Maintenance of Pseudocalanus spp.on Georges Bank: differential use of the Bank by the two species

Ann Bucklin¹, Peter H. Wiebe², Christopher A. Manning¹,

and Dennis J. McGillicuddy²

¹University of New Hampshire, Durham NH USA

²Woods Hole Oceanographic Institution, Woods Hole MA USA

Slide 2

"Pseudocalanus moultoni and P"

Pseudocalanus moultoni and P. newmani are morphologically cryptic but genetically distinct, differing by 18% in mtCOI sequence.

Multiplexed, species-specific PCR (SS-PCR) was used to identify individual copepods. Reactions were done in 96-well plates, with controls.

For the U.S. GLOBEC samples, only adult females were identified.

Slide 4

1999 Broad-scale mapping for Pseudocalanus spp.

Objectively-analyzed maps for vertically-integrated (top-to-bottom) 1999 distributions showed parallels with the 1997 maps, models, and cartoons.

Early Spring distributions (source regions) were apparently distinct; Summer distributions (destinations) were overlapping on top of Georges Bank.

1999 total abundances of Pseudocalanus spp.

Bank-wide totals for each species were determined by mapping abundance data for three strata (0-15m, 15-40m, and below 40m) to a standard grid and inter/extrapolating abundances throughout the grid.

Regional analysis using a standard grid

1999 regional abundances of Pseudocalanus spp.

Total monthly abundances for each species for each region showed differences in month-to-month patterns of abundance for all regions except the Northeast Peak.

Why does vertical distribution matter?

Vertical distribution determines transport trajectories on the Bank: copepods in the surface waters (0- 15 m) are advected by Eckman transport.

Copepods below the Eckman layer are less subject to transport. The tidal mixing front may help retain deeper-dwelling copepods on the Bank.

Remaining deeper in the water column may represent a strategy to aid retention and avoid loss from Georges Bank for small copepods like Pseudocalanus spp.

1999 vertical distributions of Pseudocalanus spp.

1999 vertical distributions by region

Pseudocalanus spp. in the Western Gulf of Maine

In MARMAP surveys 1977 – 1987, Pseudocalanus spp. shows a seasonal cycle of abundance, with two population centers:

Western Gulf of Maine

Georges Bank

Davis (1984) hypothesized the Western Gulf of Maine is a source region for the Georges Bank population

McGillicuddy et al. (1998) concluded that the populations are functionally distinct, with geographically-specific regions of growth and mortality

"The two Pseudocalanus spp"

The two Pseudocalanus spp. likely have distinct patterns of transport, retention, and maintenance on Georges Bank.

There were distinct source regions for the two species in both 1997 and 1999. By June, the species’ distributions were overlapping on the crest of the Bank.

Based on total Bank-wide abundance, the spring evolution of abundance of the two species was similar, with earlier build-up for P. newmani.

The spring evolution of abundance of the two species differed among five regions of Georges Bank, with the exception of the Northeast peak.

Vertical distributions of the two species differed both Bank-wide and within each region, with P. moultoni less abundant in the top 15 m.

Acknowledgments


	Ann Bucklin¹, Peter H. Wiebe², Christopher A. Manning¹,
	and Dennis J. McGillicuddy²
	¹University of New Hampshire, Durham NH USA
	²Woods Hole Oceanographic Institution, Woods Hole MA USA


	Pseudocalanus moultoni and P. newmani are morphologically cryptic but genetically distinct, differing by 18% in mtCOI sequence.
	Multiplexed, species-specific PCR (SS-PCR) was used to identify individual copepods. Reactions were done in 96-well plates, with controls.
	For the U.S. GLOBEC samples, only adult females were identified.


	Objectively-analyzed maps for vertically-integrated (top-to-bottom) 1999 distributions showed parallels with the 1997 maps, models, and cartoons.
	Early Spring distributions (source regions) were apparently distinct; Summer distributions (destinations) were overlapping on top of Georges Bank.


	Bank-wide totals for each species were determined by mapping abundance data for three strata (0-15m, 15-40m, and below 40m) to a standard grid and inter/extrapolating abundances throughout the grid.


	Total monthly abundances for each species for each region showed differences in month-to-month patterns of abundance for all regions except the Northeast Peak.


	Vertical distribution determines transport trajectories on the Bank: copepods in the surface waters (0- 15 m) are advected by Eckman transport.
	Copepods below the Eckman layer are less subject to transport. The tidal mixing front may help retain deeper-dwelling copepods on the Bank.
	Remaining deeper in the water column may represent a strategy to aid retention and avoid loss from Georges Bank for small copepods like Pseudocalanus spp.


	In MARMAP surveys 1977 – 1987, Pseudocalanus spp. shows a seasonal cycle of abundance, with two population centers:

	Western Gulf of Maine
	Georges Bank

	Davis (1984) hypothesized the Western Gulf of Maine is a source region for the Georges Bank population

	McGillicuddy et al. (1998) concluded that the populations are functionally distinct, with geographically-specific regions of growth and mortality


	The two Pseudocalanus spp. likely have distinct patterns of transport, retention, and maintenance on Georges Bank.
	There were distinct source regions for the two species in both 1997 and 1999. By June, the species’ distributions were overlapping on the crest of the Bank.
	Based on total Bank-wide abundance, the spring evolution of abundance of the two species was similar, with earlier build-up for P. newmani.
	The spring evolution of abundance of the two species differed among five regions of Georges Bank, with the exception of the Northeast peak.
	Vertical distributions of the two species differed both Bank-wide and within each region, with P. moultoni less abundant in the top 15 m.