Phytoplankton as a biological predictor in assessment of the ecological status of karstic lakes (case study – NP Plitvice lakes)

Složeni i raznoliki krški baražni ekosustavi unatoč izuzetnom ekološkom, prirodnom, kulturnom i gospodarskom značaju, slabo su istraženi. U slatkovodnim lenitičkim područjima fitoplankton čini glavninu primarne produkcije i bazu trofičke piramide te se kao značajan pokazatelj promjena u ekosustavu koristi kao biološki indikator u procjeni ekološkog stanja (Okvirna Direktiva o vodama, ODV). Istraživanje fitoplanktonske zajednice krškog baražnog sustava Plitvičkih jezera provedeno je u razdoblju od godinu dana na dva vertikalna profila (jezero Kozjak i Prošće) s ciljem definiranja fitoplanktonske zajednice prema sličnim morfološkim i funkcionalnim značajkama i to u svrhu postizanja boljeg razumijevanja funkcioniranja ovog ekološkog sustava. Istraživanjem je određeno na koji način abiotički i biotički čimbenici utječu na taksonomski sastav fitoplanktonske zajednice te su određene strategije preživljavanja zajednice na osnovu intenziteta stresa i narušavanja u sustavu. Korištenjem različitih pristupa u opisu morfološko-funkcionalnih grupa definiran je, u skladu s naputcima ODV-a, najbolje primjenjiv pristup za opis zajednice fitoplanktona krških baražnih jezera, kao i mogućnost korištenja istog u određivanju ekološkog stanja. Despite their exceptional environmental, natural, cultural and economic significance, karstic barrage ecosystems are still poorly investigated. Phytoplankton is an important biological indicator of changes in the ecosystem and accounts for the majority of primary production in freshwater systems, therefore making it useful in assessing the ecological status of water bodies (in accordance with the Water Framework Directive, WFD). Phytoplankton community of Plitvice Lakes, a karstic barrage lake ecosystem, was investigated during a one year period on two vertical profiles (on Lakes Kozjak and Prošće) with the aim of defining the community with similar morphological and functional traits and achieving a better understanding on how the ecosystem is functioning. The research determined how abiotic and biotic factors affected the taxonomic composition of the phytoplankton community. Phytoplankton survival strategies based on the intensity of stress and distortion in the system were determinated. Using different descriptive morpho-functional classifications, the most applicable approach describing phytoplankton community of karstic barrage lakes was defined (in accordance with the WFD instructions), in order to investigate the possibility of using the same approach in determining the ecological status.