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Groundtruther: A QGIS plug-in for seafloor characterization
Get PDFThis work focuses on developing a software system for concurrently analyzing co-located multibeam echo sounder (MBES) datasets and seafloor imagery, fulfilling the need for a unified seafloor data exploration and analysis platform. The system comprises a graphical user interface where image browsing and geospatial data are linked and several toolboxes for extracting backscatter distribution, its angular response, and bathymetric derivatives to ultimately build detailed quantitative reports. The overall objective is to provide an efficient means of understanding the relationships between morphology, backscatter, and the observed biota and, thus, understanding the relationship between the physical and ecological elements of the seafloor. In addition, Groundtruther provides new ways to interpret remotely sensed information derived from MBES and aid the development of spatial distribution models. Furthermore, it could lead to the enrichment of ground-truth databases used to develop formal geophysical models that link acoustic backscatter observations to intrinsic properties of the seafloor.publishedVersio
Panel-based Assessment of Ecosystem Condition of Norwegian Barents Sea Shelf Ecosystems
Get PDFThe System for Assessment of Ecological Condition, coordinated by the Norwegian Environment Agency, is intended to form the foundation for evidence-based assessments of the ecological condition of Norwegian terrestrial and marine ecosystems not covered by the EU Water Framework Directive. The reference condition is defined as “intact ecosystems”, i.e., a condition that is largely unimpacted by modern industrial anthropogenic activities. An ecosystem in good ecological condition is defined as a system that does not deviate substantially from this reference condition in structure, functions or productivity. This means that, in practice, what is assessed here is the extent to which an ecosystem is impacted by anthropogenic drivers. This report describes the first operational assessment of the ecological condition of Norwegian Arctic and Sub-Arctic marine shelf ecosystems in the Barents Sea. The assessment method employed is the Panel-based Assessment of Ecosystem Condition (PAEC1), and the current assessment has considered to what extent the Barents Sea shelf ecosystems deviate from the reference condition2 by evaluating change trajectories.Panel-based Assessment of Ecosystem Condition of Norwegian Barents Sea Shelf EcosystemspublishedVersio
Hydro-acoustic classification and abundance estimation of mesopelagic fish in deep scattering layers (DSL) of the Indian Ocean
Get PDFDeep scattering layers (DSL) in oligotrophic systems are typically comprised of a variety of coexisting organisms, including fish, zooplankton, jellyfish, and squid, and hence there is uncertainty about the proportion of the acoustic backscatter in these layers that can be attributed to mesopelagic fish. Here, acoustic targets were classified using a multi-frequency acoustic classification algorithm based on data collected in the Indian Ocean at 18, 38, 70, and 120 kHz during three acoustic surveys in 2018. Frequency-dependent backscattering strength information (∆Sv) was extracted from acoustic data that coincided with trawl hauls dominated by mesopelagic fish. Five ∆Sv frequency pairs were used to separate the acoustic backscattering into three broad scattering categories, i.e. mesopelagic fish, crustacean-like/tunicates, and squids/others. Results indicated that the DSL is highly diverse and dominated by mesopelagic fish, with average densities at a regional scale ranging from 12.0 (±10.9) to 26.0 (±21.7) g m−2, and proportions of the acoustic backscatter attributed to mesopelagic fish ranging from 0.5 to 0.7. These estimates are generally lower than previously estimated for other regions of the Indian Ocean. The situation may well be similar elsewhere, particularly in oligotrophic systems, with potential ramifications for global mesopelagic fish biomass estimates.publishedVersio
Salinity induced changes in the progression of water, ion and nutrient fluxes along the gastrointestinal tract of Atlantic salmon smolt (Salmo salar)
Get PDFWater ingestion in fish increases with both water salinity and feeding. However, it is unclear whether, during feeding, water ingestion is intended to aid chyme liquefaction in the stomach or to maintain the osmotic homeostasis within the body of the fish. We investigated the effects of increasing water salinity (0, 10, 20, 35 ppt) on the progression of water, ion and nutrient fluxes in the gastrointestinal tract of Atlantic salmon smolt (Salmo salar) fed a commercial-like diet. Furthermore, the effect of water salinity on blood pH, plasma osmolality and ions was investigated. The experiment lasted for 8 weeks. Chyme was collected from 4 gastrointestinal tract (GIT) segments (stomach, proximal, middle and distal intestine) and analysed for dry matter, pH, osmolality, crude protein and mineral content. Water and electrolyte fluxes, kinetic of digestion and faecal digestibility were measured using yttrium oxide (Y2O3) as an inert marker. We found that between 0 and 35 ppt chyme dry matter decreased by 1.6% and 4.8% in the stomach and proximal intestine, respectively. Chyme pH was not affected by water salinity in the stomach, but it increased linearly (p < 0.001) with salinity in all intestinal segments. Chymeosmolality increased linearly (p < 0.001) with salinity in the stomach and it decreased in all intestinal segments. Water fluxes were similar among salinities in the stomach, but they increased nearly fivefold (6.2 versus 27.3 ml g− 1 ingested DM) in the proximal intestine between 0 ppt and 35 ppt. An efflux of monovalent ions (Na+ and K+) increased linearly (p < 0.001) with salinity in the proximal intestine. An efflux of divalent ions (Ca2+ and Mg2+) increased curvilinearly (p < 0.001) with salinity in the middle intestine. Plasma osmolality and ion levels increased with salinity. Crude protein digestibility and protease activity decreased significantly with water salinity in the intestine. Our study highlights that when Atlantic salmon moves from freshwater to higher water salinity environments, drinking of saltwater does not interfere with hydration of feed in the stomach, but instead bypasses to the proximal intestine to aid in osmoregulatory water uptake. Therefore, we suggest that water ingestion in seawater fish is intended for osmoregulation rather than to aid digestion by liquefying chyme in the stomach.publishedVersio
