engleski

Habitats heterogeneity of the littoral zone in the determination of snail assemblages in the shallow eutrophic lake

Glavni cilj ovog rada bio je utvrditi utjecaj makrofitskih sastojina na raznolikost, brojnost, uzrasnu (veličinsku) i trofičku strukturu puževa u rukavcu rijeke Sutle. Rukavac se sastoji od dva bazena, jednog veće prozirnosti s dobro razvijenim submerznim makrofitima kompleksnog habitusa, dok je drugi bazen bez makrofita i veće mutnoće. Istraživanje je provedeno tijekom dviju vegetacijskih sezona. Tijekom istraživanja determinirano je 10 vrsta puževa, od kojih su četiri vrste zajedničke za oba bazena. U litoralnoj zoni bazena bez makrofitskih sastojina puževi su zabilježeni sporadično, s vrlo malom brojnošću. Veća brojnost jedinki utvrđena je u bazenu s razvijenim makrofitima, a vrsta koja je dominirala tijekom istraživanog razdoblja je Gyraulus laevis. Analiza uzrasne strukture puževa ukazuje da su u kasno proljeće i ljeto dominirale juvenilne jedinke, a udio odraslih jedinki bio je značajniji tek u jesenskom razdoblju. Od funkcionalnih hranidbenih skupina puževa najveći udio imali su strugači koji su izvore hrane nalazili u obraštaju (perifitonu), a zatim usitnjivači, koji su se hranili sitnim dijelovima makrofita. Rezultati ovog rada ukazuju na važnost raznolikosti mikrostaništa u sastojinama submerznih makrofita koja su puževima predstavljala raznolik i bogat izvor hrane, sigurno mjesto za mrijest te sklonište od predatora. The main objective of this study was to determine the effect of macrophyte stands on diversity, abundance, size and trophic structure of snails in the backwater of the Sutla River. The backwater is made up of two pools, one with transparent and well-developed submerged macrophytes with complex habitus, while the other pool is without submersed macrophytes and turbid. The study was conducted during two vegetation seasons. During the study 10 species of snails were determined, of which four species were common to both pools. In the littoral zone of the pool without macrophytes snails have been reported sporadically and in very low abundance. Increased abundance of snails was found in the pool with macrophyte stands, while during the study period species Gyraulus laevis species was dominated. Analyses of age structure of snails indicate that in late spring and summer dominated juveniles, and the share of adults was significant in the fall. From functional feeding groups of snails largest share had scrapers that are food sources found in a periphyton, then grazers, feeding on small parts of macrophytes. Results of this study indicate the importance of the microhabitats diversity in the stands of submerged macrophytes, which represent to snails a diverse and rich source of food, safe place for spawning and shelter from predators.

mollucs; macrophytes; abundance; growth structure; functional feeding guilds

Predavanja održala Maria Špoljar