Trends in the Nearshore and Profundal Benthic Invertebrate Communities of Lake Simcoe: 2005-2016

Session: 56. - Science for a Healthy Lake Simcoe

Brian Ginn, Lake Simcoe Region Conservation Authority, [email protected]
Raymond Bolton, Lake Simcoe Conservation, [email protected]
Kaitlin Cocks, Lake Simcoe Region Conservation Authority, [email protected]

Abstract

Starting in 2005, and continuing annually since 2008, we have undertaken surveys of the benthic community of Lake Simcoe. Benthos of the nearshore (2-20 m water depth) and profundal (>20 m depth) zones were dominated by chironomids, oligochaetes, and invasive dreissenid mussels. The most significant species change recorded during the period of study has been the decline of the zebra mussel population ~2010, and their replacement by quagga mussels. While zebra mussels were mostly restricted to water depths <20 m, likely due to deeper substrates being soft mud and silt, quagga mussels have expanded into the profundal zone since 2012 and altered the composition and density of the deepwater benthos. Since 2005, the benthic community has seen declines in filter feeding taxa (e.g. sphaeriid bivalves and some oligochaete taxa) at sites where dreissenids are present, and a 4-5X increase in the density of deposit feeder taxa. Current investigations of benthic community changes, particularly in the profundal zone, are targeting changes to energy and nutrient cycling (e.g. benthification of resources by dreissenids) and possible impacts to higher trophic levels.

1. Keyword
benthos

2. Keyword
mussels

3. Keyword
Lake Simcoe