Exploring aquatic organism responses to anthropogenically influenced environmental changes through development and utilization of hydroacoustic technology

Abstract

Anthropogenic perturbations have had dramatic effects on the aquatic ecosystems. Acid deposition dramatically altered the lakes, rivers and streams in the Adirondacks. The most palpable effect was the extirpation of entire fisheries from specific lakes. Brooktrout Lake, in the south western Adirondacks is a perfect example of a lake that was completely altered by acid deposition. The lake maintained a thriving fishery through the 1960s until it began to succumb to the pressures of the acid deposition. The fishery was extirpated and this allowed a new top predator to colonize the lake, Chaoborus americanus. The combined effect of this new top predator and acid deposition selected ecosystem components completely altered the biota of the lake. With the passing of the 1990 Clean Air Act Amendment (1990) the acid deposition on the lake was decreased dramatically and consequently the lake made a dramatic chemical rebound. In 2005 fish were reintroduced to the lake. Hydroacoustic examinations of the lake tracked both the reintroduced fish population and the C. americanus. Hydroacoustic backscatter analysis documented the C. americanus; they remained in the lake concurrently with the fish and displayed diel vertical migration until they were eventually extirpated by the fish. The fish naturalized to the lake and through hydroacoustic population estimates, netting, isotopic concentration analysis and genetic testing, it was conclusively determined that the reintroduced fish were successfully reproducing in the lake, a direct result of the 1990 CAAA.

Another anthropogenic perturbation to aquatic ecosystems is the introduction of aquatic invasive species. Invasive species have been linked to ecosystem declines and species loss. Management and control of invasive species on Lake George has been conducted to help maintain the lakes ecosystem. Eurasian watermilfoil was discovered in 1986 and has been unsuccessfully managed since. A hydroacoustic rapid detection technique was developed to assess large swaths of the littoral zone for this plant to aid management efforts. Asian clam was discovered in the lake in 2010. A combined traditional and hydroacoustic survey was used to identify its extent and an experimental control effort was tested.