Calanus Finmarchicus Research Articles

Acute Toxicity of Eight Oil Spill Response Chemicals to Temperate, Boreal, and Arctic Species

The objectives of this study were to (1) determine the acute toxicity of selected shoreline washing agents (SWA) and dispersants, and (2) assess interspecies differences in sensitivity to the products. Eight shoreline washing agents (Hela saneringsvæske, Bios, Bioversal, Absorrep K212, and Corexit 9580) and chemical dispersants (Corexit 9500, Dasic NS, and Gamlen OD4000) were tested on five marine species, algae Skeletonema costatum, planktonic copepod species Acartia tonsa (temperate species), Calanus finmarchicus (boreal species) and Calanus glacialis (Arctic species), and benthic amphipod Corophium volutator. For most products, A. tonsa was the most sensitive species, whereas C. volutator was the least sensitive; however, these species were exposed through different media (water/sediment). In general, all copepod species displayed a relatively similar sensitivity to all products. However, A. tonsa was somewhat more sensitive than other copepods to most of the tested products. Thus, A. tonsa appears to be a candidate species for boreal and Arctic copepods for acute toxicity testing, and data generated on this species may be used as to provide conservative estimates. The benthic species (C. volutator) had a different sensitivity pattern relative to pelagic species, displaying higher sensitivity to solvent-based SWA than to water-based SWA. Comparing product toxicity, the dispersants were in general most toxic while the solvent-based SWA were least toxic to pelagic species.

Diffusible gas transmitter signaling in the copepod crustacean Calanus finmarchicus: Identification of the biosynthetic enzymes of nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S) using a de novo assembled transcriptome

Neurochemical signaling is a major component of physiological/behavioral control throughout the animal kingdom. Gas transmitters are perhaps the most ancient class of molecules used by nervous systems for chemical communication. Three gases are generally recognized as being produced by neurons: nitric oxide (NO), carbon monoxide (CO) and hydrogen sulfide (H2S). As part of an ongoing effort to identify and characterize the neurochemical signaling systems of the copepod Calanus finmarchicus, the biomass dominant zooplankton in much of the North Atlantic Ocean, we have mined a de novo assembled transcriptome for sequences encoding the neuronal biosynthetic enzymes of these gases, i.e. nitric oxide synthase (NOS), heme oxygenase (HO) and cystathionine β-synthase (CBS), respectively. Using Drosophila proteins as queries, two NOS-, one HO-, and one CBS-encoding transcripts were identified. Reverse BLAST and structural analyses of the deduced proteins suggest that each is a true member of its respective enzyme family. RNA-Seq data collected from embryos, early nauplii, late nauplii, early copepodites, late copepodites and adults revealed the expression of each transcript to be stage specific: one NOS restricted primarily to the embryo and the other was absent in the embryo but expressed in all other stages, no CBS expression in the embryo, but present in all other stages, and HO expressed across all developmental stages. Given the importance of gas transmitters in the regulatory control of a number of physiological processes, these data open opportunities for investigating the roles these proteins play under different life-stage and environmental conditions in this ecologically important species.

Prediction of the peptidomes of Tigriopus californicus and Lepeophtheirus salmonis (Copepoda, Crustacea)

