Effects of a thermal discharge on the mortality of copepods in a subtropical estuary

Abstract

Experimental field treatments were employed to examine the thermal mortalities of copepods exposed to the heated effluents of a power generating plant located on a subtropical estuary. Significant lethal effects were observed for all species studied, with mass mortalities occurring during the warmest months of the year. Of the seven species examined, the copepods identified as estuarine species had steeper mortality curves and higher upper lethal thermal limits than the more neritic forms. The estuarine species have apparently evolved the ability to live in subtropical areas under temperature conditions very close to their upper thermal limits. Coastal species, on the other hand, exhibit a greater variation in temperature sensitivity so thermal additions in subtropical estuaries could be very significant in limiting their distribution and abundance.