24 results on '"Blake A. Schaeffer"'
Search Results
2. Identifying lakes at risk of toxic cyanobacterial blooms using satellite imagery and field surveys across the United States
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Amalia M. Handler, Jana E. Compton, Ryan A. Hill, Scott G. Leibowitz, and Blake A. Schaeffer
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Environmental Engineering ,Environmental Chemistry ,Pollution ,Waste Management and Disposal - Published
- 2023
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Catalog
3. Satellite and in situ cyanobacteria monitoring: Understanding the impact of monitoring frequency on management decisions
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Natalie Reynolds, Blake A. Schaeffer, Lucie Guertault, and Natalie G. Nelson
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Water Science and Technology - Published
- 2023
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4. Potential for commercial PlanetScope satellites in oil response monitoring
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Blake A. Schaeffer, Peter Whitman, Robyn Conmy, Wilson Salls, Megan Coffer, David Graybill, and Marie C. Lebrasse
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Gulf of Mexico ,Mississippi ,Petroleum ,Petroleum Pollution ,Aquatic Science ,Oceanography ,Pollution ,United States ,Water Pollutants, Chemical ,Environmental Monitoring - Abstract
Extraction of petroleum oil resources may result in oil spills in the aquatic environment. Active and passive satellites are generally limited in either spatial coverage, temporal revisit periods, or spatial resolution when tracking surface oil slicks. PlanetScope passive satellites are reported to have near daily global coverage at a resolution of 3.5 m at nadir. These satellites may complement monitoring and fill temporal gaps by leveraging sun glint caused by the nadir viewing angle. Here, we demonstrate potential for PlanetScope satellite usage by investigating overpass timing and sun glint intensity. The United States potential for use was greatest during summer solstice and at lower latitudes. When combined with other high-resolution active and passive satellites, PlanetScope coverage added an average of 86.3 days each year from January 2018 through December 2020, as demonstrated at the Mississippi Canyon Block 20 Saratoga Platform site in the Gulf of Mexico. more...
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- 2022
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5. Property values and cyanobacterial algal blooms: Evidence from satellite monitoring of Inland Lakes
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Jiarui Zhang, Daniel J. Phaneuf, and Blake A. Schaeffer
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Economics and Econometrics ,General Environmental Science - Published
- 2022
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6. Satellite-derived cyanobacteria frequency and magnitude in headwaters & near-dam reservoir surface waters of the Southern U.S
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Amber R, Ignatius, S Thomas, Purucker, Blake A, Schaeffer, Kurt, Wolfe, Erin, Urquhart, and Deron, Smith
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Satellite Imagery ,Lakes ,Environmental Engineering ,Harmful Algal Bloom ,Environmental Chemistry ,Hydrology ,Cyanobacteria ,Pollution ,Waste Management and Disposal ,Environmental Monitoring - Abstract
Reservoirs are dominant features of the modern hydrologic landscape and provide vital services. However, the unique morphology of reservoirs can create suitable conditions for excessive algae growth and associated cyanobacteria blooms in shallow in-flow reservoir locations by providing warm water environments with relatively high nutrient inputs, deposition, and nutrient storage. Cyanobacteria harmful algal blooms (cyanoHAB) are costly water management issues and bloom recurrence is associated with economic costs and negative impacts to human, animal, and environmental health. As cyanoHAB occurrence varies substantially within different regions of a water body, understanding in-lake cyanoHAB spatial dynamics is essential to guide reservoir monitoring and mitigate potential public exposure to cyanotoxins. Cloud-based computational processing power and high temporal frequency of satellites enables advanced pixel-based spatial analysis of cyanoHAB frequency and quantitative assessment of reservoir headwater in-flows compared to near-dam surface waters of individual reservoirs. Additionally, extensive spatial coverage of satellite imagery allows for evaluation of spatial trends across many dozens of reservoir sites. Surface water cyanobacteria concentrations for sixty reservoirs in the southern U.S. were estimated using 300 m resolution European Space Agency (ESA) Ocean and Land Colour Instrument (OLCI) satellite sensor for a five year period (May 2016-April 2021). Of the reservoirs studied, spatial analysis of OLCI data revealed 98% had more frequent cyanoHAB occurrence above the concentration of100,000 cells/mL in headwaters compared to near-dam surface waters (P0.001). Headwaters exhibited greater seasonal variability with more frequent and higher magnitude cyanoHABs occurring mid-summer to fall. Examination of reservoirs identified extremely high concentration cyanobacteria events (1,000,000 cells/mL) occurring in 70% of headwater locations while only 30% of near-dam locations exceeded this threshold. Wilcoxon signed-rank tests of cyanoHAB magnitudes using paired-observations (dates with observations in both a reservoir's headwater and near-dam locations) confirmed significantly higher concentrations in headwater versus near-dam locations (p0.001). more...
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- 2022
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7. Mobile device application for monitoring cyanobacteria harmful algal blooms using Sentinel-3 satellite Ocean and Land Colour Instruments
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Sean W. Bailey, Michael Galvin, Robyn N. Conmy, Rajbir Parmar, Ross S. Lunetta, Kurt Wolfe, P. Jeremy Werdell, Amber R. Ignatius, Erin A. Urquhart, Darryl J. Keith, Richard P. Stumpf, Blake A. Schaeffer, and John M. Johnston more...
