Restoration and Phytoremediation in Two Impaired Hawaiian Streams Using
Native Plants and Coir Fiber Logs.
Carolyn Unser
M.S. Thesis Proposal
Advisor: Dr. Greg Bruland
Department of Natural Resources and Environmental Management
Summer 2008
Abstract
Many of Hawai’i’s streams are currently on the State’s 303(d) list of impaired water
bodies for which nutrients, turbidity, and suspended solids exceed that of Environmental
Protection Agency (EPA) allowable loads. Waimānalo Watershed, a Category I watershed
within the Ko’olaupoko region of Oahu, is listed as a top priority watershed for restoration. In
response, reports such as the Total Maximum Daily Loads (TMDL) Estimated for Waimānalo
Stream and the Waimānalo Stream TMDL Implementation Plan were developed to document
current conditions and control methods. This M.S. Thesis will address issues raised in these
reports by applying one of their suggested best management practices (BMPs),
phytoremediation, in order to increase nutrient uptake by riparian plants and to enhance stream
structure and function. Due to the highly episodic flow periods common to this area, existing
demonstration projects have been challenged by the task of establishing and maintaining stream
bank vegetation. An innovative approach using native sedges planted in coconut coir logs and
installed along stream riparian zones will be studied in an experimental setting and then in a
large-scale field installation along sections of Waimānalo and Kahawai Streams. Similar
methods to establish riparian vegetation have been used on continental streams but their use has
not been documented on Hawaii's streams. Identification of appropriate species for remediation
and successful installation of pre-planted coir logs along stream banks will protect sedges from
high flows and accelerate root anchoring into stream-bank substrate as the logs degrade. The
main hypotheses to be tested are as follows: (1) native wetland/riparian plant species will be able
to successfully establish and survive in coconut coir media; (2a) individual species selected will
have significantly different levels of tissue nitrogen (N) content when exposed to varying levels
of N; (2b) within species, tissue N content will increase across the N addition treatments; (3) preplanted coir logs will have a higher degree of % cover than direct plantings; and (4) installation
of coir logs will decrease nutrients in stream waters as planted species will uptake nutrients.
Literature Review
Introduction
Waimānalo Watershed, located in the Ko’olaupoko District region of Eastern Oahu,
drains about a 16 km2 area into Waimānalo Bay and onto a reef with submerged margins (KBAC,
2002). Waimānalo Stream is the primary drainage for the basin valley and the watershed’s only
true perennial stream which stretches about 5.5 km in length. The stream is in the shape of the
letter “Y,” with the southeastern tributary identified as Kahawai Stream and the northwestern
tributary, named Waimānalo Stream. Unless otherwise noted, the term “Waimānalo Stream”
includes both Waimānalo and Kahawai tributaries (KBAC, 2002). Waimānalo translates to
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potable or sweet water in the native Hawaiian language (Pukui, 1986). Waimānalo Stream,
however, was described in a recent report issued by the Hawai’i State Department of Health
(DOH) as an impaired, highly-altered waterway that no longer functions as a natural stream,
since sediments and nutrients from the watershed enter the stream at a rate faster than they can
be assimilated and recycled (HDOE, 1998; Harrigan, 2001; KBAC, 2002).
Waimānalo Stream was listed as an impaired water body on Hawai’i’s 1998 Clean Water
Act 303(d) List (KBAC, 2002; HIDOH, 1998). In a standard response to the official priority
listing, a Total Maximum Daily Load (TMDL) assessment for Waimānalo Stream’s was
conducted. This assessment, prepared by the DOH, determined the maximum amount of
pollutants that can enter Waimānalo Stream without violating the State’s Water Quality
Standards, compiled in the Hawai’i Administrative Rules, Chapter 11-54 (Harrigan, 2001).
