• European Marine Science
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• Estuarine Coastal and Shelf Science close

The ocean quahog Arctica islandica is equally attractive to physiologists and environmental scientists due to its long life span of up to 400 years . For physiology, A. islandica is an exciting age model whereas environmental sciences infer past environmental conditions from morphometric and biogeochemical properties of the calcareous shell. In order to evaluate whether and animals from different localities differ, the present study compared genetics and morphometry of six A. islandica populations, from the Norwegian Coast, Kattegat, Kiel bay, White Sea, German Bight and Off Ne Iceland. For genetics, present research found 30 haplotypes of the mitochondrial cytochrome B (cyt B) gene, of which some are widely distributed, whereas others are quite rare. There is no consistent geographical pattern in haplotype distribution, even when a further previously published 11 haplotypes are taken into account. For morphometry, discriminant analysis indicated significant morphometric differences, e.g. in shell shape, between populations which are independent of geographical distance. Moreover, genetic and morphometric patterns appear to be unrelated. Thus, present study reveals morphological differences between populations of A. islandica appear to be driven by the environment rather than underlying genetic differences between populations.

Abstract The presence of mangrove trees and crab burrows potentially contribute to localized variation in sediment elevation and affect sediment characteristics in these ecosystems, but the interacting effects of trees and burrows are largely unknown. Using a field study and artificial burrow experiment, we investigated variation in sediment redox potential, organic matter content, carbon to nitrogen ratios and activities of microbial communities related to presence and absence of trees and burrows. The presence of mangrove trees of the species Ceriops australis decreased the redox potential of the sediment, which may favor organic matter preservation, but no significant differences were observed in percent organic matter in sediment next to trees versus distant from trees. The effects of C. australis on sediment redox conditions were counteracted by the presence of crab burrows in deeper (20 cm) sediments. The utilization of a variety of carbon sources by microbial communities varied between the surface of crab burrow walls and bulk sediment, indicating crab burrow-induced changes in microbial communities, whereas the presence of C. australis did not affect community-wide microbial activity patterns and did not interact with the effects of crab burrows. The novel artificial crab burrow-mimics replicated these results, where organic matter and carbon to nitrogen ratios did not change over the experiment course whilst redox did. Differences in carbon-utilization by microbial communities between artificial burrow walls and bulk sediment mimicked those between natural crab burrow walls and bulk sediment. Hence, in the environmental settings of this study, it was the presence of burrow structures rather than crabs that induced changes in microbial communities.

© 2021 The Authors. While mangroves are increasingly described as social-ecological systems (SESs), performing SES research is so much more than merely documenting local resource utilisation patterns in case studies. The aim of this paper is to review and show how ecological, human and institutional resilience could be understood and fostered in an era of uncertainty, through the adaptive cycle (AC) heuristic. Uncertainties come in many forms and shapes: climate change, social and economic dynamics, natural disasters, political and institutional disruption and ever-increasing public demands for participation. Social-ecological studies form windows of experimentation that can provide insights beyond their case-specific context. In order to synthesise and structure the cumulative knowledge base arising from existing and future studies, the need for a suitable overarching framework arose. Here, the AC heuristic represents the connectedness between variables of the mangrove SES versus the mangrove's accumulated capital (natural, built, human and social). We posit that the AC heuristic can be used to interpret spatial and temporal changes (ecological, social, economic, political) in mangrove SESs and we exemplify it by using the 2004 Indian Ocean tsunami as well as a century-long silviculture case. The AC, combined with the SES scheme, allows integration of the spato-temporal dynamics and the multi-dimensional character of mangrove SESs. We also reviewed the ecosystem functions, services and disservices of mangrove SESs, linking each of them to SES capital and variable (fast or slow) attributes, which in turn are closely linked to the different axes and phases of the AC. We call upon mangrove scientists from the natural, applied, social and human sciences to join forces in fitting diversified empirical data from multiple case studies around the world to the AC heuristic. The aim is to reflect on and understand such complex dynamic systems with stakeholders having various (mutual) relationships at risk of breaking down, and to prepare for interactive adaptive planning for mangrove forests. Belgian Science Policy Office ‘EVAMAB – Economic valuation of ecosystem services in Man & Biosphere Reserves' - BELSPO (BL/58/UN32); Erasmus Mundus Masters Course in Tropical Biodiversity and Ecosystems (TROPIMUNDO); VLIR-UOS-funded GREENDYKE Project (ZEIN2008PR347); BELSPO-funded MAMAFOREST-Project (SR/00/323); ZMT Academy travel grant; Singapore National Parks Board (NParks); TUYF Charitable Trust; HKU Seed Fund for Research; International Coral Reef Initiative (ICRI); UNEP/GEF Blue Forest Project; Pew Charitable Trust; Department of Science and Technology, India INSPIRE Faculty scheme (IFA18-LSPA111);