Complex, dynamic combination of physical, chemical and nutritional variables controls spatio-temporal variation of sandy beach community structure

Sandy beach ecological theory states that physical features of the beach control macrobenthic community structure on all but the most dissipative beaches. However, few studies have simultaneously evaluated the relative importance of physical, chemical and biological factors as potential explanatory variables for meso-scale spatio-temporal patterns of intertidal community structure in these systems. Here, we investigate macroinfaunal community structure of a micro-tidal sandy beach that is located on an oligotrophic subtropical coast and is influenced by seasonal estuarine input. We repeatedly sampled biological and environmental variables at a series of beach transects arranged at increasing distances from the estuary mouth. Sampling took place over a period of five months, corresponding with the transition between the dry and wet season. This allowed assessment of biological-physical relationships across chemical and nutritional gradients associated with a range of estuarine inputs. Physical, chemical, and biological response variables, as well as measures of community structure, showed significant spatio-temporal patterns. In general, bivariate relationships between biological and environmental variables were rare and weak. However, multivariate correlation approaches identified a variety of environmental variables (i.e., sampling session, the C∶N ratio of particulate organic matter, dissolved inorganic nutrient concentrations, various size fractions of photopigment concentrations, salinity and, to a lesser extent, beach width and sediment kurtosis) that either alone or combined provided significant explanatory power for spatio-temporal patterns of macroinfaunal community structure. Overall, these results showed that the macrobenthic community on Mtunzini Beach was not structured primarily by physical factors, but instead by a complex and dynamic blend of nutritional, chemical and physical drivers. This emphasises the need to recognise ocean-exposed sandy beaches as functional ecosystems in their own right.     

Biotic interactions drive species occurrence and richness in dynamic beach environments

Biotic interactions are predicted to have the strongest influence on species assemblages in extreme environments. We therefore test the hypothesis that in abiotically-severe beaches plant–plant interactions, specifically facilitation, are important relative to abiotic conditions. This hypothesis is tested by assessing the influence of dominant vascular plant species on the fine-scale occurrence and richness of vascular and cryptogam species using a unique dataset of boreal beaches along the Finnish Baltic Sea, characterized by strong post-glacial land uplift and large environmental gradients. We studied three different levels of vegetation patterns across a broad geographical scale; individual species, functional groups and the entire community. Results showed that dominant vascular species strongly drive species occurrence and richness in dynamic beach environments, with some species having an influence similar to that of key abiotic variables. In contrast to expectations, facilitative effects did not dominate in these harsh environments. Instead, the outcomes of biotic interactions were species-specific, and also differed between vascular and cryptogam species, with the former group most strongly influenced by a pioneer species and the latter by a late succession generalist. Our study highlights the importance of incorporating biotic interaction effects into models of multiple vegetation properties and cautions against overly simplistic generalizations to describe relatively idiosyncratic interaction effects.     

Species richness at the guild level: effects of species pool and local environmental conditions on stream macroinvertebrate communities

1.?A fundamental question in ecology is which factors determine species richness. Here, we studied the relative importance of regional species pool and local environmental characteristics in determining local species richness (LSR). Typically, this question has been studied using whole communities or a certain taxonomic group, although including species with widely varying biological traits in the same analysis may hinder the detection of ecologically meaningful patterns. 2.?We studied the question above for whole stream macroinvertebrate community and within functional feeding guilds. We defined the local scale as a riffle site and the regional scale (i.e. representing the regional species pool) as a stream. Such intermediate-sized regional scale is rarely studied in this context. 3.?We sampled altogether 100 sites, ten riffles (local scale) in each of ten streams (regional scale). We used the local-regional richness regression plots to study the overall effect of regional species pool on LSR. Variation partitioning was used to determine the relative importance of regional species pool and local environmental conditions for species richness. 4.?The local-regional richness relationship was mainly linear, suggesting strong species pool effects. Only one guild showed some signs of curvilinearity. However, variation partitioning showed that local environmental characteristics accounted for a larger fraction of variance in LSR than regional species pool. Also, the relative importance of the fractions differed between the whole community and guilds, as well as among guilds. 5.?This study indicates that the importance of the local and regional processes may vary depending on feeding guild and trophic level. We conclude that both the size of the regional species pool and local habitat characteristics are important in determining LSR of stream macroinvertebrates. Our results are in agreement with recent large-scale studies conducted in highly different study systems and complement the previous findings by showing that the interplay of regional and local factors is also important at intermediate regional scales.     