Following this assessment, a report for implementation recommendations was ordered. This
report described Waimānalo Stream’s many problems, including poor water quality, lack of
habitat, and altered flow regimes. Since placement on the EPA’s 303(d) list of impaired water
bodies of Hawai’i, residents and environmental interest groups have recognized the need for
restorative action and the need to address the point and nonpoint sources effecting health of
Waimānalo stream.
Many factors have contributed to the decline of this stream system. Urban development
and land-use changes over the last century have drastically altered this streams waterways and
landscapes resulting in a shift of natural system functions and processes (Laws, 2003; KBAC,
2002). The streams in the watershed are prone to flash floods and prolonged periods of low
flows (Tomlinson, 2003). Erosion of stream banks, including the toe area, is one of the major
contributors to sediment pollution problems in streams and near shore marine waters of Hawai’i.
Other contributors of stream pollution include surface runoff generated from anthropogenic
sources such as cess pools, leaching of agricultural and residential fertilizers, and animal waste.
These pollutants are then transported along the waterways where they are either deposited in or
along the streams or in receiving waters at the ocean. Land-based sources of pollutants, such as
sediment, nutrients, and other pollutants, are one of several factors threatening the quality of
coral reef ecosystems in Hawai`i (EPA, 2001 and 2004). Management of these identified stream
problems is important for sustaining Hawai’i’s terrestrial and aquatic habitats, as well as,
ensuring the future of healthy aquifers.
Past demonstration projects with this stream have employed bio-engineering techniques
for the protection of stream banks. This project will build upon past remediation efforts and
utilize principles from constructive wetlands for nutrient uptake. The use of coconut coir fiber
“logs” for toe protection will be expanded to include the development of pre-planted logs that
will decrease the time that the vulnerable area of banks are exposed to erosion during restoration
projects. Successful establishment of vegetation in the toe area can significantly decrease
sediment loads generated from these areas during storm flows (EPA, 2001). Riparian plantings
often act as a sink for nutrients from runoff waters because they can remove nutrients entering
streams through surface and subsurface soils (Sabater, 2000). Native plantings will replace alien
vegetation that decrease stream habitat and often clog channel ways (Laws, 2003). Although
pre-planted logs have been successfully used in the continental U.S., this technique has neither
been demonstrated with Hawaiian plants nor under the highly variable flow rates found in
Hawai’i.
Phytoremediation of nutrients in Waimānalo and Kahawai Streams takes advantage of the
natural metabolic processes in living plants to carry out a variety of chemical reactions that are
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energized by sunlight. Plants and associated microorganisms can absorb, transform, or degrade
pollutants, thus limiting their spread in the environment. To understand the role of these plants
in the treatment process, it is important to consider the role of phreatophytes1 in the landscape.
Phreatophytes are only one part of a complex system, so when comparing the effectiveness of a
system process, such as reducing organic N, performance considerations of the complete system
must be taken into account.
The process of utilizing plants for the cleanup and containment of nutrients contained in
the free flowing water of streams in Hawai’i warrants further research. There have been studies
focusing on the effectiveness of constructed wetlands or riparian zones in Hawai’i using native
plants. However, few studies have quantified individual species and their effectiveness in
remediating nutrients, metals, or other types of pollution. To date most “restoration” in Hawai’i
has simply involved removal of non-native, invasive vegetation. A review of the scant literature
regarding wetland restoration in Hawai’i has established that learning how to effectively restore
native plants to Hawai’i’s streams will require much more effort, scientific study and most
importantly, documentation of successes and failures encountered when attempting to restore
wetland vegetation (Brimacombe, 2002).
This project will conduct nutrient loading experiments with several native Hawaiian
sedge species planted on coir logs, document their ability to take up nutrients, grow out the most
effective plants in coir logs at a greenhouse, and conduct a large-scale field installation of these
pre-planted coir logs at the toe of the stream banks of Waimānalo & Kahawai streams. Field
data collection will document success of implementation and restoration of stream ecological
structure and function. Changes in water quality parameters (e.g. nutrient concentrations) and
plant survival through different installation methods, such as pre-planted coir logs or outplanting potted individuals will be monitored over the course of the thesis research.