Transcriptome mining is a powerful method for crustacean peptide discovery, especially when large sequence datasets are available and an appropriate reference is extant. Recently, a 206,041-sequence transcriptome for the copepod Calanus finmarchicus was mined for peptide-encoding transcripts, with ones for 17 families/subfamilies identified. Here, the deduced Calanus pre/preprohormones were used as templates for peptide discovery in the copepods Tigriopus californicus and Lepeophtheirus salmonis; large transcriptome shotgun assembly datasets are publicly accessible for both species. Sixty-five Tigriopus and 17 Lepeophtheirus transcripts, encompassing 22 and 13 distinct peptide families/subfamilies, respectively, were identified, with the structures of 161 and 70 unique mature peptides predicted from the deduced precursors. The identified peptides included members of the allatostatin A, allatostatin C, bursicon α, bursicon β, CAPA/periviscerokinin/pyrokinin, crustacean cardioactive peptide, crustacean hyperglycemic hormone/ion transport peptide, diuretic hormone 31, FLRFamide, leucokinin, myosuppressin, neuroparsin, neuropeptide F, orcokinin, and tachykinin-related peptide families, most of which possess novel structures, though isoforms from other copepods are known. Of particular note was the discovery of novel isoforms of adipokinetic hormone-corazonin-like peptide, allatotropin, corazonin, eclosion hormone and intocin, peptide families previously unidentified in copepods. In addition, Tigriopus precursors for two previously unknown peptide groups were discovered, one encoding GSEFLamides and the other DXXRLamides; precursors for the novel FXGGXamide family were identified from both Tigriopus and Lepeophtheirus. These data not only greatly expand the catalog of known copepod peptides, but also provide strong foundations for future functional studies of peptidergic signaling in members of this ecologically important crustacean subclass.

Spatio-Temporal Variability of the North Sea Cod Recruitment in Relation to Temperature and Zooplankton

The North Sea cod (Gadus morhua, L.) stock has continuously declined over the past four decades linked with overfishing and climate change. Changes in stock structure due to overfishing have made the stock largely dependent on its recruitment success, which greatly relies on environmental conditions. Here we focus on the spatio-temporal variability of cod recruitment in an effort to detect changes during the critical early life stages. Using International Bottom Trawl Survey (IBTS) data from 1974 to 2011, a major spatio-temporal change in the distribution of cod recruits was identified in the late 1990s, characterized by a pronounced decrease in the central and southeastern North Sea stock. Other minor spatial changes were also recorded in the mid-1980s and early 1990s. We tested whether the observed changes in recruits distribution could be related with direct (i.e. temperature) and/or indirect (i.e. changes in the quantity and quality of zooplankton prey) effects of climate variability. The analyses were based on spatially-resolved time series, i.e. sea surface temperature (SST) from the Hadley Center and zooplankton records from the Continuous Plankton Recorder Survey. We showed that spring SST increase was the main driver for the most recent decrease in cod recruitment. The late 1990s were also characterized by relatively low total zooplankton biomass, particularly of energy-rich zooplankton such as the copepod Calanus finmarchicus, which have further contributed to the decline of North Sea cod recruitment. Long-term spatially-resolved observations were used to produce regional distribution models that could further be used to predict the abundance of North Sea cod recruits based on temperature and zooplankton food availability.

Water mass structure defines the diapausing copepod distribution in a right whale habitat on the Scotian Shelf

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 497:69-85 (2014) - DOI: https://doi.org/10.3354/meps10584 Water mass structure defines the diapausing copepod distribution in a right whale habitat on the Scotian Shelf Kimberley T. A. Davies1,*, Christopher T. Taggart1, R. Kent Smedbol1,2 1Department of Oceanography, Dalhousie University, 1355 Oxford St., Halifax, Nova Scotia, B3H 4R2, Canada 2Fisheries and Oceans Canada, Bedford Institute of Oceanography, 1 Challenger Drive, Dartmouth, Nova Scotia, B2Y 4A2, Canada *Corresponding author: kim.davies@dal.ca ABSTRACT: North Atlantic right whales Eubalaena glacialis aggregate in Roseway Basin on the western Scotian Shelf where their energy-rich food sources, diapausing copepods Calanus spp., are concentrated at depth. The Canadian Species at Risk Recovery Strategy for right whales provides provisional Critical Habitat (CH) boundaries for Roseway Basin based on right whale occupancy, with the stipulation that the boundaries be refined using spatially explicit indicators of CH, specifically the environmental, oceanographic, and bathymetric conditions responsible for the copepod aggregations and distribution. We measured the concentration, energy density, spatial distribution, and extent of the right whale food base and the related oceanography at depth in the Basin during late-summer 2008 with the goal of refining the spatial extent of right whale CH. We show that the diapausing copepods were distributed throughout the Basin, with elevated concentrations located at depth toward the northeast and along the southern Basin margin slope. The aggregations were associated with warm, salty, high-density (26.0 to 26.2 σt, kg m-3), continental slope-influenced water masses and not with cold, fresh, low-density (<26.0 σt) water masses originating on the Scotian Shelf. Tidally driven variation in the copepod aggregations across the southern slope was coincident with the movement of the 26.0 σt isopycnal. We propose a mechanism, based on water mass density and advection, that explains the spatial and temporal (e.g. inter-annual) variation in diapausing Calanus energy density (joules per unit ocean volume) distribution, and by proxy, variation in right whale occupancy of the Basin. We further propose that the provisional CH boundaries, partly conditioned on vessel-strike mitigation measures, be extended to better encompass the critical feeding habitat. This could be achieved without compromise regarding vessel traffic and existing vessel-strike mitigation. KEY WORDS: North Atlantic right whale · Critical Habitat · Roseway Basin · Water mass density · Slope water · Calanus finmarchicus · Calanus hyperboreus · Conservation Full text in pdf format Supplementary material PreviousNextCite this article as: Davies KTA, Taggart CT, Smedbol RK (2014) Water mass structure defines the diapausing copepod distribution in a right whale habitat on the Scotian Shelf. Mar Ecol Prog Ser 497:69-85. https://doi.org/10.3354/meps10584 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 497. Online publication date: February 05, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.

