94 INVERTEBRATES IN Myriophyllum spicatum L. STANDS IN LAKE SAKADAŠ, CROATIA DUBRAVKA ČERBA * , IRELLA BOGUT, JASNA VIDAKOVIĆ, GORAN PALIJAN Department of Biology, J. J. Strossmayer University, Trg Ljudevita Gaja 6, HR-31000 Osijek, Croatia; e-mail: dcerba@gmail.com, ibogut@gmail.com, javidako@inet.hr, gpalijan@ffos.hr * Corresponding author Abstract Čerba D., Bogut I., Vidaković J., Palijan G.: Invertebrates in Myriophyllum spicatum L. stands in lake Sakadaš, Croatia. Ekológia (Bratislava), Vol. 28, No. 1, p. 94–105, 2009. The invertebrates associated with Myriophyllum spicatum L., were studied during the vegetation period in 2004, at three stations I, II and III, in lake Sakadaš within Kopački rit floodplain, Croatia. A total of twenty one taxa were recorded, with the dominance of the insect larvae representatives. Family Chironomidae had the greatest abundance and represented 67% of all recorded invertebrates, while as nematodes and oligochaetes were especially abundant at the third station. Significant dif- ferences in invertebrate abundances were recorded between months of sampling – July and August as well as July and September. Also, stations I and II showed statisticaly important differences in relation to station III, located near lake’s dam. Physicochemical data, including trophic state indices, as well as invertebrate community composition were indicative for eutrophic state of water with a tendency to hypertrophy at all stations in lake Sakadaš. Key words: submerged macrophytes, eutrophication, chironomids, nematodes, oligochaetes Introduction In relatively small and shallow lakes, the littoral flora has a very important role in produc- tivity of the lake and can regulate and dominate metabolism of the entire lake ecosystem (Wetzel, 2001). Macrophytes in shallow waters provide shelter for invertebrates from predators and disturbance (Dvořák, Best, 1982; Tessier et al., 2004). Aquatic plants with different architecture of leaves support different biomass, taxonomic composition as well as size structure of invertebrate fauna (Soszka, 1975; Hann, 1995; Cheruvelil et al., 2002). Plant surface is ideal for the colonisation of periphytic algae, which are a source of food for many of invertebrates (Dvořák, Best, 1982; Monahan, Caffrey, 1996; Zirk, Goldsborough, 1996). Due to the importance of the Kopački rit Nature Park as a large floodplain area and Ekológia (Bratislava) Vol. 28, No. 1, p. 94–105, 2009