Watershed, lake and food web factors influence diazotrophic cyanobacteria in mountain lakes

Cyanobacterial blooms can occur in freshwater ecosystems largely isolated from development and not experiencing extensive cultural eutrophication. For example, remote mountain lakes can experience intense blooms of diazotrophic (nitrogen-fixing) cyanobacteria caused by factors acting at different spatial and temporal scales. In this study, we examined how cross-scale interactions among watershed, lake, and food web characteristics influence diazotrophic cyanobacteria biovolume in mountain lakes. We quantified diazotrophic cyanobacteria biovolume, zooplankton abundance, and physico-chemical variables for 29 lakes in the Cascade Mountains of Oregon, USA, in summer 2019. Watershed characteristics were compiled from historical data sets available for the region. Diazotrophic cyanobacteria biovolume ranged across the lakes from 0 to 1,930,000 µm3 mL-1; Dolichospermum was the most common genus. Random forest models showed that 11 watershed, lake, and food web characteristics explained 76% of ..., We compiled a data set of 132 Oregon Cascade lakes on fish stocking, water chemistry, and watershed characteristics from various sources to identify a potential set of study lakes (D. M. Johnson 1985; USDA Forest Service 1996; US Environmental Protection Agency 2009; 2016).  We only considered lakes >10 hectares and with a maximum depth of ≥3 meters to exclude extremely small lakes or ponds that can be seasonally variable in depth and emergent vegetation cover (US Environmental Protection Agency 2009). We created a representative sample of lakes from this dataset using binary regression trees from the R package rpart v.4 (T. Therneau, Atkinson, and Ripley 2019). A binary regression tree repeatedly divides the response data into nodes to reduce variation within nodes based on predictor variables. Total P concentration was the response variable as P is often a crucial lake characteristic for diazotrophic cyanobacteria and varies significantly in the Cascades (D. M. Johnson 1985; D. P. ..., Microsoft Excel, Google Sheets, Apple Numbers, or any CSV reading software, # The dataset associated with, \"Watershed, lake and food web factors influence diazotrophic cyanobacteria in mountain lakes\"

The master dataset contains the values by lake of the response variable-diazotrophic cyanobacteria biovolume and potential lake (physical/chemical), food web and watershed factors.
Parameters that were measured in situ in 2019 were averaged across between the two sampling bouts.

The average biovolume dataset contains the mean biovolume for each cell or counting unit (filament/colony) by phytoplankton genus or lowest identified taxonomic group.

The correlation matrix dataset contains the Spearman correlation coefficients between each of 38 final predictors for the binary regression tree and random forest model. The final set of predictors were reached by the following steps: Predictors were removed if they had zero or near zero variance based on percent of unique values (<10%) and frequency ratio (i.e. frequency of the most common value divided by the frequen...