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  • ASLO (Association for the Sciences of Limnology and Oceanography)  (3)
  • Public Library of Science  (2)
  • Inter Research  (1)
  • 1
    Publication Date: 2021-03-30
    Description: Anthropogenic atmospheric loading of CO2 raises concerns about combined effects of increasing ocean temperature and acidification, on biological processes. In particular, the response of appendicularian zooplankton to climate change may have significant ecosystem implications as they can alter biogeochemical cycling compared to classical copepod dominated food webs. However, the response of appendicularians to multiple climate drivers and effect on carbon cycling are still not well understood. Here, we investigated how gelatinous zooplankton (appendicularians) affect carbon cycling of marine food webs under conditions predicted by future climate scenarios. Appendicularians performed well in warmer conditions and benefited from low pH levels, which in turn altered the direction of carbon flow. Increased appendicularians removed particles from the water column that might otherwise nourish copepods by increasing carbon transport to depth from continuous discarding of filtration houses and fecal pellets. This helps to remove CO2 from the atmosphere, and may also have fisheries implications.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 2
    Publication Date: 2017-04-13
    Description: The unabated rise in anthropogenic CO2 emissions is predicted to strongly influence the ocean's environment, increasing the mean sea-surface temperature by 4°C and causing a pH decline of 0.3 units by the year 2100. These changes are likely to affect the nutritional value of marine food sources since temperature and CO2 can influence the fatty (FA) and amino acid (AA) composition of marine primary producers. Here, essential amino (EA) and polyunsaturated fatty (PUFA) acids are of particular importance due to their nutritional value to higher trophic levels. In order to determine the interactive effects of CO2 and temperature on the nutritional quality of a primary producer, we analyzed the relative PUFA and EA composition of the diatom Cylindrotheca fusiformis cultured under a factorial matrix of 2 temperatures (14 and 19°C) and 3 partial pressures of CO2 (180, 380, 750 μatm) for 〉250 generations. Our results show a decay of ∼3% and ∼6% in PUFA and EA content in algae kept at a pCO2 of 750 μatm (high) compared to the 380 μatm (intermediate) CO2 treatments at 14°C. Cultures kept at 19°C displayed a ∼3% lower PUFA content under high compared to intermediate pCO2, while EA did not show differences between treatments. Algae grown at a pCO2 of 180 μatm (low) had a lower PUFA and AA content in relation to those at intermediate and high CO2 levels at 14°C, but there were no differences in EA at 19°C for any CO2 treatment. This study is the first to report adverse effects of warming and acidification on the EA of a primary producer, and corroborates previous observations of negative effects of these stressors on PUFA. Considering that only ∼20% of essential biomolecules such as PUFA (and possibly EA) are incorporated into new biomass at the next trophic level, thepotential impacts of adverse effects of ocean warming and acidification at the base of the food web may be amplified towards higher trophic levels, which rely on them as source of essential biomolecules.
    Type: Article , PeerReviewed
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  • 3
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    Inter Research
    In:  Marine Ecology Progress Series, 486 . pp. 37-46.
    Publication Date: 2018-06-25
    Description: Changing seawater chemistry towards reduced pH as a result of increasing atmospheric carbon dioxide (CO2) is affecting oceanic organisms, particularly calcifying species. Responses of non-calcifying consumers are highly variable and mainly mediated through indirect ocean acidification effects induced by changing the biochemical content of their prey, as shown within single species and simple 2-trophic level systems. However, it can be expected that indirect CO2 impacts observed at the single species level are compensated at the ecosystem level by species richness and complex trophic interactions. A dampening of CO2-effects can be further expected for coastal communities adapted to strong natural fluctuations in pCO2, typical for productive coastal habitats. Here we show that a plankton community of the Kiel Fjord was tolerant to CO2 partial pressure (pCO2) levels projected for the end of this century (〈1400 µatm), and only subtle differences were observed at the extremely high value of 4000 µatm. We found similar phyto- and microzooplankton biomass and copepod abundance and egg production across all CO2 treatment levels. Stoichiometric phytoplankton food quality was minimally different at the highest pCO2 treatment, but was far from being potentially limiting for copepods. These results are in contrast to studies that include only a single species, which observe strong indirect CO2 effects for herbivores and suggest limitations of biological responses at the level of organism to community. Although this coastal plankton community was highly tolerant to high fluctuations in pCO2, increase in hypoxia and CO2 uptake by the ocean can aggravate acidification and may lead to pH changes outside the range presently experienced by coastal organisms.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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  • 4
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    ASLO (Association for the Sciences of Limnology and Oceanography)
    In:  Limnology and Oceanography, 54 (6). pp. 2283-2297.
