Projects

Residence time as a factor controlling harmful algal blooms and fecal coliform bacteria in Little La

End Date: 2-1-12

Abstract

Remediation of water quality that has been degraded through anthropogenic activity is a central theme of NOOA’s 5-year and 20-year plans.  To achieve this, problems must be identified, the causal factors must be defined and then a management plan can be designed and implemented.  While simple in concept, this proves to be difficult in practice.  The estuarine and coastal regions where the problems are most obvious are both complex and dynamic, and the manifestation of the problem may occur on temporal and spatial scales that are not easily observed.

One approach is to examine the causative links in a system that has clearly-identified problems, a representative structure but a small size: in effect a natural mesocosm.  We have identified Little Lagoon, AL, as one such system.  In a collaboration between the PI’s lab, the Alabama Department of Public Health, and volunteers from the local community (members of the Little Lagoon Preservation Society), we have demonstrated that the lagoon:

  • has a high incidence (24% of biweekly samples taken over 2 years) of fecal coliform bacteria above the regulatory threshold of 200 CFU L-1, with a maximum of 25,000 CFU L-1; and
  • is a hot-spot for blooms of the toxic harmful algal bloom (HAB) diatom Pseudo-nitzschia spp., with levels of its neurotoxin (domoic acid) measured at two orders of magnitude above those reported from highly deleterious blooms off the Pacific coast of the U.S.

As the lagoon is used extensively for recreational boating and fishing, these are problems whose causative mechanisms must be identified and addressed.  The density of Pseudo-nitzschia spp. blooms is correlated with discharge from the aquifer in spring-time.  The aquifer is highly contaminated with nitrate, suggesting a link between the HAB and human activity.  The tractable dimensions (c. 12 x 0.75 km), constrained exchange with the Gulf of Mexico, and an existing collaboration between the PI’s lab and local stakeholders make this an ideal test-case for management.

We propose to use a combination of molecular techniques and stable isotope analysis to determine whether the fecal coliforms are of human origin or not and whether the nitrate in the groundwater is derived from agricultural activity or wastewater.  These are the first steps to management of the sources of the coliforms and blooms.  We will develop a hydrodynamic model of residence time and flushing in the lagoon to simulate the outcomes of possible remediation scenarios.  These include widening the pass between the lagoon and the Gulf of Mexico, deepening the pass and creating a second pass.  While the management outcomes are local, the implications are not.  The same mechanism of groundwater coupling to HABs has been proposed for comparable, but physically intractable, systems off Florida and the Yucatan in the Gulf of Mexico and off Australia and Korea.  The proposed work addresses Action Steps WQ-1.1, WQ-1.3, WQ-2.1and WQ-2.5 of the Gulf of Mexico Alliance’s Action Plan II, the Gulf-wide list of priorities for research and management of pathogenic bacteria and HABs that has been endorsed by NOAA, US EPA and USGS.

Objectives

The overall objective of this proposal is to provide stakeholders and managers of Little Lagoon, AL, with data to help develop a science-based management plan for fecal coliform contamination and toxic blooms of the diatom Pseudo-nitzschia spp.  Three specific objectives are:

  1. to use genetic fingerprinting to determine the source of fecal coliforms;
  2. to use isotopic signatures to determine the source of nitrate that fuels microalgal growth;
  3. to develop a model of circulation and residence time for Little Lagoon.

The following activities will be undertaken in Year 1 to fulfill these specific objectives:

  1. to characterize the physical, chemical and biological characteristics of Little Lagoon by continuing bi-weekly sampling with collaborators from the Little Lagoon Preservation Society (LLPS);
  2. to determine the abundance of specific Bacteroides genes in water samples demonstrated to have fecal coliforms present and identify potential sources of contamination;
  3. to characterize the E. coli community structure in water samples and potential sources of contamination;
  4. to determine the ð15N of nitrate in groundwater and likely sources to determine the source of nitrate;
  5. to deploy moorings for development and parameterization of a box-model of transport in the lagoon;
  6. to generate 2-D maps of the physical parameters of the lagoon at weekly (during mooring deployment) and monthly intervals (other months) for calibration and testing of the box model;
  7. to develop a preliminary box model based on the available data;
  8. to measure group-specific microalgal growth rates and grazing losses;
  9. to provide updates and progress reports to LLPS at quarterly meetings.

