| Chlorinated disinfection by-products are known to be carcinogenic, mutagenic and teratogenic in drinking water. Because of these risks to human health they have been widely studied in freshwater ecosystems; however, their toxicology in coastal marine environments is not fully understood. When wastewater effluent containing residual chlorine is discharged into marine waters, bromine and chlorine species compete to react with humic matter, producing non-volatile halogenated aliphatic acids including haloacetic acids (HAAs). HAAs readily partition in water and rarely volatize back into the atmosphere because complete ionization occurs. Aquatic environments are particularly vulnerable to HAA contamination because HAAs are unlikely to sorb onto suspended solids or sediments, instead remaining available in the water column for exposure to aquatic organisms.;The objective of this research was to quantify the effects of brominated haloacetic acids in estuaries using phytoplankton as a proxy for estuarine health and productivity. Algae are a particularly good early indicator of pollutant toxicity in an ecosystem because of their high capacity for chemical uptake (due to a high surface area to volume ratio), widespread prevalence and high rate of turnover. Changes in phytoplankton abundance and availability may affect grazers that depend on these primary producers as a food source, and algal density may affect surface water quality parameters.;In and ex situ acute bioassays were completed to measure the half-maximum effective concentrations (EC50 ) for growth in both cultured and natural phytoplankton populations to quantify phytoplankton response to bromoacetic acid. Growth inhibition was estimated by changes in chlorophyll a concentrations measured by fluorometry and high performance liquid chromatography. The EC50 of bromoacetic acid on cultured phytoplankton varied little among species tested, at 194 mg l-1 for Thalassiosira pseudonana, 240 mg l-1 for Dunaliella tertiolecta and 209 mg l-1 for Rhodomonas salina. Mixed natural phytoplankton communities were more sensitive to HAA exposure with an EC50 of 80 mg l-1. Natural mixed phytoplankton communities consisting of diatoms, cryptophytes, dinoflagellates, prasinophytes, haptophytes, and green algae were more sensitive to contamination with an overall EC50 of 80 mg l-1. Discriminant analysis of algal groups suggested that bromoacetic acid additions result in an alteration of phytoplankton community structure, which may have implications to the overall population response. Although lethal to both cultured and natural phytoplankton, a two-fold EC50 decrease in mixed natural phytoplankton populations affirms the importance of field confirmation for establishing water quality criteria. |
