Spatial distribution of micromollusks under the impact of recreation

Abstract

Anthropogenic impacts lead to a decrease in the abundance and diversity of communities of living organisms. The rate of recovery of populations is inversely proportional to size: the smaller the size, the greater the potential for population recovery after negative impact. Therefore, under conditions of extremely high levels of anthropogenic impact, small-sized animals are a reliable source of ecosystem state. The aim of the work is to: 1) to evaluate rates of the micromollusc Vallonia pulchella (Müller, 1774) abundance in ecosystems that are subject to extremely high levels of recreational pressure; 2) to identify factors that influence the spatial patterns of soil micromollusks; and 3) to investigate the possibility of using micromollusks for the purposes of bioindication of recreational pressure. The soil sampling was performed on a regular grid with recording of local coordinates. The micromollusks were extracted from the soil samples by hand sorting. Physical properties of soil sensitive to recreational load were also measured. Micromolluscs were found to exhibit a non-linear response to recreational impact. The maximum abundance of animals is observed at a certain distance from recreational trails. This distance is specific for different species of micromollusks. Micromollusks have high population abundance even under conditions of high recreational load. The regular spatial patterns of these animals are caused by changes in the soil habitat, which are induced by recreational load. This circumstance allows to consider micromollusks as a reliable indicator of the level of recreational load.