Final Report: An Assessment of Environmental Contaminant Levels in Water and Dragonfly Larvae Tissues from the Mobile/Tensaw Delta

EPA Grant Number: R830651C004
Subproject: this is subproject number 004 , established and managed by the Center Director under grant R827072
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: Alabama Center For Estuarine Studies (ACES)
Center Director: Shipp, Robert L.
Title: An Assessment of Environmental Contaminant Levels in Water and Dragonfly Larvae Tissues from the Mobile/Tensaw Delta
Investigators: Rice, Timothy M , Cioffi, Eugene A. , McCreadie, John W.
Institution: University of South Alabama
EPA Project Officer: Packard, Benjamin H
Project Period: September 1, 2004 through August 31, 2006
RFA: Targeted Research Center (2004) Recipients Lists
Research Category: Hazardous Waste/Remediation , Targeted Research


Mobile Bay, Mobile, AL, became a part of the country’s National Estuary Program (NEP) in 1995. Included in the NEP study area are the Bay proper and the Mobile/Tensaw Delta (MTD). The Delta comprises over 120,000 ha of cypress-gum swamps and bottomland hardwood forests, interlaced with streams, canals, bayous, and marshes. The Delta is the nation’s second largest river delta, much of which remains in a natural state. The Delta is of interest to both biologists and resource managers for a variety of reasons. First, it is one of the largest, intact, wetland ecosystems in the United States. Second, relatively little is known about large river systems, particularly in the South, when compared to our understanding of community structure and function of smaller, upland northern streams. Third, little is known about the biota of the MTD, particularly the invertebrate fauna. The southeastern United States has a high diversity of both plants and animals. Thus, it has been assumed that the Delta would also be a center of high diversity, especially in consideration of its relatively undisturbed state. However, this may not be the case.

Using Small Grants for Exploratory Research (SGER) funds provided by the Alabama Center for Estuarine Studies (ACES), the Total Insect Bio-inventory Project (TIBP) of the MTD was established in the spring of 2000. A preliminary assessment of the insect biodiversity of the lower MTD (i.e., below I-65) has been conducted under this program by McCreadie & Adler (The Paradox of the Delta: Protecting the Biodiversity We Do Not Yet Understand, ACES grant 06/30/2000 - 12/31/2002; Preliminary Survey of Both Aerial and Ground-Dwelling Insects, ACES grant 06/30/2001 - 12/31/2003). These studies indicate a disturbing low biodiversity in the lower MTD, which might indicate that this ecosystem, like many others on the planet, has suffered from various forms of anthropogenic disturbances. The drainage basin of the MTD covers over 75% of the state of Alabama. Hence, a variety of insults over this large area could be funneling into the Delta, which in turn may affect both the abundance and richness of the Delta’s flora and fauna. Recent studies have suggested that the health of aquatic ecosystems needs to be assessed using physical, chemical and biological parameters.

This project conducted an extensive survey of the water quality of the entire Mobile/Tensaw. Specifically, we tested for various groups of chemicals (heavy metals, total mercury, PCBs, and chlorinated pesticides) at 16 sites. In addition, we also examined the accumulation of these contaminants in animal tissue using the dragonfly larva Erythemis simplicicollis (Odonata: Libelullidae) as the model tissue.

The final objectives of this research project were to: (1) examine the spatial distribution of environmental chemicals (heavy metals, total mercury, PCBs, and chlorinated pesticides) in surface waters of the MTD, (2) examine the accumulation of heavy metals, total mercury, PCBs and chlorinated pesticides in tissues of larvae of the dragonfly E. simplicicollis; (3) establish standard techniques for analyzing a wide variety of environmental toxicants in surface waters and tissues at the University of South Alabama; and (4) create a current, accessible database of the water quality of the MTD.

The dragonfly E. simplicicollis was selected as our study animal for the following reasons: (1) E. simplicicollis is abundant in the MTD and easily identified. (2) E. simplicicollis is most common on submerged aquatic plants and thus constantly exposed to the water column. (3) Dragonfly larvae respire by sucking water internally into their hind-gut where gaseous exchange can occur over thin rectal gills. This would also provide the opportunity for water-borne toxicants to enter the body. (4) Dragonflies have fat bodies which will store and concentrate toxicants. (5) Dragonflies are predators, thus toxicants have the opportunity to concentrate in their tissues via biomagnification.

These objectives were pursued by hiring a graduate student to oversee the majority of the work in pursuit of a Masters Degree, and various undergraduate and graduate students as assistants to this student.

