Sandy Beach Environments Research Articles

An Approach to Assessing the Impact of Hurricane Matthew on Meiofaunal Communities in Sandy Beach Environments

ABSTRACTHurricanes are natural periodic events that disrupt marine ecosystems along their path, altering the distribution and abundance of organisms. In October 2016, Hurricane Matthew struck the Santa Marta region (Colombia) and impacted its coastal zone, yet there have been insufficient studies to measure its effects. The aim of this study was to assess the impact of Hurricane Matthew on the meiofaunal community in the region. To achieve this, sediment samples were collected from the intertidal zone of three beaches 5 days after the hurricane had passed. The results were compared with previous data collected in October 2014, on the abundance and diversity of taxonomic groups of intertidal meiofauna, as well as physicochemical variables such as granulometry, organic matter in sediments, salinity, and water temperature. Following Hurricane Matthew, the physicochemical variables showed changes due to the effect of the cyclonic surge in the coastal zone. The average organism abundance not only experienced a decline in both abundance and richness but also underwent changes in composition. Nematoda, originally the fourth most abundant group in 2014, became the most dominant taxon post‐hurricane. Conversely, the relative abundance of Copepoda decreased. The total number of recorded taxa was 13, which is close to the 15 previously reported. The ANOSIM and PERMANOVA tests confirmed differences in the meiofaunal community before and after Hurricane Matthew, with Tardigrada, Cnidaria, Ostracoda and Mollusca, being the main groups that contributed the most to the dissimilarity between periods. The environmental variables of organic matter and temperature best explained the structure of the meiofaunal community after the natural phenomenon. This study highlights the importance of meiofauna as a monitoring tool for beaches and the effects of environmental disturbances such as hurricanes, which are expected to become more common in coastal areas due to climate change.

Conceptualizing Controlling Factors for PFAS Salting Out in Groundwater Discharge Zones Along Sandy Beaches.

Understanding fate and transport processes for per- and poly-fluoroalkyl substances (PFAS) is critical for managing impacted sites. "PFAS Salting Out" in groundwater, defined herein, is an understudied process where PFAS in fresh groundwater mixes with saline groundwater near marine shorelines, which increases sorption of PFAS to aquifer solids. While sorption reduces PFAS mass discharge to marine surface water, the fraction that sorbs to beach sediments may be mobilized under future salinity changes. The objective of this study was to conceptually explore the potential for PFAS Salting Out in sandy beach environments and to perform a preliminary broad-scale characterization of sandy shoreline areas in the continental U.S. While no site-specific PFAS data were collected, our conceptual approach involved developing a multivariate regression model that assessed how tidal amplitude and freshwater submarine groundwater discharge affect the mixing of fresh and saline groundwater in sandy coastal aquifers. We then applied this model to 143 U.S. shoreline areas with sandy beaches (21% of total beaches in the USA), indirectly mapping potential salinity increases in shallow freshwater PFAS plumes as low (<10 ppt), medium (10-20 ppt), or high (>20 ppt) along groundwater flow paths before reaching the ocean. Higher potential salinity increases were observed in West Coast bays and the North Atlantic coastline, due to the combination of moderate to large tides and large fresh groundwater discharge rates, while lower increases occurred along the Gulf of Mexico and the southern Florida Atlantic coast. The salinity increases were used to estimate potential perfluorooctane sulfonic acid (PFOS) sorption in groundwater due to salting out processes. Low-category shorelines may see a 1- to 2.5-fold increase in sorption of PFOS, medium-category a 2.0- to 6.4-fold increase, and high-category a 3.8- to 25-fold increase in PFOS sorption. The analysis presented provides a first critical step in developing a large-scale approach to classify the PFAS Salting Out potential along shorelines and the limitations of the approach adopted highlights important areas for further research.

