Hot and heavy: Responses of ragworms (Hediste diversicolor) to copper-spiked sediments and elevated temperature

Sediment contamination and seawater warming are two major stressors to macrobenthos in estuaries. However, little is known about their combined effects on infaunal organisms. Here we investigated the responses of an estuarine polychaete Hediste diversicolor to metal-contaminated sediment and increased temperature. Ragworms were exposed to sediments spiked with 10 and 20 mg kg-1 of copper at 12 and 20 degrees C for three weeks. No considerable changes were observed in the expression of genes related to copper homeostasis and in the accu-mulation of oxidative stress damage. Dicarbonyl stress was attenuated by warming exposure. Whole-body energy reserves in the form of carbohydrates, lipids and proteins were little affected, but the energy consumption rate increased with copper exposure and elevated temperature, indicating higher basal maintenance costs of rag -worms. The combined effects of copper and warming exposures were mostly additive, with copper being a weak stressor and warming a more potent stressor. These results were replicable, as confirmed by two independent experiments of similar settings conducted at two different months of the year. This study suggests the higher sensitivity of energy-related biomarkers and the need to search for more conserved molecular markers of metal exposure in H. diversicolor.

Automated summary

Sediment contamination and seawater warming are two major stressors for estuary benthos. This study investigated the combined effects of metal-contaminated sediment and increased temperature on an estuarine polychaete, Hediste diversicolor. The results showed that the combined effects were mostly additive, with copper being a weak stressor and warming a more potent stressor. This study highlights the importance of energy-related biomarkers and the search for more conserved molecular markers to assess metal exposure in H. diversicolor.