THE USE OF POPULATION ASPECTS OF THE GHOST CRABS AS INDICATORS OF ANTHROPOGENIC IMPACT ON URBAN BEACHES OF THE BRAZILIAN SEMIARID COAST

Temporal changes in macrofauna as response indicator to potential human pressures on sandy beaches

Crustaceans as ecological indicators of metropolitan sandy beaches health

Ghost Crabs, Ocypode cursor (Linnaeus, 1758), are used as a bioindicator species to evaluate the ecological condition of sandy beaches. Studies using Ghost Crabs as bio-indicator have often focused on the influence of human disturbance and beach geomorphology, separately. However, the relative importance of these variables should be assessed to maintain community structure. Here, I used an indirect burrow examination technique to understand whether Ghost Crabs respond to human disturbance stronger than to geomorphological properties of the sites. I analysed sand compaction rate, sand grain size, beach width, and beach slope as geomorphological features and urbanization index as a measure of human disturbance on each site. I further examined Ghost Crab burrows by counting and measuring the openings. Ghost Crabs showed lower population density and individual body sizes as a response to human disturbance, and the level of this response was partly related to the geomorphological features of the sites. However, human disturbance explained approximately 72% of the variation in the Ghost Crab burrow density and about 70% of the variation in the burrow size, alone. The findings of this study corroborate the use of Ghost Crabs as an efficient bioindicator species of human disturbance on sandy shores to achieve efficient beach management, yet suggest that managers and scientists should combine the influences of geomorphological features of the beaches and the degree of human disturbances in their ecological assessments.

Spatial and temporal variations of litter at the Mediterranean beaches of Morocco mainly due to beach users

Digital rock modeling to quantify scale dependence of petrophysical measurements in burrowed reservoir rocks: An example using Thalassinoides

Urbanisation alters processing of marine carrion on sandy beaches

Quantifying solute distributions in the bioturbated zone of marine sediments by defining an average microenvironment

Fluctuating asymmetry of two crustacean species on fourteen sandy beaches of Rio de Janeiro State

The spatial distribution of the ghost crab Ocypode quadrata (Crustacea, Brachyura) was described in five low‐energy tide‐dominated sandy beaches in São Sebastião Channel (Grande, Zimbro, Pitangueiras, Cabelo Gordo, and Segredo). On each beach, the zonation study was performed on five random 1 m wide transects sampled from the water line to the vegetation. In general, individuals occurred above 1 m in height in relation to mean low water (MLW) and peaked between 1.5 and 2.0 m. The sandy beaches were then divided into three 1 m wide strips (tidal levels) parallel to the water line and equivalent to medium intertidal, upper intertidal, and subterrestrial fringe to test the effect of beach and tidal level on the abundance and size of O. quadrata. These strips were sampled as a whole using adjacent 1 m2 squares. A previous evaluation showed a positive significant relationship between carapace length and burrow diameter, thus supporting crab size estimates from burrow openings. The smallest individuals occurred mainly in the medium intertidal, but were also recorded in the subterrestrial fringe, which was occupied mainly by large‐sized individuals. In general, the individuals were randomly dispersed within the strips and concentrated in the upper intertidal zone on all the sandy beaches. The density of O. quadrata varied among beaches, with a tendency to lower values on areas with very fine and poorly or moderately sorted sediments and on that most used for recreational activities (Grande). Burrow size also varied among beaches, with a tendency of smaller burrows in areas with coarser sand grains and higher tourism. These results indicate that the effect of human impact on density and size of O. quadrata may be confounded by the high environmental heterogeneity of the studied system, which may make it difficult to utilize this species as an indicator of the conservation status of low‐energy tide‐dominated sandy beaches.

The data from 161 quantitative sandy beach transect surveys from a wide variety of locations were examined to identify trends and relationships between total marine macrofauna species richness, abundance, and biomass and physical variables. Several physical variables were correlated, especially sand particle size and beach face slope, and spring tide range and beach face slope. Higher latitudes experienced larger waves, and flatter beaches had finer sands, larger waves, and larger tides. Strong correlations were found between species richness and beach slope, tide range, and sand particle size, as well as various indices of beach state. Tropical regions harbored significantly more species than other regions. A new Beach index (BI), based on tide range, beach face slope, and sand particle size, correlated well with species richness, explaining 56% of the variability in the data without considering latitude. Abundance and biomass were best correlated with log(1/beach face slope) and tended to be higher in temperate regions. General patterns are discussed; the new index is evaluated; and the roles of sand, tide, slope, and latitude are considered. It is concluded that for regional studies log(1/beach face slope) is the most useful index to compare beaches, whereas for wider comparisons covering areas of differing tide range, BI might be most useful. These patterns have implications for global biodiversity management on sandy beaches.

