The National Lakes Assessment (NLA) is a statistical survey of the condition of our nation's lakes, ponds, and reservoirs. It is designed to provide information on the extent of lakes that support healthy biological condition and recreation, estimate how widespread major stressors are that impact lake quality, and provide insight into whether lake quality is improving or getting worse. This dataset is an archived (zipped) file comprised of chemical, physical and biological files used in developing the NLA 2022 report. Sampling was conducted in the summer of 2022 at approximately 1000 sites in the conterminous U.S. Sites were selected using a statistical survey (probabilistic) design. The files include water chemistry, profile data, benthic macroinvertebrates, physical habitat, landscape metrics, secchi depth, tropic status, zooplankton, etc. Users are encouraged to visit the NARS data webpage for updates to data files and data from other surveys. https://www.epa.gov/national-aquatic-resource-surveys/data-national-aquatic-resource-surveys Citation for the NLA 2022 archived data: U.S. Environmental Protection Agency. 2024. National Lakes Assessment: The fourth collaborative survey of lakes in the United States. EPA 841-R-24-006. U.S. Environmental Protection Agency, Office of Water and Office of Research and Development. https://nationallakesassessment.epa.gov/webreport EPA encourages users who are publishing subsets of the data (say as part of a journal article publication) to include the above citation. EPA also encourages users of the data to include the following acknowledgement: “The National Lakes Assessment 2022 data were a result of the collective efforts of dedicated field crews, laboratory staff, data management and quality control staff, analysts and many others from EPA, states, tribes, federal agencies, universities, and other organizations. Please contact nars-hq@epa.gov with any questions.”. Citation information for this dataset can be found in Data.gov's References section.

This data release contains a 17-year record (2005-2022) of discrete chlorophyll data from inland waters, collected from across the nation and territories. These data are from discrete samples (collected in the field and analyzed in the laboratory) from plankton (suspended algae) and periphyton (benthic algae) from lakes, streams, rivers, reservoirs, canals, and other sites. These data are gathered to support process and remote sensing modeling and prediction of Harmful Algal Blooms (HABs). The chlorophyll data were compiled from the Water Quality Portal (WQP) and USGS National Water Quality Lab (NWQL).

Data for uncorrected chlorophyll a, corrected chlorophyll a, and pheophytin from EPA Methods 445 and 446 are included and reported, following the conventions of EPA section 445:

• 12.1 uncorrected chlorophyll a – based on the initial optical measurement of the sample, which includes both chlorophyll a and pheophytin
• 12.2 corrected chlorophyll a – based on optical measurement after acidification and calculation to estimate the amount of active chlorophyll in the original sample
• 12.3 pheophytin – based on calculations to estimate the amount of pheophytin in the original sample

These data were harmonized for reporting units (plankton as µg/L and periphyton as mg/m2), duplicate values, collection depth, site type, negative values, and some extreme values. HABs events are associated with high values of chlorophyll, as algae may be concentrated in dense surface scums. These data may include an indicator for hydrologic event code, which may be helpful in determining HABs events.

Acknowledgements

This work was completed as part of two projects in the USGS Water Mission Area (WMA) Water Quality Processes Program: (1) the Improved Understanding and Prediction of Prioritized Constituents Project, an effort to advance datasets and understanding of chlorophyll, nutrient, carbon, and sediment occurrence and transport, and (2) the Proxies Project, an effort to develop estimation methods for PFAS, harmful algal blooms, and metals, at multiple spatial and temporal scales.

Arar, E.J. and Collins, G.B. 1997. Method 445.0: In vitro determination of chlorophyll a and pheophytin a in marine and freshwater algae by fluorescence. EPA Office of Research and Development.