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Environmental Engineering ,010504 meteorology & atmospheric sciences ,Ecological health ,business.industry ,Ecological Modeling ,Environmental resource management ,010501 environmental sciences ,01 natural sciences ,Algal bloom ,Article ,Water quality management ,Software deployment ,Environmental science ,Satellite ,Satellite imagery ,Water quality ,business ,Mobile device ,Software ,0105 earth and related environmental sciences - Abstract
Cyanobacterial harmful algal blooms (cyanoHAB) cause human and ecological health problems in lakes worldwide. The timely distribution of satellite-derived cyanoHAB data is necessary for adaptive water quality management and for targeted deployment of water quality monitoring resources. Software platforms that permit timely, useful, and cost-effective delivery of information from satellites are required to help managers respond to cyanoHABs. The Cyanobacteria Assessment Network (CyAN) mobile device application (app) uses data from the European Space Agency Copernicus Sentinel-3 satellite Ocean and Land Colour Instrument (OLCI) in near real-time to make initial water quality assessments and quickly alert managers to potential problems and emerging threats related to cyanobacteria. App functionality and satellite data were validated with 25 state health advisories issued in 2017. The CyAN app provides water quality managers with a user-friendly platform that reduces the complexities associated with accessing satellite data to allow fast, efficient, initial assessments across lakes. more...
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- 2018
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8. Spatio-temporal dynamics of inherent optical properties in oligotrophic northern Gulf of Mexico estuaries
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Ike Sari Astuti, Blake A. Schaeffer, Deepak R. Mishra, and Sachidananda Mishra
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geography ,Detritus ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Discharge ,0211 other engineering and technologies ,Imaging spectrometer ,Geology ,Estuary ,IOPS ,02 engineering and technology ,Aquatic Science ,Oceanography ,Atmospheric sciences ,01 natural sciences ,Article ,Environmental science ,Precipitation ,Water quality ,Bay ,021101 geological & geomatics engineering ,0105 earth and related environmental sciences - Abstract
Coastal and estuarine ecosystems provide numerous economic and environmental benefits to society. However, increasing anthropogenic activities and developmental pressure may stress these areas and hamper their ecosystem services. Satellite remote sensing could be used as a tool for monitoring water quality parameters, including inherent optical properties (IOP) in coastal regions. Spatio-temporal information on IOP variability will help in understanding the dynamics of the water quality of estuaries. The objective of this research was to develop a novel hybrid model by combining and parameterizing existing quasi analytical and semi-analytical algorithms to estimate IOPs in four oligotrophic northern Gulf of Mexico Florida estuaries. The hybrid model was applied to above surface remote sensing reflectance data representing the Medium Resolution Imaging Spectrometer (MERIS) and Sentinel-3’s Ocean and Land Colour Instrument (OCLI) bands. The hybrid model produced a root means squared error (RMSE) of 0.32 m(−1) (13.95% NRMSE) for total absorption (a(t)), 0.21 m(−1) (7.61% NRMSE) for detritus-gelbstoff absorption (a(dg)), and 0.09 m(−1) (22.77% NRMSE) for phytoplankton pigment absorption (a(phi)). Results showed that absorption by detritus and gelbstoff (a(dg)) dominates the water in these estuaries. Monthly IOP variability in 2010 revealed that compared to other estuaries, magnitudes of IOPs was the highest in Pensacola Bay and therefore the highest attenuation. Findings also indicated that river discharge and precipitation predominantly govern the IOP variations in all four estuaries, showing an increase in IOP values following the high flow period. The hybrid model improved IOP retrieval in these low chlorophyll-a (Chl-a) estuaries where the existing spectral decomposition models did not perform satisfactorily. more...