Wax Esters from the Marine Copepod Calanus finmarchicus Reduce Diet-Induced Obesity and Obesity-Related Metabolic Disorders in Mice1–3

We showed previously that dietary supplementation with oil from the marine zooplankton Calanus finmarchicus (Calanus oil) attenuates obesity, inflammation, and glucose intolerance in mice. More than 80% of Calanus oil consists of wax esters, i.e., long-chain fatty alcohols linked to long-chain fatty acids. In the present study, we compared the metabolic effects of Calanus oil-derived wax esters (WE) with those of purified eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) ethyl esters (E/D) in a mouse model of diet-induced obesity. C57BL/6J mice received a high-fat diet (HFD; 45% energy from fat). After 7 wk, the diet was supplemented with either 1% (wt:wt) WE or 0.2% (wt:wt) E/D. The amount of EPA + DHA in the E/D diet was matched to the total amount of n–3 (ω-3) polyunsaturated fatty acids (PUFAs) in the WE diet. A third group was given an unsupplemented HFD throughout the entire 27-wk feeding period. WE reduced body weight gain, abdominal fat, and liver triacylglycerol by 21%, 34%, and 52%, respectively, and significantly improved glucose tolerance and aerobic capacity. In abdominal fat depots, WE reduced macrophage infiltration by 74% and downregulated expression of proinflammatory genes (tumor necrosis factor-α, interleukin–6, and monocyte chemoattractant protein–1), whereas adiponectin expression was significantly upregulated. By comparison, E/D primarily suppressed the expression of proinflammatory genes but had less influence on glucose tolerance than WE. E/D affected obesity parameters, aerobic capacity, or adiponectin expression by <10%. These results show that the wax ester component of Calanus oil can account for the biologic effects shown previously for the crude oil. However, these effects cannot exclusively be ascribed to the content of n–3 PUFAs in the wax ester fraction.

Revisiting the Role of Individual Variability in Population Persistence and Stability

Populations often exhibit a pronounced degree of individual variability and this can be important when constructing ecological models. In this paper, we revisit the role of inter-individual variability in population persistence and stability under predation pressure. As a case study, we consider interactions between a structured population of zooplankton grazers and their predators. Unlike previous structured population models, which only consider variability of individuals according to the age or body size, we focus on physiological and behavioural structuring. We first experimentally demonstrate a high degree of variation of individual consumption rates in three dominant species of herbivorous copepods (Calanus finmarchicus, Calanus glacialis, Calanus euxinus) and show that this disparity implies a pronounced variation in the consumption capacities of individuals. Then we construct a parsimonious predator-prey model which takes into account the intra-population variability of prey individuals according to behavioural traits: effectively, each organism has a ‘personality’ of its own. Our modelling results show that structuring of prey according to their growth rate and vulnerability to predation can dampen predator-prey cycles and enhance persistence of a species, even if the resource stock for prey is unlimited. The main mechanism of efficient top-down regulation is shown to work by letting the prey population become dominated by less vulnerable individuals when predator densities are high, while the trait distribution recovers when the predator densities are low.

