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Integration and Synthesis of Georges Bank Broad-scale Survey Results, A Brief Overview. The principal objective of this project is to utilize the very comprehensive U.S GLOBEC broad-scale data sets that now exist to address two overarching questions:

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integration and synthesis of georges bank broad scale survey results a brief overview
Integration and Synthesis of Georges Bank Broad-scale Survey Results,A Brief Overview
  • The principal objective of this project is to utilize the very comprehensive U.S GLOBEC broad-scale data sets that now exist to address two overarching questions:
  • What controls inter-annual variability in the abundance of the target species (cod and haddock larvae, Calanus finmarchicus, and Pseudocalanus spp) on Georges Bank (e.g., bottom up or top down biological processes, or physical advective processes)?
  • How are these processes likely to be influenced by climate variability?
slide2

Began with 38 Stations

in 1995

Added station 39

in 1996

Added stations 40

in 1997

Added station 41

in 1998

slide3

GLOBEC-01: Integration and synthesis of the

Georges Bank Broad-Scale Survey Results.

Principal Investigators and Their Institutions

Northeast Fisheries Science Center:

D. G. Mountain

J. R. Green

P.L. Berrien

San Francisco State University:

S.M. Bollens

University of Maine:

D.W. Townsend

University of New Hampshire:

A. Bucklin

J. Runge

University of Rhode Island:

E.G. Durbin

R. G. Campbell

B.K. Sullivan

Woods Hole Oceanographic Institution:

P.H. Wiebe

C. J. Ashjian

L.P. Madin

D. J. McGillicuddy

J. Quinlan

slide4

GLOBEC-01: Integration and synthesis of the Georges Bank Broad-Scale Survey Results.

Questions Guiding Research

What are the broad-scale distributions of the target species and their predators and prey in relation to physical variables, and how do these change from winter to summer conditions and year to year?

How are the broad-scale distributions of measurement/indices for growth, fertility, respiration, and starvation in the target species related to the distributions of food supply and environmental conditions?

How are predator populations spatially and temporally distributed with respect to their prey (target species) and environmental conditions?

How does the birth date and/or life stage frequency distribution of surviving individuals change during the drift around the Bank?

Is cohort mortality chronic or dominated by episodic events?

Is the probability of survivorship associated with individuals originating from discrete stocks?

slide5

Integration and Synthesis of Georges Bank Broad-scale

Survey Results.

  • The project involves work in two coordinated efforts.
  • 1) Data Completion and Data Management.
  • 2) Data analysis, Integration, and Interpretation
  • A. Hydrographic-biological Relationships
  • B. Integration of Rate Processes and Broad-Scale-Distribution Data Sets
  • C. Building Climatology using Objective Mapping or Kriging
  • D. Modeling
georges bank broad scale standard grid

Georges Bank Broad-Scale Standard Grid.

Integration and Synthesis of Georges Bank Broad-scaleSurvey Results.

The grid spacing is 0.05 degrees in latitude and longitude. Also provided is the area represented by point. There are 2355 points in the grid.

slide9

Standard grids used to:

Systematically map data to foster analyses, and

Produce a comprehensive atlas of physical, chemical, and biological fields

surveyed during the Program

Bathymetry,

Temperature,

Salinity,

Density,

Chlorophyll,

Fluorescence,

Nutrients,

Carbon (for 1999 only),

Currents1 (ADCP, Drogues),

Backscattering (BioS and

HTI, ADCP)

Satellite data (AVHRR, SeaWifs, Winds),

Meteorological data,

Zooplankton biomass,

Species counts (e.g.

Calanus finmarchicus - by stage,

Pseudocalanus spp - by stage,

other inverts, cod, haddock),

predators (Invert, Vert [NMFS-COP]),

Derived rates such as productivity

and mortality.

slide11

Integration and Synthesis of Georges Bank Broad-scaleSurvey Results.

Broad-scale egg samples for both cod and haddock have been processed to consider possible maternal influence on egg viability, assuming increased egg size may reflect better condition and overall viability.

There was no indication that interannual variation in egg

mortality rates was related to variation in egg size.

