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Larval anchovy and sardine dispersal patterns in South Africa’s exclusive economic zone
Get PDFLagrangian dispersal models are valuable tools for understanding the transport mechanisms and distribution of larvae in space and time. These models primarily use high-quality physical oceanographic data from hydrodynamic ocean models to simulate the advection and connecting pathways of larvae. The paper seeks to achieve the following objectives 1) to establish the dispersal patterns of larval anchovies and sardines spawned in South Africa’s coastal marine protected areas (i.e., inshore of the 200 m isobath), and 2) to assess the impact of model resolution on the dispersal patterns by comparing outputs of a 3-km-grid coastal and regional ocean community model, and the 8-km-grid global ocean physics reanalysis product. We demonstrate that the model yields more structured patterns than sporadic patterns obtained from the global reanalysis. The model shows relatively shorter residence times (i.e., < 5 days) and transport confined to the inshore area of the Agulhas Current. The high variability of dispersals observed off the west coast is attributable to the significant differences in mean kinetic energy between the model and global reanalysis. This finding directly impacts transport and potential connectivity along coastlines: global reanalysis data overestimated local retention and subsequent recruitment variability. Our findings indicate that a model grid size of 3 km or smaller may be more appropriate for studying the dispersal patterns of anchovies and sardines in the South African coastal zone. These findings add to the growing knowledge of the importance of including sub-mesoscale processes in Lagrangian analysis for dispersal studies of coastal species.publishedVersio
Biomass mapping of fjordic cold-water coral reefs reveals distinct functional role of vertical wall habitat
Get PDFFjords provide unique habitats for large cold-water coral (CWC) reefs, typically growing on sills and vertical walls. Fjord reefs are among the most thriving CWC reefs in Norway. Yet, these reefs, especially the wall reefs, are notoriously understudied. Here, we mapped the biomass, total carbon (C) stocks and C turnover (as respiration) of the reef-building coral Lophelia pertusa (syn. Desmophyllum pertusum), and dominant, large CWC reef-associated suspension feeders (the sponges Geodia barretti and Mycale lingua, the CWC Madrepora oculata and the bivalve Acesta excavata) within the Hardangerfjord, Norway. Remotely Operated Vehicle (ROV) recorded videos from wall and sill reefs were used to estimate species-specific biomass. Coupled with high resolution terrain data (2 × 2 m), predictive maps of species biomass were produced using a random forest (RF) model. The resulting biomass data were integrated with species-specific C content and C respiration rates from literature to estimate C stocks and C turnover of wall versus sill reefs. Area-specific results from the RF models reveal that wall reefs had a higher habitat suitability for all species except L. pertusa, which was more dominant on the sills. Accordingly, the wall reefs supported an up to 11 times higher biomass, C stock, and turnover for all species, except for L. pertusa, which had two-fold higher values on the sill reef. As a result, the wall reefs showed a 1.5 to 4.8 times higher total mean C turnover by dominant suspension feeders (all studied species) compared to the sill reefs. With their high C turnover and their presumably wide distribution in Norwegian fjords and globally, benthic wall reef megafauna may have a substantial, but overlooked biomass and functional role within CWC reef systems.publishedVersio
Aquatic connectivity: challenges and solutions in a changing climate
Get PDFThe challenge of managing aquatic connectivity in a changing climate is exacerbated in the presence of additional anthropogenic stressors, social factors, and economic drivers. Here we discuss these issues in the context of structural and functional connectivity for aquatic biodiversity, specifically fish, in both the freshwater and marine realms. We posit that adaptive management strategies that consider shifting baselines and the socio-ecological implications of climate change will be required to achieve management objectives. The role of renewable energy expansion, particularly hydropower, is critically examined for its impact on connectivity. We advocate for strategic spatial planning that incorporates nature-positive solutions, ensuring climate mitigation efforts are harmonized with biodiversity conservation. We underscore the urgency of integrating robust scientific modelling with stakeholder values to define clear, adaptive management objectives. Finally, we call for innovative monitoring and predictive decision-making tools to navigate the uncertainties inherent in a changing climate, with the goal of ensuring the resilience and sustainability of aquatic ecosystems.publishedVersio
