Hypoxia in surface coastal waters at the entrance of the Gulf of California and its relation to coastal upwelling
Carlos Alberto Herrera Becerril, National Autonomous University of Mexico, Posgrado en Ciencias de la Tierra, Mexico City, DF, Mexico, Joan-Albert Sanchez-Cabeza, Universidad Nacional Autonoma de Mexico, Unidad Académica Mazatlán, Instituto de Ciencias del Mar y Limnología., Mexico City, SI, Mexico, Andrea Rebeca Lara Cera, National Autonomous University of Mexico, Facultad de Ciencias, México City, DF, Mexico, León Felipe Álvarez Sánchez, Instituto de Ciencias del Mar y Limnología, Universidad Nacional Autónoma de México, Ciudad de México, Unidad de Informática Marina, Mexico City, DF, Mexico, Maria Luisa Machain-Castillo, UNAM National Autonomous University of Mexico, Instituto de Ciencias del Mar y Limnología, Mexico City, DF, Mexico and Ana Carolina Ruiz-Fernández, Universidad Nacional Autonoma de Mexico, Unidad Académica Mazatlán, Instituto de Ciencias del Mar y Limnología, Mazatlán, SI, Mexico
Abstract:
Coastal ecosystems are especially affected by global change, including deoxygenation, sea level rise, acidification and climate change. With the aim of identify and quantify these changes in Mexican coastal zone, we have implemented low-cost long-term coastal observatories in three different zones (Mexican Pacific, Gulf of Mexico and Caribbean), which provide high temporal-resolution physico-chemical data (Sanchez-Cabeza et al., 2018).
Oxygen time-series (2014-2016) were recorded by an autonomous sensor in Mazatlan Bay (entrance to the Gulf of California). We observed hypoxic (some almost anoxic) events in surface waters (~5 m), with duration ranging from days to weeks. Remote sensing temperature analysis and instrumental wind data showed that at least some of the events could be caused by coastal upwelling of oxygen poor waters. Indeed, the oxycline is shallow and anoxia is observed < 50m nearshore.
First results suggest that these events are natural and do not represent an extra ecologic pressure in the region. However, monitoring is needed to establish an early warning system of possible changes such as a frequency increase, due to a possible increment of coastal upwelling events (Bakun et al., 2015), or a regional/global deoxygenation.
Bakun, A et al., 2015. Anticipated effects of climate change on coastal upwelling ecosystems. https://doi.org/10.1007/s40641-015-0008-4
Sanchez-Cabeza J.A et al., 2018. A low-cost long-term model of coastal observatories of global change. https://doi.org/10.1080/1755876X.2018.1533723
