A missing piece in the Arctic food web puzzle? Stomach contents of Greenland sharks sampled in Svalbard, Norway

The ocean surface microlayer (SML), with physicochemical characteristics different from those of subsurface waters (SSW), results in dense and active viral and microbial communities that may favor virus–host interactions. Conversely, wind speed and/or UV radiation could adversely affect virus infection. Furthermore, in polar regions, organic and inorganic nutrient inputs from melting ice may increase microbial activity in the SML. Since the role of viruses in the microbial food web of the SML is poorly understood in polar oceans, we aimed to study the impact of viruses on prokaryotic communities in the SML and in the SSW in Arctic and Antarctic waters. We hypothesized that a higher viral activity in the SML than in the SSW in both polar systems would be observed. We measured viral and prokaryote abundances, virus-mediated mortality on prokaryotes, heterotrophic and phototrophic nanoflagellate abundance, and environmental factors. In both polar zones, we found small differences in environmental factors between the SML and the SSW. In contrast, despite the adverse effect of wind, viral and prokaryote abundances and virus-mediated mortality on prokaryotes were higher in the SML than in the SSW. As a consequence, the higher carbon flux released by lysed cells in the SML than in the SSW would increase the pool of dissolved organic carbon (DOC) and be rapidly used by other prokaryotes to grow (the viral shunt). Thus, our results suggest that viral activity greatly contributes to the functioning of the microbial food web in the SML, which could influence the biogeochemical cycles of the water column.

Download Full-text

Contrasting pelagic ecosystem functioning in eastern and western Baffin Bay revealed by trophic network modeling

Elem Sci Anth ◽

10.1525/elementa.397 ◽

2020 ◽

Vol 8 ◽

Cited By ~ 2

Author(s):

Blanche Saint-Béat ◽

Brian D. Fath ◽

Cyril Aubry ◽

Jonathan Colombet ◽

Julie Dinasquet ◽

...

Keyword(s):

Carbon Cycle ◽

Food Web ◽

Biological Data ◽

The Arctic ◽

Ecosystem Structure ◽

Carbon Export ◽

Baffin Bay ◽

Planktonic Food ◽

Carbon Transfer ◽

Current Flows

Baffin Bay, located at the Arctic Ocean’s ‘doorstep’, is a heterogeneous environment where a warm and salty eastern current flows northwards in the opposite direction of a cold and relatively fresh Arctic current flowing along the west coast of the bay. This circulation affects the physical and biogeochemical environment on both sides of the bay. The phytoplanktonic species composition is driven by its environment and, in turn, shapes carbon transfer through the planktonic food web. This study aims at determining the effects of such contrasting environments on ecosystem structure and functioning and the consequences for the carbon cycle. Ecological indices calculated from food web flow values provide ecosystem properties that are not accessible by direct in situ measurement. From new biological data gathered during the Green Edge project, we built a planktonic food web model for each side of Baffin Bay, considering several biological processes involved in the carbon cycle, notably in the gravitational, lipid, and microbial carbon pumps. Missing flow values were estimated by linear inverse modeling. Calculated ecological network analysis indices revealed significant differences in the functioning of each ecosystem. The eastern Baffin Bay food web presents a more specialized food web that constrains carbon through specific and efficient pathways, leading to segregation of the microbial loop from the classical grazing chain. In contrast, the western food web showed redundant and shorter pathways that caused a higher carbon export, especially via lipid and microbial pumps, and thus promoted carbon sequestration. Moreover, indirect effects resulting from bottom-up and top-down control impacted pairwise relations between species differently and led to the dominance of mutualism in the eastern food web. These differences in pairwise relations affect the dynamics and evolution of each food web and thus might lead to contrasting responses to ongoing climate change.

Download Full-text

Trace Metals (As, Cd, Cu, Fe, and Zn) in Arctic cod, Boreogadus saida, and Selected Zooplankton from Strathcona Sound, Northern Baffin Island

Journal of the Fisheries Research Board of Canada ◽

10.1139/f76-340 ◽

1976 ◽

Vol 33 (12) ◽

pp. 2836-2840 ◽

Cited By ~ 61

Author(s):

Arne Bohn ◽

R. O. McElroy

Keyword(s):

