Long-term effects of competition and environmental drivers on the growth of the endangered coral Mussismilia braziliensis (Verril, 1867)

Abstract

Most coral reefs have recently experienced acute changes in benthic community structure, generally involving dominance shifts from slow-growing hard corals to fast-growing benthic invertebrates and fleshy photosynthesizers. Besides overfishing, increased nutrification and sedimentation are important drivers of this process, which is well documented at landscape scales in the Caribbean and in the Indo-Pacific. However, small-scale processes that occur at the level of individual organisms remain poorly explored. In addition, the generality of coral reef decline models still needs to be verified on the vast realm of turbid-zone reefs. Here, we documented the outcome of interactions between an endangered Brazilian-endemic coral (Mussismilia braziliensis) and its most abundant contacting organisms (turf, cyanobacteria, corals, crustose coralline algae and foliose macroalgae). Our study was based on a long (2006–2016) series of high resolution data (fixed photoquadrats) acquired along a cross-shelf gradient that includes coastal unprotected reefs and offshore protected sites. The study region (Abrolhos Bank) comprises the largest and richest coralline complex in the South Atlantic, and a foremost example of a turbid-zone reef system with low diversity and expressive coral cover. Coral growth was significantly different between reefs. Coral-algae contacts predominated inshore, while cyanobacteria and turf contacts dominated offshore. An overall trend in positive coral growth was detected from 2009 onward in the inshore reef, whereas retraction in live coral tissue was observed offshore during this period. Turbidity (+) and cyanobacteria (−) were the best predictors of coral growth. Complimentary incubation experiments, in which treatments of Symbiodinium spp. from M. braziliensis colonies were subjected to cyanobacterial exudates, showed a negative effect of the exudate on the symbionts, demonstrating that cyanobacteria play an important role in coral tissue necrosis. Negative effects of cyanobacteria on living coral tissue may remain undetected from percent cover estimates gathered at larger spatial scales, as these ephemeral organisms tend to be rapidly replaced by longer-living macroalgae, or complex turf-like consortia. The cross-shelf trend of decreasing turbidity and macroalgae abundance suggests either a direct positive effect of turbidity on coral growth, or an indirect effect related to the higher inshore cover of foliose macroalgae, constraining cyanobacterial abundance. It is unclear whether the higher inshore macroalgal abundance (10–20% of reef cover) is a stable phase related to a long-standing high turbidity background, or a contemporary response to anthropogenic stress. Our results challenge the idea that high macroalgal cover is always associated with compromised coral health, as the baselines for turbid zone reefs may derive sharply from those of coral-dominated reefs that dwell under oligotrophic conditions.

South Atlantic Coral Reefs Are Major Global Warming Refugia and Less Susceptible to Bleaching

“…Our analysis shows that more than half of South Atlantic coral species are tolerant to turbid environments, which is more than twice than the proportion recorded for the Caribbean and more than three times higher than that for the Indo-Pacific (Figure 1). An emblematic example is Mussismilia braziliensis, an endemic species which is one of the main South Atlantic reef-builders, that displays higher growth rate and reproduction effort when found in more turbid conditions (Pires et al, 2011;Ribeiro et al, 2018). In addition, turbid inshore reefs in the South Atlantic often display higher coral cover and abundance than less turbid offshore reefs, particularly Montastraea cavernosa (Francini-Filho et al, 2013;Loiola et al, 2019).…”

Marine Invertebrate Extracts Induce Colon Cancer Cell Death via ROS-Mediated DNA Oxidative Damage and Mitochondrial Impairment

“…Secondary metabolites produced in response to competitive pressure allow them to survive. Many scientific studies have shown the advantages of possessing these secondary metabolites to survive [12][13][14][15]. Of the more than 33 currently known phyla, 97% are present in and 45% are exclusive to the marine ecosystem [16].…”

Age, growth, reproduction and management of Southwestern Atlantic’s largest and endangered herbivorous reef fish, Scarus trispinosus Valenciennes, 1840

“…Spatial variation in growth and other demographic patterns among parrotfishes has been associated to sex, fishing effort and resource quality/availability (Gust, Choat & Ackerman, 2002; Taylor & Choat, 2014; Lessa et al, 2016). Across the Abrolhos Bank, there is high cross-shelf variability in environmental conditions and fishing effort (Bruce et al, 2012; Freitas et al, 2011; Freitas et al, 2014; Moura et al, 2011; Moura et al, 2013; Ribeiro et al, 2018), coinciding with the sharp demographic partition between our samples from coastal (slower-growth and ages <9 years) and offshore reefs (faster growth and ages between 3–22 years) (see Fig. 8 and Table 1).…”

“…The region encompasses South Atlantic’s largest reefs (20% of the area) and rhodolith beds (∼40%), the two benthic megahabitats where parrotfishes are common. The region is under the synergistic effects of climatic and local anthropogenic stressors (Bruce et al, 2012; Ribeiro et al, 2018). Abrolhos is Brazil’s main reef fisheries ground (Freitas et al, 2014) and bears the country’s first no-take National Marine Park (910 km 2 , declared in 1983) and two community-based Extractive Reserves (ERs), Cassurubá (1,010 km 2 , 2009) and Corumbau (815 km 2 , 2000).…”