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Open AccessArticle

Zooplankton Community Response to Seasonal Hypoxia: A Test of Three Hypotheses

School of Oceanography, University of Washington, Box 357940, Seattle, WA 98195, USA
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Diversity 2020, 12(1), 21; https://doi.org/10.3390/d12010021
Received: 7 November 2019 / Revised: 27 December 2019 / Accepted: 28 December 2019 / Published: 1 January 2020
(This article belongs to the Special Issue The Effects of Hypoxia on Marine Food Webs and Ecosystems)
Several hypotheses of how zooplankton communities respond to coastal hypoxia have been put forward in the literature over the past few decades. We explored three of those that are focused on how zooplankton composition or biomass is affected by seasonal hypoxia using data collected over two summers in Hood Canal, a seasonally-hypoxic sub-basin of Puget Sound, Washington. We conducted hydrographic profiles and zooplankton net tows at four stations, from a region in the south that annually experiences moderate hypoxia to a region in the north where oxygen remains above hypoxic levels. The specific hypotheses tested were that low oxygen leads to: (1) increased dominance of gelatinous relative to crustacean zooplankton, (2) increased dominance of cyclopoid copepods relative to calanoid copepods, and (3) overall decreased zooplankton abundance and biomass at hypoxic sites compared to where oxygen levels are high. Additionally, we examined whether the temporal stability of community structure was decreased by hypoxia. We found evidence of a shift toward more gelatinous zooplankton and lower total zooplankton abundance and biomass at hypoxic sites, but no clear increase in the dominance of cyclopoid relative to calanoid copepods. We also found the lowest variance in community structure at the most hypoxic site, in contrast to our prediction. Hypoxia can fundamentally alter marine ecosystems, but the impacts differ among systems.
Keywords: Puget Sound; Hood Canal; oxygen; copepods; gelatinous zooplankton; community structure; cyclopoids; calanoids; diversity Puget Sound; Hood Canal; oxygen; copepods; gelatinous zooplankton; community structure; cyclopoids; calanoids; diversity
MDPI and ACS Style

Keister, J.E.; Winans, A.K.; Herrmann, B. Zooplankton Community Response to Seasonal Hypoxia: A Test of Three Hypotheses. Diversity 2020, 12, 21.

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