Lake Ontario zooplankton in 2003 and 2008: Community changes and vertical redistribution

Aquatic Ecosystem Health & Management
By: , and 



Lake-wide zooplankton surveys are critical for documenting and understanding food web responses to ecosystem change. Surveys in 2003 and 2008 during the binational intensive field year in Lake Ontario found that offshore epilimnetic crustacean zooplankton declined by a factor of 12 (density) and factor of 5 (biomass) in the summer with smaller declines in the fall. These declines coincided with an increase in abundance of Bythotrephes and are likely the result of direct predation by, or behavioral responses to this invasive invertebrate predator. Whole water column zooplankton density also declined from 2003 to 2008 in the summer and fall (factor of 4), but biomass only declined in the fall (factor of 2). The decline in biomass was less than the decline in density because the average size of individual zooplankton increased. This was due to changes in the zooplankton community composition from a cyclopoid/bosminid dominated community in 2003 to a calanoid dominated community in 2008. The increase in calanoid copepods was primarily due to the larger species Limnocalanus macrurus and Leptodiaptomus sicilis. These cold water species were found in and below the thermocline associated with a deep chlorophyll layer. In 2008, most of the zooplankton biomass resided in or below the thermocline during the day. Increased importance of copepods in deeper, colder water may favor Cisco and Rainbow Smelt over Alewife because these species are better adapted to cold temperatures than Alewife.

Study Area

Publication type Article
Publication Subtype Journal Article
Title Lake Ontario zooplankton in 2003 and 2008: Community changes and vertical redistribution
Series title Aquatic Ecosystem Health & Management
DOI 10.1080/14634988.2014.965121
Volume 18
Issue 1
Year Published 2014
Language English
Publisher Taylor & Francis
Contributing office(s) Great Lakes Science Center
Description 20 p.
First page 43
Last page 62
Country Canada, United States
Other Geospatial Lake Ontario
Online Only (Y/N) N
Additional Online Files (Y/N) N
Google Analytic Metrics Metrics page
Additional publication details