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- 2018
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9. Assessing cyanobacterial frequency and abundance at surface waters near drinking water intakes across the United States
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P. Jeremy Werdell, Richard P. Stumpf, Katherine Foreman, John A. Darling, Ryan J. Albert, Erin A. Urquhart, Keith A. Loftin, Megan M. Coffer, Blake A. Schaeffer, and Alex Porteous
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Environmental Engineering ,0208 environmental biotechnology ,Population ,02 engineering and technology ,010501 environmental sciences ,Cyanobacteria ,01 natural sciences ,Algal bloom ,Abundance (ecology) ,Satellite imagery ,education ,Waste Management and Disposal ,0105 earth and related environmental sciences ,Water Science and Technology ,Civil and Structural Engineering ,education.field_of_study ,Drinking Water ,Ecological Modeling ,Eutrophication ,Pollution ,United States ,020801 environmental engineering ,Lakes ,Environmental science ,Water treatment ,Water quality ,Physical geography ,Bloom ,Surface water ,Environmental Monitoring - Abstract
This study presents the first large-scale assessment of cyanobacterial frequency and abundance of surface water near drinking water intakes across the United States. Public water systems serve drinking water to nearly 90% of the United States population. Cyanobacteria and their toxins may degrade the quality of finished drinking water and can lead to negative health consequences. Satellite imagery can serve as a cost-effective and consistent monitoring technique for surface cyanobacterial blooms in source waters and can provide drinking water treatment operators information for managing their systems. This study uses satellite imagery from the European Space Agency's Ocean and Land Colour Instrument (OLCI) spanning June 2016 through April 2020. At 300-m spatial resolution, OLCI imagery can be used to monitor cyanobacteria in 685 drinking water sources across 285 lakes in 44 states, referred to here as resolvable drinking water sources. First, a subset of satellite data was compared to a subset of responses (n = 84) submitted as part of the U.S. Environmental Protection Agency's fourth Unregulated Contaminant Monitoring Rule (UCMR 4). These UCMR 4 qualitative responses included visual observations of algal bloom presence and absence near drinking water intakes from March 2018 through November 2019. Overall agreement between satellite imagery and UCMR 4 qualitative responses was 94% with a Kappa coefficient of 0.70. Next, temporal frequency of cyanobacterial blooms at all resolvable drinking water sources was assessed. In 2019, bloom frequency averaged 2% and peaked at 100%, where 100% indicated a bloom was always present at the source waters when satellite imagery was available. Monthly cyanobacterial abundances were used to assess short-term trends across all resolvable drinking water sources and effect size was computed to provide insight on the number of years of data that must be obtained to increase confidence in an observed change. Generally, 2016 through 2020 was an insufficient time period for confidently observing changes at these source waters; on average, a decade of satellite imagery would be required for observed environmental trends to outweigh variability in the data. However, five source waters did demonstrate a sustained short-term trend, with one increasing in cyanobacterial abundance from June 2016 to April 2020 and four decreasing. more...
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- 2021
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10. A method for examining temporal changes in cyanobacterial harmful algal bloom spatial extent using satellite remote sensing
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P. Jeremy Werdell, Richard P. Stumpf, Blake A. Schaeffer, Erin A. Urquhart, and Keith A. Loftin
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Inland waters ,Time Factors ,010504 meteorology & atmospheric sciences ,Harmful Algal Bloom ,Plant Science ,010501 environmental sciences ,Aquatic Science ,Cyanobacteria ,01 natural sciences ,Algal bloom ,California ,Article ,World health ,Harmful algal blooms ,0105 earth and related environmental sciences ,Geography ,Remote sensing ,MERIS ,Medium resolution ,Oceanography ,Remote sensing (archaeology) ,Satellite remote sensing ,Remote Sensing Technology ,Florida ,Environmental science ,Satellite ,Spatial extent ,Bloom - Abstract
Cyanobacterial harmful algal blooms (CyanoHAB) are thought to be increasing globally over the past few decades, but relatively little quantitative information is available about the spatial extent of blooms. Satellite remote sensing provides a potential technology for identifying cyanoHABs in multiple water bodies and across geo-political boundaries. An assessment method was developed using MEdium Resolution Imaging Spectrometer (MERIS) imagery to quantify cyanoHAB surface area extent, transferable to different spatial areas, in Florida, Ohio, and California for the test period of 2008 to 2012. Temporal assessment was used to evaluate changes in satellite resolvable inland waterbodies for each state of interest. To further assess cyanoHAB risk within the states, the World Health Organization’s (WHO) recreational guidance level thresholds were used to categorize surface area of cyanoHABs into three risk categories: low, moderate, and high-risk bloom area. Results showed that in Florida, the area of cyanoHABs increased largely due to observed increases in high-risk bloom area. California exhibited a slight decrease in cyanoHAB extent, primarily attributed to decreases in Northern California. In Ohio (excluding Lake Erie), little change in cyanoHAB surface area was observed. This study uses satellite remote sensing to quantify changes in inland cyanoHAB surface area across numerous water bodies within an entire state. The temporal assessment method developed here will be relevant into the future as it is transferable to the Ocean Land Colour Instrument (OLCI) on Sentinel-3A/3B missions. more...
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- 2017
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11. Characterizing light attenuation within Northwest Florida Estuaries: Implications for RESTORE Act water quality monitoring
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Joseph P. Schubauer-Berigan, Robyn N. Conmy, John C. Lehrter, Jessica Aukamp, Blake A. Schaeffer, Richard M. Greene, and Allyn Duffy
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Light ,010504 meteorology & atmospheric sciences ,010501 environmental sciences ,Aquatic Science ,Oceanography ,01 natural sciences ,Article ,law.invention ,law ,Water Quality ,Environmental monitoring ,Phytoplankton ,Petroleum Pollution ,Seawater ,Ecosystem ,Water pollution ,0105 earth and related environmental sciences ,Hydrology ,geography ,geography.geographical_feature_category ,Water Pollution ,Estuary ,Pollution ,Colored dissolved organic matter ,Florida ,CLARITY ,Environmental science ,Water quality ,Estuaries ,Environmental Monitoring - Abstract
Water Quality (WQ) condition is based on ecosystem stressor indicators (e.g. water clarity) which are biogeochemically important and critical when considering the Deepwater Horizon oil spill restoration efforts under the 2012 RESTORE Act. Nearly all of the proposed RESTORE projects list restoring WC as a goal, but 90% neglect water clarity. Here, dynamics of optical constituents impacting clarity are presented from a 2009–2011 study within Pensacola, Choctawhatchee, St. Andrew and St. Joseph estuaries (targeted RESTORE sites) in Northwest Florida. Phytoplankton were the smallest contribution to total absorption (a(t-w)PAR) at 412 nm (5–11%), whereas colored dissolved organic matter was the largest (61–79%). Estuarine a(t-w)PAR was significantly related to light attenuation (K(d)PAR), where individual contributors to clarity and the influence of climatic events were discerned. Provided are conversion equations demonstrating interoperability of clarity indicators between traditional State-measured WQ measures (e.g. secchi disc), optical constituents, and even satellite remote sensing for obtaining baseline assessments. more...
