CHAPTER 4 Separate and combined impacts of waterborne and dietary copper intake on Evechinus chloroticus early life stages
ABSTRACT
Most marine toxicity studies focus on waterborne pollutants, while organisms living in a polluted area are likely to be exposed to contaminated food as well. This study investigated the toxic effect of environmentally realistic levels of copper from the diet versus waterborne exposure, on larvae of the sea urchin Evechinus chloroticus. Larvae were exposed to two levels of copper: 1.3 μg/L or 10 μg/L via one of three copper sources: dissolved copper, algal diet (Dunaliella tertiolecta) cultured at these copper levels, or in a combined treatment. In addition, the effect of pulse (4 days exposure) vs. chronic exposure was evaluated. In chronic exposure, the experimental design was fully crossed between copper source and copper level. In pulse exposure,only the highest copper level was used for all copper sources. Sea urchins were
monitored for 38 d post-settlement to investigate carry-over effects. Detrimental effects observed during larval development included a decrease in normal development at the highest copper level, and a delay in development (30% larvae with a rudiment across all copper levels vs. 65% in controls) with waterborne exposure. Settlement success was strongly impaired in most treatments (25 – 55% of controls) and was 30% lower in dietary than in waterborne treatments. Surviving settlers exposed to dietary copper as larvae were on average 30% smaller than controls, while those exposed to dissolved copper were 60% larger. Overall toxic
effects on larvae were stronger with waterborne exposure, but dietary exposure elicited stronger carry-over effects. Pulse exposure was more toxic than chronic exposure when copper was present in the diet but not when present in water only,suggesting that acclimation may occur; however this is dependent on the route of copper intake. Toxic effects occurred at a level of copper commonly found in the field, indicating the importance of considering pollutant intake from the diet by larvae.