An Investigation on the Effects of Akulikuli Sesuvium
portulacastrum on the Quality of Ala Wai Water (Hawaii, 2009.)
Kai Kane
Mr. Kay/Mrs. Shimamoto
May 22, 2012
Abstract:
Our experiment is designed to test the effect that Akulikuli plants, a native, hardy plant, have on
the Ala Wai water quality. Environmentalists and researchers are aiming to use such plants like
Akulikuli to clean up, or phytoremediate, the rancid waters of the Ala Wai. Already, Akulikuli
plants have been launched on rafts in hopes that their roots will remove harmful chemicals from
the water and restore a measure of cleanliness to the canal. We wanted to see the exact effects
that Akulikuli could have on water so in our experiment we set up five tubs. Three contained
Ala Wai water and the other two had fresh water from a hose. In one fresh water tub we put
three Akulikuli plants. One Ala Wai water tub had three Akulikuli plants and one had six
Akulikuli plants. The tubs that did not have Akulikuli plants were used as control. The tubs
were set in an area with sun for the plants but where it would not rain. Over a month and two
days we took four readings. The data we collected, which cannot be considered entirely accurate,
demonstrate that while Akulikuli would not change dissolved oxygen percentage or the total
amount of dissolved solids in the Ala Wai, Akulikuli would certainly decrease salinity, neutralize
pH, and increase dissolved nitrogen levels. Phytoremediation is a viable method of improving
water quality, but the limited effectiveness may not be worth the high cost necessary to clean the
Ala Wai.
Question:
Can the presence and growth of Akulikuli Sesuvium portulacastrum improve the quality
of contaminated Ala Wai water as measured in terms of dissolved oxygen, pH, nitrate levels, and
salinity when the system is monitored over an extended period of time? (Hawaii, 2009).
Introduction and Research:
Long ago, the Ala Wai was created to rid the swampy wetlands in Waikiki of the
mosquitos and make the land suitable for industrial and agricultural development; the early
settlers of Hawaii wished to make Waikiki adequate for growth by draining the natural swamps
giving rise to the canal. Displacing the natural waterway from the mountains to the ocean has
had drastic effects on the ecology and homeostasis of the Ala Wai. There has been a buildup of
sediment, phosphorous, nitrogen, heavy metals, and street water runoff that have contributed to
the muck and scum of the Ala Wai we know today. The Ala Wai has now become polluted and
is in dire need of phytoremediation to rejuvenate the waterway to homeostatic balance.
As settlers developed the land they often destroyed environmental niches in the
ecosystem disrupting the balance of nature, known as homeostasis. With creation of the Ala
Wai, immigrants devastated the means of plants to absorb nitrogen and phosphorous in the
natural waterway. This plethora of excess nutrients provided an oasis for algal blooms and
microorganisms. According to the Health Department, the average nitrogen concentrations in the
Ala Wai canal are six times the accepted state standards, and phosphorous levels are double the
acceptable levels (Vorsino, 2007). This phenomenon of excess nutrients and sediment
accumulation is known as eutrophication and can cause severe environmental effects: increased
phytoplankton biomass, decreased clarity, reduced levels of light at depth, and a significant
decrease in dissolved oxygen levels (Mack, 2012). This in turn can turn a body of water from a
recreational lake to a green muck wasteland. Such has happened to the Ala Wai in the past years
transforming a waterway where local kids would swim and play to a mucky wasteland with the
stench of decay that can be smelled by tourists in Waikiki.
In order to rejuvenate the Ala Wai to its former clean state, an indigenous Hawaiian plant
has been selected to take on the job. Akulikuli, more commonly known as sea purslane, is a
hardy and salt tolerant plant that acts to fill the ecological niche eliminated by the swamps,
which were drained many years ago (Hawaii, 2009). Now, through the Akulikuli’s process of
phytoremediation, environmental biologists hope to improve the water quality of the Ala Wai.
Phytoremediation is the use of vegetation to extract biological contaminants from the ground or
water. Phytoremediation can remove metals from water, and it is also very effective in
remediating soil and organic compounds (Florio, Rembijas). It is a cost-efficient method of
cleaning up pollution, estimated to range from sixty cents to six dollars for every 1000 gallons of
water, with a safer environmental impact because all extraction tools would be organic (NASC).
Some other benefits of Phytoremediation are that the selected sites are more aesthetically
pleasing and low maintenance after being set up. Phytoremediation is not an uncommon method
of treating polluted soil or water, but Akulikuli would be particularly welcome in Hawaii
because it is an indigenous plant. Projects have been underway since 2005 with help from a 500
thousand dollar grant. Morris Takushi, a director of Natural Systems, received permits from the
U.S. Coast Guard and U.S. Army Corps of Engineers to introduce the Akulikuli plant into the