Prediction of the protein components of a putative Calanus finmarchicus (Crustacea, Copepoda) circadian signaling system using a de novo assembled transcriptome

Diel vertical migration and seasonal diapause are critical life history events for the copepod Calanus finmarchicus. While much is known about these behaviors phenomenologically, little is known about their molecular underpinnings. Recent studies in insects suggest that some circadian genes/proteins also contribute to the establishment of seasonal diapause. Thus, it is possible that in Calanus these distinct timing regimes share some genetic components. To begin to address this possibility, we used the well-established Drosophila melanogaster circadian system as a reference for mining clock transcripts from a 200,000+ sequence Calanus transcriptome; the proteins encoded by the identified transcripts were also deduced and characterized. Sequences encoding homologs of the Drosophila core clock proteins CLOCK, CYCLE, PERIOD and TIMELESS were identified, as was one encoding CRYPTOCHROME 2, a core clock protein in ancestral insect systems, but absent in Drosophila. Calanus transcripts encoding proteins known to modulate the Drosophila core clock were also identified and characterized, e.g. CLOCKWORK ORANGE, DOUBLETIME, SHAGGY and VRILLE. Alignment and structural analyses of the deduced Calanus proteins with their Drosophila counterparts revealed extensive sequence conservation, particularly in functional domains. Interestingly, reverse BLAST analyses of these sequences against all arthropod proteins typically revealed non-Drosophila isoforms to be most similar to the Calanus queries. This, in combination with the presence of both CRYPTOCHROME 1 (a clock input pathway protein) and CRYPTOCHROME 2 in Calanus, suggests that the organization of the copepod circadian system is an ancestral one, more similar to that of insects like Danaus plexippus than to that of Drosophila.

Annual variation in the nutritional value of Stage V Calanus finmarchicus: implications for right whales and other copepod predators

Stage V (C5) Calanus finmarchicus is a central prey item for animals feeding at sev- eral trophic levels in the Bay of Fundy, Canada, especially the highly endangered North Atlantic right whale Eubalaena glacialis. Here, we show that the energy and lipid content of C5 C. fin- marchicus collected twice monthly (July to September) from the Grand Manan Basin exhibited significant variation over multiple years (2006 to 2010). Mean ± SD wet mass energy (6.77 ± 0.65 kJ g �1 ) was highest in 2007 and lowest in 2009 (5.82 ± 0.90 kJ g �1 ); lipid content followed the same pattern. Significant decreases in individual energy content were observed over the summer during 2006 and 2010. Lipid content was significantly correlated with energy content. Overall, energy content of copepods was 13% lower in 2009 than in 2006�2007, which could alter foraging patterns and activity budgets of predators such as the North Atlantic right whale and have impli- cations for assessment of whale habitat based on models of energy requirements. Variation in C5 quality may be linked to annual changes in the lipid content of Bay of Fundy herring, which con- sume copepods and are in turn a main prey item of seabirds, fishes, and marine mammals. Our study emphasizes that variation in quality, not just quantity, of prey should be considered when formulating predator consumption models and in tracking trophic transfer.

Peptidergic signaling in Calanus finmarchicus (Crustacea, Copepoda): In silico identification of putative peptide hormones and their receptors using a de novo assembled transcriptome