Communities in high definition: Spatial and environmental factors shape the micro-distribution of aquatic invertebrates

1. According to metacommunity theories, the structure of natural communities is the result of both environmental filtering and spatial processes, with their relative importance depending on factors including local habitat characteristics, functional features of organisms, and the spatial scale considered. However, few studies have explored environmental and spatial processes in riverine systems at local scales, explicitly incorporating spatial coordinates into multi-taxa distribution models. To address this gap, we conducted a small-scale study to discriminate between abiotic and biotic factors affecting the distribution of aquatic macroinvertebrates, applying metacommunity concepts.
2. We studied a mountain section in each of three perennial streams within the Po River Basin (northern Italy). We sampled macroinvertebrates both in summer and winter, using specific in situ 50-point random sampling grids. Environmental factors, including benthic organic matter (BOM), flow velocity, water depth, and substrate were recorded together with spatial coordinates for each sampling point. The relationships between community metrics (taxon richness, abundance, biomass, biomass–abundance ratio, and functional feeding groups) and explanatory variables (environmental and spatial) were assessed using generalised additive models. The influence of the explanatory variables on community structure was analysed with joint species distribution models.
3. Environmental variables—primarily BOM—were the main drivers affecting community metrics, whereas the effects of spatial variables varied among metrics, streams, and seasons. During summer, community structure was strongly affected by BOM and spatial position within the riverbed, the latter probably being a proxy for mass effects mediated by biotic and stochastic processes. In contrast, community structure was mainly shaped by hydraulic variables in winter.
4. Using macroinvertebrate communities as a model group, our results demonstrate that metacommunity concepts can explain small-scale variability in community structure. We found that both environmental filtering and biotic processes shape local communities, with the strength of these drivers depending on the season. These insights provide baseline knowledge that informs our understanding of ecological responses to environmental variability in contexts including restoration ecology, habitat suitability modelling, and biomonitoring.

     

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.     

Characterizing macroinvertebrate communities across China: Large-scale implementation of a self-organizing map

Understanding the geographical patterns and divisions of communities is a fundamental step in achieving the sustainable management of ecosystems, especially in deteriorating global and local environments. The idea of geographical division has been applied on all continents but Antarctica, but it has never been rigorously tested for stream ecosystems in China, leaving a gap in knowledge for many basic and applied research questions regarding, for example, diversity patterns, conservation issues or climate change effects. To fill this gap, we aimed to (1) evaluate the geographical divisions of the macroinvertebrate communities in Chinese streams using the self-organizing map (SOM) method and (2) to characterize the distribution patterns in relation to different environmental variables. Macroinvertebrates were collected from 57 relatively clean stream sites covering a south-north gradient along the boundary of the geographic ladder (or altitudinal divide) in China. SOM was used to analyze large-scale biogeographical divisions of the macroinvertebrate communities. The sampling sites were divided into six clusters, distinguishing the samples from northern, central, and southern China. This pattern was also reflected by biotic metrics (abundance, biomass, taxa and sum of Ephemeroptera, Plecoptera, and Trichoptera richness, and diversity). The gradient of environmental variables, particularly water quality variables, was similar between the clusters, with the exceptions of two clusters from southwestern China when considering altitude and one cluster from northern China when considering conductivity and TN. The different clusters from the SOM were associated with indicator species, with clean-water adapted species dominating in southwestern China and pollution tolerant species in northern China. However, there were no significant correlations between environmental variables and biotic metrics. The overall combination of environmental variables and organism data suggests that spatial variation was the main predictor determining the composition of the macroinvertebrate communities on a large-scale, and the trained SOM appeared to be efficient at classifying streams on a broad geographic scale.     

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.     