Comparative analysis of sandy beach and foredune geomorphic change measurements from Apple lidar and small-unoccupied aerial systems

Sandy beach and foredune environments are common throughout coastlines globally. Coastal landscapes are dynamic and vulnerable to water level fluctuations, storm events, and human disturbances. Standard methods for measuring geomorphic changes include small-unoccupied aircraft systems paired with structure-from-motion photogrammetry (sUAS-SfM), but this can be costly and logistically challenging. We evaluated the accuracy of Apple lidar in comparison to high precision sUAS-SfM and RTK-GPS to map sandy beach and foredune geomorphic change. Checkpoint elevations were measured via RTK-GPS and both the sUAS-SfM and Apple lidar surveyed elevations were compared against these checkpoints to evaluate the performance of both methods for measuring elevations. The sUAS-SfM elevation data were on average around 0.004 m above/below the checkpoint elevations while the Apple Lidar elevations were around 0.039 m. Apple lidar and sUAS-SfM-derived volumetric measurements and spatial patterns of erosion and accretion were compared to evaluate the Apple lidar’s ability to detect geomorphic change over time. The geomorphic changes documented from these two methods were similar though the Apple lidar appeared to capture finer-scale erosion and accretion patterns. Our findings indicate that the Apple lidar can capture sandy beach and foredune geomorphic changes rapidly and accurately, which can promote proactive and resilient coastal management.

Collembola biocenoses (Arthropoda: Hexapoda) in the archipelago of Fernando de Noronha, Brazil

The biota on oceanic islands commonly contains high percentage of endemic species, although their vulnerability is usually greater in relation to continental species. Here, we determined the composition, distribution and environmental factors influencing Collembola communities in three coastal environmental habitats of the Fernando de Noronha Archipelago, Brazil. In total, we sampled 20,308 collembolans belonging to 30 species. We report that the sandy beach environments studied harbor a single endemic specialist species (Isotogastrura mucrospatulata Palacios-Vargas, de Lima, & Zeppelini, 2013); environments of slope forest sites and top forests display a generalist fauna with wide distribution on the mainland. In most cases, abundance, richness and diversity did not significantly vary between site, coastal environmental habitat or moisture content levels. However, among the environmental factors, moisture content and litter layer depth were the most important ones structuring the collembolan communities of the archipelago in the Db-RDA analysis. Our results indicate that the beaches of the archipelago harbor completely different collembolan communities from the forests and because they harbor endemic species, and endemic collembolan species have been shown to be more sensitive to disturbance than non-endemics, we also suggest that Sandy Beaches and Slope Forests environments deserve attention in dedicated nature conservation policies as these often are either not soil-specific, or focused on soil physical properties rather than soil biodiversity.

Utility of an inexpensive near-infrared camera to quantify beach surface moisture

Surface moisture content is an essential factor that must be considered when studying aeolian sediment transport on a sandy beach. In recent years, near-infrared (NIR) remote sensing sensors have shown promise for obtaining accurate surface moisture data; however, prior studies utilized instruments with extreme costs. This study assesses the capability of an inexpensive NIR digital camera to measure surface moisture at two sandy beach environments – Tybee Island, Georgia and Pensacola Beach, Florida – that exhibit varying sediment hue characteristics. To account for temporal variations in solar atmospheric conditions, we normalized the raw sediment surface reflectance data against a white reflectance card and a sample of oven dry sand representative of each study site. This is a necessary step to account for solar atmospheric conditions. Calibration results illustrate that the NIR camera is capable of producing accurate representations of beach surface moisture; analyses from both study sites produced R2 values greater than 0.76 with error estimates at ±1–2% moisture. No statistical difference in calibration relationships were observed for data collected over multiple days and times of day. Calibration data for the reflectance card produced more robust relationships with smaller prediction errors than the oven dry sand analyses; however. Overall, this study illustrates that an inexpensive digital camera modified to record NIR radiation is capable of producing robust and accurate measurements of beach surface moisture.

Assessment of moisture content in sandy beach environments from multispectral satellite imagery

A framework for estimating moisture content from satellite-based multispectral imagery of sandy beaches was tested under various site conditions and sensors. It utilizes the reflectance of dry soil and an empirical factor c relating reflectance and moisture content for a specific sediment. Here, c was derived two ways: first, from in situ measurements of moisture content and average NIR image reflectance; and second, from laboratory-based measurements of moisture content and spectrometer reflectance. The proposed method was tested at four sandy beaches: Duck, North Carolina; and Cannon Beach, Ocean Cape, and Point Carrew, Yakutat, Alaska. Both measured and estimated moisture content profiles were impacted by site geomorphology. For profiles with uniform slopes, moisture contents ranged from 3.0% to 8.0% (zone 1) and from 8.0% to 23.0% (zone 2). Compared to field measurements, the moisture contents estimated using c calibrated from in situ and laboratory data resulted in percent error of 3.6%–44.7% and 2.7%–58.6%, respectively. The highest percent error occurred at the transition from zone 1 to zone 2. Generally, moisture contents were overestimated in zone 1 and underestimated in zone 2, but followed the expected trends based on field measurements. When estimated moisture contents in zone 1 exceeded 10%, surface roughness, debris, geomorphology, and weather conditions were considered.

