These data have been collected as part of a cooperative project between the U.S. Geological Survey (USGS) and the U.S Environmental Protection Agency. This project began in 2016 and consisted of a mesocosm experiment quantifying short term responses by a transplanted natural diatom dominant algae community exposed to gradients of nitrogen, phosphorous, and a mixture of both nitrogen and phosphorus. The data consist of water quality parameters such as temperature and pH as well as aqueous nutrient concentrations and algae responses, including chlorophyll a concentrations, algae dry mass, algae ash-free dry mass, and intra-cellular phosphorus and nitrogen in algae. Algae growth rates were estimated from these data and are meant to be used with water-quality models; the results of this investigation can be found in the manuscript associated with this data release (Schmidt and others 2019).

Data from a set of studies that ran from 1977-1978, and 1980-1982, around the site of Gaillard Island, Mobile Bay, Alabama, before, during, and after its construction (1979-1981). Extant data from the MESC Data Management System include sediment particle size distribution (001), identification and enumeration of benthic fauna (002), discrete hydrography and turbidity (003) during and after island construction, and discrete hydrography and turbidity before island construction (004).

Quantitative phytoplankton data was collected as part of an interdisciplinary and multiagency experimental study investigating harmful algal bloom (HAB) dynamics in the Caloosahatchee River located in southwestern Florida. Algae and cyanobacteria play crucial roles in aquatic ecosystems, but under favorable environmental conditions such as nutrient enrichment certain taxa may experience population growth booms resulting in HABs. HABs are becoming increasing common in the Caloosahatchee and the Lake Okeechobee system, yet the drivers and processes controlling these events is still under investigation. Here, three independent mesocosm experiments were conducted on the Caloosahatchee River at the W. P. Franklin Lock and Dam, Florida, in February 2021, May 2021, and July 2021 to test the effects of nutrient enrichment of phytoplankton assemblage structure at different times in the year to capture natural temporal variability in water quality and phytoplankton assemblages. The experimental installation consisted of three floating metal cradles each containing four fiberglass chambers filled with native river water. The twelve chambers were assigned to one of five treatments: phosphate (P), nitrate (N), urea (U), ammonium (A), or control (C). Only four of the five treatments were selected for a given experiment: February 2021 treatments included P, N, A, and C, May 2021 treatments included P, U, A, and C, and July 2021 treatments included U, N, A, and C. The P, N, U, and A treatment chambers were enriched in the appropriate nutrient by applying a concentrated dosing solution of either dibasic dodecahydrate sodium phosphate, anhydrous sodium nitrate, solid crystal urea, or liquid ammonium hydroxide respectively to elevate concentrations above ambient levels. The mesocosms were treated and sampled approximately every 24 hours over a 72-hour period (Time 0, Time 24, Time 48, Time 72). May and July 2021 mesocosm were also sampled a week from the initial dosing (T240). Water quality, phytoplankton, cyanotoxin, and environmental DNA (eDNA) samples were collected before and after dosing each day. The current dataset contains only the phytoplankton data including absolute and relative abundance measures at the genus to species level as natural units (NU/mL), cell densities (cells/mL), and biovolumes (um3/mL).

Quantitative phytoplankton data was collected as part of an interdisciplinary and multiagency experimental study investigating harmful algal bloom (HAB) dynamics in the Caloosahatchee River located in southwestern Florida. Algae and cyanobacteria play crucial roles in aquatic ecosystems, but under favorable environmental conditions such as nutrient enrichment certain taxa may experience population growth booms resulting in HABs. HABs are becoming increasing common in the Caloosahatchee and the Lake Okeechobee system, yet the drivers and processes controlling these events is still under investigation. Here, three independent mesocosm experiments were conducted on the Caloosahatchee River at the W. P. Franklin Lock and Dam, Florida, in February 2021, May 2021, and July 2021 to test the effects of nutrient enrichment of phytoplankton assemblage structure at different times in the year to capture natural temporal variability in water quality and phytoplankton assemblages. The experimental installation consisted of three floating metal cradles each containing four fiberglass chambers filled with native river water. The twelve chambers were assigned to one of five treatments: phosphate (P), nitrate (N), urea (U), ammonium (A), or control (C). Only four of the five treatments were selected for a given experiment: February 2021 treatments included P, N, A, and C, May 2021 treatments included P, U, A, and C, and July 2021 treatments included U, N, A, and C. The P, N, U, and A treatment chambers were enriched in the appropriate nutrient by applying a concentrated dosing solution of either dibasic dodecahydrate sodium phosphate, anhydrous sodium nitrate, solid crystal urea, or liquid ammonium hydroxide respectively to elevate concentrations above ambient levels. The mesocosms were treated and sampled approximately every 24 hours over a 72-hour period (Time 0, Time 24, Time 48, Time 72). May and July 2021 mesocosm were also sampled a week from the initial dosing (T240). Water quality, phytoplankton, cyanotoxin, and environmental DNA (eDNA) samples were collected before and after dosing each day. The current dataset contains only the phytoplankton data including absolute and relative abundance measures at the genus to species level as natural units (NU/mL), cell densities (cells/mL), and biovolumes (um3/mL).

