1. Structural and functional responses of harpacticoid copepods to anoxia in the Northern Adriatic: an experimental approachMarleen Roelofs, Marleen De Troch, Bettina Riedel, Mateja Grego, 2013, original scientific article Abstract: Combined in situ and laboratory studies were conducted to document the effects of anoxia on the structure and functioning of meiobenthic communities, with special focus on harpacticoid copepods. In a first step, anoxia was created artificially by means of an underwater chamber at 24 m depth in the Northern Adriatic, Gulf of Trieste (Mediterranean). Nematodes were found as the most abundant taxon, followed by harpacticoid copepods. While nematode densities were not affected by treatment (anoxia/normoxia) or sediment depth, these factors had a significant impact on copepod abundances. Harpacticoid copepod family diversity, in contrast, was not affected by anoxic conditions, only by depth. Ectinosomatidae and Cletodidae were most abundant in both normoxic and anoxic samples.
The functional response of harpacticoid copepods to anoxia was studied in a laboratory tracer experiment by adding 13C pre-labelled diatoms to sediment cores in order to test (1) if there is a difference in food uptake by copepods under normoxic and anoxic conditions and (2) whether initial (normoxia) feeding of harpacticoid copepods on diatoms results in a better survival of copepods in subsequent anoxic conditions. Independent of the addition of diatoms, there was a higher survival rate in normoxia than anoxia. The supply of additional food did not result in a higher survival rate of copepods in anoxia, which might be explained by the presence of a nutritionally better food source and/or a lack of starvation before adding the diatoms. However, there was a reduced grazing pressure by copepods on diatoms in anoxic conditions. This resulted in a modified fatty acid composition of the sediment. We concluded that anoxia not only impacts the survival of consumers (direct effect) but also of primary producers (indirect effect), with important implications for the recovery phase.
Keywords: morje, plankton, kopepodi, živalski plankton, trofični status, morski plankton, harpaktikoidi, anoksije
Published in DiRROS: 02.08.2024; Views: 70; Downloads: 118
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2. CellTracker Green labelling vs. Rose Bengal staining: CTG wins by points in distinguishing living from dead anoxia-impacted copepods and nematodsMateja Grego, Michael Stachowitsch, Marleen De Troch, Bettina Riedel, 2013, original scientific article Abstract: Hypoxia and anoxia have become a key threat to shallow coastal seas. Much is known about their impact on macrofauna, less on meiofauna. In an attempt to shed more light on the latter group, in particular from a process-oriented view, we experimentally induced short-term anoxia (1 week) in the northern Adriatic Sea (Mediterranean) and examined the two most abundant meiofauna taxa – harpacticoid copepods and nematodes. Both taxa also represent different ends of the tolerance spectrum, with copepods being the most sensitive and nematodes among the most tolerant. We compared two methods: CellTracker Green (CTG) – new labelling approach for meiofauna – with the traditional rose bengal (RB) staining method. CTG binds to active enzymes and therefore colours live organisms only. The two methods show considerable differences in the number of living and dead individuals of both meiofauna taxa. Generally, RB will stain dead but not yet decomposed copepods and nematodes equally as it does live ones. Specifically, RB significantly overestimated the number of living copepods in all sediment layers in anoxic samples, but not in any normoxic samples. In contrast, for nematodes, the methods did not show such a clear difference between anoxia and normoxia. RB overestimated the number of living nematodes in the top sediment layer of normoxic samples, which implies an overestimation of the overall live nematofauna. For monitoring and biodiversity studies, the RB method might be sufficient, but for more precise quantification of community degradation, especially after an oxygen depletion event, CTG labelling is a better tool. Moreover, it clearly highlights the surviving species within the copepod or nematode community. As already accepted for foraminiferal research, we demonstrate that the CTG labelling is also valid for other meiofauna groups.
