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Povzetek: The structure and activity of prokaryotic communities were determined in marine snow and in the ambient water of the northern Adriatic Sea in different seasons (autumn, spring and summer). The seasonal variation in the composition of marine-snow-associated and ambient-water bacterial communities was assessed by T-RFLP (Terminal Restriction Fragment Length Polymorphism) on the 16S rRNA gene (16S rDNA) and 16S rRNA transcript (16S rRNA) level. On the 16S rDNA level, the bacterial community composition of the marine snow and ambient water was similar in summer and autumn, but not in spring. In contrast, on the 16S rRNA level, indicative of the active bacterial community, the marine-snow-associated bacterial community was different from that of the ambient-water, and different from the bacterial community on the 16S rDNA level, except in autumn. To phylogenetically characterize the bacterial and archaeal community composition associated with marine snow and the ambient water, clone libraries of 16S rDNA and 16S rRNA were constructed from 2 contrasting seasons. Phylogenetic profiling revealed a higher similarity among bacterial communities in summer compared to late autumn. Certain bacterial and archaeal groups were exclusively associated with summer or autumn marine snow, suggesting that marine-snow-associated prokaryotic communities are subjected to successional changes similar to ambient-water communities. Moreover, the presence of bacterial groups enriched in marine snow including Vibrionales and sulphate-reducing bacteria is consistent with niche partitioning and metabolic adaptations of the particle-associated microbiota.
Ključne besede: marine snow, free-living-bacteria, Northern Adriatic sea
Objavljeno v DiRROS: 02.08.2024; Ogledov: 14; Prenosov: 7
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Povzetek: The tetrasporophyte of the non-indigenous red alga Asparagopsis armata (the Falkenbergia stage) is considered to be established in Slovenian coastal waters. However, until 2016, it was found only in low coverage and in few localities with hard substrata. The paper reports a recent bloom of these tetrasporophytes in the mediolittoral belt of the Bay of Piran, where thalli of this red alga overgrew the articularted coralline alga Corallina officinalis. The sites affected by this large expansion of tetrasporophytes of A. armata should be regularly monitored in the future, in order to point out which environmental factors are responsible for such phenomenon, and to formulate proper conclusions on the status of this non-indigenous alga in the coastal area concerned.
Ključne besede: non-indigenous species, coastal waters, autburst, northern Adriatic Sea
Objavljeno v DiRROS: 01.08.2024; Ogledov: 39; Prenosov: 13
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Povzetek: On 1st December 2018 a fisherman caught a specimen of the giant tun Tonna galea (Linnaeus, 1758) in the bottom trammel net for flounders, approximately 1 Nm outside the town of Izola. The net was placed on a muddy bottom at 20 m of depth. This is the second record of T. galea in the Slovenian waters (Gulf of Trieste, northern Adriatic Sea). Another specimen (the first one) was previously reported in October 2015 in the waters off Piran. By including T. galea in the checklist of Slovenian marine malacofauna, at least 370 gastropod species were up to date recorded in the Slovenian part of the Adriatic Sea.
Ključne besede: giant tun, marine malacofauna, Gulf of Trieste, northern Adriatic Sea
Objavljeno v DiRROS: 31.07.2024; Ogledov: 48; Prenosov: 35
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Povzetek: In the Mediterranean Sea Cymodocea nodosa is considered a valid indicator of environmental changes, due to its extensive distribution, sensitivity to different pressures, and measurability of species responses to those stressors. Navigation routes are recognized among the main pressures on the status of C. nodosa meadows in the Gulf of Trieste, related to a high resuspension of sediments and, in consequence, high water turbidity and reduced light levels. The MediSkew index was applied to samples collected in the C. nodosa meadow growing near the Port of Koper, and the ecological status was evaluated. The results were compared to those obtained for the C. nodosa samples from the reference site in the Gulf of Trieste, the Strunjan Nature Reserve.
Ključne besede: MediSkew index, leaf lengths, Port of Koper, northern Adriatic Sea
Objavljeno v DiRROS: 31.07.2024; Ogledov: 43; Prenosov: 24
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Povzetek: Carbonate sediments in non-vegetated habitats on the north-east Adriatic shelf are dominated by shells of molluscs. However, the rate of carbonate molluscan production prior to the 20th century eutrophication and overfishing on this and other shelves remains unknown because: (i) monitoring of ecosystems prior to the 20th century was scarce; and (ii) ecosystem history inferred from cores is masked by condensation and mixing. Here, based on geochronological dating of four bivalve species, carbonate production during the Holocene is assessed in the Gulf of Trieste, where algal and seagrass habitats underwent a major decline during the 20th century. Assemblages of sand-dwelling Gouldia minima and opportunistic Corbula gibba are time-averaged to >1000 years and Corbula gibba shells are older by >2000 years than shells of co-occurring Gouldia minima. This age difference is driven by temporally disjunct production of two species coupled with decimetre-scale mixing. Stratigraphic unmixing shows that Corbula gibba declined in abundance during the highstand phase and increased again during the 20th century. In contrast, one of the major contributors to carbonate sands – Gouldia minima – increased in abundance during the highstand phase, but declined to almost zero abundance over the past two centuries. Gouldia minima and herbivorous gastropods associated with macroalgae or seagrasses are abundant in the top-core increments but are rarely alive. Although Gouldia minima is not limited to vegetated habitats, it is abundant in such habitats elsewhere in the Mediterranean Sea. This live–dead mismatch reflects the difference between highstand baseline communities (with soft-bottom vegetated zones and hard-bottom Arca beds) and present-day oligophotic communities with organic-loving species. Therefore, the decline in light penetration and the loss of vegetated habitats with high molluscan production traces back to the 19th century. More than 50% of the shells on the sea floor in the Gulf of Trieste reflect inactive production that was sourced by heterozoan carbonate factory in algal or seagrass habitats.
Ključne besede: bioturbation, carbonate production, mollusca, northern Adriatic Sea, taphonomy, time averaging
Objavljeno v DiRROS: 23.07.2024; Ogledov: 61; Prenosov: 35
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