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[Estimation of the risk of drug-related problems in nursing home residents : A retrospective analysis of routine data]. Z Gerontol Geriatr 2023; 56:673-678. [PMID: 36577859 PMCID: PMC10709222 DOI: 10.1007/s00391-022-02152-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 11/29/2022] [Indexed: 12/29/2022]
Abstract
BACKGROUND Polypharmacy and drug-related problems are major challenges in the care and treatment of nursing home residents. Many interventional studies showed disappointing results, which lead to the question if this could also be due to the selection of the target parameters of these studies. MATERIAL AND METHODS A routine data set from six long-term care facilities was retrospectively analyzed. The question is if the recently validated medication risk score (MERIS) is suitable for carrying out a risk assessment in a population of nursing home residents. Associations between MERIS and the dependent variables hospital admissions and falls over 12 months and a weight loss of ≥ 5% over 3 months were examined. RESULTS Out of 495 residents 38.6% (n = 191) have a high risk of drug-related problems according to MERIS. A univariate regression analysis showed a significantly increased risk of hospital admissions (OR 2.2; p < 0.001) and weight loss of ≥ 5% (OR 1.95; p = 0.041) with high MERIS, but no significant association with falls. In the multivariate regression the risk of hospitalization was increased by diabetes mellitus (OR 1.88; p = 0.004), falls in the same period (OR 1.91; p = 0.001), positive MERIS (OR 1.75; p = 0.006) and decreased with stable weight (OR 0.88; p = 0.004). CONCLUSION The results indicate the potential of the score for future research projects and individual risk assessment; however, due to the limitations of retrospective secondary analyses further studies are required.
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Floating Debris in the Northern Gulf of Mexico after Hurricane Katrina. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023. [PMID: 37347705 DOI: 10.1021/acs.est.3c01689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 06/24/2023]
Abstract
Hurricane Katrina (category 5 with maximum wind of 280 km/h when the eye is in the central Gulf of Mexico) made landfall near New Orleans on August 29, 2005, causing millions of cubic meters of disaster debris, severe flooding, and US$125 billion in damage. Yet, despite numerous reports on its environmental and economic impacts, little is known about how much debris has entered the marine environment. Here, using satellite images (MODIS, MERIS, and Landsat), airborne photographs, and imaging spectroscopy, we show the distribution, possible types, and amount of Katrina-induced debris in the northern Gulf of Mexico. Satellite images collected between August 30 and September 19 show elongated image features around the Mississippi River Delta in a region bounded by 92.5°W-87.5°W and 27.8°N-30.25°N. Image spectroscopy and color appearance of these image features indicate that they are likely dominated by driftwood (including construction lumber) and dead plants (e.g., uprooted marsh) and possibly mixed with plastics and other materials. The image sequence shows that if aggregated together to completely cover the water surface, the maximal debris area reached 21.7 km2 on August 31 to the east of the delta, which drifted to the west following the ocean currents. When measured by area in satellite images, this perhaps represents a historical record of all previously reported floating debris due to natural disasters such as hurricanes, floodings, and tsunamis.
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Modeling Anthropogenic and Environmental Influences on Freshwater Harmful Algal Bloom Development Detected by MERIS Over the Central United States. WATER RESOURCES RESEARCH 2021; 57:e2020WR028946. [PMID: 35860362 PMCID: PMC9285409 DOI: 10.1029/2020wr028946] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Revised: 06/21/2021] [Accepted: 09/06/2021] [Indexed: 05/31/2023]
Abstract
Human and ecological health have been threatened by the increase of cyanobacteria harmful algal blooms (cyanoHABs) in freshwater systems. Successful mitigation of this risk requires understanding the factors driving cyanoHABs at a broad scale. To inform management priorities and decisions, we employed random forest modeling to identify major cyanoHAB drivers in 369 freshwater lakes distributed across 15 upper Midwest states during the 2011 bloom season (July-October). We used Cyanobacteria Index (CI_cyano)-A remotely sensed product derived from the MEdium Resolution Imaging Spectrometer (MERIS) aboard the European Space Agency's Envisat satellite-as the response variable to obtain variable importance metrics for 75 landscape and lake physiographic predictor variables. Lakes were stratified into high and low elevation categories to further focus CI_cyano variable importance identification by anthropogenic and natural influences. "High elevation" watershed land cover (LC) was primarily forest or natural vegetation, compared with "low elevation" watersheds LC dominated by anthropogenic landscapes (e.g., agriculture and municipalities). We used the top ranked 25 Random Forest variables to create a classification and regression tree (CART) for both low and high elevation lake designations to identify variable thresholds for possible management mitigation. Mean CI_cyano was 3 times larger for "low elevation" lakes than for "high elevation" lakes, with both mean values exceeding the "High" World Health Organization recreational guidance/action level threshold for cyanobacteria (100,000 cells/mL). Agrarian-related variables were prominent across all 369 lakes and low elevation lakes. High elevation lakes showed more influence of lakeside LC than for the low elevation lakes.
