Hyporheic Oxygen Dynamics in the East River, Colorado: Insights From an In‐Situ, High Frequency Time Series During Two Distinct Flow Seasons

Abstract

Dissolved oxygen (DO) is an important constituent of stream ecosystems. Fish and most invertebrates rely on high DO concentrations to maintain healthy populations. DO is largely controlled by primary production by autotrophs, exchange with the atmosphere, water temperature (which controls saturation), and consumption by heterotrophic organisms (Odum, 1956). Riverbeds and hyporheic zones harbor extensive surfaces for heterotrophic bacteria. Thus, the process of hydrologic exchange of water and DO between the river and bed contributes indirectly to river DO concentrations as well. In general, the hyporheic zone has been found to be a sink of DO due to heterotrophic respiration (Mulholland et al., 1997). Furthermore, several hyporheic modeling studies have emphasized the importance of hyporheic respiration or DO consumption due to biogeochemical cycling (e.g., De Falco et al., 2018;Marzadri et al., 2016). Empirical evidence at a few sites have demonstrated that hyporheic DO consumption helps facilitate biogeochemical processes such as denitrification (Baker et al., 1999;Zarnetske et al., 2011a). However direct long-term, high-frequency observations of DO concentrations in rivers

Seasonal drivers of dissolved oxygen across a tidal creek–marsh interface revealed by machine learning

“…Our approach required a network of sensors collecting trustworthy, high‐frequency data across long‐term deployments, including unsaturated periods and dynamic flow regimes. The Opti O 2 sensor met these coastal instrumentation challenges, as previously observed in river systems (Gooseff et al 2023).…”

“…2). In particular, the Opti O 2 DO sensor is capable of withstanding intermittent wet and dry cycles such as those experienced in our groundwater well without degradation of data quality (Ghosh et al 2019; Gooseff et al 2023). In addition, the short measurement 5‐min interval (made possible by remote power maintained by solar) provided higher sample sizes, which allowed us to apply our cross‐validation strategy.…”

“…All sensors were set to measure at 5-min intervals. The 14 different parameters (river DO and temperature, floodplain DO and temperature, seep DO and temperature, river and floodplain water level and salinity, and 4 climate variables) from the network of sensors were compressed into a single deterministic data stream then telemetered using Opti O 2 's flashlogger hardware (Gooseff et al 2023) and a Campbell Scientific CR6 datalogger. DO values were corrected for temperature and salinity (Benson and Krause 1984) using temperature from the Opti O 2 instruments and salinity from the Aquatrolls.…”

“…Because DO regulates many key biogeochemical processes and can be measured by in situ sensors, it also serves as a useful marker of ephemeral yet biogeochemically important ecosystem control points (Bernhardt et al 2017; Regier et al 2021). Recent advances in instrumentation allow for reliable, high spatial resolution DO measurement with in situ sensors (Gooseff et al 2023). These continuous oxygen time series were obtained in otherwise challenging environments that experience dynamic water saturation conditions.…”