Knowledge of reproductive biology is essential for ecological studies on coral population dynamics. The azooxanthellate colonial coral Astroides calycularis is endemic to the western Mediterranean Sea and adjacent Atlantic coasts. Specimens of this species in artificial conditions, an aquarium with enclosed seawater and low food availability, appeared to show an asexual dispersal mechanism. This mechanism consisted of the detachment and release of single, skeletonless polyps from the underlying colony skeleton (i.e., polyp bail-out). While the released free-living polyps regularly showed extended tentacles and most of them survived, they did not show re-attachment to the substrate or any skeleton formation until the end of the experiment, ∼2–3 months after bail-out. Formation of new reproductive colonies, thereby the eventual completion of asexual reproduction through polyp bail-out in A. calycularis, still needs to be confirmed. In addition to sexual reproduction, polyp bail-out may constitute an alternative propagation mechanism during periods of environmental stress, thereby potentially increasing the survival rate of the parental genotype and the dispersal by drifting soft polyps. © 2017 Senckenberg Gesellschaft für Naturforschung and Springer-Verlag Berlin Heidelber

Before‐After‐Control‐Impact (BACI) designs are widespread in environmental science, however their implicitly hierarchical nature complicates the evaluation of statistical power. Here, we describe epower, an r package for assessing statistical power of BACI designs. The package uses Bayesian statistical methods via the r‐package INLA to fit the appropriate hierarchical model to user supplied pilot survey data. A posterior sample is then used to build a Monte Carlo simulation to test statistical power specifically for the Before/After × Control/Impact interaction term in the BACI model. Power can be assessed for any number of user‐specified effect sizes for the existing design, or across a range of levels of replication for any part of the sampling design hierarchy. The package offers a user friendly robust approach for assessing statistical power of BACI designs whilst accounting for uncertainty in parameter values within a fully generalized framework.

The study of a Posidonia australis sediment archive has provided a record of ecosystem dynamics and processes over the last 600 years in Oyster Harbour (SW Australia). Ecosystem shifts are a widespread phenomenon in coastal areas, and this study identifies baseline conditions and the time-course of ecological change (cycles, trends, resilience and thresholds of ecosystem change) under environmental stress in seagrass-dominated ecosystem. The shifts in the concentrations of chemical elements, carbonates, sediments <0.125 mm and stable carbon isotope signatures (δ(13) C) of the organic matter were detected between 1850s and 1920s, whereas the shift detected in P concentration occurred several decades later (1960s). The first degradation phase (1850s-1950s) follows the onset of European settlement in Australia and was characterized by a strong increase in sediment accumulation rates and fine-grained particles, driven primarily by enhanced run-off due to land clearance and agriculture in the catchment. About 80% of total seagrass area at Oyster Harbour was lost during the second phase of environmental degradation (1960s until present). The sharp increase in P concentration and the increasing contribution of algae and terrestrial inputs into the sedimentary organic matter pool around 1960s provides compelling evidence of the documented eutrophication of the estuary and the subsequent loss of seagrass meadows. The results presented demonstrate the power of seagrass sedimentary archives to reconstruct the trajectories of anthropogenic pressures on estuarine ecosystem and the associated regime shifts, which can be used to improve the capacity of scientists and environmental managers to understand, predict and better manage ecological change in these ecosystems.

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For large fishes, seagrass canopies typically provide a relatively flat habitat on seabeds, but seagrasses in the genus Posidonia can provide additional habitat complexity by forming organic-rich deposits known as mats. Erosional processes can scour channels through the mats, resulting in the formation of escarpments with caves. Here we report that reef fishes, such as groupers, inhabit the caves found within mat escarpments. The characteristics of the cavities are highly variable, ranging from small-elongated holes to deep caves with large entrances. The origin of these caves (biological and/or geological) is unknown, but it is possible that fish behavior enhance their formation. Posidonia seagrass escarpments provide a complex 3D habitat for reef fish that is not provided by typical canopy structure of seagrass. Further studies are required to gain insights into the natural history of seagrass escarpments and their ecological importance.