Spatial and temporal variability in recruitment of intertidal mussels around the coast of southern Africa

Intensity of intertidal mussel recruitment was compared across a range of different spatial and temporal scales around the coast of southern Africa between June 1995 and October 1996. Comparison of the east and west coasts revealed significantly higher recruit densities on the west coast, corresponding to larger adult densities. This difference between the two coasts reflects biogeographic disparities in mussel species composition, growth rates and spawning intensities, oceanographic conditions and productivity. Significant spatial variations in recruitment were recorded between regions 100–1000 km apart and between localities 1–25 km apart. Results suggest that the influence of dispersal processes on recruitment patterns acts at a relatively small scale, and may affect the distribution and abundance of adults among shores only a few kilometres apart. The high variability in recruitment intensities at a scale of metres indicates that larva! supply to the shore may be locally patchy, or that settlement preferences of recruits may be sensitive to subtle small-scale differences in adult density within mussel clumps. Small-scale differences in post-settlement mortality (e.g. owing to patchy predation pressure) may also play a role. This small-scale variability in recruitment is likely to reinforce the mosaic distribution of mussels evident on many of the shores. Significant temporal variability in recruit density was recorded, both between 3-monthly sampling intervals and interannually. Seasonal differences were absent for the north-west regions, whereas asynchronous seasonal patterns were displayed in the other regions. Results suggest that temporal cycles of recruitment are irregular and episodic, which may have important consequences for the dynamics of adults. Significant positive correlations were obtained between maximal recruitment and adult abundance, measured by density, or total number of adults on the shore (stock). This could be explained by the density-dependent role of adult conspecifics in providing suitable settlement habitat, or supply-side recruit limitation. These results have important implications for the management of exploited populations of mussels around the coast of southern Africa. Exploitation may influence recruitment success via at least two processes: reduction of larval supply by depletion of adult stock, and alteration of habitat suitable for settlement. Thus, overexploitation will compromise recruitment, which is itself the only mechanism of recovery. The west-coast mussel populations are likely to be more resilient to exploitation as recruitment is more predictable over time, stocks are larger and recruitment intensities high. This brings into question the present regulations for mussel harvesting because, paradoxically, more lenient regulations are applied on the east coast, where stocks and recruitment are low, than on the west coast, where biomass, recruitment and potential for recovery are high

Assessment of scientific gaps related to the effective environmental management of deep-seabed mining

A comprehensive understanding of the deep-sea environment and mining’s likely impacts is necessary to assess whether and under what conditions deep-seabed mining operations comply with the International Seabed Authority’s obligations to prevent ‘serious harm’ and ensure the ‘effective protection of the marine environment from harmful effects’ in accordance with the United Nations Convention on the Law of the Sea. A synthesis of the peer-reviewed literature and consultations with deep-seabed mining stakeholders revealed that, despite an increase in deep-sea research, there are few categories of publicly available scientific knowledge comprehensive enough to enable evidence-based decision-making regarding environmental management, including whether to proceed with mining in regions where exploration contracts have been granted by the International Seabed Authority. Further information on deep-sea environmental baselines and mining impacts is critical for this emerging industry. Closing the scientific gaps related to deep-seabed mining is a monumental task that is essential to fulfilling the overarching obligation to prevent serious harm and ensure effective protection, and will require clear direction, substantial resources, and robust coordination and collaboration. Based on the information gathered, we propose a potential high-level road map of activities that could stimulate a much-needed discussion on the steps that should be taken to close key scientific gaps before any exploitation is considered. These steps include the definition of environmental goals and objectives, the establishment of an international research agenda to generate new deep-sea environmental, biological, and ecological information, and the synthesis of data that already exist

International genome-wide meta-analysis identifies new primary biliary cirrhosis risk loci and targetable pathogenic pathways.

Primary biliary cirrhosis (PBC) is a classical autoimmune liver disease for which effective immunomodulatory therapy is lacking. Here we perform meta-analyses of discovery data sets from genome-wide association studies of European subjects (n=2,764 cases and 10,475 controls) followed by validation genotyping in an independent cohort (n=3,716 cases and 4,261 controls). We discover and validate six previously unknown risk loci for PBC (Pcombined<5 × 10(-8)) and used pathway analysis to identify JAK-STAT/IL12/IL27 signalling and cytokine-cytokine pathways, for which relevant therapies exist

Namibian deep-sea benthos collection project: history and progress

Despite the wealth of expert fisheries scientists in Namibia, the lack of deep-sea benthic (seafloor) ecologists and taxonomists poses a problem in meeting requirements for monitoring current and proposed impacts in the deep-water environment of Namibia’s Exclusive Economic Zone (EEZ). In light of this issue, a collaboration between benthic ecologists Bronwen Currie (Namibian Ministry for Fisheries and Marine Resources, Namibia), Maria Baker (University of Southampton, UK and co-lead for INDEEP and DOSI – global networks for deep-sea science and policy) and Lisa Levin (Scripps Institution of Oceanography, USA and co-lead for DOSI) resulted in the organisation and convening of a 10-day workshop in April 2016 in Swakopmund, Namibia at the National Marine Information and Research Centre of the Ministry of Fisheries and Marine Resources headquarters. This event attempted to inspire scientists to engage in benthic biodiversity assessment efforts. The workshop considered not only the fundamental principles of benthic ecology but also addressed the main concerns of a variety of deep-sea anthropogenic activities. The event was funded by INDEEP, the International Seabed Authority Endowment Fund and MFMR. Funding enabled participation of 28 individuals, mostly from Namibia but also representatives from Kenya, Madagascar, Mauritania and Angola. Their experience spanned sectors and disciplines, although most were related to fisheries in some way, and included an Executive Director of the Centre of Studies and Development of Fisheries, Senior Fisheries Biologists, Head of Data Management, PhD Students, Fisheries Research Technicians and Research Scientists

Behavioural and physiological adaptations of the bearded goby, a key fish species of the extreme environment of the northern Benguela upwelling

Nutrient-rich, upwelling marine areas with high productivity often produce sediments dominated by organic-rich mud. Here, intense decay processes create hypoxic conditions with high concentrations of hydrogen sulphide and methane in the muddy surface layers. Such environments are inhospitable to most forms of life and those organisms that can survive in these areas tend to be specialists that cope with anoxic or hypoxic conditions, e.g. sulphide-oxidising bacteria and chemolithotrophic bacteria. Surprisingly, during recent acoustic and survey work in the northern Benguela region off the coast of Namibia, it was observed that the bearded goby Sufflogobius bibarbatus spends much of the day on the seabed interacting with the hypoxic and sulphidic mud, making a diel vertical migration (DVM) to spend the night in more oxygenated, but jellyfish-rich waters. We describe a series of experiments that demonstrate physiological and behavioural adaptations that enable the gobies to cope with hypoxia, anoxia and exposure to sulphide for prolonged periods of time. We also observed that the fish burrow directly into the muddy substrate when threatened and that, unlike another fish species common to this area, the horse mackerel Trachurus capensis, the gobies tolerate the presence of jellyfish

Satellite imaging - Massive emissions of toxic gas in the Atlantic

Recurrent eruptions of toxic hydrogen sulphide gas in the waters along the Namibian coast off southwestern Africa have been considered to be local features with only limited ecosystem-scale consequences. But satellite remote sensing has revealed that these naturally occurring events are much more extensive and longer-lasting than previously suspected, and that the resultant hypoxia may last for much longer. The effects on the marine ecology and valuable coastal fisheries of this region are likely to be important