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Karl-otto Rothhaupt - One of the best experts on this subject based on the ideXlab platform.
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Calanoid copepod grazing affects plankton size structure and composition in a deep, large lake
Journal of Plankton Research, 2019Co-Authors: Alessandra Janina Kunzmann, Harald Ehret, Elizabeth Yohannes, Dietmar Straile, Karl-otto RothhauptAbstract:Abstract Cultural oligotrophication is expected to shift lake zooplankton to become dominated by Calanoid copepods. Hence, understanding the influence of Calanoids on the taxonomic and size structure of the lower plankton food web is crucial for predicting the effects of oligotrophication on energy fluxes in these systems. We studied the effect of an omnivorous Calanoid, Eudiaptomus gracilis, on the lower planktonic food web using an in situ incubation approach in large and deep Lake Constance. We show that E. gracilis significantly reduced ciliate, phytoplankton, rotifer, but increased bacteria biovolume. Highest clearance rates were observed for ciliates whose biovolume declines may have caused a release of predation pressure on bacteria. E. gracilis grazing shifted the size structure of the phytoplankton community by reducing mean phytoplankton cell size (directional selection) and simultaneously increasing cell size variance (disruptive selection). Ciliate cell sizes experienced a similar selective regime in one of the experiments, whereas in the other two experiments, no change of size structure was detected. Results suggest strong influences of E. gracilis grazing on the lower plankton food web and a significant shift in phytoplankton size structure. For evaluating detailed effects of omnivorous consumers on plankton size structure, cascading interactions need to be considered.
Holger Auel - One of the best experts on this subject based on the ideXlab platform.
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Who is who in the tropical Atlantic? Functional traits, ecophysiological adaptations and life strategies in tropical Calanoid copepods
Progress in Oceanography, 2019Co-Authors: Lena Teuber, Wilhelm Hagen, Maya Bode, Holger AuelAbstract:Abstract It is well known that tropical oceans harbour a rich biodiversity of Calanoid copepods. However, their functional traits, ecophysiological adaptations and life strategies have hardly been studied. In polar, temperate and upwelling ecosystems, Calanoid copepods show a variety of specific life strategies in relation to seasonal changes and physical dynamics of their respective habitats. In contrast, it was assumed that epipelagic zooplankton communities in tropical oceans had developed rather uniform life-history traits, due to a low productivity and the lack of a pronounced seasonality. This article reviews ecophysiological characteristics of Calanoid copepods from epi- to bathypelagic depths in the eastern tropical Atlantic based on a variety of methodological approaches. Five different types of life strategies could be identified for abundant tropical Calanoid copepod species. Pronounced oxygen minimum zones, prominent in many (sub-)tropical regions, are apparently an important driver for the development of copepods' adaptations and life-history traits. Our results emphasize that life strategies of tropical copepods are more complex and diverse than previously assumed. This review clearly identifies certain copepod groups that are better adapted to hypoxia than others and may thus cope with intensifying and expanding oxygen minimum zones in a future ocean.
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Complex trophic interactions of Calanoid copepods in the Benguela upwelling system
Journal of Sea Research, 2014Co-Authors: Anna Schukat, Holger Auel, Lena Teuber, Niko Lahajnar, Wilhelm HagenAbstract:Abstract Life-cycle adaptations, dietary preferences and trophic levels of Calanoid copepods from the northern Benguela Current off Namibia were determined via lipid classes, marker fatty acids and stable isotope analyses, respectively. Trophic levels of copepod species were compared to other zooplankton and top consumers. Lipid class analyses revealed that three of the dominant Calanoid copepod species stored wax esters, four accumulated triacylglycerols and another three species were characterised by high phospholipid levels. The two biomarker approaches (via fatty acids and stable isotopes) revealed a complex pattern of trophic positions for the various copepod species, but also highlighted the dietary importance of diatoms and dinoflagellates. Calanoides carinatus and Nannocalanus minor occupied the lowest trophic level (predominantly herbivorous) corresponding to high amounts of fatty acid markers for diatoms (e.g. 16:1(n − 7)) and dinoflagellates (e.g. 18:4(n − 3)). These two copepod species represent the classical link between primary production and higher trophic levels. All other copepods belonged to secondary or even tertiary (some deep-sea copepods) consumers. The Calanoid copepod species cover the entire range of δ 15 N ratios, as compared to δ 15 N ratios of all non-Calanoid taxa investigated, from salps to adult fish. These data emphasise that the trophic roles of Calanoid copepods are far more complex than just interlinking primary producers with pelagic fish, which should also be considered in the process of developing realistic food-web models of coastal upwelling systems.
