Ecological assessments of the coral reef communities in the Eastern Caribbean and the effects of herbivory in influencing coral juvenile density and algal cover

Abstract

Caribbean reefs have been unevenly surveyed, with many areas lacking baseline data. In this study, the current status of Orbicella reefs, a structurally complex forereef habitat, was quantified in an understudied region, the Eastern Caribbean. During 2011 the same observers surveyed benthic assemblages, coral juvenile density, herbivorous fishes, and invertebrates at 30 Orbicella reefs in four Eastern Caribbean areas: Antigua, Barbados, St Lucia, and St Vincent and the Grenadines (hereafter St Vincent). Not all Orbicella forereefs were functionally the same in the Eastern Caribbean. Benthic communities and herbivorous fishes varied greatly among islands. Hard coral had the highest overall percent cover on most reefs in this study, with an average cover of 22%, and was greater than fleshy macroalgal cover at 83% of the sites. Overall, coral juvenile density was low but was positively associated with higher densities of Diadema antillarum, highlighting the importance of herbivory on the reefs. Nearshore coral reefs in Barbados were in a better state than other areas, exhibiting higher coral cover dominated by spawning corals, higher densities of coral juveniles exhibiting higher coral cover dominated by spawning corals, higher densities of coral juveniles and D. antillarum. Low biomass of herbivorous fishes at a majority of the coral reef sites is of major concern for the functioning of these reefs. Conservation of parrotfishes and other herbivores is necessary given the abundance of algae on most of these reefs and the beneficial effect of their presence on coral juveniles. This is the first comprehensive study that compares the state of Orbicella reefs in the Eastern Caribbean, providing valuable information that will be useful in creating realistic targets for future management and conservation.

Assessment of Elkhorn Coral Populations and Associated Herbivores in Akumal, Mexico

“…The high number of small bodied Redtail parrotfish species may be contributing to this trend ( Table 2). Our results also revealed increased coral presence and cover with increasing urchin populations and confirmed previous studies demonstrating that higher Diadema densities are associated with coral recovery (Edmunds and Carpenter, 2001;Carpenter and Edmunds, 2006;Myhre and Acevedo-Gutiérrez, 2007) and lower macroalgal cover (Carpenter and Edmunds, 2006;Myhre and Acevedo-Gutiérrez, 2007;Williams et al, 2016;Rodríguez-Barreras et al, 2018) in the Caribbean. This correlation may also be due to positive feedbacks associated with structural complexity and Diadema populations (Lee, 2006).…”

“…Our study revealed that even at low biomass, parrotfish browser species, which feed specifically on macroalgae, have a significant negative correlation with macroalgal cover. Parrotfish biomass in the Mesoamerican Barrier Reef has been increasing slightly in the past few years, and the populations observed here in Akumal are comparable to country and region-wide parrotfish population sizes (Jackson et al, 2014;McField et al, 2018), indicating that recovering populations may be reaching a threshold in which they can exert effective top down control of algal growth (Williams et al, 2016). Even though total parrotfish biomass was not correlated to lower macroalgal cover, fish grazing activity from non-browser species may have other positive benefits such as contributing to increased coral calcification (Suchley and Alvarez-Filip, 2017) or overall reef accretion (Cramer et al, 2017).…”

“…Our results support recommendations to enhance herbivore populations as one mechanism to promote coral recovery and control macroalgal growth on degraded coral reefs (Adam et al, 2015a;Williams et al, 2016). Efforts to protect and potentially enhance fish populations are already underway through designation of a fish sanctuary and marine reserve in Akumal (Official Gazette of the Federation, 2016; Yucatan Times, 2019).…”

Coral Reef Bleaching: An Ecological and Biological Overview

“…Despite occupying only 0.1% of the ocean, coral reefs play a critical role in marine ecology, and in human sustainability, they are invaluable from a variety of perspectives. They are home to more than a quarter of all the species that inhabit the ocean, provide coastal protection, and support more than 10 millions of people living on tropical coasts [1,2]. Economic goods and ecosystem services of coral reefs are worth more than US $20 trillion annually [3].…”

Coral Reef Resilience Index for Novel Ecosystems: A Spatial Planning Tool for Managers and Decision Makers - A Case Study from Puerto Rico

“…But the 2005 sea surface warming episode and massive coral reef bleaching event caused an unprecedented coral mortality episode across the northeastern Caribbean region, including P.R., that mostly impacted large reef-building taxa [11][12][13][14]. More than a decade later, there is still no net recovery among many of the impacted coral species, and reef communities have followed a significantly different trajectory resulting in the emergence of novel ecosystems largely dominated by ephemeral coral species [15] and macroalgal growth [16][17][18]. Although such impacts have been well documented, long-term impacts associated to the emergence of novel benthic assemblages on reef functions, values, and benefits still remain largely unknown.…”