Abnormal reproduction of the sand crab Emerita analoga in the vicinity of a nuclear generating station in Southern California

Female sand crabs (Emerita analoga) were sampled from 12 beaches along a 350 km stretch of Southern California coastline during the reproductive season in July, 1982. The percentage of mature females with egg masses and the condition of those egg masses were examined at each site. The proportion of mature females with egg masses varied only slightly between beaches. However, at sites within about 20 km of the San Onofre Nuclear Generating Station, a high percentage of females carried egg masses consisting of empty egg shells. A transplant experiment was conducted. Females with empty egg masses were taken from the 6.5 km N study site, where only 5% of the mature females carried normal egg masses, and transferred to running unfiltered seawater in Santa Barbara. After 2 wk, about a third of the transplanted females carried normal egg masses, while at the same time the proportion of mature females with normal egg masses remained at 5% on the beach of origin. Heated water discharged from the nuclear generating station is probably not the cause of the abnormal reproduction of sand crabs along the nearby coast. More likely causes are: (1) runoff of agricultural pesticides from a creek 3 km north of the nuclear generating plant; (2) release of metals from corroding cooling pipes, and/or (3) increased turbidity of the nearshore waters.