Optical Tools for HAB Detection

Optical Detection and Characterization of Pre-HAB Populations of the Fish-killing Alga, Heterosigma akashiwo

Researchers created new imaging technology for monitoring harmful Alexandrium and Heterosigma algae, and developed a new model for predicting when and where Heterosigma will form HABs.

Principal Investigator

Daniel Grünbaum, University of Washington, School of Oceanography


Washington Sea Grant-funded researchers developed and deployed high-resolution, low-cost, low-power micro-imaging technology using embedded computers and high-definition cameras to detect, quantify, and characterize swimming algal cells. The imagers can work autonomously, storing data onboard, or be integrated into sensor networks, streaming real-time data to an online server.

Research Updates


The toxic algae Heterosigma and Alexandrium are common and costly sources of harmful algal blooms (HABs) in Puget Sound. Alexandrium is a toxin that can accumulate in shellfish and cause paralytic shellfish poisoning in humans and other animals. Heterosigma is a microscopic raphidophyte that relies upon its vigorous swimming ability to aggregate into toxic blooms that kill fish and other marine life.


In field tests, prototype imagers distinguished Alexandrium chains and quantified their abundance and swimming velocities. They enabled the team to publish new observations of Heterosigma cells emerging from sediment to water column. When conditions became supportive, resting cells could emerge and divide within hours, suggesting a tradeoff between swimming speed and efficient transition to the water column, both of which are metabolically demanding. The research team developed a numerical model based on this tradeoff that predicts the conditions under which different Heterosigma strains are likely to dominate HAB populations as well as conditions under which no strains will likely bloom.


Chan KYK (2012) Biomechanics of larval morphology affect swimming: insights from the sand dollars (Dendraster excentricus). Integrative and Comparative Biology, 54(2):458-469.

Chan KYK, Clay TW, Grünbaum D (2012) Physical constraints on larval swimming and their implications for dispersal. Integrative and Comparative Biology, 52:27.

Chan KYK, Grünbaum D, Arnberg M, Thorndyke M, Dupont ST (2012) Ocean acidification induces budding in larval sea urchins. Marine Biology, 160:2129-2135

Chan KYK, Yang S, Maliska ME, Grünbaum D (2012) An interdisciplinary, guided inquiry on estuarine transport using a computer model in high school classrooms. American Biology Teacher. 74(1):26-33.

Durkin CA, Bender SJ, Chan KYK, Gaessner K, Grünbaum D, Armbrust EV (2013) Silicic acid supplied to coastal diatom communities influences cellular silicification and the potential export of carbon. Limnology and Oceanography, 58(5):1707-1726.

Hall, R (2010) Washington researchers develop device to predict harmful algal blooms. Aquaculture North America, May/June 2010:20-21.

Tobin E (2012) In Science, words matter. Los Angeles Times, 2 April.

Tobin ED, Grünbaum D, Patterson J, Cattolico RA (2013) Behavioral and physiological changes during benthic-pelagic transition in the harmful alga, Heterosigma akashiwo: potential for rapid bloom formation. PLoS One, 8(10):e76663.