CONSIDERATIONS IN THE DESIGN OF CULTURE EXPERIMENTS: AMMONIA SPP. IN CU-ENRICHED SEAWATER?

Surface and pore water samples from two bays in Puerto Rico (Torrecilla Lagoon and Jobos Bay) were analyzed for total copper (Cu) concentrations. The ranges of these concentrations were 1.57 μM - 2.59μM. However, based on seawater alkalinity and pH, these concentrations could not be used in designing experiments because the culture medium became oversaturated. This reality demonstrates the importance of understanding chemical parameters of seawater prior to initiating culture experiments.

Two experiments were performed at 0.20 μM and 0.30 μM (undersaturated), using a 24-well culture device constructed from Teflon® to minimize absorption. Juvenile Ammonia sp. was exposed to controlled pH, temperature, and alkalinity, with Cu⁺² concentrations as treatment conditions, for a period of 30 days. Biological (maximum and intermediate diameters) and physicochemical parameters were measured every 3 to 4 days. Specimens were imaged at the end of each experiment to evaluate for morphological anomalies and growth rates.

Shell deformities in Cu treatments were not as common as anticipated, though approximately 10% of individuals showed a vertical change in coiling axis, resulting in higher than normal trochospiral growth. In addition, relative slower growth rates are an indication that Cu⁺² serves as a cause and effect stressor. These experiments suggest that heavy metals are not solely responsible for shell deformities in natural environments, but likely act with other stressors (e.g., hypoxia).