Harmful algal blooms (HABs) – stories from two oceans, future projections and management
Professor Anna Godhe, Department of Marine Sciences, University of Gothenburg, Sweden
Dr Andrew Turner, Principal Chemist, Cefas Food Safety Group, Cefas, Weymouth
Friday 11 May 2018
Phytoplankton form the base of the marine food chain and are responsible for 50% of the CO2 fixation on Earth. However, a few species of algae are harmful in the sense that they produce toxins which sometimes kill marine invertebrates, fishes and mammals. Algal toxins are also known to accumulate in bivalves, and human consumption of such toxic bivalves may be fatal. One prominent group of toxin-producing microalgae are dinoflagellates. We have explored a long-term monitoring series from the eastern Arabian Sea and recorded that during ENSO (El Niño Southern Oscillation) periods the sea surface water temperature increases and the stratification of the water column intensifies. These hydrographic conditions coincide with higher abundances of dinoflagellates.
During the most recent ENSO event in 2016, the same area was exposed to a large outbreak of ciguatera fish poisoning, which is caused by yet another dinoflagellate toxin which accumulates in fish. Hence, global warming is hypothetically favourable for dinoflagellates at the expense of other phytoplankton groups, and we might have to consider an increase in HABs. We have also further explored the effects of such blooms by looking at the next trophic level and investigated how toxin accumulation in bivalves, and bivalve health will be effected under climate change conditions.