Heterotrophic protists in the Central Arctic Ocean

Sherr, Evelyn B.; Sherr, Barry F.; Fessenden, Lynne

doi:10.1016/s0967-0645(97)00050-7

Cited by 138 publications

(82 citation statements)

References 44 publications

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“…The chl a concentrations and abundances of bacteria, viruses, phototrophic and heterotrophic flagellates and ciliates in the Arctic and Fjord communities examined were comparable to values reported in other Arctic studies (Sherr et al 1997, Lovejoy et al 2007, Säwström et al 2007b, Boras et al 2010. BP (bacterial production) was significantly lower in open Arctic waters than in Fjord waters (Table 1), where the temperature was higher.…”

Section: Characteristics Of the In Situ Arctic And Fjord Waterssupporting

confidence: 87%

Experimental evaluation of the warming effect on viral, bacterial and protistan communities in two contrasting Arctic systems

Lara

Arrieta²,

García-Zarandona³

et al. 2013

Aquat. Microb. Ecol.

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The effect of Arctic warming, which is 3 times faster than the global average, on microbial communities was evaluated experimentally to determine how increasing temperatures affect bacterial and viral abundance and production, protist community composition, and bacterial loss rates (bacterivory and lysis) in 2 contrasting Arctic marine systems. In July 2009, we collected samples from open Arctic waters in the Barents Sea and Atlantic-influenced waters in Isfjorden, Svalbard Islands (Fjord waters). The samples were used in 2 microcosm experiments at 7 temperatures, ranging from 1.0 to 10.0°C. In the open Arctic microbial community, collected at <1.0°C, bacterial and viral abundances, bacterial production and grazing rates due to protists increased significantly above 5.5°C, and remained at high values at even higher experimental temperatures. The abundance of protists, such as some heterotrophic pico/nanoflagellates, as well as some ciliates, also increased with warming. In contrast, the biomass of phototrophs decreased above 5.5°C. The water temperature in Fjord waters was 6.2°C at the time of sampling, and the microbial community showed smaller variations than the Arctic community. These results indicate that increases in temperature stimulate heterotrophic microbial biomass and activity compared to that of phototrophs, which has important implications for carbon and nutrient cycling in the system. In addition, open Arctic communities were more vulnerable to warming than those already adapted to the warmer Fjord waters influenced by Atlantic seawater.

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Section: Characteristics Of the In Situ Arctic And Fjord Waterssupporting

confidence: 87%

Experimental evaluation of the warming effect on viral, bacterial and protistan communities in two contrasting Arctic systems

Lara

Arrieta²,

García-Zarandona³

et al. 2013

Aquat. Microb. Ecol.

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“…Perhaps because of relatively high concentrations of labile DOM at this time of year, community respiration typically exceeds primary production, heterotrophic bacteria actively cycle labile DOM, and bacterial biomass is high (Cota et al 1996;Rich et al 1997;Sherr et al 1997), despite in situ temperatures remaining low and both bacterivory and viral mortality having a significant impact on bacterial production (Steward et al 1996;Sherr et al 1997).…”

Section: Discussionmentioning

confidence: 99%

Dynamic bacterial and viral response to an algal bloom at subzero temperatures

Yager

Connelly

Mortazavi

et al. 2001

Limnology & Oceanography

126

117

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New evidence suggests that cold-loving (psychrophilic) bacteria may be a dynamic component of the episodic bloom events of high-latitude ecosystems. Here we report the results of an unusually early springtime study of pelagic microbial activity in the coastal Alaskan Arctic. Heterotrophic bacterioplankton clearly responded to an algal bloom by doubling cell size, increasing the fraction of actively respiring cells (up to an unprecedented 84% metabolically active using redox dye CTC), shifting substrate-uptake capabilities from kinetic parameters better adapted to lower substrate concentrations to those more suited for higher concentrations, and more than doubling cell abundance. Community composition (determined by polymerase chain reaction/DGGE and nucleotide sequence analysis) also shifted over the bloom. Results support, for the first time with modern molecular methods, previous culture-based observations of bacterial community succession during Arctic algal blooms and confirm that previously observed variability in pelagic microbial activity can be linked to changes in community structure. During early bloom stages, virioplankton and bacterial abundance were comparable, suggesting that mortality due to phage infection was low at that time. The virus-to-bacteria ratio (VBR) increased 10-fold at the height of the bloom, however, suggesting an increased potential for bacterioplankton mortality resulting from viral infection. The peak in VBR coincided with observed shifts in both microbial activity and community structure. These early-season data suggest that substrate and virioplankton interactions may control the active microbial carbon cycling of this region.

