Coral reefs and their ecosystems are threatened by both global stressors, including increasing sea-surface temperatures and ocean acidification (OA), and local stressors such as land-based sources of pollution that can magnify the effects of OA. Corals can physiologically control the chemistry of their internal calcifying fluids (CF) and can thereby regulate their calcification process. Specifically, increasing aragonite saturation state in the CF (ΩCF) may allow corals to calcify even under external low saturation conditions. Questions remain regarding the physiological processes that govern the CF chemistry and how they change in response to multiple stressors. To address this knowledge gap, the boron δ11B and B/Ca were analyzed in tropical corals, Porites lobata, collected at submarine groundwater seeps impacted by the release of treated wastewater in west Maui, Hawai'i, to document the interactions between high nutrient / low pH seep water on CF carbonate chemistry. Results show substantial up-regulation of pH and dissolved inorganic carbon (DIC) with respect to seawater in P. lobata corals collected from within the wastewater impacted area at Kahekili Beach Park compared to the control site at Olowalu Beach. The ΩCF was 9 to 10 times higher than ambient seawater Ω, and 13 to 26% higher than in corals from the control site and from values previously observed in tropical Porites spp. corals. Such elevated up-regulation suggests that corals exposed to nutrient-enriched, low pH effluent sustain CF supersaturated with respect to aragonite, possibly as an internal coping mechanism to combat multiple stressors from land-based sources of pollution. This elevated up-regulation has implications to coral vulnerability to future climate- and ocean-change.
|Title||The role of pH up-regulation in response to nutrient-enriched, low-pH groundwater discharge|
|Authors||Nancy G. Prouty, Marlene Wall, J. Fietzke, Olivia Cheriton, Eleni Anagnostou, Brian Phillip, Adina Paytan|
|Publication Subtype||Journal Article|
|Series Title||Marine Chemistry|
|Record Source||USGS Publications Warehouse|
|USGS Organization||Pacific Coastal and Marine Science Center|
Geochemical analysis (including stable boron, boron:calcium ratio, and carbon and oxygen isotopes) were measured from coral cores collected in July 2013 from the shallow reef at Kahekili in Kaanapali, west Maui, Hawaii from scleractinian Porites lobata.