which are suggested to influence the fishes’ susceptibility to parasitism. Here, we analyze the early infestation and prevalence of parasitism in surf zones fishes of 27 beaches in southeastern Brazil with different characteristics. Parasites were recorded in only seven of the beaches. A high infestation was found in a single site, the highly urbanized Itaguá beach, where the prevalence of parasitism on juveniles and early adults of the Atlantic anchoveta Cetengraulis edentulus was high (68.11%). Four species of parasitic isopods were found, all belonging to the Cymothoidae family, but Livoneca desterroensis was the most abundant (78.7%). No effects of parasitism were detected on the size, weight and physiological condition of fishes, but presence of parasites and prevalence of infestation were positively affected by urbanization. Overall, our results indicate that the surf-zones have low parasite infestation, yet, they suggest that anthropic effects such as urbanization may enhance the prevalence of isopod parasitism.

     

Zonation of vegetation on lacustrine coastal dunes: effects of burial by sand

More than 50 years ago it was proposed that zonation of major plant species on coastal dunes was determined by salt spray. Here, we argue against this hypothesis because (i) salt concentrations rarely exceed toxic levels; (ii) high precipitation in temperate latitudes washes the salt off the plants; (iii) major salt spray events occur in late autumn and winter when plants are dormant; and (iv) zonation also occurs on lacustrine dunes. Instead, we show evidence that zonation may be caused by burial because plant distribution was correlated with sand deposition and species were eliminated when burial exceeded their limits of tolerance, thus creating zones of different plant species. We conclude that in temperate regions (i) burial by sand may be among the most important factors in zonation, while salt spray may play a secondary role; and (ii) single environmental factors cannot be the determinants of a phenomenon as complex as species zonation.     

Is zonation on coastal sand dunes determined primarily by sand burial or by salt spray? A test in New Zealand dunes

There has long been controversy on which environmental factor is the predominant determinant of community zonation on sand dunes. It is demonstrated here that, on a dune system in southern New Zealand, several environmental factors that could limit growth all vary along the sea-to-inland sand dune zonation: soil moisture, soil nutrients, wind exposure, sand burial, salt spray and soil salinity. Correlation of the responses of 30 species to experimental stress (burial, darkness, rooting-medium salinity and salt spray) with the zonation of the species in the field indicates that, in the four dune systems studied, sand burial and salt are both important, with salt generally being the more important. However, the relative importance of the factors differs between sites.     

The importance of sand albedo for the thermal conditions on sea turtle nesting beaches

At Ascension Island and Cyprus, major nesting areas for green turtles ( Chelonia mydas ) in the Atlantic and Mediterranean, respectively, visual inspection shows some beaches are light in colour while others are darker. We objectively measured the albedo of the sand on different beaches, i.e. the percentage of the incident solar radiation that was reflected from the sand surface. At sites where albedo was recorded, we also measured the temperature of the sand at nest depths. At both rookeries, the sand temperature was markedly higher on darker beaches due to greater absorption of the incident solar radiation over the diurnal cycle. Temperature loggers buried at nest depths revealed seasonal changes in temperature on both islands, but showed that the lowest temperatures found on the darker beaches rarely dropped below the highest temperatures on the lighter beaches. Sea turtles exhibit temperature-dependent sex determination. Since sand albedo is a major avenue for the production of a range of incubation temperatures on both islands, it will also have profound implications for hatchling sex ratios. In comparison with both Ascension Island and Cyprus, for samples collected from sea turtle rookeries around the world there was an even greater range in sand albedo values. This suggests that sand albedo, a factor that has previously received little consideration, will have profound implications for nest temperatures, and hence hatchling sex ratios, for other populations and species.     

Temporal development of vegetation and geomorphology in a man-made beach-dune system by natural processes

Twenty-four yrs of primary succession in a man-made beach-dune system at the Baltic coast of Denmark, built of calcareous, marine sand and the dune planted with Ammophila arenaria , was studied by qualitative observations, quantitative records in permanent plots, levelling and soil analysis within a selected area of 0.75 ha. The aim of the study was to discuss whether human initiated and influenced beach and dune dynamics mimick natural beach and dune processes, and to discuss the relationship between succession and zonation. During the study period, which started in 1979, the man-made dune stabilized rather fast. In the stabilized dune, a sand-pararendzina with a thin A-horizon developed. The beach expanded by accretion of less calcareous, marine sand. On the beach new dunes, 3 m high, successively developed. The number of species in the study area increased from 16 to 55, accompanied by species and life form dynamics, characteristic for primary succession on sandy coasts. A gradual change in species composition of the permanent plots, which appeared by a DCA analysis, could by using TWINSPAN be structured into four groups or plant communities, which reflect succession as well as zonation. Two groups represent the vegetation of sandy beaches with annual dicotyledon species, and mobile dunes dominated by rhizomatous geophytes, especially A. arenaria. The two other groups represent stabilized, calcareous dune, dominated by hemicryptophytes, specially Festuca rubra , and less stabilized dune with F. rubra and the invasive alien Rosa rugosa. It was concluded, that the main trends in the geomorphological and vegetational development of the man-made beach-dune system is similar to the development in natural dunes. In the future, further accretion and seaward dune formation may be expected, but is it also expected, that larger parts of the area gradually will be covered by low scrubs of R. rugosa.     