Influence of environmental variables on macroinvertebrate community structure in Lianhuan Lake

The structural characteristics of the macroinvertebrate community can effectively reflect the health status of lake ecosystems and the quality of the lake ecological environment. It is therefore important to identify the limiting factors of macroinvertebrate community structure for the maintenance of lake ecosystem health. In this study, the community composition of macroinvertebrate assemblages and their relationships with environmental variables were investigated in 13 small lakes within Lianhuan Lake in northern China. A self‐organizing map and K‐means clustering analysis grouped the macroinvertebrate communities into five groups, and the indicator species reflected the environmental characteristics of each group. Principal component analysis indicated that the classification of the macroinvertebrate communities was affected by environmental variables. The Kruskal–Wallis test results showed that environmental variables (pH, total phosphorus, nitrate, water temperature, dissolved oxygen, conductivity, permanganate index, and ammonium) had a significant effect on the classification of the macroinvertebrate communities. Redundancy analysis showed that mollusks were significantly negatively correlated with pH and chlorophyll a, while annelids and aquatic insects were significantly positively correlated with chlorophyll a and dissolved oxygen. Spearman correlation analysis showed that the species richness and Shannon''s diversity of macroinvertebrates were significantly negatively correlated with total phosphorus, while the biomass of macroinvertebrates was significantly negatively correlated with pH. High alkalinity and lake eutrophication have a serious impact on the macroinvertebrate community. Human disturbances, such as industrial and agricultural runoff, negatively impact the ecological environment and affect macroinvertebrate community structure. Thus, macroinvertebrate community structure should be improved by enhancing the ecological environment and controlling environmental pollution at a watershed scale.     

The potential contribution of vegetation ecology to biodiversity research

The contribution of vegetation ecology to the study of biodiversity depends on better communication between the different research paradigms in ecology. Recent developments in vegetation theory and associated statistical modelling techniques are reviewed for their relevance to biodiversity. Species composition and collective properties such as species richness vary as a continuum in a multi-dimensional environmental space; a concept which needs to be incorporated into biodiversity studies. Different kinds of environmental gradients can be recognised and species responses to them vary. Species response curves of eucalypts to an environmental gradient of mean annual temperature have been shown to exhibit a particular pattern of skewed response curves. Generalised linear modelling (GLM) and generalised additive modelling (GAM) techniques are important tools for biodiversity studies. They have successfully distinguished the contribution of environmental (climatic) and spatial (history and species dispersal ability) variables in determining forest tree composition in New Zealand. Species richness studies are examined at global, regional and local scales. At all scales, direct and resource environmental gradients need to be incorporated into the analysis rather than indirect gradients e.g. latitude which have no direct physiological influence on biota. Evidence indicates that species richness at the regional scale is sensitive to environment, confounding current studies on local/regional species richness relationships. Plant community experiments require designs based on environmental gradients rather than dependent biological properties such as productivity or species richness to avoid confounding the biotic components. Neglect of climatic and other environmental gradients and the concentration on the collective properties of species assemblages has limited recent biodiversity studies. Conservation evaluation could benefit from greater use of the continuum concepts and statistical modelling techniques of vegetation ecology. The future development of ecology will depend on testing the different assumptions of competing research paradigms and a more inclusive synthesis of ecological theory.     

The biogeography of abundant and rare bacterioplankton in the lakes and reservoirs of China

Bacteria play key roles in the ecology of both aquatic and terrestrial ecosystems; however, little is known about their diversity and biogeography, especially in the rare microbial biosphere of inland freshwater ecosystems. Here we investigated aspects of the community ecology and geographical distribution of abundant and rare bacterioplankton using high-throughput sequencing and examined the relative influence of local environmental variables and regional (spatial) factors on their geographical distribution patterns in 42 lakes and reservoirs across China. Our results showed that the geographical patterns of abundant and rare bacterial subcommunities were generally similar, and both of them showed a significant distance–decay relationship. This suggests that the rare bacterial biosphere is not a random assembly, as some authors have assumed, and that its distribution is most likely subject to the same ecological processes that control abundant taxa. However, we identified some differences between the abundant and rare groups as both groups of bacteria showed a significant positive relationship between sites occupancy and abundance, but the abundant bacteria exhibited a weaker distance–decay relationship than the rare bacteria. Our results implied that rare subcommunities were mostly governed by local environmental variables, whereas the abundant subcommunities were mainly affected by regional factors. In addition, both local and regional variables that were significantly related to the spatial variation of abundant bacterial community composition were different to those of rare ones, suggesting that abundant and rare bacteria may have discrepant ecological niches and may play different roles in natural ecosystems.     

