Dian J. Gifford, Michael E. Sieracki and Igor Belkin Title: US-GLOBEC: Cross-Frontal Processes and Recruitment Variability on Georges Bank - Diet of Calanus finmarchicus Copepodids and Nauplii
Principal Investigators: Dian J. Gifford, Michael E. Sieracki and Igor Belkin
This proposal is one of a cluster of three linked proposals submitted for GLOBEC Phase 3 and recommended for funding. The other 2 proposals are: (1) US-GLOBEC: Cross-frontal distributions and exchange of zooplankton on Georges Bank; K. Wishner, PI and (2) US-GLOBEC: Cross-frontal fluxes and mixing on Georges Bank; D. Hebert and J. Barth, PIs. The Hebert and Barth proposal is focused on physical oceanography; the Gifford et al. and Wishner proposals combine biology and physics.
The major scientific questions addressed by the three proposals are:
** What is the 3-dimensional circulation associated with the target fronts over a fortnightly time-scale? (Hebert and Barth; Belkin)
** What is the effect of tidal current variability over semi-diurnal and fortnightly time-scales? (Hebert and Barth; Belkin)
** What are the dynamics and rates of cross-frontal exchange of water? (Hebert and Barth; Belkin)
** What water masses are present? (Hebert and Barth; Belkin)
** What are the distributions of target zooplankton species across the fronts? (Wishner)
** What is the potential prey field (nanoplankton and microplankton) of target copepods and larval fish in the frontal regions? (Gifford and Sieracki )
** What are the rates of feeding and growth of Calanus nauplii and copepodids at the different cross-frontal locations? (Gifford and Sieracki)
** What are the cross-frontal exchange rates of zooplankton (Wishner), nano- and microplankton (Gifford and Sieracki)
** How do biological and physical processes interact to control cross-frontal exchanges of target organisms? (Wishner; Gifford, Sieracki and Belkin). For example, how do vertical distributions and migration of zooplankton interact with cross-frontal exchange processes? (Wishner)
** How does the spatial variability in frontal movement influence the distribution and exchange of organisms at different locations and depths? (Wishner; Gifford, Sieracki and Belkin)
** How do temporal variations of the front (e.g., spring/neap, tidal and diel scales ) interact with populations of target organisms? What are the potential consequences of these proceses for recruitment of target organisms? (Wishner; Gifford, Sieracki and Belkin)
The work will be done as a coordinated two-ship operation, using one ship for the SEASOAR work of Hebert and Barth and one ship for the biological/physical work of Gifford, Sieracki, Belkin and Wishner. The work will be done at two frontal locations at times which encompass the life cycles of the target organisms: (1) the Northeast Peak Front (late March, when the thermal signature of this front is most strongly developed) and the Southern Flank Tidal Mixing Front (late June, when the thermal signal of this front is strongly developed.
Specific cruise activities in each frontal area include:
** High resolution SEASOAR surveys around an isopycnal float in the frontal areas (Hebert and Barth)
** High resolution SCANFISH surveys in the frontal areas (Belkin)
** Cross-frontal transects of hydrography, zooplankton, microplankton, and nanoplankton (SCANFISH, 1 m-MOCNESS, CTD, GO-FLO rosette (Wishner; Gifford, Sieracki and Belkin)
** Time series stations (Wishner; Gifford, Sieracki and Belkin)
** Zooplankton vital rates (Gifford and Sieracki)
Sensors mounted on the SEASOAR include dual temperature and conductivity sensors, a fluorometer, transmissometer, and a Microsoar. Sensors mounted on the SCANFISH include temperature and conductivity sensors, a fluorometer, and oxygen sensor. Thus, the SEASOAR (Hebert and Barth) and SCANFISH (Gifford, Sieracki and Belkin in conjunction with Wishner) will be doing near real-time mapping of cross-frontal distributions of a wide variety of biological, physical and chemical parameters. We will be able to evaulate cross-frontal exchanges and mixing of water, including numerous chemical and biological characteristics. These data will be used in conjunction with species distributional data to determine cross-frontal exchanges of nanophytoplankton, nanozooplankton, microphytoplanktpon, microzooplankton, and mesozooplankton. The sampling scheme takes account of the semi-weekly and diurnal tidal cycle, day/night cycle, Bank topography, etc.
Anticipated direct collaborators include Barbara Sullivan (cross-frontal distribution and abundance of small predators in MOC-1 samples), Larry Madin (predator feeding rates), Ann Bucklin (Pseudocalanus cross-frontal distributions and genetics), Bob Beardsley (Northeast Peak moorings), Jim Irish (Southern Flank moorings), and Jim Bisagni (front detection via remote sensing).