Inhibition of coral recruitment by macroalgae and cyanobacteria

Abstract

Coral recruitment is a key process in the maintenance and recovery of coral reef ecosystems. While intense competition between coral and algae is often assumed on reefs that have undergone phase shifts from coral to algal dominance, data examining the competitive interactions involved, particularly during the larval and immediate post-settlement stage, are scarce. Using a series of field and outdoor seawater table experiments, we tested the hypothesis that common species of macroalgae and cyanobacteria inhibit coral recruitment. We examined the effects of Lyngbya spp., Dictyota spp., Lobophora variegata (J. V. Lamouroux) Womersley, and Chondrophycus poiteaui (J. V. Lamouroux) Nam (formerly Laurencia poiteaui) on the recruitment success of Porites astreoides larvae. All species but C. poiteaui caused either recruitment inhibition or avoidance behavior in P. astreoides larvae, while L. confervoides and D. menstrualis significantly increased mortality rates of P. astreoides recruits. We also tested the effect of some of these macrophytes on larvae of the gorgonian octocoral Briareum asbestinum. Exposure to Lyngbya majuscula reduced survival and recruitment in the octocoral larvae. Our results provide evidence that algae and cyanobacteria use tactics beyond space occupation to inhibit coral recruitment. On reefs experiencing phase shifts or temporary algal blooms, the restocking of adult coral populations may be slowed due to recruitment inhibition, thereby perpetuating reduced coral cover and limiting coral community recovery.

Biological community structure on patch reefs in Biscayne National Park, FL, USA

“…Many species of coral larvae require CCA to settle (Morse et al 1988;Heyward and Negri 1999), and availability of CCA is negatively correlated with macroalgal abundance (Hixon 1997). Dictyota spp., the most abundant fleshy algae observed in this study, was not as abundant on these patch reefs (15.4 ± 0.8% cover) compared to other locations on the Florida reef tract (Lirman and Biber 2000;Beach et al 2003;Kuffner et al 2006), whereas SSS was fairly abundant (overall mean 21% cover). In a study conducted in this area in 1981, Burns (1985) reported that they observed lots of "uncolonized reef substrate."…”

“…A mean of 20.8 ± 1.1% of the bottom was assigned to the category SSS, defined as hard substratum covered mostly in crustose coralline algae (CCA) and lacking sediments >1 mm deep, macroalgae, or thick turf algae as previously described in Kuffner et al (2006). This category was considered to be an index of suitable settlement substratum for coral larvae and is analogous to the "cropped substratum" category of .…”

Chemical Defenses: From Compounds to Communities

“…A study of the recruitment of coral larvae in Guam found that the presence of L. majuscula significantly reduced larval survival in Acropora surculosa and recruitment in Pocillopora damicornis (Kuffner and Paul, 2004). Similar studies in the Florida Keys showed that larvae of Porites astreoides avoided settling near Lyngbya polychroa and Lyngbya confervoides on recruitment tiles and that L. majuscula negatively impacted survival and recruitment of larvae of the octocoral Briareum asbestinum (Kuffner et al, 2006). These studies highlight the potential for secondary metabolites to influence the structure of marine ecosystems, and demonstrate the lack of knowledge surrounding the allelopathic role of LTA and other cyanobacterial secondary metabolites.…”

Crustose coralline algal species host distinct bacterial assemblages on their surfaces

“…have been isolated from algal biofilms and coral mucus (de Castro et al, 2010;Horta et al, 2014), and there is some evidence linking Staphylococcus strains to coral disease (Kellogg et al, 2013). Cyanobacteria, especially those in the order Oscillatoriales, inhibit settlement of coral larvae and have been implicated as causative agents of black band disease (Frias-Lopez et al, 2003;Kuffner and Paul, 2004;Kuffner et al, 2006;Casamatta et al, 2012). Larvae of multiple coral species avoid settling on the surface of P. solubile Ritson-Williams et al, 2014), and this may be due to inhibitory microbial OTUs that cause larval avoidance of this species of CCA.…”