Body Weight ◽

Trace Metals ◽

Stomach Contents ◽

Bottom Trawl ◽

The Arctic ◽

Baffin Island ◽

Boreogadus Saida ◽

Arctic Cod ◽

Planktonic Copepods ◽

The Difference

Arctic cod (Boreogadus saida) were captured by bottom trawl at depths of 120–300 m. Zooplankton were obtained by bottom to surface tows from the Arctic cod habitat. Average concentrations of arsenic (As) and zinc (Zn) were higher in Arctic cod fillets than in livers from the same fish; cadmium (Cd) and iron (Fe) concentrations were higher in livers. The difference between copper (Cu) concentrations in muscle and liver was not significant. As and Zn in whole fish, and As in fillets from seven specimens, were positively correlated to body weight. Cu and Fe in whole fish were negatively correlated to body weight, whereas Cd was not related to body weight. Examination of Arctic cod stomach contents indicated that planktonic copepods were important in the diet. Cd levels were 5–8 times higher in the unsorted copepods than in the Arctic cod, whereas As, Cu, Fe, and Zn were higher in the fish than in the copepods.

Download Full-text

Upper thermal limits of cardiac function for Arctic cod Boreogadus saida , a key food web fish species in the Arctic Ocean

Journal of Fish Biology ◽

10.1111/jfb.12397 ◽

2014 ◽

Vol 84 (6) ◽

pp. 1781-1792 ◽

Cited By ~ 25

Author(s):

H. E. Drost ◽

E. C. Carmack ◽

A. P. Farrell

Keyword(s):

Cardiac Function ◽

Food Web ◽

Arctic Ocean ◽

Fish Species ◽

The Arctic ◽

Boreogadus Saida ◽

Arctic Cod ◽

Thermal Limits ◽

The Arctic Ocean

Download Full-text

Mercury in lichens and reindeer hair from Alaska: 2005–2007 pilot survey

Polar Record ◽

10.1017/s0032247409008353 ◽

2009 ◽

Vol 45 (4) ◽

pp. 368-374 ◽

Cited By ~ 5

Author(s):

James A. Lokken ◽

Gregory L. Finstad ◽

Kriya L. Dunlap ◽

Lawrence K. Duffy

Keyword(s):

Industrial Development ◽

Fire Regime ◽

The Arctic ◽

Metal Exposure ◽

Non Invasive ◽

The North ◽

Invasive Method ◽

Seward Peninsula ◽

Arctic Food Web ◽

Flooding Events

ABSTRACTReindeer and caribou are terrestrial herbivores, that feed on lichens and are used for commercial and subsistence food products. Caribou are a key component of the arctic food web and the bioaccumulation of toxic contaminants, such as mercury (Hg), needs to be monitored to establish a baseline as the arctic environment is impacted by both climate change and future industrial development. A changing climate in Alaska is influencing plant species composition, fire regime, melting and flooding events, and thus, impacting Hg bioavailability in the food chain. Industrial development in Asia is also projected to increase the atmospheric global pool of Hg from increased coal combustion. Reindeer, a domesticated representative of caribou, can be used as a terrestrial biomonitor for metal exposure. In this study total mercury concentrations were measured in lichens and in hair of grazing reindeer on defined ranges across Alaska to establish a baseline for future hypothesis development and testing regarding Hg deposition. The Hg mean level for Seward Peninsula lichens on the Davis Range was 37.4 ng g−1, on the Gray Range 47.1 ng g−1, on the Kakaruk Range 42.2 ng g−1, and 41.7 ng g−1 on the Noyakuk Range. Lichen Hg levels on St. Lawrence Island was 46.6 ng g−1. Methyl mercury levels in lichens were found to be below detection levels. Reindeer grazing on these ranges had mean Hg hair levels of 14.6 ng g−1 (Davis herd), 83.4 ng g−1 (Gray herd), and 40.3 ng g−1 (Noyakuk herd). Two reindeer on St. Lawrence Island had an average of Hg of 43.0 ng g−1. Sample sizes ranged from n = 2 to n = 11. Hg mean levels in lichen on Seward Peninsula were higher than Hg means of two ranges in northern Mongolia. The Hg levels observed in this study indicate that Hg levels in Alaska are low at this time and pose no risk to the health of reindeer or human subsistence harvesters. A significant relationship between Hg in lichens on the ranges and the Hg in reindeer on those ranges has not been established. There are insufficient data on Hg levels in many areas of the north and more information is needed on location specific and time trends in Hg concentrations. Lichens and reindeer hair provide a good, non-invasive method of monitoring metal exposure changes in Alaskan ecosystems.

Download Full-text