The following activities will be undertaken in Year 2 to fulfill these specific objectives:

  1. to characterize the chemistry and biology of Little Lagoon by continuing bi-weekly sampling with collaborators from the Little Lagoon Preservation Society;
  2. to determine the sources of fecal coliforms by analyzing all Bacteriodes and E. coli community data;
  3. to develop a multivariate ,decision-tree analysis relating microalgal community composition and blooms of Pseudo-nitzschia spp. to the physical and chemical characteristics of groundwater and the lagoon;
  4. to determine the abundance of specific Bacteroides genes in water samples demonstrated to have fecal coliforms present and identify potential sources of contamination;
  5. to characterize the E. coli community structure in water samples and potential sources of contamination;
  6. to determine the ð15N of nitrate in groundwater and likely sources to determine the source of nitrate;
  7. to deploy moorings for development and parameterization of a box-model of transport in the lagoon;
  8. to refine the preliminary box model based on new data;
  9. to run ‘what-if’ model scenarios of different configurations of the pass to estimate the effect on flushing;
  10. to integrate the residence time and growth rate data for recommended management action;
  11. to provide the data along with the analysis to the stakeholders and managers of Little Lagoon;
  12. to publish the findings of this study in the appropriate scientific journals.

Methodology

Bi-weekly monitoring: In collaboration with LLPS, monitoring of 4 stations will continue. This monitoring will include determining the fecal coliform numbers, temperature, salinity, dissolved inorganic nutrients (nitrate, nitrite, ammonium, phosphate and silicate), TN and TP, CDOM and microalgal chlorophylls and carotenoids. The bi-weekly sampling will be augmented with sampling from 2 or more wells adjacent to the lagoon, measuring the same suite of physical and chemical parameters.  Nutrient concentrations will be measured in filtered and unfiltered water (dissolved vs total pools) using a Scalar San+ autoanalyzer.  TN and TP will be measured in whole water oxidized with persulfate.  CDOM will be determined by absorption differences between whole and filtered (GF/F) water.  Microagal abundance and taxonomic compostion will be determined using Chla and marker pigments as measured with HPLC.  Pseudo-nitzschia spp. will be counted using light microscopy.
Fecal coliform counts: The number of fecal coliforms will be measured using the Coliscan Easygel selective agar (Micrology Laboratories, Goshen, IN), a modified Multiple Tube Fermentation (mMTF) method approved by the US EPA. Detection of counts above the regulatory threshold (200 CFU L-1) will be used as the criterion for further analyses using Bacteroidales host-specific qPCR and E. coli-specific PCR/DGGE.
Bacteroidales host-specific qPCR: Microbes will be concentrated from water samples (10-20 L) using tangential flow filtration and the DNA extracted.  qPCR will be carried out using the BacUni-UCD primer and probes to determine the total number of Bacteroidales genes.  Samples positive with this primer/probe set will be further analyzed with the BacHum-UDC (human), BacCow-UCD (agricultural) and BacCan-UCD (domestic animal) primers and probes.  All qPCR reactions will include a standard curve and samples in triplicate.
E. coli-specific-source analysis: Water samples positive for Bacteroidales will be fingerprinted using PCR/DGGE for three different genes in E. coli; ß-3D-glucuronidase (uidA), malate dehydrogenase (mdh) and outer membrane phosphoporin (phoE).  Sites around Little Lagoon will be sampled monthly to determine if they are sources of contamination.  Water samples will be processed using concentration and extraction, while DNA from sediments and sewage effluent will be extracted directly.  These samples will be fingerprinted and compared to water samples using the Gelcompar program from Applied Maths.
Nutrient source analysis: The same sources analyzed for E. coli PCR/DGGE will be analyzed to determine the source of the nitrate using ð15N analysis.  Samples will be concentrated and adsorbed onto a filter and analyzed at either the UC Davis Stable Isotope Laboratory or Coastal Science Laboratories (Austin, TX), depending on the cost structure.  All analyses carried out during bi-weekly sampling will be applied to these samples.
Moorings and mapping: To obtain data to build the mixing model, moorings (YSI probe to measure water level, salinity, temperature and turbidity) will be deployed at each of the 4 stations for 8 weeks during the spring.  A CDOM fluorometer will also be placed a one station.  During the mooring, weekly mapping of the lagoon will occur using a flow-though system with a YSI probe and CDOM fluorometer, WETLabs ac-9 spectral absorption and scattering sensor and Satlantic ISUS nitrate sensor. A total of 50 discrete samples will be taken from the ends and mid-point of each leg of the cross-lagoon transects, for measurement of nutrient concentrations, CDOM absorptin (aCDOM), and microalgal pigments.  Mapping will occur monthly when the mooring are not deployed.
Model forcing data: Forcing data required to develop the model will be obtained from nearby weather stations and moorings.  These includes wind and precipitation data from the Dauphin Island station and Middle Bay Light station (Mobile Bay National Estuary Program) and water level data from NOAA’s tide station at Dauphin Island (NOAA’s National Data Buoy Center).
Decision-tree analysis: A multivariate model will be derived from the monitoring data (groundwater and lagoon) and the micoalgal community composition (HPLC pigments and Pseudo-nitzschia spp. counts), using PRIMER-E software.  The environmental data will be compared between sites and sample-times by constructing a matrix of pair-wise similarity coefficients.  A second matrix will be based on pigments that are taxonomic markers and Pseudo-nitzschia spp. densities.  The environmental correlates of community composition will be tested using the BEST analysis, with permutative sub-sampling to identify the parameters with the highest explanatory power.  The taxonomic matrix will be classified by cluster analysis and the same clustering classification will be applied to the restricted dataset of environmental variables to construct a multivariate decision tree .  This will describe the combinations of environmental conditions during which shifts in community composition and HABs are most likely to occur.
Evaluation of residence time and effect on microagal growth: Once the model (either box or numerical) has been developed it will be analyzed using various forcing conditions to determine the effects of residence times and flushing times.  Cost/benefit analysis will be run on what-if scenarios, to evaluate potential management plans.  To evaluate flushing on microalgae, dilution experiments will be carried out to estimate the growth rate of microalgae.  These experiments will use the dilution technique of reduced grazing pressure to estimate in situ growth rates under natural conditions (no nutrients added) and in response to nutrient pulses (addition of nutrients).

