Eutrophication and Dreissena invasion as drivers of biodiversity: a century of change in the mollusc community of Oneida Lake.

Vadim A Karatayev,Alexander Y Karatayev,Lars G Rudstam,Lyubov E Burlakova,John F Valentine

doi:10.1371/journal.pone.0101388

Abstract

Changes in nutrient loading and invasive species are among the strongest human-driven disturbances in freshwater ecosystems, but our knowledge on how they affect the biodiversity of lakes is still limited. We conducted a detailed historical analysis of the mollusc community of Oneida Lake based on our comprehensive lakewide study in 2012 and previous surveys dating back to 1915. In the early 20th century, the lake had a high water clarity, with abundant macrophytes and benthic algae, and hosted the most diverse molluscan community in New York State, including 32 gastropod and 9 unionid species. By the 1960s, lake turbidity increased during a period of anthropogenic eutrophication, resulting in a 38% decline in species richness and a 95% reduction in abundance of native gastropods grazing on benthic algae. Following the invasion of Dreissena spp. in 1991 and subsequent increases in water clarity, native gastropod species richness expanded by 37% and abundance increased 20-fold by 2012. In contrast, filter-feeding unionids were unaffected by increased turbidity during the period of eutrophication but were extirpated by dreissenids. Through contrasting effects on turbidity, eutrophication and Dreissena spp. have likely driven the observed changes in native grazing gastropods by affecting the abundance of light-limited benthic algae. Given the high species richness and ecological importance of benthic grazers, monitoring and managing turbidity is important in preserving molluscan diversity.

Highlights

Freshwater ecosystems occupy less than 1% of the Earth’s surface, yet contain,10% of all described species [1]
Perhaps the strongest and most widespread anthropogenic press disturbances have been eutrophication [9] and invasive species, the spread of zebra (Dreissena polymorpha) and quagga (D. rostriformis bugensis) mussels, which act as powerful ecosystem engineers [10,11,12,13]
Current state of the molluscan community During our study, we found a total of 31 molluscan species, most of which (84%) were native to the region (Table 1, S1)

Summary

Introduction

Freshwater ecosystems occupy less than 1% of the Earth’s surface, yet contain ,10% of all described species [1]. 90% of the world’s population lives near fresh water, making these unique ecosystems hotspots of both biotic diversity and human activity [2]. As the global population continues to grow, biotic and abiotic processes in these ecosystems are being impacted, and in some cases profoundly altered, by anthropogenic activities [3,4]. Our attempt to abate the precipitous decline in global biodiversity places a premium on identifying the extent to which human-mediated disturbances affect the species richness of these systems. Disturbances can perturb systems as discrete events (‘‘pulses’’), or as continuous processes (‘‘presses’’), with the latter more likely to produce long-term ecosystem changes [8]. Perhaps the strongest and most widespread anthropogenic press disturbances have been eutrophication [9] and invasive species, the spread of zebra (Dreissena polymorpha) and quagga (D. rostriformis bugensis) mussels, which act as powerful ecosystem engineers [10,11,12,13]

Methods

Results

Conclusion