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Envisat MERIS and Sentinel-3 OLCI satellite lake biophysical water quality flag dataset for the contiguous United States. Data Brief 2019; 28:104826. [PMID: 31871980 PMCID: PMC6909159 DOI: 10.1016/j.dib.2019.104826] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2019] [Revised: 11/01/2019] [Accepted: 11/08/2019] [Indexed: 11/26/2022] Open
Abstract
Monitoring lake biophysical water quality is a global challenge. Satellite remote sensing offers a technology for continuous water quality information in data poor regions throughout the United States. Quality assurance flag data are provided for the presence of snow/ice, land-adjacency, and unresolvable waterbodies supporting water quality derived measures from Envisat MEdium Resolution Imaging Spectrometer and Sentinel-3 Ocean and Land Colour Instrument for the continental United States. In addition, an updated Waterbody Data mask that contains valid waterbody and coastal ocean delineation is provided. The quality assurance flag datasets can benefit the scientific community in processing lake water quality throughout the contiguous United States by addressing errors from snow/ice, land adjacency, and land masking. The dataset presented here will be used in the development of national scale metrics for derived biophysical water quality in the US.
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Key Words
- Biophysical water quality
- CONUS, Contiguous United States
- DN, Digital Number
- ESA, European Space Agency
- Envisat
- Lakes
- MERIS
- MERIS, Medium Resolution Imaging Spectroradiometer
- NASA, National Aeronautical Space Administration
- NHD, National Hydrography Dataset
- NLA, National Lakes Assessment
- OBPG, Ocean Biology Processing Group
- OLCI
- OLCI, Ocean Land Colour Instrument
- QA, Quality Assurance
- Remote sensing
- SEADAS, SeaWIFS Data Analysis
- SRTM, Shuttle Radar Topography Mission
- SWBD, SRTM Waterbody Data
- Satellite
- Sentinel-3
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Spatio-Temporal Dynamics of Inherent Optical Properties in Oligotrophic Northern Gulf of Mexico Estuaries. CONTINENTAL SHELF RESEARCH 2018; 166:92-107. [PMID: 36419821 PMCID: PMC9680836 DOI: 10.1016/j.csr.2018.06.016] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
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 (aphi). Results showed that absorption by detritus and gelbstoff (adg) 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.
