Effects of red-tide and toxic dinoflagellates on the survival and growth of larvae of the mussel, Mytilus galloprovincialis

Abstract

There were many studies on the effects of red tide dinoflagellates on shellfish populations (Nielsen and Strømgren, 1991; Lesser and Shumway, 1993; Luckenbach et al., 1993; Matsuyama et al., 1997; Li et al., 2001). However, these studies mainly focused on the toxic effects of dinoflagellates on adults or juveniles. Interactions between dinoflagellates and bivalve larvae have not been understood comprehensively yet. Thus, the purpose of this study was established to know the effects of red tide dinoflagellates (Amphidinium carterae, Prorocentrum triestinum, Gymnodinium impudicum, and Akashiwo sanguinea on the survival and growth of the larvae of the mussel, Mytilus galloprovincialis.The survivals of M. galloprovincialis larvae in no food and I. galbana treatments after 10 days were 100%. But, some of larvae died in treatments with red tide and toxic dinoflagellates. The survival of larvae was higher than 90% when the food was either A. carterae (p=0.153) or A. sanguinea (p=0.630). The lowest survival (20%) was found when the food was P. triestinum (p<0.001). In the P. triestinum treatment, there was no significant change in survival from day 0 to day 4. But, after day 4, the survival rapidly decreased from 87% down to ca. 50% at day 6, and 20% at day 10. The shell length of M. galloprovincialis larvae in no food treatment decreased (p=0.010), while that in I. galbana treatment increased (p<0.001). The daily increment of shell growth of larvae in the I. galbana treatment was 3.79 μm. When the food was A. carterae, G. impudicum, or A. sanguinea, the shell length of larvae increased. But, the shell length decreased when the food was P. triestinum. After 10 days, the shell length of larvae was significantly affected by 6 different treatments (p<0.001), and was higher in the order of treatments: I. galbana > A. carterae > A. sanguinea > G. impudicum > P. triestinum > no food. In considering the harmful effects of red tides on the aquatic ecosystem, not only the effect