Objectives and Hypothesis
Overall Objective: To identify candidate native sedge species for stream phytoremediation and
to demonstrate the use of pre-planted fiber logs for successful plant installation in two Hawaiian
streams.
Experimental Objectives and Hypotheses
Objective 1: Select and test native wetland/riparian plant species [Cyperus javanicus Houtt, Java
sedge (Ahu’awa), Cyperus laevigatus L., smooth flatsedge (Makaloa), Cladium mariscus ssp.
jamaicense Crantz Kukenth, sawgrass (‘Uki), and Cyperus polystachos. manyspike flatsedge
(Kiolohia) for their suitability for restoration at a demonstration site using a set of predetermined criteria.
Objective 2: Determine success of using coconut coir logs as a media for plant root
establishment prior to field installation.
1
Phreatophytes are plants whose roots are in direct contact with water in the aquifer or vadose
zone.
3
Alternative Hypothesis 1: Native wetland/riparian plant species will be able to
successfully establish and survive in coconut coir media.
Objective 3: Expose selected species to varying levels of N (in the form of ammonium nitrate in
surface water) and compare their tissue nutrient uptake.
Alternative Hypothesis 2a: The individual species selected will have significantly
different levels of tissue N content as biomass structure, physiological needs, and nutrient
tolerances differ among species.
Alternative Hypothesis 2b: Within species, tissue N content will increase across the N
addition treatments.
Field Establishment Objective and Hypotheses
Objective 4: Install and secure pre-planted coir logs along 92 meters (m) of each stream and
monitor plant species survival and compare species percent (%) cover and planting method
success.
Alternative Hypothesis 3: Pre-planted coir logs will have a higher degree of % cover than
direct plantings.
Objective 5: Monitor quarterly water quality samples from streams, including N (nitrate,
ammonium, and total dissolved N, phosphorous (P), before, during, and after coir log
installation.
Alternative Hypothesis 4: Installation of coir logs will decrease nutrients in stream
waters as planted species will uptake nutrients.
Methods
Plant selection
The selected plant species have been repeatedly mentioned in literature related to
constructed wetlands or have been used in erosion control projects in Hawai’i, and/or have been
recommended by experts in the field. Persons contacted about plant selection include the
following: Matthew Kanemoto (Kahuku High Agricultural Science Program Director), Pauline
Chinn (UH Mānoa Professor, Education and Curriculum Studies; Science Multicultural
Education, Indigenous Science Curriculum), Dennis Kim (Native Plant landscape Nursery
Owner), and Hui Ku Maoli Ola Nursery (Native Hawaiian Plant Specialists). Species have been
chosen which meet the project criteria:
1. Native status
2. Wetland indicator status.
3. Potential ability to establish roots within and grow on coconut fiber coir logs
4. Pollutant uptake
5. Stream hydraulic properties
6. Ease of maintenance.
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7. Remediative quality/attached microbial growth on root
8. Commercial/Local availability.
The species selected will need to thrive in the existing impaired environmental conditions
of Kahawai and Waimānalo Streams. Baseline samples will be collected and used to
characterize the in-situ site conditions that will need to be represented in the greenhouse study in
order to ensure success of field plantings.
Four species of native Hawaiian wetland plants will be exposed to different
concentrations of N though a cyclical hydroponic system established outdoors at the CTAHR
Mauka Campus experimental plots. The four species selected are: Cyperus polystachyos
(Kiolohia), Cyperus javanicus ('Ahu'awa), Cyperus laevigatus (Makaloa), Cladium jamaicense
('Uki).
