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Investigating and Examining Invertebrates Living in the Mud of Zones 1, 3, and 5 of the Ala Wai
Estuary
Team FarronTrons
(Farron Choe, Amber Alualu, John Zobian, Borys Pleskacz)
Abstract:
Our group investigated the different invertebrates living in zones 1, 2 and 3 of the Ala
Wai mud. We deployed a set of plates into the mud, gave them two weeks for a biofilm to form,
and collected them. Next our group filtered the invertebrates through a plankton net, scraped off
the plates, and examined under microscopes. We noted the different types of invertebrates and
their concentrations in zones 1, 3, and 5. Invertebrates that we discovered include amphipods,
nematodes, annelids, insect larvae, and copepods. We also found that there were no trends
showing different concentrations of specific invertebrates in certain zones, but there were slight
differences between the first two collections. The third collection yielded huge amounts of
amphipods due to the amount of rainfall and detritus in the water. There was a lot of inaccuracy
in our counting due to the detritus in the water, the difficulty of counting the specimens, and
other factors.
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Introduction:
Estuaries are semi-enclosed bodies of water where fresh and salt water mix. Salinity
levels can vary depending on the flow of fresh water sources and the tide of the ocean. Fresh
water is less dense and tends to float above the denser salt water. The time it takes for all the
estuary water to cycle is called flushing time. Estuaries are some of the most biologically
productive places on the planet, and are places for organisms to breed and find food. (Judith S.
Weis, 2008)
The food chain of estuaries is driven by the water plants, bottom-dwelling algae, and
other living organisms that convert the sun’s energy into food energy. After these plants and
algae go through their growth cycle and die, they’re covered by protozoa, fungi, bacteria, and
other microorganisms (detritus). These protozoa and microorganisms are in turn consumed by
invertebrates. Invertebrates are eaten by fish, and fish are consumed by birds and animals. Since
tides replenish oxygen levels for other living organisms in the ecosystem and bacteria and other
microorganisms use up a lot of oxygen, tides are essential to this cycle. (Judith S. Weis, 2008)
Amphipods have seven pairs of walking legs, four pairs that reach forward and five to
seven pairs that reach backward. The first pair of legs may also be modified in order to help
grasp food (claws). Amphipods are typically less than 10 millimeters long, however, there was
one rare case of a 28-centimeter amphipod that was found in the depths of the Atlantic Ocean.
The sizes of amphipods are limited by the availability of dissolved oxygen. There are two
different types of amphipods that are found in shallow marine environments: Caprellidae and
Gammaridae. Caprellidae have long, skinny bodies whereas the Gammaridae have bodies that
are flattened on each side. The diet of the amphipod depends on the habitat they live in. While
amphipods living on seaweed may be herbivores, amphipods that live in the Ala Wai feed off of
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detritus or scavenge off of dead animals or plants. In an ecosystem, amphipods are usually the
next step up from plankton and are eaten by fish. (Museum Victoria, accessed 2010)
Nematodes are one of the most abundant animals on the Earth. Nematodes are nonsegmented roundworms that have long and narrow simple structured internal body cavities called
pseudocoeloms. They can be free-living and predaceous, which means predatory or
parasitic. Free-living nematodes feed on either bacteria or fungus, while predaceous nematodes
eat all types of nematodes and protozoa. Other nematodes that are omnivores, including plant
parasites, are root-feeders. (Elaine R. Ingham, 1996) Nematodes can also can undergo
cryptobiosis, the ability to slow down or stop metabolic processes when they are in unfavorable
environmental conditions so that they can survive extreme aridity, heat, or cold, and then return
to their metabolic state of life when favorable conditions return. (David I. Shapiro-Ilan & Randy
Gaugler, accessed 2010)
Annelids, which are long cylindrical shaped worms, are a type of invertebrate that have a
body cavity (coelom), movable bristles (setae), and a body divided into segments. They do not
have appendages, antennae, or an obvious head end. This phylum is divided into three classes:
earthworms (Oligochaeta) and their relatives, leeches (Hirudinea), and a large number of marine
worms (polychaetes). Most earthworms feed on a wide variety organic matter, primarily detritus
and algae which can be found in the Ala Wai. As they feed they dispose what they do not need
in castings which are high in nutrients and in turn become food for other animals. (Bellarmine
University, accessed 2010)
Materials:

145mm by 152mm by 5mm wood plates, 6 attached by a screw with wood spacers in
between each plate
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
Rope and mini-buoy to float the rope attached to the plates

Buckets

Nets

Brushes to Scrape off Plates

Plankton Net

Petri Dishes

Pipettes

Microscopes
Procedure:
1. Deploy 1 set of plates in zones 1, 3 and 5. Allow a two week period for biofilm to accumulate
on the plates.
2. Prepare 3 buckets (one for each zone) and 3 fishing nets (one for each bucket).
3. Add water from one zone 1 into the bucket for zone 1.
4. Withdraw plates and be sure to hold the zone 1 net under the plates to catch any excess
organisms from falling out of the plates. Drop the zone 1 plates into the zone 1 bucket.
5. Repeats steps 3 and 4 with the remaining two zones.
6. Use a plankton net to extract the sediments and organisms from the water for one zone. Keep
filtering until all sediments and organisms from one zone is accounted for.
7. Once all sediments and organisms from one zone is in a petri dish, use a sterile pipette to
withdraw some zone matter (cutting the tips of the pipettes would help to withdraw more matter)
and examine under a microscope.
8. Use tank water to dilute the matter that is examined in order to view specimens clearer.
9. Once specimens are thoroughly examined and classified from one zone, discard specimens.
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10. Repeat steps 6 though 8 for the remaining two zones. (Specimens may be refrigerated to be
examined at a further time.)
Data:
1st Collection:
Zone 1
Zone 3
Zone 5
9 annelids (average length
0.5mm-10mm)
11 annelids
2 annelids
13 amphipods (1-2mm)
3 amphipods (1-5mm)
6 amphipods (2-4mm)
5 nematodes (0.5mm-1.5mm)
5 nematodes
1 nematode (2.5mm)
Pictures from Zone 1…
Zone 1 Nematode
Zone 3 Amphipod
2nd Collection:
Zone 1
*N/A*
Zone 3
0 annelids
*Zone 1 plates were lost 12 amphipods
due to heavy rainfall*
Zone 5
0 annelids
10 amphipods
4 pregnant amphipods 2 pregnant amphipods
1 nematode
1 nematode
1 Unknown fly larvae
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3rd Collection:
Zone 1
*N/A*
Zone 3
6 annelids
*Zone 1 plates were not 184 amphipods
Zone 5
11 annelids
215 amphipods
deployed due to lack of 8 pregnant amphipods 10 pregnant amphipods
plates*
0 nematodes
11 nematodes
1 Chironomid Larvae
1 Chironomid larvae
1 Copepod
0 Copepods
Pictures from Collection 3…
Zone 3 Copepod
Zone 5
Chironomid larvae
Zone 3 Pregnant
Amphipod
Zone 5 Pregnant Amphipod
Zone 3 Amphipod
Zone 5 Amphipod
Zone 5 Annelid
Discussion:
All three collection dates yielded different results. In comparison to the zero annelids and
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two nematodes found in the second collection, many annelids and nematodes were counted in the
first collection The number of amphipods stayed relatively the same between both collections,
considering the fact that we did not have plates for zone 1. This could be due to the fact that the
conditions during the first collection were prime for annelids and nematodes (both worm-like) to
reside on the plates. It could also be due to miscounting. The third collection yielded 17
annelids and 11 nematodes, which is more than collection two and close to collection one. The
number of amphipods, however, was in the hundreds due to the heavy rain occurring around the
time of collection three. The heavy rain could have caused more amphipods to cling to the plates,
or may have had something to do with the living patterns of amphipods in our section of the Ala
Wai (they may have flowed in from other sections or been unearthed from the mud by all the
rainfall). Also, since the amphipods feed off of detritus including decayed leaves and other debris
that could have been unearthed and brought into the zones because of the rain, we found
unusually large numbers of amphipods in the debris in our samples. This could also have
contributed to the 399 amphipods we counted in collection three, as opposed to collection one
and three each having 22 amphipods. The size of amphipods may be dependent on the amount
of dissolved oxygen in the water. It is possible that the rain dissolved more oxygen in the water,
allowing the amphipods in collection three to reach a larger size than in previous collections.
With more dissolved oxygen in the Ala Wai, more amphipods are able to inhabit the same area.
While examining the different invertebrates in zones 1, 3 and 5, it was observed that the
variety of invertebrates remained fairly the same throughout all three zones. Although we are
lacking two collections of zone 1, the numbers of discovered invertebrates seem very random
and show no trends as to whether specific invertebrates prefer specific zones.
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Furthermore, within these zones, unique characteristics of the invertebrates were
observed. While examining the amphipods, a wide variety of different amphipods were seen.
Some amphipods were pregnant, which was implied by the large sac of green colored eggs in the
abdomen area, other amphipods exibited different coloration or structural differences. Most
amphipods were pinkish or grayish in color; however, yellowish-golden colored amphipods were
also seen. Size differences many have occurred due to the age variations of the amphipods and
gender probably determined whether or not the amphipod would have claws. The large, fully
grown pregnant amphipods had small claws whereas other amphipods of the same size had large
claws. There were also amphipods with underdeveloped claws, but with large fins that allowed
those amphipods to swim quickly in the water. These noted differences existed probably because
different species of amphipods reside in the mud of the Ala Wai.
It is important to note, however, several experimental discrepancies may have lead to
error in counting the number of organisms found in each zone. Due to the small size of the
nematodes, we were not able to accurately count all of them. Many could have been missed or
thrown out due to the inexact nature of our procedure. Since the organisms were refrigerated, the
nematodes may have been mistaken for detritus. This same problem may have occurred with all
of the specimens, since these microorganisms were mixed with debris from the Ala Wai.
In addition, due to heavy rain storms that occurred throughout the time period the plates
were deployed in the water, plates tended to shift downward into other zones. As a result, in
collections 2 and 3, the data is slightly inaccurate since the zone 3 plate floated downward into
the next zone, zone 4. Thus organisms from the original zone and next zone the plates were in
could have been mixed together.
Another error would be due to our procedure. Since our group withdrew sample Ala Wai
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water from the surface and put it into the buckets before adding the plates, specimens could have
been in the surface water and may have affected our numbers.
Conclusion