Enhancement of habitat heterogeneity and species richness on rocky shores inundated by sand

Summary Many rocky shores are subject to periodic inundation by sand, which is often thought to reduce species richness by eliminating organisms intolerant of sand scour or sand smothering. However, regular disturbance (e.g. inundation) should promote richness by preventing the development of low diversity climax communities. A study of faunal richness on 10 regularly inundated shores showed that inundation does promote richness, but by increasing habitat heterogeneity. Some species are excluded from parts of the shore by sand, but because of the patchiness of sand deposits they are rarely excluded from the entire shore. Other species are found only on rocks associated with sand, while typically sandy shore animals occur in the sand deposits themselves. Total richness (281 species) was greater than for local noninundated shores and sandy beaches combined.     

In depth review of the ecology of arenicolous marine fungi

As an ecotone, sandy beaches exist within a multi-dimensional mesh of environmental gradients, shaped by numerous parameters (e.g. temperature, humidity, wave action, sand particle size and salinity). These limit the proliferation of a narrow group of fungal species. Obligate arenicolous marine fungi are an ecological assemblage of sand-associated heterotrophs that inhabit sandy beaches. These organisms have evolved to cope with dynamic beach conditions, having a cosmopolitan distribution across tropical, subtropical and temperate regions. Herein we provide an overview of published works relating to the fungi of sandy beaches, focusing on the past half-century. We outline a broad range of topics in ecology including fungal adaptive traits to intertidal conditions at the morphological and genetic levels, temporal and spatial patterns in community structure, and species variations in substrate preference. Collectively, these concepts should encourage marine mycologists to embrace a holistic set of perspectives to shape the outlook for beach ecology.     

Geographic variation for colour in the sandburrowing beetle Chaerodes trachyscelides White (Goleoptera: Tenebrionidae) on New Zealand beaches analysed using CIELAB L * values

Chaerodes trachyscelides White is a highly specialized, flightless burrowing beetle confined to the narrow strip of sand at and just above high water level on sandy marine beaches in New Zealand. Although the ventral surface of the beetle is always pale, the dorsal surface varies from pale to almost black. Large samples of this beetle were taken, together with the sand, from 11 beaches on New Zealand's three main islands. The colour of the dorsal surface of each individual beetle and that of the sand samples was measured using reflectance spectroscopy and expressed as CIE L*,a*,b* (CIELAB) values. The L* values, which are objective, quantitative measures of the degree of lightness of the beetles, were subjected to statistical and frequency analysis. Although the species was very variable in colour and the variation appeared to be continuous, a highly significant correlation was obtained between the mean of the L* values for the samples on each beach and that of the sand, the correlation coefficient being 0.961. This close association between the lightness of the beetles and that of the sand suggests the variable melanism functions as cryptic colouration. On most beaches, the distribution oflightness among the beetles sampled conformed to a normal curve. For beetles from sites where the sand was relatively uniform, such as the black Taranaki beaches, the L* frequency distribution curves were narrow and the coefficient of variation of mean beetle colour was relatively small indicating low colour variability. In contrast, the greatest within-site variability occurred on the two Stewart Island beaches sampled, where in each case there was less uniformity in the colour of the sand. At one of these sites, Maori Beach, darker sand present below the high water level is often deposited on the zone occupied by the beetles after storms. On Lonneker's Beach, the distribution of L* values among the beetles sampled was actually bimodal. On this small beach, there was an area of intensely black sand in the zone occupied by the beetles, but most of the rest was covered with light golden sand. These results are interpreted as evidence that the variability of colour of Chaerodes beetles has the effect of populations being able to match the colour of the sand of their home beaches, presumably as a consequence of the differential survival of individuals.     

广东硇洲岛的瓣鳃类

根据1999－2001年在广东硇洲岛海滨的岩石岩,砾石滩,泥沙滩,泥沙滩,沙滩,红树林区潮间带和近海区潮下带等各种生态环境采集到的瓣鳃类动物的整理鉴定,获得瓣鳃炎77种,分隶于24科44属,本文对其区系组成及分布特点进行了详细的论述。     

Taxonomic composition and distribution of the echinoderms associations in the littoral ecosystems from the Colombian Pacific

This paper examines published information and gray literature about taxonomy and ecology of echinoderm species of the Colombian Pacific Coast. Unpublished collection data of specimens kept in the Marine Sciences Museum of the University of Valle are also considered. Sixty-six species are found in coastal ecosystems and shallow bottoms of ten geographical, coastal and insular localities of the Pacific coast of Colombia. Main habitats having echinoderms are: rocky cliffs and shores, coral reefs, sand beaches, mud substrates, mangroves, and shallow bottoms of mud, sand, gravel and rocks. Regular Echinoidea and Asteroidea are the most diverse and abundant groups, mainly in subtidal rocky shallow bottoms and coral reefs. Ophiuroidea are abundant below rocky boulders. Irregular Echinoidea are abundant on sand beaches. The relatively high number of species shows that this geographical area presents a high diversity of echinoderms compared with other tropical shallow and littoral zones of the world. Rocky substrates and coral reefs are the ecosystems with the highest numbers of echinoderm species and individuals. A conservation status assessment is difficult because the lack of periodical sampling and few data about deep zones. In general, the species reported in the last 25 years, have not experimented important changes in their populations, although in some specific places, populations may decrease because human activities in coastal areas increase sedimentation rates change some rocky substrates to mud or sand.     

