Using the Continuous Plankton Recorder to investigate the absence of North Atlantic right whales (Eubalaena glacialis) from the Roseway Basin foraging ground

North Atlantic right whales (Eubalaena glacialis) were absent from Roseway Basin, located off southeastern Nova Scotia, for a 7-year period (1993–1999). The objective of this study was to examine the availability of the right whale's main prey, Calanus finmarchicus, in Roseway Basin during those 7 years to determine if the whales’ absence was due to inadequate prey resources. Since we had no historical data on zooplankton abundances at depth on the Scotian Shelf, near-surface zooplankton abundance data from the Continuous Plankton Recorder were used to infer water-column abundances. In addition, environmental parameters that are often correlated with high zooplankton concentrations were examined. The hypotheses tested were that changes in these parameters would be detectable between three time periods: pre-1993, 1993–1999 and post-1999. Calanus finmarchicus abundance was found to be lowest during 1993–1999, suggesting that right whales were not foraging in Roseway Basin because of the near-absence of their main prey species. Decreased in situ salinity and density proved to be indicators of the changes in circulation in the 1990s that may have affected the advection of C. finmarchicus onto the Scotian Shelf.

Absolute and relative abundances of zooplankton taxa in Kongsfjorden during 2002

Seasonal changes in the zooplankton composition of the glacially influenced Kongsfjorden, Svalbard (79°N, 12°E), and its adjacent shelf were studied in 2002. Samples were collected in the spring, summer and autumn in stratified hauls (according to hydrographic characteristics), by means of a 0.180-mm Multi Plankton Sampler. A strong front between the open sea and the fjord waters was observed during the spring, preventing water mass exchange, but was not observed later in the season. The considerable seasonal changes in zooplankton abundance were related to the seasonal variation in hydrographical regime. The total zooplankton abundance during the spring (40-2010 individuals/m**3) was much lower than in the summer and autumn (410-10,560 individuals/m**3). The main factors shaping the zooplankton community in the fjord include: the presence of a local front, advection, the flow pattern and the decreasing depth of the basin in the inner fjord. Presumably these factors regulate the gross pattern of zooplankton density and distribution, and override the importance of biological processes. This study increased our understanding of seasonal processes in fjords, particularly with regard to the strong seasonal variability in the Arctic.

Abundance and biomass of zooplankton collected in 1995 and 1998 in the frontal zone between the Gulf Stream and the Labrador current

Vertical distribution of meso- and macroplankton was studied in the region of the most sharply pronounced climatic frontal zone between the Gulf Stream and the Labrador current. Hauls with a plankton net BR 113/140 and visual counts of macroplankton from the Mir submersible were used. In the frontal zone a contact occurs between arctic-boreal communities and communities of the North Atlantic subtropical gyre. The community of the North Atlantic subtropical gyre is more mature in terms of succession; many macroplanktonic carnivores-scavengers (mainly shrimps Acanthephyra) develop there and form a ''living network'' feeding on those transported from the north rich arctic-boreal mesoplankton. As a result biomass of shrimps appears to be significantly higher than biomass of their preys. Peculiarities of vertical distribution and population structure of shrimps were analyzed. Data on quantitative vertical distribution of total biomass of meso- and macroplankton and its principal groups, including gelatinous animals (ctenophores, medusas, and siphonophores) were obtained. Variations of the role of different plankton groups with depth were considered; these data enable a conclusion that frontal variations of the community structure embrace the depth range from the surface down to 2000 m.

