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MEPS prepress abstract   -  DOI:

Boring worms (Sipuncula and Annelida: Polychaeta): their early impact on ETP coral reefs

María Fernanda Cardona-Gutiérrez, Edgardo Londoño-Cruz*

*Corresponding author:

ABSTRACT: The current form, condition, and survival of coral reefs depend on the balance between construction and destruction. Natural processes such as bioerosion can cause this balance to lean towards destruction, threatening these ecosystems. Polychaetes and sipunculids are members of the boring community; however, knowledge of their identity and role in the bioerosive process and their capacity to remove CaCO3 in the coral reefs of the Eastern Tropical Pacific (ETP) is currently scarce. To tackle this problem, five experimental units made of Pocillopora spp. branches were deployed in four reef zones (Back-reef, Reef-flat, Reef-front, and Reef-slope) of two reefs (La Azufrada and Playa Blanca) for two different time periods (6 mo. - P1 and 9 mo. - P2) (N=80) in Gorgona National Natural Park, Colombia. All worms (polychaetes and sipunculids) were identified and net removal and bioerosion rates were determined. In total, 137 worms were found, 64.2% in La Azufrada and 35.8% in Playa Blanca. Statistical analyses showed there were no significant effects of reef, reef-zone, or duration of exposure (6 vs. 9 months) for either the net carbonate removal or the bioerosion rate. Irrespective of reef or duration of exposure, average net removal was 0.022 g for P1 and 0.027 g for P2, and 0.032 g in La Azufrada and 0.018 g in Playa Blanca, respectively. The average bioerosion rate, again, irrespective of reef or duration of exposure, was 2.553 g kg-1 yr-1 for P1 and 2.011 g kg-1 yr-1 for P2, and 2.839 g kg-1 yr-1 in La Azufrada and 1.807 g kg-1 yr-1 in Playa Blanca, respectively. As can be seen, the trend between periods is opposite for net removal and bioerosion rate, which can be interpreted as a deceleration on the impact of worms on the coral substrate as time passes. We suggest that regardless of the small body size of the worms we found boring our coral cylinders, their role in CaCO3 removal is very important. The information provided here—species involved and amounts removed—is key in the understanding of the bioerosion process in ETP coral reefs.