| Summary: | Prediction of the impact of global climate change on marine phytoplankton is fraughtwith uncertainties. A range of environmental changes will influence phytoplankton,including warming, enhanced stratification, alteration of ocean currents,intensification or weakening of local nutrient upwelling, heavy precipitation, andstorm events causing changes in land runoff and micronutrient availability. Further,elevated CO2 could directly reduce calcification through ocean acidification, but alsostimulate photosynthesis or other biogeochemical processes such as N-fixation.Phytoplankton responses are likely to be species- or even strain-specific. Complexfactor interactions exist and simulated ecophysiological laboratory experiments rarelyallow for sufficient acclimation or take into account physiological plasticity andgenetic strain diversity. In the absence of multi-decadal Australian datasets to assessdirectly impacts of climate change, we must use appropriate datasets from otherlocations, look to the geological record for past responses to climate, and examine theresponse of phytoplankton to climate forcing over shorter time scales (e.g. El Nio-Southern Oscillation). Given documented changes in Australia and other parts of theworld, we can expect: (1) range expansion of warm-water species at the expense ofcold-water species, which are driven polewards; (2) changes in the abundance andseasonal window of growth of selected phytoplankton species; (3) earlier timing ofpeak production of phytoplankton, especially in temperate regions; (4) Knock-oneffects for marine food webs, notably when individual zooplankton and fish grazersare differentially impacted (match-mismatch) by climate change. Some harmfulalgal bloom phenomena (e.g. toxic dinoflagellates benefitting from land runoff and/orwater column stratification, tropical benthic dinoflagellates responding to warmerwater temperatures and coral reef disturbance) may become worse, while others maydiminish in areas currently impacted. Greatest problems for human society will becaused by being unprepared for significant range expansions or the increase of algalbiotoxin problems in currently poorly monitored areas. We thus require increasedvigilance in seafood biotoxin and algal monitoring programmes and the IntegratedMarine Observing System (IMOS) are contributing significantly to these efforts. Acombination of laboratory and field approaches over multiple spatial and temporalscales is necessary to better predict climate impacts on phytoplankton.
|
|---|