Spatial and Temporal Variability of Tidepool Hyperbenthos on a Rocky Shore in Nova-Scotia, Canada

Abstract

We examined the distribution and abundance of the hyperbenthos in tidepools on a rocky shore, near Halifax, Nova Scotia, Canada, at approximately monthly intervals between March and November 1991, and between April and June 1992. We sampled 4 pools at each of 3 intertidal heights: mid and high intertidal and splash zones. Additional samples were taken at the sea surface for comparison. Calanoid and harpacticoid copepods, cladocerans, foraminiferans, nematodes and rotifers were the most abundant groups within our samples. Significant differences in the abundance of these groups among zones were detected on only 5 out of 12 sampling dates. Total hyperbenthos, as well as calanoid and harpacticoid copepods, nematodes and rotifers, generally were more abundant in the high and/or the splash pools. The abundance of total hyperbenthos varied significantly among pools within zones from May to October 1991 and in June 1992. Significant differences in abundance among pools within zones were also detected for harpacticoid copepods and nematodes on 3 sampling dates, for calanoid copepods and rotifers on 5 sampling dates, and for cladocerans and foraminiferans on 2 sampling dates. In most cases, the significant variability in abundance among pools arose within the high intertidal or the splash zones. Over the entire sampling period, the diversity of faunal groups was lower in the splash pools, possibly as a result of harsh conditions in these pools. The few groups that survived in these high pools, such as rotifers and the calanoid copepod Eurytemora affinis, reached densities of up to 106 ind. m-3. Dominant populations may be established in particular pools by founder effects and persist due to low flushing rates. Thus, variability among pools in the high intertidal and splash zones may exceed that observed among pools in lower intertidal zones.