Can Antarctica's shallow zoobenthos 'bounce back' from iceberg scouring impacts driven by climate change?

All coastal systems experience disturbances and many across the planet are under unprecedented threat from an intensification of a variety of stressors. The West Antarctic Peninsula is a hotspot of physical climate change and has experienced a dramatic loss of sea‐ice and glaciers in recent years. Among other things, sea‐ice immobilizes icebergs, reducing collisions between icebergs and the seabed, thus decreasing ice‐scouring. Ice disturbance drives patchiness in successional stages across seabed assemblages in Antarctica's shallows, making this an ideal system to understand the ecosystem resilience to increasing disturbance with climate change. We monitored a shallow benthic ecosystem before, during and after a 3‐year pulse of catastrophic ice‐scouring events and show that such systems can return, or bounce back, to previous states within 10 years. Our long‐term data series show that recovery can happen more rapidly than expected, when disturbances abate, even in highly sensitive cold, polar environments

Competition between co-occurring invasive and native consumers switches between habitats

1.The introduction of a non‐native species frequently has adverse direct effects on native species. The underlying mechanisms, however, often remain unclear, in particular where native and invasive species are taxonomically similar. 2.We found evidence of direct competitive interactions between a globally distributed invasive species (the Pacific oyster, Magallana gigas) and its native counterpart (the European oyster, Ostrea edulis). We also discovered that the competitive outcome differed between different habitat types and orientation by identifying context‐dependent responses driven by environmental conditions and stress (i.e. intertidal compared to subtidal habitats; and vertical versus horizontal substratum). This is particularly important because the European oyster is threatened, or in decline, throughout most of its range and restoration efforts are underway in many regions. 3.We combined experimental manipulations and stable isotope analysis (SIA) to identify the direct effects of competition and the mechanisms by which the invasive and native species compete. We identified negative effects of the invasive species on the native oyster but these were limited to the subtidal habitat (lower stress environment) and determined by substratum orientation (habitat structure). Crucially, we found that effects of the invasive species on the native species were not always negative and under certain conditions (e.g. on vertical substrata) were positive. Shifts in isotopic niches of both species when co‐occurring, alongside mixing models, indicate that exploitative competition for food is most likely to underpin niche partitioning between both species. 4.We have identified different foraging strategies under different contexts and our findings highlight the importance of exploitative competition as a driving mechanism behind the co‐occurrence of two seemingly functionally similar consumers. The combination of experimental manipulations with SIA is a powerful tool and we illustrate how this approach should be incorporated, into multiple environmental contexts at appropriate scales, to more accurately predict impacts of the spread of invasive species on native communities

Use of emerging technologies to help measure fjordic biodiversity and blue carbon: mini-manned submarines and autonomous underwater vehicle swarms

Meaningful protection of global oceans lags far behind that of land and has taken little consideration of climate mitigation potential to date (such as through assessment of blue carbon stocks and change). With the new emphasis on synergistic approaches to the identification and conservation of both carbon- and species- rich habitats, we need much better knowledge of the geography and status of blue carbon habitats beyond coastal wetlands. In subpolar and polar regions, some blue carbon habitats are still emerging and work as negative (mitigating) feedback on climate change, yet remain unprotected despite strong evidence of threat overlap. Scientific research expeditions are gradually increasing our understanding, but appropriate vessels are a limiting factor due to high costs and carbon footprints. Even when available such vessels cannot access all areas (e.g., remote fjords with sills) and may struggle to measure certain aspects of habitats (e.g., steep or vertical surfaces). New technologies and opportunities have advanced to aid some of these problems, and here, two of them are considered, mini-manned submersibles and autonomous underwater vehicles. These two platforms have both become much more available and affordable (through novel partnerships) while also being much more scientifically capable. This technology has the potential to reduce the carbon footprint of science and particularly aid in assessing biology and environment status and change on steep sides, such as fjord walls

Bonamia infection in native oysters (Ostrea edulis) in relation to European restoration projects

1. There is a growing effort throughout Europe to restore populations of native oysters (Ostrea edulis), with the ecological objective of enhancing ecosystem biodiversity and resilience. 2. The introduced parasite, Bonamia ostreae, caused catastrophic mortalities during the 1980s, furthering the decline of this species, and is now present throughout much of the natural range of O. edulis. It is therefore important that restoration attempts avoid further introduction and spread of this parasite, which can cause lethal infections of O. edulis. 3. This article presents a comprehensive overview of the scale and distribution of current infection, transmission pathways, and preventive measure guidelines, focusing on the seas, inlets, and estuaries of north‐west Europe, where most ecological restoration attempts for the native European oyster have occurred so far. 4. This is critical information for restoration project planning in which the risk of Bonamia infection must be taken into account

Diversitätsmuster und Artenkomposition entlang von Stressgradienten in der Helgoländer Gezeitenzone.

Diversity is affected by a variety of biotic and abiotic factors. To predict and appreciate how diversity is changing along various stress conditions an environmental stress model (ESM) (Menge & Sutherland) has been developed 20 years ago. Since then it has been adjusted to recent results of studies for a more accurate evaluation, concerning the pattern of diversity along stress gradients. For this model a unimodal graph is expected for diversity following a physical stress gradient. Weak competitors who are adapted to extreme conditions are responsible for the low diversity at high stress conditions, while the low diversity at low stress is a result of competitive exclusion of dominant species. We tested the ESM on three rocky shores differently exposed to wave action on Helgoland Island, Germany in a mensurate field experiment. Former research investigating the ESM in the rocky intertidal on Helgoland has not met the expectations of the ESM completely. To determine whether the ESM doesn't apply for Helgoland or if the experimental design lacked precision we altered the design to a higher vertical resolution of samples. We were taking samples from the beginning of May to mid June 2010. To be able to also adress biotic factors in our study we measured species composition besides diversity, species richness and evenness of macrobenthic organisms. On none of the three studied shores we could find a characteristic unimodal graph for the diversity along an environmental stressgradient accordingly to Menge & Sutherland (1987). However at the protected shore we observed an increase of diversity from high to low stress. The missing decrease of diversity in the lower eulittoral, is a result of the high density of microhabitats formed by macroalgae. Furthermore, we detected a connection between the patterns of diversity and wave exposure. Thus the observed diversity-pattern becoming flatter with an increase in wave exposure. A comparison of the diversity in two unlike habitats at the same shore aroused the consideration that abiotic factors might have different impacts on two different positions at the same shore. Concluding we found that the identity of species is important to comprehend the pattern of diversity following an environmental stress gradient. The ESM doesn't include this factor adequately and is therefore not a universal model applicable on all coasts. This is why we suggest that the ESM needs further development especially concerning biotic factors

Zwerschke_et_al_2018_IBIS_GrowthRate_Mortality

Zwerschke_et_al_2018_IBIS_GrowthRate_Mortalit