Plasticity of Foraging Strategies Adopted by the Painted Ghost Crab, Ocypode gaudichaudii, in Response to in situ Food Resource Manipulation Experiments.

The feeding strategies of Ocypode gaudichaudii at two sandy beaches, Culebra Beach (CB) and Playa Venao (PV) in Panama, were studied via three experiments. Two separate manipulative in situ experiments were conducted to determine how the densities of food resources and the size of the supplemented food offered to the crabs can affect their diet and food handling behavior. The third experiment, a transplantation study, was also conducted to determine the plasticity of the feeding behavior of the displaced crabs. In the first experiment, freshly-emerged crabs showed different feeding modes when washed-sediment was seeded with different densities of diatoms and rove beetles, which suggests that they are optimal foragers. Crabs hoarded food in the second experiment when food augmentation was performed, in which small and large food pellets were placed around the burrows at the beginning and end of the crabs' feeding cycle. All freshly-emerged crabs from both sites foraged on the small pellets outside their burrows and did not cache food; when pellets were provided at the end of the feeding cycle, crabs from CB fed on some of the small pellets and returned to their burrows with the uneaten pellets left on the surface, whereas crabs at PV picked up all the small food pellets and transferred them into their burrows over several trips before plugging their burrow entrances. Only the crabs from PV carried the large food pellets supplemented at the start and end of the feeding cycle into their burrows. In contrast, the crabs at CB often left behind the partially-eaten pellets on the sand surface, probably due to the increased risk of predation associated with the prolonged handling time of the large food pellets. Excavation of the burrows of the crabs that hoarded food showed that all the pellets were deposited at the bend of the burrows, indicating that they were not consumed immediately. Crabs that fed in droves at PV stopped droving and foraged around their burrows after being transplanted to CB. This is the first documentation of food hoarding in a sandy beach macroinvertebrate at a resource-impoverished habitat. The plasticity of feeding strategies adopted by the painted ghost crab in response to different densities of food resources in the habitat could be an adaptation to the dynamic sandy beach environment.

Ichthyofauna of sandy beaches along the Acre river, Brazil

Abstract: Despite increasing efforts in recent years to catalog the fish diversity of Amazonian rivers, many regions are still under-sampled, and sandy beach environments are particularly poorly understood. The present study focused on a 300 km stretch of the Acre river, in the southwestern Amazon basin, where we sampled 30 sandy beaches separated by a mean interval of 10 km. We collected 15,329 fish representing 80 species, 26 families, and nine orders. The Characiformes were the most abundant order, providing 88.24% of the individuals collected, followed by the Siluriformes, with 10.03%, while the Siluriformes had the highest species richness, with 37 species (45.0%), followed by the Characiformes, with 30 (37.5%). The most abundant species were the characiforms Knodus orteguasae and Creagruto barrigai. Reliable data on a region’s biota is fundamental for the evaluation of patterns of biodiversity, and the occurrence and management of threatened species. As fish are directly affected by pollutants and the degradation of aquatic environments, further research in areas that are still poorly sampled will be essential for the elaboration of effective conservation strategies.

