Ecohydrologic Linkages of Stream Chlorophyll a across the Contiguous U.S.

Chlorophyll a (Chl a) is an important indicator of stream water quality and considered a crucial biotic variable in the domain of river ecology. However, concentrations of Chl a is governed by the multitude interactions of climatic, hydrologic, and land use/cover processes. Observational data for stream water quality and hydrology were gathered for numerous stream monitoring stations across the contiguous U.S. from the USGS NWIS and EPA STORET databases. Data for climatic variables such as net solar radiation (Rn) and atmospheric pressure (P_a) were collected from the national solar radiation database. A systematic data analytics methodology was then employed to determine the ecohydrologic linkages of stream Chl a. Our results indicated a strong positive linkage of T_w and pH with the concentrations of Chl a, suggesting the domination of photosynthesis at specific temperature ranges. Both the nutrient components (TN and TP) had a strong positive/negative control on Chl a based on the range of TN/TP ratio. However, Rn, P_a, salinity (SC), and discharge (Q) exhibited a weak control on Chl a. The findings of the study would help manage stream water quality and ecosystem health across the U.S. and beyond.