The copepod Calanus finmarchicus is the most abundant zooplankton species in the North Atlantic. While the life history of this crustacean is well studied, little is known about its peptidergic signaling systems despite the fact that these pathways are undoubtedly important components of its physiological/behavioral control systems. Here we have generated and used a de novo assembled transcriptome for C. finmarchicus (206,041 sequences in total) to identify peptide precursor proteins and receptors. Using known protein queries, 34 transcripts encoding peptide preprohormones and 18 encoding peptide receptors were identified. Using a combination of online software programs and homology to known arthropod isoforms, 148 mature peptides were predicted from the deduced precursors, including members of the allatostatin-A, allatostatin-B, allatostatin-C, bursicon, crustacean cardioactive peptide (CCAP), crustacean hyperglycemic hormone, diuretic hormone 31 (DH31), diuretic hormone 44 (DH44), FMRFamide-like peptide (myosuppressin, neuropeptide F [NPF] and extended FL/IRFamide subfamilies), leucokinin, neuroparsin, orcokinin, orcomyotropin, periviscerokinin, RYamide and tachykinin-related peptide (TRP) families. The identified receptors included ones for allatostatin-A, allatostatin-C, bursicon, CCAP, DH31, DH44, ecdysis-triggering hormone, NPF, short NPF, FMRFamide, insulin-like peptide, leucokinin, periviscerokinin, pigment dispersing hormone, and TRP. Developmental profiling of the identified transcripts in embryos, early nauplii, late nauplii, early copepodites, late copepodites, and adult females was also undertaken, with all showing the highest expression levels in the naupliar and copepodite stages. Collectively, these data radically expand the catalog of known C. finmarchicus peptidergic signaling proteins and provide a foundation for experiments directed at understanding the physiological roles served by them in this species.

Acute exposure of water soluble fractions of marine diesel on Arctic Calanus glacialis and boreal Calanus finmarchicus: Effects on survival and biomarker response

The use of marine diesels in Arctic areas is expected to increase due to increased shipping transport, oil and gas activities, and the ban of heavy bunker oils in many areas. This project aimed at gathering information regarding the sensitivity of an Arctic copepod to marine diesel. The approach undertaken was to study the effects on survival (LC50s) and gene expression of a known detoxification gene (glutathione S-transferase [GST]) in Calanus glacialis following exposure to water soluble fractions (WSFs) of marine diesel (at 2°C). We compared the observed LC-values of C. glacialis to the identical experimental data of the boreal Calanus finmarchicus (at 10°C), and to the predicted LC50-values using regression models. The C. glacialis appeared more tolerant to the acute effects of marine diesel WSF compared to the “average pelagic crustacean” as predicted by regression models, and compared to C. finmarchicus. Although these results may be explained by a slower equilibration of petrogenic chemicals from the WSF at lower temperatures, C. glacialis also displayed higher GST expression following exposure than C. finmarchicus. In addition, the lipid content of the test organisms appears to be an important factor for the determination of acute toxicity, as copepods with high lipid content survived longer than copepods with low lipid content.

Applying the concept of the ecological niche and a macroecological approach to understand how climate influences zooplankton: Advantages, assumptions, limitations and requirements

Ecosystem effects of climate change have been detected in all components of the Earth System. In the marine biosphere, climate-change responses have caused large and well-documented biogeographical and phenological shifts, which have in turn altered local dominance hierarchies, and also the structure, diversity and functional linkages within regional marine ecosystems. There is an urgent need to improve both our knowledge of the global-scale effects of climate change on marine biodiversity and our capacity to project future impacts. But extrapolation of previously estimated changes to additional places and to future conditions is complicated by non-linear responses to environmental variables, and also by complexities of multivariate interaction that can lead to tipping-points. In this paper, we show how observations from widely-spaced locations can be combined to characterise the ecological niche of a species, and how the concept of the niche can be used to understand and project how climate-induced changes in temperatures will alter marine zooplankton both locally and globally. As an example to illustrate our view, we apply this framework to the relatively well-known copepod Calanus finmarchicus. Our results suggest that climate change will strongly affect the local abundance of this species in the North Atlantic Ocean by the end of this century. Predicted changes are large (e.g. increase by ±6–10-fold of the temporal changes in the abundance of C. finmarchicus) and vary as a function of the magnitude of warming and the local sign and steepness of the thermal niche. Substantial rates of change hold even under optimistic climatic scenarii. After reviewing the main limitations of the niche concept in bioclimatological research, we argue that the application of this concept in ecology and bioclimatology might nevertheless represent the best tool currently available to scientists to discern and anticipate the effect of global climate change on species and ecosystems. The framework we proposed forces us however to think globally and to develop a worldwide coordinated macroecological approach, that includes global monitoring, new mathematical tools of detection and new types of modeling.