Efficient and reliable methods for estimating the abundance of keystone coastal macrofauna over large spatial scales
Get PDFCoastal bivalves are important ecosystem engineers, and identifying critical habitats can enhance conservation outcomes for threated keystone species as well as determining hotspots for invasive species. As early action is more efficient in both conservation and mitigation of species invasions, efficient and reliable tools for mapping and monitoring species over large scales are essential. We assessed the reliability and efficiency of towed video and quadrat sampling for estimating the abundance of three keystone macrofaunal bivalve species. To assess reliability, we compared the measured density based on each of the two methods to the “true” density estimated by manually surveying an entire transect. We found that both the video and quadrat method caused underestimation of the density of bivalves, but that the amount of underestimation was comparable, and further that both methods took substantially less time than surveying an entire transect manually. The video method underestimated the abundance of Pacific oysters (Magallana gigas), European flat oysters (Ostrea edulis), and blue mussels (Mytilus spp.) by 23%, 24%, and 16%, respectively. The causes of underestimation for the two oyster species were bivalves grouped in clusters, large amounts of small individuals, and generally higher abundances. While Mytilus spp. were underestimated overall, here observer experience was important, with inexperienced observers overestimating and experienced observers underestimating. Our study found both methods to be reliable and efficient for estimating the abundance of three keystone macrofaunal species, suggesting their potential applicability to other sessile or slow-moving species. We propose that these methods, due to their efficiency, can advance scientific knowledge and enhance conservation outcomes by establishing population baselines, assessing trends over time, and identifying and protecting critical habitats.publishedVersio
Aquaculture sludge as feed for black soldier fly: Transfer of chemical and biological contaminants and nutrients
Get PDFAquaculture sludge (uneaten feed and faeces) is nutrient rich and has potential as feed for insects. The aim of this study was to investigate the transfer of chemical and biological contaminants, as well as nutrients, from aquaculture sludge to black soldier fly larvae. The larvae were reared on a sludge mixture made of different sludges collected from Norwegian freshwater salmonid facilities. The sludge was spiked with four common salmon pathogens: Infectious Pancreatic Necrosis Virus, Infectious Salmon Anemia virus, Yersinia ruckeri or Mycobacterium salmoniphilum. During the 15 days of growth on sludge, the black soldier fly larvae accumulated valuable nutrients including protein, fat, eicosapentaenoic acid, iron, manganese, zinc and selenium. The larvae also accumulated undesirable substances including cadmium, mercury, dioxins and polychlorinated biphenyls. The concentrations of dioxins exceeded the EU maximum level set for animal feed. None of the salmon pathogens that were spiked to the sludge were detected in the black soldier fly larvae. This study reports low risk of transfer of salmon pathogens from sludge to insect larvae, and showed that the transfer of heavy metals, minerals and metalloids are in accordance with earlier studies. The large variations in levels of heavy metals between batches of sludge can cause levels in BSF exceeding the EU maximum levels, and thus indicate a need for monitoring of the proposed value chain. The transfer of dioxins from sludge to insects, reported for the first time in this paper, would be of special interest for future research, with special focus on risk mitigation.publishedVersio
On the Retention of Cod Early Life Stages Spawned at Jan Mayen
Get PDFThe Jan Mayen shelf has recently been identified as a spawning area for cod (Gadus morhua). Genetic analyses and otolith types of adult cod caught in the Jan Mayen area show that they are of mixed origin, from both Iceland and the Barents Sea. However, they are genetically different from both stocks indicating the possibility of a cod stock around Jan Mayen. Motivated by this, we investigate the potential for eggs and larvae of cod to stay behind at Jan Mayen after spawning, which would be a requirement for having a self-sustained stock. This is done using a numerical model for larval drift and growth, similarly to what has been done for other cod stocks. Using the modelled drift, we compare the proportion of larvae retained in different years to the strength of year classes as indicated by fisheries data. We find that even if most individuals are transported away from Jan Mayen, there are still some years where a significant proportion (more than 20%) of the larvae remains at the time of settlement in October–November. However, the year-to-year variability is large, with almost no individuals remaining in certain years. Our results suggest that aggregated over years, the amount of larvae that reach the age of bottom settlement on the Jan Mayen shelf area could be sufficient to give a potential for a self-sustained cod population. In addition, we find that the main drift direction away from Jan Mayen is southwest towards East Greenland.publishedVersio
