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A Review of Zooplankton Communities in the Massachusetts Bay/Cape Cod Bay System

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A Review of Zooplankton Communities in the Massachusetts Bay/Cape Cod Bay System Jefferson T. Turner UMass Dartmouth OMSAP Meeting October 21, 2003 – PowerPoint PPT presentation

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Title: A Review of Zooplankton Communities in the Massachusetts Bay/Cape Cod Bay System


1
A Review of Zooplankton Communities in the
Massachusetts Bay/Cape Cod Bay System
  • Jefferson T. Turner
  • UMass Dartmouth
  • OMSAP Meeting
  • October 21, 2003

2
  • Concern that the MWRA effluent discharge might
    adversely change the zooplankton community in
    Massachusetts Bay
  • Several attempts to develop a Contingency Plan
    zooplankton threshold
  • In 2000 OMSAP recommended Since the
    Massachusetts and Cape Cod Bays system flows like
    a conveyor belt from north to south, MWRA
    should develop a method for analyzing the current
    data spatially and temporally to contrast
    differences between the northern boundary
    stations and Cape Cod Bay. (OMSAP 2000).

3
Zooplankton Threshold Study Objectives
  • Review relevant literature for evidence of
    specific responses that could be used to
    postulate a zooplankton threshold
  • Explore the conveyor belt hypothesis of north
    to south transport of zooplankton communities
  • Review available data to examine the effects of
    local and regional environmental factors on
    zooplankton communities in Mass Bay
  • Determine whether an appropriate zooplankton
    threshold can be developed

4
MWRA Zooplankton Monitoring Stations
5
Review of the Literature - Summary
  • Zooplankton taxa in the area MWRA monitors are
    typical of the Gulf of Maine and New England
    coastal waters in terms of taxonomic composition,
    seasonal cycles and life history.
  • Genetic studies by Bucklin indicate that Calanus
    finmarchicus and Pseudocalanus spp. are part of a
    genetically homogeneous population from the Gulf
    of St. Lawrence through the Gulf of Maine to
    Georges Bank. This is not the case with Acartia
    tonsa.

6
conveyor belt hypothesis
  • Can advection of zooplankton population at the
    northern boundary through the nearfield with
    subsequent transport southward, ultimately lead
    to changes in zooplankton in Cape Cod Bay?
  • Suggestion was that the timing of peaks in
    important zooplankton species could be
    sequential, with taxa peaking first at the
    northern boundary, later in the nearfield and
    southern Massachusetts Bay, and ultimately
    reaching Cape Cod Bay

7
Conveyor belt hypothesis not supported by the
MWRA data
  • pulses of zooplankton not evident in north to
    south data within the bays rather pulses often
    occur simultaneously or bays leads boundary
  • Peak C. finmarchicus abundances often coincident
    or occur earlier at the southern stations than
    northern.
  • No consistent north-south sequence in peak
    abundances for O. similis, Paracalanus parvus,
    Pseudocalanus spp., Paracalanus/Pseudocalanus
    copepodites, and Centropages typicus.

8
PCA analysis found two major influences on
zooplankton community structure
  • Seasonal/Temperature gradient in communities.
    Temperature is positively loaded on Factor 1,
    DO is negatively loaded. Cold-water taxa which
    are abundant relatively early in the year, such
    as cirripede larvae have negative or weak
    loadings on factor 1, taxa abundant in warm
    summer waters (e.g. Oithona similis, Osim) have
    positive loadings.
  • Estuarine/offshore gradient in community
    structure. Taxa abundant in somewhat turbid,
    low salinity, Harbor waters like Acartia
    hudsonica (Ahuds) have positive loading on Factor
    2. Taxa more abundant in higher salinity, clearer
    offshore waters like Oithona similis and
    Paracalanus parvus (Ppar) have negative Factor 2
    loadings.

9
Long-term measurements Sorting out species
responses
  • Hemispheric scale processes may be influencing
    the response and abundance
  • (Turner et al. May 2003 International Zooplankton
    Production Symposium, Spain)

10
Findings
  • The zooplankton community in Mass Bay is
    dominated by species which have widespread
    distributions in the Gulf of Maine and some of
    which are found throughout the East coast of the
    US
  • Zooplankton abundance tends to follow a
    predictable temporal pattern, with peak abundance
    in mid-summer and lower levels in spring and fall
  • Blooms tend to co-occur throughout system
    regional differences not strongly evident
  • The conveyor belt concept not evident in the
    zooplankton data as treated by cluster analysis
    and PCA
  • The beginning of discharge at the MWRA outfall in
    September 2000 had no clear effect on zooplankton
    abundance or community structure

11
Conclusions
  • Unable to define a meaningful simple numerical
    threshold for zooplankton community data at this
    time.
  • MWRA will continue to evaluate and interpret the
    zooplankton community in its interpretive
    synthesis reports.
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