Search

Abstract: Drift macroalgae detached from rocky substrate frequently strands on the shore line, driving a number of ecological processes, such as degradation, consumption, habitat supply and biogeochemical processing. The algal subsidies received by beaches of Foster Bay, in Deception Island, were evaluated in terms of the spatio-temporal dynamics of wrack deposits. Predominance in the strands of a single red blade species, Palmaria decipiens, points toward an equivalent abundance in the subtidal macroalgal beds, accompanied by Desmarestia menziesii and Desmarestia antarctica, among others. Biomass measurements and wrack grooming along the intertidal range over time indicate that an instantaneous stock of 39.9MT of algal debris strands on the shore line of Foster Bay, with more than 50% of these materials being renewed at each tidal cycle. Estimates of macrophyte production fluxing to the bay ecosystems suggest that only a small fraction (2.8%) of the detached material within the bay accumulates as wrack along the intertidal zone. Variability in the amount of algae along the shore is significantly affected by wind direction or coastal orientation, with larger strandings when sea–land winds prevail. The degradative process of algal wrack was analyzed through a litter bag experiment where pre-weighted fragments of P. decipiens and D. menziesii were sequentially removed from the drift line along 14days. Degradation of wrack biomass occurs within the first days of decaying, loosing up to 41.3% of its initial weight (D. menziesii), with remarkable variability among the two species tested. Higher feeding rates of amphipods were obtained with P. decipiens compared to that on D. menziesii, which can be mediated by its low content in deterrents and its blade shape, as well as being the most abundant species in the Deception Island and in many coastal areas of the Antarctic Peninsula. Globally, the consumer species assayed could process through consumption 0.73%day−1 of the instantaneous stock of algal deposits along the shore of Foster Bay. This study attempts to identify different linked processes poorly understood in the ecology of Antarctic shores, as the stranding, degradation and consumption of large amount of macroalgal subsidies from highly productive submerged rocky substrates toward low productive intertidal sedimentary shores. [Copyright &y& Elsevier]

Ten sandy beaches along the north coast of Spain were studied during September 1999 to analyse the number of species, abundance and biomass of macroinfauna along a gradient of intermediate beach types and exposure range. Faunal samples were collected with metallic cylinders (25 cm diameter, 15 cm depth) at 10 equally spaced shore levels along six replicated transects separated randomly and extending from above the drift line to the low tide swash zone. Exposure rate, Dean''s parameter (Ω), beach state index (BSI) and relative tidal range (RTR) were estimated at each beach. Length and width of the beach, intertidal slope, sorting and median grain size and also swash amplitude and wave characteristics were measured. The number of species was between 10 and 29. Macrofaunal abundances ranged between 4962 and 71,228 ind. linear m-1 and between 31 and 329 ind. m-2, while biomass (ash free dry weight) ranged between 0.027 and 0.278 g m-2 and between 3 and 61 g linear m-1. The results show some significant trends: the number of species is the biotic variable most affected by physical and morphodynamic factors, increasing linearly with relative tidal range and decreasing with increasing average grain size. The same trend was observed from exposed to very exposed beaches and the biomass decreased exponentially with increasing average grain size. These trends agree with previous studies in different coasts in the world where coarse sands limit the benthic macrofauna. The morphodynamic parameters as Dean''s parameter or Beach State Index did not show a predictive value. The results suggest that different characteristics of benthic macrofauna communities in intermediate beaches can be affected in different ways by the physical processes involved in beach morphodynamics. [Copyright &y& Elsevier]

Antarctic benthic ecosystems support a unique fauna characterized by high levels of diversity and endemism. However, our knowledge of the macrofauna communities across the Antarctic intertidal sedimentary shore is limited, and their fundamental ecological features, including spatial variability, remain poorly understood. This study aimed to investigate the abundance, community structure (i.e. taxa-specific abundance), and biodiversity patterns (α-, β-, and λ-diversity) of benthic macrofauna communities on intertidal sedimentary shores of two Antarctic islands (South Shetland archipelago, N of Antarctic Peninsula): Livingston and Deception. We conducted a quantitative sampling during two Austral summer campaigns (2004 and 2005), studying eleven intertidal sites, with five sites located on Livingston and six on Deception. Our results demonstrated a significantly higher abundance of intertidal benthic macrofauna communities on Livingston than on Deception. Furthermore, significant differences in community structure were observed between the two islands. In terms of biodiversity patterns, there were no significant differences in the number of taxa within communities (α-diversity) between the two islands. However, significant differences in the variation of community composition (determined by the number and identity of taxa) between intertidal sites (β-diversity) were observed, shedding light on the higher total taxa count (λ-diversity) on Livingston compared to Deception. We suggest that the island-specific characteristics (e.g., granulometric characteristics, ice disturbance, sedimentation rates, and geothermal activity) determine the differences observed in macrofauna communities. However, other ecological processes and factors are operating on different spatial and temporal scales (e.g., population dynamics, biotic interactions, oceanographic conditions, and climate change) that influence the occurrence and abundance of macrofaunal taxa. Our findings contribute to the fundamental understanding of the spatial variability of these communities and provide essential information for better management decisions and conservation practices in Antarctic coastal ecosystems. • The spatial variability of the macrobenthos in Antarctic intertidal sedimentary shores was investigated. • For the first time, we show that Livingston and Deception Islands support different intertidal macrofauna communities. • While α-diversity did not differ between the two islands, β-diversity was significantly different. • A multi-scale approach is essential to assess the biodiversity patterns of macrofauna in Antarctic intertidal shores. [ABSTRACT FROM AUTHOR]

Abstract: Thirty-four exposed sandy beaches on the northern coast of Spain (from 42°11′ to 43°44′N, and from 2°04′ to 8°52′ W; ca. 1000 km) were sampled over a range of beach sizes, beach morphodynamics and exposure rates. Ten equally spaced intertidal shore levels along six replicated transects were sampled at each beach. Sediment and macrofauna samples were collected using corers to a depth of 15 cm. Morphodynamic characteristics such as the beach face slope, wave environment, exposure rates, Dean''s parameter and Beach State Index were estimated. Biotic results indicated that in all the beaches the community was dominated by isopods, amphipods and polychaetes, mostly belonging to the detritivorous-opportunistic trophic group. The number of intertidal species ranged from 9 to 31, their density being between 31 and 618 individuals m−2, while individuals per linear metre (m−1) ranged from 4962 to 17 2215. The biomass, calculated as total ash-free dry weight (AFDW) varied from 0.027 to 2.412 g m−2, and from 3.6 to 266.6 g m−1. Multiple regression analysis indicated that number of species significantly increased with proximity to the wind-driven upwelling zone located to the west, i.e., west-coast beaches hosted more species than east-coast beaches. The number of species increased with decreasing mean grain size and increasing beach length. The density of individuals m−2 increased with decreasing mean grain size, while biomass m−2 increased with increasing food availability estimated as chlorophyll-a concentration in the water column of the swash zone. Multiple-regression analysis indicated that chlorophyll-a in the water column increased with increasing western longitude. Additional insights provided by single-regression analysis showed a positive relationship between the number of species and chlorophyll-a, while increasing biomass occurred with increasing mean grain size of the beach. The results indicate that community characteristics in the exposed sandy beaches studied are affected by physical characteristics such as sediment size and beach length, but also by other factors dependent on coastal processes, such as food availability in the water column. [Copyright &y& Elsevier]