Juveniles of the cold-water coral Caryophyllia huinayensis under sediment stress – an ex situ experiment

The walls of the Chilean fjords are hotspots of biodiversity, but also threatened by the development of salmonid farming and coastal infrastructure. One of the consequences of these activities is the increase of sediment load in a region of high natural run-off. The cold-water coral (CWC) Caryophyllia huinayensis abounds on the steep slopes of the fjords. Its distribution, often in the shelter of overhangs, suggests a natural sensitivity to sedimentation, but actual data on the susceptibility of this coral species to sediment is lacking. Here, we explore sedimentation effects on the putatively sensitive juvenile stages of C. huinayensis. In general, it is important to understand the capabilities of CWC recruits to cope with anthropogenic impacts as their viability is the guarantee for the population future. In order to determine the resilience of juvenile C. huinayensis to sediment stress, a three-month aquaria experiment was conducted with three sediment loads: the current natural sediment concentration in Comau Fjord, 100- and 1000-fold higher values expected from local construction and coastal erosion. Measured response variables were polyp activity, and variation in coral mass and in calyx dimensions. Under high turbidity, polyp activity was clearly reduced, therefore significantly affecting prey capture effectivity and thus nutrition. Hence, the management plans for the area need to take into account the deleterious effects of increased sedimentation on vulnerable CWCs.