DataSheet_1_Thresholds of hypoxia of two Red Sea coral species (Porites sp. and Galaxea fascicularis).zip

• Main Authors: Jacqueline V. Alva García, Shannon G. Klein, Taiba Alamoudi, Silvia Arossa, Anieka J. Parry, Alexandra Steckbauer, Carlos M. Duarte
• Format: Dataset
• Language: unknown
• Published: 2022
• Subjects: Oceanography; Marine Biology; Marine Geoscience; Biological Oceanography; Chemical Oceanography; Physical Oceanography; Marine Engineering; coral reefs; dissolved oxygen; deoxygenation; O2 depletion; exposure time; Ocean acidification
• Online Access: https://doi.org/10.3389/fmars.2022.945293.s001; https://figshare.com/articles/dataset/DataSheet_1_Thresholds_of_hypoxia_of_two_Red_Sea_coral_species_Porites_sp_and_Galaxea_fascicularis_zip/21406335

Anthropogenic pressures have driven large-scale declines in coral cover on >50% of tropical coral reefs. Most research efforts have focused on ocean warming, ocean acidification, and overfishing impacts. Despite increasing instances of reef-associated hypoxic events, the role of reduced O 2 in affecting coral reef performance is largely unknown. Here, we assessed the hypoxic thresholds of two Red Sea coral species: Porites sp. and Galaxea fascicularis. We exposed coral fragments of both species to one control treatment (6.8 mg O 2 L −1 ) and three reduced dissolved oxygen treatments (5.25, 3.5, and 1.25 mg O 2 L −1 ) during a 10-day experiment. Across the two species, maximum (Fv/Fm) and effective (F′/F m ′) photochemical efficiency, chlorophyll a, and dark respiration declined under the lowest O 2 treatment (1.25 mg O 2 L −1 ). Porites sp. coral fragments, however, were remarkably resistant and showed no signs of sublethal bleaching after 10 days of exposure to reduced O 2 . Conversely, 17% of G. fascicularis fragments bleached after only three nights of exposure to the lowest O 2 treatment (1.25 mg O 2 L −1 ). Our data show that longer-term hypoxic events (i.e., days to weeks) can induce coral bleaching, but these effects depend on the extent of O 2 reduction and are likely species-specific. Importantly, the levels of O 2 usually defined as hypoxic (~2.0 to 2.8 mg O 2 L −1 ) do not adequately capture the thresholds reported here. Hence, further research is urgently needed to more accurately describe the vulnerability of coral taxa to hypoxic and anoxic events.