Grantee Research Project Results
2004 Progress Report: Behaving Drifters as Gymnodinium breve Mimics
EPA Grant Number: R829370Title: Behaving Drifters as Gymnodinium breve Mimics
Investigators: Kamykowski, Daniel , Wolcott, Thomas G. , Janowitz, Gerald S.
Institution: North Carolina State University
EPA Project Officer: Packard, Benjamin H
Project Period: November 19, 2001 through November 18, 2004 (Extended to May 18, 2006)
Project Period Covered by this Report: November 19, 2003 through November 18, 2004
Project Amount: $423,493
RFA: Ecology and Oceanography of Harmful Algal Blooms (2001) RFA Text | Recipients Lists
Research Category: Water Quality , Water , Aquatic Ecosystems
Objective:
The objectives of this research project are to: (1) parameterize a representative physiological/behavioral Karenia brevis model based on laboratory experiments; (2) construct K. brevis Population Mimics (KBPM); (3) follow the trajectories of the free-ranging, buoyancy-adjusting floats programmed to act as K. brevis on the west Florida shelf; and (4) incorporate the laboratory and field results into evolving physical-biological numerical models.
Taxonomic Update
Because Gymnodinium breve was renamed Karenia brevis, the Gymnodinium breve Population Mimic (GBPM) is now called the Karenia brevis Population Mimic (KBPM).
Hypotheses
The purpose of this project is to follow the trajectories of free-ranging, buoyancy-adjusting floats programmed to act as KBPM on the west Florida shelf and to incorporate the results into evolving physical-biological models. Hypotheses that will be tested remain the same.
The hypotheses to be tested in support of improving behavioral programming are:
Hypothesis 1: K. brevis exhibits positive chemotaxis toward inorganic and organic nutrients.
Hypothesis 2: K. brevis adjusts its migration in response to the nutrient sources that yield a chemotactic response when they are available in only part of a laboratory water column.
The hypotheses to be tested in support of testing KBPM utility are:
Hypothesis 3: KBPMs and CODE drifters placed in proximity to each other follow similar tracks.
Hypothesis 4: KBPM that migrate vertically in the same water column as other KBPM distributed and maintained at different water column depths integrate the horizontal flows encountered during the vertical migration and track differently than the KBPM maintained at any given depth.
Hypothesis 5: The environmental exposure recorded by the migrating KBPM will support better relative growth than that recorded by the stationary depth KBPM when entered into an existing model of K. brevis’ physiological responses.
Hypothesis 6: KBPM, programmed to vertically migrate, track in situ K. brevis populations when dropped into natural aggregations of K. brevis.
The hypothesis to be tested in support of improving previous numerical models is:
Hypothesis 7: Physical-biological models incorporating information obtained from KBPM better simulate natural events (population growth and physical aggregation) than those that do not.
Progress Summary:
Hypothesis 1
No further results are available on chemotaxis during the reporting period.
Hypothesis 2
Two mesocosms each illuminated at approximately 1,000 μ mole quanta m-2 s-1 were maintained at constant temperature during an experiment comparing nitrate replete and deplete mesocosms. In general, the intensity of the daytime aggregation decreased in the nutrient-deleted water column, but the populations remained diffuse through the water column at night in both cases. To more realistically test the nutrient effects, a mesocosm was set up with nitrate only available in the lower one-third of the water column that was maintained at 4°C less than the upper two-thirds of the water column. This situation was conceived as simulating a subthermocline nutrient source or a nutrient flux out of the sediments. In this case, a strong surface aggregate during the day was followed by an accumulation of cells in the lower layer at night. Parallel batch culture experiments were run with 15N-NO3 to determine the day/night nitrate uptake characteristics of K. brevis using populations just reaching nitrate depletion and another population in a nutrient-replete state. Under nitrate-replete conditions, dark uptake is much less than light uptake. Under incipient nitrate-deplete conditions, dark uptake equals light uptake. With these differences in mind, 15N-NO3 uptake in the nitrate stratified mesocosm was intermediate between the two batch cultures in day/night capacity, suggesting that the nutrient-stratified water column offers an intermediate condition of nitrate availability.
Laboratory experiments were performed in support of behavioral model improvements for the KBPM. Radial photosynthetron experiments with 10 strains isolated from geographically diverse areas in the Gulf of Mexico and the Florida Atlantic Coast fell along a gradient of light capability. In different experiments, the order of the different strains along the light capability gradient changed depending on culture density and growth rate. Based on experiments with dilution solutions derived with various filtration meshes, we presently believe that bacteria play a role in the exact photoresponse that a strain exhibits. This has implications related to the extent to which field populations are differentially transported in horizontal space during diel vertical migrations. For example, a population that re-enters the same surface water each day may be more photoinhibited than a population that moves relative to surface water at night to enter into new surface water the next day.
