Biological responses to environmental stresses
(hypoxia and acidification)
Puget Sound Oceanography
2011
Climate projections
Ocean
Atmospheric
‘Business as usual’
With emissions mitigation
pH along St. George California transect
Feely et al., 2002
Calcium carbonate (as aragonite) saturation depths: from 1991-1996 cruises.
Feely et al., 2002
February 2008
August 2008
Brittlestar adults increase calcification
Oysters – decreased growth and calcification
Wood et al, 2008
3500ppm
Net calcification
380ppm
Calcium content (g)
Beniash et al, 2010
Pteropod – shell dissolution
Control
Deformed
Limacina
7.4
Normal
CaCO3 precipitated
Krill – deformed eggs, reduced hatching
pH
7.7
Control
low pH
Sea urchins –
deformed larvae
pH 8.1
pH 7.8
Kawaguchi et al, 2010
incubation time
Fabry et al, 2008
Comeau et al. 2009
Kurihara et al, 2008
Biological effects on invertebrates:
Compensation (when
present) shown to
usually come at
energetic expense.
Mean effect size
Highly variable, mostly
(but not all) negative
effects.
Doney et al, 2009
Impacts on fish?
Salmon, herring, and mackerel prey:
Changes in prey:
Lab experiments: low pH affects sensory systems;
changes behavior:
Leads to mortality in
the field :
Hypoxia
Primary effects:
• mortality
• physiological stress / impaired abilities
• increased/decreased metabolic functions
Secondary effects:
• habitat loss
• decreased prey abundance
• changes in predation / predation risk
Field observations of fish
distributions –
low abundances in hypoxic
water
Vertical distributions of fish and some zooplankton change in
response to hypoxia:
May (oxic bottom water)
Fish abundance
Depth
Fish abundance
(Copepods)
Fish abundance
August (hypoxic bottom water)
Depth
Fish abundance
(Copepods)
(Copepods)
Stanley and Wilson, 2004
(Copepods)
Roman, 1993
Benthos
Hypoxic ------------------------------------------------------------------------Oxic water column
Diaz and Rosenberg (1995)
What drives changes in distributions?
•
•
•
•
Avoidance?
Direct mortality?
Indirect mortality (e.g., predation)?
Population-level changes (growth, reproduction)?
High mortality in hypoxic water.
Species-specific thresholds
copepods
Roman (1993)
episodic vs. chronic
Avoidance:
Behavioral trade-offs: Habitat preference vs. predation risk
Fish larvae avoid hypoxia, increasing overlap with predators
Treatment:
Without Striped Bass Oxygen (mg/l)
2
4
6
predators predators
Pycnocline
Predator
avoidance
Without Striped Bass Oxygen (mg/l)
predators predators
2
4
6
Pycnocline
Effects of hypoxia depend on species:
Physiology:
Dissolved oxygen (mg/l)
Predation
rates:
# of prey eaten
Dissolved oxygen (mg/l)
Breitburg 1994
Vertical movement of Aurelia under five oxygen conditions
“Normal”
Lots of vertical movement
Each coloured line is the track of
an individual specimen over a 1 h
period.
Thuesen et al. J Exp Biol 2005
Multiple stressors:
Habitat squeeze: high temperatures and low dissolved
oxygen
Dissolved Oxygen
<5mg/l=stress
<3mg/l=mortality
Water temperature
>25C =
stress and
mortality
August 18-20, 2003
Courtesy E. North, UMD, HPL
Main Stem Hood Canal oxygen patterns:
Ocean end
Hoodsport
Hood Canal oxygen and density profiles:
Bioacoustic surveys
Hoodsport, September 2006
Night
Day
0
0
5
10
15 0
0
20
20
40
40
60
60
80
80
100
100
120
120
140
140
20 5
10
15
20
Surface zooplankton
layer
Fish separated
from their prey