Science Initiative I: Estuarine Hypoxia and Acidification

Goals

The Estuarine Hypoxia and Acidification science initiative aims to determine how the estuarine bioreactor acts to modify the ecological effects of ocean acidification and hypoxia on an upwelling-influenced river-dominated coastal margin.

• Quantify the temporal and spatial variability of the physical transport of coastal water masses into the estuary that have: a) low and harmful dissolved oxygen (DO) concentrations; and/or b) dissolved inorganic carbon (DIC) concentrations that are corrosive to CaCO₃ exoskeletons of estuarine biota.
• Determine the role of: a) primary production (e.g. M. rubrum blooms, benthic diatoms, submerged vegetation, chemolithotrophs); and b) ecosystem-scale metabolism (including ETM and lateral bays), on mitigating or enhancing deleterious effects of estuarine hypoxia and/or estuarine acidification.
• Quantify the importance of riverine discharge on acidification of estuarine/coastal waters
• Develop strategies for early detection and prediction of hypoxia and acidification events.

Conceptual diagram illustrating the geographic origin of identified (solid arrows) or proposed (dashed arrows) mechanisms or processes affecting hypoxia and/or acidification in the estuary and plume. Colored arrows indicate where ecosystem metabolic process.

Estuarine hypoxia and acidification.

Each targeted biological hotspot (Initiatives II-IV) is modulated by river flow and biogenic inputs. Each hotspot is also modulated by the biogeochemistry of the northern California Current, because estuary and shelf are strongly linked through tidal exchange and upwelling promotes the delivery of deep coastal waters into the estuary. CMOP has already documented strong hypoxic events in the CRE, produced by intrusion during the flood tide of oxygen-depleted coastal bottom waters. These events are now regularly monitored through SATURN endurance stations, and an automated Oxygen Watch has been developed. Similar observations have been reported for the smaller Yaquina estuary on the Oregon coast and thus is likely to be a widespread phenomenon for PNW estuaries. It is probable that these water masses have a low aragonite saturation state, since the mechanisms leading to coastal hypoxia also result in ocean acidification.

Much less is known about the ecosystem impacts of these water masses or whether estuarine processes can enhance or mitigate either the low DO or low aragonite saturation state. However, there is mounting evidence that acidification is likely to be a major ‘coastal zone’ issue that will require mitigation steps at the national policy level. Also, freshwater input, nutrients, and organic carbon from the river will certainly impact many aspects of hypoxia and ocean acidification, especially in a river-dominated system such as the CRE. Since estuaries, including the CRE, are shallow and the entire water column can be within the euphotic zone and thus subject to photosynthetic activity, it is possible that oxygen production and CO₂ removal could be enhanced in estuaries, thereby mitigating the deleterious impacts of ocean acidification. Conversely, ecosystem respiration could exacerbate those impacts.

Understanding the intrusion of hypoxic, acidic coastal water masses into the CRE is essential for the characterization of ocean influences on the three CRE biological hotspots.

Science Initiative I Team

Initiative Leader
Joseph Needoba, Oregon Health & Science University (OHSU)

Investigators
António Baptista (OHSU), Byron Crump (Univ. Maryland), Craig McNeil (APL-UW), Tawnya Peterson (OHSU), Holly Simon (OHSU), Yvette Spitz (OSU), Brad Tebo (OHSU)

Students, Post-Docs, and Staff
Suzanne DeLorenzo-Kroll (OHSU), Estefania Ilaneza-Garcia (OHSU), Rachel Golda (OHSU), Clara Llebot (OHSU) Mariya Smith (OHSU) Sarah Riseman (OHSU)

Operational Team Support
Astoria Field Team: Michael Wilkin (OHSU), Katie Rathmell (OHSU), Jo Goodman (OHSU)
Cyber Team: Charles Seaton (OHSU), Paul Turner (OHSU)
Clatsop Community College: Faculty and students of the Maritime Science Program and Integrated Technologies Program