Peter Wiebe, Principal Investigator
Charles Greene (Cornell University), Mark Benfield (Louisiana State University), Co PIs
This project has focused on establishing how physical and biological processes in the Gulf of Maine (GOM) interact to regulate the recruitment of Calanus finmarchicus to
Georges Bank each year. To address this question , a series of five survey cruises were conducted in the GOM during the autumns of 1997 through 1999. Each cruise included survey transect lines in Wilkinson, Jordan, and Georges Basins , along which multi-frequency acoustic , video, hydrographic , and bio-optical data were collected. The surveys were conducted using ahigh-speed, deep-towed vehicle referred to as the BIOMAPER II. This vehicle is configured with afive-frequency sonar system, a video plankton recorder (VPR), and a set of hydrographic as well as bio-optical sensors. MOCNESS (Multiple Opening/Closing Net and Environmental Sensing System) tows also were conducted in each of the deep basins . The MOCNESS samples were collected for ground-truthing and inter-comparisons with the acoustic and VPR data as well as to provide information on the abundance, distribution, and size of Calanus adult and copepodite stages.
Evaluation of the abundance and size distribution of Calanus continued during the year with the completion of ten more sets of net samples (8 depth strata per tow ). A total of 20 sets of nets have been analyzed to date. Night tows from each of five cruises and three basins have been completed and a total of five day tows from Wilkinson and Jordan Basins are done. Day tows from Georges Basin are yet to be examined . Larger Calanus stage V copepodites were isolated for genetic analysis by Ann Bucklin to determine the presence of Calanus glacialis.'
Silhouette analysis of the entire community population in one tow has been completed. This involved identifying the organisms to taxonomic group and measuring each animal for length and then obtaining a wet weight estimate using both experimentally and empirically derived formulae (Davis & Wiebe , 1985). These data were used to compare with BIOMAPER-II acoustic and VPR optical data.
The most significant result from this field study so far has been linking the order of magnitude reduction in C. finmarchicus abundance observed in the GOM during autumn
1998 (relative to the autumns of 1997 and 1999) to an NAO-driven modal shift in the NW .Atlantic's coupled slope water system. Retrospective analyses of continuous
plankton recorder and hydrographic time-series data have enabled us to place this result in the context of climate-driven changes in ocean circulation observed over the past half century (Greene and Pershing, 2000 ; MERCINA submitted).
Benfield, M.C., P.H. Wiebe, T.K. Stanton, C.S. Davis, S.M. Gallager, and C.H. Greene. 1998. Estimating the spatial distribution of zooplankton biomass by combining Video Plankton Recorder and single-frequency acoustic data. Deep-Sea Research II. 45(7):1175-1199.
Greene, C.H., P.H. Wiebe, C. Pelkie, M.C. Benfield, and J.M. Popp. 1998. Three-dimensional acoustic visualization of zooplankton patchiness . Deep-Sea Research
Greene, C.H., P.H. Wiebe, A. J. Pershing, G. Gal, J.M. Popp, N. J. Copley, T. C. Austin, A. M. Bradley, R. G. Goldsborough, J. Dawson, R. Hendershott, and S. Kaartvedt. 1998. Assessing the distribution and abundance of zooplankton: a comparison of acoustic and net-sampling methods with D-BAD MOCNESS. Deep-Sea Research II. 45(7):1219-1237.
Greene, C.H., and A.J. Pershing. 2000. The response of Calanus finmarchicus populations to climate variability in the Northwest Atlantic: Basin-scale forcing associated with the North Atlantic Oscillation. ICES J. Mar. Sci. 57: 1536-1544.
MERCINA. 2001. Oceanographic responses to climate in the Northwest Atlantic. Oceanography 14: 77-83. Wiebe, P.H., T.K. Stanton, C.H. Greene, M.C. Benfield, H.M. Sosik , T. Austin, J.D. Warren, and T. Hammar. In Press. BIOMAPER II: an integrated instrument platform for coupled biological and physical measurements in coastal and oceanic regimes. IEEE J. Ocean. Eng.
This grant also has supported our participation in trans-Atlantic efforts to study the responses of North Atlantic shelf ecosystems to climate variability and change. In
addition to six presentations on this topic at various national meetings, the following presentations have been made internationally:
Greene, C.H., and A.J. Pershing. The response of Calanus finmarchicus populations to climate variability in the Northwest Atlantic: basin-scale forcing associated with the
North Atlantic Oscillation. ICES Symposium: Population Dynamics of Calanus in the North Atlantic, Tromso, Norway; August 1999.
Greene, C.H. The response of Northeast and Northwest Atlantic shelf ecosystems to climate variability and change (Invited Symposium Speaker). ASLO Summer Meeting,
Copenhagen, Denmark; June 2000.
Greene, C.H., and A.J. Pershing. Trans-Atlantic responses of Calanus finmarchicus to basin-scale forcing associated with the North Atlantic Oscillation (Invited Symposium
Speaker). American Geophysical Union Chapman Conference on the North Atlantic Oscillation, Ourense, Spain; November 2000.
Greene, C.H., and A.J. Pershing. Trans-Atlantic responses of Calanus finmarchicus to basin-scale forcing associated with the North Atlantic Oscillation (Invited Symposium Speaker). 70th Anniversary of the Continuous Plankton Recorder Surveys of North Atlantic Symposium, Edinburgh, Scotland; August 2001.
The presentation at the ASLO Summer Meeting during June 2000 was part of a special symposium and workshop on this topic organized by C. Greene and Dr. Benjamin Planque (IFREMER). This workshop led to the formation of a new working group dedicated to investigating Marine Ecosystem Responses to Climate In the North Atlantic (MERCINA -http://www.geo.cornell.edu/mercina/). The primary goal of the group is to provide a climatological context for interpreting the findings from large, multi-national field programs conducted on the continental shelves of the North Atlantic. A second meeting of this working group will be held at the AGUTASLO Ocean Sciences Meeting in Hawaii during February 2002. This working group meeting is being organized by C. Greene and Dr. Michael Fogarty (US GLOBEC Steering Committee Chairman).