The Experimental Study On The Toxicity Of Karenia Mikimotoi To Marine Animals

The toxicity of a Karenia mikimotoi strain was investigated in this paper. Its acute effects on Brachionus plicatilus, Artemia salina, Argopecten irradians Lamarck, Chlamys farreri and Neomysis awatschensis and the chronic effects on N. awatschensis were studied.The results showed that the population of B. plicatilis was significantly decreased when exposed to K. mikimotoi at low densities (<80cells/mL) and the 24hEC50 was about 20cells/mL. The toxicity comparison of different algal fractions showed that the algal culture and re-suspended algal cells had the adverse effects, while the broken cells and filtrate showed little impact. When direct contact of K. mikimotoi cells and rotifers was interrupted with a cell-impermeable membrane, the toxic effects completely disappeared. The results indicating that the inhibitory effect was mainly related to the cell-mediated attacks.The results of ingesting experiment showed that A. salina could prey K. mikimotoi, but the survival of A. salina was significantly decreased when exposed to K. mikimotoi.The effects on early development of A. irradians and C. farreri exposed to the alga K. mikimotoi were also performed. It was found that the algal culture could inhibit the swimming activity of D-shaped larvae and decreased the survival rate of eye-spot larvae of A. irradians, but showed no adverse effects on of A. irradians, the egg hatching success and the survival of D-shaped larvae of C. farreri.K. mikimotoi could affect the survival and reproduction of N. awatschensis, and the effects increased with the algal concentration. In acute experiment (16d), the survival rate was significantly decreased when exposed to algal concentration of 15,000cells/mL. Chronic experiment (73 days) showed that K. mikimotoi could affect the total juvenile population of N. awatschensis. The total numbers of juveniles produced were only 237, 226 and 11 in algal concentrations of 500, 2500, 5000 cells/mL, respectively, while 252 juveniles were released in the control group during the same period. In concentration of 500, 2500 and 5000 cells/mL, the first releasing day was prolonged for 8, 8, 25 days compared with that of the control. It was also found that K. mikimotoi can affect the survival of the adult mysid: in 5000 cells/mL of K. mikimotoi, the survival rate of N. awatschensis was only 37.8% of that of the control.K. mikimotoi showed no adverse effects on the survival of juvenile Scophthalmus maximus and Paralichthys olivaceus during the test time.During the blooms in which the densities of K. mikimotoi reach 1,000cells/mL, some sensitive zooplanktons or the sensitive phases of marine animals will die. That will affect the structure of marine ecosystem.