Effects of environmentally relevant concentrations of microplastic fibers on Pacific mole crab (Emerita analoga) mortality and reproduction

AbstractMicroplastics are ubiquitous in marine systems; however, knowledge of the effects of these particles on marine fauna is limited. Ocean‐borne plastic debris accumulates in littoral ecosystems worldwide, and invertebrate infauna inhabiting these systems can ingest small plastic particles and fibers, mistaking them for food. We examined the effect of microplastic fibers on physiological and reproductive outcomes in a nearshore organism by exposing Pacific mole crabs (Emerita analoga) to environmentally relevant concentrations of microsized polypropylene rope fibers. We compared adult gravid female crab mortality, reproductive success, and embryonic developmental rates between microfiber‐exposed and control crabs. Pacific mole crabs exposed to polypropylene rope had increased adult crab mortality, and decreased retention of egg clutches, causing variability in embryonic development rates. These effects of microplastic ingestion on a nearshore prey species have implications for predators such as surf perf and shore birds, as plastic use, and resultant microplastic presence in nearshore environments increases. Microplastics are ubiquitous in marine and sandy beach environments, posing a significant threat to the marine organisms that reside therein. The most predominant classification of microplastics found have been microfibers. Although a number of biological effects of microplastics have been measured, with documented effects on growth, little research has examined how microplastic fibers affect reproductive output and subsequent development of offspring. We examined the effects of exposure to microfibers on adult mortality, reproductive output, and embryonic development of the filter feeding Pacific mole crab (E. analoga), a dominant infaunal organism on sandy beaches. We demonstrate the effects of microplastic ingestion on mole crab mortality and embryonic development, filling a gap in the current knowledge on the impact of microplastics.

Between the tides: Modelling the elevation of Australia's exposed intertidal zone at continental scale

The intertidal zone represents a critical transition between marine and terrestrial ecosystems, supporting a complex mosaic of highly productive and biologically diverse habitats. However, our understanding of these important coastal environments is limited by a lack of spatially consistent topographic data, which can be extremely challenging and costly to obtain at continental-scale. Satellite remote sensing represents an important resource for monitoring extensive coastal zones. Previous approaches to modelling the elevation of the intertidal zone using earth observation (EO) data have been restricted to small study regions or have relied on manual image interpretation, thus limiting their ability to be applied consistently over large geographic extents. In this study, we present an automated open-source approach to generate satellite-derived elevation data for over 15,387 km2 of intertidal terrain across the entire Australian coastline. Our approach combines global tidal modelling with a 30-year time series archive of spatially and spectrally calibrated Landsat satellite data managed within the Digital Earth Australia (DEA) platform. The resulting National Intertidal Digital Elevation Model (NIDEM) dataset provides an unprecedented three-dimensional representation of Australia's vast exposed intertidal zone at 25 m spatial resolution. We validate our model against LiDAR, RTK GPS and multibeam bathymetry datasets, finding that modelled elevations are highly accurate across sandy beach (±0.41 m RMSE) and tidal flat environments (±0.39 m RMSE). Model performance was least accurate (±2.98 m RMSE) within rocky shores and reefs and other complex coastal environments with extreme and variable tidal regimes. We discuss key challenges associated with modelling intertidal elevation including tidal model performance and biased observations from sun-synchronous satellites, and suggest future directions to improve the accuracy and utility of continental-scale intertidal elevation modelling. Our model can be applied to tidally-influenced coastal environments globally, addressing a key gap between the availability of sub-tidal bathymetry and terrestrial elevation data.

The seaweed fly (Coelopidae) can facilitate environmental survival and transmission of E. coli O157 at sandy beaches

The sustainable management of recreational beaches is essential for minimising risk of human exposure to microbial pathogens whilst simultaneously maintaining valuable ecosystem services. Decaying seaweed on public beaches is gaining recognition as a substrate for microbial contamination, and is a potentially significant reservoir for human pathogens in close proximity to beach users. Closely associated with beds of decaying seaweed are dense populations of the seaweed fly (Coelopidae), which could influence the spatio-temporal fate of seaweed-associated human pathogens within beach environments. Replicated mesocosms containing seaweed inoculated with a bioluminescent strain of the zoonotic pathogen E. coli O157:H7, were used to determine the effects of two seaweed flies, Coelopa frigida and C. pilipes, on E. coli O157:H7 survival dynamics. Multiple generations of seaweed flies and their larvae significantly enhanced persistence of E. coli O157:H7 in simulated wrack habitats, demonstrating that both female and male C. frigida flies are capable of transferring E. coli O157:H7 between individual wrack beds and into the sand. Adult fly faeces can contain significant concentrations of E. coli O157:H7, which suggests they are capable of acting as biological vectors and bridge hosts between wrack habitats and other seaweed fly populations, and facilitate the persistence and dispersal of E. coli O157:H7 in sandy beach environments. This study provides the first evidence that seaweed fly populations inhabiting natural wrack beds contaminated with the human pathogen E. coli O157:H7 have the capacity to amplify the hazard source, and therefore potential transmission risk, to beach users exposed to seaweed and sand in the intertidal zone. The risk to public health from seaweed flies and decaying wrack beds is usually limited by human avoidance behaviour; however, seaweed fly migration and nuisance inland plagues in urban areas could increase human exposure routes beyond the beach environment.

