IJERD – International Journal of Environmental and Rural Development (2014) 5-1

Research article
erd

Verification of Drainage with Biotope Placed on Artificial
Floating Island Using Phragmites australis (Cav.) Trin. for
Water Purification
MASATO KIMURA*
Obihiro University of Agriculture and Veterinary Medicine, Hokkaido, Japan
Email: masa-k@obihiro.ac.jp

OSAMU TSUJI
Obihiro University of Agriculture and Veterinary Medicine, Hokkaido, JapanTOSHIMI MUNEOKA
Obihiro University of Agriculture and Veterinary Medicine, Hokkaido, JapanHIROTO OTE
Hokkaido Government, Hokkaido, JapanRYUICHIRO NAKAGAWA
Hokkaido Government, Hokkaido, JapanYURI YAMAZAKI
Obihiro University of Agriculture and Veterinary Medicine, Hokkaido, Japan
Received 27 October 2013

Accepted 1 March 2014(*Corresponding author)

Abstract Soil and fertilizer runoff from farms causes water pollution and eutrophication ofstreams and lakes. A method for cleaning the polluted water is the placement of artificial
floating islands of Phragmites on the water surface. Phragmites plants absorb nitrogendissolved in water, promoting lateral bud sprouting. The grown lateral buds are then cut,removing the pollutants. This purification method is suitable for cold regions such as
Hokkaido. We devised a drainage system with a biotope to apply this purification methodwith a minimum of effort. The advantage of the method is that because the artificial
floating islands of Phragmites after sprouting are placed in the drainage and streams, noPhragmites nursery is required. In this study, to determine the effectiveness of this method,
Phragmites plants after sprouting or in the 3rd year of growth were placed in a stream in
Biei Town, Hokkaido and were observed every 2 weeks. In the 3rd-year Phragmites plants,
terrestrial stems were lying on the ground after a month, but new lateral buds grew fromthe culms of fallen stems and underground stems. Thus, if Phragmites grown to a certain
stage could be used, this method is a promising approach to improve water quality. In
contrast, in Phragmites plants after sprouting, the number of terrestrial stems continued todecrease during the observation period because no underground stems were established byrunning water and accreted sand. The method should therefore be investigated in otherlocations, such as wide river channels and stable streams.
Keywords Phragmites australis (Cav.) Trin., water purification, drainage system with abiotope, stream

INTRODUCTION
Hokkaido is located in the northernmost part of Japan and covers the largest area in the country.
Land-extensive farming is practiced in this area. This area plays an important role as a food supply
area for Japan. However, because large amounts of fertilizer are applied to fields to increase yield,
soil and fertilizer run off into streams, lakes, and marshes after heavy rains. This runoff is the mostⒸ ISERD101

IJERD – International Journal of Environmental and Rural Development (2014) 5-1

important cause of water contamination and eutrophication. Given that pollutant loads from farm
fields have recently been increasing, it is desirable to investigate methods and strategies for
improving and maintaining the water quality of streams, lakes, and marshes.
One method to clean eutrophic water is to place the artificial floating islands of Phragmites
australis (Cav.) Trin. on the water surface (Uchida et al., 1999, 2001; Uchida and Maruyama,1998; Tazaki, 2002). This method comprises three steps. First, the artificial floating islands areplaced on the surface of a eutrophic water body, and lateral buds sprouting from nods ofPhragmites plants are inserted into a drain mat. Second, after the lateral buds have sprouted, theygrow and absorb large amounts of nitrogen, including nitrogen from the eutrophic water. Finally, inautumn, Phragmites plants that have accumulated nitrogen are cut and removed from the system.
The artificial floating islands are left in place during the winter and reused in the following year. To
investigate the suitability of this method in cold regions such as Hokkaido, Tsuji et al. (2009) andKimura et al. (2012) placed the artificial floating islands on a biotope developed adjacent to Lake
Mizusawa in Hokkaido and observed the growth of Phragmites. The result was that the plants grewsteadily and were not damaged by cold during the following winter. Thus, water quality in cold
regions could be improved by this method.
In this study, to assess a drainage system with a biotope using the artificial floating islands ofPhragmites, we placed two Phragmites at different growth stages in a stream flowing into LakeMizusawa, Hokkaido and observed their growth. The two kinds of Phragmites are following: one isthe Phragmites in the 1st year after sprouting, another is the Phragmites in the 3rd year which therhizome fully grew in the site for breeding of Phragmites. If the 1st-year Phragmites grew
successfully, water quality improvement employing the drainage system with a biotope using theartificial floating islands of Phragmites would be more efficient, given that a Phragmites nursery
would not be required.
METHODOLOGY
Study Areastudy area
Biei-cho

