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Journal ArticleDOI

Temperature and phytoplankton size class biomass drives the zooplankton food web dynamics in the Indian Ocean sector of the Southern Ocean

01 Apr 2019-Polar Biology (Springer Berlin Heidelberg)-Vol. 42, Iss: 4, pp 823-829
TL;DR: During the austral summer of 2015, in the Indian sector of the Southern Ocean, the vertical profiles of zooplankton community structures between 0 and 1000 m were investigated using a Hydro-Bios, Multi Plankton Sampler, and abundance was numerically dominated by calanoids and cyclopoids.
Abstract: The abundance and vertical distribution of zooplankton community structure in the mesopelagic zone are important to better understand their role in the food web dynamics in the Southern Ocean ecosystem. During the austral summer of 2015, in the Indian sector of the Southern Ocean, the vertical profiles of zooplankton community structures between 0 and 1000 m were investigated using a Hydro-Bios, Multi Plankton Sampler (200-µm mesh, 0.25 m2 mouth area). A strong contrast in terms of population structure and biovolume was observed between the Subtropical Front and the Polar Front 2. High zooplankton abundance was recorded on each transect in the Polar Front. Zooplankton abundance was numerically dominated by calanoids and cyclopoids, constituting approximately 86% of the total zooplankton count. Abundance of copepods were the highest within the mixed layer depth. Under warm, stratified conditions, surface waters were dominated by picophytoplankton. These conditions result in the zooplankton being dominated by small crustaceans. This long, inefficient food web is of poor nutritional quality, supporting a smaller biomass of higher trophic levels. In contrast, under cold and well mixed conditions, surface waters were dominated by microphytoplankton. These conditions result in the zooplankton being dominated by crustaceans, such as large copepods. This short, nutritionally rich and efficient food web supports higher trophic levels.
Citations
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Journal ArticleDOI
01 Nov 1966-Nature
TL;DR: Biology of the Antarctic Seas II as mentioned in this paper, edited by George A. Llano, was published by the American Geophysical Union of the National Academy of Sciences (AGEUS).
Abstract: Biology of the Antarctic Seas II Edited by George A. Llano. (Antarctic Research Series, Vol. 5. Publication No. 1297.) Pp. xi + 280. (Washington, D.C.: American Geophysical Union of the National Academy of Sciences—National Research Council, 1965.) $12.

226 citations

Journal ArticleDOI
TL;DR: In this paper, the authors evaluated how 10 µm of polyethylene microspheres can be ingested by Artemia salina larvae within the first 7 days of the life cycle, and the impact on their health.
Abstract: In the present study, it has been evaluated how 10 µm of polyethylene microspheres can be ingested by Artemia salina (Linnaeus, 1758) larvae within the first 7 days of the life cycle, and the impact on their health. Twelve A. salina larvae (instar I) groups were exposed to different microplastics (MPs) concentrations (0-1-10-102-103-104 MPs/mL), with and without Dunaliella salina as a food source. The results highlighted that A. salina larvae ingest MPs in relation to the exposure times in a dose-dependent manner and are significantly influenced by food availability. The highest contamination found was 306.2 MPs/individual at 104 MPs/mL exposure without a food source. No MPs were found in the presence of the food source from 1 to 102 MPs/mL, while contamination was detected at all concentrations of MPs without a food source. The worst effect on the developmental stages was evaluated at 168 h with a food source, with a delay compared to the control of I and II instars at 103 and 104 MPs/mL, respectively. Furthermore, microalgal feeding was significantly reduced for about 50% in the presence of 104 MPs/mL. These results highlight that aquatic microplastics pollution could affect the A. salina’s feeding behavior and life cycle.

29 citations

Journal ArticleDOI
TL;DR: Future decreasing TDs under climate warming may decouple crustacean grazing pressure on phytoplankton, which may further deteriorate the water quality.

