Effect of Macroalgal Expansion and Marine Protected Areas on Coral Recovery Following a Climatic Disturbance

Abstract

Disturbance plays an important role in structuring marine ecosystems, and there is a need to understand how conservation practices, such as the designation of Marine Protected Areas (MPAs), facilitate postdisturbance recovery. We evaluated the association of MPAs, herbivorous fish biomass, substrate type, postdisturbance coral cover, and change in macroalgal cover with coral recovery on the fringing reefs of the inner Seychelle islands, where coral mortality after a 1998 bleaching event was extensive. We visually estimated benthic cover and fish biomass at 9 sites in MPAs where fishing is banned and at 12 sites where fishing is permitted in 1994, 2005, 2008, and 2011. We used analysis of variance to examine spatial and temporal variations in coral cover and generalized additive models to identify relations between coral recovery and the aforementioned factors that may promote recovery. Coral recovery occurred on all substrate types, but it was highly variable among sites and times. Between 2005 and 2011 the increase in coral cover averaged 1%/year across 21 sites, and the maximum increase was 4%/year. However, mean coral cover across the study area (14%) remained at half of 1994 levels (28%). Sites within MPAs had faster rates of coral recovery than sites in fished areas only where cover of macroalgae was low and had not increased over time. In MPAs where macroalgae cover expanded since 1998 there was no recovery. Where coral was recovering on granite reefs there was a shift in relative prevalence of colony life-form from branching to encrusting species. This simplification of reef structure may affect associated reef fauna even if predisturbance levels of coral cover are attained.

Pattern and intensity of human impact on coral reefs depend on depth along the reef profile and on the descriptor adopted

“…Taxonomic composition is often considered as the best descriptor of the overall status of ecosystems ; however, the high biodiversity of Maldivian coral reefs (Andr efou€ et, 2012) led us to adopt non-taxonomic descriptors that assemble species according to their ecological role (Darling et al, 2012;Wilson et al, 2012). In particular, we estimated the percent cover of five broad benthic categories (Lasagna et al, 2008): 1) hard (zooxanthellate) corals; 2) soft (zooxanthellate) corals; 3) other (azooxanthellate, suspension-feeding) invertebrates; 4) macroalgae; 5) abiotic attributes (sand, rock, coral rubble).…”

Similar impacts of fishing and environmental stress on calcifying organisms in Indian Ocean coral reefs

“…The one weak association was a negative association between acan thurids and coral cover that would indicate their preference for feeding on dead coral surfaces (Marshell & Mumby 2012). While this does not support some ecosystem management recommendations, it does correspond with a number of large-scale studies that have failed to find significant coral− parrot fish associations, identified other factors, or found that herbivorous fish passively associate with, rather than actively control, algae-coral relationships (McClanahan et al 2011b, Wilson et al 2012, Carassou et al 2013, Russ et al 2015, Suchley et al 2016.…”

Incorporating herbivorous sea urchins in ramet culture of staghorn coral Acropora cervicornis

“…While the stressors affecting coral populations can differ widely at the local level, competition with macroalgae and algal turfs has been recognized as a global cause of coral mortality (McCook et al 2001, Diaz-Pulido & McCook 2004, Birrell et al 2008, DiazPulido et al 2009, Barott et al 2012) and as a determinant of coral recovery from climatic disturbances (Wilson et al 2012). In fact, recent studies on the effectiveness of Marine Protected Areas have identified the preservation of an intact and diverse herbivore guild as one of the keys to enhancing coral resilience (Hughes et al 2007, Mumby et al 2007, Mumby & Steneck 2008.…”