Climate Change, Phytoplankton, and HABs

Abstract

Planktonic microalgae, or phytoplankton, are quantitatively the most important primary producers supporting estuarine and coastal food webs. Because they exhibit fast growth and reproductive rates, they are highly sensitive and susceptible to environmental changes, including anthropogenic nutrient over-enrichment, and altered physical–chemical drivers brought about by climate change. As such, they are the “canaries in the mine,” rapidly responding to these changes, and serving as sensitive, quantifiable indicators of biogeochemical and trophic alterations at the community to ecosystem scales. With regard to climate change, phytoplankton community structure and function are readily impacted and altered by temperature, either directly by affecting group-specific growth rates, or indirectly by responding to changes in water column stratification. Another major component of climate change, altered patterns and amounts of precipitation, and resultant changes in freshwater discharge, flushing rates, salinity, and nutrient supply regimes can profoundly alter phytoplankton community dynamics, with cascading effects on food webs, biogeochemical cycling, and water and habitat quality; in particular, the development and proliferation of opportunistic harmful (toxic, hypoxia-generating and food web altering) bloom-forming algal taxa (HABs) problematic cyanobacteria, dinoflagellates, and other algal groups. Climatic drivers and changes therein strongly interact with other man-induced stressors, including nutrient and organic matter enrichment, xenobiotic pollutants and hydrologic modifications, the creation of dams, impoundments, and water withdrawal for irrigation and human consumption. A major challenge with regard to understanding the underlying processes and managing phytoplankton dynamics is distinguishing and accounting for the synergistic and antagonistic interactions and impact of these drivers, i.e., what is manageable and what is not? – as we further enter an increasingly complex and challenging Anthropocene. Finally, we will need to address and manage changing nutrient (nitrogen and phosphorus), hydrologic, and temperature thresholds, especially as they pertain to mitigating a global proliferation of HABs.

Topics & Concepts