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On the detectability of adjacency effects in ocean color remote sensing of mid-latitude coastal environments by SeaWiFS, MODIS-A, MERIS, OLCI, OLI and MSI. REMOTE SENSING OF ENVIRONMENT 2018; 209:423-438. [PMID: 29725142 PMCID: PMC5890359 DOI: 10.1016/j.rse.2017.12.021] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 12/06/2017] [Accepted: 12/15/2017] [Indexed: 05/25/2023]
Abstract
The detectability of adjacency effects (AE) in ocean color remote sensing by SeaWiFS, MODIS-A, MERIS, OLCI, OLI and MSI is theoretically assessed for typical observation conditions up to 36 km offshore (20 km for MSI). The methodology detailed in Bulgarelli et al. (2014) is applied to expand previous investigations to the wide range of terrestrial land covers and water types usually encountered in mid-latitude coastal environments. Simulations fully account for multiple scattering within a stratified atmosphere bounded by a non-uniform reflecting surface, sea surface roughness, sun position and off-nadir sensor view. A harmonized comparison of AE is ensured by adjusting the radiometric sensitivity of each sensor to the same input radiance. Results show that average AE in data from MODIS-A, and from MERIS and OLCI in reduced spatial resolution, are still above the sensor noise level (NL) at 36 km offshore, except for AE caused by green vegetation at the red wavelengths. Conversely, in data from the less sensitive SeaWiFS, OLI and MSI sensors, as well as from MERIS and OLCI in full spatial resolution, sole AE caused by highly reflecting land covers (such as snow, dry vegetation, white sand and concrete) are above the sensor NL throughout the transect, while AE originated from green vegetation and bare soil at visible wavelengths may become lower than NL at close distance from the coast. Such a distance increases with the radiometric resolution of the sensor. It is finally observed that AE are slightly sensitive to the water type only at the blue wavelengths. Notably, for an atmospheric correction scheme inferring the aerosol properties from NIR data, perturbations induced by AE at NIR and visible wavelengths might compensate each other. As a consequence, biases induced by AE on radiometric products (e.g., the water-leaving radiance) are not strictly correlated to the intensity of the reflectance of the nearby land.
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Water quality near Estonian harbours in the Baltic Sea as observed from entire MERIS full resolution archive. MARINE POLLUTION BULLETIN 2018; 126:565-574. [PMID: 28986113 DOI: 10.1016/j.marpolbul.2017.09.058] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2017] [Revised: 09/22/2017] [Accepted: 09/25/2017] [Indexed: 06/07/2023]
Abstract
Variations and trends in water quality parameters (total suspended matter and coloured dissolved organic matter) were examined in five harbours in the eastern Baltic Sea using satellite imagery collected from 2002 to 2011 by the Medium Resolution Imaging Spectrometer (MERIS) at full spatial resolution (300×300m). In the eastern Gulf of Finland harbours (Sillamäe, Kunda) the TSM monthly variations were related to monthly mean wind speed. In Tallinn harbour, which operates >6000 vessels annually, evidence of anthropogenic impacts was identified through inter-annual TSM variations. The vessel traffic footprint was ascertained from the significant correlation (R=0.66; p=0.035) between the number of annual vessel visits and mean annual TSM concentration. In the harbour of Pärnu, located close to the river mouth, inter-annual water quality variations in terms of the CDOM concentrations were affected by the mean annual river discharge levels of the Pärnu River.
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Determination of phytoplankton abundances (Chlorophyll-a) in the optically complex inland water - The Baltic Sea. THE SCIENCE OF THE TOTAL ENVIRONMENT 2017; 601-602:1060-1074. [PMID: 28599362 DOI: 10.1016/j.scitotenv.2017.05.245] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Revised: 05/26/2017] [Accepted: 05/26/2017] [Indexed: 06/07/2023]
Abstract
A novel approach, termed Summed Positive Peaks (SPP), is proposed for determining phytoplankton abundances (Chlorophyll-a or Chl-a) and surface phytoplankton bloom extent in the optically complex Baltic Sea. The SPP approach is established on the basis of a baseline subtraction method using Rayleigh corrected top-of-atmosphere data from the Medium Resolution Imaging Spectrometer (MERIS) measurements. It calculates the reflectance differences between phytoplankton related signals observed in the MERIS red and near infrared (NIR) bands, such as sun-induced chlorophyll fluorescence (SICF) and the backscattering at 709nm, and considers the summation of the positive line heights for estimating Chl-a concentrations. The SPP algorithm is calibrated against near coincident in situ data collected from three types of phytoplankton dominant waters encountered in the Baltic Sea during 2010 (N=379). The validation results show that the algorithm is capable of retrieving Chl-a concentrations ranging from 0.5 to 3mgm-3, with an RMSE of 0.24mgm-3 (R2=0.69, N=264). Additionally, the comparison results with several Chl-a algorithms demonstrates the robustness of the SPP approach and its sensitivity to low to medium biomass waters. Based on the red and NIR reflectance features, a flagging method is also proposed to distinguish intensive surface phytoplankton blooms from the background water.
