Download Georges Bank Broad-Scale Standard Grid.

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?
Began with 38 Stations
in 1995
Added station 39
in 1996
Added stations 40
in 1997
Added station 41
in 1998
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
S. GLOBEC
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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
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?
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
Integration and Synthesis of Georges Bank Broad-scale
Survey Results.
Georges Bank Broad-Scale Standard Grid.
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.
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.
Integration and Synthesis of Georges Bank Broad-scale
Survey 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.
Integration and Synthesis of Georges Bank Broad-scale
Survey 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 filtered relative 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.
Integration and Synthesis of Georges Bank Broad-scale
Survey Results.
Broad-scale patterns in the distribution of key species
produced by Ted Durbin
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.
Integration and Synthesis of Georges Bank Broad-scale
Survey 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:
1)
To examine the relationships between these biota and various
environmental conditions, especially hydrography and Slope Water
intrusions.
2)
To study the overall community structure within the Georges Bank
macrozooplankton and micronekton using multivariate analyses.
3)
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.
Integration and Synthesis of Georges Bank Broad-scale
Survey 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.
Chronology
End