Influence of Land Use,Nutrients, and Geography on Microbial Communities and Fecal Indicator Abundance at Lake Michigan Beaches

Microbial communities within beach sand play a key role in nutrient cycling and are important to the nearshore ecosystem function. Escherichia coli and enterococci, two common indicators of fecal pollution, have been shown to persist in the beach sand, but little is known about how microbial community assemblages are related to these fecal indicator bacteria (FIB) reservoirs. We examined eight beaches across a geographic gradient and range of land use types and characterized the indigenous community structure in the water and the backshore, berm, and submerged sands. FIB were found at similar levels in sand at beaches adjacent to urban, forested, and agricultural land and in both the berm and backshore. However, there were striking differences in the berm and backshore microbial communities, even within the same beach, reflecting the very different environmental conditions in these beach zones in which FIB can survive. In contrast, the microbial communities in a particular beach zone were similar among beaches, including at beaches on opposite shores of Lake Michigan. The differences in the microbial communities that did exist within a beach zone correlated to nutrient levels, which varied among geographic locations. Total organic carbon and total phosphorus were higher in Wisconsin beach sand than in beach sand from Michigan. Within predominate genera, fine-scale sequence differences could be found that distinguished the populations from the two states, suggesting a biogeographic effect. This work demonstrates that microbial communities are reflective of environmental conditions at freshwater beaches and are able to provide useful information regarding long-term anthropogenic stress.     

Intertidal Benthic Invertebrates and Sediment Stability at the Mouth of Delaware Bay

From December 1970 to December 1972, the monthly species composition, density, species richness, and biomass of marine macroscopic invertebrates were quantitatively studied from a wave-protected, intertidal sand flat at the mouth of Delaware Bay. Considerable erosion, transportation, and deposition of sand occurred throughout the study period. The fauna was extremely flexible and resilient in its response to a gradient of considerable sediment mobility. This response was similar in scope to one recognized along the coast of California. Comparison of the local biota with other sand flats and beaches from Maine to South Carolina showed that (1). haustoriids were among the dominant species, (2). densities were roughly comparable, and (3). secondary species were similar. Based on the biological index value, three species contained 87.8% of the fauna from the Cape Henlopen tide flat. These species were the polychaete Scoloplos fragilis and the amphipod Neohaustorius biarticulatus, which were characteristic of sand bars, and the polychaete Heteromastus filiformis, which was more characteristic of troughs or depressions. Mean density varied considerably both monthly and annually with almost no cyclic repetition for any of the three species. There was evidence to indicate that specific habitat requirements of a few species can strongly affect the structure which emerges for a total fauna. Morphology, behavior, physiology, and reproductive strategy are aspects of biology which link dominant benthic species of intertidal sand beaches together.     

Green beach vegetation dynamics explained by embryo dune development

Sandy coastlines are dynamic environments with potential for biodiverse habitats, such as green beaches. Green beach vegetation can develop on nutrient-poor beaches landward from embryo dunes. It is characterised by low-dynamic coastal wetland habitat such as salt marshes and dune slacks. It has been hypothesised that the establishment of green beach vegetation is facilitated by the shelter provided by embryo dunes, however evidence is lacking.We explored the importance of geomorphology and soil conditions on the species richness and turnover of green beach vegetation over a time period of 10 years. We recorded 107 plots along 11 transects over a gradient from beach to dune on the island of Schiermonnikoog, the Netherlands. We characterised transect geomorphology at transect level and soil conditions and vegetation at plot level in 2006 and 2016.We found that the green beach vegetation was highly dynamic, total plant cover increased by 62% within 10 years. In 2006 beach width was an important factor in explaining species richness, with the highest number of species occurring on narrow beaches with a large volume of embryo dunes. In 2016, species richness was positively associated with the build-up of organic matter. Overall species richness declined relative to 2006 and was accompanied by an increase in elevation due to sand burial and the expansion of embryo dune volume.Our data suggests that geomorphology influenced the vegetation indirectly by affecting sand burial rate. Plant species richness declined less at sheltered conditions where sand burial was limited, allowing the build-up of organic matter. This indicates a time-dependent relationship between the development of embryo dunes and plant species richness: embryo dunes can be a source of shelter, thus increasing species richness, but can compete for space over time, lowering species richness again. Our results are relevant for engineering and management of biodiverse sandy shores.