Diatom Distribution and Mercury Levels in Two Hawaiian Intertidal Marine Beaches

Abstract

In order to study the ecology of diatoms in Hawaiian beaches, field studies were conducted on two distinctly different marine beaches. One (Kalapana Beach, Island of Hawaii) is composed mostly of black basaltic sand of volcanic origin, and the other (Kahala Beach, Island of Oahu) is mainly biogenic calcium carbonate. A 3-month, baseline field study was conducted during which time mercury levels and numbers of viable diatoms were determined for each sampled intertidal position. When comparable intertidal positions were analyzed between beaches, cell numbers at Kahala were up to 3360-fold higher than those at Kalapana, but mercury values at Kalapana were up to 14-fold higher than those at Kahala. When mercury values were compared to numbers of diatoms, a positive correlation (+0.49) was found for the Kahala data, while a negative correlation (-0.57) was found for the Kalapana data. Mercury values at Kalapana reached reported toxic levels. This may be a factor in reducing the numbers ofdiatoms in the Kalapana Beach.