Prevalence and incidence of 2023 coral bleaching caused by thermal stress and their impact on the associated reef fishes and benthic invertebrates in Lian, Batangas

• Main Authors: De Leon, Kathleen Anne F., Alfonso, Don Gabriel A., Lema, Gabrielle Alexandra N., Olendo, Sara Francine T.
• Format: text
• Language: English
• Published: Animo Repository 2024
• Subjects: Coral bleaching > Philippines > Batangas; Temperature—Physiological effect; Coral reefs and islands > Philippines > Batangas; Biology
• Online Access: https://animorepository.dlsu.edu.ph/etdb_bio/88
• Institution: De La Salle University

Coral reefs play a vital role in the sustainability of marine ecosystems. Given their mutualistic relationship with many marine species, such as butterflyfishes, as well as the benefits of the reef system to other ecosystems, the well-being of these coral reefs is of the utmost importance. This prompts researchers to reevaluate the status of the reefs and the factors driving significant changes, whether they are due to environmental or anthropogenic factors. Coral bleaching, caused by thermal stress, and its impacts on reef-associated fish and benthic invertebrates were investigated in Talim Bay, Lian, Batangas, in the year 2023. Surveys conducted in July and November across sixteen monitoring stations assessed coral cover, butterflyfish diversity, benthic invertebrate populations, and sea surface temperatures (SST) with degree heating weeks (DHW). These surveys include the C30 method and snorkeling censuses for butterflyfishes and target invertebrate indicators. Results showed a slight decline in average hard coral cover (HCC) from 33.0% in July to 32.1% in November, with the cover of dominant algal assemblages (turf algae) remaining stable. Despite thermal stress in July, significant bleaching was not observed in November, indicating potential coral resilience and acclimatization. Butterflyfish species richness decreased significantly, though abundance remained stable, suggesting adjustments in the species composition. Among benthic invertebrates, there was a notable loss of giant clams in November, while other species exhibited no significant changes in abundance. SST decreased from 29-31℃ in July to 28-30℃ in November, with DHW dropping from 3.8- 4.7℃-weeks to 0.5℃-weeks. Findings of the study provide some insights towards understanding the relationship between thermal stress, coral cover, and the reef-associated species that may provide bases for more effective conservation strategies.