Citation:

Brown, C. An approach for reference conditions for marine waters: Preliminary analysis for Lummi Nations Waters. Conference Call with Region 10 staff and Lummi Nation Staff, NA, Oregon, September 20, 2019.

Impact/Purpose:

The Lummi Nation as interested in developing numeric nutrient criteria for their tribal waters. At the request of R10 and Lummi Nation staff, ORD reviewed their data and compared to publicly available nearshore oceanic data to see if nearshore water could be used as reference condition for Lummi Nation marine waters. ORD demonstrated that mixing diagrams combined with ocean end member data may be useful for developing reference conditions for Lummi waters.

Description:

At the request of Region 10 and Lummi Nations staff, ORD was asked to examine datasets provided by Lummi Nations to see if an approach could be developed for reference conditions for marine waters. Through the N-STEPS program, reference conditions had been developed for freshwater; however, analysis for marine waters was hindered due to limited data availability and complications associated with the estuarine environment (e.g., high temporal variability due to ocean-estuary coupling). Lummi Nations staff provided water quality data used in the N-STEP analysis. This dataset was supplemented with publicly available nearshore datasets. Nutrient concentrations in the nearshore environment revealed that peak nutrient concentrations were similar between Tatoosh Island, which is at the entrance of Puget Sound, and offshore of Newport, Oregon at station NH-5. These data may be useful to serve as reference condition for marine waters. Typically, the 75th percentile is calculated for reference condition datasets. The 75th percentile for nitrate+nitrite and phosphate were similar between Tatoosh Island and NH-5, suggesting that this might serve as reference condition for marine waters. Nutrient and dissolved oxygen data from Tatoosh Island were compared to data collected at Lummi Nation waters and nearby sites sampled by Washington Department of Ecology. Mixing diagrams (property versus salinity graphs) suggest that WA Department of Ecology sites were similar to marine end members; while Lummi Nation sites occasionally had nutrient levels exceeding marine and freshwater end members. More work would be needed but this exploratory analysis suggests that mixing diagrams and using offshore data may be useful for deriving reference conditions for marine waters. Minimum dissolved oxygen at Lummi Waters sites occurred at high salinities, suggesting import of oceanic waters may be the cause of low dissolved oxygen at these sites, rather than in situ processes. This suggests that dissolved oxygen from Lummi Nation sites may have limited utility in stressor-response relationships unless data analysis controls for import of marine waters.

Record Details: