Jellyfish-Associated Microbiome in the Marine Environment: Exploring Its Biotechnological Potential.

Despite accumulating evidence of the importance of the jellyfish-associated microbiome to jellyfish, its potential relevance to blue biotechnology has only recently been recognized. In this review, we emphasize the biotechnological potential of host⁻microorganism systems and focus on gelatinous zooplankton as a host for the microbiome with biotechnological potential. The basic characteristics of jellyfish-associated microbial communities, the mechanisms underlying the jellyfish-microbe relationship, and the role/function of the jellyfish-associated microbiome and its biotechnological potential are reviewed. It appears that the jellyfish-associated microbiome is discrete from the microbial community in the ambient seawater, exhibiting a certain degree of specialization with some preferences for specific jellyfish taxa and for specific jellyfish populations, life stages, and body parts. In addition, different sampling approaches and methodologies to study the phylogenetic diversity of the jellyfish-associated microbiome are described and discussed. Finally, some general conclusions are drawn from the existing literature and future research directions are highlighted on the jellyfish-associated microbiome.

Recurrent jellyfish blooms are a consequence of global oscillations.

A perceived recent increase in global jellyfish abundance has been portrayed as a symptom of degraded oceans. This perception is based primarily on a few case studies and anecdotal evidence, but a formal analysis of global temporal trends in jellyfish populations has been missing. Here, we analyze all available long-term datasets on changes in jellyfish abundance across multiple coastal stations, using linear and logistic mixed models and effect-size analysis to show that there is no robust evidence for a global increase in jellyfish. Although there has been a small linear increase in jellyfish since the 1970s, this trend was unsubstantiated by effect-size analysis that showed no difference in the proportion of increasing vs. decreasing jellyfish populations over all time periods examined. Rather, the strongest nonrandom trend indicated jellyfish populations undergo larger, worldwide oscillations with an approximate 20-y periodicity, including a rising phase during the 1990s that contributed to the perception of a global increase in jellyfish abundance. Sustained monitoring is required over the next decade to elucidate with statistical confidence whether the weak increasing linear trend in jellyfish after 1970 is an actual shift in the baseline or part of an oscillation. Irrespective of the nature of increase, given the potential damage posed by jellyfish blooms to fisheries, tourism, and other human industries, our findings foretell recurrent phases of rise and fall in jellyfish populations that society should be prepared to face.

Chemical composition and egg production capacity throughout bloom development of ctenophore Mnemiopsis leidyi in the northern Adriatic Sea.

High abundances of gelatinous zooplankton (GZ) can significantly impact marine ecosystem by acting as both sink and source of organic matter (OM) and nutrients. The decay of GZ bloom can introduce significant amount of OM to the ocean interior, with its variability influenced by GZ life traits and environmental factors, impacting microbial communities vital to marine biogeochemical cycles. The invasive ctenophores Mnemiopsis leidyi has formed massive blooms in the northern Adriatic Sea since 2016. However, the variability in the chemical composition and egg production of blooming populations, as well as the role of environmental factors in governing this variability, remains largely unknown. Our analysis of biometry, chemical composition, and fecundity of M. leidyi sampled in the Gulf of Trieste in 2021 revealed stable carbon and nitrogen content throughout bloom development, with no significant correlation with seawater temperature, salinity, oxygen, and chlorophyll a concentration. Although the studied population exhibited homogeneity in terms of biometry and chemical composition, the number of produced eggs varied substantially, showing no clear correlation with environmental variables and being somewhat lower than previously reported for the study area and other Mediterranean areas. We observed a positive correlation between the wet weight of individuals and the percentage of hatched eggs, as well as a significant positive correlation between the percentage of hatched eggs and ambient seawater temperature. Additionally, we noted that the speed of hatching decreased with decreasing seawater temperature in autumn, corresponding to the end of M. leidyi bloom.

Mass occurrence of the ctenophore Bolinopsis vitrea (L. Agassiz, 1860) in the nearshore southern Adriatic Sea (Kotor Bay, Montenegro).

The ctenophore Bolinopsis vitrea has been rarely observed in the Mediterranean Sea. A bloom of B. vitrea is here reported for the first time in the southern Adriatic Sea in the spring and summer of 2009, together with its effect on the plankton of Kotor Bay. Ctenophores were found below 5 m depth only. Results of the investigation indicate that mass occurrence of B. vitrea could have a great impact on the Kotor Bay ecosystem. Their predation on copepods would reduce grazing pressure on phytoplankton, favouring an uncommon bloom of the latter. It is evident that B. vitrea are capable of altering rapidly the composition and biomass of coastal plankton communities when present in large masses. This first evidence of such events for this species may indicate changes in the functioning of marine ecosystems of the southern Adriatic.

"Kisanje" severnega Jadrana.