12 citations

Journal ArticleDOI
TL;DR: In this article, the authors developed a time-dynamic food web model for the Kerguelen Plateau using Ecopath with Ecosim to explore likely drivers of change in this relatively data-poor region and evaluated the environmental and human drivers of food web dynamics in the region by calibrating it with French and Australian fisheries data from 1997-2018 and biomass data for the period 1986-2018.
Abstract: Understanding the impacts of climate and fishing on marine systems is important for ecosystem-based management in the Southern Ocean, but can be difficult to evaluate due to patchy data in space and time. We developed the first time-dynamic food web model for the Kerguelen Plateau using Ecopath with Ecosim to explore likely drivers of change in this relatively data-poor region. The Kerguelen Plateau is located at the centre of intersecting frontal systems and is inhabited by one of the largest populations of the commercially important Patagonian toothfish. We used this model to evaluate the environmental and human drivers of food web dynamics in the region by calibrating it with French and Australian fisheries data from 1997–2018 and biomass data for the period 1986–2018. Fishing was not identified as a driver of food web dynamics within this model, which could indicate that current management strategies are sustainable. A correlation analysis with environmental parameters likely to drive food web dynamics (sea surface temperature, zonal wind, Southern Annular Mode and chlorophyll a concentration) highlighted cool sea surface temperature, higher zonal wind speeds and negative phases of the Southern Annular Mode as important drivers of change, particularly during the summer. As the Southern Ocean is predicted to warm and winds are expected to intensify under future climate change, our study illustrates the importance of considering environmental change in ecosystem management.

11 citations


Cites background from "Temperature and phytoplankton size ..."

  • ...The resulting zooplankton composition is dominated by large copepods, leading to a short, energy-efficient pathway for predators (Quéguiner, 2013; Venkataramana et al., 2019)....

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Journal ArticleDOI
TL;DR: The changes in these parameters were distinctly marked by change points around the year 2012, resulting in a 0.83°C increase in SST, a0.3 PSU increase in salinity, and a decrease in CHL in excess of 0.4 mg m-3 as mentioned in this paper.
Abstract: Sea surface temperature (SST), salinity, and chlorophyll concentration (CHL) have changed in the US Northeast Shelf ecosystem over recent decades. The changes in these parameters were distinctly marked by change points around the year 2012 resulting in a 0.83°C increase in SST, a 0.3 PSU increase in salinity, and decrease in CHL in excess of 0.4 mg m-3. Where temperature and salinity shifted in mean level around their respective change points, CHL declined in a more monotonic fashion. Modelled data suggest that the shift in CHL resulted in a greater contribution of pico- and nanophytoplankton and a decreased contribution of microphytoplankton to overall CHL. Complementary estimates of the contribution of different phytoplankton functional types suggest a diminished contribution of diatoms to the phytoplankton community. Hence, not only is there evidence of a decline in the overall primary production capacity of the ecosystem, but also evidence of a fundamental change in the size and quality of phytoplankton supporting food webs. Two ecosystem responses to the observed changes in SST, salinity, and CHL were analyzed. Both length and weight at age have declined for a number of species, and both measures of growth appear to be negatively associated with temperature and positively associated with CHL. Biomass of fish and macroinvertebrates has declined in recent years, with a decrease in pelagic species associated with a decrease in CHL, while the decline in demersal species was more associated with an increase in temperature. Collectively, these ecosystem changes appear to be the result of the complex interactions of both thermal effects and changes at the base of the food web.

8 citations

References
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Journal ArticleDOI
01 May 1995
TL;DR: In this article, large-scale features of the Antarctic Circumpolar Current (ACC) were described using all historical hydrographic data available from the Southern Ocean, and the geopotential anomaly of the sea surface relative to 1000 db reveals the highly-sheared eastward flow of the ACC and the strong steering of the current by the ridge system around Antarctica.
Abstract: Large-scale features of the Antarctic Circumpolar Current (ACC) are described using all historical hydrographic data available from the Southern Ocean. The geopotential anomaly of the sea surface relative to 1000 db reveals the highly-sheared eastward flow of the ACC and the strong steering of the current by the ridge system around Antarctica. The near-surface property distributions differentiate the ACC waters from the warmer and saltier waters of the subtropical regimes. The Subtropical Front (STF), interrupted only by South America, marks the northern most extent of subantarctic waters. Distributions of properties on isopycnal surfaces show an abrupt end to the characteristic signal of the Upper Circumpolar Deep Water (UCDW), as this water mass shoals southward and is entrained into the surface mixed layer. This sharp water mass boundary nearly coincides with the southernmost circumpolar streamline passing through Drake Passage. To its south are the weakly-sheared circulations of the subpolar regime. Inspection of many hydrographic crossings of this transition reveals that the poleward edge of the UCD W signal is a reasonable definition of the southern boundary of the ACC. At Drake Passage, three deep-reaching fronts account for most of the ACC transport. Well-established indicators of the Subantarctic Front and Polar Front are traced unbroken around Antarctica. The third deep-reaching front observed to the south of the Polar Front at Drake Passage also continues with similar characteristics as a circumpolar feature. It is called here the southern ACC front. Stations from multiple synoptic transects of these circumpolar fronts are used to describe the average property structure within each ACC zone. Between the STF and the southern boundary of the ACC, the shear transport of the circumpolar current above 3000 m is at all longitudes about 100 Sv (1 Sv = 106 m3 s−) eastward.