An estimate of the value of the beachfront with respect to the hotel room rates in Thailand

This study evaluated the seasonal changes in the abundance and composition of microplastics in beach sands from urban and rural beaches along Sarangani Bay Protected Seascape, Mindanao, the Philippines. Sand samples were collected during the wet season (August) and dry season (December) using the quadrat-based protocol, and microplastics were extracted using the flotation method. A total of 110 microplastics were collected, with 87 found in the wet and 23 in the dry seasons. Urban beaches during the wet season (0.047 particles/g) exhibited significantly higher (p < 0.05) microplastics than during the dry season (0.015 particles/g). Microplastics are significantly influenced by seasonal changes, particularly during the rainy season when increased precipitation enhances water flow, facilitating the transport of plastic materials from land sources into aquatic environments, leading to higher microplastic concentrations. Fourier transform infrared spectroscopy (FTIR) analysis was employed to identify the chemical composition of the microplastics, revealing the primary polymers present, including polyester (23.1%) and polyethylene (23.1%). In urban areas during the wet season, both polyethylene and polyester were the most dominant polymer types, each comprising 37.5% of the total. In contrast, during the dry season, phenoxy resin emerged as the sole dominant polymer type. Rural areas displayed a more varied composition during the wet season, with three polymer types recorded: propylene, polyethylene terephthalate (PET), and butyl methacrylate, each at 33.3%. However, only PET was recorded during the dry season. The highest microplastic abundance was observed in urban beach sediments during the wet season, suggesting urban runoff sources. The findings highlight the influence of human activities on coastal plastic pollution, enhanced by erosion and wet deposition during the wet season. These are crucial to reducing the influx of microplastics, safeguarding the marine ecosystem, and ensuring sustainable coastal environments for future generations.

AimWhile geographical patterns of species richness are reasonably well explored for single well‐studied taxa, less is known about aggregate patterns of total richness for major biomes and their environmental correlates. Here we analyse continental‐scale aggregate patterns of macrofaunal diversity for sandy beaches, a dominant habitat along the Atlantic and Pacific coasts of South America.LocationSouth American coastlines.Time periodPresent day (data amassed from studies performed since 1971).Major taxa studiedBenthic macrofauna, including crustaceans, polychaetes and molluscs.MethodsWe compiled richness information for all macrofaunal groups on 263 sandy beaches in South America using standard criteria. We further matched these data with environmental variables including sea surface temperature (SST), chlorophyll a, grain size, beach slope, tide range and various morphometrics. We used generalized linear mixed models to relate environmental factors to observed variation in total macrofaunal richness across all beaches, testing competing hypotheses about environmental correlates and possible drivers of latitudinal diversity.ResultsMacrofaunal richness decreased from tropical to temperate beaches in the Pacific and followed a parabolic trend in the Atlantic, with the highest biodiversity found at tropical and mid‐latitudinal bands. Beach slope, tidal range and chlorophyll a mostly explained latitudinal trends in macrofaunal richness, followed by grain size, SST and ocean basin.Main conclusionsThis study indicates that richness of macrofaunal species at a given beach is most closely related to characteristics of the physical habitat, such as beach slope, area and grain size. At this scale, planktonic food supply also appeared to be more important than temperature, which is a dominant explanatory variable of global‐scale variation in species richness.

Global patterns in sandy beach macrofauna: Species richness, abundance, biomass and body size

Microplastic pollution stands as an emerging threat to sandy beach ecosystems, globally. However, beaches are three-dimensional systems, and only a limited number of studies investigated the vertical and horizontal distribution of microplastics in these systems. Furthermore, the causative drivers behind the three-dimensional distribution of microplastics on sandy beaches have not been well understood. Therefore, 7 potential factors including total organic content, sand grain size, beach length, and width, the proximity of the study site to the closest city center (a proxy for the tourism influence), cleaning frequency of the beaches, and road type next to the beach on nine sandy beaches of the Turkish Coast of the Black Sea were collectively investigated as causative drivers. Microplastic abundance, size, and compositions were examined in sand samples collected at different depths between 0 and 105 cm. While microplastic abundance was evenly distributed horizontally, it showed a gradual decline with increasing depth. The abundance of microplastics varied between 21.18±0.98 item/kg-1 (at the beach surface) and 2.78±0.93 item/kg-1 (at the deepest sampling point). Potential factors examined here explained 84.7% of the variation in microplastic abundance with the highest relative influence by wave actions. Microplastic size showed a seaward decline on the beach surface with 1045.11±274.36 μm, but it seemed similar between depths. Other characteristics (color, shape, and polymer type) significantly differed between depths and tidal heights. The majority of the microplastics were fragments (38.4%) and foams (37.8%). White was the most available microplastic color with 30.23%. Microplastics detected on these sites were dominated by polystyrenes. The factors examined here explained their variations of microplastic characteristics between 84.25% and 89.14%. This study provides important insights into the current literature by examining multiple causative drivers for the three-dimensional microplastic distribution on sandy beaches, which should be useful for management strategies to reduce the impact of these contaminants on organisms.