Crustaceans as ecological indicators of metropolitan sandy beaches health

We have investigated how indices of beach health perform in predicting the abundances of the crustaceans Emerita brasiliensis and Atlantorchestoidea brasiliensis from 22 metropolitan beaches in the cities of Rio de Janeiro and Niterói. Urbanization, Recreation and Conservation indices were used to assess sandy beaches health. Grain size and beach slope were used as morphodynamics indicators. Diagram from the principal component analysis clearly separated beaches with different urbanization and conservation levels. Generalized additive models (GAM's) were adjusted for species abundance using the indices and morphodynamic parameters as explanatory variables. Lower abundances were predicted for beaches with high levels of urbanization, whereas predictions of higher abundances occurred on beaches with high conservation levels. Using theoretic inference we showed that the urbanization index was the most important predictor for abundance of A. brasiliensis and the conservation index was the most important predictor for E. brasiliensis, reflecting different responses by upper tidal and intertidal species. A. brasiliensis occupies the intermediate and upper beach zones and E. brasiliensis is a swash zone filter-feeder that is more abundant in pristine beaches. Both species are highly subject to the impact of bathers and coastal modification. Unexpected, the recreation index did not show a negative effect on abundance predictions. Urbanization and conservation indices can be suitable metrics to measure anthropogenic effects on macrobenthic species. Moreover, mole crabs and sandhoppers species can be easily monitored. Coastal urbanization is a global phenomenon and we used the diagram of urbanization and conservation levels to expose possible directions for management strategies of metropolitan sandy beaches.     

Relationships between stream macroinvertebrates and environmental variables at multiple spatial scales

1. Aquatic communities are structured by multiple forces, and identifying the driving factors over multispatial scales is an important research issue. The East Asian monsoon region is globally one of the richest environments in terms of biodiversity, and is undergoing rapid human development, yet the river ecosystems in this region have not been well studied. We applied a hierarchical framework to incorporate regional and local environmental effects on stream macroinvertebrate communities in this region. The knowledge gained is expected to improve the understanding of the importance of spatial scale on regional and local diversity in the East Asian monsoon region. 2. A national data set of benthic macroinvertebrates and environmental variables (geographical, land‐use, hydrological, substratum and physicochemical elements) in Korean rivers was used to determine the habitat preferences of macroinvertebrates. 3. Latitude, proportion of forest coverage, riffle habitat, silt substratum and temperature were the most important determinants for the ordinations of macroinvertebrate communities in each category evaluated by canonical correspondence analysis (CCA). The optimal habitats for stream macroinvertebrates are not the same for all species, and overall community metrics and abundance of sensitive species tended to be lower in open agricultural and urban streams than in forested streams. The sensitivity of mayflies and stoneflies to anthropogenic disturbances implicated them as good indicators to assess the effects of urban and agricultural activities. 4. A partial CCA was used to evaluate the relative importance of macrohabitat and microhabitat variables on community composition at three spatial scales (whole country, the large Han River basin and two small sub‐basins in the lowlands and highlands). The majority of community variation (17–22% for each environmental element) was explained by macrohabitat variables at the regional spatial scale. In contrast, large proportions (15–18%) were explained by microhabitat variables at the local spatial scale. 5. Our findings indicate that the relative importance of habitat scales should be determined by geographical size and that comprehensive understanding of multispatial scale patterns can be important for implementing sound biodiversity conservation programmes.     

Analysis of macrobenthic communities in Flanders,Belgium, using a stepwise input variable selection procedure with artificial neural networks

The effect of environmental conditions on river macrobenthic communities was studied using a dataset consisting of 343 sediment samples from unnavigable watercourses in Flanders, Belgium. Artificial neural network models were used to analyse the relation among river characteristics and macrobenthic communities. The dataset included presence or absence of macroinvertebrate taxa and 12 physicochemical and hydromorphological variables for each sampling site. The abiotic variables served as input for the artificial neural networks to predict the macrobenthic community. The effects of the input variables on model performance were assessed in order to identify the most diagnostic river characteristics for macrobenthic community composition. This was done by consecutively eliminating the least important variables and, when beneficial for model performance, adding previously removed ones again. This stepwise input variable selection procedure was tested not only on a model predicting the entire macrobenthic community, but also on three models, each predicting an individual taxon. Additionally, during each step of the stepwise leave-one-out procedure, a sensitivity analysis was performed to determine the response of the predicted macroinvertebrate taxa to the input variables applied. This research illustrated that a combination of input variable selection with sensitivity analyses can contribute to the development of reliable and ecologically relevant ANN models. The river characteristics predicting presence or absence of the benthic macroinvertebrates best were the Julian day, conductivity, and dissolved oxygen content. These conditions reflect the importance of discharges of untreated wastewater that occurred during the period of investigation in nearly all Flemish rivers.     

