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  • 1
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    Higher temperature, increased CO2, and changing nutrient ratios alter the carbon metabolism and induce oxidative stress in a cosmopolitan diatom (2023)
    Wiley
    In:  EPIC3Limnology and Oceanography, Wiley, ISSN: 0024-3590
    Details
    Publikationsdatum: 2023-12-11
    Beschreibung: Phytoplankton are responsible for about 90% of the oceanic primary production, largely supporting marine food webs, and actively contributing to the biogeochemical cycling of carbon. Yet, increasing temperature and pCO2, along with higher dissolved nitrogen: phosphorus ratios in coastal waters are likely to impact phytoplankton physiology, especially in terms of photosynthetic rate, respiration, and dissolved organic carbon (DOC) production. Here, we conducted a full-factorial experiment to identify the individual and combined effects of temperature, pCO2, and N : P ratio on the antioxidant capacity and carbon metabolism of the diatom Phaeodactylum tricornutum. Our results demonstrate that, among these three drivers, temperature is the most influential factor on the physiology of this species, with warming causing oxidative stress and lower activity of antioxidant enzymes. Furthermore, the photosynthetic rate was higher under warmer conditions and higher pCO2, and, together with a lower dark respiration rate and higher DOC exudation, generated cells with lower carbon content. An enhanced oceanic CO2 uptake and an overall stimulated microbial loop benefiting from higher DOC exudation are potential longer-term consequences of rising temperatures, elevated pCO2 as well as shifted dissolved N : P ratios.
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , isiRev
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  • 2
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    Cascading, interactive, and indirect effects of climate change on aquatic communities, habitats, and ecosystems (2023)
    Wiley
    In:  EPIC3Limnology and Oceanography, Wiley, 68(S1), pp. s1-s7, ISSN: 0024-3590
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    Publikationsdatum: 2023-08-09
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , isiRev
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  • 3
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    Differential effects of elevated 〈scp〉 〈i〉p〈/i〉 CO 〈sub〉2〈/sub〉 〈/scp〉 and warming on marine phytoplankton stoichiometry (2022)
    Wiley
    In:  EPIC3Limnology and Oceanography, Wiley, 67(3), pp. 598-607, ISSN: 0024-3590
    Details
    Publikationsdatum: 2022-09-15
    Beschreibung: Phytoplankton stand at the base of the marine food-web, and play a major role in global carbon cycling. Rising CO2 levels and temperatures are expected to enhance growth and alter carbon:nutrient stoichiometry of marine phytoplankton, with possible consequences for the functioning of marine food-webs and the oceanic carbon pump. To date, however, the consistency of phytoplankton stoichiometric responses remains unclear. We therefore performed a meta-analysis on data from experimental studies on stoichiometric responses of marine phytoplankton to elevated pCO2 and 3–5° warming under nutrient replete and limited conditions. Our results demonstrate that elevated pCO2 increased overall phytoplankton C:N (by 4%) and C:P (by 9%) molar ratios under nutrient replete conditions, as well as phytoplankton growth rates (by 6%). Nutrient limitation amplified the CO2 effect on C:N and C:P ratios, with increases to 27% and 17%, respectively. In contrast to elevated pCO2, warming did not consistently alter phytoplankton elemental composition. This could be attributed to species- and study-specific increases and decreases in stoichiometry in response to warming. While our observed moderate CO2-driven changes in stoichiometry are not likely to drive marked changes in food web functioning, they are in the same order of magnitude as current and projected estimations of oceanic carbon export. Therefore, our results may indicate a stoichiometric compensation mechanism for reduced oceanic carbon export due to declining primary production in the near future.
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , NonPeerReviewed
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  • 4
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    A common temperature dependence of nutritional demands in ectotherms (2022)
    Wiley
    In:  EPIC3Ecology Letters, Wiley, ISSN: 1461-023X
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    Publikationsdatum: 2023-06-21
    Beschreibung: In light of ongoing climate change, it is increasingly important to know how nutritional requirements of ectotherms are affected by changing temperatures. Here, we analyse the wide thermal response of phosphorus (P) requirements via elemental gross growth efficiencies of Carbon (C) and P, and the Threshold Elemental Ratios in different aquatic invertebrate ectotherms: the freshwater model species Daphnia magna, the marine copepod Acartia tonsa, the marine heterotrophic dinoflagellate Oxyrrhis marina, and larvae of two populations of the marine crab Carcinus maenas. We show that they all share a non-linear cubic thermal response of nutrient requirements. Phosphorus requirements decrease from low to intermediate temperatures, increase at higher temperatures and decrease again when temperature is excessive. This common thermal response of nutrient requirements is of great importance if we aim to understand or even predict how ectotherm communities will react to global warming and nutrient-driven eutrophication.