In silico characterization of the insect diapause-associated protein couch potato (CPO) in Calanus finmarchicus (Crustacea: Copepoda)

Couch potato (CPO) is an RNA-binding protein involved in the regulation of nervous system development and adult diapause in insects. Within insects, this protein is highly conserved, yet it has not been identified in another large arthropod group, the Crustacea. Here, functional genomics was used to identify putative CPO homologs in the copepod Calanus finmarchicus, a planktonic crustacean that undergoes seasonal diapause. In silico mining of expressed sequence tag (EST) and 454 pyrosequencing data resulted in the identification of two full-length CPO proteins, each 205 amino acids long. The two C. finmarchicus CPOs (Calfi-CPO I and II) are identical in sequence with the exception of three amino acids, and are predicted to possess a single RNA recognition motif (RRM). Sequence comparison of the two Calfi-CPOs with those of insects shows high levels of amino acid conservation, particularly in their RRMs. Using the C. finmarchicus sequences as queries, ESTs encoding partial CPOs were identified from two other crustaceans, the parasitic copepod Lernaeocera branchialis and shrimp Penaeus monodon. Surprisingly, no convincing CPO-encoding transcripts were identified from crustacean species with very large (>100,000) EST datasets (e.g. Litopenaeus vannamei, Daphnia pulex and Lepeophtheirus salmonis), suggesting that CPO transcript/protein may be expressed at very low levels or absent in some crustaceans. RNA-Seq data suggested stage-specific expression of CPO in C. finmarchicus, with few transcripts present in eggs (which represent mixed embryonic stages) and adults, and high levels in nauplii and copepodites; stages exhibiting high CPO expression are consistent with a role for it in neuronal development.

Calanus spp.—Vectors for the biotoxin, domoic acid, in the Arctic marine ecosystem?

Three Calanus species, Calanus glacialis, Calanus finmarchicus and Calanus hyperboreus, which are the most important zooplankton herbivores in Western Greenland, were fed with unialgal cultures of toxic Pseudo-nitzschia seriata and non-toxic Pseudo-nitzschia delicatissima. All three copepod species grazed on toxic P. seriata and also accumulated domoic acid during the grazing. There were no differences in ingestion rates between toxic and non-toxic Pseudo-nitzschia species in any of the copepods. C. finmarchicus and C. hyperboreus grazed on toxic P. seriata during the first 6h of the experiment but seemed to stop grazing during the last 6h of the experiment suggesting that the copepods may have suffered some kind of physiological incapacitation due to ingestion of domoic acid. C. glacialis grazed on toxic P. seriata continuously during the whole experiment, probably due to the lower domoic acid cell quota of P. seriata during the experiment on C. glacialis than on the other two copepod species. The depuration experiment on C. glacialis indicated that the copepods still retained domoic acid after 10h of depuration in filtered sea water. The results show that the three Calanus species are potential vectors for domoic acid to higher trophic levels in the Arctic.

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Degradation of copepod faecal pellets in the upper layer: role of microbial community and Calanus finmarchicus

