64. Carbonate system parameters monitoring in coastal waters of Chile

Rodrigo Torres (1,2)*, Patricio Manriquez (3), Emilio Alarcon (1,4), Jose Luis Iriarte (2,4,5), Maximiliano Vergara (6), Silvia Murcia (7), Ernesto Davis (8)

1 Centro de Investigación en Ecosistemas de la Patagonia (CIEP), Coyhaique, 5951822, Chile.
2 Centro de Investigación: Dinámica de Ecosistemas Marinos de Altas Latitudes (IDEAL), Valdivia, Chile.
3 Centro de Estudios Avanzados en Zonas Áridas (CEAZA), Coquimbo, Chile.
4 Universidad Austral de Chile, 5501558, Puerto Montt, Chile.
5 Centro de Investigación COPAS, Universidad de Concepción, Concepción, Chile.
6 Programa de Doctorado en Ciencias de la Acuicultura, Universidad Austral de Chile, 5501558, Puerto Montt, Chile.
7 Universidad de Magallanes, Punta Arenas, Chile.
8 Fundación CEQUA, Punta Arenas, Chile.

Background
The carbonate system variability plays a role determining the exposure of marine organisms to high CO2 stressors (low pH, carbonate under-saturation). Here we show spatial and temporal the carbonate system variability along the coast of Chile.

Methods
Time Series: Surface seawater pH and total alkalinity were measure in the intertidal zone, two or three times per week during a period of one or two years at the coast of Chile (at 30°S, 40°S and 42°S). Stations located at 30°S and 40°S correspond to the coastal upwelling system of Chile, and the station at 42°S correspond to Northern Patagonian Archipelago.
Surveys: Two decades of carbonate system data from Antofagasta (23°S) to Cape Horn (56°S) were revised, including data collected from the new carbonate system monitoring program on opportunity ships (Cruceros Australis S.A.).

Findings
Surface waters pH range in upwelling areas and inner fjord water ranged from 7.7 to 8.4 pH units and 7.7 to 8.5 pH units, respectively. However the intra annual variability of those coastal ecosystems was substantially different. While most of the variability of pH and carbonate saturation state were associated to 1-2 weeks of upwelling evens in exposed shore of central Chile (42°S), the variability of pH and carbonate saturation state at inner waters of Northern Patagonia was mainly associated to the Summer-Winter annual cycle. While upwelling of pCO2 super-saturated waters lowers surface water omega in central and northern Chile, freshening of the coastal ocean in Patagonian Archipelago fjord reduce Omega in surface waters even in CO2 equilibrated waters.

Conclusions
Similar ranges of pH along the coast of Chile but different variability patters, highlight that variability (e.g. intra-annual variability) should be consider in the perturbation experiment design to assess the role of “exposure” of marine organism to high CO2 levels.