2,513 citations

Journal ArticleDOI
TL;DR: In this article, the distribution and composition of phytoplankton stocks in relation to water masses were studied during the SO-JGOFS cruise of R.V. Polarstern in the Atlantic sector of the Southern Ocean in October/November 1992.
Abstract: The distribution and composition of phytoplankton stocks in relation to water masses were studied during the SO-JGOFS cruise of R.V. Polarstern in the Atlantic sector of the Southern Ocean in October/November 1992. The cruise comprised one west-to-east transect along the ice edge from 49°W to 6°W and several meridional transects along 6°W that extended from the closed pack ice of the Weddell Sea, across the southern Antarctic Circumpolar Current (ACC) and into the Polar Frontal Zone. Chlorophyll (chi a concentrations, temperature and salinity were recorded continuously in surface water during the transects. Vertical distribution and species composition of microplankton were assessed microscopically in discrete water samples collected at stations. Contrary to expectations, no significant enhancement of phytoplankton biomass was found in the vicinity of the retreating ice cover. Melt-water-influenced zones were indicated by low salinity but also by abundance of characteristic sea-ice species such as Nitzschia closterium and N. prolongatoides, but chlorophyll concentrations averaged only 0.3 mg chi a m−3 and barely increased during the spring. Values were even lower and remained constant in the southern ACC (ca 0.2 mg chi a m−3). In contrast, large phytoplankton blooms developed during the 6 weeks of investigation in the region of the Polar Front (PFr), from 0.7 to > 4 mg chi a m−3. Three distinct blooms extended below 70 m depth, each dominated by a different diatom species (Fragilariopsis kerguelensis, Corethron inerme and C. criophilum). We speculate that the large phytoplankton stocks below 40 m depth are a result of subduction of surface layers as sinking and in situ growth can be ruled out. The factors leading to the accumulation of high phytoplankton stocks in the PFr (up to 270 mg chi m−2), but not in the meltwater zones or in the front between ACC and Weddell Gyre, are not clear, but higher iron concentrations in the former region seem to have played a role.

239 citations

Journal ArticleDOI
01 Nov 1966-Nature
TL;DR: Biology of the Antarctic Seas II as mentioned in this paper, edited by George A. Llano, was published by the American Geophysical Union of the National Academy of Sciences (AGEUS).
Abstract: Biology of the Antarctic Seas II Edited by George A. Llano. (Antarctic Research Series, Vol. 5. Publication No. 1297.) Pp. xi + 280. (Washington, D.C.: American Geophysical Union of the National Academy of Sciences—National Research Council, 1965.) $12.

226 citations


"Temperature and phytoplankton size ..." refers background in this paper

  • ...Furthermore, Knox (2007) stated that copepods usually dominate the SO mesozooplankton assemblages both numerically in terms of biomass and abundance distribution....

    [...]

Journal ArticleDOI
TL;DR: Both the low summer temperatures and short primary production season seem to dictate a long life cycle for C. acutus, and O. similis appears to remain in the epipelagic and reproduce there year-round, although the food sources which sustain this are still uncertain.

208 citations


"Temperature and phytoplankton size ..." refers background or result in this paper

  • ...This same trend has been also noted by other Antarctic researchers (Atkinson 1998; Dubischar et al....

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  • ...The success of numerically dominant species Calanoides acutus, Calanus propinquus, and R. gigas were likely due to their different life strategies (Atkinson 1998)....

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  • ...(Atkinson 1998)....

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  • ...1996; Atkinson 1998; Dubischar et al....

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