Influence of environmental variables on zooplankton development in the Danube River

Cilj ovog istraživanja bio je utvrditi utjecaj okolišnih parametara na razvoj zooplanktona tijekom različitih godišnjih doba. Uzorci su prikupljeni na rijeci Dunav mjesečnom dinamikom tijekom 2011. godine. Zabilježene su dvije vrste rašljoticalaca i tri vrste veslonožaca. Najveća brojnost planktonskih rakova zabilježena je u ljetnom (1,12 ind/L), a najmanja u jesenskom razdoblju (0,58 ind/L). Iz skupine rašljoticalaca pronađene su Bosmina longirostris (O.F. Müller, 1785) i Sida crystallina (O.F. Müller, 1776). Iz skupine veslonožaca pronađene su vrste Acanthocyclops vernalis (Fisher, 1853), Cyclops vicinus (Sars, 1863) i Thermocyclops crassus (Fisher, 1853) te razvojni stadiji nauplii i kopepoditi. Istraživanjem je utvrđeno da mjereni okolišni čimbenici imaju različit utjecaj na razvoj i strukturu planktonskih rakova ovisno o godišnjem dobu. Najveći utjecaj imali su temperatura, koncentracija dušika i električna provodljivost.The aim of this study was to investigate the influence of different environmental variables on zooplankton development during different seasons. Samples were collected monthly from the Danube River during 2011. Two cladoceran and three copepod species were recorded. The maximum abundance of crustacean zooplankton was recorded in summer (1,12 ind/L) while minimum abundance was recorded in autumn (0,58 ind/L). Among cladocerans Bosmina longirostris (O.F. Müller, 1785) and Sida crystallina (O.F. Müller, 1776) were recorded while among copepods Acanthocyclops vernalis (Fisher, 1853), Cyclops vicinus (Sars, 1863) and Thermocyclops crassus (Fisher, 1853) with juvenile copepods (nauplii and copepodites) were recorded. The present study defined that measured environmental variables have a different effect on growth and structure of crustacean zooplankton concerning different seasons. Major environmental variables influencing crustacean zooplankton were temperature, nitrogen concentration and conductivity