2000 Progress Report: Effects of Salinity Stress on Natural and Anthropogenically-Derived Bacteria in Estuarine Environments

EPA Grant Number: R827072C012
Subproject: this is subproject number 012 , 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: Effects of Salinity Stress on Natural and Anthropogenically-Derived Bacteria in Estuarine Environments
Investigators: Kiene, Ronald P.
Institution: University of South Alabama
EPA Project Officer: Packard, Benjamin H
Project Period: October 1, 1999 through September 30, 2000
Project Period Covered by this Report: October 1, 1999 through September 30, 2000
Project Amount: Refer to main center abstract for funding details.
RFA: Alabama Center For Estuarine Studies (ACES) (1999) RFA Text |  Recipients Lists
Research Category: Ecological Restoration , Targeted Research


Bacteria are among the most important components of ecosystems because they carry out most of the heterotrophic metabolism and nutrient regeneration. Knowledge of what controls the growth of specific bacterial groups in estuaries is presently very limited, but of great concern from a management standpoint. Aquatic bacteria are the first line of defense in coastal ecosystems because they have the potential to mitigate the detrimental effects of certain anthropogenic pollutants, through degradation and transformation of these harmful compounds. Despite the importance of bacteria to the overall health of estuaries, the influence of changing osmotic conditions on natural bacterial populations is poorly known.

The goals of this project are to examine how salinity stress affects both natural and introduced bacteria in the Mobile Bay Estuary.

Progress Summary:

Work carried out to date has focused on the response of natural populations to salinity stress. Transects carried out along a salinity gradient down the central axis of Mobile Bay showed that bacterial production was sometimes negatively correlated with salinity. This pattern could be due to differences in availability of organic matter to the bacteria or it could be due to physiological stress imposed by salinity transitions. Natural assemblages of bacterioplankton (filtrate fractions < 1 mm) from Mobile Bay were experimentally subjected to salinity stress by addition of organic-free NaCl and the response of bacterial biomass production (3H-leucine incorporation) was measured. Populations from low salinity regions of the Bay, where ambient salinity was 2 ppt, were highly susceptible to short-term salinity stress, with biomass production being inhibited 50% by a 5 ppt salinity increase. Inhibition was progressively greater at +10 and +15 ppt, and was nearly complete at +15 or +20 ppt. Populations from water with an ambient salinity of 19 ppt, showed a lower response to salinity stress, being only slightly inhibited by +5 ppt treatment and 40% inhibited by + 20 ppt treatment. In the tests that showed strong inhibitory effects of salinity stress, the bacterial biomass production did not recover from the stress over a 6 h incubation period. These findings suggest that bacterial populations from mesohaline waters are proportionally less susceptible to salinity stress than populations from the oligohaline regions of the Bay.

In some water samples collected throughout the year, especially those from shallow sites or during sediment resuspension events, salinity stress produced remarkably little effect on bacterial biomass production. We were interested to learn whether naturally-available organic compounds might serve as osmoprotectants under these circumstances. To begin to address this question, we carried out experiments with populations that were susceptible to salinity stress and we added small amounts (20 nM) of compounds known to be bacterial osmoprotectants. The addition of 20 nM concentrations of glycine betaine (GB), a well known osmolyte, substantially relieved inhibition caused by +5 or +10 ppt salinity stress in short-term experiments, whereas addition of GB to non-stressed samples had no effects on bacterial biomass production. These results suggest that bacteria experiencing osmotic stress in an estuary could relieve this stress by taking up osmoprotectants from the surrounding water, a novel finding. Susceptibility of populations to salinity stress may therefore depend strongly on the pool of dissolved organic matter available to them, particularly the availability of specific compounds that can function as osmoprotectants. Ongoing work is aimed at determining which compounds are used in situ.

In future work the effects of salinity stress on bacterial metabolic activities, especially degradation of organic matter (natural and pollutant) will be tested. A long term goal of this and other ongoing studies is to characterize the microbial community structure, using classical and modern molecular techniques, and to relate this information to the function of bacteria in the estuary.

Journal Articles:

No journal articles submitted with this report: View all 1 publications for this subproject

Supplemental Keywords:

estuarine research, coastal ecosystem, human modifications, water use, watersheds, aquatic ecosystems, bay ecosystem, nutrients, salinity stress, anthropogenic stress., RFA, Scientific Discipline, Geographic Area, Water, ECOSYSTEMS, Ecosystem Protection/Environmental Exposure & Risk, Aquatic Ecosystems & Estuarine Research, estuarine research, Ecosystem/Assessment/Indicators, Ecosystem Protection, Chemistry, Restoration, Aquatic Ecosystem, Ecological Effects - Environmental Exposure & Risk, Aquatic Ecosystems, Ecological Effects - Human Health, Ecology and Ecosystems, Aquatic Ecosystem Restoration, Gulf of Mexico, Ecological Indicators, coastal ecosystem, eutrophication, anthropogenic stress, anthropogenic stresses, wetlands, water use, Mobile Bay, watersheds, salinity stress, estuaries, nutrients, natural bacteria, coastal environments, ecosystem, estuarine waters, water quality, human modifications, bay ecosystem

Progress and Final Reports:

Original Abstract
  • Final

  • 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