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[Remote Sensing of Chlorophyll-a Concentrations in Lake Hongze Using Long Time Series MERIS Observations]. HUAN JING KE XUE= HUANJING KEXUE 2017; 38:3645-3656. [PMID: 29965243 DOI: 10.13227/j.hjkx.201702192] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Chlorophyll-a (Chl-a) concentrations are usually measured as the proxy of phytoplankton biomass and used to evaluate the trophic status of inland waters. Based on 49 in situ samples taken from two measurement campaigns in Lake Hongze in 2016, we evaluate the performance of five Chl-a estimation algorithms (including the band ratio, three-band, FLH algorithm, MCI, and UMOC algorithms). The results showed that the UMOC model was the most suitable model for the estimation of Chl-a in Lake Hongze. The mean relative error (MRE) of UMOC was 32.30%, much lower than the band ratio algorithm (75.17%), three-band algorithm (62.44%), FLH algorithm (45.87%), and MCI algorithm (56.95%). The best-performing UMOC model was applied to the atmospherically corrected 689 MERIS images between 2002-2012 and long time series MERIS Chl-a concentration estimation products were acquired. Between 2002 and 2012, the mean Chl-a concentration in Lake Hongze was 19.560 mg·m-3 with substantial spatial and temporal variability. Based on the variability of monthly mean Chl-a concentrations in each pixel, the Lake Hongze waterbody was divided into three water types, Region A, Region B, and Region C. The annual mean Chl-a concentrations of Region B and Region C showed no significant changes, while the concentrations in Region A increased markedly. The analysis of the meteorological factors showed that the fluctuations of the annual mean Chl-a concentrations in Region B and Region C were mainly affected by annual precipitation, suggesting that the Chl-a concentrations of these two regions are dominated by the intensity of the lake flow. The annual mean Chl-a concentrations of Region A showed a strong negative correlation with the annual mean wind speed. The descending trend of the annual wind speed may enhance the eutrophication degree of this region, threatening the safety of the water quality of the South-North Water Transfer Project. The Chl-a concentrations showed a strong positive correlation with the distance from the Huaihe Estuary in the wet season suggesting that the Huaihe River has an obvious inhibitory effect on algal biomass in Lake Hongze during this period.
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Retrieval of aerosol optical properties using MERIS observations: Algorithm and some first results. REMOTE SENSING OF ENVIRONMENT 2017; 197:125-140. [PMID: 29760534 PMCID: PMC5946060 DOI: 10.1016/j.rse.2016.11.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The MEdium Resolution Imaging Spectrometer (MERIS) instrument on board ESA Envisat made measurements from 2002 to 2012. Although MERIS was limited in spectral coverage, accurate Aerosol Optical Thickness (AOT) from MERIS data are retrieved by using appropriate additional information. We introduce a new AOT retrieval algorithm for MERIS over land surfaces, referred to as eXtensible Bremen AErosol Retrieval (XBAER). XBAER is similar to the "dark-target" (DT) retrieval algorithm used for Moderate-resolution Imaging Spectroradiometer (MODIS), in that it uses a lookup table (LUT) to match to satellite-observed reflectance and derive the AOT. Instead of a global parameterization of surface spectral reflectance, XBAER uses a set of spectral coefficients to prescribe surface properties. In this manner, XBAER is not limited to dark surfaces (vegetation) and retrieves AOT over bright surface (desert, semiarid, and urban areas). Preliminary validation of the MERIS-derived AOT and the ground-based Aerosol Robotic Network (AERONET) measurements yield good agreement, the resulting regression equation is y = (0.92 × ± 0.07) + (0.05 ± 0.01) and Pearson correlation coefficient of R = 0.78. Global monthly means of AOT have been compared from XBAER, MODIS and other satellite-derived datasets.
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A method for examining temporal changes in cyanobacterial harmful algal bloom spatial extent using satellite remote sensing. HARMFUL ALGAE 2017; 67:144-152. [PMID: 28755717 PMCID: PMC6084444 DOI: 10.1016/j.hal.2017.06.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Revised: 05/26/2017] [Accepted: 06/03/2017] [Indexed: 05/06/2023]
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.
