A comparison between sites of growth, physiological performance and stress responses in transplanted Tridacna gigas

• Published in: Aquaculture Vol. 219; no. 1; pp. 815 - 828
• Main Authors: Elfwing, Tina, Blidberg, Eva, Sison, Marilou, Tedengren, Michael
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 02.04.2003; Elsevier Science; Elsevier Sequoia S.A
• Subjects: Animal aquaculture; Animal populations; Animal productions; Animal, plant and microbial ecology; Applied ecology; Aquaculture; Biological and medical sciences; Coasts; Copper; Ecotoxicology, biological effects of pollution; Effects of pollution and side effects of pesticides on protozoa and invertebrates; Fundamental and applied biological sciences. Psychology; Giant clam; Invertebrate aquaculture; Marine; Mollusca; Mollusks; Photosynthesis; Physiology; Tridacna gigas; Water quality; Zooxanthellae; South China Sea; Asia; Philippine Islands; ISEW, Philippines; Physiology; Giant clam; Zooxanthellae; Copper; Photosynthesis; Growth rate; Toxicity; Biological productivity; Coastal zone; Marine environment; Restocking; Bivalvia; Thallophyta; Symbionte; Endangered species; Algae; Antifouling paint; Coral reef; Heavy metal; Dinophyta; Water pollution; Invertebrata; Mollusca; Respiration; Aquaculture
• ISSN: 0044-8486; 1873-5622
• DOI: 10.1016/S0044-8486(02)00660-9

The continuous increase of human activities in the tropical coastal zones threatens the water quality necessary for cultivating giant clams. In order to investigate the potential for disturbances, of natural and/or anthropogenic origin, to affect growth in giant clams, transplantation experiments were conducted in the north of the Philippines. After 6 months, there were significantly lower values for both wet weights (wwt) and shell lengths (SL) at the “disturbed sites”, where the clams had experienced both natural turbidity and impacts from human settlement and fish pens, compared to the reference site. Differences between sites were also manifested as impaired physiological performance under identical light regimes and water quality in a laboratory experiment: gross production and respiration ( P g/ R) ratios were lower, Rapid Light Curves (RLC) showed lower maximal production at light saturation, chlorophyll (chl) a levels per cell was higher and the degree of epibionts increased with over 90% compared to controls. The suggested explanation to this is reduced light penetration as a result of both natural higher turbidity and nutrient loading brought about by, e.g. intensive fish aquaculture in the channel. Light penetration will be further reduced in the future with present development of fish pens in the channel. To assess tolerance to additional anthropogenic impacts, such as release of copper from antifouling treatment of fish cages, clams from different sites were exposed to a sublethal dose of copper (5 μg Cu 2+ l −1) under laboratory conditions. Clams from all sites showed lowered P g/ R ratios when exposed to the metal, although the control clams displayed a larger percentage decrease than clams from the channel. This could be interpreted as higher tolerances in those clams already adapted to a stressful environment, or merely reflect an overall energy conservation through reduced metabolic activity.