This data release contains a 17-year record (2005-2022) of discrete chlorophyll data from inland waters, collected from across the nation and territories. These data are from discrete samples (collected in the field and analyzed in the laboratory) from plankton (suspended algae) and periphyton (benthic algae) from lakes, streams, rivers, reservoirs, canals, and other sites. These data are gathered to support process and remote sensing modeling and prediction of Harmful Algal Blooms (HABs). The chlorophyll data were compiled from the Water Quality Portal (WQP) and USGS National Water Quality Lab (NWQL).

Data for uncorrected chlorophyll a, corrected chlorophyll a, and pheophytin from EPA Methods 445 and 446 are included and reported, following the conventions of EPA section 445:

• 12.1 uncorrected chlorophyll a – based on the initial optical measurement of the sample, which includes both chlorophyll a and pheophytin
• 12.2 corrected chlorophyll a – based on optical measurement after acidification and calculation to estimate the amount of active chlorophyll in the original sample
• 12.3 pheophytin – based on calculations to estimate the amount of pheophytin in the original sample

These data were harmonized for reporting units (plankton as µg/L and periphyton as mg/m2), duplicate values, collection depth, site type, negative values, and some extreme values. HABs events are associated with high values of chlorophyll, as algae may be concentrated in dense surface scums. These data may include an indicator for hydrologic event code, which may be helpful in determining HABs events.

Acknowledgements

This work was completed as part of two projects in the USGS Water Mission Area (WMA) Water Quality Processes Program: (1) the Improved Understanding and Prediction of Prioritized Constituents Project, an effort to advance datasets and understanding of chlorophyll, nutrient, carbon, and sediment occurrence and transport, and (2) the Proxies Project, an effort to develop estimation methods for PFAS, harmful algal blooms, and metals, at multiple spatial and temporal scales.

Arar, E.J. and Collins, G.B. 1997. Method 445.0: In vitro determination of chlorophyll a and pheophytin a in marine and freshwater algae by fluorescence. EPA Office of Research and Development.

This data release contains discrete chlorophyll data, specifically corrected chlorophyll a, uncorrected chlorophyll a, and pheophytin pigments, from inland waters in the Illinois River Basin for 1981–2023. These data are discrete samples (collected in the field and analyzed in the laboratory) of plankton (suspended algae) and periphyton (benthic algae) from lakes, streams, rivers, canals, and other aquatic sites. These data support the investigation of harmful algal blooms (HABs) in the Illinois River Basin. The data are multi-source, meaning multiple monitoring organizations collected and analyzed these samples. Data were sourced from the Water Quality Portal (WQP; which contains water quality data from many organizations), Illinois Natural History Survey (INHS), the Fox River Study Group (FRSG; which also contains data from multiple organizations), and previously unpublished data from the US Geological Survey’s National Water Quality Laboratory. Final chlorophyll data are provided in the "all_combined_chl_data.csv" file. Data provided by the INHS included non-chlorophyll water quality data that are published in the "all_other_inhs_data.csv" file. Site information is provided in the "site_list_final.csv" file. The "site_list_original.csv" file provides information for collocated sites that had multiple identifiers (i.e., different site numbers provided by different organizations though samples were all collected at the same physical location). These collocated sites were assigned a single identifier which is used in "site_list_final.csv." Additional details are found in the process steps.

This data release contains discrete chlorophyll data, specifically corrected chlorophyll a, uncorrected chlorophyll a, and pheophytin pigments, from inland waters in the Illinois River Basin for 1981–2023. These data are discrete samples (collected in the field and analyzed in the laboratory) of plankton (suspended algae) and periphyton (benthic algae) from lakes, streams, rivers, canals, and other aquatic sites. These data support the investigation of harmful algal blooms (HABs) in the Illinois River Basin. The data are multi-source, meaning multiple monitoring organizations collected and analyzed these samples. Data were sourced from the Water Quality Portal (WQP; which contains water quality data from many organizations), Illinois Natural History Survey (INHS), the Fox River Study Group (FRSG; which also contains data from multiple organizations), and previously unpublished data from the US Geological Survey’s National Water Quality Laboratory. Final chlorophyll data are provided in the "all_combined_chl_data.csv" file. Data provided by the INHS included non-chlorophyll water quality data that are published in the "all_other_inhs_data.csv" file. Site information is provided in the "site_list_final.csv" file. The "site_list_original.csv" file provides information for collocated sites that had multiple identifiers (i.e., different site numbers provided by different organizations though samples were all collected at the same physical location). These collocated sites were assigned a single identifier which is used in "site_list_final.csv." Additional details are found in the process steps.