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 462:39-49 (2012) - DOI: https://doi.org/10.3354/meps09808 Degradation of copepod faecal pellets in the upper layer: role of microbial community and Calanus finmarchicus Camilla Svensen*, Christian Wexels Riser, Marit Reigstad, Lena Seuthe Faculty of Biosciences, Fisheries and Economics, University of Tromsø, 9037 Tromsø, Norway *Email: camilla.svensen@uit.no ABSTRACT: Copepod faecal pellets (FP) are considered important contributors to vertical carbon flux, but investigations comparing FP production with FP export using sediment traps conclude that vertical export is not their only fate. FP are degraded to a large extent in the upper 60 m, and even among large, fast-sinking FP, only a fraction reaches sediment traps deeper than 200 m. Retention mechanisms for copepod FP are still not well understood. In order to investigate the relative importance of the small (<180 µm) compartment of the plankton community versus larger filter-feeding copepods for degradation of large, fast-sinking FP, we incubated FP produced by Calanus finmarchicus (Gunnerus) in 180 µm-filtered water from the chlorophyll a maximum. From a series of experiments, we found that the degradation of large FP is time-dependent, as no degradation was apparent after 20 or 48 h of incubation, but after 72 h FP volume was reduced by 32%. We also found that large filter-feeding copepods may facilitate the degradation process, since FP degradation increased from 0 to 75% after 48 h of incubation in the presence of 5 C. finmarchicus. We conclude that ciliates and dinoflagellates are able to degrade large copepod FP, but that this process is too slow to explain observed retention of large FP in the upper 200 m of the water column due to fast sinking of large particles. Rather than looking for single-factor explanations for flux-regulating processes, we stress the importance of investigating combined effects in relevant time frames to understand the complexity of carbon flux regulation in natural systems. KEY WORDS: Faecal pellet · Faecal pellet retention · Microbial degradation · Faecal pellet fragmentation · Calanus finmarchicus · Carbon cycling Full text in pdf format PreviousNextCite this article as: Svensen C, Wexels Riser C, Reigstad M, Seuthe L (2012) Degradation of copepod faecal pellets in the upper layer: role of microbial community and Calanus finmarchicus. Mar Ecol Prog Ser 462:39-49. https://doi.org/10.3354/meps09808 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 462. Online publication date: August 21, 2012 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2012 Inter-Research.

Feeding ecology of capelin (Mallotus villosus Müller) in West Greenland waters

Capelin (Mallotus villosus Muller) is a key pelagic mediator of energy from lower to higher trophic levels in arctic waters. This is also the case in Greenland waters, but little is known of its feeding behaviour in this region. By analysing stable nitrogen isotopes and stomach content of capelin collected along 1500 km of the Greenland west coast, this study aims to provide knowledge on capelin feeding ecology and the role that diet composition and biomass may have in generating the observed latitudinal growth differences in Greenland capelin. In total, 572 stomachs were sampled. The most dominant prey by wet weight was euphausiids (61 %) followed by amphipods (18 %) and copepods (10 %). The most common species were Thysanoessa raschii, Themisto libulla, Calanus finmarchicus and Calanus hyperboreus. Copepods dominated in smaller capelin but were replaced by euphausiids in larger fish. A similar prey shift towards euphausiids along with an increase in prey weight (relative and absolute) was seen with increasing latitude. The spatial variation in feeding pattern was supported by stable nitrogen analyses. The mean δ15N values of capelin muscle tissue for the south (60–64°N) and north (68–72°N) were 9.54 ‰ ± 0.72 and 12.47 ‰ ± 0.38 (mean ± SD), respectively. However, when differences in isotopic baseline values (C. finmarchicus δ15N, 2.47 ‰) in the two areas were taken into account, the isotope values suggest that capelin in the northern areas fed on a slightly higher trophic level higher than in the south, as would be expected with increasing importance of euphausiids. These significant feeding differences along the Greenland west coast are likely impacting capelin growth and condition as they show parallel trends along the same gradient.

Using RAFOS floats to simulate overwinter transport of Calanus finmarchicus in the Norwegian Sea

The Norwegian Sea is one of the core areas of the copepod Calanus finmarchicus. We use 33 drift trajectories of RAFOS floats over 6 months to describe and discuss overwinter transportation of C. finmarchicus in the Norwegian Sea. The mean drift speed of the floats was 5.7 cms−1, which resulted in a mean trajectory length of 881 km. The corresponding displacement speed and displacement was 2.1 cms−1 and 326 km. Our results show that most of the floats remain within the Norwegian basin. The data set clearly indicates that the winter exchange between the southeast and northwest in the Norwegian Basin is very limited and mainly restricted to a narrow band along the ridge delimiting the Norwegian Basin in the north. The fate of an overwintering C. finmarchicus is strongly dependent on where it sinks into the deep water to overwinter. If it takes place over the slope (bottom depth < 1700 m) in the south, the chance is high that it will be expelled into the North Atlantic. From a position close by, but just in slightly deeper water, may result in a fast track far into the Lofoten Basin.

