Response to sedimentation stress of the gorgonian coral Primnoella chilensis from the Chilean fjord region

Abstract

Sedimentation is one of the main disturbance factors influencing benthic communities and coastal reef organisms through a variety of mechanisms. In Chilean Patagonia, rising anthropogenic intrusions such as coastal road projects and aquaculture installations threaten the local biodiversity causing increased sedimentation with even more to be expected. Primnoella chilensis (Philippi, 1894) is an important habitat-forming gorgonian coral, abundant in this region, but significant abundance decreases were reported for the last decade. The present study aimed to describe physiological and behavioural stress responses of P. chilensis to increased sedimentation. Therefore, two laboratory experiments were conducted measuring colonies' responses in respiration for 18 hours as well as documenting polyp activity and mucus secretion for 15 days under sediment exposure. No significant differences in oxygen consumption were measured, presumably due to the low number of test organisms. Further, no mucus secretion or changes in colonies' overall activity were detected. However, an analysis on single polyp level revealed a significantly increased percentage of open polyps when exposed to high sedimentation. This increased activity may be explained by intensified filter-feeding behaviour and active sediment rejection. In addition, a spawning event was detected as a possible stress reaction. All in all, the results suggest that P. chilensis is able to tolerate the simulated sedimentation loads of 225 and 450 mm/y due to its morphology and compartmentalized behaviour. This goes along with previous findings on gorgonian corals. Nonetheless, anthropogenic disturbances may by far exceed and alter natural ones due to their extent and persistence causing unpredictable, dangerous conditions for the benthic community