Ala Wai. A total of forty to eighty 3,000 foot rafts were placed in the canal as "floating
phytoremediation platforms" according to project manager Chad Durkin of Natural Systems Inc.
in May 2005 (Nakaso, 2005).
There are downsides to phytoremediation, however. Efficiency is dependent upon the
survival and health of the active plants. There is a considerable amount of time involved in
setting up a phytoremediation system, more than other remediation technologies. Extracted
toxins can also become products in biological magnification if the plants are consumed, releasing
the pollutants directly into an organism (NASC). Phytoremediation is also not as effective for
sites with high contaminant concentrations and it is slower at improving water or soil quality
than conventional methods. Finally, Phytoremediation does not work through winter therefore it
is seasonally effective (Florio, Rembijas). However, this would not be a problem in the eversummer season of Hawaii.
By placing the Akulikuli in the Ala Wai on floating beds, the roots of the plant drop
down to depths of about three to five feet and are surrounded by fishnets to keep larger fish from
eating away the roots. The plants, roots, bacteria, including mycorrhizae, a symbiotic fungal
organism, and microorganisms create a floating ecosystem that acts to absorb nutrients including
nitrogen, in the form of nitrates, and phosphorous from the water. By using Akulikuli to fill the
niche and essentially choking out the algal blooms, the Ala Wai can be remediated back to its
natural state. This clean state would allow for safe fishing, canoe paddling, and other recreational
activities once abundant and enjoyed by Waikiki locals. David Penn, a water-quality coordinator
for the Department of Health, said, "We know the system does function to remove pollutants, but
we don't know what the overall capacity of the system would be on a large scale" (Vorsino,
2006). The dearth of interest and data on the effects of the Akulikuli plant on water-quality has
forced the project to shut down, leaving the problem to the next generation, as many problems in
our world have remained.
Since the early immigrants of Hawaii settled the swamps of Waikiki, they have
understood and appreciated the importance of the natural flow of water from the mountains to
the ocean. The avarice of developers of Waikiki neglected the ‘aina and its importance in the
native culture. Today, the Ala Wai remains a reminder of the neglect bestowed on our island and
way of life. The indigenous Hawaiian plant, Akulikuli has shown hopes in the lab to
phytoremediate the Ala Wai water. Clearly, the Ala Wai is in desperate need of
phytoremediation by Akulikuli, but this task will be left up to future generations with hopes seen
by Mr. Kay and the University of Hawaii.
A previous AP Biology group, Team Hyacinth, studied the effects of Akulikuli
specifically on the turbidity over a period of three days. Our investigation spanned one month
and identified any changes in the percentage of dissolved oxygen, pH, concentration of nitrates,
and salinity. An improvement in water quality was indicated by an increase in dissolved oxygen,
a neutral pH, increased nitrates, and a lowered salinity. In this environment, fish and plants
would receive better living conditions; therefore a combination of any of the above
improvements would constitute a successful phytoremediation process.
Materials and Methods:
In order to conduct this experiment, collect four styrofoam bins, metal wire mesh, wood,
tap water, buckets, Ala Wai water samples, YSI Sonde, scissors, paper, pencils, and computer.
1. Collect all available materials and begin by setting up the four styrofoam bins along with a
control bucket for tap water and label them as such: “1:Ala Wai Water w/o Akulikuli , 2:Tap
Water w/o Akulikuli, 3:Ala Wai Water and Akulikuli Plant 4:Tap Water and Akulikuli Plant, 5:
Ala Wai Water and 2xAkulikuli Plant.”
2. Water samples will be taken from the Ala Wai off the dock and taken back to the set up bins.
3. While some team members are getting water, cut circles for the potted Akulikuli plants. Three
circles need to be cut into the styrofoam for bins # 3 and 4. Six holes need to be cut for bin #5.
(One of our bins needed to be reinforced with wire mesh and wood so it would not break under
the weight of the plants.)
4. Fill each bin with the same volume of water; volumes vary due to bin size, so that the water
submerges the bottom of each pot, insuring that the Akulikuli roots can reach the water.
5. Take measurements of pH, nitrates, dissolved oxygen and salinity levels and record them on a
data table using the YSI Sonde.
Date:
Bin 1: Ala Wai w/o Akuli
Bin 2: Tap Water w/o Akuli
Bin 3: Ala Wai Akuli
Bin 4: Tap Water Akuli
Bin 5: Ala Wai 2xAkuli
Salinity (PPT)
Percent Dissolved Oxygen
(%)
pH
Nitrates (g/L)
5. Place three potted Akulikuli plants in bins 3 and 4 and place six potted Akulikuli plants in bin
#5.
6. Allow the plants and water to interact for an extended period of time, approximately one
month and take YSI Sonde measurements as often as desired to have enough data to analyze.
Taking Data:
1. Remove the lids of each of the bins so the YSI Sonde probe can be completely submerged.
2. Run the YSI Sonde for approximately 30 seconds, as it takes readings every 5 seconds. This
