1,721,016 research outputs found
KOSMOS Bergen 2015 mesocosm study: C. harengus survival
No full textTo evaluate the influence of ocean acidification on predatory plankton, e.g. Hydrozoa and fish larvae as well as their interaction in complex natural communities, we deployed eight pelagic mesocosms for 53 days (Mai to July) in Raunefjord, Norway, and enclosed 60 m³ of local seawater containing a natural plankton community under post-bloom conditions. Four mesocosms were manipulated to simulate extreme pCO2 levels of 2069 µatm while the other four served as untreated controls. To investigate the interaction between Hydrozoa and fish larvae influenced by OA ee studied OA-induced changes at the top of the food web by following ≈2000 larvae of Atlantic herring (Clupea harengus) hatched inside each mesocosm during the first week of the experiment, and a Hydrozoa population that had already established inside the mesocosms. Organisms of both taxa inside and outside the mesocosms were measured over the course of the experiment in regular intervals. The data stems from 55µm and 500µm Apstein net hauls, subsequent microscopic analyses as well as carbon to nitrogen measurements. Under OA, we detected 20% higher abundance of hydromedusae staged jellyfish, but 25% lower biomass. At the same time, survival rates of Atlantic herring larvae were higher under OA (control pCO2: 0.1%, high pCO2: 1.7%) in the final phase of the study
KOSMOS 2014 mesocosm study: mesozooplankton abundances
No full textUsing a mesocosm approach, we investigated ocean acidification effects on a subtropical zooplankton community during oligotrophic, bloom, and post-bloom phases under a range of different pCO2 levels (from ~400 to ~1480 µatm). To do that, we simulated an upwelling event by adding 650 m-depth nutrient-rich water to the mesocosms, which initiated a phytoplankton bloom. The most abundant mesozooplankters were calanoid copepods, which did not respond to CO2 treatments during the oligotrophic phase of the experiment but were found in higher abundance under medium- and high-pCO2 conditions towards the end of the experiment, most likely as a response to increased phyto- and microzooplankton standing stocks. The second most abundant mesozooplankton taxon were appendicularians, which did not show a response to the different pCO2 treatments. Overall, CO2 effects on zooplankton seem to be primarily transmitted through significant CO2 effects on phytoplankton and therefore indirect pathways
KOSMOS Bergen 2015 mesocosm study: C. harengus biomass
No full textTo evaluate the influence of ocean acidification on predatory plankton, e.g. Hydrozoa and fish larvae as well as their interaction in complex natural communities, we deployed eight pelagic mesocosms for 53 days (Mai to July) in Raunefjord, Norway, and enclosed 60 m³ of local seawater containing a natural plankton community under post-bloom conditions. Four mesocosms were manipulated to simulate extreme pCO2 levels of 2069 µatm while the other four served as untreated controls. To investigate the interaction between Hydrozoa and fish larvae influenced by OA ee studied OA-induced changes at the top of the food web by following ≈2000 larvae of Atlantic herring (Clupea harengus) hatched inside each mesocosm during the first week of the experiment, and a Hydrozoa population that had already established inside the mesocosms. Organisms of both taxa inside and outside the mesocosms were measured over the course of the experiment in regular intervals. The data stems from 55µm and 500µm Apstein net hauls, subsequent microscopic analyses as well as carbon to nitrogen measurements. Under OA, we detected 20% higher abundance of hydromedusae staged jellyfish, but 25% lower biomass. At the same time, survival rates of Atlantic herring larvae were higher under OA (control pCO2: 0.1%, high pCO2: 1.7%) in the final phase of the study
KOSMOS Bergen 2015 mesocosm study: Hydrozoa, C. harengus, and Copepoda abundances and biomasses
No full textTo evaluate the influence of ocean acidification on predatory plankton, e.g. Hydrozoa and fish larvae as well as their interaction in complex natural communities, we deployed eight pelagic mesocosms for 53 days (Mai to July) in Raunefjord, Norway, and enclosed 60 m³ of local seawater containing a natural plankton community under post-bloom conditions. Four mesocosms were manipulated to simulate extreme pCO2 levels of 2069 µatm while the other four served as untreated controls. To investigate the interaction between Hydrozoa and fish larvae influenced by OA ee studied OA-induced changes at the top of the food web by following ≈2000 larvae of Atlantic herring (Clupea harengus) hatched inside each mesocosm during the first week of the experiment, and a Hydrozoa population that had already established inside the mesocosms. Organisms of both taxa inside and outside the mesocosms were measured over the course of the experiment in regular intervals. The data stems from 55µm and 500µm Apstein net hauls, subsequent microscopic analyses as well as carbon to nitrogen measurements. Under OA, we detected 20% higher abundance of hydromedusae staged jellyfish, but 25% lower biomass. At the same time, survival rates of Atlantic herring larvae were higher under OA (control pCO2: 0.1%, high pCO2: 1.7%) in the final phase of the study
