Invasion done: history and explanation of the spread of the river nerite (Theodoxus fluviatilis L., 1758) along the artificial shoreline of Lake Balaton

Résumé fourni par la source

Lakes and their catchment area, which are of great interest for tourism, are now heavily modified and subject to urbanisation and other forms of shoreline development.All these processes can contribute to the appearance and spread of non-native species.Although Theodoxus fluviatilis (L., 1758) appeared in Lake Balaton (Hungary) in 2013, we have limited information on the spread of the species as well as on the ecological preference of the species in the lake.To address these shortcomings, we surveyed the spatial distribution of the species, examined how land-use pressures along with the geographical location of sampling sites influence the abundance of T. fluviatilis, and investigated the depth preference of the species along the shoreline of the lake.We found that the species has successfully conquered the artificial rocky shoreline of Lake Balaton eight years after its first appearance.Our results indicate that the geographic location of the sampling sites had a significant role since the abundance of T. fluviatilis decreased from southwest to northeast, corresponds to the nutrient gradient in Lake Balaton.This result suggests that, beyond local factors like artificial rip-rap habitats, lake-level factors also significantly influence the distribution of the species.We observed that T. fluviatilis favours 70-80 cm water depth, which might be due to the decreasing rate of wave-induced disturbances along the depth gradient and the available food for the species.We argue that the occurrence and the spread of the species in the lake can be explained by the existence of shoreline modification and by the water management practice that maintains high water levels.These assumptions are consistent with literature evidence stating that the high water level can influence key environmental variables such as windinduced turbidity, sediment resuspension, and underwater light conditions, which may affect the distribution of aquatic organisms in the littoral zone.

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