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“…When assuming complete algivory, 32-55% and 20-60% of the annual primary production was consumed by ciliates in Disko Bay and the Kattegat, respectively. Furthermore, because heterotrophic dinoflagellates were found to be as important grazers as ciliates in both systems, it was concluded that protozooplankton at high latitudes are also important in the cycling of primary production and should be considered if carbon and nutrient cycling in these systems is to be understood.During the past decade it has been shown that ciliates and heterotrophic dinoflagellates are abundant in arctic marine waters; these protists have higher growth capacities than copepods from the genus Calanus, which traditionally have been considered the principal grazers associated with high latitudes (Andersen 1988;Nielsen and Hansen 1995;Hansen et al 1996;Sherr et al 1997;Levinsen et al 2000a). Furthermore, adult and nauplii of the Calanus species have been shown to preferentially feed on ciliates and dinoflagellates (Barthel 1988;Ohman and Runge 1994; Levinsen et al 1 To whom correspondence should be addressed.…”

mentioning

confidence: 99%

“…During the past decade it has been shown that ciliates and heterotrophic dinoflagellates are abundant in arctic marine waters; these protists have higher growth capacities than copepods from the genus Calanus, which traditionally have been considered the principal grazers associated with high latitudes (Andersen 1988;Nielsen and Hansen 1995;Hansen et al 1996;Sherr et al 1997;Levinsen et al 2000a). Furthermore, adult and nauplii of the Calanus species have been shown to preferentially feed on ciliates and dinoflagellates (Barthel 1988;Ohman and Runge 1994;Levinsen et al 2000b;Turner et al 2001).…”

mentioning

confidence: 99%

The trophic role of marine pelagic ciliates and heterotrophic dinoflagellates in arctic and temperate coastal ecosystems: A cross‐latitude comparison

Levinsen¹,

Nielsen²

2002

Limnology & Oceanography

136

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We compared seasonal studies of ciliates and heterotrophic dinoflagellates conducted in Disko Bay (West Greenland, ϳ69ЊN) and the Kattegat (Denmark, ϳ56ЊN). In both systems, ciliates and heterotrophic dinoflagellates were important components of the plankton. Their biomass was minute in the winter (October to April) in Disko Bay compared to the Kattegat, but from May to August/September, the biomass and composition of the ciliate and heterotrophic dinoflagellate assemblages were similar in the two systems. The seasonal biomass pattern was unimodal and bimodal for Disko Bay and the Kattegat, respectively. To evaluate top-down versus bottom-up control, experimentally derived maximum estimates of protozooplankton growth rates and copepod predation capacities from the study sites were applied to biomass data. This analysis showed that the effect of copepods was significant but that ciliates and heterotrophic dinoflagellates could effectively exploit prey during periods when top-down pressure was relaxed. In Disko Bay, a high copepod biomass in spring is primarily caused by migration of an overwintering copepod population from deep waters into the photic zone prior to the spring bloom. We suggest that ''regulation windows'' for the protozooplankton are present even during the spring bloom when copepods occur at their peak levels because of food saturation. Bottom-up regulation occurred during the winter and occasionally when copepod predation pressure relaxed, but it was difficult to separate food limitation from the effect of temperature. Multiple regression analysis supports the notion that ciliate and heterotrophic dinoflagellate biomass changed seasonally according to both top-down and bottom-up regulation, as well as to temperature control. Protozooplankton growth estimates were also used to calculate the fraction of primary production processed by the ciliates and heterotrophic dinoflagellates. When assuming complete algivory, 32-55% and 20-60% of the annual primary production was consumed by ciliates in Disko Bay and the Kattegat, respectively. Furthermore, because heterotrophic dinoflagellates were found to be as important grazers as ciliates in both systems, it was concluded that protozooplankton at high latitudes are also important in the cycling of primary production and should be considered if carbon and nutrient cycling in these systems is to be understood.During the past decade it has been shown that ciliates and heterotrophic dinoflagellates are abundant in arctic marine waters; these protists have higher growth capacities than copepods from the genus Calanus, which traditionally have been considered the principal grazers associated with high latitudes (Andersen 1988;Nielsen and Hansen 1995;Hansen et al. 1996;Sherr et al. 1997;Levinsen et al. 2000a). Furthermore, adult and nauplii of the Calanus species have been shown to preferentially feed on ciliates and dinoflagellates (Barthel 1988;Ohman and Runge 1994; Levinsen et al. 1 To whom correspondence should be addressed. Present address: Unive...

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Heterotrophic protists in the Central Arctic Ocean

Cited by 138 publications

References 44 publications

Experimental evaluation of the warming effect on viral, bacterial and protistan communities in two contrasting Arctic systems

Experimental evaluation of the warming effect on viral, bacterial and protistan communities in two contrasting Arctic systems

Dynamic bacterial and viral response to an algal bloom at subzero temperatures

The trophic role of marine pelagic ciliates and heterotrophic dinoflagellates in arctic and temperate coastal ecosystems: A cross‐latitude comparison

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