Pigment compositions are linked to the habitat types in dinoflagellates

Compared to planktonic species, there is little known about the ecology, physiology, and existence of benthic dinoflagellates living in sandy beach or seafloor environments. In a previous study, we discovered 13(2),17(3)-cyclopheophorbide a enol (cPPB-aE) from sand-dwelling benthic dinoflagellates. This enol had never been detected in phytoplankton despite the fact that it is a chlorophyll a catabolite. We speculated from this discovery that habitat selection might be linked to pigment compositions in dinoflagellates. To test the hypothesis of habitat selection linking to pigment compositions, we conducted extensive analysis of pigments with high performance liquid chromatography (HPLC) for 40 species using 45 strains of dinoflagellates including three habitat types; sand-dwelling benthic forms, tidal pool inhabitants and planktonic species. The 40 dinoflagellates are also able to be distinguished into two types based on their chloroplast origins; red alga-derived secondary chloroplasts and diatom-derived tertiary ones. By plotting the pigments profiles onto three habitats, we noticed that twelve pigments including cPPB-aE were found to occur only in benthic sand-dwelling species of red alga-derived type. The similar tendency was also observed in dinoflagellates with diatom-derived chloroplasts, i.e. additional sixteen pigments including chl c 3 were found only in sand-dwelling forms. This is the first report of the occurrence of chl c 3 in dinoflagellates with diatom-derived chloroplasts. These results clarify that far greater diversity of pigments are produced by the dinoflagellates living in sand regardless of chloroplast types relative to those of planktonic and tidal pool forms. Dinoflagellates seem to produce a part of their pigments in response to their habitats.

