Distribution and abundance of tintinnids in the Quoddy Region of the Bay of Fundy

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Abstract
The seasonal cycle of tintinnid species compositions, numerical abundance, and average lorica oral diameter was examined along a nearshore–offshore transect in the Quoddy Region of the Bay of Fundy. Among 27 species identified, Stenosemella nivalis was most abundant. Highest abundances of tintinnids were observed near the surface; hyaline forms dominated near the surface while agglutinated forms were predominant in subsurface waters. Maximum abundances of 1.8 × 108 and 9.0 × 106 cells/m2 were observed at near- and off-shore stations, respectively, in summer. Hyaline tintinnids were more numerous in midsummer and at the offshore site, possibly because of the necessity of a sedimentary phase in the life cycle of agglutinated forms. The seasonal decrease in the lorica oral diameter of tintinnids was paralleled by a decrease in average cell volume of phytoplankton. Annual tintinnid productivity was estimated as 250 kJ/m2 in Passamaquoddy Bay (nearshore) and total productivity from May to October was 34 kj/m2 in the lower Bay of Fundy (offshore). We conclude that tintinnid ciliates are an important trophic intermediate in the planktonic food web because of their high productivity and their ability to feed on the small, highly productive phytoplankton.