KOSMOS mesocosm experiment Gran Canaria 2019 on testing the effect of nutrient composition (Si:N) during artificial upwelling: mesozooplankton carbon and nitrogen content and stable isotope δ15N
No full textMesozooplankton (mesoZP) per capita mass, elemental composition and stable N isotopes during the mesocosm experiment in the Canary Islands in autumn 2019. Depth-integrated (0-2.5m) water samples were taken over the course of 33 days. Metazoan zooplankton were split into three size fractions (55-200, 200-500 and >500 µm), picked into tin cups in groups and C, N and δ15N measured in an element analyser coupled to a mass spectrometer. Particulate organic matter (>0.7µm) was also measured for a comparison of C/N between the bottom of the food web and mesoZP grazers. The upwelling treatment started on day 6. Methodological details in Goldenberg et al. (doi:10.3389/fmars.2022.1015188) and Goldenberg et al. (under review)
KOSMOS mesocosm experiment Gran Canaria 2019 on testing the effect of nutrient composition (Si:N) during artificial upwelling: mesozooplankton trophic level and fish biomass and feeding
No full textMesozooplankton trophic position (via copepod δ15N) to approximate food web length as well as fish production (via biomass increase) and feeding rate (via stomach content) during the mesocosm experiment in the Canary Islands in autumn 2019. Copepods >200µm were sampled depth-integrated (0-2.5m) on day 13. At this time, copepods represented the top of the food web as fish were not yet present. Individuals were picked in groups into tin capsules and δ15N measured in a mass spectrometer. Particulate organic matter(>0.7µm) δ15N was also measured to calculate an autotroph baseline. The difference between copepod and autotroph δ15N was used as trophic level proxy. A small pelagic fish (silverside, Atherina presbyter) was introduced to the mesocosms on day 15. On day 18, for a subset of fish, stomachs content was assessed to estimate feeding success. On day 21, all fish were sampled for biomass and abundance. The upwelling treatment started on day 6. Methodological details in Goldenberg et al. (doi:10.3389/fmars.2022.1015188) and Goldenberg et al. (under review)
Seawater carbonate chemistry and Hydrozoa, Copepoda abundances and biomasses, and Clupea harengus biomass, survival, condition
No full textAnthropogenic CO2 emissions cause a drop in seawater pH and shift the inorganic carbon speciation. Collectively, the term ocean acidification (OA) summarizes these changes. Few studies have examined OA effects on predatory plankton, e.g. Hydrozoa and fish larvae as well as their interaction in complex natural communities. Because Hydrozoa can seriously compete with and prey on other higher-level predators such as fish, changes in their abundances may have significant consequences for marine food webs and ecosystem services. To investigate the interaction between Hydrozoa and fish larvae influenced by OA, we enclosed a natural plankton community in Raunefjord, Norway, for 53 days in eight ≈ 58 m³ pelagic mesocosms. CO2 levels in four mesocosms were increased to ≈ 2000 µatm pCO2, whereas the other four served as untreated controls. We studied OA-induced changes at the top of the food web by following ≈2000 larvae of Atlantic herring (Clupea harengus) hatched inside each mesocosm during the first week of the experiment, and a Hydrozoa population that had already established inside the mesocosms. Under OA, we detected 20% higher abundance of hydromedusae staged jellyfish, but 25% lower biomass. At the same time, survival rates of Atlantic herring larvae were higher under OA (control pCO2: 0.1%, high pCO2: 1.7%) in the final phase of the study. These results indicate that a decrease in predation pressure shortly after hatch likely shaped higher herring larvae survival, when hydromedusae abundance was lower in the OA treatment compared to control conditions. We conclude that indirect food-web mediated OA effects drove the observed changes in the Hydrozoa – fish relationship, based on significant changes in the phyto-, micro-, and mesoplankton community under high pCO2. Ultimately, the observed immediate consequences of these changes for fish larvae survival and the balance of the Hydrozoa – fish larvae predator – prey relationship has important implications for the functioning of oceanic food webs