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Energetics and carbon budgets of dominant Calanoid copepods in the northern Benguela upwelling system
Journal of Experimental Marine Biology and Ecology, 2013Co-Authors: Anna Schukat, Lena Teuber, Wilhelm Hagen, Norbert Wasmund, Holger AuelAbstract:Abstract Respiration rates of 16 Calanoid copepod species from the northern Benguela upwelling system were measured on board RRS Discovery in September/October 2010 to determine their energy requirements and assess their significance in the carbon cycle. Individual respiration rates were standardised to a mean copepod body mass and a temperature regime typical of the northern Benguela Current. These adjusted respiration rates revealed two different activity levels (active and resting) in copepodids C5 of Calanoides carinatus and females of Rhincalanus nasutus , which reduced their metabolism during dormancy by 82% and 62%, respectively. An allometric function (I max ) and an energy budget approach were performed to calculate ingestion rates. I max generally overestimated the ingestion rates derived from the energy budget approach by > 75%. We suggest that the energy budget approach is the more reliable approximation with a total Calanoid copepod (mainly females) consumption of 78 mg C m − 2 d − 1 in neritic regions and 21 mg C m − 2 d − 1 in oceanic regions. The two primarily herbivorous copepods C. carinatus (neritic) and Nannocalanus minor (oceanic) contributed 83% and 5%, respectively, to total consumption by Calanoid copepods. Locally, C. carinatus can remove up to 90% of the diatom biomass daily. In contrast, the maximum daily removal of dinoflagellate biomass by N. minor was 9%. These estimates imply that C. carinatus is an important primary consumers in the neritic province of the northern Benguela system, while N. minor has little grazing impact on phytoplankton populations further offshore. Data on energy requirements and total consumption rates of dominant Calanoid copepods of this study are essential for the development of realistic carbon budgets and food-web models for the northern Benguela upwelling system.
Frederic Ibanez - One of the best experts on this subject based on the ideXlab platform.
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monitoring marine plankton ecosystems ii long term changes in north sea Calanoid copepods in relation to hydro climatic variability
Marine Ecology Progress Series, 2004Co-Authors: Gregory Beaugrand, Frederic IbanezAbstract:Recently, a framework has been proposed to monitor plankton ecosystems in the North Atlantic and adjacent seas using Calanoid copepod species. In this study, we use this framework to investigate, at the community structure (Calanoid copepod) level, the long-term changes in plankton ecosystems related to hydro-climatic variability in the North Sea during the period 1958-1999. A chronology of ecological events that occurred in the North Sea is outlined. In addition to the long- term and year-to-year variability, this study reveals that North Sea plankton ecosystems had 2 dynamic regimes during the period 1958-1999: a cold-biological (1962-1982) and a warm-biological dynamic regime (1984-1999). The impact of the regime shift on the community structure of Calanoid copepods and total diversity (as mean number of Calanoid copepod species per continuous plankton recorder sample) is detectable in the stratified regions of the North Sea after ca. 1983. This study reveals that the regime shift resulted from the conjunction of both local and regional hydro-climatic forcing and a change in the location of an oceanic biogeographical boundary in the north-east Atlantic Ocean. Results indicate a strong dependence of ecological processes in the North Sea to both hydro-climatic and biological variability in the north-east Atlantic Ocean. If the current climate warming persists, results suggest that this may continue to alter the structure of North Sea ecosys- tems and lead to other regime shifts, thus making it very challenging to predict future responses of North Sea pelagic ecosystems to climate change.
