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Query: "author" (Ivajnšič Danijel) .

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1.
Evaluating seagrass meadow dynamics by integrating field-based and remote sensing techniques
Danijel Ivajnšič, Martina Orlando-Bonaca, Daša Donša, Jaša Veno Grujić, Domen Trkov, Borut Mavrič, Lovrenc Lipej, 2022, original scientific article

Abstract: Marine phanerogams are considered biological sentinels or indicators since any modification in seagrass meadow distribution and coverage signals negative changes in the marine environment. In recent decades, seagrass meadows have undergone global losses at accelerating rates, and almost one-third of their coverage has disappeared globally. This study focused on the dynamics of seagrass meadows in the northern Adriatic Sea, which is one of the most anthropogenically affected areas in the Mediterranean Sea. Seagrass distribution data and remote sensing products were utilized to identify the stable and dynamic parts of the seagrass ecosystem. Different seagrass species could not be distinguished with the Sentinel-2 (BOA) satellite image. However, results revealed a generally stable seagrass meadow (283.5 Ha) but, on the other hand, a stochastic behavior in seagrass meadow retraction (90.8 Ha) linked to local environmental processes associated with anthropogenic activities or climate change. If systemized, this proposed approach to monitoring seagrass meadow dynamics could be developed as a spatial decision support system for the entire Mediterranean basin. Such a tool could serve as a key element for decision makers in marine protected areas and would potentially support more effective conservation and management actions in these highly productive and important environments.
Keywords: Adriatic Sea, seagrass meadow, change analysis, Cimodocea nodosa, image classifiers, Sentinel-2, marine biology, hydrobiology
Published in DiRROS: 16.07.2024; Views: 15; Downloads: 4
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2.
Coastal fish fauna in the Cystoseira s.l. algal belts : experiences from the Northern Adriatic Sea
Lovrenc Lipej, Danijel Ivajnšič, Valentina Pitacco, Domen Trkov, Borut Mavrič, Martina Orlando-Bonaca, 2023, original scientific article

Abstract: Cystoseira s.l. forests are recognised as important habitats which host diverse coastal fish assemblages. Many fish species use such habitats as feeding, breeding, and nursery grounds. Since the coastal fish community depends on the availability of dense macroalgal belts, the decline of these habitats in the Mediterranean Sea also affects the density of coastal fish species. We studied the coastal fish assemblage in Cystoseira s.l. forests in three consecutive years 2019–2021 in the Gulf of Trieste (Adriatic Sea). Data on coastal fish fauna were collected by visual counts conducted by SCUBA diving. Data on algal cover and habitat types were obtained by recording with a video camera. Similarities and differences in the fish community were analysed in terms of habitat and substrate preferences. A total of 34 species were recorded in Cystoseira forests. The results of the present study show that the different algal cover and associated depth gradient have different effects on the fish assemblage in coastal waters, affecting species composition and abundance. For many species, particularly labrids and sea breams, there is a decreasing temporal trend in frequency of occurrence and density. However, fish community trends can be used as a good “proxy” to evaluate the algal belt status. Our results indicate that rapid conservation and restoration actions are needed to stem the decline of Cystoseira s.l. forests.
Keywords: Cystoseira s.l. forests, fish assemblage, fish biodiversity, habitat preference, macroalgal belt, Mediterranean Sea
Published in DiRROS: 12.07.2024; Views: 46; Downloads: 18
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3.
The coastal ichthyofauna of the Mediterranean coral reef : the case of Mljet National Park (Croatia, southern Adriatic Sea)
Lovrenc Lipej, Danijel Ivajnšič, Valentina Pitacco, Borut Mavrič, Domen Trkov, Petar Kružić, 2024, original scientific article

Abstract: The authors studied the structure of the coastal fish assemblage in a temperate coral reef within a marine protected area in order to provide a baseline information on the occurrence and temporal distribution of fish and to highlight the importance of the coral reef to ichthyofauna. The coastal fish assemblage was investigated at two sites in Veliko jezero (Mljet National Park) in the southern Adriatic Sea with a non-destructive SCUBA visual technique in the period from 2013 to 2021. Altogether, 38 fish taxa were recorded on the right bank (coral reef) and 36 species on the left bank. The presence of the coral reef at a depth range between 9 m to 12 m is the main factor differentiating the fish fauna in these two areas, which are otherwise governed by the same environmental factors. At the coral reef a decrease in fish diversity was discovered with a steady regression from 2013 to 2021.
Keywords: fish fauna, spatial heterogeneity, Mediterranean coral reef, Cladocora caespitosa, marine protected area, Veliko jezero
Published in DiRROS: 10.05.2024; Views: 183; Downloads: 251
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