Breakwaters as habitat for sessile intertidal biota in the Southern Gulf of St. Lawrence
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Date
2013
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University of New Brunswick
Abstract
Increasing human populations are causing rocky breakwaters to become common
features along coastlines. However, knowledge is scarce about the role of breakwaters as
intertidal habitat. This study is the first to investigate the assemblage ecology of habitat
found on rocky breakwaters compared to natural rocky intertidal areas in the North
Atlantic coast of North America so that the potential effects of artificial rocky structures
can be understood. Percent coverage of macro-algae and macro-invertebrates were
quantified on breakwaters near Arisaig, in the Southern Gulf of St. Lawrence (sGSL) to
investigate possible temporal confounds in the main study, from June-August 2010. No
significant differences were seen over the months for richness and abundance data, and
June differed from the July and August for community composition. Then, percent
coverage of sessile biota was quantified at exposed and sheltered areas on breakwaters
and natural rocky shores along 430 km of the sGSL. Richness and abundance in sheltered
areas of breakwaters were both less than in sheltered areas of natural rocky areas.
Breakwaters had significantly different community composition compared to natural
rocky shores and between wave exposed and sheltered areas. Semibalanus balanoides
were more abundant on natural rocky shores than breakwaters and were found in higher
abundance at exposed areas than sheltered areas. Ulva intestinalis had higher abundances
on breakwaters than natural rocky shorelines and U. intestinalis, Fucus spp. and
Ascophyllum spp. had higher abundances in sheltered areas than exposed areas of
breakwaters. This study showed that biotic communities on breakwaters are substantially
different than the surrounding natural rocky shores throughout the sGSL.