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Diversity of Calanoid copepods in the North Atlantic and adjacent seas: species associations and biogeography
Marine Ecology Progress Series, 2002Co-Authors: Gregory Beaugrand, Frederic Ibanez, J. Alistair Lindley, Philip C. ReidAbstract:Present-day patterns in pelagic biodiversity are the result of the interaction of many fac- tors acting at different scales. Developing an understanding of the processes that regulate the diver- sity of oceanic ecosystems is thus challenging. In this study, diversity of Calanoid copepods was decomposed into species associations by means of the recent 'indicator value method' and multivari- ate analyses. For the first time, at an oceanic basin scale and with a spatial resolution approaching the mesoscale, species associations of Calanoid copepods have been identified. Nine species associations were determined and have enabled us, (1) to improve the ecological partitioning of this region, and (2) to identify the main factors that regulate pelagic biodiversity in this area. It is shown that temper- ature, hydrodynamics, stratification and seasonal variability of the environment are likely to be the main factors contributing to the ecological regulation of diversity of Calanoid copepods. The similar geographical pattern evident between currents/water masses and the species associations suggest that the species groups may be used as an environmental indicator to evaluate long-term changes in the marine environment related to climate change and other increasing human-induced influences.
Wilhelm Hagen - One of the best experts on this subject based on the ideXlab platform.
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Who is who in the tropical Atlantic? Functional traits, ecophysiological adaptations and life strategies in tropical Calanoid copepods
Progress in Oceanography, 2019Co-Authors: Lena Teuber, Wilhelm Hagen, Maya Bode, Holger AuelAbstract:Abstract It is well known that tropical oceans harbour a rich biodiversity of Calanoid copepods. However, their functional traits, ecophysiological adaptations and life strategies have hardly been studied. In polar, temperate and upwelling ecosystems, Calanoid copepods show a variety of specific life strategies in relation to seasonal changes and physical dynamics of their respective habitats. In contrast, it was assumed that epipelagic zooplankton communities in tropical oceans had developed rather uniform life-history traits, due to a low productivity and the lack of a pronounced seasonality. This article reviews ecophysiological characteristics of Calanoid copepods from epi- to bathypelagic depths in the eastern tropical Atlantic based on a variety of methodological approaches. Five different types of life strategies could be identified for abundant tropical Calanoid copepod species. Pronounced oxygen minimum zones, prominent in many (sub-)tropical regions, are apparently an important driver for the development of copepods' adaptations and life-history traits. Our results emphasize that life strategies of tropical copepods are more complex and diverse than previously assumed. This review clearly identifies certain copepod groups that are better adapted to hypoxia than others and may thus cope with intensifying and expanding oxygen minimum zones in a future ocean.
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Complex trophic interactions of Calanoid copepods in the Benguela upwelling system
Journal of Sea Research, 2014Co-Authors: Anna Schukat, Holger Auel, Lena Teuber, Niko Lahajnar, Wilhelm HagenAbstract:Abstract Life-cycle adaptations, dietary preferences and trophic levels of Calanoid copepods from the northern Benguela Current off Namibia were determined via lipid classes, marker fatty acids and stable isotope analyses, respectively. Trophic levels of copepod species were compared to other zooplankton and top consumers. Lipid class analyses revealed that three of the dominant Calanoid copepod species stored wax esters, four accumulated triacylglycerols and another three species were characterised by high phospholipid levels. The two biomarker approaches (via fatty acids and stable isotopes) revealed a complex pattern of trophic positions for the various copepod species, but also highlighted the dietary importance of diatoms and dinoflagellates. Calanoides carinatus and Nannocalanus minor occupied the lowest trophic level (predominantly herbivorous) corresponding to high amounts of fatty acid markers for diatoms (e.g. 16:1(n − 7)) and dinoflagellates (e.g. 18:4(n − 3)). These two copepod species represent the classical link between primary production and higher trophic levels. All other copepods belonged to secondary or even tertiary (some deep-sea copepods) consumers. The Calanoid copepod species cover the entire range of δ 15 N ratios, as compared to δ 15 N ratios of all non-Calanoid taxa investigated, from salps to adult fish. These data emphasise that the trophic roles of Calanoid copepods are far more complex than just interlinking primary producers with pelagic fish, which should also be considered in the process of developing realistic food-web models of coastal upwelling systems.
