Is there a relation ship between rainfall and invertebrates living in

Correlation between amount of rainfall to
the different types and amount of anthropods
and annelids found in the Ala Wai Canal in
Zone 4
Fish are Friends Not Food
Lauren Chinen, Drew Matsuura, Tiffanie Takeda, Darin Poei, John
In our Ala Wai Project, we attempted to find a correlation between the amount of rainfall in the
various zones of the Ala Wai Canal, and the amount of anthropods and annelids found in these
zones. We utilized the Lamotte stainless steel bottom-sampling dredge to collect our samples and
used a stick to further dredge the bottom sampler into the mud to collect a sufficient amount of
mud. From our data collection, we realized that annelids and anthropods are mostly located on
the surface of the river bottom. We found more annelids than anthropods because annelids can
survive in conditions with lower amounts of oxygen. At the end of our experiment, we
concluded that there is no correlation between the amount of rainfall and organisms in the Ala
Wai Canal because we could not find a pattern within our data. Possibly, if we continue to trial
we could come to a definite conclusion finding whether there is a direct correlation between the
rainfall and the amount of organisms in the mud.
Final Project Question:
Are there any correlations between the weather conditions and the number of anthropods
and annelid worms found in Zone 4?
Background and Research
For our project, the purpose of our investigation was to determine whether there were any
correlations between the amount of rainfall and the amount of anthropods and annelid worms
found in the mud of Zone 4. The Ala Wai Canal is an estuary; a coastal region where freshwater
meets salt water. The canal was originally constructed to drain wetlands 1-2 kilometers behind
the Waikiki shoreline. The wetlands were crossed and fed by the two major streams that drain
Manoa, Palolo, and Makiki valley. Over recent studies, the canal showed major productivity
driven by high levels of silica, phosphate, nitrate, and ammonia. The concentration of inorganic
nitrogen and phosphorous tend to be higher after storms have occurred. The increased level of
phosphorous is anoxic causing a severe depletion of oxygen, thus affecting the aerobic organisms
through the imbalance of water’s conductivity (Missouri Department of Natural Resources).
Conductivity indicates the presence of inorganic dissolved substances, thus displaying the water
The amount of rainfall can also affect the organisms in the water specifically. The water
contains dissolved oxygen, thus as the ponds lose water, the organisms in the water become more
confined to a smaller volume of water and are under stress. As evaporation of the water
continues without being replenished by rainfall, the waste metabolites become concentrated and
the water becomes more polluted with ammonia, carbon dioxide and nitrates. Thus, if the
environment becomes unsuitable because of the lack of rainfall, the organisms will not
survive. With little to no dissolved oxygen present in the water, the aerobic organisms cannot
thrive because oxygen is required for those organisms for energy production (Lewis, 2012). Also,
increased levels of rainfall may have a similar effect. More rainfall may wash away vital
nutrients and alter the natural and optimal habitat of certain organisms. This will lead to lower
amounts of organisms found surviving in the area. The increase in rainfall may also bring
additional runoff from inland valleys and streams which may cause debris and change the
habitats of the organisms and might kill them. Variations in the rainfall will cause the water level
and water composition to change, which will alter the composition of our mud samples, and most
likely affect the types and frequencies of organisms that we obtain.
Within the mud, we are searching for annelid worms. Limnodrilus hoffmeistriis, one of
many species of aquatic worms, is also called oligochaetes. Aquatic worms are close relatives of
earthworms, but they live in water instead of on land. Many aquatic worms tolerate low
dissolved oxygen and can live in polluted habitats.(SWCSMH, 2006) Limnodrilus hoffmeisteri
grow up to five centimeters long and its body is about one millimeter wide. They have reddish
bodies, which are split into segments. Similar to earthworms, they have pointed ends. The body
wall of these worms is so thin that you can see through it to the animal’s organs. Although one
does not normally notice them, these aquatic worms are the most common animal in the
water. These aquatic worms crawl around on top of or inside the mud at the bottom. They eat
the mud and any small bits of plants or animal matter that they can find. This worm orients itself
head downward by building a small tube in the mud and letting its backside stick in the water.
