Zooplankton community grazing impact on a bloom of Alexandrium fundyense in the Gulf of Maine

Grazing rates by a zooplankton community were measured in situ by a radiotracer cell method at depths of 1 m and 4 m at the upper tidal freshwater portion of a regulated river over a year. The objectives were to evaluate the likely grazing impact on the river phytoplankton community and to produce predictive models by regressing the measured grazing rates against zooplankton biomass, temperature and food concentrations (represented by chlorophyll a). Grazing attained rates (overall average 0.2 day-1, range 0.01-0.59 day-1, expressed as instantaneous mortality rates of algal cells) comparable to those reported for lentic zooplankton communities. The measured community grazing rates were predictable largely as a function of total biomass or rotifer biomass and surface temperature for 1 m depth, and as a function of total biomass or juvenile copepod biomass and surface temperature for 4 m depth, with all-positive regression coefficients in the models. Owing to the predominance of microzooplankton in the river, the impact of zooplankton community grazing appears likely to be linked to a small-size fraction of the phytoplankton community all year. Management strategies for river water quality may need to take account of possible functional demarcation of grazing by river zooplankton.

Download Full-text

Nutrients and water masses in the Gulf of Maine–Georges Bank region: Variability and importance to blooms of the toxic dinoflagellate Alexandrium fundyense

Deep Sea Research Part II Topical Studies in Oceanography ◽

10.1016/j.dsr2.2013.08.003 ◽

2014 ◽

Vol 103 ◽

pp. 238-263 ◽

Cited By ~ 15

Author(s):

D.W. Townsend ◽

D.J. McGillicuddy ◽

M.A. Thomas ◽

N.D. Rebuck

Keyword(s):

Gulf Of Maine ◽

Water Masses ◽

Georges Bank ◽

Toxic Dinoflagellate ◽

Alexandrium Fundyense

Download Full-text

Blooms of the toxic dinoflagellate Alexandrium fundyense in the western Gulf of Maine in 1993 and 1994: A comparative modeling study

Continental Shelf Research ◽

10.1016/j.csr.2007.06.008 ◽

2007 ◽

Vol 27 (19) ◽

pp. 2486-2512 ◽

Cited By ~ 13

Author(s):

Charles A. Stock ◽

Dennis J. McGillicuddy ◽

Donald M. Anderson ◽

Andrew R. Solow ◽

Richard P. Signell

Keyword(s):

Gulf Of Maine ◽

Comparative Modeling ◽

Toxic Dinoflagellate ◽

Alexandrium Fundyense ◽

Modeling Study

Download Full-text

Advancing an Ecosystem Approach in the Gulf of Maine

Advancing an Ecosystem Approach in the Gulf of Maine ◽

10.47886/9781934874301.ch11 ◽

2012 ◽

Keyword(s):

Gulf Of Maine ◽

Historical Context ◽

Zooplankton Community ◽

Ecosystem Approach ◽

Environmental Indicators ◽

Zooplankton Abundance ◽

The North ◽

Oscillation Result ◽

The North Atlantic Oscillation ◽

Ecosystem Changes

<i>Abstract</i>.—Numerous studies have examined the dynamics of zooplankton in the Gulf of Maine. Here the authors reanalyze relationships found in these prior studies, using updated data, with the goal of evaluating previously identified zooplankton– environment linkages. These reanalyses support the finding that major changes occurred in the zooplankton community during the late 1980s and again in the late 1990s. Evidence for a broader change in the ecosystem during these periods and mechanisms responsible for changes in the zooplankton are discussed. In general, the results of previous studies are upheld, but it is shown that the relationship between the environmental indicators and zooplankton change through time. This result implies that all data collected in the Gulf of Maine must be considered within a historical context and that the observed environmental–zooplankton linkages are still not well understood. It is possible that changes in the seasonal cycle or shifts in the pressures systems responsible for the North Atlantic oscillation result in nonstationary environmental–zooplankton relations. These results indicate that a mechanistic understanding is required to explain the documented environment–zooplankton linkages rather than correlative explanations. Since the causes of the late-1980s and late-1990s regime shifts are still unclear, future ecosystem-based management in the Gulf of Maine must be supported by continued observation and analysis to identify ecosystem changes soon after they occur. Scenario-driven modeling also is needed to provide guidance as to how the ecosystem will respond to future changes in zooplankton abundance and community structure.

Download Full-text