    Publication Date: 2017-10-24
    Description: While there is a general sense that lakes can act as sentinels of climate change, their efficacy has not been thoroughly analyzed. We identified the key response variables within a lake that act as indicators of the effects of climate change on both the lake and the catchment. These variables reflect a wide range of physical, chemical, and biological responses to climate. However, the efficacy of the different indicators is affected by regional response to climate change, characteristics of the catchment, and lake mixing regimes. Thus, particular indicators or combinations of indicators are more effective for different lake types and geographic regions. The extraction of climate signals can be further complicated by the influence of other environmental changes, such as eutrophication or acidification, and the equivalent reverse phenomena, in addition to other land-use influences. In many cases, however, confounding factors can be addressed through analytical tools such as detrending or filtering. Lakes are effective sentinels for climate change because they are sensitive to climate, respond rapidly to change, and integrate information about changes in the catchment.
    Type: Article , PeerReviewed
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  • 5
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    ASLO (Association for the Sciences of Limnology and Oceanography)
    In:  Limnology and Oceanography, 54 (6). pp. 2493-2505.
    Publication Date: 2014-01-30
    Description: Life history responses are expected to accompany climate warming, yet little is known how long-term effects of climate and environmental change affect the seasonal dynamics of planktonic organisms. We used an historical data set from Lake Washington (U.S.A.) to quantify population responses of a calanoid copepod (Leptodiaptomus ashlandi) to long-term changes in temperature and resource availability and explore potential mechanisms for the responses. Increasing water temperatures (annual mean increase of 1.5 degrees C in the upper 10-m water volume) and longer stratification periods (about 4 weeks) were observed between 1962 and 2005, coincident with a pronounced decline in Leptodiaptomus densities. However, production was maintained because of an increase in the production to biomass ratio and a life cycle shift in Leptodiaptomus from an annual to a 6-month cycle. Cross-wavelet analyses demonstrated that the annual thermal forcing of copepod recruitment observed during the first two decades of the study weakened substantially, leading to more stochastic population dynamics during the past two decades. This shift from one to two generations per year was most likely produced by a longer and warmer growing period combined with changing fluctuations in resource (phytoplankton) availability. Climate change can lead to higher-frequency voltinism in ectothermic organisms and to temporal reorganization of their population dynamics.
    Type: Article , PeerReviewed
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  • 6
    Publication Date: 2018-12-11
    Description: Our present understanding of ocean acidification (OA) impacts on marine organisms caused by rapidly rising atmospheric carbon dioxide (CO2) concentration is almost entirely limited to single species responses. OA consequences for food web interactions are, however, still unknown. Indirect OA effects can be expected for consumers by changing the nutritional quality of their prey. We used a laboratory experiment to test potential OA effects on algal fatty acid (FA) composition and resulting copepod growth. We show that elevated CO2 significantly changed the FA concentration and composition of the diatom Thalassiosira pseudonana, which constrained growth and reproduction of the copepod Acartia tonsa. A significant decline in both total FAs (28.1 to 17.4 fg cell−1) and the ratio of long-chain polyunsaturated to saturated fatty acids (PUFA:SFA) of food algae cultured under elevated (750 µatm) compared to present day (380 µatm) pCO2 was directly translated to copepods. The proportion of total essential FAs declined almost tenfold in copepods and the contribution of saturated fatty acids (SFAs) tripled at high CO2. This rapid and reversible CO2-dependent shift in FA concentration and composition caused a decrease in both copepod somatic growth and egg production from 34 to 5 eggs female−1 day−1. Because the diatom-copepod link supports some of the most productive ecosystems in the world, our study demonstrates that OA can have far-reaching consequences for ocean food webs by changing the nutritional quality of essential macromolecules in primary producers that cascade up the food web.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
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