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Energetics and carbon budgets of dominant Calanoid copepods in the northern Benguela upwelling system
Journal of Experimental Marine Biology and Ecology, 2013Co-Authors: Anna Schukat, Lena Teuber, Wilhelm Hagen, Norbert Wasmund, Holger AuelAbstract:Abstract Respiration rates of 16 Calanoid copepod species from the northern Benguela upwelling system were measured on board RRS Discovery in September/October 2010 to determine their energy requirements and assess their significance in the carbon cycle. Individual respiration rates were standardised to a mean copepod body mass and a temperature regime typical of the northern Benguela Current. These adjusted respiration rates revealed two different activity levels (active and resting) in copepodids C5 of Calanoides carinatus and females of Rhincalanus nasutus , which reduced their metabolism during dormancy by 82% and 62%, respectively. An allometric function (I max ) and an energy budget approach were performed to calculate ingestion rates. I max generally overestimated the ingestion rates derived from the energy budget approach by > 75%. We suggest that the energy budget approach is the more reliable approximation with a total Calanoid copepod (mainly females) consumption of 78 mg C m − 2 d − 1 in neritic regions and 21 mg C m − 2 d − 1 in oceanic regions. The two primarily herbivorous copepods C. carinatus (neritic) and Nannocalanus minor (oceanic) contributed 83% and 5%, respectively, to total consumption by Calanoid copepods. Locally, C. carinatus can remove up to 90% of the diatom biomass daily. In contrast, the maximum daily removal of dinoflagellate biomass by N. minor was 9%. These estimates imply that C. carinatus is an important primary consumers in the neritic province of the northern Benguela system, while N. minor has little grazing impact on phytoplankton populations further offshore. Data on energy requirements and total consumption rates of dominant Calanoid copepods of this study are essential for the development of realistic carbon budgets and food-web models for the northern Benguela upwelling system.
Alessandra Janina Kunzmann - One of the best experts on this subject based on the ideXlab platform.
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Calanoid copepod grazing affects plankton size structure and composition in a deep, large lake
Journal of Plankton Research, 2019Co-Authors: Alessandra Janina Kunzmann, Harald Ehret, Elizabeth Yohannes, Dietmar Straile, Karl-otto RothhauptAbstract:Abstract Cultural oligotrophication is expected to shift lake zooplankton to become dominated by Calanoid copepods. Hence, understanding the influence of Calanoids on the taxonomic and size structure of the lower plankton food web is crucial for predicting the effects of oligotrophication on energy fluxes in these systems. We studied the effect of an omnivorous Calanoid, Eudiaptomus gracilis, on the lower planktonic food web using an in situ incubation approach in large and deep Lake Constance. We show that E. gracilis significantly reduced ciliate, phytoplankton, rotifer, but increased bacteria biovolume. Highest clearance rates were observed for ciliates whose biovolume declines may have caused a release of predation pressure on bacteria. E. gracilis grazing shifted the size structure of the phytoplankton community by reducing mean phytoplankton cell size (directional selection) and simultaneously increasing cell size variance (disruptive selection). Ciliate cell sizes experienced a similar selective regime in one of the experiments, whereas in the other two experiments, no change of size structure was detected. Results suggest strong influences of E. gracilis grazing on the lower plankton food web and a significant shift in phytoplankton size structure. For evaluating detailed effects of omnivorous consumers on plankton size structure, cascading interactions need to be considered.