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- 2017
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12. Bio-optical water quality dynamics observed from MERIS in Pensacola Bay, Florida
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John C. Lehrter, Marcus W. Beck, Richard M. Greene, Blake A. Schaeffer, Chengfeng Le, Michael C. Murrell, Chuanmin Hu, and James D. Hagy
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0106 biological sciences ,Hydrology ,geography ,Chlorophyll a ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Discharge ,010604 marine biology & hydrobiology ,Estuary ,Aquatic Science ,Particulates ,Oceanography ,01 natural sciences ,Wind speed ,chemistry.chemical_compound ,Colored dissolved organic matter ,chemistry ,Environmental science ,Water quality ,Bay ,0105 earth and related environmental sciences - Abstract
Observed bio-optical water quality data collected from 2009 to 2011 in Pensacola Bay, Florida were used to develop empirical remote sensing retrieval algorithms for chlorophyll a (Chla), colored dissolved organic matter (CDOM), and suspended particulate matter (SPM). Time-series of the three bio-optical water quality variables were generated from MEdium Resolution Imaging Spectrometer (MERIS) observations from 2003 to 2011. Bio-optical water quality in this estuary exhibited spatial and temporal variations that were correlated to river discharge and wind. Both annual mean and monthly mean bio-optical water quality variables were positively correlated to river discharge. Monthly mean bio-optical water quality variables were also positively correlated to wind speed and wind density (defined by the number of days with daily mean wind speed > 3 m s −1 in a month) over this estuary. These results indicate that bio-optical water quality dynamics in this estuary are vulnerable to changes in river discharge and river constituent loads and local weather conditions such as winter storms and hurricanes. more...
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- 2016
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13. Performance across WorldView-2 and RapidEye for reproducible seagrass mapping
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Peter J. Whitman, Victoria Hill, Richard C. Zimmerman, Jiang Li, Megan M. Coffer, Kazi Aminul Islam, and Blake A. Schaeffer
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010504 meteorology & atmospheric sciences ,biology ,Aerial survey ,Contextual image classification ,0208 environmental biotechnology ,Atmospheric correction ,Soil Science ,Geology ,Image processing ,02 engineering and technology ,Spectral bands ,biology.organism_classification ,01 natural sciences ,Article ,020801 environmental engineering ,Seagrass ,Environmental science ,Satellite ,Computers in Earth Sciences ,Image resolution ,0105 earth and related environmental sciences ,Remote sensing - Abstract
Satellite remote sensing offers an effective remedy to challenges in ground-based and aerial mapping that have previously impeded quantitative assessments of global seagrass extent. Commercial satellite platforms offer fine spatial resolution, an important consideration in patchy seagrass ecosystems. Currently, no consistent protocol exists for image processing of commercial data, limiting reproducibility and comparison across space and time. Additionally, the radiometric performance of commercial satellite sensors has not been assessed against the dark and variable targets characteristic of coastal waters. This study compared data products derived from two commercial satellites: DigitalGlobe's WorldView-2 and Planet's RapidEye. A single scene from each platform was obtained at St. Joseph Bay in Florida, USA, corresponding to a November 2010 field campaign. A reproducible processing regime was developed to transform imagery from basic products, as delivered from each company, into analysis-ready data usable for various scientific applications. Satellite-derived surface reflectances were compared against field measurements. WorldView-2 imagery exhibited high disagreement in the coastal blue and blue spectral bands, chronically overpredicting. RapidEye exhibited better agreement than WorldView-2, but overpredicted slightly across all spectral bands. A deep convolutional neural network was used to classify imagery into deep water, land, submerged sand, seagrass, and intertidal classes. Classification results were compared to seagrass maps derived from photointerpreted aerial imagery. This study offers the first radiometric assessment of WorldView-2 and RapidEye over a coastal system, revealing inherent calibration issues in shorter wavelengths of WorldView-2. Both platforms demonstrated as much as 97% agreement with aerial estimates, despite differing resolutions. Thus, calibration issues in WorldView-2 did not appear to interfere with classification accuracy, but could be problematic if estimating biomass. The image processing routine developed here offers a reproducible workflow for WorldView-2 and RapidEye imagery, which was tested in two additional coastal systems. This approach may become platform independent as more sensors become available. more...