will insure a more accurate reading.
3. Mark the time and the order of bins on a piece of paper so data can be collected off the
computer after all readings are taken.
4. After taking all readings make sure to place all plants and lids into their respective bin.
Data:
--See attached documnet with project pictures-Discussion:
On December 7, 2011 the YSCI was not properly calibrated for all readings so data
collected on this day is most likely invalid. When initially obtaining the water, we may have
stirred up sediment that was not present in other water containers.
Akulikuli was effective in desalinating the Ala Wai water. In the 1x Akulikuli tubs,
salinity dropped by over 74.3%. Doubling the amount of Akulikuli yielded a drop in salinity of
over 90.3%. Increasing the amount of Akulikuli thus decreases the salt content of water. Such
evidence supports the argument that the Akulikuli is responsible for significantly desalinating the
Ala Wai water.
At the beginning of our investigation we found that both Ala Wai water and our tap water
were too basic for living organisms. In order for aquatic plants like Akulikuli to survive and
thrive in optimum conditions, the pH of the water should fall between 6.5 and 8.0. Any value
less than 6.5 would make the water too acidic for the Akulikuli and thus less hospitable, and any
value greater than 8.0 would saturate the Akulikuli with excess nutrients. Our results show that
in all of our tubs containing Akulikuli plants, the pH level in these tubs decreased. However, the
pH levels within these tubs moved into the optimum pH range. In the tub containing Akulikuli in
fresh water, the pH level of the water went down slightly from about 8.45 to about 7.95. This
represented a move from a pH level outside the optimum range to one within the optimum range.
In the tub containing Ala Wai water and x1 Akulikuli the pH level went down from 8.1 to 7.3. In
the tub containing Ala Wai water and x2 Akulikuli the pH level went down more significantly
from 8.1 to 7.1. This increased rate was expected since more Akulikuli should accelerate the
process of pH change; however we did not anticipate this change to proceed quicker than it did.
In both the tubs Ala Wai water and Akulikuli, the pH of the water was just out of the optimum
range, however, the decrease in pH that was observed in both tubs, brought the pH levels of these
tubs further within the optimum pH ranges. Both our Ala Wai control and our freshwater control
showed slight decreases in pH levels overtime when they should have generally exhibited no
change in pH, but. Overall, the pH changes/moves toward optimum pH levels that we observed
in all of our tubs containing Akulikuli plants are important in maximizing the effectiveness of the
Akulikuli in the phytoremediation process. This will help improve water quality especially in
polluted waters like the Ala Wai. Not only do plants like fairly neutral pHs, but marine fish also
prefer this range of pH. Since Akulikuli moves the pH of the water towards neutral, both fish
and aquatic plants will benefit from the lowering of pH.
Our data showed that the amount of nitrate (NO3) present in the water of all of the tubs
containing Akulikuli increased over time. This occurred because the mycorrhizae on the plants
were able to fix nitrogen at a rate that was greater than the rate at which the plants were using the
nitrogen. High nitrate rates are beneficial for the survival of plants like the Akulikuli and
consequently the function of these plants. This allows them to act more efficiently in improving
water quality. At the start Ala Wai water contained more nitrates than tap water. By the end of
the investigation, the fresh water that had contained Akulikuli plants had a higher nitrate level
than the Ala Wai control water. The Ala Wai water that had six Akulikuli plants almost tripled
the initial concentration of nitrates.
Akulikuli does not greatly affect the percent of dissolved oxygen within a
fluid. Although plants produce oxygen from their leaves, this oxygen does not go into the water,
it goes into the air. Since oxygen is not produced in the roots, almost no oxygen will be
dissolved into the water. Only submerged plants and photosynthesizing protists such as algae
will increase the amount of dissolved oxygen.
For future experiments, we would design a system with two large tanks 4' X 3' X3' which
would house the Akulikuli system. These tanks would be separate however one would act as a
holding tank for Ala Wai water and sediment as well as aquatic organisms like fish and crabs.
The other tank would have a floating hydroponic tray with the Akulikuli plants. They would
create a more stable micro-ecosystem. Both tanks would have bubblers at the bottom to stir up
the sediment and maintain high dissolved oxygen levels to support aquatic animal life. A pump
from the holding tank would move water to the Akulikuli tank and a bottom tube would connect
the two tanks together. This would stimulate a flow of water present in the Ala Wai ecosystem.
This set up would be more controlled and evaporation would be cut down in a lab environment.
The large amount of water would make it easier to take readings and simulate the effects in a
larger body of water more so than out styrofoam tubs.
Conclusion:

