Suspended planktonic hydroids on Georges Bank: distribution, abundance, and impacts of a rapacious predator

J. J. Pierson, E. G. Durbin, and B. K. Sullivan

Hydroids are marine hydrozoans in the Phylum Cnidaria. They have a two-stage life cycle in which generations of sessile benthic colonies, called polyps, alternate with generations of pelagic medusa. The polyp stage is usually found attached to seaweed, rocks, and other structures on the seafloor, but dynamic processes can detach and fragment the colonies, suspending the polyps in the water. Madin et al. (1996) found that although hydroids had previously been reported suspended in the water on Georges Bank, they have not been considered important organisms in the pelagic community.

In this study, we attempt to quantify the distribution and abundance of hydroid polyps on the crest of Georges Bank throughout the winter and spring of 1995, 1996, 1997, and 1998. In addition we are going to examine how these patterns of distribution and abundance could affect the zooplankton population.