Movement‐mediated community assembly and coexistence

Organismal movement is ubiquitous and facilitates important ecological mechanisms that drive community and metacommunity composition and hence biodiversity. In most existing ecological theories and models in biodiversity research, movement is represented simplistically, ignoring the behavioural basis of movement and consequently the variation in behaviour at species and individual levels. However, as human endeavours modify climate and land use, the behavioural processes of organisms in response to these changes, including movement, become critical to understanding the resulting biodiversity loss. Here, we draw together research from different subdisciplines in ecology to understand the impact of individual‐level movement processes on community‐level patterns in species composition and coexistence. We join the movement ecology framework with the key concepts from metacommunity theory, community assembly and modern coexistence theory using the idea of micro–macro links, where various aspects of emergent movement behaviour scale up to local and regional patterns in species mobility and mobile‐link‐generated patterns in abiotic and biotic environmental conditions. These in turn influence both individual movement and, at ecological timescales, mechanisms such as dispersal limitation, environmental filtering, and niche partitioning. We conclude by highlighting challenges to and promising future avenues for data generation, data analysis and complementary modelling approaches and provide a brief outlook on how a new behaviour‐based view on movement becomes important in understanding the responses of communities under ongoing environmental change.     

Distribution and abundance of meiofauna in intertidal sand substrata around Iceland

Iceland is situated in an important subarctic transition area where complex oceanographic dynamics occur. The intertidal, subtidal, and deep-sea faunal communities of Iceland are being intensively studied, as a critical resource for continued sustainability of fisheries and the preservation of northern littoral ecosystems. However, the meiofaunal communities and the environmental factors affecting them are still relatively poorly known. The meiobenthic metazoan community was studied with core sampling in 23 sandy beaches along the intertidal zone of the Iceland coast in a campaign developed in September 2003. Small-scale variation in meiofauna composition (major taxa) was explored and related to biotic and abiotic factors at different scales, such as beach exposure, granulometry, and organic matter content. Differences in meiofaunal community structure at a low taxonomic resolution appeared among beaches located within wide biogeographical zones of hydrobiological significance (NE and SW Shelf regions) and exposure degrees. Seventeen major taxa were recorded. In contrast with more local and taxon-focused studies, oligochaetes were the dominant group all around Iceland, followed by nematodes, turbellarians, gastrotrichs, and copepods (mainly harpacticoids). Acari, ascidians, bivalves, cnidarians, collembolans, gastropods, isopods, kinorhynchs, insects, nemerteans, ostracods, and polychaetes were relatively scarce groups, together being less than 1.6% of the meiofauna. There was a large variation in meiofaunal abundance between sites. Maximum abundances (>500 ind. cm^?2) were found in Sau?arkrökur, Hraunhafnartangi, and Skálaness, whereas minimum abundances (<40 ind. cm^?2) were recorded in Magnavík, Jokülsárlón (glacier beach site), Vikurnúpur, Breidalsvík, and Stokknes. We did not find a clear pattern in overall meiofaunal abundance regarding the degree of exposure of beaches. Oligochaetes, nematodes, and copepods were relatively more abundant in sheltered beaches, whereas turbellarians and gastrotrichs tended to be more abundant in exposed beaches. The best correlates of meiofaunal composition and abundance within beaches were the proportion of gravels and the content of utilizable organic matter in the sediment. We should consider factors operating at wider scales (importantly beach exposure and overall situation in the complex oceanographical context of Iceland) to find a pattern in the local structure of intertidal meiofaunal assemblages.     

