Integration of microscopy and underway chlorophyll mapping for monitoring algal bloom development

Phytoplankton communities are constantly changing with variable spatial distributions and shifting species composition in response to numerous biological and abiotic fluctuations. The most dynamic response is the formation of algal blooms; when a taxon is able to take advantage of a particular set of conditions, and quickly grow in numbers to become dominant in the algal community. Some blooms can be associated with negative impacts on the rest of the aquatic community, and may even cause human health concerns in the case of toxin production. Due to the transient nature of plankton, monitoring of algal blooms and the phytoplankton community in general is difficult, and often accomplished using a network of fixed stations, which may be limited in their spatial coverage of these events. Alternatively, higher throughput data such as the measurement of chlorophyll a, can deliver a larger spatial and temporal area, but not provide information on species composition vital for describing the biology and potential health impacts associated with certain taxa. This paper describes the use of a hybrid approach integrating continual chlorophyll measurements over a large area along with the collection of water samples for microscopic analysis. The Dataflow system and taxonomic identifications were used in conjunction during 2011 and 2012 to monitor algal blooms on the James River, Virginia, USA. During this time, the region experienced significant blooms of a variety of dinoflagellates, most notably Cochlodinium polykrikoides and Heterocapsa triquetra. Using these methods allowed for high resolution description of the initiation, transport, expansion, and subsidence of multiple algal blooms within the tributary, including the impact of tropical storms which occurred in 2011. This technique shows potential for providing research scientists, managers and modelers with the quality and quantity of data necessary to address questions relating to river-wide quantities of algal compos- tion and abundance and could be applicable to other water bodies, including coastal systems.