Estimation of glacial meltwater discharge into Svalbard coastal waters. Oceanologia 39

Abstract During the summer expeditions of r/v 'Oceania' in 1995'Oceania' in -1996, oceanographic investigations comprising CTD profiling and suspension measurements were conducted in Svalbard fjords and shelf waters. The freshwater volume was estimated independently from the salinity drop as compared with the assumed background salinity and from the distribution of mineral suspension density in surface waters. Preliminary calculations of the instantaneous freshwater volume based on the distribution of suspended matter (at depths of < 150 m) yielded a figure of 80 km 3 in Svalbard coastal waters in summer. Values for Hornsund and Kongsfjord ranged from 0.4 to 0.7 km 3 of freshwater at the height of summer. This corresponds well with glaciological estimations, which give an annual discharge of 14.6 to 27.5 km 3 of freshwater for Svalbard. The glacial discharge is estimated to make up some 42% of the freshwater budget of Svalbard shelf waters, the remainder being derived from Barents Sea Arctic waters of reduced salinity

Replicated anthropogenic hybridisations reveal parallel patterns of admixture in marine mussels.

Human-mediated transport creates secondary contacts between genetically differentiated lineages, bringing new opportunities for gene exchange. When similar introductions occur in different places, they provide informally replicated experiments for studying hybridisation. We here examined 4,279 Mytilus mussels, sampled in Europe and genotyped with 77 ancestry-informative markers. We identified a type of introduced mussels, called "dock mussels," associated with port habitats and displaying a particular genetic signal of admixture between M. edulis and the Mediterranean lineage of M. galloprovincialis. These mussels exhibit similarities in their ancestry compositions, regardless of the local native genetic backgrounds and the distance separating colonised ports. We observed fine-scale genetic shifts at the port entrance, at scales below natural dispersal distance. Such sharp clines do not fit with migration-selection tension zone models, and instead suggest habitat choice and early-stage adaptation to the port environment, possibly coupled with connectivity barriers. Variations in the spread and admixture patterns of dock mussels seem to be influenced by the local native genetic backgrounds encountered. We next examined departures from the average admixture rate at different loci, and compared human-mediated admixture events, to naturally admixed populations and experimental crosses. When the same M. galloprovincialis background was involved, positive correlations in the departures of loci across locations were found; but when different backgrounds were involved, no or negative correlations were observed. While some observed positive correlations might be best explained by a shared history and saltatory colonisation, others are likely produced by parallel selective events. Altogether, genome-wide effect of admixture seems repeatable and more dependent on genetic background than environmental context. Our results pave the way towards further genomic analyses of admixture, and monitoring of the spread of dock mussels both at large and at fine spacial scales.ANR Project HySea (ANR-12-BSV7-0011); Russian Science Foundation project N°19-74-2002

Structure of bryozoan communities in an Antarctic glacial fjord (Admiralty Bay, South Shetlands)

Bryozoans are among the most important groups of the Southern Ocean benthic macrofauna, both in terms of species richness and abundance. However, there is a considerable lack of ecological research focused on their distribution patterns and species richness on smaller scale, especially in the soft bottom habitats of Antarctic glacial fjords. The aim of this study was to describe those patterns in the Admiralty Bay. Forty-nine Van Veen grab samples were collected at the depth range from 15 to 265 m, in the summer season of 1979/1980, at three sites distributed along the main axis of the fjord. Among 53 identified species of bryozoans, 32 were recorded in the Admiralty Bay for the first time. The most common and abundant species were Himantozoum antarcticum, Inversiula nutrix and Nematoflustra flagellata. Genera such as Arachnopusia, Cellarinella and Osthimosia were the most speciose taxa. It was demonstrated that depth was important for the distribution of the bryozoans. More than half of the recorded species were found only below 70 m. An influence of glacial disturbance was reflected in the dominance structure of colony growth-forms. The inner region of the fjord was dominated almost entirely by encrusting species, while the diversity of bryozoan growth-forms in less disturbed areas was much higher. In those sites the highest percentage of branched, tuft like species represented by buguliform and flustriform zoaria was observed.The study was supported by a grant of Polish Ministry of Science and Higher Education No. 51/N-IPY/2007/0 as well as Census of Antarctic Marine Life Project. Krzysztof Pabis was also partially supported by University of Lodz internal funds. This research was also supported by the Polish Geological Institute-National Research Institute during the realization of the project numbered 40.2900.0903.18.0 titled “Bryozoan assemblage of Admiralty Bay—richness, diversity and abundance.” Urszula Hara is deeply grateful to Leszek Giro (Micro-area Analyses Laboratory at the Polish Geological Institute-National Research Institute, Warsaw), for providing SEM assistance during the project. We also want to thank two anonymous reviewers for their suggestions that helped us improve this article. Thanks are also due to Magdalena Błażewicz-Paszkowycz for language correction and polishing the final version of the manuscript