Intermingling of two Pseudocalanus species on Georges Bank

1. Intermingling of two Pseudocalanusspecies on Georges Bank D.J. McGillicuddy, Jr. Woods Hole Oceanographic Institution A. Bucklin University of New Hampshire Journal of Marine Research 60, pp. 583-604, 2002.

2. 1997 Broadscale Survey Data P. moultoni P. newmani Species-specific PCR (Bucklin et al., 2001)

3. The forward model: an advection-diffusion-reaction equation Tendency Diffusion Reaction (biological sources and sinks) Advection C concentration v velocity K diffusivity Cobs(t0) Cobs(t1) time The forward problem

5. Observations: P. Moultoni Models Observations: P. newmani

9. Are the inverse solutions ecologically realistic? R(x,y,t) bounded by –100 to +100 individuals m-3 day-1 [most fall between -10 to +10] C5 moulting potential: Mean C5 abundance 2500 individuals m-3 (Incze pump samples: April 1997, May 1997, June 1995) Stage duration in GB conditions: 5 days (McLaren et al., 1989) Implied moulting flux of 500 individuals m-3 day-1

10. Are the inverse solutions ecologically realistic? Predation potential: Model predicted rates of 3-10% day-1 Bollens et al. specific rates of predation on C. finmarchicus and Pseudocalanus spp. copepodites based on observed predator abundance and feeding rates http://userwww.sfsu.edu/~bioocean/research/gbpredation/gbpredation1.html

11. Conclusions (I) • Inverse method results in convergent solutions • Geographically specific regions of growth/mortality • These vary seasonally according to animal abundance • patterns, the circulation, and their orientation • Two main balances: • Tendency / source (weak currents or aligned gradients) • Tendency / source / advection

12. Conclusions (II) Resulting biological sources and sinks ecologically realistic -- R(x,y,t) bounded by independent rate estimates C5 moulting flux Predation by invertebrates and vertebrates Emerging conceptual model: -- Distinct source regions in late winter P. moultoni on NW flank P. newmani on NE peak and Browns Bank -- During the growing season, GB circulation blends these reproducing (not interbreeding) populations such that their distributions overlap by early summer.

13. Caveats Physics -- errors in the circulation -- vertical shear Biology -- density dependence vs. “geographic” formulation -- multistage models, behavior, etc. Observational limitations -- only adults -- upper 40m

15. Are the inverse solutions ecologically realistic? R(x,y,t) bounded by –100 to +100 individuals m-3 day-1 [most fall between -10 to +10] C5 moulting potential: Mean C5 abundance 2500 individuals m-3 (Incze pump samples) Stage duration in GB conditions: 5 days (McLaren et al., 1989) Implied moulting flux of 500 individuals m-3 day-1 Predation potential: Hydroid ingestion rate: 0.25 cop. hydr-1 day-1 (Madin et al., 1996) Characteristic abundance: 10,000 hydranths m-3 Potential consumption rate: 2500 copepods m-3 day-1 Pseudocalanus adults ~15% of total postlarvae (Davis, 1987) Hydroid predation on Pseudocalanus: 200 individuals m-3 day-1

17. Pseudocalanus spp.MARMAP 1977-1987 Two population centers: Western Gulf of Maine Georges Bank Davis (1984) hypothesis: Western Gulf of Maine is a source region for the Georges Bank population Concentration (# m-3)

18. General circulation during the stratified season Beardsley et al. (1997)

19. A first attempt to simulate the data…

20. Derivation of the adjoint model (1) Define a cost function J: Problem: Given observations C0(t0) and C1(t1), find R(x,y) that minimizes J Where λ=λ(x,y,t) are Lagrange multipliers

21. Derivation of the adjoint model (2) We require R at the minimum of (and therefore J) where Adjoint model: It can be shown that:

22. Convergence of the iterative procedure

23. Example results: Mar-Apr to May-Jun Red: source Blue: sink

24. Term-by-Term Diagnosis Observations Biological Source/Sink Advection Diffusion Tendency JF-MA MA-MJ MJ-JA

25. Chlorophyll-aMARMAP 1977-1987O’Reilly and Zetlin (1996) Jan-Feb Mar-Apr May-Jun Jul-Aug Davis (1984) Cutoff for food limitation 0.6 – 1.2 μg Chl l-1 Nov-Dec Sep-Oct Cutoff range

26. ChaetognathsMARMAP 1977-1987Sullivan and Meise (1996) Jan-Feb Mar-Apr May-Jun Jul-Aug Sep-Oct Nov-Dec

27. ECOHAB-GOM Observations • Gulf-wide • distribution • 2) Association with coastal • current • 3) Center of mass • shifts west-to-east • as season progresses Townsend et al. (2001)

28. Some thoughts on model designfor HAB applications Forward models Inverse approaches McG et al. (1998) Fisheries Oceanography, 7(3/4), 205-218. McG and Bucklin (2002) Journal of Marine Research, 60, 583-604. http://science.whoi.edu/users/mcgillic/software/scotia_1.0/

29. END

30. Term-by-Term Diagnosis Continued… Observations Biological Source/Sink Advection Diffusion Tendency JA-SO SO-ND ND-JF

32. Pseudocalanus spp.MARMAP 1977-1987 Concentration (# m-3)

33. Term-by-Term Diagnosis Obs Src Adv Dif Ten JF-MA MA-MJ MJ-JA JA-SO SO-ND ND-JF

34. Term-by-Term Diagnosis Obs Src Adv Dif Ten JF-MA MA-MJ MJ-JA JA-SO SO-ND ND-JF

35. A first attempt to simulate the data…

36. Term-by-term diagnosis Red: source Blue: sink

37. Observations: P. Moultoni Models Observations: P. newmani