VARIABILITY OF CORAL SKELETAL TIN, COPPER, ZINC AND CADMIUM IN PORITES LOBATA CORALS FROM KONA, HAWAII

Coral skeletal Cu, Zn, Sn, and Cd concentrations were measured along multiple transects (1992-1998) at annual and sub-annual resolution in coral colonies collected from two sites on the west coast of Hawaii: a moderately “anthropogenically impacted” site (Keauhou Bay) and a “control” site (Makalawena). Metal concentrations were compared between skeletal transects from the same colony (intra-colony variability), between different colonies from the same location (inter-colony variability), and between coral colonies from the two locations (site-site variability).

Cu and Zn concentrations ranged from 0.3 ppm to 7.5 ppm, and 0.1 ppm to 2.5 ppm, respectively and mean Cu and Zn concentrations were found to be significantly higher in corals from the impacted site compared to the control site. Possible sources of Cu and Zn in Keauhou Bay include anti-fouling boat paints and golf course fertilizers, which are not present at Makalawena. Mean coral skeletal Sn concentrations (non-lattice bound) from the Hawaii corals (0.19 +/- 0.25 µmol Sn/mol Ca; range: below detection to 1.75 µmol Sn/mol Ca) were comparable in concentration to those measured in other studies. Significant differences in median tin concentrations within (intra-colony variability) and between (inter-colony variability) colonies were found. The pattern of variability in tin concentrations across a single colony may be related to a colonies size and shape. The mean lattice-bound cadmium concentrations measured (5.81 +/- 9.78 nmol Cd/mol Ca) were comparable to natural background Cd concentrations measured in open ocean corals from the Galapagos (1-8 nmol Cd/mol Ca). Mean cadmium concentrations were significantly different within a coral (i.e. between transects) and the general temporal patterns in cadmium concentration could not be consistently replicated across a colony. The large intra-colony variability in Sn and Cd prevented the detection of a significant difference in mean Sn or Cd concentrations between the impacted and control sites.

These results highlight the importance of using multiple time series to assess coral skeletal tracers and the need for a better understanding of the biological controls on trace metal incorporation during biomineralization.