Modelling secondary production in the Norwegian Sea with a fully coupled physical/primary production/individual-based Calanus finmarchicus model system

The copepod Calanus finmarchicus is the dominant species of the meso-zooplankton in the Norwegian Sea, and constitutes an important link between the phytoplankton and the higher trophic levels in the Norwegian Sea food chain. An individual-based model for C. finmarchicus, based on super-individuals and evolving traits for behaviour, stages, etc., is two-way coupled to the NORWegian ECOlogical Model system (NORWECOM). One year of modelled C. finmarchicus spatial distribution, production and biomass are found to represent observations reasonably well. High C. finmarchicus abundance is found along the Norwegian shelf-break in the early summer, while the overwintering population is found along the slope and in the deeper Norwegian Sea basins. The timing of the spring bloom is generally later than in the observations. Annual Norwegian Sea production is found to be 29 million tonnes of carbon and a production to biomass (P/B) ratio of 4.3 emerges. Sensitivity tests show that the modelling system is robust to initial values of behavioural traits and with regards to the number of super-individuals simulated given that this is above about 50,000 individuals. Experiments with the model system indicate that it provides a valuable tool for studies of ecosystem responses to causative forces such as prey density or overwintering population size. For example, introducing C. finmarchicus food limitations reduces the stock dramatically, but on the other hand, a reduced stock may rebuild in one year under normal conditions.

Late-summer zooplankton community structure, abundance, and distribution in the Hudson Bay system (Canada) and their relationships with environmental conditions, 2003–2006

Zooplankton communities were examined for the first time in three different hydrographic regions of the Hudson Bay system (HBS) in early August to early September from 2003 to 2006. Sampling was conducted at 50 stations distributed along different transects located in Hudson Bay (HB), Hudson Strait (HS), and Foxe Basin (FB). Variations in zooplankton biomass, abundance, taxonomic composition, and diversity in relation to environmental variables were studied using multivariate techniques. During all sampling years, the total zooplankton biomass was on average four times lower in HB than in HS and FB. Clustering samples by their relative species compositions revealed no interannual variation in zooplankton community but showed a marked interregional variability between the three regions. Water column stratification explained the greatest proportion (25%) of this spatial variability. According to redundancy analysis (RDA), the zooplankton taxa that contribute most to the separation of the three regions are Microcalanus spp., Oithona similis, Oncaea borealis, Aeginopsis laurentii, Sagitta elegans, Fritillaria sp., and larvae of cnidaria, chaetognatha, and pteropoda in HB; hyperiid amphipods in FB; and Pseudocalanus spp. CI–CV, Calanus glacialis CI–CVI, Calanus finmarchicus CI–CVI, Calanus hyperboreus CV–CVI, Acartia longiremis CI–CV, Metridia longa N3-N6 CI-CIII CVIf, Eukrohnia hamata, larvae of echinodermata, mollusca, cirripedia, appendicularia, and polychaeta in the northwestern and southeastern HS transects. For the HB transect, the RDA analyzed allowed us to distinguish three regions (HB west, central, and east) with different environmental gradients and zooplankton assemblages, in particular higher concentration of Pseudocalanus spp. nauplii and CI–CVI, as well as benthic macrozooplankton and meroplankton larvae in western HB. In HS, Calanoid species (mainly C. finmarchicus and C. glacialis) were mostly observed at the north shore stations associated with the weakly stratified Arctic–North Atlantic waters coming from southwestern Davis Strait (inflow). In general, the RDA models tested among the HBS regions were very consistent with its general surface circulation pattern for summer conditions in terms of environmental variables and distinct zooplankton assemblages. Overall, zooplankton biomass and diversity indices (H′, J′, and S) were lower in the most stratified environment (i.e., HB) than in the deeper (FB) and more dynamic (HS) regions. The results of this work clearly show that the spatial differentiation and structure of the zooplankton communities are strongly influenced by the hydrodynamic conditions in the HBS that, trough their actions on temperature, salinity, stratification, mixing conditions and depth strata, lead to the spatial differentiation of these communities.