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- 2020
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14. Quantifying national and regional cyanobacterial occurrence in US lakes using satellite remote sensing
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John A. Darling, Wilson B. Salls, Blake A. Schaeffer, Erin A. Urquhart, and Megan M. Coffer
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0106 biological sciences ,Inland waters ,General Decision Sciences ,010501 environmental sciences ,Cyanobacteria ,010603 evolutionary biology ,01 natural sciences ,Algal bloom ,Article ,Harmful algal blooms ,medicine ,Ecology, Evolution, Behavior and Systematics ,0105 earth and related environmental sciences ,Ecology ,Baseline (sea) ,Sampling (statistics) ,Remote sensing ,Seasonality ,medicine.disease ,Snow ,Water quality ,Environmental science ,Satellite ,Physical geography ,Bloom - Abstract
Cyanobacterial harmful algal blooms are the most common form of harmful algal blooms in freshwater systems throughout the world. However, in situ sampling of cyanobacteria in inland lakes is limited both spatially and temporally. Satellite data has proven to be an effective tool to monitor cyanobacteria in freshwater lakes across the United States. This study uses data from the European Space Agency Envisat MEdium Resolution Imaging Spectrometer and the Sentinel-3 Ocean and Land Color Instrument to provide a national overview of the percentage of lakes experiencing a cyanobacterial bloom on a weekly basis for 2008–2011, 2017, and 2018. A total of 2321 lakes across the contiguous United States were included in the analysis. We examined four different thresholds to define when a waterbody is classified as experiencing a bloom. Across these four thresholds, we explored variability in bloom percentage with changes in seasonality and lake size. As a validation of algorithm performance, we analyzed the agreement between satellite observations and previously established ecological patterns, although data availability in the wintertime limited these comparisons on a year-round basis. Changes in cyanobacterial bloom percentage at the national scale followed the well-known temporal pattern of freshwater blooms. The percentage of lakes experiencing a bloom increased throughout the year, reached a maximum in fall, and decreased through the winter. Wintertime data, particularly in northern regions, were consistently limited due to snow and ice cover. With the exception of the Southeast and South, regional patterns mimicked patterns found at the national scale. The Southeast and South exhibited an unexpected pattern as cyanobacterial bloom percentage reached a maximum in the winter rather than the summer. Lake Jesup in Florida was used as a case study to validate this observed pattern against field observations of chlorophyll a. Results from this research establish a baseline of annual occurrence of cyanobacterial blooms in inland lakes across the United States. In addition, methods presented in this study can be tailored to fit the specific requirements of an individual system or region. more...
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- 2020
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15. Evaluation of cyanobacteria cell count detection derived from MERIS imagery across the eastern USA
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Ross S. Lunetta, Mark S. Murphy, Blake A. Schaeffer, Richard P. Stumpf, Scott Jacobs, and Darryl J. Keith
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Cyanobacteria ,biology ,Imaging spectrometer ,Soil Science ,Climate change ,Geology ,Spectral bands ,biology.organism_classification ,Algal bloom ,Phycocyanin ,Environmental science ,Satellite imagery ,Water quality ,Computers in Earth Sciences ,Remote sensing - Abstract
Inland waters across the United States (US) are at potential risk for increased outbreaks of toxic cyanobacteria blooms events resulting from elevated water temperatures and extreme hydrologic events attributable to climate change and increased nutrient loadings associated with intensive agricultural practices. Current monitoring efforts are limited in scope due to resource limitations, analytical complexity, and data integration efforts. The goals of this study were to validate an algorithm for satellite imagery that could potentially be used to monitor surface cyanobacteria events in near real-time to provide a compressive monitoring capability for freshwater lakes (> 100 ha). The algorithm incorporated narrow spectral bands specific to the European Space Agency's (ESA's) MEdium Resolution Imaging Spectrometer (MERIS) instrument that were optimally oriented at phytoplankton pigment absorption features including phycocyanin at 620 nm. A validation of derived cyanobacteria cell counts was performed using available in situ data assembled from existing monitoring programs across eight states in the eastern US over a 39-month period (2009–2012). Results indicated that MERIS provided robust estimates for low (10,000–109,000 cells/mL) and very high (> 1,000,000 cells/mL) cell enumeration ranges (approximately 90% and 83%, respectively). However, the results for two intermediate ranges (110,000–299,000 and 300,000–1,000,000 cells/mL) were substandard, at approximately 28% and 40%, respectively. The confusion associated with intermediate cyanobacteria cell count ranges was largely attributed to the lack of available taxonomic data and distinction of natural counting units for the in situ measurements that would have facilitated conversions between cell counts and cell volumes. The results of this study document the potential for using MERIS-derived cyanobacteria cell count estimates to monitor freshwater lakes (> 100 ha) across the eastern US. more...