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Marine Zooplankton Community Responses to Anthropogenic Influences
No full textContinued anthropogenic carbon dioxide (CO2) emissions lead to a persistent intensification of current levels of ocean acidification (OA) and have already had measurable impacts on life in the world’s oceans. Even if greenhouse gas emissions, including those of CO2, immediately ceased, a deliberate anthropogenic removal of CO2 from the atmosphere via so-called ‘negative emission technologies’ (NETs) is inevitable in order to reach the 2015 Paris Agreement goal of maximum 2°C global warming. Little is known, however, about possible side-effects of particularly ocean based NETs and potential interdependencies with ongoing climate change, which could affect plankton communities, marine ecosystems, and ecosystem services like fisheries. In the present thesis, the response of pelagic ecosystems was investigated under the influence of the environmental stressor OA and one of the ocean-based NETs that is under consideration, artificial upwelling. In this NET nutrient rich deep-water is admixed into nutrient depleted surface waters in order to enhance productivity and sequester carbon via the biological carbon pump. My work focused on the responses of plankton community composition, trophic level interactions, and productivity of the impacted zooplankton community. All of which are regulating factors that are important for the overall production of organic matter in an ecosystem. In a first step to assess these factors, I evaluated in a large scale mesocosm experiment, how the overall function and structure of a natural plankton community is affected by xtreme OA conditions. The experiment revealed pronounced positive and negative treatment effects on the species composition, abundance and biomass of various species within the plankton community in the mesocosms, emerging shortly after the CO2 manipulation. These OA effects were visible in all trophic levels of the planktonic food web as well as the elemental stoichiometry of organic matter. The results imply that a variety of indirect and direct OA effects led to an increase in secondary consumer biomass and enhanced top-down control in the food web, yet with unknown consequences for the productivity of the ecosystem. Intrigued by the clear effects of OA on higher trophic levels (fish larvae and hydrozoans) in the aforementioned mesocosm study, a more detailed analysis was carried out in a separate study. Here, I focused on the drivers and implications of the observed changes on the top predators in the enclosed plankton community. The findings of this study indicate that an observed decrease in Hydrozoa predation pressure and higher fish larvae survival at the top of the food chain were indirectly mediated by OA affecting lower trophic levels (phyto-, micro-, mesoplankton) as well as the predator - prey relationship between fish larvae and hydrozoans. The immediate consequences these indirect OA effects had on the top predators could entail extensive alterations also for ecosystem services. In a final step, I assessed the possible application of artificial upwelling for enhancing productivity and the efficiency of carbon transfer in an oligotrophic plankton community. A large scale mesocosm experiment simulating different upwelling modes and intensities was conducted. The results revealed an increase in primary and secondary production as well as the carbon transfer efficiency in the food web. The corresponding effect size of this increase was closely linked to temporal frequency and intensity of upwelling as well as the species and size composition of the zooplankton/ copepod community and its access to food in different qualities. Altogether, this dissertation revealed two distinct findings on the stressor and application of potential NET of artificial upwelling. Firstly, intensifying OA under a business-as-usual scenario could lead not only to a pronounced restructuring of zooplankton populations, but also entire plankton communities, including substantial changes in the predator-prey coupling of higher trophic levels, e.g. Hydrozoa and fish larvae. On the other hand, the application of artificial upwelling caused distinct changes in the productivity of the affected zooplankton community, which, under certain circumstances, supports the potential of this technique to create efficient food webs with considerable biomass output. In conclusion, these findings make clear that more focus has to be put on ocean-based climate change solutions like artificial upwelling in order to counteract direct effects of future environmental stressors to plankton communities
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