The present knowledge of the carbonate system in the northern Adriatic is described in this short overview. Its buffer capacity is rather high, due to riverine input of carbonates dissolved from Alpine and Karstic watersheds, and the waters should have a higher resilience to acidification. In the shallow eutrophic areas, the combined effect of rising atmospheric CO2, warming and river-induced anthropogenic CO2 with the associated decrease in buffer capacity could act to acidification process. Significant effect on calcifying organisms is expected in the future.

Lack of genetic structure in the jellyfish Pelagia noctiluca (Cnidaria: Scyphozoa: Semaeostomeae) across European seas.

The genetic structure of the holopelagic scyphozoan Pelagia noctiluca was inferred based on the study of 144 adult medusae. The areas of study were five geographic regions in two European seas (Eastern Atlantic and Mediterranean Sea). A 655-bp sequence of mitochondrial cytochrome c oxidase subunit I (COI), and a 645-bp sequence of two nuclear internal transcribed spacers (ITS1 and ITS2) were analyzed. The protein coding COI gene showed a higher level of divergence than the combined nuclear ITS fragment (haplotype diversity 0.962 vs. 0.723, nucleotide diversity 1.16% vs. 0.31%). Phylogeographic analysis on COI gene revealed two clades, the larger consisting of specimens from all sampling sites, and the smaller mostly formed of specimens from the Mediterranean Sea. Haplotype diversity was very high throughout the sampled area, and within sample diversity was higher than diversity among geographical regions. No strongly supported genetically or geographically distinct groups of P. noctiluca were found. The results - long distance dispersal, insignificant F(ST) values, lack of isolation by distance - pointed toward an admixture among Mediterranean and East Atlantic populations.

Bacteria associated with moon jellyfish during bloom and post-bloom periods in the Gulf of Trieste (northern Adriatic).

Jellyfish are a prominent component of the plankton community. They frequently form conspicuous blooms which may interfere with different human enterprises. Among the aspects that remain understudied are jellyfish associations with microorganisms having potentially important implications for organic matter cycling. To the best of our knowledge, this study is the first to investigate the bacterial community associated with live moon jellyfish (Aurelia solida, Scyohozoa) in the Adriatic Sea. Using 16S rRNA clone libraries and culture-based methods, we have analyzed the bacterial community composition of different body parts: the exumbrella surface, oral arms, and gastric cavity, and investigated possible differences in medusa-associated bacterial community structure at the time of the jellyfish population peak, and during the senescent phase at the end of bloom. Microbiota associated with moon jellyfish was different from ambient seawater bacterial assemblage and varied between different body parts. Betaproteobacteria (Burkholderia, Cupriavidus and Achromobacter) dominated community in the gastral cavity of medusa, while Alphaproteobacteria (Phaeobacter, Ruegeria) and Gammaproteobacteria (Stenotrophomonas, Alteromonas, Pseudoalteromonas and Vibrio) prevailed on 'outer' body parts. Bacterial community structure changed during senescent phase, at the end of the jellyfish bloom, showing an increased abundance of Gammaproteobacteria, exclusively Vibrio. The results of cultured bacterial isolates showed the dominance of Gammaproeteobacteria, especially Vibrio and Pseudoalteromonas in all body parts. Our results suggest that jellyfish associated bacterial community might have an important role for the host, and that anthropogenic pollution in the Gulf of Trieste might affect their community structure.

Comparative analysis of the ecosystems in the northern Adriatic Sea and the Inland Sea of Japan: Can anthropogenic pressures disclose jellyfish outbreaks?

A prominent increase in the moon jellyfish (genus Aurelia) populations has been observed since 1980 in two semi-enclosed temperate seas: the northern Adriatic Sea and the Inland Sea of Japan. Therefore, we reviewed long-term environmental and biotic data from the two Long-Term Ecological Research (LTER) sites, along with the increase in the moon jellyfish occurrence to elucidate how these coastal seas shifted to the jellyfish-dominated ecosystems. The principal component analysis of atmospheric data revealed a simultaneous occurrence of similar climatic changes in the early 1980s; thereafter, air temperature increased steadily and precipitation decreased but became more extreme. Accordingly, the average seawater temperature from March to October, a period of polyps' asexual reproduction i.e. budding, increased, potentially leading to an increase in the reproductive rates of local polyp populations. Conspicuous eutrophication occurred due to the rise of anthropogenic activities in both areas from the 1960s onwards. This coincided with an increase of the stock size of forage fishes, such as anchovy and sardine, but not the population size of the jellyfish. However, by the end of the 1980s, when the eutrophication lessened due to the regulations of nutrients loads from the land, the productive fishing grounds of both systems turned into a state that may be described as 'jellyfish-permeated,' as manifested by a drastic decrease in fish landings and a prominent increase in the intensity and frequency of medusa blooms. A steady increase in artificial marine structures that provide substrate for newly settled polyps might further contribute to the enhancement of jellyfish population size. Elevated fishing pressure and/or predation by jellyfish on ichthyoplankton and zooplankton might jeopardize the recruitment of anchovy, so that the anchovy catch has never recovered fully. These semi-enclosed seas may represent many temperate coastal waters with increased anthropogenic stressors, which have degraded the ecosystem from fish-dominated to jellyfish-dominated.

