Nueces River Tidal Nutrient Bioassays

Increasing frequency and severity of fish kills within the tidal segment of the Nueces River have raised concerns about water quality degradation. Previous research to investigate these fish kills linked mortality to low dissolved oxygen events related to algal blooms, which had been triggered by high nutrient loadings. Possible sources of excess nutrient loadings include permitted point source discharges, runoff from urban and rural non-point sources, on-site sewage facilities, groundwater discharges, and others. Additional stressors may include water management and engineered structures impeding flow and prolonging residence time of constituents in the tidal segment.

These growing concerns have also been expressed by local residents and users of the tidal segment of the Nueces River and have led to the formation of Nueces River Tidal Stakeholder Group in 2023. However, little data regarding the nutrient loadings to this segment are available to decision makers and resource managers. Information gained from this study will be combined with information from historical data reviews and new field sampling to guide resource managers towards addressing the most relevant nutrient in future load reduction decisions, as each nutrient can have different sources.

The purpose of the study is to determine which nutrient(s) (nitrogen, phosphorus, or both) is responsible for algal growth on the tidal segment of the Nueces River. To determine which nutrient is controlling algal growth, nutrient bioassays will be conducted on a seasonal/quarterly basis from one site (co-located with the known "hot spot" for algae enrichment) in the Nueces River Tidal segment.