FOUR-YEAR STUDY OF OXIC HOT MOMENTS DRIVEN BY SALINIZATION OF A FORMER FRESH WATER HABITAT HIGHLIGHTS BIDIRECTIONAL EXCHANGE BETWEEN SURFACE AND GROUND WATER

Human activities, such as engineered barriers, can increase the salinity of freshwater systems, which then affect the biogeochemistry of floodplains and wetlands. Inundations during high water levels can mobilize dissolved oxygen (DO), a driver of biochemical function, towards the subsurface, stimulating microbial activity. This requires insight into the spatiotemporal variability of essential biochemical drivers within coastal habitats. Measuring DO at a sufficient temporal resolution has limited our ability to predict how chronic sea-level rise will impact former freshwater ecosystems functionality due to flooding. We seek to fill this knowledge gap. Following dam removal, the former freshwater habitat at Beaver Creek, Washington, USA is now disturbed by periodic intrusion of saline waters during high tide. Using state-of-the-art probes (Opti O₂) we continuously measured subsurface DO over 4 years. This data set is the first measurement in a coastal environment with the requisite temporal resolution to obtain subsurface oxygen consumption time series. Co-located measurements of salinity, surface and groundwater levels, and meteorological parameters let us parse the critical drivers of coastal ecosystem biochemistry. Wavelet analyses elucidate the interactions between DO, salinity and water level during oxygenation events followed by subsequent returns to anoxia. Information theory revealed DO’s relationship with meteorological data. We show the importance of multi-year, continuous measurements to elucidate the non-linear coupling of climate, biochemistry and hydrology.

Primary Presenter: Ruby Ghosh, Opti O2 (ghosh@optio2.com)

Authors:

Ruby Ghosh, Opti O2  (ghosh@optio2.com)

Emilio Grande, Dept.of Earth and Environmental Sciences, California State University East Bay  (emilio.grande@csueastbay.edu)

Charles McIntire, Opti O2  (mcintire@optio2.com)