Surface water monitoring data from national aquatic surveys (lakes, streams, rivers). This dataset is associated with the following publication: Stoddard , J., J. Van Sickle, A. Herlihy, J. Brahney, S. Paulsen , D. Peck , R. Mitchell , and A. Pollard. Continental-scale increase in stream and lake phosphorus: Are oligotrophic systems disappearing in the U.S.?. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, USA, 50(7): 3409-3415, (2016).

PURPOSE: Chlorophyll a is a photosynthetic pigment common to aquatic algae, and its measurement can provide an estimate of free-floating algae abundance in an aquatic system. For more than 40 years, the Fisheries and Oceans Canada - Great Lakes Laboratory for Fisheries and Aquatic Sciences (DFO-GLLFAS) office in Sault Ste. Marie Ontario has collected water samples for chlorophyll a spectrophotometric analysis, producing data in the form of mg/m3. The collection of chlorophyll a data was generally conducted to assist in characterizing the aquatic systems level of primary productivity, since that can influence fish abundance. This was a supplementary measure of the quality of fish habitat in these systems for a variety of fish-related projects of relevance to DFO’s mandate. Consistency of data collection was dependent on the duration of each project and funding available. DESCRIPTION: The initial study collected chlorophyll a data from the five lakes in the Turkey Lakes Watershed (TLW – Upper and Lower Batchawana Lakes, Wishart Lake, Little Turkey Lake and Turkey Lake) as well as Quinn Lake which is located outside of the TLW (see Smokorowski et al. 2006) in partnership with Environment and Climate Change Canada (ECCC) and Natural Resources Canada (NRCAN), as part of Canada’s Acid Rain Initiative. The TLW study was established in 1979 to evaluate the impacts of acid rain on terrestrial and aquatic ecosystems. This dataset encompasses chlorophyll a data collected from five lakes in the TLW and Quinn Lake (data also collected by the Canadian Wildlife Service and Environment and Climate Change Canada) from 1983 - 2010 with some gaps of varying duration (Webster et al., 2021). Note that an experimental habitat removal took place in some TLW lakes and Quinn Lake in 1999 and 2000. Specifically, in autumn of 1999, 50% of the coarse woody material was removed from the shorelines of Little Turkey Lake and Quinn Lake, and in autumn of 2000, 50% of the course woody material was removed from Wishart Lake shoreline (details available in Smokorowski et al., 2006). Methods Summary: Sampling was only conducted during the open water season and the frequency and extent of sampling frequency in each waterbody varied and was project- and funding-dependent. There are no chlorophyll a data for the years 1986, 1989 – 1990, 1996 – 1997, 2006-2007 and 2009. Sampling was accomplished by rinsing on site an appropriately-cleaned 1 L, brown-opaque polyethylene bottles at least three times. For hand draw samples, the bottle was immersed sub-surface (less than 0.5 meters) to collect the sample. Composite tube samples were collected using an integrated water sampling tube that collected epilimnion water from the entire water column to a depth of 5 meters. Up to five - 1 L (1000 mL) samples were collected per station and returned to the lab on ice. Each 1 L sample was filtered using glass fiber filters (Whatman GF/C, 42.5 mm) within one day of sampling, and then frozen prior to standard chlorophyll a analysis (American Public Health Association [APHA] 1985). From 1983-1998, Chlorophyll a concentrations (mg/L) was calculated based on APHA 1985; from 1998 to present the calculation was based on APHA (1998). The sample dataset information includes the georeferenced sampling locations, the raw data for chlorophyll a calculations, and the calculated chlorophyll a concentrations using both the APHA (1985) and APHA (1998) methods. This dataset was published in partnership with the Canadian Institute of Ecology and Evolution - Living Data Project, which was funded by a CREATE grant from the Natural Science and Engineering Research Council of Canada. We would like to recognize Caroline Dallstream for her effort in publishing this dataset. SAMPLING METHODS: Methods Summary: Sampling was only conducted during the open water season and the frequency and extent of sampling frequency in each waterbody varied and was project- and funding-dependent. There are no chlorophyll a