Growbox Sampling Design
The plants will be planted in coconut fiber coir logs that will be placed into 6 mm plasticlined wooden grow-boxes with the dimensions 2.5 m x 1.2 m x .46 m. An irrigation reservoir
will be hydraulically connected to the grow boxes. The grow boxes will have a slightly positive
slope and at the low end a 227 Liter per hour aquarium pump will convey effluent water to a
catchment reservoir, which will return the water to the irrigation reservoir. Three grow boxes
will be used, each with four coir logs, measuring 2.13 m by approximately 20 cm diameter,
placed in each grow box. Plants will be positioned in a randomized complete block design to
minimize effects from position, distance, shading, or species interaction. Blocks can be defined
either by plant distance on each log from irrigation reservoir or by each log itself (Appendix 1).
A hydroponic fertilizer will be added to the irrigation reservoir as a baseline nutrient
solution for optimal plant growth. In addition to the baseline solution, ammonium nitrate will be
added to increase the aqueous nitrate in the second and third boxes by 4 mg/L and 8 mg/L,
respectively, above baseline additions to reflect a high and very high range for the stream.
Ammonium nitrate quantities for grow box additions were determined by comparing results from
the project’s September 2007 stream sampling and from data contained in publications of past
sampling analysis and recommendations regarding Waimānalo and Kahawai Stream sampling
(Harrigan, 2001; Laws, 2003). Physical and chemical properties, such as pH, temperature, etc.,
will be closely monitored to ensure no major differences.
Grow box water will be changed and both the baseline hydroponic fertilizer and the
ammonium nitrate additions re-administered every two weeks. Samples will be analyzed for
total dissolved nitrogen (TDN), nitrate+nitrite (NO3+NO2), total phosphorus (TP), and phosphate
(PO4-P). Quality Assurance/Quality Control water samples will be collected (1) 24 hours, and 2)
1 week following the addition of baseline and spike nutrients) on a minimum of two occasions;
these samples will also be sent to the Marine Science Analytical Lab (MSAL) at UH Hilo for
analysis. The 24 hour sample will be used to measure the efficacy of the estimated computation
of initial N and P concentration derived via mass volume calculations and the 1 week sample
used to estimate if nutrient uptake by plants is linear.
The final month of the experiment trial will consist of deconstructivly harvesting and
measuring the biomass of each species from within each nutrient treatment for estimates of the
aboveground biomass. Sampling of 2 or 3 plants per nutrient level will, decided at time of
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harvest, will allow for a replicated design of analysis. Plant biomass weights will be compared
within species for differences and between nutrient levels.
Field Sampling design
Selected plants were grown by a local native plant nursery, Hui Ku Maoli Ola in
Kaneohe, to plant in the coir logs (each 3.05 m log will be planted with 19 plants of a single
species). The planted coir logs will be housed at the nursery, irrigated via overhead sprinklers,
and fertilized as needed to facilitate plant growth. In addition to the 1140 plants that will be
planted in the coir logs, about 1060 plants (same species) will be planted on the stream bank, in
concert with biomulch matting, to fill in the area between the coir logs and the bank. Subsequent
to the coir log and additional plant installation, erosion matting will be installed along an area of
about 1.83 m of the bank along the installed 45.73 m of coir logs.
Stream water quality data will continue to be collected quarterly throughout the duration
of this project.
Laboratory Analysis
Tissue collection
Total nitrogen (TN) and total carbon (TC) values of the plant tissue will be obtained by
ball milling samples and using the traditional analysis at the University of Hawai’i Manoa
Agriculture Diagnostic Service Center (ADSC) Laboratory.
Water Samples
Grow box and stream samples will be collected in 500 mL acid washed bottles and sent
to MSAL to be analyzed for TDN, NO3-N, NH4-N, TP, and PO4-P.
Data Analysis
Growbox
Tissue biomass will be measured over time for N content. Sampling of four species in
the three treatment tanks will be conducted four times, once per month, with block species
combined. This includes a total of 64 samples per box and a combined total of 192 samples for
analysis.