Biei-chosmall stream

Mizusawa Lakewater catchmentarea

Fig. 1 Study area: Mizusawa Lake in Biei-cho, Hokkaido
The study area was in one of the three streams flowing into Lake Mizusawa (Fig. 1), a manmade
lake at latitude 43 ° 32 ′ 14 ″N and longitude 142 ° 29 ′ 41 ″ E located in Biei-cho in central
Hokkaido. The terrain around these streams and lake is hilly and comprises mostly farm fields(293.8 × 10−2 km2) for wheat, corn and so on. During the growing season, large amounts offertilizer are applied to the fields to increase yield. According to Ote et al. (2011), the amount of
nitrogen applied to these hillside farms was 1.8 × 103 kg in 2010. However, following heavy rains,soil and fertilizer flowed into the streams and lake from the water catchment area. In 2010, the rateof nitrogen runoff from farms was 11% (Ote et al., 2011). Thus, the nitrogen loading of the threestreams and Lake Mizusawa was estimated to be 2.0 × 103 kg. This is the most important cause of
eutrophication of the streams and lake and leads to the occurrence of blue-green algae andⒸ ISERD102

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unpleasant smells. To preserve the local environment, it is desirable to improve water quality.
Growth of Phragmites
50cm

50cm

Five stems of Phragmites inserted
into a mat.

Fig. 2 Drain mat used to make artificial floating islands for water purification
As shown in Fig. 2, the artificial floating island of Phragmites comprises a drain mat(Yoshiharakakou Co., Ltd.) and five stems of Phragmites. First, the mats are placed on the water
surface until sprouting from the stems occurs. The mats are then transferred to the nursery and left
there until the rhizome grows to maturity.

Fig. 3 Aerial parts and rhizomes of 1st-year Phragmites

Fig. 4 Aerial parts and rhizomes of 3rd-year Phragmites
Figures 3 and 4 show the artificial floating islands of 1st- and 3rd-year Phragmites,
respectively. The 1st-year Phragmites was placed on the water surface of Lake Mizusawa on July 5,2012 and then sprouted. The 3rd-year Phragmites was transferred to the nursery on September 25,
2010. These Phragmites overwintered and the rhizomes grew as shown in Fig. 3.
These two types of the artificial floating island of Phragmites were transferred to the stream
shown in Fig. 1 on August 24, 2012. Figure 5 shows the arrangement of the artificial floatingⒸ ISERD103

IJERD – International Journal of Environmental and Rural Development (2014) 5-1islands of Phragmites. As shown in this figure, the artificial floating islands of 1st- and 3rd-year
Phragmites were placed alternately in the stream at 1-m intervals from upstream to downstream.
Moreover, each one was placed on the stream at 0.3 m intervals from water route and sandbank.
All the artificial floating islands of Phragmites were rooted to the bottom of the stream by anchor
pins. The number of stems was recorded every 2 weeks.
ground plan
Aright bank