Swarm and UNOISE outperform DADA2 and Deblur for denoising high-diversity marine seafloor samples
Get PDFThe performance of sequence variant resolution analytic tools for metabarcoding has not yet been adequately benchmarked for high-diversity environmental samples. We therefore evaluated the sequence variant tools DADA2, Deblur, Swarm, and UNOISE, using high-diversity seafloor samples, resulting in comparisons of 1800 sequence variant tables. The evaluation was based on 30 sediment grab samples, for which 3 replica samples were collected. Each replica sample was extracted using 5 common DNA extraction kits, resulting in 450 DNA extracts which were 16S rRNA gene sequenced (V3–V4), using Illumina. Assessments included variation across replica samples, extraction kits, and denoising methods, in addition to applying prior knowledge about alpha diversity correlations toward the cosmopolitan marine archaeon Nitrosopumilus with high diversity and the sulfide oxidizing Sulfurovum with low diversity. DADA2 displayed the highest variance between replicates (Manhattan distance 1.14), while Swarm showed the lowest variance (Manhattan distance 0.93). For the analysis based on prior biological knowledge, UNOISE displayed the highest alpha diversity (Simpson’s D) correlation toward Nitrosopumilus (Spearman rho = 0.85), while DADA2 showed the lowest (Spearman rho = 0.10). Deblur completely eliminated Nitrosopumilus from the dataset. For Sulfurovum, on the other hand, all the methods showed comparable results. In conclusion, our evaluations show that Swarm and UNOISE performed better than DADA2 and Deblur for high-diversity seafloor samples.publishedVersio
Answering the key stakeholder questions about the impact of offshore wind farms on marine life using hypothesis testing to inform targeted monitoring
Get PDFStakeholders need scientific advice on the environmental impacts of offshore wind (OW) before the facilities are installed. The utility of conventional environmental monitoring methods as a basis for forecasting OW impacts is limited because they do not explain the causes of the observed effects. We propose a multistep approach, based on process-oriented hypothesis testing, targeted monitoring and numerical modeling, to answer key stakeholder questions about planning an OW facility: Q1—Where do we place future OW farms so that impacts on the ecosystem are minimized? Q2—Which species and ecosystem processes will be impacted and to what degree? Q3—Can we mitigate impacts and, if so, how? and Q4—What are the risks of placing an OW facility in one location vs. another? Hypothesis testing can be used to assess impacts of OW facilities on target species-ecological process. This knowledge is transferable and is broadly applicable, a priori, to assess suitable locations for OW (Q1). Hypothesis testing can be combined with monitoring methods to guide targeted monitoring. The knowledge generated can identify the species/habitats at risk (Q2), help selecting/developing mitigation measures (Q3), and be used as input parameters for models to forecast OW impacts at a large spatial scale (Q1; Q4).Answering the key stakeholder questions about the impact of offshore wind farms on marine life using hypothesis testing to inform targeted monitoringpublishedVersio
Four new goatfishes (Upeneus, Mullidae, Mulliformes) from the Asian Indo-Pacific with a list of valid goatfish species and remarks on goatfish diversity
Get PDFBased on a large comparative data set available from recent studies of goatfish species of the genus Upeneus (Mullidae, Mulliformes) with seven spines in the first dorsal fin, four new species from the area of the Asian Indo-Pacific are described. Initial search for and discovery of the new species was greatly assisted by the recognition of several subgroups within two rather large taxonomic species groups, the pori and the japonicus groups, each consisting of nine previously described species. Two of the new species, Upeneus aurorae n. sp. from Luzon, Philippines, and U. huan n. sp. from Central Vietnam (W Pacific), are characterized by relatively low gill-raker counts, while U. brevignathus n. sp. from off SE Yemen (NW Indian Ocean) has high gill-raker counts. All three species share the typical characteristics of the pori-species group such as height of first dorsal fin decreasing proportionally, pectoral fins shorter or of similar length as pelvic fins, oblique bars on lower caudal-fin lobe present and white, rose-whitish or pale-red barbels in fresh and live fish. The fourth new species, U. andamanensis n. sp. from the Andaman Islands (NE Indian Ocean), mostly resembles U. guttatus and two other species of the japonicus-species group, which all belong to a subgroup characterized by the first dorsal fin being relatively high with subsequent fin elements decreasing disproportionally in height. While no fresh colour information is available for U. brevignathus n. sp. and U. andamanensis n. sp., each of them can be clearly distinguished morphologically and by preserved colour from the most similar species. A list of all valid goatfish species is included, with English common names and remarks to clarify validity judgments. The results are discussed with respect to the usefulness of using taxonomic species groupings for facilitating detection of new species and other purposes in continuing studies of the species diversity of goatfishes.publishedVersio