The eggs were also staged and seasonal egg mortality rates for both species were calculated for each year of sampling.

The mortality rates varied by a factor of two over the duration

of the program.

Comparisons with time series of the local wind stress suggest:

Variability in egg mortality was caused by variations in

wind-driven off-bank transport during the periods of peak

egg abundance.

A particle tracking model, using the observed winds and the observed egg distributions, indicates:

A seasonal loss of eggs consistent with the calculated egg

mortality rates. Both the interannual variability in the winds

and in the egg distributions appear important in determining

the interannual variability in the egg mortality rates.

slide12

Integration and Synthesis of Georges Bank Broad-scaleSurvey Results.

A 1 m2 MOCNESS (0.15 mm mesh) and a zooplankton pump (0.05 mm or 0.035 mm mesh) were used during the broad-scale surveys.

A comparison indicates that C1 and C2 of Calanus and all

C1-C5 of Pseudocalanus were under sampled by the

MOCNESS relative to the pump an average of 37%.

Overestimation of the volume filteredrelative to the

actual volume filtered is the likely cause.

Reproductive rates and mortality rates of target zooplankton species:

The reproductive rates of C. finmarchicus at broad-scale

stations have been calculated for all broad-scale cruises.

A modification of the procedure for estimating C. finmarchicus egg production rates from the preserved broad-scale samples has been developed that explicitly accounts for food limitation effects on clutch size.

slide13

Integration and Synthesis of Georges Bank Broad-scaleSurvey Results.

Broad-scale patterns in the distribution of key species

produced by Ted Durbin

slide14

Calanus finmarchicus total copepodids. Monthly mean abundance (1995-1999), [log10(No m-2+1)].

January

February

March

April

May

June

  • Absence from the bank in January, but higher numbers in the Gulf of Maine (mostly Go C5).
  • Advection of animals onto the NE Peak and along the Southern Flank in February.
  • A build-up of the population in April and May and a decline on the bank in June.
  • A persistent region of low abundance in the shallow, tidally mixed crest of the bank.
slide15

Integration and Synthesis of Georges Bank Broad-scaleSurvey Results.

  • Integration and synthesis of the nutrients and chlorophyll data. Effort involves re-plotting and re-contouring the data sets on phytoplankton chlorophyll and nutrient distributions on Georges Bank. Budgets are now being constructed, which include some of the organic nitrogen and carbon measures.
  • The 10-m2 MOCNESS data on the distribution and abundances of the major macrozooplankton and micronekton predators is being used:
  • To examine the relationships between these biota and various environmental conditions, especially hydrography and Slope Water intrusions.
  • To study the overall community structure within the Georges Bank macrozooplankton and micronekton using multivariate analyses.
  • To integrate the distribution and abundance data with various rate process data derived from GLOBEC process cruises and the literature to generate broad-scale distributions of specific predation mortality rates for each target (prey) taxon.
slide16

Integration and Synthesis of Georges Bank Broad-scaleSurvey Results.

Broad-scale biovolume and bioacoustic backscattering data are being compared to examine seasonal and the year to year variations.

The kriging technique and a newly developed wavelet/fractal

interpolation scheme is being applied to the acoustic and biovolume

data sets to obtain 3D volume renditions.

Work is being completed on data collected on cruises in the fall 1997, 1998, and 1999 to survey diapausing populations of Calanus finmarchicus and their predators in the Gulf of Maine using MOCNESS and BIOMAPER-II. Following the precipitous drop in the NAO index that occurred in

1996, colder and fresher water of Labrador Sea origin entered the

Gulf of Maine in 1998 after a lag of about two years.Coincidently,

the autumn diapausing C. finmarchicus abundance was much lower

in 1998 than in 1997 or 1999.

Despite the substantially lower Calanus abundance in 1998, overall zooplankton biomass levels as revealed by net catches and acoustic indices were comparable between the three years.

Potential competitors (other copepods, the pteropod Limacina

retroversa), and predators (euphausiids, decapods, medusae, and

siphonophores) had enhanced biomass and/or numbers, which may

explain the reduced Calanus in 1998.