Abstract
Although the ecosystem transforming impact of the invasive dreissenid mussels has been widely reported in short-to-mid time scale studies, little is known about the contribution of the spent shells to sediments accumulating on the lake bottom. The question whether the shell production significantly reduces the lifespan of the lake by increasing sedimentation rate is particularly interesting in those shallow lakes where the calcium supply is sufficient to maintain the high mussel biomass production permanently, and where the alkaline water does not favor shell dissolution. Lake Balaton, a large calcareous, shallow lake in Central Europe invaded by dreissenids (Dreissena polymorpha, Dreissena rostriformis bugensis), provides an ideal testing ground for this scenario. Therefore, we made calculations based on recent population abundance datasets (2000–2018), estimated the whole habitable, hard surface coastline and the muddy bottom of the pelagic area which is also gradually becoming inhabited by D. r. bugensis, using high resolution aerial photographs and analyzing seismic sections. We created four scenarios: (1) if no dreissenids are present (applying basic sedimentation rate); (2) if D. r. bugensis had not been introduced to the lake (only D. polymorpha); (3) if D. r. bugensis occupies the hard surfaces of the coastline (the current dominant situation); (4) if D. r. bugensis colonizes the entire lake bottom (a probable future model). Different sedimentation rates obtained from the literature were used to model the filling of Lake Balaton. The shell production of the new invader, D. r. bugensis can shorten the lake’s lifespan by one to two-thirds, depending on the model, and whether the mussel density currently observed at the shoreline is extended to the whole lake bottom. Attention is called to shallow calcareous lakes with low pre-invasion sedimentation rates in which the shell contribution of invasive mollusks has the potential to shorten lifespan.
Highlights
Increasing attention is being paid to shallow lakes due to their vulnerability
Samples and observations both underwater and on the beach, as well as seismic sections in the Fonyód area make clear that there are two underwater ridges of Upper Miocene outcrops along the coastline (Novák et al, 2010) which are thickly covered by D. polymorpha
Filling of the lake basin caused by dreissenid invasion at Lake Balaton In the present study, the idea of invasive dreissenid shell production contributing to sedimentation was examined
Summary
Increasing attention is being paid to shallow lakes due to their vulnerability. The natural filling process of a lake basin over a longer time scale, resulting in the termination of the lake is overlooked. Quantifying this process by attempting to model it, is of great interest in learning the fate of shallow lakes. Dreissenid species, Dreissena polymorpha (Pallas 1771, common name: zebra mussel) and Dreissena rostriformis bugensis (Andrusov, 1897, quagga mussel) originated from the Ponto-Caspian region, but have become widely distributed These invasive bivalves are in North America and Europe, where they are rapidly colonizing freshwater bodies
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