Summary/Accomplishments (Outputs/Outcomes):

Funds became available and a graduate student was selected as the research assistant in September 2004. Field work began immediately; 48 sites were selected within the Delta, but these were consolidated into 16 sites due to time and labor constraints. Eight sites were located North of I-65, and 8 were located South of I-65. Dragonfly larvae were all collected from patches of floating stargrass (Hypoxis) within the Negro Basin during summer 2005. Approximately 40 field trips were taken between September 2004 and September 2005 to collect water samples and dragonfly larvae. To assist the student during field work, one undergraduate and two graduate students were hired between January and December 2005. Research funding for the graduate student’s salary terminated after the first year of the project (September 2004-2005), but the student still continues on the project and is expected to complete a Masters Degree in summer or fall 2007. As of December 2005, all field samples for water analysis and sufficient samples of dragonfly larvae have been collected and are stored in the PI’s lab at the University of South Alabama.

Analysis of water and of larvae tissues for heavy metals has been completed. We have found detectable levels of lead, cadmium, and copper in the Mobile and Tensaw Rivers, but the majority of samples were within acceptable EPA criteria for protecting aquatic life. No differences in samples from North versus South I-65, or from Mobile versus Tensaw River, were observed. We have also measured detectable levels of these metals in whole larvae, but samples were low and we do not expect any acute toxic effects in the larvae based on these levels.

Analysis of water and of larvae tissues for total mercury has been performed. We are not yet equipped at the university to conduct our own mercury analyses, so the pre-processed samples were sent to a local contract laboratory (ACT Labs, Inc., Mobile). According to their analysis, total mercury levels in both water and larval samples were below instrumentation detection limits (0.2 μg/L). Although these data indicate that mercury is low in these samples, we intend to conduct further analysis with remaining samples.

Analysis of water samples for chlorinated organic compounds (PCBs and chlorinated pesticides) has begun and will continue. Preliminary analysis through gas chromatography indicated the presence of these compounds in the Mobile and Tensaw rivers. Future activity will include identification and quantification of specific compounds in these samples.

The original proposal had other objectives which we were not able to accomplish. We originally intended to measure methylmercury in water and tissue. However, there are no standard methods for analyzing this compound, and we do not yet have the instrumentation in place. Given that total mercury levels in samples are low, we are confident that methylmercury levels, being a proportion of these low total mercury levels, would be measured at levels below any criteria that would cause concern. We had also originally intended to compare contaminants levels with tidal flux. However, sampling from even 16 sites proved to be more time and labor-intensive than anticipated. Field work was conducted when weather and van/boat facilities permitted, regardless of tides or seasons.


These objectives were pursued with the assistance of undergraduate (Joshua Goff) and graduate (Christopher McQuillen, Kate Sheehan, Valerie Tollett) students who have received practical research training in the area of field sampling and analytical chemistry. Emphasis was placed on collection of field samples and processing/analysis of chemicals from these samples.

Acknowledgements and Disclaimers

This research has been supported by a grant from the U.S. Environmental Protection Agency’s Science to Achieve Results (STAR) Program, through ACES. Although the research described in this article has been funded wholly or in part by the U.S. Environmental Protection Agency’s STAR Program (EPA # R-83065101-1-03), it has not been subjected to any EPA review and, therefore, does not necessarily reflect the views of the Agency. No official endorsement should be inferred.

Supplemental Keywords:

gulf coast, biology, environmental chemistry, analytical, toxics, PCBs, heavy metals, mercury,

Relevant Websites: Exit

Progress and Final Reports:

Original Abstract
  • 2005

  • Main Center Abstract and Reports:

    R827072    Alabama Center For Estuarine Studies (ACES)