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , NonPeerReviewed
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  • 5
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    How sharp is the knife? Herbivore and carnivore sensitivity to resource stoichiometric quality (2023)
    Wiley
    In:  EPIC3Oikos, Wiley, ISSN: 0030-1299
    Details
    Publikationsdatum: 2023-06-12
    Beschreibung: While understanding feeding preferences of herbivores and carnivores is of major importance in ecology, we still know very little on the sensitivity of different functional groups to suboptimal stoichiometric resource quality. Here, we apply concepts of ecological stoichiometry to shed light on differences in the nutritional requirements of herbivores and carnivores, and to make predictions on the influence of suboptimal resource stoichiometric quality on the fitness of these different consumers to. Herbivores generally experience more variation in the quality of their resource than carnivores do, and these differences have likely shaped the extent to which coping mechanisms have evolved. Consequently, we expect 1) herbivores to maintain their stoichiometric homeostasis over a broader range of resource stoichiometry than carnivores, 2) the threshold elemental ratio (TER), i.e. the dietary carbon to nutrient ratio which maximizes fitness, of herbivores to be higher than that of carnivores, 3) a narrower and sharper knife-edge response in carnivores than herbivores and 4) asymmetric knife-edge responses indicating a higher sensitivity to the diet quality that consumers are not used to dealing with, namely nutrient limitation in carnivores and nutrient excess in herbivores. Our study poses that documenting the ranges of resource quality where consumer fitness declines in diverse organisms is a very promising avenue to increase our understanding of community composition and food web functioning.
    Repository-Name: EPIC Alfred Wegener Institut
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  • 6
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    Environmentally induced functional shifts in phytoplankton and their potential consequences for ecosystem functioning (2022)
    Wiley
    In:  EPIC3Global Change Biology, Wiley, 28(8), pp. 2804-2819, ISSN: 1354-1013
    Details
    Publikationsdatum: 2023-06-21
    Beschreibung: Phytoplanktonic organisms are particularly sensitive to environmental change, and, as they represent a direct link between abiotic and biotic compartments within the marine food web, changes in the functional structure of phytoplankton communities can result in profound impacts on ecosystem functioning. Using a trait-based approach, we examined changes in the functional structure of the southern North Sea phytoplankton over the past five decades in relation to environmental conditions. We identified a shift in functional structure between 1998 and 2004 which coincides with a pronounced increase in diatom and decrease in dinoflagellate abundances, and we provide a mechanistic explanation for this taxonomic change. Early in the 2000s, the phytoplankton functional structure shifted from slow growing, autumn blooming, mixotrophic organisms, towards earlier blooming and faster-growing microalgae. Warming and decreasing dissolved phosphorus concentrations were linked to this rapid reorganization of the functional structure. We identified a potential link between this shift and dissolved nutrient concentrations, and we hypothesise that organisms blooming early and displaying high growth rates efficiently take up nutrients which then are no longer available to late bloomers. Moreover, we identified that the above-mentioned functional change may have bottom-up consequences, through a food quality-driven negative influence on copepod abundances. Overall, our study highlights that, by altering the phytoplankton functional composition, global and regional changes may have profound long-term impacts on coastal ecosystems, impacting both food-web structure and biogeochemical cycles.
