1. Chemical composition and egg production capacity throughout bloom development of ctenophore Mnemiopsis leidyi in the northern Adriatic SeaKevin Rečnik, Katja Klun, Lovrenc Lipej, Alenka Malej, Tinkara Tinta, 2024, original scientific article Abstract: 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.
Keywords: ctenophore, biogeochemistry, egg production capacity, invasive species, chemical composition, marine ecology
Published in DiRROS: 29.08.2024; Views: 112; Downloads: 551
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2. Annual recurrence of prokaryotic climax communities in shallow waters of the North MediterraneanMauro Celussi, Vincenzo Manna, Elisa Banchi, Viviana Fonti, Matteo Bazzaro, Vesna Flander-Putrle, Katja Klun, Martina Kralj, Neža Orel, Tinkara Tinta, 2024, original scientific article Abstract: In temperate coastal environments, wide fluctuations of biotic and abiotic factors drive microbiome dynamics. To link recurrent ecological patterns with planktonic microbial communities, we analysed a monthly-sampled 3-year time series of 16S rRNA amplicon sequencing data, alongside environmental variables, collected at two stations in the northern Adriatic Sea. Time series multivariate analyses allowed us to identify three stable, mature communities (climaxes), whose recurrence was mainly driven by changes in photoperiod and temperature. Mixotrophs (e.g., Ca. Nitrosopumilus, SUP05 clade, and Marine Group II) thrived under oligotrophic, low-light conditions, whereas copiotrophs (e.g., NS4 and NS5 clades) bloomed at higher temperatures and substrate availability. The early spring climax was characterised by a more diverse set of amplicon sequence variants, including copiotrophs associated with phytoplankton-derived organic matter degradation, and photo-auto/heterotrophic organisms (e.g., Synechococcus sp., Roseobacter clade), whose rhythmicity was linked to photoperiod lengthening. Through the identification of recurrent climax assemblages, we begin to delineate a typology of ecosystem based on microbiome composition and functionality, allowing for the intercomparison of microbial assemblages among different biomes, a still underachieved goal in the omics era.
Keywords: marine microbial ecology, coastal seas, microbial community analyses, marine biology, marine ecology
Published in DiRROS: 17.05.2024; Views: 441; Downloads: 335
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