|English: Broad Cove, Cobscook Bay State Park in Maine at low tide (Photo credit: Wikipedia)|
Century-scale Species Incidence, Rareness and Turnover in a High Diversity Northwest Atlantic Coastal Embayment
THOMAS J. TROTT
R.S. Friedman Field Station, Edmunds, ME 04628; Biology Department, Suffolk University, 41 Temple Street, Boston, MA 02114; email@example.com
Abstract The increased chance of extinction for rare species jeopardizes the resilience of high diversity coastal ecosystems where the uncommon often hold key roles which sustain ecosystem functioning. Rare species can support the most vulnerable functions of an ecosystem, occupy niches that more common species are unable to fill, and have significant disproportionate effects on higher trophic levels when lost. Therefore, detecting rare species and marine extinctions at any spatial scale is a priority. The deep (~2 centuries) zoological record of Cobscook Bay, USA, a biological hotspot in the Northwest Atlantic, provides the opportunity to assess species rareness and turnover in a high diversity coastal ecosystem. This well-studied macrotidal embayment in the lower Bay of Fundy has 874 macroinvertebrate species known from 3,767 records and an extrapolated maximum species richness of approximately 1,175 species. The chronology of its historical record of species incidence features some striking patterns. Approximately one-third of identified species have yet to be confirmed, with 88 last seen prior to 1900. Sampling effort, species ranges, endemicity and stochastic larval settlement do not adequately explain why so many species are rare. Instead, evidence of late 20th-century species turnover coincident with diversification and intensification of commercial fisheries suggests that local extinction is the primary cause for species rareness. In addition, present-day species assemblages have significantly altered taxonomic structure and trophic composition. The implications of rare species loss on the stability and function of this highly productive estuary illustrate the need for ecological conservation to protect the substantial contribution of Cobscook Bay to the biodiversity of the Gulf of Maine.