Climate,landscape and microenvironment interact to determine plant composition in naturally discrete gravel beach communities

Question: What is the relative importance of national‐, regional‐ and within‐beach‐scale influences on vegetation composition and floristic affinities of New Zealand gravel beaches? Location: Coastal New Zealand. Methods: We sampled vegetation composition at 61 gravel beaches, quantifying site factors and adjacent landscape characteristics. Site, climate and geographic relationships between gravel beaches and related ecosystems were inferred using GIS data layers. To simultaneously investigate influences at different spatial scales, we used ordination and variation partitioning to examine relationships between composition and environment, and hierarchical models to understand floristic affinities with related ecosystems. Results: At a national scale, compositional variation among beaches reflects mean annual temperature and spring vapour pressure deficit; within regions, proximity of native woody vegetation and coastal turfs are important; within‐beach variation is related to substrate stability and particle size distribution. The gravel beach flora is 50% exotic, reflecting the highly modified nearby landscapes; 30% of species are characteristic of coastal sands, 20% of braided riverbeds and 8% of coastal turfs. Affinities with coastal sand communities are unrelated to microsite sandiness or area of sand dunes within 50 km. Affinities with braided riverbeds are related to the bed area of those rivers draining within 200 km and proportion of gravel in the substrate. Affinities with coastal turfs are related to proximity to the nearest turf and the proportion of humus in the substrate. Conclusions: Examining multiple scales of influence in a landscape context is essential to understand composition of naturally discrete ecosystems that span wide geographic ranges and to underpin their conservation management.     

Evaluation of beach vegetation for conservation/rehabilitation in Tottori Prefecture,Southwest Japan

We examined 17 beaches in Tottori Prefecture to evaluate the current status of beach vegetation for conservation/rehabilitation purposes. We conducted a floristic survey and a beach vegetation status survey, and analyzed the beach environment using aerial photographs and a geographic information system. The health of the beach vegetation was evaluated by principal component analysis (PCA) of beach vegetation and environmental variables. PCA of beach vegetation variables, where axis 1 represented the scale of beach vegetation and axis 2 represented the quality of beach vegetation, resulted in four categories. PCA of beach environment variables, with axis 1 representing the synthetic component of grain/area/extension and axis 2 representing beach widths, also resulted in four categories. A beach vegetation list was determined from a floristic survey, and three conclusions were made based on this list. We first determined the priority of the beach plant species with regard to conservation. Based on their occurrence, the beach plants were divided into four types that were ordered with regard to their priority for beach plant conservation. We next focused on the occurrence of beach plants listed in the Red data book for Tottori Prefecture and reexamined the validity of the extinction risk category. Our conclusion was that this category needs to be updated. Finally, we compared the number of beach plant species of the survey site beaches with that of the Tottori Sand Dunes, where more natural conditions prevail. We found that only seven beaches equaled or surpassed the Tottori Sand Dunes in terms of the number of plant species. Based on these findings, we concluded that beaches other than the Tottori Sand Dunes are in need of conservation/rehabilitation.     

Community structure of macrobenthos in homestead ponds of Noakhali coast,Bangladesh

The integrity of the homestead pond supply depends on how various macrobenthic communities make their living more diversified and contribute to complex food webs. In addition, the macrobenthic community are significantly used as indicator organisms to detect the pollution impacts in aquatic ecosystems. In this study, we show the data about the diversity and community structure of macrobenthos and their relationship with environmental variables in homestead ponds of Noakhali coast from January 2019 to August 2019. The current study yielded 17 species belonging to seven taxonomic groups with a mean density of 3630 ind./m². The Nematode community, comprising 48.86% of the total taxonomic groups with Prionchulus sp. as the dominant macrobenthic species represented more than 31% of the total macrobenthic taxa, and showed a significant negative correlation with the value of salinity, DO, pH. The environmental variables and diversity indices were detected significant variations (P < 0.05) among stations by the Kruskal-Wallis ANOVA, whereas Shannon-Wiener Diversity Index (H´) assessed moderate pollution, Evenness index (J) assessed uniform distributions of macrobenthic community, and environmental variables showed acceptable condition for the productivity of ponds. Cluster analysis (CA) and Non-metric multidimensional scaling (nMDS) demonstrate demarcations in the community structure of macrobenthos between samples. Within macrobenthic communities, Canonical Correspondence Analysis (CCA) provided insights and interpretations of the relationships between species and environmental gradients. Macrobenthic community reached the most abundance at a lower temperature, transparency and a higher DO, pH and salinity.     

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.