1 / 17

Detecting and monitoring K. brevis blooms in the eastern Gulf of Mexico

Detecting and monitoring K. brevis blooms in the eastern Gulf of Mexico. A toxic dinoflagellate which causes neurotoxic shellfish poisoning, deaths of marine mammals & fish, and human respiratory irritation Blooms result in high chlorophyll and discolored water ranging from mahogany to yellow.

ivrit
Download Presentation

Detecting and monitoring K. brevis blooms in the eastern Gulf of Mexico

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Detecting and monitoring K. brevis blooms in the eastern Gulf of Mexico

  2. A toxic dinoflagellate which causes neurotoxic shellfish poisoning, deaths of marine mammals & fish, and human respiratory irritation Blooms result in high chlorophyll and discolored water ranging from mahogany to yellow What is K. brevis?

  3. Can SeaWiFS detect K. brevis? • SeaWiFS can estimate chlorophyll concentrations using a regionally specific algorithm • K. brevis blooms are a major component of the phytoplankton biomass • oligotrophic waters • occur in late summer through winter when diatoms blooms are rare • chl ranges from 1 to 100 μg l−1 in the bloom, much higher than background levels on the inner shelf

  4. Anomalies are used to indicate the presence of a K. brevis bloom Remove the seasonal pattern Chl anomalies > 1 μg l−1 are indicative of K. brevis Comparison of imagery and observations shows method accurate 75% of the time Detecting K. brevis from chl data Relationship of measured chlorophyll-a to K. brevis cell concentrations off southwest Florida, September 2001. Dotted line shows the relationship of 1 μg l−1 to 100 cells ml−1.

  5. Cell counts during cruise, September 19–26, 2001 Chlorophyll (upper group) and anomalies (lower group)

  6. MODIS fluorescence • SeaWiFS coastal limitations: • Satellite derived chl suffer from uncertainties in the atmospheric correction and the presence of other colored material such as CDOM, detritus, other phytoplankton, and a shallow bottom. • Recent studies show MODIS fluorescence line height (FLH) shows the highest correlation with near-concurrent in situ chl-a measurements. These correlations held up through time and across various water types.

  7. MODIS data MODIS/Aqua imagery. Left column: Fluorescence Line Height (FLH). Middle column: band-ratio chlorophyll concentration. Right column: enhanced RGB (ERGB) composite images from water-leaving radiance in three MODIS wavelengths: 551 nm (R), 488 nm (G), and 443 nm (B).

  8. MODIS vs SeaWiFS Cross-shelf transect, up to ± 6 hr time difference, r between in situ Chl and MODIS FLH, MODIS Chl, and SeaWiFS Chl are 0.79, 0.52, and 0.43 Alongshore transect, only ± 2 hr time difference between MODIS and in situ surveys In situ Chl (mg m− 3), MODIS FLH (W m− 2 μm− 1 sr− 1, MODIS Chl (mg m− 3)

  9. Overestimate of chl due to CDOM MODIS/Aqua imagery on 13 November 2004 (18:32 GMT). Overlaid on the FLH and Chl images are two arbitrary along-coast and cross-shelf transect lines.

  10. Why does MODIS provide more accurate chl mesurements in coastal environments? • MODIS FLH bands focus on the red part of the spectrum where chl fluorescence dominates the total signal • SeaWiFS chl measurements are based on absorption in the blue where CDOM oftens dominates the signal

  11. Tracking blooms w/ AUV’s • Fill in the gaps of satellite data and provide 3D data of bloom dynamics over time • Detect whether a bloom is toxic and track the bloom front over shorter timescales • Collect water samples • Measure currents with ADCPs

  12. REMUS • Uses an optical phytoplankton discriminator to detect K. brevis cells from mixed phytoplankton communities • A similarity index (SI) is established which indicates when K. brevis dominates the phytoplankton community

  13. Tracking a bloom (MODIS) satellite chlorophyll (A) and SST (B) from January 9, 2005. A high chlorophyll patch along the upwelling front was identified as K. brevis Transect from January 21, 2005 Images from January 9, 18, 27, February 10, and 17, showing the progression of K. brevis southward along the shoreline

  14. SI vs chl fluorescence Chlorophyll fluorescence data (μg/L) from the first (A) and second (B) cycles K. brevis similarity index (SI) from the first (A) and second (B) cycles

  15. Low correlation for low chl concentrations Better agreement for higher chl concentrations What about bloom movement? Is the OPD sensor working? K. brevis similarity index (SI) vs. chlorophyll fluorescence for the January 21 transect

  16. Bloom movement along fronts is determined from salinity, temperature, current speed/direction, particulate backscatter, and chlorophyll. Arrows represent along shore current movement parallel to the transect. Color represents cross shore current movement, with hot colors moving away from the viewer and cool colors moving towards the viewer Salinity (psu; A) and temperature (°C; B) data from the first cycle and salinity (C) and temperature (D) from the second cycle of the January 21, 2005 mission

  17. References Stumpf RP, Culver ME, Tester PA, et al.Monitoring Karenia brevis blooms in the Gulf of Mexico using satellite ocean color imagery and other dataHARMFUL ALGAE 2 (2): 147-160 JUN 2003 Tomlinson MC, Stumpf RP, Ransibrahmanakul V, et al.Evaluation of the use of SeaWiFS imagery for detecting Karenia brevis harmful algal blooms in the eastern Gulf of MexicoREMOTE SENSING OF ENVIRONMENT 91 (3-4): 293-303 JUN 30 2004

More Related