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , NonPeerReviewed
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  • 7
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    Long‐term shifts in phenology, thermal niche, population size, and their interactions in marine pelagic copepods (2024)
    Wiley
    In:  EPIC3Limnology and Oceanography, Wiley, ISSN: 0024-3590
    Details
    Publikationsdatum: 2024-02-08
    Beschreibung: Under climatic warming many species shift their seasonal timing of life cycle events (phenology) and seasonal abundance distribution, but whether they maintain the same thermal niche is still poorly understood. Here, we studied multidecadal trends in abundance and phenology of seven major copepod species across three stations (Stonehaven (SH), Helgoland Roads (HR), and Plymouth L4) on the North–West European shelf, spanning ~ 6.5° of latitude. All seven species consistently occupied colder temperatures at the northern station compared to the southerly station, but they maintained the same realized thermal niche over years. Expected phenological shifts (i.e., earlier when warmer) in some stations were obscured possibly by the long-term drop of copepod density in spring–summer, which may be due to a variation in the food/predators abundance. The ongoing spring–summer declines in abundance (~ 50%) of many North Atlantic pelagic species over the last five decades, as found in recent studies, may have also influenced the metrics of seasonal timing. To separate the seasonal timing of life events from that of seasonal abundance distribution, we used a time series of egg production rate (EPR) of Calanus helgolandicus at L4, and found that this shifted later into the summer–autumn over the last 30 yr of warming, coincident with declining spring–summer food and increasing predator abundance. Overall, direct temperature effects do appear to influence the seasonal timing of the copepods, but to explain impacts at individual stations or long-term trends in population size or phenology, understanding the changing balance of food and predators appears to be critical.
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , isiRev
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  • 8
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    Are all copepods the same? Variation in copepod stoichiometry with taxonomy, ontogeny, latitude, and habitat (2023)
    Wiley
    In:  EPIC3Ecosphere, Wiley, 14(12), ISSN: 2150-8925
    Details
    Publikationsdatum: 2024-02-08
    Beschreibung: Copepods are the most abundant metazoans on Earth, driving cycles of key elements in aquatic systems, most prominently carbon (C), nitrogen (N), and phosphorus (P). One key factor determining nutrient cycling is copepod somatic stoichiometry, which can reflect ecological strategy. We conducted a systematic review that updates the seminal work of Båmstedt (1986) by summarizing the effects of latitude, habitat, life history stage, and taxonomy on C:N, C:P, and N:P ratios of field-collected copepods. We found that differences among copepod families accounted for the greatest variation, with the Rhincalanidae and Diaptomidae being particularly C-rich, while the Calanidae were more N- and P-rich. Copepod C:N was higher in inland waters compared with animals from marine environments in both copepodites and adult females, matching the higher C content of seston in many inland freshwaters. For both copepodites and adult females, mid-latitude animals had higher C:N and C:P than high-latitude animals, which matched predictions based on the availability of nutrients or adaptation to cold environments. More data must be gathered to fill gaps in our knowledge of copepod stoichiometry, focusing particularly on younger life stages, non-calanoids, low and high latitudes, the southern hemisphere, and estuarine and some inland water habitats, including large lakes. Such information will help better parameterize models of aquatic ecosystems and improve our understanding of how copepods influence consumer-driven nutrient cycling and food web dynamics.
    Repository-Name: EPIC Alfred Wegener Institut
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  • 9
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    A multiple baseline approach for marine heatwaves (2024)
    Wiley
    In:  EPIC3Limnology and Oceanography, Wiley, ISSN: 0024-3590
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    Publikationsdatum: 2024-02-09
    Beschreibung: 〈jats:title〉Abstract〈/jats:title〉〈jats:p〉Marine heatwaves and other extreme temperature events can drive biological responses, including mass mortality. However, their effects depend on how they are experienced by biological systems (including human societies). We applied two different baselines (fixed and shifting) to a time series of North Sea water temperature to explore how slowly vs. quickly adapting systems would experience extreme temperatures. We tested if the properties of marine heatwaves and the association with atmospheric heatwaves were robust to a change in baseline. A fixed baseline produced an increase in the frequency and duration of marine heatwaves, which would be experienced as the new normal by slowly adapting systems; 7 of the 10 most severe heatwaves occurred between 1990 and 2018. The shifting baseline removed the trend in the frequency but not duration of heatwaves; the 1990s appeared as a period of change in the frequency of strong and severe heatwaves as compared to the 1980s. There were also common patterns among baselines: marine heatwaves were more frequent in late summer when temperatures peak; temperature variability was characterized by low frequency, large amplitude fluctuations (i.e., as red noise), known to drive extinction events. In addition, marine heatwaves occurred during or just after atmospheric heatwaves. Our work highlights the importance of identifying properties of marine heatwaves that are robust or contingent on a change in baseline.〈/jats:p〉
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