Harmful algal blooms and climate change: Preparing to forecast the future

The central findings of an international workshop organized by PICES and GEOHAB were that while there are reasons to expect HABs to increase with climate change, poor scientific understanding seriously limits forecasts, and current research strategies will not likely improve this capacity.

The impacts of algal blooms are extensive. Although phytoplankton blooms normally fuel productive ecosystems, some blooms create very low oxygen concentrations in bottom waters, killing or driving out marine fish or benthic organisms. Others produce potent neurotoxins that threaten ecosystems and human health.

Evidence suggests that these destructive blooms, called red tides in the past but more properly "harmful" algal blooms, are increasing in frequency and severity, possibly from human causes.

The combined effects of increasing temperature and atmospheric CO2 are affecting ocean surface temperatures, nutrients, light, and ocean water acidity, all of which affect marine ecosystems. These factors influence not just the intensity of algal blooms but also their composition. The question is whether climate change will enable harmful species to outcompete other phytoplankton.

The challenge is that the mechanisms driving the development of most HABs are only partially understood. The workshop participants developed several urgent recommendations on research priorities. These include re-orientating research to study how harmful species interact in planktonic communities, focus more intensive study on key organisms, emphasize developing ecological and forecast models, and strengthen linkages among global, national and regional observation programs.

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