Zooplankton sound scattering layers in North Norway fjords : interactions between fish and krill shoals in a winter situation in Ullsfjorden and Øksfjorden

Aspects of the inter-relationship of krill Sound Scattering Layers (SSLs) and fish were examined in Ullsfjorden and Øksfjorden, northern Norway from 2 - 8 February 1980. Diel changes in the depth distribution and biomass of krill (Euphausiacea) were compared with the depth distribution and abundance of gadoid fish using a pelagic capelin trawl, 38 and 120 kHz echosounders, and a digital echointegrator. Krill underwent vertical migrations from the surface at night to the fjord bottom at mid-day. A significant power curve relationship was found when catches of krill in the pelagic trawl (l·trawl h-1) were compared with volume backscattering (dB m-3) at 120 kHz, indicating that krill biomass can be reliably estimated using acoustic techniques. Krill were the dominant food item of fish caught with the pelagic trawl in the SSLs. Fish were nevertheless rare in these krill SSLs; the majority congregated under them, probably feeding extensively at their periphery. Interactions between krill and pelagic feeding gadoids in north Norwegian fjords are examined

A cross-ecosystem comparison of temporal variability in recruitment of functionally analogous fish stocks

As part of the international MENU collaboration, variability in temporal patterns of recruitment and spawning stock were compared among functionally analogous species from four marine ecosystems including the Gulf of Maine/Georges Bank, the Norwegian/Barents Seas, the eastern Bering Sea and the Gulf of Alaska. Variability was characterized by calculating coefficients of variation for each time series and by representing the time series as anomalies. Patterns of synchrony and asynchrony in recruitment and spawning stock indices were examined among and between ecosystems and related to observed patterns in biophysical properties (e.g. local trophodynamics, local hydrography and large scale climate indices) using a wide range of time series analyses, autocorrelation corrections, autoregressive processes, and multivariate cross-correlation analyses. Of all the commonalities, the relatively similar cross-ecosystem and within-species magnitude of variation was most notable. Of all the differences, the timing of high or low recruitment years across both species and ecosystems was most notable. However, many of the peaks in these indices of recruitment were synchronous across ecosystems for functionally analogous species. Yet the relationships (or lack thereof) between recruitment anomalies and key biophysical properties demonstrated that no one factor consistently caused large recruitment events. Our observations also suggested that there was no routine and common set of factors that influences recruitment; often multiple factors were of similar relative prominence. This work demonstrates that commonalities and synchronies in recruitment fluctuations can be found across geographically very distant ecosystems, but biophysical causes of the fluctuations are difficult to partition. Keywords: Ecosystem, recruitment, trophodynamics, variation

Microsatellite markers for the Arctic copepod Calanus glacialis and cross-amplification with C. finmarchicus

Calanus glacialis is a major component of Arctic zooplankton and a keystone species in Arctic marine ecosystems. Due to the observed climate warming, its numbers are being reduced to the advantage of a sibling Atlantic species Calanus finmarchicus. We developed and characterized the first set of microsatellite markers in this species to investigate its population genetic structure and dispersal capabilities. Nine polymorphic loci displayed an average of 7.3 alleles (range between 2 and 13) and the levels of expected heterozygosity ranged from 0.039 to 0.806. These provide a valuable tool to understand present connectivity patterns across Arctic regions, look for signatures of past climate effects and predict the response to future climate-driven environmental changes. Additionally, due to the cross-amplification with C. finmarchicus, the markers can be used to discriminate between these sibling species.National Science Centre, Poland [2011/03/B/NZ8/02876]; FCT, Portugal [PTDC/MAR/72630/2006]; EU FP7 Project ATP [226248]; European Community (ASSEMBLE-MARINE) [227799]info:eu-repo/semantics/publishedVersio

A comparison of community and trophic structure in five marine ecosystems based on energy budgets and system metrics

