Designing a Closed Ecological System to Support Animal

1
Designing a Closed Ecological System to Support
Animal Populations for Greater than 30
Days Palm Sized Ecosystems
Kristen Durance and Andrew Bryant University of
Washington Dr. Frieda Taub School of
Aquatic and Fishery Sciences University of
Washington Team Jessica Benthuysen, Andrew
Bryant, Patrick Cheung, Kristen Durance,
Hans-Karl Isern, Gavan Kaizawa-Miyata, Flora
Nisanova, Justin Phillips.
Introduction Closed Ecological Systems are
environments that have no or very little mass
exchange with their surroundings. The planet
earth -- a biosphere in which very little matter
enters from or exits to space fits this
category. Life is sustained by the cycling of
carbon, nitrogen, oxygen and other elements
throughout the planet, without exhausting them.
Scientists have developed small-scale models
of systems, in the laboratory, but since most of
them are open to and rely on inputs from the
outside, it is difficult to be aware of all
factors. We eliminate this problem by
developing systems that are closed to the
surrounding environment. They receive light
energy from outside but recycle all material.
Using CES to study the patterns and effects of
elements within an ecosystem allows us to not
only observe specific interactions, but to
replicate and reproduce experiments and results.
DESIGN PROBLEM Create closed ecological systems
that would last for more than 30 days. RESULT
Achieved!
http//www.micscape.simplenet.com/
mag/artjun99/wflea.html
Daphnia are freshwater filter feeding animals
All of our CES were constructed using 75mL tissue
culture flasks -- inexpensive, sealable
containers typically used to culture tissue
cells. These containers, unlike glass culture
tubes have an optically flat surface, so algae
and grazers can be observed under a dissecting or
inverted microscope. Each flask, both marine and
freshwater, was filled with water, media and
algae and allowed to sit open for 5 days. This
allowed for gas exchange and for any unexpected
organics to oxidize. The invertebrates were then
added and the flasks were placed in their
respective incubators.
Our small, closed ecological systems are a great
stepping stone for further research in the field.
Future investigations include creating larger
systems with slightly more complexity and varying
trophic levels. What we have learned from these
simple systems will help us to know what the
starting off point is for larger systems and what
limitations these organisms studied have in any
system. The data gathered in these experiments as
well as those done by pervious groups will allow
us to generate slightly more complex systems to
continually explore ecological concepts in the
future.
Saltwater Systems
Tigriopus is a marine animal
Methods Marine ecosystems were developed using
three algal species and a small marine
invertebrate grazer Tigriopus. Each system was
prepared with seawater and algal nutrients,
inoculated with algae and allowed to grow.
Tigriopus were inoculated into half of the
ecosystems and the containers were sealed.
Daylength was varied from 18, 12, 6 and 0 hours
light per 24 hours.
Freshwater Systems
http//www.uni-oldenburg.de/zoomorphology/Biology.
html
Nitrogen and Phosphorus Introduction
Experiment Purpose This study asked whether
the viability of closed ecological systems was
limited by the taking up of nutrients in the form
of daphnia carapaces, carcasses or in other
forms. It is thought that nutrients, especially
nitrogen, are removed from the systems in these
durable forms. Slightly open systems, into which
nutrients were added, were used to gain an
understanding of the limitations on entirely
closed ones.
Results Results show that different algal
species dominate ecosystems at different hours of
light. Tigriopus survival in zero hours of light
suggest that there may be slight light leaks
within the system allowing some oxygen
production, or that respiration has not depleted
the initial dissolved oxygen. At day-lengths of
18 and 12 hours there are algae present and a
shift in the species that dominate.
Method Nutrients were introduced into the
systems by means of syringes. The first nutrient
introduced was a Nitrate (NO3) solution, to test
whether nitrogen is taken out of the systems and
becomes a limiting factor. An NO3/PO4 solution
was injected into a second set of systems to
examine the possibility of phosphorus becoming a
limiting factor after nitrogen is introduced.
The third set of flasks was injected with Kent
water, acting as the control.
At day-length of 12 and 18 hours, no
Tigriopus hatched during the study, suggesting
that the increased amount of light was effecting
the Tigriopus survival either directly or
indirectly. The presence of babies at 6-hour
day-length suggests that this may be the most
optimal amount of light for these grazers.
Results Data suggests that Nitrogen is a
limiting factor in closed ecological systems
the health of algae was significantly higher in
systems where NO3 was introduced, and average
Daphnia population was slightly higher (fig. 4).
There were no indications that Phosphorus was a
limiting factor, and in fact systems with
nitrogen and phosphorus did, on average, worse
than those with only nitrogen.
Closed ecological systems are sold commercially
(see photos, above and below). Many claim to be
self-contained when in fact they require water to
be changed and nutrients to be added.
University of Washington
Dr. Clair E. Folsome
EcoSpheres (R)
Bio-Sphere (R)