Ecological response to climate change

Lilian BusseScripps Institution of Oceanography

ESP seminarJune 9, 2006

Outline

• Introduction into the climate-ocean-biology relationship• Presentation of some recent studies on the biological

response to climate change • Conclusions• Concerns and uncertainties

What are the uncertainties in climate-ocean-biology relationship?

• Great uncertainty how variations in the atmosphere gets translated into variations into the ocean or land and its populations

• How will the climate change?• How will the biology react (on taxon level, on population

level, ability to recover, thresholds)?• Are there other hypotheses to explain biological

changes: habitat changes, pollution, El Nino etc.?

The ocean is warming…

McGowan et al.

…SIO is a good proxy for overall changes…

(McGowan et al. 1995)

And the possible responses of biology…

Recent studies:

North Pacific and North Atlantic, increased temperatures:• Zooplankton-CalCOFI study• Food web studies North Atlantic• Foraminifera sediment study

Entire ocean ecosystem, increased CO2:

• Ocean acidification

Plankton of the ocean

Climate change

Impact on plankton

Economic implications

Impact on fish/fisheries

Impact on food supply for humans

Zooplankton-CalCOFI study

• Roemmich & McGowan 1995 – 43 years time series from CalCOFI (1951-1993)

• Results: Decline of zooplankton by 80%, affects the foodweb (food for fish and birds)

• Link to climate change: sea surface heated T difference across thermocline increases increase of stratification less upwelling of nutrient rich water, less nutrients, less phytoplankton less zooplankton

• Conclusion: More climate change massive biological impacts?

(Roemmich & McGowan 1995)

(Roemmich & McGowan 1995)

Planktonic food webs in the North Atlantic

• Richardson and Schoemann 2004, Continuous Plankton Recorder, 1958-2002, North Atlantic, decadal and ocean basin scale

• Results: Phytoplankton becomes more abundant when cooler regions warmed, because of higher metabolic rates BUT: when warm regions become warmer, phytoplankton becomes less abundant

• Link to climate change: increased heating can enhance existing stratification, and therefore reduce nutrients to phytoplankton (in cooler water, enough turbulence, enough nutrients)

• Conclusion: Effects on plankton will affect oxygen production, carbon sequestering, and biogeochemical cycling. It will also effect fisheries.

(McGowan et al.)

Planktonic food webs in the North Atlantic

• Richardson and Edwards, 2004, marine pelagic phenology (study of annually recurring life cycle events)

• Results: since 1987 – blooms are not synchronized anymore, phytoplankton 3 weeks earlier, zooplankton only 10 days earlier

• Link to climate change: Shifts have occurred with increase in SST, physiological developments stimulated by higher temperature

• Conclusions: Impacts on ecosystem functioning and higher trophic levels (e.g. fish) possible

Edwards and Richardson (2004)

Sediment Study

• Field et al. 2006, foraminifera and ocean warming, 1,400 year time series, Santa Barbara Channel

• Results: Foraminifera were strongly affected by global warming, increase of abundance of tropical and subtropical species, decrease of subpolar species

• Link to climate change: tropical and subtropical species prefer higher SST, and deeper thermoclines

• Conclusions: lower trophic levels in the CA currents is affected by 20th century warming

(Field et al. 2006)

Ocean acidification

(Doney, 2006)

There are 3 mineral forms of calcium carbonate:-Calcite-Aragonite-Magnesium calcite

Aragonite and Magnesium calcite more soluble than calcite

Cool water and deep waters are usually undersaturated with calcite and aragoniteWarmer shallower water is oversaturated with calcite and aragonite

Ocean acidification• Doney, S.C. 2006, measurements of carbon in the ocean

from 1989 and 2005, South Atlantic to Equator• Results: pH 0.1 lower that pre-industrial times (predicted

0.3 less on 2100), some marine life has less calcium carbonate to build their shells

• Link to climate change: 1/3 of the CO2 released by fossil fuels ends up in the ocean

• Conclusion: coccolithophorids, foraminifera, snails, and corals – they move, they disappear?; cold water less saturated, polar regions suffer first acidification

The future of Aragonite

(Doney, 2006)

Conclusions

•Presented studies show that climate change has an effects on the marine organisms, populations, and food web in the pelagic ecosystem•Marine food webs are complicated and are hard to untangle

Concerns and uncertainties• “Changes in the abundance and distribution of species

of are not due to global change but due to land use changes and by natural fluctuations” → this statement ignores systematic trends we see across all ecosystems

• Statistical, model, and fundamental uncertainty → Careful science can reduce but not eliminate uncertainties → Lack of full scientific certainty is not a reason for delaying immediate response

• Length of time series- many time series are too short to detect full interdecadal cycles, spatial coverage of most studies is restricted to point sampling, diff. methods makes is difficult to combined multiple datasets- consistency across scales and systems means we should abide by the precautionary principle

References

• Doney, S.C. 2006: The dangers of ocean acidification. Scientific American, March 2006, 1-9.

• Edwards, M. & Richardson, A.J. 2004: Impact of climate change on marine pelagic phenology and trophic mismatch. Nature 430, 881-884.

• Field, D.B., Baumgartner, T.R., Charles, C.D., Ferreira-Bartrina, V., Ohman, M.D. 2006: Planktonic Foraminifera of the California Current refeldt 20th-Century warming. Science 311, 63-66.

• Richardson, A.J. & Schoeman, D.S. 2004: Climate impact on Plankton Ecosystems in the North East Atlantic. Science 305, 1609-1612.

• Roemmich, D. & McGowan, J. 2003: Climatic Warming and the Decline of Zooplankton in the California Current. Science 267, 1324-1326.