This dataset contains the results of a literature review of experimental nutrient addition studies to determine which nutrient forms were most often measured in the scientific literature. To obtain a representative selection of relevant studies, we searched Web of Science™ using a search string to target experimental studies in artificial and natural lotic systems while limiting irrelevant papers. We screened the titles and abstracts of returned papers for relevance (experimental studies in streams/stream mesocosms that manipulated nutrients). To supplement this search, we sorted the relevant articles from the Web of Science™ search alphabetically by author and sequentially examined the bibliographies for additional relevant articles (screening titles for relevance, and then screening abstracts of potentially relevant articles) until we had obtained a total of 100 articles. If we could not find a relevant article electronically, we moved to the next article in the bibliography. Our goal was not to be completely comprehensive, but to obtain a fairly large sample of published, peer-reviewed studies from which to assess patterns. We excluded any lentic or estuarine studies from consideration and included only studies that used mesocosms mimicking stream systems (flowing water or stream water source) or that manipulated nutrient concentrations in natural streams or rivers. We excluded studies that used nutrient diffusing substrate (NDS) because these manipulate nutrients on substrates and not in the water column. We also excluded studies examining only nutrient uptake, which rely on measuring dissolved nutrient concentrations with the goal of characterizing in-stream processing (e.g., Newbold et al., 1983). From the included studies, we extracted or summarized the following information: study type, study duration, nutrient treatments, nutrients measured, inclusion of TN and/or TP response to nutrient additions, and a description of how results were reported in relation to the research-management mismatch, if it existed. Below is information on how the search was conducted: Search string used for Web of Science advanced search Search conducted on 27 September 2016. TS= (stream* OR creek* OR river* OR lotic OR brook OR headwater OR tributary) AND TS = (mesocosm OR flume OR "artificial stream" OR "experimental stream" OR "nutrient addition") AND TI= (nitrogen OR phosphorus OR nutrient OR enrichment OR fertilization OR eutrophication)

These raw data associated with this research were collected as part of the United States Environmental Protection Agency's 2018-2019 National Rivers and Streams Assessment (NRSA). The worksheet "Water chemistry data" includes environmental variables examined in this study including total phosphorus (TP), total nitrogen (TN), conductivity, pH, and ecoregion. The worksheet "Diatom ASVs" includes relative abundances of gene sequence reads for each amplicon sequence variant (ASV), which are referred to as taxa. This dataset is associated with the following publication: Smucker, N., E. Pilgrim, C. Nietch, L. Gains-Germain, C. Carpenter, J. Darling, L. Yuan, R. Mitchell, and A. Pollard. Using DNA metabarcoding to characterize national scale diatom-environment relationships and to develop indicators in streams and rivers of the United States. SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, NETHERLANDS, 939: 173502, (2024).

The accession contains chlorophyll a and phaeophytin data collected by Florida State University in the North American coastline for three time periods in 1986. First data set was collected in February, second was collected in April and the last data set was collected in September of the same year. The principal investigator in this study was Dr. Richard Iverson. The data are in Lotus 1-2-3 format. Approximate study location was Atlantic coast; 26-39 degrees N and 71-80 degrees W. Parameters include: position, chlorophyll a (in milligrams per cubic meter) and phaeophytin (in milligrams per cubic meter). Samples were taken every two hours. Additional data associated with this study is filed under NODC reference numbers L00358-L00360.