海南海岸青皮林繁殖物候特征

PDF HTML阅读 XML下载 导出引用 引用提醒 海南海岸青皮林繁殖物候特征 DOI: 10.5846/stxb201304010572 作者: 作者单位: 热带动植物生态学省部共建教育部重点实验室 海南师范大学生命科学学院,热带动植物生态学省部共建教育部重点实验室 海南师范大学生命科学学院,热带动植物生态学省部共建教育部重点实验室 海南师范大学生命科学学院,热带动植物生态学省部共建教育部重点实验室 海南师范大学生命科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目(31060092) Reproductive phenological characteristics of hainan coastal Vatica mangachapoi forest Author: Affiliation: Ministry of Education Key Laboratory for Tropical Animal and Plant Ecology,College of Life Sciences,Hainan Normal University,,,Ministry of Education Key Laboratory for Tropical Animal and Plant Ecology,College of Life Sciences,Hainan Normal University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:石梅湾海岸青皮林是海南岛重要的天然海防林及旅游区风景林,对其繁殖物候的研究有助于揭示青皮在贫瘠海岸沙滩成功定居及繁殖的生物学特性。采用种群、个体定位和小枝标记相结合的方法,连续3a对其开花物候进行观测,结果表明:青皮个体繁殖物候期约为101d,小枝平均花蕾数为133.3个,幼果坐果率为42.4%,结实率为4.4%;青皮种群为1a连续开花型,但集中开花模式明显,有2个高峰期且花量多,非集中开花期花量很少;个体间及个体中小枝间开花存在一定的不同步性;开花及种子丰年现象明显,歉年花量及种子雨量很少;开花物候期前1个月的降雨量对开花物候期无显著影响,但3、4月份平均气温分别高于24℃和26.4℃,开花期提前明显,低于此温度开花期推迟相对缓慢,即物候期的提前与推迟对温度的上升与下降的响应是非线性的。 Abstract:Vatica mangachapoi belongs to the Vatica Linn genus of the Dipterocarpaceae family and was once extensively distributed over Hainan Island, from low to medium altitude. It is now an endangered species and a Ⅱ grade key protected plant in China,due to over cutting for its valuable wood. It exhibits several excellent characteristics, such as strong adaptability to growth conditions, especially having the ability to colonize poor sandy beach or rocky areas, eventually easily forming a single Vatica mangachapoi dominant community due to strong natural regeneration, ability to compete and strong wind resistance. Therefore, it is no surprise that the Vatica mangachapoi forest is distributed over the sandy beach of Shimei Bay, Hainan Island, China, and is the only patch of natural forest growing on sandy beach environments in Hainan Island. Now it has become a significant model forest for the regeneration and transformation of manmade shelterbelts and as a scenic forest in the Shimei Bay tourism area in Hainan Island. The reproductive phenology study of Vatica mangachapoi forest will help to reveal the biological characteristics of Vatica mangachapoi that allows it to successfully settle and reproduce in arid coastal beach environments. Our primary objectives were to: (1) Investigate the biological characteristics of Vatica mangachapoi reproductive phenology, and (2) analyze the response of Vatica mangachapoi reproductive phenology to temperature changes in the coastal Vatica mangachapoi forest of Shimei Bay, so as to supply a theoretical basis for the protection and management of the Vatica mangachapoi forest and to predict Vatica mangachapoi fluorescence, formation of red seed calyx, seed rain dispersal periods, etc. The reproductive phonological observations were conducted on the three levels of population, individuals and twigs continuously for three years. Thirty individual Vatica mangachapoi were selected based on systematic sampling and sixty twigs were labeled with two twigs per individual. 3a meteorological data were obtained from Hainan meteorological Bureau to analyze the interannual phenophase variation. The results showed that the average reproductive phenophase, numbers of buds in a twig, seed setting rate of young seeds, and seed setting rate of mature seeds of Vatica mangachapoi were 101d, 133.3, 42.4% and 4.4%, respectively. The population of Vatica mangachapoi was of 1a continuous flowering type, but exhibited the obvious concentrated florescence with a bimodal. There were many flowers in the period of concentrated flowering and few in the non-concentrated flowering period; the flowering time exhibited an obvious asynchronicity among individuals and between twigs on each individual. There was a significant difference in the numbers of flowers and seeds between the harvest and lean years; the rainfall in one month before buds occurred had no obvious effect on the flowering phenophase, but the monthly average temperature did have an obvious effect. When the monthly average temperature in March and April in the month before buds appeared was higher than 24℃ and 26.4℃, respectively, the flowering phenophase progression was obvious, but the flowering phenophase was delayed when the temperature was lower. These results demonstrate that the response of the flowering phenophase progression and delay based on the rise and fall in temperature was nonlinear, and the bimodal phenophase and seed dispersal period were a benefit to successful Vatica mangachapoi seed germination and growth on the seasonal dry sandy beach. 参考文献 相似文献 引证文献

Sandy reefs of Sabellaria wilsoni (Polychaeta: Sabellariidae) as ecosystem engineers for meiofauna in the Amazon coastal region, Brazil

The aim of the present study was to evaluate the effects of ecosystem engineering caused by reefs of Sabellaria wilsoni (Polychaeta: Sabellariidae) on the meiofauna community of Algodoal Island, in the state of Amazonas, Brazil. Two types of sandy reefs (ball and platform structures) as well as the surrounding sandy sediments of two distinct beaches (low tide terrace and dissipative) were studied. Sampling was carried out at each location in June (rainy season) and December (dry season) 2008, along two profiles perpendicular to the coastal line. A total of 22 taxa of meiofauna were found, with average density of 1,774.2 ind/10 cm2. Nematoda was the dominant taxon in all seasons and at all locations. ANOVA testing showed that, of the univariate parameters, only richness was significantly different between environments. PERMANOVA highlighted significant differences in the interaction between the environmental factors, as well as between types of reefs and beaches. Changes in structural and abiotic factors led to higher diversity in the reefs, indicating the importance of S. wilsoni as an ecosystem engineer in this Amazonian estuarine sandy beach environment.

