Maintenance of Genetic Diversity: Challenges for Management of Marine Diversity

There are three general classes of threat to biodiversity at the gene level: 1) extinction, which result in complete and irreversible loss of genes; 2) hybridization, which may cause re-arrangement of co-adapted genes and loss of adaptability to local conditions, and 3) reduction of genetic variability within populations. While extinction avoidance is a fundamental management objective and hybridization can usually be dismissed in marine populations, the reduction of genetic variability within populations is a plausible threat and can occur in two ways. First, a decrease in population size may result in inbreeding. Normally, marine fish have very large population sizes, and commercial extinction is likely to occur long before populations are reduced to the level required for losses of genetic diversity due to inbreeding. However, when populations are very severely over-fished to small numbers, concerns associated with small population sizes and disruptions of migration between populations may become prominent. In particular, undetected populations within management units may be fished to this level before the situation is properly evaluated and remedied. Second, a reduction of genetic variability within populations may occur in a directed way, due to, e.g., selective fishing. Fishing is expected to generate selection on life history traits such as age and size at maturation; changes in life history traits influence the dynamics of fish populations, energy flows in the ecosystem, and ultimately, sustainable yield. We discuss management objectives designed to ameliorate genetic complications associated with small population size and fisheries-induced selection, and outline a management approach that may be useful when developing advice for maintaining genetic diversity

The Use of Density Analyses to Delineate Sponge Grounds and Other Benthic VMEs from Trawl Survey Data

b

Vulnerable Marine Ecosystems Dominated by Deep-Water Corals and Sponges in the NAFO Convention Area

Many species of deep-water corals and sponges are important structure forming species in deep-sea environments, however not all coral and sponges meet the criteria associated with vulnerability. Here we review the taxa living within the NAFO regulatory area (NRA) and provide literature supporting their consideration as components of vulnerable marine ecosystems (VMEs). For the sponges, we present the first map of their location in the NRA, as determined from fisheries bycatch information

Development of Encounter Protocols and Assessment of Significant Adverse Impact by Bottom Trawling for Sponge Grounds and Sea Pen Fields in the NAFO Regulatory Area

We provide a scientific basis for recommending commercial encounter protocols for sponges and sea pens in the NRA. For each we provide an assessment of significant adverse impact of bottom trawling taking into account published and new data on gear efficiency and selectivity, incidental mortality and recoverability. The proportion of VMS trawls in 2010 that would be impacted by lowering the current thresholds is estimated following previously established methods. Approaches to move-on rules are also considered

Role of Astrophorina sponges (Demospongiae) in food-web interactions at the Flemish Cap (NW Atlantic)

Deep-sea sponges are important contributors to carbon and nitrogen cycling due to their large filtration capacity. Species of the suborder Astrophorina form dense sponge grounds in the North Atlantic, where they serve as prey for spongivores, but also have non-trophic interactions with commensal epi- and endobionts. At the Flemish Cap (NW Atlantic), Astrophorina sponges are present in 4 previously described deep-sea epifaunal assemblages: the deep-sea coral assemblage, lower slope assemblages 1 and 2, and the deep-sea sponge assemblage. To investigate their role in trophic and non-trophic interactions at the Flemish Cap, we developed trophic and non-trophic interaction web models for each of the 4 faunal assemblages using the published literature. By excluding the sponges from the models, we estimated how many trophic, and facultative and obligatory non-trophic, interactions would be lost, and how this removal affected food-web properties (number of compartments, links, link density, and connectance). Astrophorina sponges were mostly linked via facultative non-trophic interactions to 59, 58, 84, and 90 compartments in the deep-sea coral, the lower slope 1 and 2, and the deep-sea sponge assemblages, respectively. Direct trophic interactions only existed with Syllidae, Echinasteridae, and Pterasteridae. Astrophorina sponges were considered highest impact taxa in all faunal assemblages and, together with sea pens, they were identified as structural species/habitat formers and foundation species in the deep-sea coral and deep-sea sponge habitat. Hence, even less abundant, or non-representative (indicator), species can be important for food-web integrity via trophic and non-trophic interactions