Hypotheses 3, 4, 5 and 6
Design of the KBPM is now complete, and all subsystems have been functionally tested. The program for its user interface, datalogging/uploading, and operation (about 6,500 lines) is complete. Laboratory trials have revealed appropriate parameter values for optimizing “swimming” with minimal under/overshoots of depth (Figure 1). Field deployments await resolution of (apparently compiler-caused) interrupt conflicts. As soon as the software vendor fixes the bug, we will begin accumulating field experience with the mimics. A significant K. brevis event did not occur on the west Florida shelf during fall 2004, but we continue to watch the Web sites for information on the status of K. brevis and plan to travel to Florida when appropriate. The final fabrication of the operating KBPM is described below.
Figure 1. Depth Regulation by Mimic (Step Profile)
The design is based on a high-end Microchip PIC microcontroller with sufficient on-chip resources to permit a large reduction in parts count and complexity, hence increase in reliability. All the circuitry (except temperature sensor, IR communications transceiver, GPS, and radio beacon module) fits an 11-cm diameter PC board. It comprises the PIC; 64-256K of nonvolatile data memory; real-time clock; sensors for rotation, pressure, and light; and drivers for the pinger, buoyancy pump, radio and LED beacons, and conductivity cell.
Reprogramming now can be conducted via the IR serial port without opening the housing, facilitating rapid turnaround when testing new programs. The mating module we have designed plugs directly into a host computer’s serial port and requires no power source other than the port itself.
The mimic’s user interface includes a menu providing access to a host of operational parameters (sensor calibrations, wake interval, datalogging frequency, variables to log, migration models, GPS fix times, recovery time, upload of logged data, etc.)
The “speed through water” sensor uses a new device, the Austria Microsystems AS5020. It encodes the angular position of a magnet suspended above it with 5.6 degree resolution and sends the angle to the microcontroller as serial data. A rare-earth bar magnet with a 6mm center gap is suspended a few mm above the chip on a low-friction pivot. It acts as a (geostationary) compass needle, whereas the gap provides a field whose rotational position the device encodes. The program uses the output to sense angular velocity caused by spin of the “propeller” drag skirt as the device moves up or down through the water.
The salinity sensor, a conductivity cell with graphite electrodes, has been scaled up from one used in our blue crab dataloggers. The software that reads it produces a very linear measure of conductance (correlation coefficient > 0.999), corrects for the current temperature reading (sensor in same module as conductivity cell), and calculates salinity.
The temperature- (Figure 2) and gain-compensated pressure transducer is read by the PIC’s 10-bit A/D converter, and 10 samples are averaged to reduce the effect of power-line noise from the switching voltage regulator. In the next upgrade, we will add a linear voltage regulator for the analog module to minimize noise and digital potentiometers to permit dynamically resetting the span and increase resolution (from the current 0.1 m) at shallower depths.
Figure 2. Temperature/PAR Logging by Mimic (Bench by Window)
The sensor for light (photosynthetically active radiation [PAR]) is the TAOS TCS230, which measures light intensity in several bands. Light is collected by a spherical Teflon diffuser and conducted to the sensor by a graded-index light fiber (Fujitsu) bundle. The mimic program weights the response in each band such that the aggregate curve is as flat as possible between 400 and 700 nm. As the ambient spectral composition changes, such a sensor provides an approximation of the energy available for photosynthesis. The sensor is calibrated by comparison with a standard PAR sensor.
Geographical position fixes are obtained during brief surface intervals. A Garmin GPS receiver engine relays position data to the microcontroller’s secondary serial port. The PIC uses the satellite time data to update the system clock to the exact second, and logs a good position fix (dilution of precision below a threshold value, or the minimum obtainable within the allowed time). Before sinking back to “playing organism,” the instrument transmits its current position over the radio beacon. Encoding position information on the beacon signal also will facilitate recovery of mimics at the end of deployments.
Data (time, target and observed depth, temperature, PAR, salinity, pump activity, vertical velocity, etc.) are logged into nonvolatile serial electronically erasable programmable read-only memory. The user interface allows selecting which variables to log, and the program “packs” them into memory with no space lost for unused variables. Data are uploaded in a spreadsheet-compatible format.
The basis of the pressure housing remains a fire extinguisher cylinder; these are inexpensive, readily available, and of almost exactly the right characteristics for 100 m maximum depth. The two halves meet in a PVC ring with o-ring seals. The module containing the IR communications port, temperature sensor, and salinity sensor is part of this mating ring. A plug that screws into the neck of the cylinder incorporates the radio beacon, 32 KHz tracking/telemetry pinger, pressure sensor tube, light collector/fiber, and GPS antenna/cable.
The variable ballast (buoyancy adjusting) system uses vinyl ballast bags and ethylene glycol (antifreeze—noncorrosive and with some lubricity) as the ballast fluid. Using parameters determined empirically in a lab tank, the unit maintains programmed depths within 10 cm.