Mollusc life and death assemblages on a tropical rocky shore as proxies for the taphonomic loss in a fossil counterpart

Comparison of a modern rocky shore mollusc life assemblage from Thailand with the associated death assemblage, and interpretation of the fossilization potential of the latter, are used to investigate the fidelity in reconstruction of ancient analogues. The fauna from the death assemblage represents species from the rocky shore and the associated sandy pocket beaches, and only a few exotic species from other, completely different habitats are present. The environmental fidelity between the life and death assemblage is thus high, with the majority of species from the death assemblage representing the intertidal to shallow subtidal rocky shore environment, from which the life assemblage was sampled, and the associated sandy beach environment. The life assemblage should in principle have a high fossilization potential because only two out of 67 species are without a calcareous shell, but it actually has a lower taxonomic agreement to the death assemblage than found in previous published studies. Rocky shore life and death assemblages thus appear to show lower taxonomic agreement compared to muddy or sandy shelf assemblages due to the mix after death with the sandy beach assemblage. A hypothetical fossil assemblage is constructed from the death assemblage, assuming that only calcitic and infaunal aragonitic species have a chance to be preserved in the geological record. The hypothetical fossil assemblage is not taxonomically similar to the life assemblage but shows high environmental fidelity to the rocky shore and sandy pocket beach. In terms of species richness the life assemblage is dominated by epifaunal, herbivorous gastropods, whereas the hypothetical fossil assemblage is dominated by infaunal, suspension feeding bivalves. The hypothetical fossil assemblage thus represents a faunal community from an intertidal to shallow subtidal rocky shore environment and the associated sandy pocket beach environment, and shows marked differences in faunal composition, modes of life, richness and density patterns compared to the rocky shore life assemblage due to the mix between the two associated habitats. This serves to illustrate the significance of integrating the taphonomic influence on a fossil faunal assemblage before attempting to reconstruct an ancient ecosystem and environment.

Secondary production of sandy beach macrofauna: An evaluation of predictive models

During the last three decades, several predictive models have been developed to estimate the somatic production of macroinvertebrates. Although the models have been evaluated for their ability to assess the production of macrobenthos in different marine ecosystems, these approaches have not been applied specifically to sandy beach macrofauna and may not be directly applicable to this transitional environment. Hence, in this study, a broad literature review of sandy beach macrofauna production was conducted and estimates obtained with cohort-based and size-based methods were collected. The performance of nine models in estimating the production of individual populations from the sandy beach environment, evaluated for all taxonomic groups combined and for individual groups separately, was assessed, comparing the production predicted by the models to the estimates obtained from the literature (observed production). Most of the models overestimated population production compared to observed production estimates, whether for all populations combined or more specific taxonomic groups. However, estimates by two models developed by Cusson and Bourget provided best fits to measured production, and thus represent the best alternatives to the cohort-based and size-based methods in this habitat. The consistent performance of one of these Cusson and Bourget models, which was developed for the macrobenthos of sandy substrate habitats (C&BSS), shows that the performance of a model does not depend on whether it was developed for a specific taxonomic group. Moreover, since some widely used models (e.g., the Robertson model) show very different responses when applied to the macrofauna of different marine environments (e.g., sandy beaches and estuaries), prior evaluation of these models is essential.

Environmental effects on the structure of polychaete feeding guilds on the beaches of Sepetiba Bay, south-eastern Brazil

Several studies have been conducted to explain patterns of the abundance, richness and diversity of sandy-beach macrofauna; however, such analyses have ignored the overall functional structure of macrofauna communities. Few studies have examined polychaete feeding guilds on sandy beach environments. To examine the effects of environmental factors on polychaete feeding guilds on sandy beaches, 12 sandy beaches from five islands in Sepetiba Bay were sampled. A total of 24 polychaete morphospecies, grouped among 21 families, were identified in these sandy beaches. The polychaete species were classified into 10 feeding guilds, and the SDT guild (suspended-deposit feeders, discretely motile, with tentacles) was the most abundant feeding guild, with 34.2% of total number of organisms. The highest trophic importance index and index of trophic diversity values were recorded on the sheltered beaches. A canonical correspondence analysis showed that the exposure rate, beach length, and grain size of the beach sediment significantly affected the polychaete feeding guild distribution and abundance. We can conclude that sheltered beaches have a higher diversity of feeding guilds than exposed beaches and that the biological descriptors of the feeding guilds are directly associated with the grain size of the sediment.

