Use of plants for toxicity assessment of estuarine ecosystems

Estuarine ecosystems are being rapidly degraded by environmental toxicants from municipal and industrial wastes, agricultural runoff, recreational boating, shipping, and coastal development, ranking them as the most anthropogenically degraded habitat types on earth. Toxicity tests are used to establish links between adverse ecological effects and the toxicity of environmental chemicals. However, most toxicity tests used for regulating the release of chemicals into the environment have used animals as test species, with the erroneous assumption that toxicant levels protective of fish or invertebrates are also protective of plants. Most plant toxicity tests have used terrestrial crop plants, whereas the few aquatic test species used have been primarily freshwater algae. Even though estuarine and marine vascular plants are highly vulnerable to environmental chemicals, phytotoxicity studies using native coastal plants have been limited, and no such studies are required for testing by regulating agencies. The relevance of toxicity tests of estuarine sediments and of wastes entering the estuary should depend on the use of estuarine and marine plant species. This review summarizes toxicity testing of marine plants used in biomonitoring, phytotoxicity, biotransformations of toxicants, bioaccumulation, and phytoremediation. Challenges to marine plant testing are discussed and include developing standard test protocols, identifying species with minimal salinity and toxicant interaction, defining and choosing a suitable sediment for sediment-bound toxicant testing, selecting endpoints with low variability, producing viable seeds, and culturing test plants. Progress in acquiring a suitable database is being made, but at a rate that is inadequate to create the sound, scientific foundation needed for safeguarding our estuarine ecosystems in the near future.