Lecture 6: Responses of a Marine Microbial Community to Petroleum Hydrocarbon Exposure
Gaytha A. Langlois, Ph.D.
Site
Map
Condylostoma
sp.
- an oil-tolerant marine ciliate
Role
of Protozoa in Aquatic Food Chains
Bacteria and protozoa
may account for 50% of benthic respiration
Protozoa show diverse
patterns of interspecies interactions
Elaborate predator/prey
relationships may be altered by perturbations
Effects
of Land Use on Island Ecosystems
Greater human activity
may result in increased contact with mainland species
Increased development
may bring pollution and/or change evolutionary dynamics
Pollution events such
as oil spills may alter biotic communities significantly
Leaking underground
storage tanks also produce long-lasting impacts
Overview
- Oil Contamination Study on Prudence Island
Background Information
Prudence Island (“Chibacuwese”)
located in Narragansett Bay - purchased in 1637
South end of island
is protected from further development; part of the National Estuarine Sanctuary
Program
Samples taken at T-wharf
(41o34’53”N, 71o19’18”W)
U.S. Navy fuel depot
site, resulting in fuel tank leakage and a subsequent bioremediation project
by the Army Corps
of Engineers (completed in 2001)
Prudence Island Site
Overview
- Oil Contamination Study (continued)
Description of Observations
Samples taken from
2 sandy beaches near bioremediation area (1999-Present)
Samples taken from
top 1 cm. sediment
Physical parameters
recorded (temperature, salinity, dissolved oxygen)
Hydrocarbon analysis
conducted 2000-2001
Phase Contrast Microscopy
(live observations of protists and microalgae)
Hypotheses
Petroleum HCNs will
be similar to compounds found in the bioremediation area
Volatile organic compounds
will be high as a result of biosparging technique
Oiled communities
will resemble those found in earlier mesocosm studies
Mesocosm
Studies at MERL
MERL (Marine Ecosystems
Research Laboratory), Graduate School of Oceanography, University of Rhode
Island
3-year study of the
effects of petroleum hydrocarbons on estuarine/marine ecosystems
General
Findings from Studies at the Prudence Island Site
Oil/gasoline residues
are visible in the intertidal zone
Petroleum HCNs found
in intertidal zone are similar to profiles for nearby monitoring wells
in bioremediation area
VOCs are present in
intertidal samples (BTEX profile), indicating presence of residues of gasoline
Changes
in Biotic Community
Microbial communities
are similar to those found in other oil contaminated sites (emergence of
large, diatom-eating ciliates; reduced numbers in selected microinvertebrate
populations; high numbers of diatoms)
Patterns are similar
to those found in previous MERL studies and elsewhere
Oiled microbial communities
are characterized by different species groupings, and show
altered community
structure and trophic dynamics
Studies are ongoing;
database will remain accessible via a Web Site (including previous field
and mesocosm studies)
Figure 1: Changes in
Populations in Control & Oiled Marine Microbial Communities
(see Handout)
Table II. Comparison
of Indicator Species in Control & Oiled Habitats
(see Handout)
Summary
Community responses
to petroleum contamination are complex
Restructured communities
may survive, but are not necessarily aligned with the natural food web
More research is needed
Check on ongoing results
at http://web.bryant/~langlois/islands