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R827072C001 Fluorescent Whitening Agents As Facile Pollution Markers In Shellfishing Waters
    R827072C002 Red Snapper Demographics on Artificial Reefs: The Effect of Nearest-Neighbor Dynamics
    R827072C003 Stabilization of Eroding Shorelines in Estuarine Wave Eliminates with Constructed Fringe Wetlands Incorporating Offshore Breakwaters
    R827072C004 Interaction Between Water Column Structure and Reproduction in Jellyfish Populations Of Mobile Bay (SGER)
    R827072C005 Effects of Variation in River Discharge and Wind-Driven Resuspension on Higher Trophic Levels in the Mobile Bay Ecosystem
    R827072C006 Results of Zooplankton Component
    R827072C007 Benthic Study Component
    R827072C008 A Preliminary Survey of Macroalgal and Aquatic Plant Distribution in the Mobile Tensaw Delta
    R827072C009 Fisheries-induced changes in the structure and function of shallow water "nursery habitats": an experimental assessment
    R827072C010 Effects Of Variation in River Discharge and Wind-Driven Resuspension on Lower Trophic Levels of the Mobile Bay Ecosystem
    R827072C011 Evaluation of Alabama Estuaries as Developmental Habitat for Juvenile Sea Turtles
    R827072C012 Effects of Salinity Stress on Natural and Anthropogenically-Derived Bacteria in Estuarine Environments
    R827072C013 The Role of Land-Use/Land-Cover and Sub-estuarine Ecosystem Nitrogen Cycling in the Regulation of Nitrogen Delivery to a River Dominated Estuary; Mobile Bay, Alabama
    R827072C014 Environmental Attitudes of Alabama Coastal Residents: Public Opinion Polls and Environmental Policy
    R827072C015 Synthesis and Characterization of an Electrochemical Peptide Nucleic Acid Probe
    R827072C016 Determinants of Small-Scale Variation in the Abundance of the Blue Crab Callinectes Sapidus
    R827072C017 Effects of Estrogen Pollution on the Reproductive Fitness of the Gulf Pipefish, Syngnathus scovelli
    R827072C019 A Model for Genetic Diversity Aquatic Insects of the Mobile/Tensaw River Delta
    R827072C020 Evaluating Trophic Processes as Indicators of Anthropogenic Eutrophication in Coastal Ecosystems: An Exploratory Analysis
    R827072C021 Effects of Anthropogenic Eutrophication on the Magnitude and Trophic Fate of Microphytobenthic Production in Estuaries
    R827072C022 Characteristics of Ship Waves and Wind Waves in Mobile Bay
    R827072C023 Methods Comparison Between Stripping Voltammetry and Plasma Emission Spectroscopy for Metals in Mobile Bay
    R827072C024 Changes in Water Conditions and Sedimentation Rates Associated With Construction of the Mobile Bay Causeway
    R827072C025 Cold-Induced Hibernation of Marine Vibrios in the Gulf of Mexico: A Study of Cell-Cell Communication and Dormancy in Vibrio vulnificus
    R827072C026 Holocene Sedimentary History of Weeks Bay, AL: Human and Natural Impacts on Deposition in a Gulf Coast Estuary
    R827072C027 Shelter Bottlenecks and Self-Regulation in Blue Crab Populations: Assessing the Roles of Nursery Habitats and Juvenile Interactions for Shelter Dependent Organisms
    R827072C028 Predicting Seagrass Survival in Nutrient Enriched Waters: Toward a New View of an Existing Paradigm
    R827072C029 DMSP and its Role as an Antioxidant in the Salt Marsh Macrophyte Spartina alterniflora
    R827072C030 A Preliminary Survey of Aerial and Ground-Dwelling Insects of the Mobile/Tensaw Delta
    R827072C031 Natural Biogeochemical Tags of Striped Mullet, Mugil cephalus, Estuarine Nursery Areas in the North Central Gulf of Mexico
    R827072C032 Resolution of Sedimentation Rates in Impacted Coastal Environments Using 137Cs and 210Pb Markers: Dog River and Fowl River Embayments
    R827072C033 Investigation of the Use of Pulse Amplitude Modulated (PAM) Fluorometry as an Indicator of Submerged Aquatic Vegetation Health in Mobile Bay
    R827072C034 Influence of Invasive Plant Species in Determining Diversity of Aquatic Vegetation in the Mobile-Tensaw Delta
    R827072C035 The Influence of Shallow Water Hydrodynamics on the Importance of Seagrass Detritus in Estuarine Food Webs
    R827072C036 Food Web Interactions, Spatial Subsidies and the Flow of Energy Between the Mobile Bay Delta and Offshore Waters: A SGER Proposal to the Alabama Center for Estuarine Studies
    R830651C001 Meteorological Modeling of Hurricanes and Coastal Interactions: A Stability Study For Vertical Pressure Levels
    R830651C002 Characterization of Glycoprotein Cues Used by the Parasitic Rhizocephalan Barnacle Loxothylacus texanus To Identify Its Blue Crab Host, Callinectes sapidus
    R830651C003 Survey of Diamondback Terrapin Populations in Alabama Estuaries
    R830651C004 An Assessment of Environmental Contaminant Levels in Water and Dragonfly Larvae Tissues from the Mobile/Tensaw Delta