Anthropogenic nutrients and harmful algae in coastal waters

Abstract

Harmful algal blooms (HABs) are thought to be increasing in coastal waters worldwide. Anthropogenic nutrient enrichment has been proposed as a principal causative factor of this increase through elevated inorganic and/or organic nutrient concentrations and modified nutrient ratios. We assess: 1) the level of understanding of the link between the amount, form and ratio of anthropogenic nutrients and HABs; 2) the evidence for a link between anthropogenically generated HABs and negative impacts on human health; and 3) the economic implications of anthropogenic nutrient/HAB interactions. We demonstrate that an anthropogenic nutrient-HAB link is far from universal, and where it has been demonstrated, it is most frequently associated with high biomass rather than low biomass (biotoxin producing) HABs. While organic nutrients have been shown to support the growth of a range of HAB species, insufficient evidence exists to clearly establish if these nutrients specifically promote the growth of harmful species in preference to benign ones, or if/how they influence toxicity of harmful species. We conclude that the role of anthropogenic nutrients in promoting HABs is site-specific, with hydrodynamic processes often determining whether blooms occur. We also find a lack of evidence of widespread significant adverse health impacts from anthropogenic nutrient-generated HABs, although this may be partly due to a lack of human/animal health and HAB monitoring. Detailed economic evaluation and cost/benefit analysis of the impact of anthropogenically generated HABs, or nutrient reduction schemes to alleviate them, is also frequently lacking.

Potentially harmful microalgae and algal blooms in a eutrophic estuary in Turkey

“…Significant deviations from the Redfield ratio indicated that this area had a highly variable concentration of nitrogen and phosphorus. A recent study clearly highlights the variations of Redfield ratios as associated with anthropogenic nutrient, yet it questions the role of this ratio in the occurrence of harmful algal blooms (HABs) (Davidson et al, 2014). Dissolved silicate concentrations were generally high and adequate for supporting the diatom proliferation.…”

Marine cage culture and the environment: effects on water quality and primary production

“…Similar to other algae species, the nutrient fluxes that influence HAB population dynamics are complex and vary for different species (Anderson et al 2002, 2008, Vargo 2009, Lewitus et al 2012, Iriarte et al 2013, Davidson et al 2014. Environmental factors other than nutrient loading also contribute to the formation of HABs.…”

Nitrogen dynamics and phytoplankton community structure: the role of organic nutrients

“…Although it is increasingly clear that DON serves as an N source for both bacteria and phytoplankton (Antia et al 1991;Bronk et al 2007;Lønborg et al 2009b;Pete et al 2010), there is little information on the relative utilisation of different forms of inorganic and organic N over an annual cycle or possible links to phytoplankton community composition (Glibert et al 1982a(Glibert et al , 2016 and references therein, Davidson et al 2014Davidson et al , 2012.…”