Responses of microbial community from northern Gulf of Mexico sandy sediments following exposure to deepwater horizon crude oil

In the present study, microbial community responses to exposure to unweathered Macondo Well crude oil and conventional diesel in a sandy beach environment were determined. Biodegradation was assessed in mesocosm experiments with differing fuel amounts (2,000 and 4,000 mg/kg) and with or without inorganic nutrient amendment. Carbon dioxide production was measured daily for 42 d. Aerobic alkane, total hydrocarbon, and polycyclic aromatic hydrocarbon (PAH) degraders were enumerated in treated and control mesocosms and changes in their abundances were measured weekly. Hydrocarbon mineralization occurred in all treatments. In the inorganic nutrient-amended treatments, the degradation rates were 2.31 and 2.00 times greater in the 2,000 mg/kg diesel and crude oil treatments, respectively, and 3.52 (diesel) and 4.14 (crude) times higher for the fuel types at the 4,000 mg/kg fuel concentrations compared to unamended treatments. Microbial lag phases were short (<3 d) and alkane and total hydrocarbon degrader numbers increased by five orders of magnitude compared to the uncontaminated treatments within 7 d in most treatments. Hydrocarbon degrader numbers in diesel and in crude oil treatments were similar; however, the PAH degraders were more abundant in the crude oil relative to diesel treatment. These findings indicate that hydrocarbon degradation by extant microbial populations in the northern Gulf of Mexico sandy beach environments can be stimulated and enhanced by inorganic nutrient addition.

Seasonal variation of bivalve larvae on an exposed sandy beach on Kashima-nada: Tips for the sandy beach recruitment process

Bivalves are often the dominant macrobenthos species in exposed sandy beach environments. However, our understanding of their recruitment processes before post-settlement stages on sandy beaches with highly energetic environments is incomplete. To clarify the characteristics of the free-swimming planktonic stage that affects recruitment efficiency in sandy shore ecosystems, we investigated the temporal (weekly–biweekly) variation of bivalve planktonic larval concentration coupled with oceanographic conditions on an exposed sandy shore on the sea of Kashima-nada, Japan, from summer 2003 to autumn 2005. Larvae were observed throughout the year, but the surge of larval concentration composed of sandy beach and sessile bivalves occurred most prominently in summer, from August to September. The peak concentration of larvae during this season was more than 1000 times higher than in other seasons. The larval concentration was positively correlated with water temperature and northward wind velocity and negatively correlated with each of the nutrient concentrations. On the other hand, chlorophyll a concentration and salinity seemed to have little effect on the larval concentration. Based on this fundamental knowledge, further investigations about planktonic larvae in sandy beaches are needed.

Testing the Habitat Safety Hypothesis with behavioural field experiments: amphipod orientation on sandy beaches with contrasting morphodynamics

Understanding behavioural adaptations in sandy beach macrofauna has been a major step in theoretical development of sandy beach ecology. In particular, behavioural studies in supra- littoral amphipods have been useful in understanding macrofaunal responses and adaptations to environmental changes in these dynamic ecosystems. The predictions of the Habitat Safety Hypo- thesis (HSH) were tested for the first time on Atlantorchestoidea brasiliensis through orientation experiments carried out on 2 sandy beaches, one dissipative and the other reflective. Orientation pat- terns of A. brasiliensis followed the trend predicted by the HSH: even though sandhoppers oriented seawards on both beaches using a sun compass, the orientation on the reflective beach was more pre- cise than on the dissipative one. Thus, stability conditions in the supralittoral zone of the reflective beach favoured a higher precision of the sun compass. The precision of seawards orientation on the dissipative beach increased when landscape references were added to the sun compass mechanism. The response to an unexpected object was also experimentally tested by use of a visual pattern, and a higher individual variability in the orientation of the reflective beach population was found. Thus, orientation strategies in sandy beach environments seem to respond to the stability of the supralit- toral zone, widening the general pattern predicted by the HSH for the supralittoral fauna to the behavioural traits of the population.