The Influence of Aerosols on Harmful Algal Toxin Production and Maintenance

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The primary objective of this study is to determine what aerosol events (desert dust storms, volcanic eruptions, fires) or pathways contribute to the propagation of harmful algal toxins. This study provides insight into what type of aerosol events contribute to harmful algal blooms.


Numerous brown blobs on a tan background marked with an uneven grid

Figure 1. The above image illustrates counting Karenia brevis cells using a hemocytometer. (Credit: Sarah Shedler, USGS. Public domain.)

Toxic algal blooms, frequently noted as harmful algal blooms (HABs) are believed to be initiated and maintained through the uptake and recycling of atmospheric nutrient sources (desert dust, volcanic ash and fire ash) in Florida’s various freshwater, brackish water, and marine-aquatic ecosystems (Lenes and others, 2001; Griffin and others, 2004; Lenes and others, 2008). While extensive discharges from riverine sources throughout and in close proximity to brackish and marine ecosystems occur annually, the marine ecosystems are typically devoid of nutrients and the influence of aerosolized nutrients originating from local and distal sources is comparatively unknown. The coastal and inland freshwater lakes and rivers present an ideal location to study the influences of aerosols in bloom propagation and stability. In this study we will investigate the influence of individual and combined nutrient sources on toxin production due to freshwater HAB species and the red-tide agent Karenia brevis. In addition, we will investigate the influence of these sources on the cyanobacterium Trichodesmium which are believed to be intricately associated with Karenia brevis blooms due to the deposition of African dust on regional surface waters as well as riverine transport of land-based sources of nutrients (Lenes and others, 2008).

This study will expand an ongoing freshwater HABs (Microcystis aeruginosa and an Anabaena species) aerosol fertilization study where the influences of desert dust and volcanic ash are being investigated to determine their role in HAB toxin production using microcosm-based experiments. In this proposed study we will culture our various species of HABs and acquire aerosol material from existing USGS archives and new dust events. In short, microcosm experiments will consist of spiked cultures and non-spiked controls that will be monitored over time. Analyses will include source material geochemistry and water chemistry, phytoplankton abundance (microscopic and quantitative-polymerase chain reaction), toxin production, morphological change and 16S microbial diversity based on sequencing of the 16S gene.

These data will provide insight into the initiation and maintenance of HABs on the West Florida Shelf (WFS) and the magnitude of the influence these aeolian sources have on HABs. Further, these data will provide an understanding of the transition of HABs to toxic algae, and the role the local and distal sources have on potential risks to fisheries, human and economic health.

Potential Management Implications

It is currently unknown what role these atmospheric nutrient sources and natural processes may play in bloom dynamics and toxin production. If a natural phenomenon such as aerosol deposition is driving bloom proliferation/toxin production, it is important to know the relative impact compared with anthropogenic drivers. It is also crucial to better understand if other mitigation efforts on the reduction of anthropogenic N and P reduction can be successful as a short- and/or long-term mitigation strategy when deposition events have occurred. A better understanding of these processes can perhaps allow us to better manage our environmental sustainability coupled with appropriate and more full natural resource utilization. While volcanic eruptions and desert dust storms cannot be controlled, forest ecosystems and recovery after fires can be managed. Additionally, impact zones from ash deposition can be predicted to better understand impact areas on algal blooms and toxin production if and when they occur, to provide earlier warning of events as better understanding is achieved.

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References Cited

Griffin, D.W., and Kellogg, C.A., 2004, Dust Storms and their impact on ocean and human health: Dust in Earth’s atmosphere: EcoHealth 1, 284–295

Lenes, J.M., Darrow, B.P., Cattrall, C., Heil, C.A., Callahan, M., Vargo, G.A., Byrne, R.H., Prospero, J.M., Bates, D.E., Fanning, K.A., and Walsh, J.J., 2001, Iron fertilization and the Trichodesmium response on the West Florida shelf: Limnology and Oceanography,

Lenes, J.M., Darrow, B.A., Walsh, J.J., Prospero, J.M., He, R., Weisberg, R.H., Vargo, G.A., and Heil, C.A., 2008, Saharan dust and phosphatic fidelity: A three-dimensional biogeochemical model of Trichodesmium as a nutrient source for red tides on the West Florida Shelf: Continental Shelf Research,