Ramicrusta invasive alga causes mortality in Caribbean coral larvae

Abstract

The settlement of coral larvae is an important process which contributes to the success and longevity of coral reefs. Coral larvae often recruit to benthic structures covered with crustose coralline algae (CCA) which produce cues that promote settlement and metamorphosis. The Peysonneliaceae Ramicrusta spp. are red-brown encrusting alga that have recently become abundant on shallow Caribbean reefs, replacing CCA habitat, overgrowing corals and potentially threatening coral recruitment. In order to assess the threat of Ramicrusta to coral recruitment, we compared the survival and settlement of Porites astreoides and Favia fragum larvae to 0.5 – 2 mg ml-1 solutions of Ramicrusta sp. or CCA as well as sterile seawater (control). In all cases larval mortality was extremely high in the Ramicrusta treatments compared to the CCA and control treatments. We found 96% (± 8.9% standard deviation, SD) mortality of P. astreoides larvae when exposed to solutions of Ramicrusta and 0 - 4% (± 0 - 8.9% SD) mortality in the CCA treatments. We observed 100% F. fragum larval mortality when exposed to Ramicrusta and 5 – 10% (± 10 – 20% SD) mortality in the CCA treatments. Settlement or surface interaction of larvae in the CCA treatments was 40 - 68% (± 22 - 37% SD) for P. astreoides and 65 - 75% (± 10 - 19% SD) for F. fragum. Two P. astreoides larva that survived Ramicrusta exposure did settle/surface interact, suggesting that some larvae may be tolerant to Ramicrusta. These results suggest that Ramicrusta is a lethal threat to Caribbean coral recruitment.

Benzoyl Chloride Derivatization Advances the Quantification of Dissolved Polar Metabolites on Coral Reefs

“…Homoserine betaine was detected at two reefs (JS and TK) and had a significant positive correlation to the encrusting red-brown algaeRamicrusta (Figure 4), an invasive species on coral reefs shown to overgrow corals and threaten coral recruitment. 60,61 Homoserine betaine is a novel metabolite structurally identified by Pade et al 2016 and previously reported in a green alga Monostroma nitidium, 62 shellfish Callista brevisiphonata, 63 and a turban shell Turbo argyrostoma. 62 Its specific function in reef and nonreef organisms is largely undescribed, excluding Pade et al 2016, where the novel role of homoserine betaine as a previously unknown, compatible solute produced by the cyanobacterium Trichodesmium spp.…”

Soundscape enrichment increases larval settlement rates for the brooding coral Porites astreoides

“…In the years since Lillis’ data were collected in 2017, Tektite Reef has faced numerous acute and chronic stressors including a major bleaching event and the previously mentioned SCTLD outbreak which has led to the rapid mortality of several massive coral species [ 54 , 55 ]. Our own surveys of Tektite have noted decreases in hard coral cover from 28.9% in 2017 to 19.8% in 2022 with concurrent increases in the presence of cyanobacterial mats and macroalgae (TA Mooney 2017–2022, unpublished data), including overgrowth of peyssonnelid algal crusts which threaten natural larval settlement [ 56 ]. Although we did not note major differences in the overall shapes of acoustic spectra recorded at Tektite and Cocoloba in 2022 compared with 2017 ( figure 5 a ; electronic supplementary material, figure S2), Kaplan & Mooney [ 43 ] reported that hourly SPL RMS levels in the low-frequency (100–1000 Hz) band at Tektite in 2013 ranged from 100 to 105 dB re 1 μPa.…”

Advancing Reef Monitoring Techniques through Exometabolomics: Quantification of Labile Dissolved Organic Metabolites on Coral Reefs

“…53 Homoserine betaine was detected at two reefs (JS and TK) and had a significant positive correlation to encrusting red-brown algae Ramicrusta (Figure 5), an invasive species on coral reefs shown to overgrow corals and threaten coral recruitment. 54,55 The presence and relatively high median concentrations of homoserine betaine at JS (1.6 nM) and TK (1.1 nM) is an intriguing finding that requires further investigation due to the limited information available regarding the potential function and presence of homoserine betaine in reef-associated organisms. GABA is a non-protein amino acid and one of the major inhibitory neurotransmitters in animal central nervous systems.…”