Effects of Injury and Nutrition on Sediment Disturbance by a Marine Polychaete, Clymenella torquata
First Name:
Beth
Last Name:
Campbell
Field of Study:
Marine Biology
Keywords:
marine worms, injury, nutrition, sediment mixing, marine ecology
Approximately 70% of the ocean floor is covered by sediment. The invertebrates that live in these habitats modify the structure and composition of sediments, including sediment chemistry, nutrient cycling, and bacterial communities as they burrow, feed, defecate, and flush their tubes and burrows with seawater. This bioturbation can significantly impact physical and biological factors, including the release of material to the water column and the community structure. Non-lethal tissue loss to predators or other disturbances has been frequently observed in sedimentary communities and previous research has reported significant effects of one-time injury on animal activity. Food supply can also influence animal activity.
In laboratory studies, we examined effects of injury and nutrient enrichment on bioturbation rates of a common species of bamboo worm, Clymenella torquata. Individual worms were held in PVC cores in a recirculating seawater system. Experiments were performed to compare the concurrent effects of single and repeated posterior injury and low homogeneous enrichment and high surface enrichment with controls. Defecation, sediment mixing, growth rates, regeneration rates and surface behaviors were monitored.
Bioturbation by C. torquata significantly decreased following a repeated posterior injury, but only modest effects of homogeneous algal enrichment were observed. Repeated injury correlated with greater reductions in defecation, with effects evident over a longer time frame. Growth rates decreased following repeated injury relative to controls. Regeneration rates did not vary based on injury type or homogenous sediment enrichment. The downward movement of surface particles was similar among treatments. Calculated hypothetical sediment reworking rates indicate population-level effects of injury and sediment enrichment.
A follow-up study confirmed that sediment bioturbation decreases with repeated injury in C. torquata. In this case, algal enrichment at the sediment surface correlated with an increase in bioturbation. Repeated injury resulted in significant decreases in total recorded surface activities and defecation. Intact worms in enriched sediment were more active at the sediment surface than worms in other treatments. Overall, intact worms subducted more surface sediment as a result of feeding at depth and enrichment resulted in greater worm activity below 8 cm.
These findings help explain how the activities of animals living in sediments are modified by injury and food supply, and can be used to improve future models of sediment reworking. Improved models will increase understanding of marine community ecology and ocean systems.