We deployed wood plates with spacers into zones 1, 3, and 5 to sit for two weeks and
form biofilm. After two weeks, we collected the plates and examined the specimens on
them.

We found that there were no trends in specific invertebrates residing in certain zones, and
that the numbers seemed fairly random. Also, after heavy rainfall the number of
amphipods in the zones increased greatly.

Further experimentation can be done through conducting a more thorough analysis of the
invertebrates living in the Ala Wai mud. Multiple sets of plates can be deployed in each
zone in order to minimize error.

Given the time for more thorough research, a further more precise experiment could be
conducted. If students research exactly what each invertebrate eats, baited traps can be
used to study one specific invertebrate.

Our data probably could not be extrapolated to all other estuaries; however, our data does
give a better understanding of the organisms that live within the depths of our local Ala
Wai Estuary.
Works Cited
“Annelids.” Accessed Novermber 23, 2010. From Bellarmine University.
<http://cas.bellarmine.edu/tietjen/images/annelids.htm>
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“Annelida - worms and leeches.” Accessed November 23, 2010. From CSIRO Entomology
Home. <http://www.ento.csiro.au/education/allies/annelida.html>
David I. Shapiro-Ilan & Randy Gaugler. “Nematodes.” Accessed November 23, 2010. From
Cornell University's New York State Agricultural Experiment Station.
<http://www.nysaes.cornell.edu/ent/biocontrol/pathogens/nematodes.html>
Elaine R. Ingham. “Soil Nematodes | NRCS SQ.” (1996). Accessed November 23, 2010. From
NRCS Soils. <http://soils.usda.gov/sqi/concepts/soil_biology/nematodes.html>
Hinterland’s Who’s Who. “Estuaries. Habitat for Wildlife.” Accessed November 22, 2010. From
Canadian Wildlife Service. <http://www.hww.ca/hww2.asp?pid=0&id=226&cid=2>
“The Biology of Amphipods.” Accessed November 23, 2010. From Museum Victoria.
<http://museumvictoria.com.au/crust/amphbiol.html>
Waggoner, Ben. “Introduction to the Nematoda”. Accessed November 23, 2010. From
University of California Museum of Paleontology.
<http://www.ucmp.berkeley.edu/phyla/ecdysozoa/nematoda.html>
Weis, Judith S. “Estuary”. (2008). Accessed November 22, 2010. From The Encyclopedia of
Earth. <http://www.eoearth.org/article/Estuary#gen2>