Metabolic Constraints on Marine Habitat and its Climatic Changes Curtis Deutsch University of California, Los Angeles In collaboration with: Aaron Ferrel, Taka Ito, Hartmut Frenzel And funded by:
Jan 01, 2016
Metabolic Constraints on Marine Habitat
and its Climatic Changes
Curtis DeutschUniversity of California, Los Angeles
In collaboration with: Aaron Ferrel, Taka Ito, Hartmut Frenzel
And funded by:
Oxygen and marine ecosystems
Low O2 restricts habitat of aerobic macrofauna. - anaerobic metabolism - mortality
2) Microbes (biogeochemistry)
NO
2 (m
ol/li
ter)
0 2 4 6 8 10 12 14 16 18
O2 ()
1) Macrofauna (ecology)1.0
0.8
0.6
0.4
0.2
0
Fra
ctio
n S
peci
es H
abita
bilit
y
50% lethalityO2~ 50 M “Hypoxia”
O2 ()0 60 120 180 240 300
Vacquer-Sunyer and Duarte [2008] Devol [1978]
Low O2 creates habitat for anaerobic microbes. - denitrification, annamox - widespread N limitation
Onset of denitrificationO2~ 5 M “Suboxia”
Biogeochemical ChangesO
2 cy
cle
N c
ycle
Simulations (GCM) Observations (CalCOFI)
Deutsch et al. [2011]
log(VO2/VO2)
Hypoxic sensitivity
€
VO2 =∂VO2
∂O2crit ΔO 2 The sensitivity of
hypoxic volumes can be predicted from data alone.
It increases rapidly with decreasing O2 threshold.
Model simulations (dots) consistent with this simple prediction.
Global O2 anomaly(assumed)
Derivative of histogram(observed)
Change in volume(predicted)
100%
30%10%
300%
Normalized change in hypoxic volume (VO2/VO2)
Deutsch et al. [2011]
Goals of this Study
Question:
How does climate warming change the aerobic habitat of marine species?
Strategy:
Integrate laboratory, demographic, and climate data to map the metabolic scope of diverse marine species across their geographic range.
A General Framework
€
Φ =O2 Supply
O2 Demand= Ao *
[O2 ]
B 3/4 exp(−Eo /kBT )
Gas Transfer
Metabolic Rate
Ferrel and Deutsch [in review]
Problem: Index depends (invisibly) on many physiological factors. Solution: Estimate coefficients (Eo, Ao) using laboratory data.
Alternate interpretation: Φ is the ratio of potential metabolic rate to minimum rate for survival, i.e. a non-dimensional measure of metabolic scope [Fry, 1947; Hochachka, 1990].
Laboratory dataUse published laboratory experiments on hypoxic tolerance (O2
crit) measured as onset of anaerobic metabolism and increased mortality (LC50)
Φ(O2crit) = 1
Estimate parametersAo (intercept)Eo (slope)
Mass and temperature account for ~70% of variance.
Ferrel and Deutsch [in review]
Problem: Laboratory tanks are not the real world!Solution: Map Φ alongside species distribution data.
Φ =1.6
Distribution data: Cod
Cod Characteristics:
Depth of habitat0-400m
Mass at maturity500-1500g
Range of Φcrit
1.3-2.6
Φ =1.6
Western PopulationMigrates From ~37oN in winterTo ~41oN in summer
Eastern PopulationMigrates Surface in spring/winterTo ~250 m in summer/fall
Seasonal Migration
Annual PopulationsAnnual Populations
Φmax=2.4 Φmin=2.4
Seasonal populations
Annual populations
Species Distribution: Rock Crab
Crab Characteristics:
Depth of habitat0-400m (benthic)
Mass (larval)1.25-5 x10-4
Range of Φcrit
1.8-4.1
Φ =2.2
Species Distribution: Seabream
Seabream Characteristics:
Depth of habitat0-60m
Mass at maturity300-900g
Range of Φcrit
1.6-4.0
Φ =1.9
Species Distribution: Eelpout
Eelpout Characteristics:
Depth of habitat0-40m
Mass at maturity100-300g
Range of Φcrit
1.4-3.3
Comparison to Terrestrial Taxa
Peterson, Nagy, Diamond [1990]
Ratio of Field to Resting Metabolic Rates:
Birds, mammals, lizards 1.5-5 (max 7)
Marine fish/crabs 1.3-4.1 (1.6-2.4)
Humans 1.4-5.6
A B
T (oC) O2 (M)
Climate ProjectionsProjected T, O2 changes in 2071-2100, 0-400m
IPCC Earth System Model mean, RCP8.5 scenario
Warming is global, deoxygenation is extra-tropical.
Declining Metabolic IndexProjected change in Φ in 2071-2100, 0-400m
IPCC Earth System Model mean, RCP8.5 scenario
Global meanDecrease ~20%
Northern High Latitudes ~40%
Φ %) Φ %)
A B
Temperature vs OxygenOxygen contribution Temperature contribution
Globally, warming and deoxygenation contribute ~15% and 5% reduction of metabolic index, respectively. The role of O2 is greater in the Pacific, where O2 is already lower.
Habitat Loss
Habitat Loss(slope, annual)
Metabolic Habitat Loss
Cod-24%
Seabream-14%
Eelpout-26%
Rock Crab-22%
Relative change in habitable thickness (%)
Integrated Habitat Loss
Loss of metabolic habitat is generally greater than theloss of thermal habitat (Tmax), but not always.
The loss of O2 contributes ~25% of the metabolic habitat loss. Its role in the Pacific is likely to be even greater.
Conclusions– The ratio of O2 supply to demand - an index of metabolic
scope – can be mapped using laboratory, demographic, and climate data.
– Species with diverse thermal and hypoxic tolerances are limited at the equatorward edge of their geographic range by a similar metabolic scope, consistent with that of terrestrial taxa.
– Metabolic habitat is projected to contract rapidly due to the synergistic impacts of anthropogenic warming (~75%) and the associated loss of oxygen (~25%).
Figure S5A
B C
A
B
Changes in Metabolic Index