Time series of zooplankton abundance at station L4 in the English Channel from 1988 to 2011

Ongoing zooplankton research at the Plymouth Marine Laboratory has established a time series of zooplankton species since 1988 at L4, a coastal station off Plymouth. Samples were collected by vertical net hauls (WP2 net, mesh 200 µm; UNESCO 1968) from the sea floor (approximately 50 m) to the surface and stored in 4% formalin. Much of the zooplankton analysis has been to the level of "major taxonomic groups" only, and a number of different analysts have participated over the years. The level of expertise has generally been consistent, but the user should be aware that levels of taxonomic discrimination may vary during the course of the dataset. The dominant calanoid copepods are generally well discriminated to species throughout. Calanus has not been routinely examined for species determination, the assumption being that the local population is entirely composed of Calanus helgolandicus. In certain years there has been a particular interest in Temora stylifera, Centropages cherchiae and other species reflected in the dataset. The lack of records in other previous years does not necessarily reflect species absence. We view it as essential for all users of L4 plankton data to establish and maintain contact with the nominated current data originators as well as fully consulting the metadata. While not impinging on free data access, this ensures that this large, species-rich but slightly complex species database is being used in the correct way, and any potential issues with the data are clarified. Furthermore, a proper dialogue with these local experts on the time series will enable where appropriate the most recent sampling timepoints to be used. The data can be downloaded from BODC or from doi:10.1594/PANGAEA.778092 as files for each year by searching for "L4 zooplankton". The most comprehensive dataset is the version downloadable directly from this page. The entire set of zooplankton samples is stored at the Plymouth Marine Laboratory in buffered formalin, and may be available for further taxonomic analysis on request.

Fecal pellet and egg production rates of copepod species at varying suspended sediment concentrations

We investigated the effect of suspended sediments on the vital rates of the copepods Calanus finmarchicus, Pseudocalanus sp. and Metridia longa in a Greenland sub-Arctic fjord. The fjord had a gradient of suspended particulate matter (SPM) with high concentrations (>50 mg/L) in the inner fjord due to glacial melt water runoff. Laboratory experiments showed that when feeding on the diatom Thalassiosira weissflogii specific ingestion rates were low at high concentrations of suspended sediment for C. finmarchicus (>20 mg/L) and Pseudocalanus sp. (>50 mg/L), while no effect was found for M. longa. For C. finmarchicus, a relatively constant fecal pellet production (FPP) and fecal pellet volume suggested ingestion of sediment, which probably led to reduction in egg production rates (EPRs) at high sediment concentrations. For Pseudocalanus sp., FPP decreased with increasing sediment concentrations, while no effect was observed on EPR. No significant difference was observed in FPP for M. longa feeding on the diatom T. weissflogii compared to the ciliate Strombidium sulcatum. The study shows that high sediment concentrations influence the capability of carbon turnover in C. finmarchicus and Pseudocalanus sp., while M. longa appears to be more tolerant to high sediment loads. Therefore, high concentrations of SPM could potentially influence the species composition of glacially influenced fjords.

Properties of water masses, taxa abundance, and isotopic ratios of samples obtained around Svalbard archipelago

The feeding strategies of Calanus hyperboreus, C. glacialis, and C. finmarchicus were investigated in the high-Arctic Svalbard region (77-81 °N) in May, August, and December, including seasons with algal blooms, late- to post-bloom situations, and unproductive winter periods. Stable isotope and fatty acid trophic marker (FATM) techniques were employed together to assess trophic level (TL), carbon sources (phytoplankton vs. ice algae), and diet of the three Calanus species. In addition, population development, distribution, and nutritional state (i.e. storage lipids) were examined to estimate their population status at the time of sampling. In May and August, the vertical distribution of the three Calanus species usually coincided with the maximum algal biomass. Their stable isotope and fatty acid (FA) composition indicated that they all were essentially herbivores in May, when the algal biomass was highest. Their FA composition, however, revealed different food preferences. C. hyperboreus had high proportions of 18:4n3, suggesting that it fed mainly on Phaeocystis, whereas C. glacialis and C. finmarchicus had high proportions of 16:4n1, 16:1n7, and 20:5n3, suggesting diatoms as their major food source. Carbon sources (i.e. phytoplankton vs. ice algae) were not possible to determine solely from FATM techniques since ice-diatoms and pelagic-diatoms were characterised by the same FA. However, the enriched d13C values of C. glacialis and C. finmarchicus in May indicated that they fed both on pelagic- and ice-diatoms. Patterns in absolute FA and fatty alcohol composition revealed that diatoms were the most important food for C. hyperboreus and C. glacialis, followed by Phaeocystis, whereas diatoms, Phaeocystis and other small autotrophic flagellates were equally important food for C. finmarchicus. During periods of lower algal biomass, only C. glacialis exhibited evidence of significant dietary switch, with a TL indicative of omnivory (mean TL=2.4). Large spatial variability was observed in population development, distribution, and lipid store sizes in August. At the northernmost station at the southern margin of the Arctic Ocean, the three Calanus species had similarly low lipid stores as they had in May, suggesting that they ascended later in the year. In December, relatively lipid-rich specimens had TL similar to those during the peak productive season (TL~2.0), suggesting that they were hibernating and not feeding on the available refractory material available at that time of the year. In contrast, lipid-poor specimens in December had substantially high TL (TL=2.5), suggesting that they were active and possibly were feeding.

