Algal blooms

Abstract

In sum, while some algal blooms, such as spring blooms, are natural characteristics of many temperate and coastal waters, and critically important for food webs of marine and freshwater ecosystems, HABs are, in large part, a consequence of anthropogenic activities. HABs are increasing in frequency, magnitude, and ecological and economic effects throughout the world. Understanding of toxins, human health impacts, and the socioeconomic consequences of these blooms – to fisheries and economies – is emerging, but many questions remain unanswered, particularly as new toxins are discovered or characterized. One of the most significant factors contributing to their expansion – particularly in estuaries – is increased nutrient loading from sewage effluent, agriculture, animal operations, and aquaculture. What is clear is that the historic view of phytoplankton responses to eutrophication – increased nutrients promotes increased chlorophyll and high biomass blooms, leading to oxygen deduction and losses in habitat (e.g., Cloern, 2001) – is too simplistic for understanding how HABs respond to the major changes in nutrient loads, forms, and stoichiometry that many systems are now sustaining. Nutrient form and proportion matter and many HABs have physiological mechanisms that enable them to thrive in these environments that are being dramatically altered by human influence. Furthermore, the interplay of biology and physics is only understood at a limited scale, with much to be learned about local scales, microstructures, as well as mesoscale features. Climate changes are adding additional factors that may enhance the likelihood for blooms, and the complexity of ecosystem changes with climate changes means that much is yet to be learned about the direct and indirect effects of climate on HABs. New technologies are advancing toward improved monitoring and prediction, but many such technologies are sophisticated and expensive. Although considerable advances have been made in understanding the biology of HABs, and their interactions with other members of the community at all levels of the food web, there is still much to be learned about how and why specific species respond to specific conditions.