Keywords: morje, plankton, kopepodi, živalski plankton, trofični status, morski plankton, CTG, CellTracker Green
Published in DiRROS: 02.08.2024; Views: 86; Downloads: 89
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3. Temperature dependence of planktonic metabolism in the subtropical North Atlantic OceanL.S. Garcia-Corral, E. Barber, A. Regaudie-de_Gioux, S. Sal, J.M. Holding, S. Agusti, N. Navarro, P. Serret, Patricija Mozetič, Carlos M. Duarte, 2014, original scientific article Abstract: The temperature dependence of planktonic metabolism in the subtropical North Atlantic Ocean was assessed on the basis of measurements of gross primary production (GPP), community respiration (CR) and net community production (NCP), as well as experimental assessments of the response of CR to temperature manipulations. Metabolic rates were measured at 68 stations along three consecutive longitudinal transects completed during the Malaspina 2010 Expedition, in three different seasons. Temperature gradients were observed in depth and at basin and seasonal scale. The results showed seasonal variability in the metabolic rates, the highest rates being observed during the spring transect. The overall mean integrated GPP / CR ratio was 1.39 ± 0.27 decreasing from winter to summer, and the NCP for the subtropical North Atlantic Ocean during the cruises exhibits net autotrophy (NCP > 0) in about two-thirds (66%) of the total sampled communities. Also, we reported the activation energies describing the temperature dependence of planktonic community metabolism, which was generally higher for CR than for GPP in the subtropical North Atlantic Ocean, as the metabolic theory of ecology predicts. Furthermore, we made a comparison of activation energies describing the responses to in situ temperature in the field (EaCR = 1.64 ± 0.36 eV) and those derived experimentally by temperature manipulations (EaCR = 1.45 ± 0.6 eV), which showed great consistency.
Keywords: morje, plankton, fitoplankton, klorofil, trofični status, anoksije
Published in DiRROS: 01.08.2024; Views: 91; Downloads: 113
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4. A MSFD complementary approach for the assessment of pressures, knowledge and data gaps in Southern European Seas: The PERSEUS experienceAlenka Malej, Alessandro Crise, H. Kaberi, J. Ruiz, 2015, original scientific article Abstract: PERSEUS project aims to identify the most relevant pressures exerted on the ecosystems of the Southern European Seas (SES), highlighting knowledge and data gaps that endanger the achievement of SES Good Environmental Status (GES) as mandated by the Marine Strategy Framework Directive (MSFD). A complementary approach has been adopted, by a meta-analysis of existing literature on pressure/impact/knowledge gaps summarized in tables related to the MSFD descriptors, discriminating open waters from coastal areas. A comparative assessment of the Initial Assessments (IAs) for five SES countries has been also independently performed. The comparison between meta-analysis results and IAs shows similarities for coastal areas only. Major knowledge gaps have been detected for the biodiversity, marine food web, marine litter and underwater noise descriptors. The meta-analysis also allowed the identification of additional research themes targeting research topics that are requested to the achievement of GES
Keywords: morje, plankton, PERSEUS, MSFD, kvaliteta morskega okolja, evropske direktive, okoljski indikatorji, Marine Strategy Framework Directive, Southern European Seas, Good Environmental status, PERSEUS project, Initial assessment
Published in DiRROS: 26.07.2024; Views: 126; Downloads: 94
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5. Biodiversity patterns of cyanobacterial oligotypes in lakes and rivers : results of a large-scale metabarcoding survey in the Alpine regionNico Salmaso, Serena Bernabei, Adriano Boscaini, Camilla Capelli, Leonardo Cerasino, Isabelle Domaizon, Tina Eleršek, Claudia Greco, Aleksandra Krivograd-Klemenčič, Paolo Tomassetti, Rainer Kurmayer, 2023, original scientific article Abstract: In this work, we characterised the cyanobacterial communities in the plankton and littoral biofilm of 38 lakes and in the biofilm of 21 rivers in the Alps and surrounding subalpine regions by 16S rRNA gene metabarcoding. We found little overlap in the distribution of amplicon sequence variants (ASVs) between the three habitats and between water bodies. The differences were caused by environmental filtering acting on the selection of the most abundant ASVs and a high contribution of rare oligotypes. The differentiation of community and genotype composition from specific water bodies was explained to a significant extent by environmental variables and morphometry. The taxonomic consistency of ASVs classified under the same genus name was assessed by phylogenetic analyses performed on three representative dominant genera, namely Cyanobium, Tychonema and Planktothrix. The analyses revealed eco-evolutionary adaptations in lakes and rivers, including some evidence for a polyphyletic nature. Monitoring individual genotypes in relation to environmental conditions will be useful to define the ecological amplitude of these taxa. However, the persistence or ephemeral nature of some of the rarest and most unusual ASVs has remained unknown.
Keywords: plankton, littoral, bioflm, European Alps, phylogenetic analysis, toxigenic cyanobacteria
Published in DiRROS: 15.07.2024; Views: 143; Downloads: 115
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