Ecosystem functioning in streams across the US varies depending on many factors, including precipitation, elevation, land use/cover, and contribution of groundwater inputs. Comparisons of co-located groundwater and stream surface water monitoring sites at continental scales are rare, therefore we evaluated spatial patterns in NEON stream sites to determine the possible range in stream behaviors (e.g. groundwater-surface water exchange, in-stream productivity, fluctuations in nutrient levels) these monitoring sites represent, and as a future tool for evaluation of drivers and responses to climate change. Principal components analysis (PCA) was used as a dimension reduction tool, on groundwater and surface water grab samples from NEON Aquatic Sites during the period 2012-2019, with the bulk of the data available in the latter 3 years. From all of the available sites, 8 sites were chosen that represented a range of chemistry states across the network, based on PCA analysis.
Results/Conclusions
Twelve variables that explained the most structure in the PCA axes were selected for further evaluation (Ca, Na, Mg, K, Mn, F, Fe, Cl, DIC, nitrate/nitrite, chlorophyll a, and DOC). Sites tended to cluster similarly when considering both surface water and groundwater concentrations, with strong similarity in explanatory PCA components. Spatial trends in calcium, iron, DIC, nitrate/nitrate, and magnesium contributed to clustering of sites within the PCA, while large temporal variability at each site in DOC, F, and Fe masked clustering patterns at this broad scale of analysis. Variation among the 10 sites was large, suggesting the NEON network will provide important opportunities for testing ecological concepts across a wide range of conditions.