In situ infestation of sea trout Salmo trutta with salmon louse Lepeophtheirus salmonis reveals parasite-induced behavioral modifications
Get PDFIn areas with high densities of salmon farming, spillover of the ectoparasitic salmon louse Lepeophtheirus salmonis poses a major threat to wild anadromous salmonids. By combining experimentally salmon louse infestation (mean ± standard deviation = 0.25 ± 0.25 lice g−1 fish) with acoustic telemetry, we studied the behavior of wild first-time migrating sea trout Salmo trutta (n = 58, fork length = 138–204 mm) from late June to September in a marine area with naturally low infestation pressure. We observed that a similar proportion of sea trout from the control and exposed groups returned to fresh water both temporarily and permanently. However, sea trout from the control group spent nearly twice the amount of time in the fjord before first freshwater detection compared to exposed individuals (32 vs. 17 days), and statistical models indicated a dose–response of louse burden on the timing of freshwater return. This effect was combined with evidence of negative impacts of salmon louse burden on overall marine residency. Sea trout predominantly utilized waters within their natal fjord during the marine migration, with exposed fish spending significantly more time close to their home river than sea trout from the control group. In summary, the behavioral modifications caused by salmon lice could reduce individual marine growth, increase long-term mortality, and ultimately harm recruitment at the population level.publishedVersio
The Food Sources in Western Diets Modulate Obesity Development, Insulin Sensitivity, and the Plasma and Cecal Metabolome in Mice
Get PDFScope Dietary constituents modulate development of obesity and type 2 diabetes. The metabolic impact from different food sources in western diets (WD) on obesity development is not fully elucidated. This study aims to identify dietary sources that differentially affect obesity development and the metabolic processes involved. Methods and results Mice were fed isocaloric WDs with protein and fat from different food groups, including egg and dairy, terrestrial meat, game meat, marine, vegetarian, and a mixture of all. This study evaluates development of obesity, glucose tolerance, insulin sensitivity, and plasma and cecal metabolome. WD based on marine or vegetarian food sources protects male mice from obesity development and insulin resistance, whereas meat-based diets promote obesity. The intake of different food sources induces marked differences in the lipid-related plasma metabolome, particularly impacting phosphatidylcholines. Fifty-nine lipid-related plasma metabolites are positively associated with adiposity and a distinct cecal metabolome is found in mice fed a marine diet. Conclusion This study demonstrates differences in obesity development between the food groups. Diet specific metabolomic signatures in plasma and cecum associated with adiposity, where a marine based diet modulates the level of plasma and cecal phosphatidylcholines in addition to preventing obesity development.publishedVersio
Lophelia reefs off North and West Africa–Comparing environment and health
Get PDFThe health status of cold-water coral reefs on the West African coast was investigated with the main objective of obtaining knowledge of the adaptive capacity of Lophelia pertusa to environmental stressors. Three coral sites were studied, in Northern Morocco, in the Morocco/Mauritania region (both in 2020) and, in the Ghana and Ivory coast region (visited in 2012, 2017, and 2019). Area cover of live colonies, explored through underwater videos, was used as an indicator of reef health and compared with the environmental variables: reef position, depth, water mass, temperature, dissolved oxygen concentration (DO), carbonate chemistry (pH, aragonite saturation (ΩAr), macronutrients and particles (visual). For a broader picture of the adaptations presented by Lophelia our results were compared with reefs in contrasting environments. Off Ghana and Mauritania healthy reefs (i.e., having areas with more than 20 % cover of live colonies) were found to reside at DO concentrations between 1.1 and 1.6 ml L−1, in corrosive waters (pH 7.7 and ΩAr 1.0) with high nutrient concentrations. By contrast, the reefs off the North of Morocco, sitting in well-oxygenated waters with oversaturated ΩAr, had no or few live colonies. Our findings together with data from other studies show that Lophelia has a wide tolerance to hypoxia and acidification, and that in relation to climate change increased temperature and silting could pose more serious threats. These findings highlight the importance of continued studies of Lophelia reefs in contrasting environmental conditions to better understand their adaptation potential to climate change-related stressors.publishedVersio
