SPATIAL AND TEMPORAL VARIATION IN LITTORAL-ZONE BENTHIC INVERTEBRATESFROM 3 SOUTH-CENTRAL ONTARIO LAKES

Surveys of benthic invertebrates have revealed patterns attributed to the impacts of acid deposition. Unfortunately, these patterns may be c onfounded by temporal variation that will affect follow-up studies of the recovery of these communities. Here, we assess spatial and tempora l variation in time-limited, kick-and-sweep collections of littoral-zo ne benthos. Spatial variation comprised five sites representing the pr edominant nearshore substrates in each of three lakes. Temporal variat ion spanned a different scale in each lake with five sites sampled: (i ) twice on the same day, (ii) once a week for 3 weeks, and (iii) four times through the ice-free season. Variation was quantified using a mo del II analysis of variance. Spatial differences predominated in same- day samples (60.4% of the variation on average) and those collected ov er a 3-week period (46.1%). In contrast, samples collected over the ic e-free season revealed that spatial and temporal factors accounted for 9.4 and 25.6% of the variation. We conclude that our collections of l ittoral macrobenthos are highly repeatable if sampling is restricted t o short periods (e.g., 3 weeks). Surveys spanning longer periods may i ncorporate considerable temporal variation from seasonal changes in ab undance.