A descriptive analysis of recent changes in benthic communities at Evangeline Beach, Nova Scotia
LE3 .A278 2009
Gibson, Glenys D.
Bachelor of Science
The Minas Basin is a megatidal system (up to 15m tidal range) with extensive mudflats that are home to infauna such as molluscs, nematodes, crustaceans and polychaetes, these animals in turn, are important energy sources for larger animals such as shorebirds and fish. My study objective was to establish a Natural Geography of In Shore Areas (NaGISA) site in the Southern Bight of the Minas Basin as a reference point for monitoring long term change in intertidal communities, and to document the biological characteristics of this site. The first extensive survey of Minas Basin infauna, by Gratto in 1978, found that the benthos of Evangeline Beach was dominated by few species of infauna, and the majority of species found were uncommon. The question arises as to whether recent changes (30 years) in infauna distribution can be detected in the Minas Basin. I re-sampled two transects that Gratto (1978) established at Evangeline Beach, with 5 replicate samples at each of the low, mid and high intertidal zones. The 2008 samples contained a higher number of taxa than did historic (1978) samples and density was greater by an order of magnitude. Samples from the low intertidal zone contained 8000 individuals/ m2 in 1978 and >65,000 / m2 in 2008; a similar increase was found for the mid and high intertidal zones. Some individual species showed a marked change in relative abundance. For example, the spionid Pygospio elegans increased in abundance from 13% (1978) to 73% (2008) of the infauna sampled. These results suggest that the intertidal community at Evangeline Beach has changed considerably over 30 years. Historic data, however, are likely influenced by differences in sample processing effort. This NaGISA site, now established, forms an important baseline for long-term monitoring of benthic community structure in this dynamic ecosystem.
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