Search the repository

A+ | A- | | SLO | ENG

Abstract: We present a dataset of zooplankton biomass spanning more than four decades (1974–2019). The dry mass of zooplankton ranged from below 10 to almost 100 mg m-3, was highest in 1989–2002 and declined thereafter. The interannual variability of zooplankton dry mass in the period 1993–2018 was compared with the regional atmospheric index WeMOi, chlorophyll a and frequency of jellyfish blooms. Increased dry mass values were associated with a positive phase of the regional atmospheric index WeMOi, higher chlorophyll a and a lower frequency of jellyfish blooms.
Keywords: net zooplankton, dry mass, time series, chlorophyll a, jellyfish blooms
Published in DiRROS: 24.06.2026; Views: 149; Downloads: 115
Full text (1,73 MB)
This document has many files! More...

Abstract: Jellyfish are increasingly recognized as a significant contributor to marine organic matter (OM) on a global scale, with implications for ecosystem dynamics. While the role of jellyfish detritus in microbial nutrient cycling has been explored, the contribution of OM released by live jellyfish—primarily as mucus (hereinafter referred to as mucusassociated OM, or MAOM)—remains understudied. This study investigates the release of organic and inorganic nutrients through MAOM from live jellyfish and their effects on ambient microbial communities in the northern Adriatic Sea using a series of leaching and short-term microcosm experiments. Our results show that per gram of MAOM dry weight from the jellyfish Aurelia spp, approximatively 2 µmol of phosphate, 4 µmol of dissolved inorganic nitrogen, 18 µmol dissolved organic nitrogen, 134 µmol of dissolved organic carbon and 15 µmol of dissolved free amino acids can be released in the ambient seawater in 24 h. Almost half of the OM is released as dissolved OM (DOM), of which a substantial part is low molecular weight (<1 kDa) molecules. During the first 20 h, the DOM fraction of MAOM was rapidly consumed by the ambient microbial community without a corresponding increase in biomass, likely due to nitrogen limitation. In the subsequent 22 h, microbial growth accelerated to 0.19 ± 0.03 h−1 until phosphate became limiting, leading to a sharp decline in microbial production. Our metagenomics analysis revealed that the MAOM-degrading microbial community, dominated by Gammaproteobacteria opportunistic copiotrophs, exhibited increased functional capacity for nutrient assimilation and OM degradation, particularly in the transport and metabolism of amino acids (particularly glycine and taurine) and phosphorus. These traits mirror those found in detritus-degrading microbial communities, suggesting that jellyfish blooms promote the emergence of specialized microbial consortia with shared metabolic capabilities. Taken together, our findings highlight that live jellyfish, through the release of OM, play an active and previously underappreciated role in shaping ambient microbial community dynamics and nutrient fluxes in marine systems affected by jellyfish blooms.
Keywords: jellyfish, bacteria, biogeochemistry, metagenome
Published in DiRROS: 02.03.2026; Views: 716; Downloads: 217
Full text (1,31 MB)
This document has many files! More...

Keywords: research data, software, jellyfish, Mediterranean sea
Published in DiRROS: 27.10.2025; Views: 819; Downloads: 655
Full text (97,18 MB)
This document has many files! More...

Abstract: Although geographically well apart, there are interesting similarities between the ecosystems of the Sea of Marmara and the Adriatic Sea. In this study, following an evaluation of the ecological problems as well as oceanography, productivity, plankton biomass of these seas, macro-jellyfish ecology of the two ecosystems were discussed comparatively. The Sea of Marmara and the Adriatic Sea are among the areas where increases in jellyfish and mucilage events have been observed in recent decades. Environmental problems such as global warming, oxygen depletion, eutrophication, overfishing, intense maritime traffic, and habitat destruction are causing opportunistic and alien species to increase in both abundance and number of species. As biodiversity declines due to habitat destruction, so does the ecosystem’s means and ability to combat the invasion of alien species in both ecosystems. Accordingly, disruption of lower food chains can put pressure on the entire ecosystem and affect socio-ecological prospects. The number of species of Scyphozoa and Ctenophora was found to be higher in the Adraitic Sea compared to the Sea of Marmara. Mass occurrences with a clear seasonal pattern and related to the geographical location were observed for Aurelia aurita, Rhizostoma pulmo, Chrysaora hysoscella and non-native Mnemiopsis leidyi in the Marmara Sea. However, although A. aurita and R. pulmo show widespread blooms according to the seasons and regions in the Adriatic Sea, C. hysoscella and M. leidyi produced blooms limited to a few areas. Negative and positive interactions of macrojelyfishes with human were also considered. Semi-enclosed seas such as the Sea of Marmara and the Adriatic Sea are representative of many temperate coastal waters where climate change and anthropogenic stressors are increasing, and the ecosystem has changed from a fish-dominated to a jellyfish-dominated ecosystem.
Keywords: jellyfish, eutrophication, diversity, introduce, fisheries
Published in DiRROS: 07.05.2025; Views: 1045; Downloads: 766
Full text (3,51 MB)
This document has many files! More...

Abstract: The analysis of historical data sets and the results obtained from field studies about the pressures exerted on coastal ecosystems in 18 sites of the Mediterranean and the Black Sea showed that : Inputs form Po and Danube rivers showed a high interannual variability. After an increase of eutrophication over the 70-80s, a decrease of nutrients inputs, especially of phosphate, was recorded since 1990. Positive impacts are seen on phytoplancton communities. In the vicinity of most coastal big cities the policy measures taken in order to reduce polluted water discharges show their effectiveness although some local issues still exist. Chemical contaminants levels decrease rapidly when the distance increase from point sources. However a large amount of coastal inputs is exported offshore. Attention should be paid to the fate and the impact of new emerging pollutants. At the basin scale, contaminant concentrations in biota show very different patterns depending on substances. For some substances, the biogeochemical background and the environmental conditions play a important role in the contamination of marine organisms. There is globally no evidence of neither degradation nor clear trends regarding seagrass meadows. The status of seagrass habitats is correlated to water quality. It can be concluded that human pressures have not affected seagrass meadows in a irreversible way. Seagrass habitats can recover (slowly) when pressures decrease. The rate of new introductions of Non Indigenous Species has been increasing at all coastal study areas after 2000. An increase of the Lessepsian species migration is seen, in link with climate change The analysis of 18 years of data about demersal fish communities showed a geographic variability in functional group (FG) biomass trends. Nearly half of the studied Mediterranean areas shows an increase of FG biomass. Changes respond mainly to nutrient inputs trends and to a lesser extent fishing pressure. Marine litter is increasing pressure on marine ecosystems. The majority of items were made of plastic often exceeding the global average of 75%. Some harmful effects on fauna are documented (birds, turtles…) but impact is poorly known. The lack of standardized methods for underwater noise measurements make difficult to assess the level of the pressure and the impact on marine ecosystems.
Keywords: sea, water directive, marine strategy framework directive, population dynamics, Gulf of Trieste, jellyfish, PERSEUS, environmental parameters
Published in DiRROS: 16.09.2024; Views: 1404; Downloads: 1256
Full text (5,69 MB)
This document has many files! More...