Recruitment and Resilience of a Harvested Caribbean Octocoral

Abstract

Disturbance events are an important component of the ecology of coral reefs and increasingly frequent disturbances coupled with a lack of population resilience may contribute to changes in the structure of coral reef communities. The harvest of the Caribbean octocoral Antillogorgia elisabethae provides an opportunity to explore the relationship between adult abundance and recruitment and the manner in which recruitment contributes to the resilience of local populations. Recruitment of A. elisabethae was monitored in 20, 1-m2 quadrats at 8 sites along the southern edge of the Little Bahama Bank from 2004 through 2007. A. elisabethae has been harvested in The Bahamas for over fifteen years and all of the sites had been harvested three times, including a harvest during the course of the study. Abundances of adult colonies at those sites as well as a location that had not been harvested were also determined. Recruitment was highly variable, differing between sites, transects within sites, and, depending on the site, between years. Recruitment was best correlated with adult abundance averaged across the surrounding site. Regression analyses suggest abundance on smaller scales had only small effects on recruitment. The effects of the harvesting were site specific ranging from a 38 to 67% reduction in the density of mature colonies. The sites with the most abundant A. elisabethae continued to have the highest abundances after harvesting and there was no significant difference in recruitment before and after harvesting. Population size-structure at 6 of 8 sites that have been harvested multiple times exhibited an overall depletion in small colonies suggesting long term suppression of recruitment and declining populations. Severe depression of adult abundances coupled with local recruitment can create a negative feedback and lead to the decline of local populations. Populations that are dependent on self-recruitment are not resilient to large disturbance events.

Regulation of population size of arborescent octocorals on shallow Caribbean reefs

“…Height was determined (±1 cm) using a flexible tape measure stretched from the holdfast to the colony apex. Abundances were analyzed separately for adults (> 5 cm tall), and recruits (≤5 cm tall), with this size cut-off based on the maximal height to which the recruits of most octocoral species are likely to grow in 1 yr (Lasker 1990(Lasker , 2013. While the benthos was inspected for all small octocorals, sampling efficiency probably was low for recruits consisting of only a few polyps (i.e.…”

Harvesting Effects, Recovery Mechanisms, and Management Strategies for a Long-Lived and Structural Precious Coral

“…rubrum is characterized by a low dispersal that leads its populations to be generally self-seeding [ 27 ], [ 38 ], and breeding units seem also to be restricted in space, suggesting that density may play an important role in the reproduction of this species [ 28 ]. Thus, events causing total mortality on adult colonies could lower the potential for recovery even more through reproduction [ 40 ]. Alternatively, negative density-dependent processes affecting recruitment and post-recruitment survival were also reported in corals due to intra-specific competition and resources limitation (i. e. availability of suitable substrate to settle) [ 39 ].…”

Dynamics of Stony Coral and Octocoral Juvenile Assemblages Following Disturbance on Patch Reefs of the Florida Reef Tract

“…Partial and complete colony mortality on high-impact sites [28] appeared to have dampened recruitment and/ or juvenile survival. Higher abundance and cover of living coral are important drivers of coral recruitment [52][53][54]. However, percent cover on high-impact sites was comparable to cover on low-impact sites following the cold-water event.…”