An interdisciplinary and multiagency study was undertaken to study harmful algal bloom (HAB) dynamics on the Caloosahatchee River, which drains to the west from Lake Okeechobee into the Gulf of Mexico. Algae and cyanobacteria play crucial roles in aquatic ecosystems, but under favorable environmental conditions certain taxa may experience population growth booms resulting in HABs. Four independent mesocosm experiments were conducted in September 2019, June 2020, September 2020, and February 2021 to capture natural temporal variability in water quality and phytoplankton assemblages. The experimental installation consisted of three floating metal cradles each containing four fiberglass chambers filled with native river water. The twelve chambers were assigned to one of four treatments: phosphate (P), nitrate (N), ammonium (A), or control (C) – each with 3 replicates. The P, N, and A treatment chambers were enriched by applying a concentrated dosing solution of either dibasic dodecahydrate sodium phosphate, anhydrous sodium nitrate, or liquid ammonium hydroxide respectively to elevate concentrations above ambient levels. The mesocosms were treated and sampled over a 72-hour period (Time 0, Time 24, Time 48, Time 72). This dataset contains phytoplankton absolute and relative abundance measures at the genus level as natural units (NU/mL), cell densities (cells/mL), and biovolumes (um3/mL).

Malheur Lake in southeastern Oregon is a shallow, freshwater lake that provides valuable habitat for birds along the Pacific Flyway. The lake was in a turbid state for multiple decades, and past studies documented high suspended-sediment concentrations, high nutrient concentrations, and low light infiltration through the water column. Experimental restoration trials were conducted in 2021 and 2023 to determine if wave reduction barriers, flocculation, or lakebed hardening were viable restoration options to reduce suspended sediment concentrations and increase light infiltration. Mesocosms were installed in Malheur Lake along a north to south transect, and they were constructed with wire fencing and string reinforced plastic. The water quality was manipulated inside the mesocosm with one or more of the treatments while exposing the water to environmental conditions. Each week during the study period in 2021 and 2023, water-quality data were collected from inside and outside of each mesocosm. Water-quality parameters (including water temperature, specific conductance, turbidity, pH, and chlorophyll-a) were collected with a calibrated YSI 6-series water-quality monitor. Photosynthetically active radiation (PAR) data were collected from the top to the bottom of the water column inside each mesocosm with a LI-COR LI-192 sensor. In June 2021, phytoplankton samples were collected once from each mesocosm. For each sample collected, the phytoplankton were reported to the lowest taxonomic unit. Phytoplankton biovolume, algal cell concentration, and algal biomass concentration are included. All phytoplankton data were generated by PhycoTech, Inc. This data release includes three comma-separated values (.csv) files and metadata. The first CSV file includes water-quality and PAR data collected from the mesocosms in 2021 and 2023. The second CSV file includes all of the taxonomic, biovolume, and density information for the phytoplankton samples that were collected from the mesocosms in June 2021. The third CSV file includes the 55 unique taxa identified in the phytoplankton samples.

We used mesocosm experiments to compare coarse filter-large water volume samples (hereafter large volume filter samples) vs. fine filter-small water volume samples (hereafter small volume filter samples) for detection and quantification of rainbow trout (Oncorhynchus mykiss). We report the quantity of rainbow trout DNA detected using large and small water volume sampling approaches under control (no fish) and treatment (1 fish) conditions.

Benthic macrofauna community data, measured water quality parameters, and benthic index calculations from Pensacola Bay, 2016-2017. This dataset is associated with the following publication: Paul, J., J. Nestlerode, and B. Jarvis. Evaluating the effectiveness of M-AMBI with other biotic indexes in a temperate estuary. MARINE POLLUTION BULLETIN. Elsevier Science Ltd, New York, NY, USA, 193: 10, (2023).

Stream water chemistry and benthic macroinvertebrate data collected in the North Fork of Clear Creek and Clear Creek, CO, USA before and after the diversion and treatment of acid mine drainage by a high-density sludge lime process water treatment plant. Stream water chemistry and benthic macroinvertebrate samples were collected from November 2011 through October 2019 at 6 sites located above and below the North Clear Creek Water Treatment Plant (NCCWTP). The NCCWTP became fully operational in September 2017. Measured water chemistry included pH, conductivity, alkalinity, ferrous iron, total and dissolved concentrations of metals and major geochemical cations, and dissolved organic carbon. Replicate (n=5) benthic macroinvertebrate samples were collected using a 0.1 square meter Hess sampler at targeted riffle habitats among sites. Benthic samples were processed from detrital material in the laboratory using a subsampling technique to reach 300+ invertebrates, and identified to the lowest taxonomic resolution possible, typically to genus (except for chironomids that were identified to subfamily).

Stream water chemistry and benthic macroinvertebrate data collected in the North Fork of Clear Creek and Clear Creek, CO, USA before and after the diversion and treatment of acid mine drainage by a high-density sludge lime process water treatment plant. Stream water chemistry and benthic macroinvertebrate samples were collected from November 2011 through October 2019 at 6 sites located above and below the North Clear Creek Water Treatment Plant (NCCWTP). The NCCWTP became fully operational in September 2017. Measured water chemistry included pH, conductivity, alkalinity, ferrous iron, total and dissolved concentrations of metals and major geochemical cations, and dissolved organic carbon. Replicate (n=5) benthic macroinvertebrate samples were collected using a 0.1 square meter Hess sampler at targeted riffle habitats among sites. Benthic samples were processed from detrital material in the laboratory using a subsampling technique to reach 300+ invertebrates, and identified to the lowest taxonomic resolution possible, typically to genus (except for chironomids that were identified to subfamily).