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Ten-year survey of cyanobacterial blooms in Ohio's waterbodies using satellite remote sensing. HARMFUL ALGAE 2017; 66:13-19. [PMID: 28602249 DOI: 10.1016/j.hal.2017.04.013] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Revised: 02/04/2017] [Accepted: 04/07/2017] [Indexed: 06/07/2023]
Abstract
Cyanobacterial blooms are on the rise globally and are capable of adversely impacting human, animal, and ecosystem health. Blooms dominated by cyanobacteria species capable of toxin-production are commonly observed in eutrophic freshwater. The presence of cyanobacterial blooms in selected Ohio lakes, such as Lake Erie and Grand Lake St. Marys, has been well studied, but much less is known about the geographic distribution of these blooms across all of Ohio's waterbodies. We examined the geographic distribution of cyanobacterial blooms in Ohio's waterbodies from 2002 to 2011, using a nested semi-empirical algorithm and remotely sensed data from the Medium Resolution Imaging Spectrometer (MERIS) onboard the European Space Agency's Envisat. We identified: 62 lakes, reservoirs, and ponds; 7 rivers; 6 marshes and wetlands; and 3 quarries with detectable cyanobacteria pigment (phycocyanin) concentrations. Of the 78 waterbodies identified in our study, roughly half (54%; n=42) have any reported in situ microcystins monitoring results from state monitoring programs. Further, 90% of the waterbodies identified reached phycocyanin pigment concentrations representative of levels potentially hazardous to public health. This gap in lakes potentially impacted by cyanobacterial blooms and those that are currently monitored presents an important area of concern for public health, as well as ecosystem health, where unknown human and animal exposures to cyanotoxins may occur in many of Ohio's waterbodies. Our approach may be replicated in other regions around the globe with potential cyanobacterial bloom presence, in order to assess the intensity, geographic distribution, and temporal pattern of blooms in lakes not currently monitored for the presence of cyanobacterial blooms.
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Challenges for mapping cyanotoxin patterns from remote sensing of cyanobacteria. HARMFUL ALGAE 2016; 54:160-173. [PMID: 28073474 DOI: 10.1016/j.hal.2016.01.005] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 01/14/2016] [Accepted: 01/15/2016] [Indexed: 05/04/2023]
Abstract
Using satellite imagery to quantify the spatial patterns of cyanobacterial toxins has several challenges. These challenges include the need for surrogate pigments - since cyanotoxins cannot be directly detected by remote sensing, the variability in the relationship between the pigments and cyanotoxins - especially microcystins (MC), and the lack of standardization of the various measurement methods. A dual-model strategy can provide an approach to address these challenges. One model uses either chlorophyll-a (Chl-a) or phycocyanin (PC) collected in situ as a surrogate to estimate the MC concentration. The other uses a remote sensing algorithm to estimate the concentration of the surrogate pigment. Where blooms are mixtures of cyanobacteria and eukaryotic algae, PC should be the preferred surrogate to Chl-a. Where cyanobacteria dominate, Chl-a is a better surrogate than PC for remote sensing. Phycocyanin is less sensitive to detection by optical remote sensing, it is less frequently measured, PC laboratory methods are still not standardized, and PC has greater intracellular variability. Either pigment should not be presumed to have a fixed relationship with MC for any water body. The MC-pigment relationship can be valid over weeks, but have considerable intra- and inter-annual variability due to changes in the amount of MC produced relative to cyanobacterial biomass. To detect pigments by satellite, three classes of algorithms (analytic, semi-analytic, and derivative) have been used. Analytical and semi-analytical algorithms are more sensitive but less robust than derivatives because they depend on accurate atmospheric correction; as a result derivatives are more commonly used. Derivatives can estimate Chl-a concentration, and research suggests they can detect and possibly quantify PC. Derivative algorithms, however, need to be standardized in order to evaluate the reproducibility of parameterizations between lakes. A strategy for producing useful estimates of microcystins from cyanobacterial biomass is described, provided cyanotoxin variability is addressed.
