Skip to main content
U.S. flag

An official website of the United States government

The role of pH up-regulation in response to nutrient-enriched, low-pH groundwater discharge

June 8, 2022

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.

Publication Year 2022
Title The role of pH up-regulation in response to nutrient-enriched, low-pH groundwater discharge
DOI 10.1016/j.marchem.2022.104134
Authors Nancy G. Prouty, Marlene Wall, J. Fietzke, Olivia Cheriton, Eleni Anagnostou, Brian Phillip, Adina Paytan
Publication Type Article
Publication Subtype Journal Article
Series Title Marine Chemistry
Index ID 70232215
Record Source USGS Publications Warehouse
USGS Organization Pacific Coastal and Marine Science Center