Measuring Viability of the Red-Tide Dinoflagellate Lingulodinium polyedra Following Treatment with Ultraviolet (UV) Light

Harmful algae blooms (HABs) have caused millions dollars in annual losses to the aquaculture industry, inhibited beach recreation, and have threatened marine and human health. HABs and red tides can develop suddenly and their frequency, geographic range, and intensity have increased over the past decade. A possible source for spreading and seeding new areas expanding the geographic range of HABs is ballast water. The process of ballast water discharge has been identified as a primary vector for the translocation of non-indigenous species (NIS) and invasive species. National and international efforts are currently underway to address the impact of NIS and invasive species. Policy is being developed detailing stringent rules to kill, remove, or otherwise inactive organisms in ballast water prior to or upon discharge. Currently, vendors are developing technologies to treat ballast water and U.S. and international facilities are testing these technologies to verify their efficacy. Ultraviolet (UV) radiation is commonly employed in ballast water treatment technologies. Previous studies have shown that UV light is effective for disinfecting drinking water, but the response of non-pathogenic and marine organisms is largely unknown. The purpose of this research was to measure the viability of the durable red-tide forming dinoflagellate, Lingulodinium polyedra following UV treatment. Two methods were used to measure the viability signal; manual epifluorescence microscopy with correlated viability stains and Pulse Amplitude Modulated (PAM) fluorometry to measure the physiological state of the organism following UV treatment. The number of cysts was also enumerated. The results showed that there was a significant decrease in the number of living L. polyedra cells following a UV treatment of more than 100 mWs cm-2. The results also have showed a significant increase in the number of L. polyedra cysts following UV treatment as low as 50 mWs cm-2