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Oil slick morphology derived from AVIRIS measurements of the Deepwater Horizon oil spill: Implications for spatial resolution requirements of remote sensors. MARINE POLLUTION BULLETIN 2016; 103:276-285. [PMID: 26725867 DOI: 10.1016/j.marpolbul.2015.12.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/23/2015] [Revised: 11/14/2015] [Accepted: 12/05/2015] [Indexed: 05/22/2023]
Abstract
Using fine spatial resolution (~7.6m) hyperspectral AVIRIS data collected over the Deepwater Horizon oil spill in the Gulf of Mexico, we statistically estimated slick lengths, widths and length/width ratios to characterize oil slick morphology for different thickness classes. For all AVIRIS-detected oil slicks (N=52,100 continuous features) binned into four thickness classes (≤50 μm but thicker than sheen, 50-200 μm, 200-1000 μm, and >1000 μm), the median lengths, widths, and length/width ratios of these classes ranged between 22 and 38 m, 7-11 m, and 2.5-3.3, respectively. The AVIRIS data were further aggregated to 30-m (Landsat resolution) and 300-m (MERIS resolution) spatial bins to determine the fractional oil coverage in each bin. Overall, if 50% fractional pixel coverage were to be required to detect oil with thickness greater than sheen for most oil containing pixels, a 30-m resolution sensor would be needed.
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True colour classification of natural waters with medium-spectral resolution satellites: SeaWiFS, MODIS, MERIS and OLCI. SENSORS 2015; 15:25663-80. [PMID: 26473859 PMCID: PMC4634488 DOI: 10.3390/s151025663] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Revised: 09/28/2015] [Accepted: 09/28/2015] [Indexed: 12/03/2022]
Abstract
The colours from natural waters differ markedly over the globe, depending on the water composition and illumination conditions. The space-borne “ocean colour” instruments are operational instruments designed to retrieve important water-quality indicators, based on the measurement of water leaving radiance in a limited number (5 to 10) of narrow (≈10 nm) bands. Surprisingly, the analysis of the satellite data has not yet paid attention to colour as an integral optical property that can also be retrieved from multispectral satellite data. In this paper we re-introduce colour as a valuable parameter that can be expressed mainly by the hue angle (α). Based on a set of 500 synthetic spectra covering a broad range of natural waters a simple algorithm is developed to derive the hue angle from SeaWiFS, MODIS, MERIS and OLCI data. The algorithm consists of a weighted linear sum of the remote sensing reflectance in all visual bands plus a correction term for the specific band-setting of each instrument. The algorithm is validated by a set of 603 hyperspectral measurements from inland-, coastal- and near-ocean waters. We conclude that the hue angle is a simple objective parameter of natural waters that can be retrieved uniformly for all space-borne ocean colour instruments.
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Application of remote sensing for the optimization of in-situ sampling for monitoring of phytoplankton abundance in a large lake. THE SCIENCE OF THE TOTAL ENVIRONMENT 2015; 527-528:493-506. [PMID: 26002424 DOI: 10.1016/j.scitotenv.2015.05.011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2015] [Revised: 04/30/2015] [Accepted: 05/04/2015] [Indexed: 05/15/2023]
Abstract
Directives and legislations worldwide aim at representatively and continuously monitoring the ecological status of surface waters. In many countries, chlorophyll-a concentrations (CHL) are used as an indicator of phytoplankton abundance and the trophic level of lakes or reservoirs. In-situ measurements of water quality parameters, however, are time-consuming, costly and of unknown but naturally limited spatial representativeness. In addition, the variety of the involved lab and field measurement methods and instruments complicates comparability and reproducibility. Taking Lake Geneva as an example, 1234 satellite images from the MERIS sensor on the Envisat satellite from 2002 to 2012 are used to quantify the spatial and temporal variations of CHL concentrations. Based on histograms of spring, summer and autumn CHL estimates, the spatial representativeness of two existing in-situ measurement locations is analysed. Appropriate sampling frequencies to capture CHL peaks are examined by means of statistical resampling. The approaches proposed allow determining optimal in-situ sampling locations and frequencies. Their generic nature allows for adaptation to other lakes, especially to establish new survey programmes where no previous records are available.
