Toxicity of Ammonia on Fertilization, Development, and Larval Survival of the Northern Pacific Asteroid, Asterias amurensis

Abstract

Ammonia originates from various sources including dead organisms, sewage, industrial and domestic wastes, fertilizers. Since ammonia is reduced form, the concentration is not so high as to affect adversely the marine organisms in pelagic environments. But, in benthic systems, in which only a few millimeter of surface sediments was oxygenated, ammonia can be accumulated in pore water. High concentration of ammonia was frequently found in some locations where the content of organic matter was high. In many cases, marine sediments with highly contaminated by toxic metals or persistent organic pollutants has also high concentration of ammonia; this often confounded the extents and the sources of toxicity of sediments. Therefore, to discriminate the toxic effects of industrial chemicals other than ammonia, it is necessary to quantify the toxicity of ammonia on marine organisms. Naturally ammonia exists in either ionized ammonium (NH4+) or un-ionized ammonia (NH3); the latter is more toxic than the former. Here, the purpose of this study was established to know the quantitative effects of un-ionized ammonia on fertilization, development, and larval survival of the starfish, Asterias amurensis. Fertilization and developmental bioassays were conducted based on the standard protocol for echinoids by the USEPA (1995). Acute toxicity tests with bippinaria larvae were conducted for 24, 48, 72, and 96 hrs. Median effective concentration (EC50) or median lethal concentration (LC50) were estimated to evaluate the toxicity of ammonia quantitatively. The EC50s for fertilization and development was estimated to be 155 mg/L and 95 mg/L, respectively. The embryo of A. amurensis was more sensitive to ammonia than the sperm. As compared to the sensitivity of sea urchin, which have been most commonly used in pore water toxicity tests, fertilization bioassay with A. amurensis is more sensitive than that with Arbacia punctulata; developmental bioassay with A. amurensis is comparable to th