The acoustic Doppler current profiler and a digital GPS unit continue to function well. The environmental measuring system assembled by SubChem Systems, Inc. (a SeaBird SBE 19plus conductivity-temperature-depth [CTD], a LICOR LI-190SA quantum sensor, a SubChemPak analyzer [nitrate, ammonia and phosphate], and a WETLabs ECO-BB2F [chlorophyll fluorescence and particle concentration via backscatter]) generally is functional, but reliability of the nutrient analyzer and full access to all sensors in real time remains an issue.
Hypothesis 7
The time-dependent, two-dimensional distribution of a population of K. brevis was explored through the use of an Eulerian model. The model combines a previously developed physiologically based behavioral model of these dinoflagellates with a simple model for a two-dimensional, wind-driven flow field over a variable-depth continental shelf. The behavioral model is simplified from that used in previous applications and sigma coordinates are utilized in the model. The application of the model is to test the transition from the near-bottom, offshore initiation to the near-surface, near-shore appearance of K. brevis blooms. Versions of this physical-biological model will be used as KBPM information accumulates to extend the interpretation of different migration scenarios.
Future Activities:
Hypothesis 1
We will renew efforts to develop reliable chemotaxis protocols for K. brevis and to run trials with specific nutrients contained in the culture media that elicited a statistically significant result in two K. brevis strains.
Hypothesis 2
Experiments with nutrient-stratified mesocosms will continue in Year 4. Laboratory experiments with batch cultures will continue to examine biochemical pools and physiological-behavioral rates critical to the parameterization of the K. brevis biological model. Small-scale experiments will continue to examine how swimming path characteristics change at different water column locations over the course of a diel vertical migration.
Hypotheses 3, 4, 5, and 6
Preparation for KBPM field deployments are underway and will continue independently of K. brevis blooms to test the relative result of different behavioral scenarios and in significant K. brevis blooms when they occur to determine behavioral scenarios that best follow bloom progress.
Most major support equipment have been purchased and upgraded, additional deployment opportunities will be taken to continue the development of operational skills. We propose to purchase an ISUS nitrate analyzer (64% on this grant). The ISUS nitrate analyzer provides real-time nitrate, requires no reagents, has fast sample frequency, has low power and compact size, has high data precision and accuracy, has a detection range from 0.5 μM to 2000 μM, corrects for chromophoric dissolved organic matter and turbidity, and has an analog port for easy integration with CTD and other sensors. This ISUS nitrate sensor can be combined with our previously purchased instrument package to provide detailed information on nitrate available to K. brevis on a scale that complements the SubChem nutrient analyzer previously purchased. The ISUS will be used for broad spatial surveys, whereas the SubChem will be reserved for more detailed and more comprehensive nutrient analyses based on more sensitive nitrate analyses (< 0.5 μM) and the parallel measurements of phosphate and ammonia.
Hypothesis 7
The biological part of the biophysical model will continue to be upgraded with the evolving parameterization used in the KBPM. Comparison runs will determine how the full range of K. brevis physiological-behavioral capabilities determined in the laboratory influences the ability to predict bloom initiation and development based on standard physical forcing.
Journal Articles on this Report : 3 Displayed | Download in RIS Format
Other project views: | All 39 publications | 11 publications in selected types | All 10 journal articles |
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Type | Citation | ||
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Janowitz GS, Kamykowski D, Liu G. A three-dimensional wind and behaviorally driven population dynamics model for Karenia brevis. Continental Shelf Research 2008;28(1):177-188. |
R829370 (2004) |
Exit |
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McKay L, Kamykowski D, Milligan E, Schaeffer B, Sinclair G. Comparison of swimming speed and photophysiological responses to different external conditions among three Karenia brevis strains. Harmful Algae 2006;5(6):623-636. |
R829370 (2004) R829370 (Final) |
Exit Exit Exit |
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Nagai T, Yamazaki H, Kamykowski D. A Lagrangian photoresponse model coupled with 2nd-order turbulence closure. Marine Ecology Progress Series 2003;265:17-30. |
R829370 (2003) R829370 (2004) R829370 (Final) |
Exit Exit |
Supplemental Keywords:
marine, ecology, environmental chemistry, physics, organism, measurement methods, modeling, Southeast, water, ecological risk assessment, ecology, Ecology and ecosystems, oceanography, algal blooms, ECOHAB, Karenia brevis Population Mimics, KBPMs, K. brevis behavioral submodel, K. brevis red tides, K. brevis toxins, Gymnodinium breve,, RFA, Scientific Discipline, Water, Ecosystem Protection/Environmental Exposure & Risk, Ecology, Oceanography, algal blooms, Ecological Risk Assessment, Ecology and Ecosystems, Biology, brevetoxins, Gymnodinium breve toxins, ECOHAB, G. breve Population Mimics (GBPMs), G. breve red tidesProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.