Research Document - 2010/054

The Basin Head Irish Moss (Chondrus crispus) Population Abundance and Distribution 1980 to 2008

By G. Sharp, R. Semple, H. Vandermeulen, M. Wilson, C. LaRocque, and S. Nebel

Abstract

The Basin Head strain of Chondrus crispus has unique characteristics including frond morphology, reproductive stage and growing habit distinctive from the open coast populations. These fronds are held in place by an association with Blue Mussel (Mytilus edulis) forming clumps of fronds and contiguous patches of clumps. The population is concentrated in a 500 m section of the northern arm of the Basin Head lagoon. There were early reports of this population in the 1960’s. However, it was not until 1980 that two assessments defined a bed of 160,000 m² , equivalent to 127 to154 t of standing crop. Twenty years later the area was estimated at 60,000 m² and a biomass of 46.8t. A significant reduction in cover was observed in 2003 and this decline continued until less than 1 t of the biomass was present in 2008. Transfers of C. cripsus to other estuaries in PEI enhanced the growth rate compared to control fronds in Basin Head. This suggested that growing conditions in Basin Head were sub optimal for the species. The eutrophication of the basin over the past 30 years and decreasing water quality were suggested as potential reasons for the decline of the C. crispus population. Extensive blooms of Ulva spp. develop in the early summer and in the late summer breakdown of tissues leads to areas of anoxia and poor water quality. It is recommended that grow out experiments be conducted in the lagoon to test this hypothesis for the decline of C. crispus biomass.

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