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- 2015
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16. Estimation of diffuse attenuation of ultraviolet light in optically shallow Florida Keys waters from MODIS measurements
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David L. Jones, Chuanmin Hu, Brian B. Barnes, Pamela Hallock, John C. Lehrter, Blake A. Schaeffer, Nelson Melo, Susanne E. Craig, Richard G. Zepp, and Jennifer Cannizzaro
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Attenuation ,Soil Science ,Geology ,medicine.disease_cause ,Wavelength ,Colored dissolved organic matter ,Waves and shallow water ,Water column ,Attenuation coefficient ,Ultraviolet light ,medicine ,Environmental science ,Computers in Earth Sciences ,Ultraviolet ,Remote sensing - Abstract
Diffuse attenuation of solar light (Kd, m− 1) determines the percentage of light penetrating the water column and available for benthic organisms. Therefore, Kd can be used as an index of water quality for coastal ecosystems that are dependent on photosynthesis, such as the coral reef environments of the Florida Reef Tract. Ultraviolet (UV) light reaching corals can lead to reductions in photosynthetic capacity as well as DNA damage. Unfortunately, field measurements of Kd(UV) lack sufficient spatial and temporal coverage to derive statistically meaningful patterns, and it has been notoriously difficult to derive Kd in optically shallow waters from remote sensing due to bottom contamination. Here we describe an approach to derive Kd(UV) in optically shallow waters of the Florida Keys using variations in the spectral shape of MODIS-derived surface reflectance. The approach used a principal component analysis and stepwise multiple regression to parsimoniously select modes of variance in MODIS-derived reflectance data that best explained variance in concurrent in situ Kd(UV) measurements. The resulting models for Kd(UV) retrievals in waters 1–30 m deep showed strong positive relationships between derived and measured parameters [e.g., for Kd(305) ranging from 0.28 to 3.27 m− 1; N = 29; R2 = 0.94]. The predictive capabilities of these models were further tested, also showing acceptable performance [for Kd(305), R2 = 0.92; bias = − 0.02 m− 1; URMS = 23%]. The same approach worked reasonably well in deriving the absorption coefficient of colored dissolved organic matter (CDOM) in UV wavelengths [ag(UV), m− 1], as Kd(UV) is dominated by ag(UV). Application of the approach to MODIS data showed different spatial and temporal Kd(305) patterns than the Kd(488) patterns derived from a recently validated semi-analytical approach, suggesting that different mechanisms are controlling Kd in the UV and in the visible. Given the importance of water clarity and light availability to shallow-water flora and fauna, the new Kd(UV) and ag(UV) data products provide unprecedented information for assessing and monitoring of coral reef health, and could further assist ongoing regional protection efforts. more...
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- 2014
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17. MODIS-derived spatiotemporal water clarity patterns in optically shallow Florida Keys waters: A new approach to remove bottom contamination
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Zhongping Lee, Chuanmin Hu, Brian B. Barnes, John C. Lehrter, David Palandro, and Blake A. Schaeffer
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Hydrology ,geography ,geography.geographical_feature_category ,biology ,Multispectral image ,Soil Science ,Geology ,Soil science ,Coral reef ,biology.organism_classification ,Waves and shallow water ,Seagrass ,Water column ,Ocean color ,Environmental science ,Satellite ,Water quality ,Computers in Earth Sciences ,Remote sensing - Abstract
article i nfo Retrievals of water quality parameters from satellite measurements over optically shallow waters have been problematic due to bottom contamination of the signals. As a result, large errors are associated with derived water column properties. These deficiencies greatly reduce the ability to use satellites to assess the shallow water environments around coral reefs and seagrass beds. Here, a modified version of an existing algorithm is used to derive multispectral diffuse attenuation coefficient (Kd) from MODIS/Aqua measurements over op- tically shallow waters in the Florida Keys. Results were validated against concurrent in situ data (Kd(488) from 0.02 to 0.20 m −1 , N = 22, R 2 = 0.68, Mean Ratio = 0.93, unbiased RMS = 31%), and showed signifi more...
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- 2013
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18. Assessment of satellite-derived diffuse attenuation coefficients and euphotic depths in south Florida coastal waters
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Nelson Melo, Chuanmin Hu, Brian B. Barnes, Blake A. Schaeffer, Brian E. Lapointe, Jun Zhao, David English, and Frank E. Muller-Karger
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Attenuation ,Soil Science ,Geology ,IOPS ,Euphotic depth ,SeaWiFS ,Oceanography ,Ocean color ,Attenuation coefficient ,Visible range ,Environmental science ,Photic zone ,Computers in Earth Sciences ,Remote sensing - Abstract
Optical data collected in coastal waters off South Florida and in the Caribbean Sea between January 2009 and December 2010 were used to evaluate products derived with three bio-optical inversion algorithms applied to MODIS/Aqua, MODIS/Terra, and SeaWiFS satellite observations. The products included the diffuse attenuation coefficient at 490 nm (Kd_490) and for the visible range (Kd_PAR), and euphotic depth (Zeu, corresponding to 1% of the surface incident photosynthetically available radiation or PAR). Above-water hyperspectral reflectance data collected over optically shallow waters of the Florida Keys between June 1997 and August 2011 were used to help understand algorithm performance over optically shallow waters. The in situ data covered a variety of water types in South Florida and the Caribbean Sea, ranging from deep clear waters, turbid coastal waters, and optically shallow waters (Kd_490 range of ~ 0.03–1.29 m− 1). An algorithm based on Inherent Optical Properties (IOPs) showed the best performance (RMSD more...
