Relative tolerance of cirripede larval stages to acute thermal shock: A laboratory study

(1) Meroplankters drawn into once-through cooling circuits of coastal power plants are subjected to transient thermal stress. The effect of such acute thermal shock on the development of barnacle larvae was studied in the lab oratory. (2) The response of the barnacle larvae (naupliar and cyprid stages) to ele vated temperature was dependent on exposure time and their stage of develop ment. (3) Among the stages tested, N-6 larvae showed maximum tolerance. Exposure to 37 degreesC did not affect larval survival, but delayed development of N -2 larva to cypris by one day. (4) Exposure at 40 degreesC delayed, hastened or did not affect the develop ment time of N-2 and N-4 larvae through cypris, depending on exposure time. (5) Ten mins exposure at 43 degreesC proved lethal to all larval stages wit h mortality ranging from 20 to 86%. (6) Development success of the surviving larvae, measured in terms of cypri s yield, showed no significant difference from controls, at temperatures be low 40 degreesC. (7) Settlement activity was significantly affected in only those cyprid lar vae which were exposed to 43 degreesC for 10 min. (8) Results of the present study indicate that thermal stress experienced i n the once-through cooling system does not have significant impact on survi val and development of the barnacle larvae at temperatures of 37-40 degrees C. (C) 2000 Published by Elsevier Science Ltd.