BCleft bank

1m
GH

I

1st-yearPhragmites

0.3 m
DEFJK

L

3rd-year Phragmites

sectional plan

Fig. 5 Arrangement of artificial floating islands of 1st- and 3rd-year Phragmites in a stream
RESULTS
Figures 6 and 7 show changes in the number of stems of 3rd- and 1st-year Phragmites, respectively.
Each line in the two plots represents the total number of stems of the artificial floating islands ofPhragmites that lay in the same column, namely “A” and “D,” “B” and “E,” “G” and “J,” or “H”
and “K.” However, because the artificial floating island of Phragmites, “F” and “L” were flown to
downstream, the line, “C” or “I” represents the number of stem of the artificial floating island of
Phragmites, respectively.
As shown in Fig. 8, in most 3rd-year Phragmites, the aerial part fell over and was partly
covered with sand on September 5, 2012. However, the number of stems increased steadily in allpositions, especially from September 5 to September 28, as shown in Fig. 6. The number of stems
in “A” and “D,” “B” and “E,” and “C” was 104, 105, and 64, respectively, on September 28. The
reason for the increase in the number of stems was the extension of lateral buds from stems that fellover and the appearance of sprouts from the rhizomes, as shown in Fig. 8. After September 28,
because the air temperature dropped, the increase in the number of stems ceased.

8/24

9/5

9/28

8/24

10/20Fig. 6 Change in the number of stems of
3rd-year Phragmites placed in astream

9/5

9/28

10/20

Fig. 7 Change in the number of stems of
1st-year Phragmites placed in thestreamⒸ ISERD

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In contrast, as shown in Fig. 7, the number of stems of 1st-year Phragmites continued todecrease in all positions. Two months after placing in the stream, the number of stems decreased to
10 in “G” and “J,” 10 in “H” and “K,” and 17 in “I” because of the deposition of sand onPhragmites.

Fig. 8 Growth of Phragmites in the 1st year, September 28, 2012DISCUSSION
Growth of 1st- and 3rd-year Phragmites showed opposite behavior. The number of stems of 3rdyear Phragmites increased steadily (Fig. 6), whereas those of 1st-year Phragmites decreased (Fig.
7). We speculate that this difference was associated with rooting of the rhizome.
The aerial parts of 3rd-year Phragmites fell over in 2 weeks after placement in the stream, andsediment deposits were observed. However, because the rhizomes had matured in the nursery (Fig.
4), they rooted readily in the stream bed after transplanting. Therefore, the lateral buds and sprouts
could be stretched and appeared because of capable of absorbing nourishment from the rhizome(Fig. 8).This result suggests that if artificial floating islands of 3rd-year Phragmites are used, thedrainage system with a biotope can be used practically. However, because in this case a breeding
nursery of Phragmites will be required, land must be reclaimed.
As shown in Fig. 3, rhizomes did not grow to maturity. We infer accordingly that they could
not root in the stream bottom. In addition, sediment deposition was observed. From this result, weinfer that Phragmites does not readily grow in streams with irregular flow such as the stream
studied here. However, given an environment in which the rhizome can grow to maturity, wesuggest that 1st-year Phragmites can grow steadily in a stream. In future, for practical applicationof a drainage system with a biotope, we plan to determine the locations to which 1st-year
Phragmites can adapt and observe Phragmites growth again.
CONCLUSION
The drainage system with a biotope using the artificial floating islands of Phragmites wassuggested to improve the water quality of Lake Mizusawa, Biei-cho, which has been madeeutrophic by an influx of soil and fertilizer from surrounding farm fields. To investigate thepracticality of this method, 1st- and 3rd-year Phragmites were placed in a stream flowing into Lake
Mizusawa and their growth was recorded at 2-week intervals. The 3rd-year Phragmites grewsteadily because nutrients could be absorbed via rhizomes rooted in the stream bed. Thus, if theartificial floating islands of 3rd-year Phragmites are used, a drainage system with a biotope can beused practically. In contrast, the number of stems of 1st-year Phragmites decreased because theirrhizomes did not mature and nutrients required for growth could not be absorbed. However, in anenvironment where rhizomes can mature, we suggest that 1st-year Phragmites may also be used ina drainage system with a biotope. It is necessary to investigate the growth of 1st-year Phragmites
transplanted to floating islands.
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REFERENCES
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Uchida, T., Andoh, Y. and Maruyama, J. 1999. Studies on the efficiency of shoot production using lateralbud of culm and rhizome of common reed (Phragmites australis (Cav.) Trin.). J. Jpn. Soc. Reveget. Tech.,25, 13-24.
Uchida, T., Tazaki, F. and Maruyama, J. 2001. A new method on waterfront revegetation using Phragmites
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