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Spatial and temporal patterns in the seasonal distribution of toxic cyanobacteria in Western Lake Erie from 2002-2014. Toxins (Basel) 2015; 7:1649-63. [PMID: 25985390 PMCID: PMC4448166 DOI: 10.3390/toxins7051649] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Revised: 04/20/2015] [Accepted: 04/27/2015] [Indexed: 11/16/2022] Open
Abstract
Lake Erie, the world's tenth largest freshwater lake by area, has had recurring blooms of toxic cyanobacteria for the past two decades. These blooms pose potential health risks for recreation, and impact the treatment of drinking water. Understanding the timing and distribution of the blooms may aid in planning by local communities and resources managers. Satellite data provides a means of examining spatial patterns of the blooms. Data sets from MERIS (2002-2012) and MODIS (2012-2014) were analyzed to evaluate bloom patterns and frequencies. The blooms were identified using previously published algorithms to detect cyanobacteria (~25,000 cells mL-1), as well as a variation of these algorithms to account for the saturation of the MODIS ocean color bands. Images were binned into 10-day composites to reduce cloud and mixing artifacts. The 13 years of composites were used to determine frequency of presence of both detectable cyanobacteria and high risk (>100,000 cells mL-1) blooms. The bloom season according to the satellite observations falls within June 1 and October 31. Maps show the pattern of development and areas most commonly impacted during all years (with minor and severe blooms). Frequencies during years with just severe blooms (minor bloom years were not included in the analysis) were examined in the same fashion. With the annual forecasts of bloom severity, these frequency maps can provide public water suppliers and health departments with guidance on the timing of potential risk.
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Bayesian model for matching the radiometric measurements of aerospace and field ocean color sensors. SENSORS 2010; 10:7561-75. [PMID: 22163615 PMCID: PMC3231150 DOI: 10.3390/s100807561] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/11/2010] [Revised: 07/16/2010] [Accepted: 08/10/2010] [Indexed: 11/17/2022]
Abstract
A Bayesian model is developed to match aerospace ocean color observation to field measurements and derive the spatial variability of match-up sites. The performance of the model is tested against populations of synthesized spectra and full and reduced resolutions of MERIS data. The model derived the scale difference between synthesized satellite pixel and point measurements with R2 > 0.88 and relative error < 21% in the spectral range from 400 nm to 695 nm. The sub-pixel variabilities of reduced resolution MERIS image are derived with less than 12% of relative errors in heterogeneous region. The method is generic and applicable to different sensors.
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Atmospheric Effects on InSAR Measurements and Their Mitigation. SENSORS 2008; 8:5426-5448. [PMID: 27873822 PMCID: PMC3705512 DOI: 10.3390/s8095426] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Revised: 08/29/2008] [Accepted: 08/29/2008] [Indexed: 11/16/2022]
Abstract
Interferometric Synthetic Aperture Radar (InSAR) is a powerful technology for observing the Earth surface, especially for mapping the Earth's topography and deformations. InSAR measurements are however often significantly affected by the atmosphere as the radar signals propagate through the atmosphere whose state varies both in space and in time. Great efforts have been made in recent years to better understand the properties of the atmospheric effects and to develop methods for mitigating the effects. This paper provides a systematic review of the work carried out in this area. The basic principles of atmospheric effects on repeat-pass InSAR are first introduced. The studies on the properties of the atmospheric effects, including the magnitudes of the effects determined in the various parts of the world, the spectra of the atmospheric effects, the isotropic properties and the statistical distributions of the effects, are then discussed. The various methods developed for mitigating the atmospheric effects are then reviewed, including the methods that are based on PSInSAR processing, the methods that are based on interferogram modeling, and those that are based on external data such as GPS observations, ground meteorological data, and satellite data including those from the MODIS and MERIS. Two examples that use MODIS and MERIS data respectively to calibrate atmospheric effects on InSAR are also given.
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