The Global Plankton Database: an inventory and data from the Former Soviet Union expeditions

At present time, there is a lack of knowledge on the interannual climate-related variability of zooplankton communities of the tropical Atlantic, central Mediterranean Sea, Caspian Sea, and Aral Sea, due to the absence of appropriate databases. In the mid latitudes, the North Atlantic Oscillation (NAO) is the dominant mode of atmospheric fluctuations over eastern North America, the northern Atlantic Ocean and Europe. Therefore, one of the issues that need to be addressed through data synthesis is the evaluation of interannual patterns in species abundance and species diversity over these regions in regard to the NAO. The database has been used to investigate the ecological role of the NAO in interannual variations of mesozooplankton abundance and biomass along the zonal array of the NAO influence. Basic approach to the proposed research involved: (1) development of co-operation between experts and data holders in Ukraine, Russia, Kazakhstan, Azerbaijan, UK, and USA to rescue and compile the oceanographic data sets and release them on CD-ROM, (2) organization and compilation of a database based on FSU cruises to the above regions, (3) analysis of the basin-scale interannual variability of the zooplankton species abundance, biomass, and species diversity.

Water chemistry, and abundance and carbon biomass of under-ice fauna during POLARSTERN cruise ARK-XIX/1 to the Storfjord area in 2003

The under-ice habitat and fauna were studied during a typical winter situation at three stations in the western Barents Sea. Dense pack ice (7-10/10) prevailed and ice thickness ranged over <0.1-1.6 m covered by <0.1-0.6 m of snow. Air temperatures ranged between -1.8 and -27.5°C. The ice undersides were level, white and smooth. Temperature and salinity profiles in the under-ice water (0-5 m depth) were not stratified (T=-1.9 to -2.0°C and S=34.2-34.7). Concentrations of inorganic nutrients were high and concentrations of algal pigments were very low (0.02 µg chlorophyll a/l), indicating the state of biological winter. Contents of particulate organic carbon and nitrogen ranged over 84.2-241.3 and 5.3-16.4 µg/l, respectively, the C/N ratio over 11.2-15.5 pointing to the dominance of detritus in the under-ice water. Abundances of amphipods at the ice underside were lower than in other seasons: 0-1.8 ind/m**2 for Apherusa glacialis, 0-0.7 ind/m**2 for Onisimus spp., and 0-0.8 ind/m**2 for Gammarus wilkitzkii. A total of 22 metazoan taxa were found in the under-ice water, with copepods as the most diverse and numerous group. Total abundances ranged over 181-2,487 ind/m**3 (biomass: 70-2,439 µg C/m**3), showing lower values than in spring, summer and autumn. The dominant species was the calanoid copepod Pseudocalanus minutus (34-1,485 ind/m**3), contributing 19-65% to total abundances, followed by copepod nauplii (85-548 ind/m**3) and the cyclopoid copepod Oithona similis (44-262 ind/m**3). Sympagic (ice-associated) organisms occurred only rarely in the under-ice water layer.