As part of the international MENU collaboration, energy budget models for five marine ecosystems were compared to identify differences and similarities in trophic and community characteristics across ecosystems. We examined the Gulf of Maine and Georges Bank in the Northwest Atlantic Ocean, the combined Norwegian/Barents Seas in the Northeast Atlantic Ocean, and the eastern Bering Sea and the Gulf of Alaska in the Northeast Pacific Ocean. Comparable energy budgets were constructed for each ecosystem by aggregating information for similar species groups into consistent functional groups across all five ecosystems. Several ecosystem metrics (including functional group production, consumption, and biomass ratios, ABC curves, cumulative biomass, food web macrodescriptors, and network metrics) were examined across the ecosystems. The comparative approach clearly identified data gaps for each ecosystem, an important outcome of this work. Commonalities across the ecosystems included overall high primary production and energy flow at low trophic levels, high production and consumption by carnivorous zooplankton, and similar proportions of apex predator to lower trophic level biomass. Major differences included distinct biomass ratios of pelagic to demersal fish, ranging from highest in the Norwegian/Barents ecosystem to lowest in the Alaskan systems, and notable gradients in primary production per unit area, highest in the Alaskan and Georges Bank/Gulf of Maine ecosystems, and lowest in the Norwegian ecosystems. While comparing a disparate group of organisms across a wide range of marine ecosystems is challenging, this work demonstrates that standardized metrics both elucidate properties common to marine ecosystems and identify key distinctions for fishery management

Diel vertical migration of Arctic zooplankton during the polar night

High-latitude environments show extreme seasonal variation in physical and biological variables. The classic paradigm of Arctic marine ecosystems holds that most biological processes slow down or cease during the polar night. One key process that is generally assumed to cease during winter is diel vertical migration (DVM) of zooplankton. DVM constitutes the largest synchronized movement of biomass on the planet, and is of paramount importance for marine ecosystem function and carbon cycling. Here we present acoustic data that demonstrate a synchronized DVM behaviour of zooplankton that continues throughout the Arctic winter, in both open and ice-covered waters. We argue that even during the polar night, DVM is regulated by diel variations in solar and lunar illumination, which are at intensities far below the threshold of human perception. We also demonstrate that winter DVM is stronger in open waters compared with ice-covered waters. This suggests that the biologically mediated vertical flux of carbon will increase if there is a continued retreat of the Arctic winter sea ice cover

Model-informed classification of broadband acoustic backscatter from zooplankton in an in situ mesocosm

Funding: The fieldwork was registered in the Research in Svalbard database (RiS ID 11578). Fieldwork and research were financed by Arctic Field Grant Project AZKABAN-light (Norwegian Research Council project no. 322 332), Deep Impact (Norwegian Research Council project no. 300 333), Deeper Impact (Norwegian Research Council project no. 329 305), Marine Alliance for Science and Technology in Scotland (MASTS), the Ocean Frontier Institute (SCORE grant no. HR09011), and Glider Phase II financed by ConocoPhillips Skandinavia AS. Geir Pedersen’s participation was co-funded by CRIMAC (Norwegian Research Council project no. 309 512). Maxime Geoffroy was financially supported by the Ocean Frontier Institute of the Canada First Research Excellence Fund, the Natural Sciences and Engineering Research Council Discovery Grant Programme, the ArcticNet Network of Centres of Excellence Canada, the Research Council of Norway Grant Deep Impact, and the Fisheries and Oceans Canada through the Atlantic Fisheries Fund.Classification of zooplankton to species with broadband echosounder data could increase the taxonomic resolution of acoustic surveys and reduce the dependence on net and trawl samples for ‘ground truthing’. Supervised classification with broadband echosounder data is limited by the acquisition of validated data required to train machine learning algorithms (‘classifiers’). We tested the hypothesis that acoustic scattering models could be used to train classifiers for remote classification of zooplankton. Three classifiers were trained with data from scattering models of four Arctic zooplankton groups (copepods, euphausiids, chaetognaths, and hydrozoans). We evaluated classifier predictions against observations of a mixed zooplankton community in a submerged purpose-built mesocosm (12 m3) insonified with broadband transmissions (185–255 kHz). The mesocosm was deployed from a wharf in Ny-Ålesund, Svalbard, during the Arctic polar night in January 2022. We detected 7722 tracked single targets, which were used to evaluate the classifier predictions of measured zooplankton targets. The classifiers could differentiate copepods from the other groups reasonably well, but they could not differentiate euphausiids, chaetognaths, and hydrozoans reliably due to the similarities in their modelled target spectra. We recommend that model-informed classification of zooplankton from broadband acoustic signals be used with caution until a better understanding of in situ target spectra variability is gained.Publisher PDFPeer reviewe