Rationale

Harmful Algal Blooms (HABs) or Ecosystem-Disruptive Algal Blooms (EDABs and outbreaks of pathogenic organisms, such as fecal coliform bacteria (FCBs), have negative ecological impacts and potentially deleterious effects on human health.  Detecting HABs and FCBs and developing ecological models to predict and ultimately manage them is an explicit priority in NOAA’s 5- and 20-Year plans. These are also among the highest priorities within NOAA Gulf of Mexico Program’s Research Priorities and within the Gulf of Mexico Alliance’s Action Plan II. This proposal addresses the Sea Grant Focus Area of Healthy Coastal Ecosystems (1).

Little Lagoon is a poorly-flushed system in which contamination by FCBs occurs frequently, and in which dense and toxic blooms of Pseudo-nitzschia spp. occur during years in which there is high discharge from the aquifer in the spring. Because of the high recreational use of the water body, management of these problems must be considered.  The first is to reduce the delivery of nutrients and fecal contamination.  This may be effective if point sources can be identified, but may not be sufficient if the enrichment and contamination is due to non-point sources. The second approach is to alter the residence time and flushing of the lagoon.  Widening or deepening the pass or creating a second pass may be the simplest forms of remediation.  However, a hydrodynamic model is required for cost/benefit analysis and there is currently no reliable estimate of residence time for the lagoon.  This proposal will identify the most likely sources of fecal contamination and eutrophication (i.e. agriculture vs wastewater), which are necessary for selecting an appropriate management plan, and will develop the hydrodynamic model that is required for evaluating the effects of any management plan.

For More Information Contact: the MASGC Research Coordinator, Loretta Leist (Loretta.leist@usm.edu). 
Please reference the project number R/CEH-32.

Harmful Algal Blooms (HABs) or Ecosystem-Disruptive Algal Blooms (EDABs and outbreaks of pathogenic organisms, such as fecal coliform bacteria (FCBs), have negative ecological impacts and potentially deleterious effects on human health.  Detecting HABs and FCBs and developing ecological models to predict and ultimately manage them is an explicit priority in NOAA’s 5- and 20-Year plans. These are also among the highest priorities within NOAA Gulf of Mexico Program’s Research Priorities and within the Gulf of Mexico Alliance’s Action Plan II. This proposal addresses the Sea Grant Focus Area of Healthy Coastal Ecosystems (1).

Little Lagoon is a poorly-flushed system in which contamination by FCBs occurs frequently, and in which dense and toxic blooms of Pseudo-nitzschia spp. occur during years in which there is high discharge from the aquifer in the spring. Because of the high recreational use of the water body, management of these problems must be considered.  The first is to reduce the delivery of nutrients and fecal contamination.  This may be effective if point sources can be identified, but may not be sufficient if the enrichment and contamination is due to non-point sources. The second approach is to alter the residence time and flushing of the lagoon.  Widening or deepening the pass or creating a second pass may be the simplest forms of remediation.  However, a hydrodynamic model is required for cost/benefit analysis and there is currently no reliable estimate of residence time for the lagoon.  This proposal will identify the most likely sources of fecal contamination and eutrophication (i.e. agriculture vs wastewater), which are necessary for selecting an appropriate management plan, and will develop the hydrodynamic model that is required for evaluating the effects of any management plan.

For More Information Contact: the MASGC Research Coordinator, Loretta Leist (Loretta.leist@usm.edu). 
Please reference the project number R/CEH-32.