TITLE:  SHEBA/JOIS Mesozooplankton abundance and biomass
PIs:
Drs. Carin Ashjian and Robert Campbell
Phone:  508-289-3457 (Ashjian) and 401-874-6692 (Campbell)
e-mail:  cashjian@whoi.edu, campbell@gso.uri.edu

NSF GRANT: 0CE9707184

DATASET OVERVIEW:
This data set contains mesozooplankton biomass and abundance from net tows conducted during the SHEBA drift
experiment.  Two data sets are archived.  The first, SHEBA_ALLTAXA.xls, presents total displacement 
volume biomass as both dry weight (mg dw m-3) and carbon (mg C m-3) and abundances of all taxa, including 
copepodite stages for the copepods, as # m-3.  Date, position (latitude, longitude), depth intervals for 
each tow, and bottom depth (when available) are presented.  The same positions are used for all tows 
conducted on a specific date.  The second data set, SHEBA_NapuliarCounts.xls, presents the stage specific 
naupliar abundances for the dominant copepod taxa as integrated abundance (# m-2) in each depth interval. 
The depth intervals for each tow, date,  position, and net mesh also are indicated.  In general, the 
copepod species enumerated correspond to the genera and species presented in the SHEBA_ALLTAXA.xls data 
set, however species could not be reliably differentiated at the naupliar stage. 

METHODS:
Vertically discrete sampling of the water column zooplankton was conducted every 10-14 days by vertical 
hauls using a 1-m2 mouth area, 6-m length ring net equipped either with 150 µm or 53 µm mesh nets, a flow me
meter, and a Sea-Gear Inc. double release mechanism to permit sampling at selected depths.  The net was 
deployed on the down cast open with the mouth upwards, and hence not collecting plankton.  The flow meter 
was prevented from incrementing on the down cast by a pin that immobilized the tail; the tail was freed 
just prior to starting the up cast by tripping the first release of the double trip and pulling the pin 
away from the tail.  The net was closed using the second release of the double trip mechanism at the upper
depth of the desired depth interval.  Pre-determined depth intervals were sampled (0-50 m, 50-100 m,
100-200 m, 200-1500 m, 1500-2800 m), with occasional sampling over other depth intervals when time was 
limiting.  Sampling with the 53 µm mesh net was confined to the upper 100 m.  No sampling with the 53 µm me
mesh nets was conducted past early August, 1998.  Sampling was conducted for the most part during the day, 
even when little or no light was present.  Samples were preserved in 4% buffered formaldehyde immediately 
following collection.  Total zooplankton biomass was estimated from determination of displacement volume, 
following removal of fish and large jellies but retaining other macrozooplankton such as amphipods, and 
conversion to equivalent dry weight and carbon content using empirical relationships (Wiebe et al., 1975, 
1988; Postel et al., 2000).  Samples containing excessive quantities of phytoplankton were not included in 
the displacement volume analysis.  

Zooplankton from the 150 µm mesh net samples were enumerated at the Université Laval for all plankton ty
pes except species specific copepod nauplii.  Large animals (e.g., cnidarians, ctenophores, fish larvae, 
decapods) first were removed from the sample and counted.  Subsamples then were obtained with a pipette.  
Successive aliquots were enumerated until at least 150 of the target copepod species were encountered or 
until the entire sample had been examined.  Five target species were selected:  Calanus glacialis, C. 
hyperboreus, Metridia longa, Microcalanus pygmaeus, and Oithona similis.  Target copepod species were 
identified to copepodite stage.  Nauplii and eggs of the dominant copepods from the 53 µm mesh net s
amples and, for times when no 53 µm mesh net samples were available, from 150 µm mesh net samples, we
re enumerated at the University of Rhode Island.  When present in sufficient abundance, 150 individuals of 
each of the target species were counted.

REFERENCES

Postel, L., Fock, H., Hagen, W., 2000.  Biomass and abundance. In: Harris, R., Wiebe, P., Lenz, J, Skjoldal,
   H.R., Huntley, M. (Eds.), ICES Zooplankton Methodology Manual, Academic Press, San Diego, pp. 83-192.
Wiebe, P.H., Boyd, S., Cox, J.L., 1975.  Relationships between zooplankton displacement volume, wet weight, 
   dry weight, and carbon. Fishery Bulletin 73, 777-786.
Wiebe, P., 1988. Functional regression equations for zooplankton displacement volume, wet weight, 
   dry weight, and carbon: a correction.  Fishery Bulletin 86, 833-835.