Differences in physiological response to increased seawater temperature in nearshore and offshore corals in northern Vietnam

Suzanne Faxneld (1) , Tove Lund Jörgensen (1) , Ngai D. Nguyen (2) , Magnus Nyström (1, 3) , Michael Tedengren (1)

1 Department of Systems Ecology
2 Institute of Marine Environment and Resources
3 Stockholm Resilience Centre

Effects of elevated seawater temperature show high spatial heterogeneity and variation within and among coral species. The objective of this study was to investigate how two coral species, and from two high latitude reefs differently exposed to chronic disturbance, respond to elevated seawater temperatures. Corals were collected from reefs nearshore, (i.e. subjected to high sediment load, higher chlorophyll α concentrations, turbidity etc.) and offshore, (i.e. less exposed). The corals were exposed in the lab to gradually increasing temperatures (25.5 - 33.5 °C) for 72 h after which they were allowed to recover to ambient temperature (25.5 °C) for 24 h. Production and respiration were measured after 24, 48, 72 and 96 hours. The results show that from nearshore reefs suffered an initial decrease in gross primary production/respiration (GP/R) ratio after 24 h, after only a moderate temperature increase (+ 2 °C, from 25.5 to 27.5 °C), while there was no difference in GP/R ratio between heat-exposed and controls the other days, indicating that the chronic disturbance in the nearshore reef had no effect on their thermotolerance. Furthermore, from the offshore reef showed a decrease in GP/R ratio both after 24 h and 72 h (33.5 °C) of exposure.

Mots clés: Increased water temperature; Galaxea fascicularis; Porites lutea; Disturbance; Physiological responses; High latitude reefs; Vietnam

Domaines: Sciences du Vivant [q-bio]

Suzanne Faxneld, Tove Lund Jörgensen, Ngai D. Nguyen, Magnus Nyström, Michael Tedengren. Differences in physiological response to increased seawater temperature in nearshore and offshore corals in northern Vietnam. Marine Environmental Research, 2011, 71 (3), pp.225. ⟨10.1016/j.marenvres.2011.01.007⟩. ⟨hal-00673200⟩