080121-08MN006-Sabina Hackett River Project Proposal ... - NIRB

Description of the Existing EnvironmentTaxonomic compositionMost stream periphyton communities were heavily dominated by diatoms, which comprised ~90% of the periphyton cells. Sunken Lakes Outflow and Reference Lake A outflow did,however, have significant numbers of other chrysophyta, which made up approximately a thirdof their algal abundances.6.2.5.3 Lake ZooplanktonZooplankton, the heterotrophic component of aquatic plankton, are an important link in theaquatic food web; being consumers of phytoplankton and prey to many fish species.Zooplankton samples were collected from 27 lakes in the Hackett River study area in August,2007, including two reference lakes.AbundanceWithin the study area zooplankton abundances averaged ~ 1,300 organisms/m 3 , with lows of ~70 organisms/m 3 at Cleaver Lake, to highs of ~ 2,500 organisms/m 3 in the Boot Basin lakes BigToe, Hungrat and Dog. Although zooplankton abundances were highest in Boot Basin lakes, ingeneral, zooplankton abundance varied equally within and between watersheds.Taxonomic CompositionIn general, lake zooplankton communities were heavily dominated by copepods, althoughPlomia rotifers were also common. Cladocera tended to be scarce to non-existent in most lakes.Saddle Lake, Anne and Camp lakes had noticeably atypical zooplankton communitycompositions in comparison to other lakes in the study area. Saddle Lake zooplanktoncommunities were predominantly Flosculariaceae rotifers, with few copepods or other rotifera.Anne, and to a lesser extent Camp Lake, were almost exclusively composed of cyclopoidcopepods, a common taxon in the study area, but typically lower in abundance than othercopepods.Arctic Fairy shrimp (Polyartemiella hazeni), large brachiopods that typically inhabit ephemeralhabitats in the absence of fish, were found in three lakes in the study area; Bat Lake, AffleckLake, and Saddle Lake. Bat Lake and Affleck Lake were two of the few lakes in the study arealacking fish. Burbot were found in Saddle Lake, but their small size and low density may meanpredation pressure is low enough to allow P. hazeni to persist.6.2.5.4 Lake Benthic InvertebratesBenthic macroinvertebrates (benthos) are organisms greater than ½ a millimetre in size, lacking aback-bone, that inhabit lake and stream bottoms. Being in close contact with the sediments ofthese habitats as well as feeding on algae, bacteria, and detritus within these systems makebenthos very responsive to environmental changes. In addition to their direct contact withpossible contaminants, benthos are generally less motile than fish, providing a better indicator oflocal conditions. In addition to their use as indicator species, benthic organisms are a veryimportant food source for fish, particularly in streams, making their abundances an importanthabitat quality variable.January 2008 Hackett River Project – Project Proposal Sabina Silver CorporationReport Version B.1 6–5 Rescan Environmental Services Ltd. (Proj. #833-2)