2002 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, 2001 through September 30, 2002
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


The overall objective of this research project is to characterize the microbial community structure and function, in different salinity regimes of the Bay, using classical and modern molecular techniques. The specific objective of this research project is to examine how salinity stress affects both natural and introduced bacteria in the Mobile Bay Estuary.

Bacteria are among the most important components of ecosystems because they perform most of the heterotrophic metabolism and nutrient regeneration. Knowledge of what controls the growth of specific bacterial groups in estuaries presently is very limited, but is 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. The effects of salinity stress on bacterial metabolic activities, especially degradation of organic matter (natural and pollutant) are being tested. The physiological responses of bacteria to osmotic stress are being examined, particularly with regard to uptake of osmotic solutes from the water. The investigator hypothesizes that bacteria experiencing salinity (osmotic) stress will be able to mitigate that stress by taking up exogenous osmolytes such as glycine betaine and DMSP.

Progress Summary:

The relationship between bacterial activity and salinity in Mobile Bay is not straightforward. However, some sampling transects along the main axis of the Bay showed markedly decreasing rates of bacterial biomass production as salinity increased. In laboratory experiments, we found that acute salinity stress of +5 or +10 parts per thousand decreased bacterial biomass production, as measured by 3H-leucine incorporation. These sample experiments showed that simultaneous supplements of low concentrations (20 nM) of the osmolyte glycine betaine relieved the imposed salinity stress. This suggests that native estuarine bacteria can take up exogenous osmolytes for the purposes of compensating for hyperosmolarity, in such a way that allows them to maintain growth rates similar to nonstressed cells. The inhibition of bacterial production caused by experimental increases in salinity stress was more or less directly dependent on the magnitude of salinity increase.

We also examined the time dependence of the inhibition. Results from some of these experiments suggested a rapid inhibition upon increases in salinity, followed by a rapid recovery. For these experiments, the bacteria may have recovered because they took up naturally occurring extracellular osmolytes (as our other experiments indicated they could), or they rapidly synthesized intracellular osmolytes that compensated for the stress. In other experiments, we found acute salinity stress inhibited bacterial production with no observed recovery during periods of up to 6 hours after the stress. Either exogenous osmolytes were not available during these experiments, or different populations of bacteria were present that were more susceptible to the stress. Future experiments will be directed at understanding why these differences were observed. Key to these analyses will be genetic analysis of bacterial population structure. With help from this Alabama Center for Estuarine Studies funding, we have acquired the necessary equipment to address these questions.

Future Activities:

There are still some incomplete objectives of this project, which will be addressed during summer and fall 2003. In particular, we want to examine the genetic structure of bacterial populations in different salinity regimes and during different seasons in Mobile Bay. This work will help in understanding the function of the bacterioplankton community in the Bay ecosystem, and also enable a better understanding of how they respond to environmental stresses. Additional work will include experiments in which the biovolume of natural bacterioplankton is monitored during osmotic stress. We hypothesize that bacteria will shrink when exposed to an osmotic stress, and that they may recover biovolume upon administration of exogenous osmolytes. Instrumentation to make these measurements is now available.

Journal Articles on this Report : 1 Displayed | Download in RIS Format

Other subproject views: All 1 publications 1 publications in selected types All 1 journal articles
Other center views: All 86 publications 5 publications in selected types All 5 journal articles
Type Citation Sub Project Document Sources
Journal Article Kiene RP, Axell M. Response of estuarine bacterioplankton to acute osmotic stress. Applied and Environmental Microbiology. R827072C012 (2002)
not available

Supplemental Keywords:

osmoregulation, biovolume, bacterioplankton, microbial community structure and function, salinity regimes, natural and introduced bacteria, salinity stress, exogenous osmolytes, glycine betaine, DMSP, hyperosmolarity, extracellular osmolytes, intracellular osmolytes, ecosystem, ecosystem protection, ecology, ecological effects, ecological indicators, environmental exposure, water, aquatic ecosystem, coastal ecosystem, coastal environments, estuary, estuaries, estuarine research, estuarine waters, environmental chemistry, chemistry, risk, assessment, indicators, Alabama, AL, human modifications., RFA, Scientific Discipline, Geographic Area, Water, ECOSYSTEMS, Ecosystem Protection/Environmental Exposure & Risk, estuarine research, Aquatic Ecosystems & 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, anthropogenic stresses, wetlands, coastal ecosystem, eutrophication, anthropogenic stress, water use, estuaries, watersheds, Mobile Bay, salinity stress, nutrients, natural bacteria, coastal environments, ecosystem, water quality, estuarine waters, human modifications, bay ecosystem

Relevant Websites:

http://www.southalabama.edu/aces/ Exit
http://www.disl.org Exit

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