Spremembe pokritosti dna z morskimi travniki v Semedelskem zalivu v obdobju 2009–2015

Abstract

Prispevek predstavlja rezultate vecletnega preucevanja razsirjenosti in spreminjanja povrsine morskih travnikov in zaplat morskih trav v Semedelskem zalivu. V preteklosti je preucevanje morskih travnikov zahtevalo uporabo zamudnih metod in dalo le okvirne podatke, uporaba sodobnih nacinov zajemanja podatkov in GIS-orodij pa omogoca obsežnejse raziskave in natancnejse podatke. S sonarskim snemanjem in fotografiranjem iz zraka smo pridobili podatke, ki smo jih s pomocjo geografskih informacijskih sistemov analizirali in ugotovili, da se povrsina dna v Semedelskem zalivu pokritega z morskimi travniki povecuje, kar kaže na izboljsanje kakovostnega stanja obalnega morja, zlasti na manjso motnost vode in manjsi dotok hranil s kopnega. Obseg vecjih morskih travnikov se je v obdobju 2009–2015 povecal za 8,6 ha ter danes pokrivajo že 45,6 % dna. Morski travniki so se v najvecji meri povecali s pomikom spodnje meje v globlje dele zaliva in z razrascanjem posameznih zaplat v izlivnem obmocju Badasevice. The paper presents the results of a several-year long research of the range and changes in the extent of marine meadows and patches of seagrass in the Semedela Bay (Slovenia). In the past, such investigation required the use of time-consuming methods and resulted only in raw data, whereas the use of modern methods of collecting data and the GIS tools enable more extensive research and give more accurate data. Sonar mapping and air photography provided information which we analysed by means of Geographic Information Systems. We have established that the extent of the marine meadows in the Semedela Bay has been increasing, which indicates that the quality of the coastal seawater has improved; particularly its cloudiness has decreased and so has the inflow of nutrient matter from the land. The extent of larger marine meadows increased in the 2009–2015 period by 8.6 ha, so that nowadays they cover as much as 45.6 % of the seabed. They mostly have been enlarged by moving the lower border into deeper parts of the Semedela Bay and by growing individual patches in the mouth area of the river Badasevica.