Limnodrilus hoffmeistri are bioturbators, which means they can move the soil. As the worm eats
mud with its head down below, the dirt comes out the back end. This process of soil-moving is
important to keep the body of water healthy. Aquatic worms also break down the pollutants,
which settle to the bottom and poison the water. Limnodrilus hoffmeistriare often transported to
new places when the mud they are in stick to the feet of birds. These birds then travel to a new
lake or stream. This is why the Limnodrilus hoffmeistri are found worldwide.(FCPS)
The method that we used is called sub sampling. To prove that this is an accurate
measurement given our circumstances, we ran a short test on our first sample date. We gather a
sample of mud and massed the entire thing. After doing so, we gathered a small sample and
counted the number of organisms in it. By using a proportion of the mass sample/ mass total =
organisms sample/ organisms total, we were able to estimate how many organisms were present
in the entire sample. When we counted all of the organisms in the sample, we found that the
estimated and real values were very similar. This is the general idea behind the process
commonly known as sub sampling.
Materials and Methods
First, we will use a Lamotte stainless steel bottom sampling dredge to extract the mud
from the bottom of the Ala Wai Canal off the dock in Zone 4. After the dredge hits the bottom,
we will use a stick to shove the sampler deeper into the mud. That way we get a larger sample of
mud that extends below the surface of the mud. While sampling, we will note the depth in which
the mud was sampled using a string, which was separated into increments of meters. After we
collect the sample, we will pour the mud into a bucket. After collecting the sample of mud, we
are going to let the mud settle so that the water is separated from the essential mud. We will then
mass 50 grams of mud and dilute it with 350 mL of water.
Next, we will use petri dishes, a light microscope, pipets, probe tools, beakers, gloves,
and spoons to sample the mud. We will take a spoonful of mud and pour it into a petri
dish. Then we will examine each petri dish under a light microscope. When looking through the
mud using the probe tools, we will count and record the number of annelid worms within the 25
mL sample. After we find an annelid worm, we will extract it using a pipet and put them into
another petri dish. Later, we will take a picture of the annelid worm using a digital
microscope. We will do the same for any other organisms, specifically anthropods in the mud.
Immediately after we examine our mud sample, we will begin to search to find whether
there is a correlation between our weather data readings from the portal and the differing
numbers of organisms in the sample. The weather data incorporates and accounts for the rainfall
that has occurred during the past 7 days before the sample was taken.
By looking through the sample of mud and water, and counting the amount of annelid
worms and anthropods within the water, we will test whether there are any correlations between
the amount of rainfall and the types and amount of organisms present.
on that
17, 2011
11, 2012
Rained all
during the
week, low
25, 2012
March 31,
but no
rain night
Mud was
super rocky,
difficult to
obtain a good
mud sampled
Mud was
smooth and no
rocks or sand
Mud was
similar to
sample 2
Gut: 2
Gut: 21
Dead: 3
Mud was
grainy and
April 5,
Sunny, no
rain night
April 14,
Sunny, no
rain night
Weather Data:
Sample Dates of Rainfall
Dec. 10-Dec. 17
Feb. 4- Feb. 11
Feb. 18-Feb. 25
March 24- March 31
March 29-April 5
April 7-April 14
Total Rainfall
1.69 inches
2.16 inches
2.25 inches
2.23 inches
2.24 inches
2.23 inches
Pictures of organisms:
Annelid worm: Taken on February 11
Mud was
grainier than
usual and
contained a lot
of rocks
Mud was
grainy, sandy,
and rocky
Analysis of Data
We did a test on zone four from right off the dock to test the whether we could find
anything the Ala Wai mud as well as to test whether the methods of subsampling were efficient.
We sub-sampled a 50 gram sample to see if it was a sufficient method in retrospect to the entire
sample we took. From those results, we found annelid worms as well as anthropods through our
method of sampling using the lamotte dredge sampler. On that specific day of sampling it was
sunny, with no rainfall the day before of the day of.
In our latter samples from zone 4, we again found annelids and anthropods and wanted to
see whether there was any correlation between the amount of rainfall and the amount of
organisms in the mud. In sample 1, there was the least amount of rainfall during the week,
however it was the only sample in which there was rain the morning right before we took the
sample. In the first sample, we only found two annelid worms. Because it rained the morning
before, we assumed and concluded that all the organisms were on the surface of mud. Thus,
when it rained, the water from the Manoa and Palolo streams proceeded to wash away the
organisms on the surface; thus, there were no organisms in the mud. To prove that the organisms
were on the surface, we used a different method to sample mud. We took a hollow pipe and
dredged it into the bottom of zone 4 to obtain mud from a region below the surface. After
looking through that sample, we found no organisms. Hence, we concluded that the organisms
were only on the surface.
Following sample 1, our two samples in February were taken when the rainfall was heavy
during the week, however did not rain the night before or morning of. In sample two, we found
the most organisms compare to any other sample. The mud was smooth and contained less sand
and rocks compare to our latter sample which could have contributed to the amount of organisms
present within the mud. We found that the more granier the mud was, the harder it was to look
through. Sometimes, we needed to dilute the 50 gram sample of mud with more water in order
to be able to search through it efficiently. The grains and sand changed the habitat that the
organisms are used to being in, thus when the mud was grainy, we found little to no organisms.