METASEED: a novel approach to full-length 16S rRNA gene reconstruction from short read data
Get PDFBackground With the emergence of Oxford Nanopore technology, now the on-site sequencing of 16S rRNA from environments is available. Due to the error level and structure, the analysis of such data demands some database of reference sequences. However, many taxa from complex and diverse environments, have poor representation in publicly available databases. In this paper, we propose the METASEED pipeline for the reconstruction of full-length 16S sequences from such environments, in order to improve the reference for the subsequent use of on-site sequencing. Results We show that combining high-precision short-read sequencing of both 16S and full metagenome from the same samples allow us to reconstruct high-quality 16S sequences from the more abundant taxa. A significant novelty is the carefully designed collection of metagenome reads that matches the 16S amplicons, based on a combination of uniqueness and abundance. Compared to alternative approaches this produces superior results. Conclusion Our pipeline will facilitate numerous studies associated with various unknown microorganisms, thus allowing the comprehension of the diverse environments. The pipeline is a potential tool in generating a full length 16S rRNA gene database for any environment.publishedVersio
Attraction and avoidance of wild demersal fish and crustaceans to open-net aquaculture pens resolved by baited and towed underwater camera surveys
Get PDFWild gadoids are known to have close associations with open-net fish farms, leading to concerns about changes in natural fish distribution and feeding patterns. However, the nature of the relationships between non-pelagic fish and mobile benthic invertebrates and aquaculture facilities remains poorly documented, even though this group contains widespread commercial North Atlantic species. This study utilizes baited remote and towed underwater video surveys to resolve the ecosystem-level effects of open salmon aquaculture cages and organic enrichment on the spatial structure and relative abundance of demersal fish and crustacean communities. Towed camera surveys were carried out 50 to >600 m downstream of three farms producing finfish in Western Finnmark and four in the Frøya region of Norway. Towed camera surveys were paired with baited remote underwater video surveys at the four Frøya farms. The declining enrichment gradient with distance downstream of the farm cages was confirmed by modeled and observed depositional flux measurements and benthic infaunal community composition. The community structure of wild demersal fish and crustaceans in close association with the seafloor varied with the distance from the aquaculture sites. In addition to the established pattern of the attraction of gadoids, the edible crab (Cancer pagurus) and flatfish (Pleuronectes platessa and Microstomus kitt) showed a preference for areas 10–150 m from farm cages where organically enriched sediments contain a rich food source of opportunistic polychaetes. In contrast, the cuckoo wrasse (Labrus mixtus) and the common hermit crab (Pagurus bernhardus) exhibited higher numbers in locations over 600 m from the farms. Findings show how changes in the benthic food web from aquaculture enrichment can affect the spatial distribution of poorly studied but commercially important fish and crustaceans. Such changes in distribution can impact the availability of these species to coastal fisheries, especially in dense aquaculture regions.publishedVersio
First Report of ‘Soft Flesh’ Induced by the Parasite Kudoa thyrsites (Myxosporea) in Commercial Codfish From Norway
Get PDFKudoa thyrsites is a myxosporean parasite that infects the skeletal muscle of various teleost fish species globally. Severe infections lead to ‘soft flesh’ in fish fillets, resulting in food spoilage and subsequent discard. While K. thyrsites has previously been identified in migratory Atlantic mackerel in the northern Northeast Atlantic Ocean, it has not been observed in resident or farmed fish species in Norwegian waters until now. This study presents the first evidence of K. thyrsites infection and the associated ‘soft flesh’ condition in resident commercially important gadoid species from Norwegian waters, including Norwegian coastal cod (NCC), Northeast Arctic cod (NEA) and tusk. Molecular analyses confirmed the parasitic infection in ‘soft flesh’-affected fish sampled from multiple coastal locations in Norway. The life cycle of Kudoa remains unknown but likely involves an alternating annelid host as in other myxosporeans. These findings in resident hosts suggest that the parasite completes its life cycle also at higher latitudes, in northern Norway. Consequently, there is a risk for the Norwegian fishing industry, as the effect of the parasite on fish fillet texture can occasionally occur and impact both consumer acceptance and industry revenues.publishedVersio