Vertical distribution of mesoplankton at the northern margin of the North Atlantic gyre in June-August 2001

Vertical distribution of mesoplankton was studied over a single season in 2001 at two sites in the western and eastern parts of the northern margin of the North Atlantic gyre. Plankton was sampled both with use of BR 113/140 net and observed from the Mir deep-sea manned submersible. In near-slope waters southeast of Newfoundland (Titanic Polygon) there occurred intensive interaction between subtropical and sub-polar waters and plankton communities. The subtropical gyre community being more mature from the succession viewpoint created a ''net'' of carnivores and scavengers (shrimp and smaller animals) feeding plankton supplied from the north and thus increasing their own biomass. Due to features of hydrological conditions in 2001 in contrast to other years, the plankton supplied from the north was dominated by small copepods, while abundance of larger Calanus hyperboreus was small. Perhaps due to this fact, abundance of macroplanktonic shrimp decreased, while abundance of mesoplanktonic carnivores (Themisto, Sagitta, and Pareuchaeta) increased. In East Atlantic, within the Porcupine abyssal plain (Bismark Polygon) contrasts in frontal boundaries decreased and community interaction became less expressed. While vertical distribution of plankton at Titanic Polygon was characterized by a series of extraordinary features, distribution at Bismark Polygon was much more ordinary.

Zooplankton community within the Titanic Polygon, Northwest Atlantic, summer 2003

In summer 2003 we continued our long-term series of observations over the zooplankton community within the Titanic Polygon (area of the frontal zone of Gulf Stream and the Labrador Current) in the North Atlantic, where interaction of ecosystems of subpolar and warm waters takes place. Depending on hydrological situation occurring in the frontal zone interrelated interannual variations in abundance and biomass of plankton species including Calanus hyperboreus and mesopelagic shrimps of Acanthephyra genus were observed. In different years contribution of two parallel trophic nets passing primarily through the larger and smaller plankters to formation of the community varied. Data on the size structure of population of macroplankton shrimps are presented.

Biometry, and fatty acid and fatty alcohol composition of the Arctic ctenophore Mertensia ovum from Kongsfjorden

Lipids of the Arctic ctenophore Mertensia ovum, collected from Kongsfjorden (Svalbard) in 2001, were analysed to investigate seasonal variability and fate of dietary lipids. Total lipids, lipid classes and fatty acid and alcohol compositions were determined in animals, which were selected according to age-group and season. Changes in lipids of age-group 0 animals were followed during growth from spring to autumn. Total lipids increased from May to September. Lipids as percentage of dry mass were lowest in August indicating their use for reproduction. Higher values occurred in September, which may be due to lipid storage for overwintering. Wax esters were the major lipid class accounting for about 50% of total lipids in age-group 0 animals from July and August. Phospholipids were the second largest lipid fraction with up to 46% in this age-group. The principal fatty acids of M. ovum from all age-groups were 22:6(n-3), 20:5(n-3) and 16:0. Wax ester fatty alcohols were dominated by 22:1(n-11) and 20:1(n-9) followed by moderate proportions of 16:0. The unique feature of M. ovum lipids was the high amount of free fatty alcohols originating probably from the dietary wax esters. In May, free alcohols exhibited the highest mean proportion with 14.6% in age-group 0 animals. We present the first data describing a detailed free fatty alcohol composition in zooplankton. This composition was very different from the alcohol composition of M. ovum wax esters because of the predominance of the long-chain monounsaturated 22:1 (n-11) alcohol accounting for almost 100% of total free alcohols in some samples. The detailed lipid composition clearly reflected feeding of M. ovum on the herbivorous calanoid species, Calanus glacialis and C. finmarchicus, the abundant members of the zooplankton community in Kongsfjorden. Other copepod species or prey items seem to be less important for M. ovum.

Mesozooplankton of the northern Barents Sea in October 1998

Qualitative and quantitative mesozooplankton composition was examined on materials collected during an expedition carried out in October 1998 onboard the research icebreaker Akademik Fedorov. At different stations number of species varied from 25 to 33; wet biomass - from 20 to 109 g/m**2. Flux of autochthonous organic matter through plankton communities calculated from data on structural and functional analysis was from 2 to 40 mg C/m**2/day.