Unit 3 (part 7): Contamination of Algal Cultures
Concepts: Students will explore the concept of organic contaminants in an algal
culture and will learn about methods of controlling these contaminants.
Objective: The purpose of this lesson is to discuss the possible types of organic
contamination in an algal culture, explain what can happen if such contamination
exists, and learn about methods of controlling that contamination.
Summary: Algal cultures can be contaminated by other organisms in the form of
consumers, pathogens, or parasites. Such a contamination may result in the loss of
a production crop and a disruption of biofuel production. With large production
facilities for algal culturing in their early development stages, there are few studies
that have been completed regarding the protection of algal cultures from such
contaminants. We will discuss possible methods of protection currently available
and we will also look at methods used in aquaculture (fish farming) to protect
those environments from contamination.
Useful Websites:
http://en.wikipedia.org/wiki/Fish_disease
http://en.wikipedia.org/wiki/Pathogen
http://en.wikipedia.org/wiki/Parasite
http://www.thefishsite.com/articles/43/fish-diseases-in-aquaculture
http://tal.ifas.ufl.edu/publications.htm
Materials:
Beaker
Dark food coloring
© 2010, Ohio Northern University: Dr. Debra Gallagher, Dr. Robert Verb, Dr. Ken Reid and Ben McPheron
Activity Sheets:
Contamination Presentation Peer Assessment
Engage:
1. Begin the class by having a large beaker filled with water
a. Say: This water represents an algal culture. Its colorless clarity
represents the purity of the sample. That means: this sample is a pure
algal culture with no outside contaminants
b. Explain: this food coloring represents a contaminant. Drop a few
drops of food coloring into the beaker and let the coloring dissipate
c. As the coloring dissipates throughout the water it will change the hue
of the water and the solution will no longer be colorless
d. Explain: now that a contaminant has been introduced, the culture is no
longer pure. The contaminant can spread as it wishes and will
damage or even kill the algal culture. All in all, this will reduce the
yield of the culture. If let go long enough, the contaminant will affect
the entire culture.
e. If we had acted immediately, we could have ‘harvested’ the
contaminated culture and saved some of the pure culture
Explore:
1. There are several different possible contaminants. These are listed in the
Teacher Background section with more information. Explain the
information from the Teacher background section about each of these
contaminants.
a. Protozoan algal herbivores
b. Invertebrate algal herbivores
c. Vertebrates
d. Fungi
e. Bacteria and Viruses
2. Break the students into four small groups and assign one of each of these
contaminants to each group. Give them ~10 minutes to discuss how each of
these contaminants can harm an algal culture and what the long term impact
of each of the contaminants could be (ignore vertebrates)
© 2010, Ohio Northern University: Dr. Debra Gallagher, Dr. Robert Verb, Dr. Ken Reid and Ben McPheron
Explain:
1. Have each small group explain how their assigned contaminant could be
harmful to an algal culture.
2. Discuss known methods of control to protect algal cultures.
a. Vigilant monitoring: immediate harvest if contaminant is detected
b. In the case of extreme epidemics of consumers/pathogens, complete
draining and decontamination of bioreactor may be necessary
c. Explain that there is not much research on protecting algal cultures,
but that there are methods of protecting fish from contamination in the
field of aquaculture. These methods are generally not effective in
protecting algae as they typically kill the algae as well as the
pathogens or parasites
Extend:
1. Keep the students in their small groups and assign the group that already
discussed pathogens (bacteria and viruses) as well as one of the other groups
to research controlling pathogens in aquaculture, and the group that
discussed at fungus (parasites) and the last remaining group to research the
control of parasites in aquaculture
a. Information of interest includes:
i. Types of contaminant (more detailed)
ii. Methods of control
iii. Impact on fish (crop of aquaculture) if the contaminant is left
uncontrolled
2. Have the (two sets of) two groups that independently researched the same
topic meet together and discuss the information that they found
3. Have those combined groups create a short (3-5 minutes)
presentation/discussion to describe what they found. Give the groups copies
of the peer assessment so that they can see how they will be graded and
prepare their presentation accordingly.
© 2010, Ohio Northern University: Dr. Debra Gallagher, Dr. Robert Verb, Dr. Ken Reid and Ben McPheron
Evaluate:
1. Have the students use the peer assessments at the end of this lesson to grade
the presentations. Teacher should use an assessment as well. Student
grading will account for 50% of grade, teacher grading for the other 50%.