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- 2013
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19. An analysis of diffuse light attenuation in the northern Gulf of Mexico hypoxic zone using the SeaWiFS satellite data record
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Michael C. Murrell, Janis C. Kurtz, Richard W. Gould, John C. Lehrter, Blake A. Schaeffer, Geoffrey A. Sinclair, and Diane F. Yates
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Pycnocline ,geography ,geography.geographical_feature_category ,Continental shelf ,Attenuation ,Soil Science ,Geology ,Water column ,SeaWiFS ,Oceanography ,Photosynthetically active radiation ,Sediment–water interface ,Photic zone ,Computers in Earth Sciences ,Remote sensing - Abstract
article i nfo Article history: The Sea-viewing Wide Field-of-View Sensor (SeaWiFS) derived diffuse light attenuation along the Louisiana continental shelf (LCS) was examined at monthly scales from 1998 to 2007 to characterize temporal and spa- tial patterns, and responsible physical forcing conditions. The SeaWiFS diffuse light attenuation ranged from 0.10 to 2.64 m �1 . Stepwise multiple linear regression analysis suggested that spatial and temporal patterns in diffuse light attenuation were influenced by wind speed, nutrient loading, and river discharge from the Mississippi and Atchafalaya River Basin. SeaWiFS daily integrated surface photosynthetically active radiation (PAR, 400-700 nm) and diffuse light attenuation were used to calculate the absolute PAR and percentage of surface PAR that reached the sediment water interface (SWI) on the LCS. Large portions of the LCS were eu- photic to the SWI especially during April and May. This finding implied that significant primary production was possible beneath the pycnocline during spring and early summer. In addition, this study was the first to demonstrate that the euphotic depth was correlated to the depth at which the water column turned hyp- oxic on the LCS. The development of hypoxic waters may be influenced by decreased light availability below the pycnocline in addition to aforementioned physical forcing. more...
- Published
- 2011
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20. Tropical instability wave interactions within the Galápagos Archipelago
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Lian Xie, Blake A. Schaeffer, S. Banks, Yanyun Liu, Daniel Kamykowski, W.V. Sweet, and John M. Morrison
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geography ,geography.geographical_feature_category ,Buoy ,Tropical instability waves ,Aquatic Science ,Oceanography ,Sea surface temperature ,SeaWiFS ,Archipelago ,Upwelling ,Thermocline ,Geology ,Argo - Abstract
The effects of tropical instability waves (TIW) within the eastern equatorial Pacific during the boreal fall of 2005 were observed in multiple data sets. The TIW cause oscillations of the sea surface temperature (SST), meridional currents ( V ), and 20 °C isotherm (thermocline). A particularly strong 3-wave packet of ∼15-day period TIW passed through the Galapagos Archipelago in Sep and Oct 2005 and their effects were recorded by moored near-surface sensors. Repeat Argo profiles in the archipelago showed that the large temperature (>5 °C) oscillations that occurred were associated with a vertical adjustment within the water column. Numerical simulations report strong oscillations and upwelling magnitudes of ∼5.0 m d −1 near the Tropical Atmosphere Ocean (TAO) buoy at 0°, 95°W and in the Archipelago at 92°W and 90°W. A significant biological response to the TIW passage was observed within the archipelago. Chlorophyll a measured by the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) increased by >30% above 1998–2007 mean concentrations within the central archipelago. The increases coincide with coldest temperatures and the much larger increases within the archipelago as compared to those of 95°W indicate that TIW induced upwelling over the island platform itself brought more iron-enriched upwelling waters into the euphotic zone. more...
- Published
- 2009
- Full Text
- View/download PDF
21. Diel vertical migration thresholds of Karenia brevis (Dinophyceae)
- Author
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Geoff Sinclair, Daniel Kamykowski, Edward J. Milligan, Laurie McKay, and Blake A. Schaeffer
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Water column ,Nutrient ,biology ,Ecology ,Dinoflagellate ,Phototaxis ,Plant Science ,Karenia brevis ,Aquatic Science ,biology.organism_classification ,Photosynthesis ,Diel vertical migration ,Mesocosm - Abstract
Light and nutrient availability change throughout dinoflagellate diel vertical migration (DVM) and/or with sub-population location in the water column along the west Florida shelf. Typically, the vertical depth of the shelf is greater than the distance a sub-population can vertically migrate during a diel cycle, limiting the ability of a sub-population to photosynthetically fix carbon toward the surface and access nutrients sub-surface. This project investigated changes of Karenia brevis (C.C. Davis) G. Hansen et Moestrup intracellular carbon, nitrogen, internal nitrate (iNO 3 ), free amino acid (FAA), and total lipid concentrations in high-light, nitrate-replete (960 μmol quanta m −2 s −1 , 80 μM NO 3 ), and high-light, nitrate-reduced (960 μmol quanta m −2 s −1 , 3 ) mesocosms. The nitrate-reduced mesocosm had a slowed cell division rate when compared to the nitrate-replete mesocosm. Minimum intracellular carbon, nitrogen, iNO 3 , FAA, and total lipid concentrations during the largest surface sub-population aggregations led to the conclusion that daughter cells resulting from cell division received unequal shares of the parental resources and that this inequality influenced migration behavior. Nutrient reduced daughter cells were more strongly influenced by light and phototaxis for carbon production than their replete same cell division sister cells during vertical migration thus rapidly increasing the fulfillment of constituents through photosynthesis. Vertical migration was consistent with an optimization scheme based on threshold limits through utilization or formation of photosynthate. We propose a simplified conceptual model describing how K. brevis is transported along the benthos of the west Florida shelf from off-shore to on-shore. Dynamic carbon thresholds are also suggested for future DVM modeling efforts on K. brevis populations transported between nitrogen replete and nitrogen reduced environmental conditions. more...
