Malacofauna of the littoral benthos of a saline lake in southern Mendoza, Argentina

Abstract

The Bañado Carilauquen (BC) is part of the "Laguna Llancanelo" Watershed, an area of international relevance for biodiversity conservation that holds interest for oil production. Records on the biological attributes of the system's waters are scarce, particularly regarding benthic macroinvertebrate assemblages. The goal was to study the diversity of malacofauna in the BC and the relationship between its distribution patterns and water physicochemical parameters. Biological samplings and records of environmental parameters were carried out between summer of 2000 and spring of 2001 for five reaches of the BC. Complete individuals and empty shells of each species were recorded for every sample, and height and width were measured for all shells. Conchological relationships were estimated and sizes compared. The relationship between presence and abundance of molluscs and environmental parameters was explored using CCA. Five gastropod species were identified: Heleobia parchappii, H.hatcheri, Chilina mendozana, Lymnaea viator and Biomphalaria peregrina. A growing gradient of conductivity and hardness was detected between the headwaters (relatively soft waters) and the outlet-lake (very hard and saline waters). The distribution of molluscs is related to this gradient. Our results suggest that, except for the headwaters, the BC is hardly favourable for the development of gastropod populations. This was expressed in low species diversity, low densities, reduced sizes, fluctuating populations and high proportion of empty shells (> 80%).