ESTUARINE%20HYPOXIA:%20GOOD%20OR%20BAD?%20Andrew%20Altieri1,%20Jon%20Witman2,%20and%20Daniel%20Warren3%201Marine%20Science%20Center,%20Northeastern%20University%202Department%20Ecology%20and%20Evolutionary%20Biology,%20Brown%20University%203Department%20of%20Anesthesia,%20University%20of%20California%20San - PowerPoint PPT Presentation

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ESTUARINE%20HYPOXIA:%20GOOD%20OR%20BAD?%20Andrew%20Altieri1,%20Jon%20Witman2,%20and%20Daniel%20Warren3%201Marine%20Science%20Center,%20Northeastern%20University%202Department%20Ecology%20and%20Evolutionary%20Biology,%20Brown%20University%203Department%20of%20Anesthesia,%20University%20of%20California%20San

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ESTUARINE HYPOXIA: GOOD OR BAD Andrew Altieri1, Jon Witman2, and Daniel Warren3 1Marine Science Cent – PowerPoint PPT presentation

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Title: ESTUARINE%20HYPOXIA:%20GOOD%20OR%20BAD?%20Andrew%20Altieri1,%20Jon%20Witman2,%20and%20Daniel%20Warren3%201Marine%20Science%20Center,%20Northeastern%20University%202Department%20Ecology%20and%20Evolutionary%20Biology,%20Brown%20University%203Department%20of%20Anesthesia,%20University%20of%20California%20San


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ESTUARINE HYPOXIA GOOD OR BAD?Andrew Altieri1,
Jon Witman2, and Daniel Warren31Marine Science
Center, Northeastern University2Department
Ecology and Evolutionary Biology, Brown
University3Department of Anesthesia, University
of California San Francisco
2
Environmental stress reduces intensity of
predator-prey interactions(Menge Sutherland
1976, 1987)
3
Is hypoxia an environmental stress that
predictably modifies predator-prey interactions?
(Breitburg 1992, Diaz Rosenberg 1995, Rabalais
Turner 2001, Hochachka Somero 2002, Rabalais
et al. 2002, Altieri 2006, Altieri Witman 2006)
4
Study systemNarragansett Bay, RI/MA
  • Well-mixed estuary salinity 28ppt temp
    2-24C
  • Surface area 381 km2, watershed 4273 km2
    (Pilson 1985)
  • 5x nutrient increase since colonial times (Nixon
    1997)
  • Study sites soft-sediment, 3-6 m depth, 1-10 km
    apart

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Hypoxia in Narragansett Bay 2001
  • Mussel densities of up to 20,000/m2
  • 99 cover of areas up to 28 hectares
  • Mid-intertidal to 10 m depth

7
Survey mussel reefs
  • At each of 9 sites
  • Percent cover of mussels
  • Density and SF of mussel
  • Quantify seastar abundance
  • Surveys in spring and fall 2001

8
Common predators in mussel beds
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Hypoxia in the summer 2001
Periods of severe hypoxia
Spatial gradient in severity
Modified from Deacutis et al. 2006
Site TWF Site PVP
June July Aug.
Sept. Oct.
Data - Dana Kester, URI
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Beggiatoa fuzz in hypoxic areas
Dead and moribund mussels washed up on beach
13
Mussel mortality vs DO R2 0.78 P lt 0.01
(modified from Altieri Witman 2006)
14
Temporary drop in abundance of predatory stars
with hypoxia
Asterias forbesi
Mt. Tom Rock
Site June Aug./Sept. Nov.
Mt. Tom Rock 10843 41 16433
Providence Pt. 396 42 226
T-Wharf 2114 2410 3514
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Predation unimportant in mussel die-off
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Hypoxia tolerance varies among 3 bivalve spp.
  • Species specific tolerances to hypoxia
  • Mussels (2 d) lt Soft shells (7 d) lt
    Quahogs (19 d)
  • Mytilus edulis Mya
    arenaria Mercenaria mercenaria
  • Limited adjustment within species (Altieri 2006)
  • Physiological basis for differences in
    tolerances
  • Glycogen stores, pH regulation, Metabolic
    efficiency

n8 chambers/treatment 20 individuals/chamber pO2
manipulated by bubbling air or N2 Run at 22?C
summer temperature
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Hypothesis Hypoxia provides a predation refuge
  • Predation refuge for bivalves ecologically
    significant
  • Indicator species for hypoxia
  • Important prey resource
  • Filter estuary waters
  • Form living reefs for infauna
  • (Altieri Witman 2006, Lindsey
    et al. 2006)

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  • Field assay to test for hypoxia refuge
  • Softshells chosen for responsiveness
  • Clams outplanted to 4 sites
  • Two treatments, n10 baskets each
  • Caged predator exclusion hypoxia
  • Open predator access hypoxia predation
  • 8 clams per basket proportion surviving
  • Experimental runs 7 days each

19
Hypoxia provides general predation refuge
  • Refuge
  • Refuge despite
  • stress mortality
  • ? Collapse at severely
  • hypoxic sites
  • Predation resumes

20
  • 1. Hypoxia mediates predator - prey
    relationships can provide refuge
  • 2. Impact of hypoxia on community dynamics is
    predictable
  • 2a. Must consider predation and species
    specific responses

21
Acknowledgments
Environmental Protection Agency (PNB WAG) NOAA
Narragansett Bay-NERRS Rhode Island
Seagrant John G. Peterson Fellowship
(Brown) Lerner-Gray (AMNH) Sounds Conservancy
(QLF)
Emily Lindsey Carlos Rincon Jon Puritz Mihir
Parikh Marc Carrel
Mark Bertness Don Jackson Chris Deacutis Dana
Kester Kenny Raposa
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Mussel mortality vs DO R2 0.78 P lt 0.01
23
Dead Zones Baltic Sea 100,000 km2 Louisiana
shelf 27,000 km2
Do gradients of hypoxic stress have predictable
effects on predation?
Doubling of hypoxic areas and widespread Dead
zones
(Diaz 2001, Rabalais et al. 2002, UNEP 2003)
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