engleski

Monitoring of benthic habitats in shallow infralittoral of the National Park Kornati(Croatia)

Benthic communities are dynamic systems that respond constantly due to natural and anthropogenic impacts. Permanent monitoring programs are necessary for effective management of protected and threatened marine areas. The aim of this study was to use the original method of underwater geo-referenced videography to record the baseline condition of the benthic habitats in the shallow infralittoral of Kornati National Park, with special focus on Posidonia oceanica seagrass meadows. The substrate type, depth, density and taxa of aquatic vegetation and presence of ecological elements was recorded for every second of the video. We recorded 52 geo-referenced video-transects, with the total length of 28.4 km, of which Posidonia covered 14.8 km. The median depth of the highest density Posidonia was 12 m, density decreased with increasing depth, and we saw no Posidonia deeper than 32 m. The density of algal cover also decreased with depth, while the settlements of sparse Cymodocea and loose algae occurred at lower depths than where algae or Posidonia dominated. The median depth of the highest density algae and sparse Cymodocea settlements was about 9 m. The median depth of pen shell (Pinna nobilis) was 11 m. Our results confirmed that underwater geo-referenced videography can provide high-quality data (spatial and visual), which can be quickly collected and quantitatively analyzed, and these data can be collected entirely non-destructively. Since the data are geo-referenced it is possible to return to the same location at any time and re-record the same transect, and quantify any change in habitat with known statistical precision. Its low cost, rapid and non-destructive execution and statistical rigor makes this method highly suitable for monitoring benthic habitats.

monitoring; infralittoral; underwater geo-referenced videography; Adriatic; Croatia

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