Macrobenthic abundance and distribution in tidal pools of a Quebec salt marsh

Abstract

The abundance and distribution of macrobenthos in tidal pools of different sizes and physical–chemical conditions were examined in a salt marsh near Isle Verte, Quebec. The underlying purpose of the study was to determine if the macrobenthic community was the same among tidal pools regardless of their location, size, or physical–chemical conditions. Three hypotheses were examined relating to concepts of stability–diversity, island biogeography, and environmental gradients: (i) that the macrobenthic community of small tidal pools contains fewer species than that of larger pools; (ii) that numbers of macrobenthic species increase with pool size; and (iii) that macrobenthic species composition in pools nearest the Estuary is different from that of high marsh pools. No consistent differences in the macrobenthic community were found between pool sizes. Pools situated closer to the St. Lawrence Estuary had a slightly different fauna than the more inland pools owing to different flooding regimes. Oligochaetes (Tubificidae), the gastropod Hydrobia minuta, and Chironomus sp. larvae were the dominant organisms of the marsh. There was a negative correlation between the abundance of chironomid larvae and interstitial water salinity, and a positive correlation between polychaete abundance and overlying water salinity. A negative correlation was also observed between the occurrence of Chironomus sp. and Culicoides sp. (Diptera) which may have been due to biotic factors. Varying interstitial salinities were found amongst regions of large pools, possibly due to floodwater transport mechanisms in the marsh.