© 2010, Ohio Northern University: Dr. Debra Gallagher, Dr. Robert Verb, Dr. Ken Reid and Ben McPheron
Teacher Background:
Contamination of algal cultures
Algal cultures (either mixed communities or monocultures) are subject to
contamination by other organisms. There is a diverse list of freshwater organisms
that feed on algae and utilize them as a primary energy source. Organisms range
from the microscopic (protozoans) to the large (fish) could potentially feed on
algae. While it is unlikely that some of these organisms would naturally colonize
algal cultures (e.g., fish) there are many organisms that are capable of actively or
passively dispersing themselves or their propagules. These are the organisms most
likely to cause disruption to algal cultures being reared to produce biofuels. Listed
below are some general classifications of these organisms.
Protozoan Algal Herbivores
Many protozoan algal herbivores (including some species of algae) serve as
important grazers of algae in natural environments. These include groups such as
euglenoids, cryptomonads, certain chlorophytes, dinoflagellates, chrysophytes,
amoebae (e.g., Amoeba), and ciliates. Ciliates can be rather prolific consumers of
algae and are often divided into three ecological feeding groups: 1. Raptorial
feeding (Urotricha) 2. Filter feeders (Vorticella); 3. Coarse filter feeders and
Detritivores (Coleps) (Simek et al., 1996).
Invertebrate Algal Herbivores
Zooplankton filter feeders such as cladocerans (abundant) and copepods (rare) are
effective feeders on phytoplankton. These organisms reach their peak abundance
during the spring and summer months. They generally feed on smaller sized algae
such as diatoms.
A large assemblage of macroinvertebrates (often classified as grazers/scrappers)
can be important (and aggressive) direct feeders/users on algae. These include, but
are not limited to, snails, caddisfly larvae, crayfish, and mollusks. Some, like
snails, use their mouthparts to remove attached algae directly from surfaces.
Others, such as freshwater mollusks, are more adept at removing algae directly
© 2010, Ohio Northern University: Dr. Debra Gallagher, Dr. Robert Verb, Dr. Ken Reid and Ben McPheron
from the water column. Lastly, some groups, such as caddisfly larvae, may not
only feed on algae, but also incorporate algal filaments into their cases.
Vertebrates
While unlikely contaminators of algal cultures, it should be noted that some
vertebrates, such as stonerollers and tadpoles, can feed on algal communities.
Fungi
Fungi are heterotrophic eukaryotes that are capable to feeding on live algae (acting
as parasites) or consuming dead algal material (saprobes). Fungi often form
filamentous masses know as mycelia and will use digestive enzymes to break
down organic material. There are two major groups of fungi that may
attack/consume algae, the Chrtridiomycota and biflagellated fungi belonging to the
Oomycota (not a true fungus). Parasitic members of both fungal phyla can cause
epidemics in natural systems, so it is likely that the same could occur in culture.
Data indicates that diatoms and green algae are most susceptible to these fungal
attacks.
Bacteria and Viruses
Microbial pathogens, such as bacteria and viruses, can have an influence on algal
distribution and abundance in aquatic systems (Peterson et al, 1993). Infections
can cause death through cell lysis. The production of large quantities of dead algal
biomass may be based on phenology rather than environmental triggers. (Peterson
et al, 1993). Epidemic conditions have been reported from both periphyton and
phytoplankton communities (van Donk and Ringleberg, 1983; Caiola and
Pellegrini, 1984; Peterson et al, 1993).
Control
Given the developmental status of large scale algal culturing, there has not been
much research dedicated to the impacts and potential control of algal consumers
and pathogens. Future research may reveal mechanical or chemical techniques that
assist in the control and elimination of some of these organisms. As of this point in
time, the best practice involves vigilant monitoring of an algal culture and
immediate harvest if an outbreak is detected. For extreme epidemics of
© 2010, Ohio Northern University: Dr. Debra Gallagher, Dr. Robert Verb, Dr. Ken Reid and Ben McPheron
consumers/pathogens, complete draining and decontamination of the mesocosm or
bioreactor may be necessary.
© 2010, Ohio Northern University: Dr. Debra Gallagher, Dr. Robert Verb, Dr. Ken Reid and Ben McPheron