Historical versus contemporary measures of seaweed biodiversity in the Bay of Fundy.

Anthropogenic changes in many components of the Bay of Fundy biota have recently been reported, however a detailed assessment of benthic seaweed biodiversity has not been performed since the late 1970s. Here, we summarize 7 years (2000-2006) of temporal and spatial variation in species richness, composition, and percent cover of intertidal seaweeds in the outer Bay of Fundy, New Brunswick, Canada. In doing so, we provide up-to-date baseline records using repeatable and well-documented protocols. We document the presence of 72 species of seaweeds across four sites, and demonstrate that the biota at one of our sites is indicative of a degraded assemblage: large patches of unutilized substrate, low algal richness and abundance, with assemblages composed of hardy algal species and grazing and filter feeding invertebrates. Additionally, we compare these contemporary data with historical presence-absence records compiled from herbarium collections (1954-1978) and site surveys from 1963 to 1964 and 1978. Comparisons reveal 16 species not relocated in contemporary surveys. However, conclusions of anthropogenic changes in seaweed biodiversity are difficult to assess in the absence of high quality baseline information, and seaweeds historically found but not relocated in current sampling are easily misidentified, subtidal, or rare. We discuss the nature and value of baseline data, and make suggestions for future research.