Relevance

Relevance to the objectives of the Global Change and Ecosystems Sub-Priority

Harmful algal blooms (HABs) are generically either high biomass blooms (exceptional blooms, or red tides) or blooms of species which contain toxins. Some HABs derive from anthropogenic activity, notably through eutrophication or through global dispersion of species through transport systems (ballast water). Most HABs are, however, naturally occurring phenomena and records of HAB events date back centuries.

HABIT is a clear attempt to put the existence of HABs in an oceanographic context. Whether the origin of a HAB is anthropogenic or not, the behaviour of the planktonic species involved is very often in a sub-surface thin layer. Many exceptional or high biomass blooms visible at the surface derive from accumulations of cells beneath the sea surface, a notable example being Karenia mikimotoi.

By studying both the physical and biological interactions involved in maintaining thin layers, HABIT clearly addresses the following strategic objectives:

• to understand and minimise the negative impacts of human activities on marine ecosystem functioning
• to develop a better understanding of marine ecosystem functioning
• to describe and quantify cause effect relationships between harmful algal bloom formation and natural and anthropogenic forcings

Results from the programme will also equip environmental managers with a priori information allowing the optimisation of the sustainable management of natural resources (aquaculture) and with mitigation options through the prediction of HAB events.

Technical Relevance

Harmful algal blooms have negative impacts on water quality, aquatic ecosystems and public health. The potential to forecast HAB events at the coast has increased substantially with the development of operational oceanography. Achievement of the objectives of HABIT allows the use of important behavioural aspects of HAB species, i.e. the formation and persistence of high density sub-surface layers, with physical models to improve our prediction ability.

Relevance to Policy

The debate continues as to the relative contributions of anthropogenic, climatic and natural causes for the apparent increase in HAB events. It is now recognised by the scientific community that their relative importance depends largely on the hydrodynamic regime of the coastal ocean. Identification of the origins of HAB events are essential to policy makers since the only mitigation action possible lies in their prediction if these are naturally occurring.