Postglacial expansion of the arctic keystone copepod calanus glacialis

Calanus glacialis, a major contributor to zooplankton biomass in the Arctic shelf seas, is a key link between primary production and higher trophic levels that may be sensitive to climate warming. The aim of this study was to explore genetic variation in contemporary populations of this species to infer possible changes during the Quaternary period, and to assess its population structure in both space and time. Calanus glacialis was sampled in the fjords of Spitsbergen (Hornsund and Kongsfjorden) in 2003, 2004, 2006, 2009 and 2012. The sequence of a mitochondrial marker, belonging to the ND5 gene, selected for the study was 1249 base pairs long and distinguished 75 unique haplotypes among 140 individuals that formed three main clades. There was no detectable pattern in the distribution of haplotypes by geographic distance or over time. Interestingly, a Bayesian skyline plot suggested that a 1000-fold increase in population size occurred approximately 10,000 years before present, suggesting a species expansion after the Last Glacial Maximum.GAME from the National Science Centre, the Polish Ministry of Science and Higher Education Iuventus Plus [IP2014 050573]; FCT-PT [CCMAR/Multi/04326/2013]; [2011/03/B/NZ8/02876

Enhanced Secretion of Amylase from Exocrine Pancreas of Connexin32-deficient Mice

To determine whether junctional communication between pancreatic acinar cells contributes to their secretory function in vivo, we have compared wild-type mice, which express the gap junctional proteins connexin32 (Cx32) and connexin26, to mice deficient for the Cx32 gene. Pancreatic acinar cells from Cx32 (−/−) mice failed to express Cx32 as evidenced by reverse transcription–PCR and immunolabeling and showed a marked reduction (4.8- and 25-fold, respectively) in the number and size of gap junctions. Dye transfer studies showed that the extent of intercellular communication was inhibited in Cx32 (−/−) acini. However, electrical coupling was detected by dual patch clamp recording in Cx32 (−/−) acinar cell pairs. Although wild-type and Cx32 (−/−) acini were similarly stimulated to release amylase by carbamylcholine, Cx32 (−/−) acini showed a twofold increase of their basal secretion. This effect was caused by an increase in the proportion of secreting acini, as detected with a reverse hemolytic plaque assay. Blood measurements further revealed that Cx32 (−/−) mice had elevated basal levels of circulating amylase. The results, which demonstrate an inverse relationship between the extent of acinar cell coupling and basal amylase secretion in vivo, support the view that the physiological recruitment of secretory acinar cells is regulated by gap junction mediated intercellular communication

Measurement of the Spectroscopy of Orbitally Excited B Mesons at LEP

We measure the masses, decay widths and relative production rate of orbitally excited B mesons using 1.25 million hadronic Z decays recorded by the L3 detector. B-meson candidates are inclusively reconstructed and combined with charged pions produced at the primary event vertex. An excess of events above the expected background in the B\pi mass spectrum in the region 5.6-5.8 GeV is interpreted as resulting from the decay B_u,d^** -> B^(*)\pi, where B_u,d^** denotes a mixture of l=1 B-meson states containing a u or a d quark. A fit to the mass spectrum yields the masses and decay widths of the B_1^* and B_2^* spin states, as well as the branching fraction for the combination of l=1 states. In addition, evidence is presented for the existence of an excited B-meson state or mixture of states in the region 5.9-6.0 GeV