engleski

The impact of invasive amphipod Dikerogammarus villosus on leaf litter decomposition in the Drava river

Freshwater amphipods have important role in decomposition of coarse particulate organic matter and often represent key species in aquatic food webs and organic matter cycling. The aim of this study was to test the differences in leaf litter decomposition rates between two pairs of sites, with and without invasive amphipod Dikerogammarus villosus. The experiment was conducted in October 2021 at two locations on the Drava River in Croatia ; at each location at upstream site only native species were present, while at downstream site D. villosus co-occurred with native species. At each site 30 leaf bags (15 fine leaf bags for control and 15 coarse leaf bags) were placed into water containing 2.5 g of willow leaves dried for 16 hours at 60°C and sampled three times (after 3, 7 and 11 days). Leaves were conditioning in stream water for one week before the experiment. Leaf decomposition rates for coarse leaf bags were 1.1- 6.9 times lower at sites where D. villous was present, but significant difference between sites was established only at one location. The correlation between dry mass of native amphipods and leaf litter mass loss was significant at both sites (rs=0.44 and 0.65), while negative correlations were established for dry mass of D. villosus (rs=-0.55 and -0.33). These results indicate that invasion of D. villosus changes important functional role which native gammarids have in decomposition of leaf litter in the Drava River.

benthic community ; native ; invasive Amphipoda ; shredder ; Drava River

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