In samples 3, 4, 5, 6, there was about equal rainfall over the course of the 7 days before
the sample was taken, yet the amount of organisms found did not match up. In samples 4 and 6,
we found absolutely no organisms in the fifty gram sample. If our hypothesis that the rain
washed down the organisms on the surface of the mud was correct, we should have found equal
amount of organisms in all the said samples. The discrepancy could have been due to human
error. Although we looked carefully through the sample, sometimes the human eye even with
the microscope could have easily missed these extremely tiny annelid worms and
anthropods. Also, sometimes the organisms in the mud were dead which make it even more
difficult to find because it is not moving in the water. Even though we tested to make sure that
sub sampling was a sufficient method of determining the entire amount of organisms in the
entire sample, the sub sampling method could have been improved to avoid error. By taking a
larger sample, we could have determined the amount of organisms present on a larger scale.
Finally, it was much more difficult to find anthropods in comparison to the annelid
worms. Many annelid worms as described in the background can survive in a greater range of
dissolved oxygen levels and live in more polluted environments. Thus, when it rains, the brown
water rushes down, and further pollutes the water. The annelid worms can handle the changes
in levels of pollution. Also, when it rains or when it doesn’t rain, the dissolved oxygen content
in the water changes. When the volume of water decreases due to lack of rain, the amount of
oxygen available for the same amount of organisms (that once had a greater volume of water),
is decreased. Thus, many organisms cannot adapt to the lower oxygen contents. Annelid
worms, however can survive and thrive even with little dissolved oxygen, thus they were easier
to find.
We found the most annelid worms in sample two. It was interesting because we found
different annelid worms in that specific sample. There were these other annelid worms with a
small gut compare to the normal worms with the large gut.
From our data, we could conclude that:
- The weather conditions on the day of and the day before our data sampling played a
major role in the data we found.
- Most of the organisms that we are attempting to study are located at the surface of the
river bottom. We could tell this because we found no organisms when we did a survey of the
inner layers of the mud.
- To better our data sampling methods, we need to depend on the weather conditions. We
need to go out and sample on days when there has been no precipitation around our school or in
the Manoa/Palolo Valley areas.
-There is no guarantee correlation between the amount of rainfall and the amount of
organisms in the mud.
-The annelid worms were easier to find in the mud samples because they can survive in
lower dissolved oxygen contents.
This investigation proved there wasn’t a definite correlation between the amount of rainfall and
the amount of organisms within the mud. We could possibly conclude that the amount of
organisms were affected by the immediate weather which is the weather that occurred the night
before or the morning before the sample was taken, not the long term weather over a certain
period of time. The question as to whether rainfall affects amount of organisms in the Ala Wai
mud can still be researched. We could take more samples and instead of sub-sampling such a
small amount of mud, sample a larger volume of mud. Also, we could look at other conditions
and their affects on the amount of organisms in the mud, such as salinity or dissolved oxygen
content. Thus, we could come up with a more definite conclusion to what really affects the
amount of organisms present.
Works Cited:
Barbour, Michael T and Jeroen Gerritsen. (1996). Subsampling of Benthic Samples: a Defense of
the Fixed-Count Method. Retrieved May 14, 2012 from the JSTOR Web Site:
Lewis, George W. (2010). Drought Conditions Which Affect Fish and Ponds. Retrieved May 14,
2012 from The University of Georgia Web Site:
Missouri Department of Natural Resources. (2008). Water Quality Parameters. Retrieved
December 28, 2011 from Missouri Department of Natural Resources Web Site:
Oram, Brian. (2002). Sources of Total Dissolved Solids. Retrieved December 28, 2011 from
Water Research Web Site: <>.
Partnership for Environmental Education and Rural Health. (2001). Water’s the Matter.
Retrieved December 28, 2011 from Partnership for Environmental Education and Rural
Health Web Site:
ScienceDirect. (1996). A Comparison of Some Methods Commonly Used for the Collection of
Sublittoral Sediments and Their Associated Fauna. Retrieved May 14, 2012 from
ScienceDirect Web Site:
United States Environmental Protection Agency. (2011). Climate Change- Health and
Environmental Effects. Retrieved May 14, 2012 from United States Environmental
Protection Agency Web Site:
United States Environmental Protection Agency. (2011).Water Quality Criteria. Retrieved May
14, 2012 from United States Environmental Protection Agency Web Site:
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