Proper calibration is needed for more accurate readings.

Our data regarding turbidity was inconclusive.

Dissolved nitrogen was increased due to nitrogen-fixing mycorrhizae.

Akulikuli actively decrease the salinity of brackish water.

Total dissolved solids were not removed by the Akulikuli.

Akulikuli actively neutralize pH of water.

More accurate research must be done on the effects of Akulikuli on water quality.

Our setup was good and accounted for many environmental factors by including a control
setup. However, no small setup could be expected to account for all environmental
factors, such as the large variety of organic life.

Further research may be done regarding whether Akulikuli would actively alter the pH of
a strongly basic or strongly acidic environment. Future experimentation must be
conducted on a larger scale in order to investigate the extent to which Akulikuli affects
water quality.
Works Cited:
Florio, Nathan and Rembijas, Hayes. “Phytoremediation of Soil and Organic
Compounds” Rensselaer Polytechnic Institute Jan 10, 2012. Accessed April 27,
2012. <http://www.rpi.edu/dept/chem-eng/Biotech-Environ/MISC/phytorem.html>.
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Accessed May 1,
2012. <http://the.honoluluadvertiser.com/article/2005/Apr/21/ln/ln01p.html.>
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1, 2012. <http://nativeplants.hawaii.edu/plant/view/Sesuvium_portulacastrum.>
Leone, Diana. "Green is clean for Ala Wai." Star Bulletin. May 8, 2005. Accessed May 1, 2012.
<http://archives.starbulletin.com/2005/05/08/news/index3.html.>
Mack, Jeremey. "Eutrophication." Lake Scientist. 2012. Accessed May 1,
2012. <http://www.lakescientist.com/learn-about-lakes/waterquality/eutrophication.html.>
Nakaso, Dan. "'Akulikuli cleansing of the Ala Wai under way." Honolulu Advertiser. May 8,
2005. Accessed May 1,
2012. <http://the.honoluluadvertiser.com/article/2005/May/08/ln/ln07p.html.>
Nottingham Arabidopsis Stock Centre. "What Is Phytoremediation?" European Arabidopsis
Stock Centre. Nottingham Arabidopsis Stock Centre. Sept 27, 2011. Accessed Jan
23,2012. <http://arabidopsis.info/students/dom/mainpage.html>.
Vorsino, Mary. "No funding for floating Waikiki canal plants." Honolulu Advertiser. Oct. 6,
2007. Accessed May 1, 2012.
<http://the.honoluluadvertiser.com/article/2007/Oct/06/ln/hawaii710060348.html.>