Reflection of hydrocarbon pollution on hepatic EROD activity in the black goby (Gobius niger).

Hepatic ethoxyresorufin-O-deethylase (EROD) activity was measured in black gobies (Gobius niger) collected from seven sampling sites along the Slovenian coast during spawning and non-spawning periods. Sediments from the same sites were tested for their toxicity and for total polycyclic aromatic hydrocarbon (PAH) content. EROD activity was significantly higher during the non-spawning period in winter than during the spawning period in spring and generally correlated well with increased total PAH content in sediments and with sediment toxicity. An 11-fold increase of EROD activity was induced 48h after injecting 10µgg(-1) weight of benzo(a)pyrene into black gobies. On the basis of these results and of its ecological characteristics, the black goby is proposed as a suitable candidate for future biomonitoring programmes.

Scyphomedusae of the Mediterranean: state of the art and future perspectives.

Scyphomedusae (Phylum Cnidaria, Class Scyphozoa) are perceived as a nuisance due to their sudden outbreaks that negatively affect human activities (particularly tourism and fisheries) mainly because of their stings. A brief review of the history of scyphozoan blooms in the Mediterranean and updated information available after 2010 point to an increase in scyphozoan outbreaks. Whilst the negative effects on public health, aquaculture, coastal industrial activities and fisheries operations are undeniable, the effects on the ecosystem are not well defined. We focus on the trophic interactions between scyphomedusae and fish, highlighting that the negative effects of scyphomedusae on fish stocks exerted through direct predation on early life stages of fish and competition for plankton are at present speculative. In favor of a positive effect of scyphomedusae on fish populations, the reports of predation upon scyphozoans are increasing, which suggests that predators may benefit from the availability of scyphozoans by shifting their diet toward jelly prey. Additionally, scyphomedusae may provide nursery habitats to early life stages of ecologically and economically important forage fishes and other organisms which shelter underneath their bells. Together with these ecosystem services, compounds extracted from scyphozoan tissues and venoms are having a variety of biomedical applications and are likely to contribute to treat a growing number of diseases, including cancer. Our analysis highlights that a re-evaluation of the balance between "positive" and "negative" effects of scyphomedusae on the ecosystem and human activities is needed and provides indications on potential directions for future studies.

Jellyfish modulate bacterial dynamic and community structure.

Jellyfish blooms have increased in coastal areas around the world and the outbreaks have become longer and more frequent over the past few decades. The Mediterranean Sea is among the heavily affected regions and the common bloom-forming taxa are scyphozoans Aurelia aurita s.l., Pelagia noctiluca, and Rhizostoma pulmo. Jellyfish have few natural predators, therefore their carcasses at the termination of a bloom represent an organic-rich substrate that supports rapid bacterial growth, and may have a large impact on the surrounding environment. The focus of this study was to explore whether jellyfish substrate have an impact on bacterial community phylotype selection. We conducted in situ jellyfish-enrichment experiment with three different jellyfish species. Bacterial dynamic together with nutrients were monitored to assess decaying jellyfish-bacteria dynamics. Our results show that jellyfish biomass is characterized by protein rich organic matter, which is highly bioavailable to 'jellyfish-associated' and 'free-living' bacteria, and triggers rapid shifts in bacterial population dynamics and composition. Based on 16S rRNA clone libraries and denaturing gradient gel electrophoresis (DGGE) analysis, we observed a rapid shift in community composition from unculturable Alphaproteobacteria to culturable species of Gammaproteobacteria and Flavobacteria. The results of sequence analyses of bacterial isolates and of total bacterial community determined by culture independent genetic analysis showed the dominance of the Pseudoalteromonadaceae and the Vibrionaceae families. Elevated levels of dissolved proteins, dissolved organic and inorganic nutrient release, bacterial abundance and carbon production as well as ammonium concentrations characterized the degradation process. The biochemical composition of jellyfish species may influence changes in the amount of accumulated dissolved organic and inorganic nutrients. Our results can contribute insights into possible changes in bacterial population dynamics and nutrient pathways following jellyfish blooms which have important implications for ecology of coastal waters.

The effects of eluent mixing on TLS detection in gradient elution HPLC.

The effects of changing solvent composition on the LOD of TLS detection in gradient elution HPLC have been studied from the perspective of thermo-optical properties of the solvent. Hyphenated gradient high-performance liquid chromatography (HPLC)-thermal lens spectrometry (TLS), was used to separate and detect 13 carotenoid compounds and two chlorophylls. Utilization of mixing coils into the system reduces the inhomogeneities during eluent changes and therefore enables the application of thermal lens detection in the gradient HPLC method. For gradient chromatographic conditions in which the thermo-optical properties and related enhancement factor change as much as 50% over 10 min, the LODs for the TLS detector were enhanced by as much as three times in comparison with UV-Vis detection. For the isocratic part of the chromatogram, up to a tenfold improvement of LODs was achieved with TLS detection.