- Published
- 2009
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22. Phytoplankton biomass distribution and identification of productive habitats within the Galapagos Marine Reserve by MODIS, a surface acquisition system, and in-situ measurements
- Author
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William J. Sweet, Stuart Banks, Yanyun Liu, Daniel Kamykowski, Lian Xie, Gene C. Feldman, Anita A. McCulloch, John M. Morrison, and Blake A. Schaeffer
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geography ,Chlorophyll a ,Biomass (ecology) ,geography.geographical_feature_category ,Marine reserve ,Seamount ,Soil Science ,Geology ,Plankton ,chemistry.chemical_compound ,Oceanography ,chemistry ,Phytoplankton ,Upwelling ,Environmental science ,Ecosystem ,Computers in Earth Sciences - Abstract
The Galapagos Marine Reserve (GMR) is one of the most diverse ecosystems in the world. Phytoplankton are the base of the ecosystem food chain for many higher trophic organisms, so identifying phytoplankton biomass distribution is the first step in understanding the dynamic environment for effective management of the GMR. Moderate Resolution Imaging Spectroradiometer (MODIS) and hyperspectral surface acquisition system derived chlorophyll, in-situ chlorophyll fluorescence, nitrate, salinity, and temperature were collected from March 2005 to the onset of a mild El Nino in November 2006. Islands in the eastern GMR, such as San Cristobal and Espanola, are the first to experience impacts of El Nino and southern migration of the Equatorial Front. Productive habitats were defined as surface waters with salinities > 34, temperatures a > 0.4 mg m − 3 . Six temporally variable productive habitats identified were: west of Isabela Island, southwest of Floreana Island, south of Santa Cruz, between Santiago and Santa Cruz Islands, and on the eastern side near San Cristobal Island. Model results coupled with surface acquisition system derived chlorophyll indicated productive habitats may also occur for short periods and at a distance from islands such as when the Equatorial Undercurrent (EUC) and South Equatorial Current (SEC) collide over the seamounts north of Isabela Island. All productive habitats were related to topographic upwelling from the EUC into surface waters. more...
- Published
- 2008
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23. Water mass seasonal variability in the Galápagos Archipelago
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S. Banks, Daniel Kamykowski, Anita A. McCulloch, John M. Morrison, Blake A. Schaeffer, and W.V. Sweet
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geography ,Water mass ,geography.geographical_feature_category ,Equator ,Ocean current ,Aquatic Science ,Oceanography ,Sea surface temperature ,Hydrographic survey ,Archipelago ,Upwelling ,Thermocline ,Geology - Abstract
Three hydrographic surveys were conducted within the Galapagos Archipelago during 2005–2006. The surveys captured the surface properties ( S ) S >34, throughout the archipelago. Equatorial Surface Waters are present west of Isabela, where the EUC upwells as it interacts with the Galapagos platform. They also are found east of the archipelago in the cold tongue, which extends westward from South America, and therefore may be advected by the SEC into the archipelago. The upwelling west of Isabela creates a consistently shallow 20 °C isotherm (thermocline), which remains elevated across the archipelago. Linear extrapolation of the thermocline depth along the equator from 110 to 95°W gives a good approximation of the thermocline depth within the archipelago from 92 to 89°W. more...
- Published
- 2007
- Full Text
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24. Comparison of swimming speed and photophysiological responses to different external conditions among three Karenia brevis strains
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Geoff Sinclair, Daniel Kamykowski, Edward J. Milligan, Laurie McKay, and Blake A. Schaeffer
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biology ,Strain (chemistry) ,Dinoflagellate ,Plant Science ,Aquatic Science ,biology.organism_classification ,Photosynthesis ,Swimming speed ,Light intensity ,Animal science ,Botany ,Autotroph ,Karenia brevis ,Incubation - Abstract
Behavior, growth, and production are integral in the life history of Karenia brevis, an autotrophic, dinoflagellate HAB species, and are important variables in modeling blooms in the Gulf of Mexico. This study compares swimming speeds, growth rates, and photosynthetic responses of recent isolates of K. brevis (specifically the Apalachicola ‐ APA, Manasota ‐ MAN, and Jacksonville ‐ JAX strains) over a range of light intensities and temperatures. Strain swimming speeds were similar and remained fairly constant from 17 to 30 8C, but decreased markedly at 13 8C. Photosynthetic responses of the strains to different acclimated temperatures had opposite trends with APA exhibiting higher electron transport rates (ETR) at higher temperatures and MAN exhibiting higher ETR at lower temperatures. In the light experiments, the cells’ internal physiological state (represented by photosynthetic yield, ETR, and neutral lipid reserves) and swimming capabilities were examined in the dark after 6 h incubations in the radial photosynthetron. For all strains, at initial incubation light intensities swimming speed decreased and ETR increased. As incubation light intensities increased, ETR decreased and swimming speed increased. At the highest incubation light intensities, ETR and swimming speed decreased. Neutral lipids followed a pattern similar to ETR, only lipids peaked after ETR at a light intensity that corresponded to the increase in swimming speed. The results suggest that cells may partition energy selectively depending on the needs of the cell. Information was combined to characterize a generalized species response to light and temperature ranges. # 2006 Elsevier B.V. All rights reserved. more...
- Published
- 2006
- Full Text
- View/download PDF
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