Microbial strategies for survival in the glass sponge Vazella pourtalesii

Few studies have thus far explored the microbiomes of glass sponges (Hexactinellida). The present study seeks to elucidate the composition of the microbiota associated with the glass sponge Vazella pourtalesii and the functional strategies of the main symbionts. We combined microscopic approaches with metagenome-guided microbial genome reconstruction and amplicon community profiling towards this goal. Microscopic imaging revealed that the host and microbial cells appeared within dense biomass patches that are presumably syncytial tissue aggregates. Based on abundances in amplicon libraries and metagenomic data, SAR324 bacteria, Crenarchaeota, Patescibacteria and Nanoarchaeota were identified as abundant members of the V. pourtalesii microbiome and their genomic potentials were thus analyzed in detail. A general pattern emerged in that the V. pourtalesii symbionts had very small genome sizes in the range of 0.5-2.2 Mb and low GC contents, even below those of seawater relatives. Based on functional analyses of metagenome-assembled genomes (MAGs), we propose two major microbial strategies: the “givers”, namely Crenarchaeota and SAR324, heterotrophs and facultative anaerobes, produce and partly secrete all required amino acids and vitamins. The “takers”, Nanoarchaeota and Patescibacteria, are anaerobes with reduced genomes that tap into the microbial community for resources, e.g., lipids and DNA, likely using pili-like structures. We posit that the existence of microbial cells in sponge syncytia together with the low-oxygen conditions in the seawater environment are factors that shape the unique compositional and functional properties of the microbial community associated with V. pourtalesii . Importance: We investigated the microbial community of V. pourtalesii that forms globally unique, monospecific sponge grounds under low-oxygen conditions on the Scotian Shelf, where it plays a key role for its vulnerable ecosystem. The microbial community was found to be concentrated within biomass patches and is dominated by small cells (<1 μm). MAG analyses showed consistently small genome sizes and low GC contents, which is unusual in comparison to known sponge symbionts. These properties as well as the (facultatively) anaerobic metabolism and a high degree of interdependence between the dominant symbionts regarding amino acid and vitamin synthesis are likely adaptations to the unique conditions within the syncytial tissue of their hexactinellid host and the low-oxygen environment

Layers Utilized by an ArcGIS Model to Approximate Commercial Coral and Sponge By-catch in the NAFO Regulatory Area

This report specifically addresses Fisheries Commission Request #16: "Implement and/or further refine the existing GIS simulation/modelling framework, in conjunction with the VMS data supplied by the NAFO Secretariat ...", brought forth in the Fisheries Commission 33rd Annual Meeting Report (NAFO, 2011a). Data layers utilized by the model as well as their various means of construction are described in detail including the generation of NAFO VMS trawl lines. These VMS trawl line data were used to better understand fishing behaviour and also generate a new standard trawl length (13.8 nm) to be utilized by trawl simulations. The justification for utilizing just the Spain/EU research trawl by-catch dataset instead of the combined Canada/Spain/EU dataset for the production of higher resolution sponge and sea pen biomass surfaces is also made. It is demonstrated how this high resolution (5x5 km cell grid) Spain/EU data biomass layer could be utilized with 2000 randomly placed and oriented 13.8 nm simulation trawls to generate by-catch values, organized by thresholds, to capture the distributional extent of high concentration sponge and sea pen areas. This serves as the basis for a kernel density polygon analysis that calculates a commercial sponge and sea pen encounter threshold (Kenchington et al., 2011). Finally, using the Spain/EU only high resolution biomass surface, by-catch output from VMS trawls and their simulated 13.8 nm standard trawl line counterparts are compared

Report of the ICES\NAFO Joint Working Group on Deep-water Ecology (WGDEC), 11–15 March 2013, Floedevigen, Norway.

On 11 February 2013, the joint ICES/NAFO WGDEC, chaired by Francis Neat (UK) and attended by ten members met at the Institute for Marine Research in Floedevi-gen, Norway to consider the terms of reference (ToR) listed in Section 2. WGDEC was requested to update all records of deep-water vulnerable marine eco-systems (VMEs) in the North Atlantic. New data from a range of sources including multibeam echosounder surveys, fisheries surveys, habitat modelling and seabed imagery surveys was provided. For several areas across the North Atlantic, WGDEC makes recommendations for areas to be closed to bottom fisheries for the purposes of conservation of VMEs

Advances in the Assessment of Habitat Fragmentation and Protection in the NAFO Regulatory Area

NAFO has used kernel density analyses to identify VMEs dominated by large-sized sponges, sea pens, small and large gorgonian corals, erect bryozoans, sea squirts (Boltenia ovifera), and black corals. That analysis generates polygons of significant concentrations of biomass for each VME indicator which are spread across the spatial domain of the NAFO fishing footprint. There is potential for bottom contact fishing to induce changes in both the amount and configuration of habitat (e.g., decreased polygon size, increased polygon isolation, and increased edge area) through direct and indirect impacts, and it is unknown to what degree such changes may already have taken place given the long fishing history of the area. In the Report of the 13th Meeting of the NAFO Scientific Council Working Group on Ecosystem Science and Assessment (WGE-ESA), preliminary work on assessing and monitoring habitat fragmentation was presented. Here we continue that work by recalculating the indices after removing connections that are not identified through particle tracking models. We have reanalyzed the nearest neighbour distances and PX, a proximity index, for the VME polygons noted above, and for the new closed areas that will come into effect 1 January 2022. We show that PX when applied to the new closures appears sensitive to their spatial configuration which bodes will for the ability of this index to identify habitat fragmentation in the future, brought about through fishing activities and/or natural disturbances.Versión del edito