INVESTIGATORS: Laurence P. Madin Woods Hole Oceanographic Institution Woods Hole, MA 02543 508-289-2739 lmadin@whoi.edu Stephen M. Bollens Woods Hole Oceanographic Institution Woods Hole, MA 02543 508-289-3213 sbollens@whoi.edu Barbara K. Sullivan Graduate School of Oceanography University of Rhode Island Narragansett, RI 02882 401-792-6132 bsull@gsosun1.gso.uri.edu Grace Klein-MacPhee Graduate School of Oceanography University of Rhode Island Narragansett, RI 02882 401-792-6695 gracemac@gsosun1.gso.uri.edu Grant Period: July 1, 1993 - January 31, 1996
MOCNESS samples are being sorted, identified and enumerated by members of our group at WHOI (10 m2 MOCNESS) and URI/GSO (1 m2 MOCNESS). Subsamples of predators are being examined microscopically for gut contents.
Shipboard experimental work has included incubations to determine digestion or gut passage times of predators eating copepods and copepod eggs. Feeding experiments were also done to provide samples of predators with known target species as prey for antibody analysis.
The pelagic hydroids which were abundant components of the plankton at the well-mixed site were brought back to WHOI and GSO and maintained in continuous culture. A number of observations and experiments on feeding behavior, feeding rates, and growth responses to food supply and mixing were conducted with these cultures.
With supplemental grant support from NURC/UCAP in Connecticut, we used a ROV on two Process cruises in 1995 to survey bottom habitats for the presence of attached hydroid colonies that might be the source of the suspended fragments. Videotape, suction samples and grab samples are being analyzed from 4 sample regions on the Bank.
Our group has worked with a subcontractor, Hydros Inc., to develop a polyclonal antibody method for the detection of Calanus finmarchicus in the guts of predators. This is particularly important for predators like crustaceans which chew the prey into pieces too small to identify microscopically.
During 1995, we have provided support and set-up assistance to get the 10 m2 MOCNESS system installed and operating on the ships conducting the Broad Scale survey. Samples with the MOC-10 have been included in all Broad Scale cruises in order to provide distribution and abundance data for the larger predators. These samples will be sorted and identified in our labs.
Feeding studies on the process cruises included gut contents analysis and digestion time measurements for ctenophores (Pleurobrachia, Bolinopsis) collected by divers, gut passage time determinations for decapod crustaceans (Crangon, Dichelopandalus) isopods (Cirolana) and amphipods (Themisto), and preparation of predators with known prey in their guts for tests of the antibody methods.
The suspended hydroid colonies which dominated the plankton at some stations in 1994 were also found on all cruises in 1995, though in lower numbers. Observations and experiments conducted on process cruises and in our laboratories at WHOI and URI demonstrated that the hydroids (principally Clytia gracilis) were able to feed effectively on eggs and nauplii of Calanus finmarchicus and other copepods, and on larval cod. A short manuscript concerning the occurrence of the hydroids and their potential predatory impact has been prepared and submitted to Deep- Sea Research.
Other laboratory experiments with the hydroids have demonstrated the effect of food supply and mixing rate on growth rate and colony structure of the hydroids. These results will help us interpret the life history of Clytia on Georges Bank.
Sampling conducted with the NURC/UCAP ROV in May and June-July revealed large numbers of Clytia colonies on the bottom in the Northeast Peak region of the bank, upstream from the well-mixed central region where the suspended hydroids mainly occur. Some of the ROV data have been analyzed by a WHOI Summer Student Fellow, and will be prepared for publication this fall.
Development of the polyclonal antibody for Calanus finmarchicus has progressed to the point where we now have large quantities of an antibody to a protein that appears to be specific to Calanus. Tests of cross-reactivity have been conducted with all the principal predators that might consume Calanus. A protocol for fixing predator samples at sea has been developed to allow us to use the antibody on preserved samples on shore, and we have approximately 700 such samples, representing 18 species of predators. Final details of the laboratory protocol for washing and analyzing these samples are being worked out.
Madin, L.P., S.M. Bollens, E. Horgan, M. Butler, J. Runge, B.K. Sullivan, G. Klein-MacPhee, E. Durbin, A. Durbin, A. Bucklin and M.E. Clarke. Voracious planktonic hydroids: Unexpected predatory impact on a coastal marine ecosystem. Deep-Sea Res. (submitted)