Transcript Slide 1

Amy K. Cheatham, P.E.
Civil and Environmental Engineering
418 Durham Hall
The Impacts of Chemotherapeutics
on Nitrifying Bacteria in
Aquaculture Systems
Blacksburg, VA 24060
G.D. Boardman – Civil & Env. Eng.
S.A. Smith – VMRCVM
N.G. Love – Civil & Env. Eng.
G.J. Flick – Food Science & Technology
Background:
Hypothesis:
Results:
 U.S. aquaculture sales reached $1.1 billion in
 The nitrification process will be temporarily inhibited, but will recover quickly once treatments end
 Preliminary results indicate that for antibioticmedicated feeds, nitrification is inhibited during
active dosing, but recovers quickly once dosing stops
(see graph at left)
2005 – an increase of 11.7% since 1998 – and it is
anticipated that this growth will continue.
 Inhibition observed will be with respect to metabolic activity of the bacteria rather than with respect to
changes in the population composition or density
 Because aquaculture is a large-scale production
industry, disease is always a concern.
 Fluorescent in-situ hybridization (FISH) results
show that nitrifying bacteria are a very small
population within the biofilms that are formed in
aquaculture systems.
1.00
Pre-dosing
 Various chemicals are used to prevent disease
outbreaks, including antibiotics.
Dosing
Post-Dosing
0.90
0.80
 Nitrification plays a major role in aquaculture –
ammonia is toxic to fish at high levels, but always
present as a metabolic by-product.
TAN (mg/L)
0.70
 Discharge of nutrients, including nitrogen, one of
the major environmental concerns regarding
aquaculture effluents.
0.60
Romet
Control
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0.40
0.30
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Time (days)
Total Ammonia-Nitrogen (TAN) response to Romet-30® exposure
Methods:
Aquaria (20-gallons each) are set up using standard box filters and oxygen supplies and housing tilapia;
trials and controls all conducted in triplicate.
FISH image of aquaculture biofilm; blue-green –
ammonia-oxidizing bacteria, dark blue – other bacteria
 Chemotherapeutics are dosed in accordance with established guidelines.
Aquaria set-up for chemotherapeutic trials
Water quality is sampled before, during, and after the dosing periods to obtain a profile of the response and
recovery of the system. Most water quality parameters are analyzed using HACH reagents and methods.
1) To observe the impacts of common aquaculture
chemotherapeutics on:
 8-welled Teflon-coated microscope slides are suspended into the aquaria to collect samples of the biofilm
formed within the system. Slides are fixed immediately upon collection and processed using fluorescent insitu hybridization (FISH). FISH allows for the observation of shifts in the population composition and
density of the nitrifying bacteria as a result of the chemotherapeutic exposure.
 the water quality in an aquaculture system,
specifically with respect to nitrification
 Samples collected from filter and analyzed using specific oxygen uptake rates (SOUR). SOUR allows for
the observation of shifts in the activity of the nitrifying bacteria as a result of the chemotherapeutic exposure.
 the population density and metabolic activity
of the nitrifying bacteria in the aquaculture
system
 Number of samples is dependent on the dosing frequency of the chemotherapeutic being tested.
Objectives:
2) To determine if the impacts can be proactively
mitigated
Once data are obtained regarding the response of the nitrification process, experiments will be conducted to
determine if measures can be taken to proactively mitigate those impacts.
 Trials are currently being conducted using chelated
copper and formalin
 Future trials will be conducted using Chloramine-T
and potassium permanganate
Acknowledgements:
A special thanks to the U.S. Department of
Agriculture and Blue Ridge Aquaculture
(Martinsville, VA).