Seasonal dynamics of amphipod assemblages in intertidal coralline algal mats on two Brazilian shores

Coralline algae form important rocky intertidal habitats, but their function may be radically changing worldwide as increased land deforestation may ultimately lead to higher sedimentation rates over algal mats, and more frequent extreme weather conditions may increase physical disturbances. One way of addressing how environmental change may affect the ecosystem function of coralline algal mats is to examine the temporal dynamics of invertebrate assemblages associated with this habitat, and how they correlate to key environmental factors. Here, we investigated the dynamics of amphipod assemblages inhabiting coralline algal mats at two sites in southeastern Brazil from September 2010 to August 2013. Twenty-two different species were recorded, encompassing two lifestyles (free-living and tube-dwelling), and four feeding habits (detritivorous, omnivorous, herbivorous, and carnivorous). Consistently across sites and over the years, species diversity peaked in autumn, together with the passing of cold fronts and increased wave height. Physical disturbance through wave action caused algal mat thinning and reduced overall amphipod abundance, suggesting habitat limitation, but also decreased species dominance, allowing other species to build up populations over autumn and winter. The omnivore generalist Apohyale media (Dana, 1853) tended to dominate in spring and summer, when the environment was more stable, and the organic matter retained in sediments was higher. When environmental conditions changed during autumn and winter, a second omnivore, Hyale Niger (Haswell, 1879), took over, especially in years 1 and 3. During year 2, the virtual absence of H. Niger allowed the detritivore Lysianassa temimino Senna and Souza-Filho, 2010 to thrive, which was likely facilitated by the retention of assorted sediments951839

Stratified settlement and moulting competency of brachyuran megalopae in Ponta Rasa mangrove swamp, Inhaca Island (Mozambique)

Information on recruitment processes of mangrove crustaceans is very limited, in spite of the great importance of these environments for the coastal zone. This study describes the settlement patterns of brachyuran crabs at Ponta Rasa mangrove swamp, Inhaca Island, in order to assess if settlement patterns reflect adult distribution. Hoghair filter collectors were deployed at different strata within the mangrove, and at the adjacent intertidal flat as control. Sampling was conducted daily for a period of 82 days. The collected megalopae were reared in the laboratory to assess their moulting competency and to enable identification. Settlement intensity was tested for association with wind stress, from different directions and averaged over time lags up to 6 days. A total of 960 megalopae settled during this study. Only 8% of the megalopae that settled at the control site belonged to mangrove dwelling species. Settlers inside Ponta Rasa swamp were exclusively mangrove species. Ilyograpsus paludicola settled mainly among Rhizophora mucronata and the mixed area of Ceriops tagal and Bruguiera gymnorrhiza, where adults occur, and Perisesarma guttatum, the most abundant sesarmid at Ponta Rasa, settled mainly at the creek. Neosarmatium meinerti settled among Avicennia marina pnematophores, very close to the adult populations. Megalopae of mangrove taxa that settled outside the mangrove took longer to moult than the ones settling inside the swamp. In the intertidal areas of the mangrove, settlers took an average of 1–2 days to moult, whereas in subtidal areas time to moult was on an average 3–5 days. Thus, both distribution of settlers and moulting competency suggest that settling follows adult distribution. Tides have a strong influence on settlement at Ponta Rasa, with the effect that, due to the high sill at the entrance, neap tides do not penetrate the mangrove. The analysis of settlement data suggested a significant effect of wind-driven transport on onshore migration. There is however no obvious interpretation for the pattern observed. Probably, the distribution of different larval patches and the complex dynamic structure of currents within Maputo Bay and adjacent areas influence the settlement pattern

Present and future invasion perspectives of an alien shrimp in South Atlantic coastal waters: an experimental assessment of functional biomarkers and thermal tolerance

International audienceClimate change, particularly ocean warming, is thought to benefit the spread of invasive species due to their increased tolerance to temperature fluctuations as compared to native species. The physiological tolerance of invasive species as a potential mechanism driving invasion success is therefore a subject that merits further study. Specifically, we need to adequately evaluate the potential of species invasions under changing environmental conditions, so that adequate preventive measures can be taken to minimize any impacts on coastal ecosystems. Here, we experimentally evaluated the physiological responses of a recent invader in the Southern Atlantic, the shrimp Lysmata lipkei, under a warming ocean scenario. Adult shrimps were collected from rocky shores in southeastern Brazil and subjected to experimental trials under a control and a + 3 °C scenario. Molecular biomarkers (in gills and muscle), upper thermal limits, acclimation response ratios, thermal safety margins, mortality rates, estimates of body condition and energy reserves were measured over 1 month. Results suggest that higher temperatures elicit physiological adjustments at the molecular level, underpinning a high thermal tolerance. In addition, results indicated substantial acclimation capacity, with no evidence of decreased performance under an ocean-warming scenario. Thermal safety margins were low for shrimp from intertidal rock pools but high for shrimp from subtidal habitats. We conclude that the thermal tolerance of this shrimp species may favor its ongoing invasion along the Southwestern Atlantic Ocean, mainly in subtidal habitats, both under present and future thermal conditions