Any differences in tissue N levels and biomass will be statistically tested to determine
effects from exposure to elevated N levels. A randomized complete block design over three
locations will be used for analysis purposes. The locations correlate to the three N levels and
will later be combined and tested as a split plot and tested for homogeneity of variances.
Analysis of the design will be arranged in an ANOVA as a repeated experiment at
different N treatments (or locations) with four varieties and four logs (blocks).
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ANOVA for one treatment (location)
Source DF
Total
63
Blocks=Logs OR Distance 3
Varieties
3
Block X Variety
9
Month
3
Month X Variety
9
Err b
37
Combined ANOVA for three treatments (locations)
Source DF
Total
191
Loc - Nitrogen
2
Error a = Block(Loc)
9
Variety
3
Variety X Location
6
Error b
27
Month
3
Month X Variety
9
Month X Location
6
Month X Variety X Location
18
Err c
108
Photo point monitoring will be utilized biweekly to record growth and color throughout
trial. YSI data will be recorded in order to ensure that water levels remain constant throughout
experiment and between grow boxes.
Field
Vegetation monitoring will determine if plants are providing efficient ground cover
therefore protection along the active channel and toe areas. Three types of vegetation monitoring
will be conducted, photo-point monitoring, log survival counts, and percent coverage.
Photo-point monitoring of vegetation will proceed monthly using a standard operating
procedure, as follows. Vegetation monitoring will involve taking a series of digital photographs
over time at designated sites. At each site, representative locations from upstream, across
stream, and downstream will be selected for photo point monitoring. This will involve a total of
3 photos being taken per site, 18 photos per stream. Each photo monitoring plot will be marked
with rebar and GPS units to assist in returning to the same point in future sampling events. The
locations of the stakes will also be marked on a site map for reference purposes. Two PVC pipes
will be placed 5 m apart in the direction the photo is to be taken. The first pipe will serve as the
camera post and the second pipe will serve as the sighter post (see figure below).
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Camera Post
Sighter Post
Upstream
Downstream
1m
5m
The plots will be taken from the middle of the stream looking up stream, across the
stream, and downstream. One photo will be taken at each plot per visit, for a total of 3 photos.
Plant survival rate will be measured by direct plant survival count on each log during the
installation phase and recorded again 6 months later. Percent coverage will be measured and
vegetation content will be monitored at each site at 6 months after installation. Vegetation
monitoring will consist of recording percent cover and species composition from 1 m2 plots
located in the middle of a randomly selected log for each species. Percent cover of the dominant
vegetative species in the plot will be estimated (see figure on the following page for cover
estimation). Other plants in plots will be identified to the species level whenever possible using
the Hawai’i Wetland Field Guide (Erickson and Puttock, 2006).
Coverage ANOVA:
Total
Bank (Block)
Stream
Species
Stream x Species
Error
15
1
1
3
3
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Stream water quality data will be analyzed from one year prior to field installation to one
year thereafter. The September 2007 data will provide a baseline measurement. In addition to
providing a baseline for nutrient concentrations to be used in the greenhouse experiment, this
information provides a baseline for future comparisons after the planted coir logs are installed.
Proposed Thesis Outline
Chapter 1: Introduction and Literature Review
Chapter 2: Methods
Chapter 3: Grow-box Experiment and N Uptake Across Species and Treatments
Chapter 4: Field Installation, Plant Establishment, and Monitoring
Chapter 5: Summary and Conclusions
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References:
Brimacombe, K. 2002. ANNUAL REPORT II: Applied Research on Use of Native Plants for
Coastal Wetland Restoration on O’ahu. Department of Botany, University of Hawai’i,
Mānoa.
Environmental Protection Agency (EPA). 2001. Waimānalo Stream TMDL Implementation
Plan. Environmental Planning Office. Hawaii Department of Health: 18.
Environmental Protection Agency (EPA). 2004. “Hawai`i’s Local Action Strategy to Address
Land-Based Pollution Threats to Coral Reefs.” Accessed on 27 June, 2008, from
http://www.hawai`i.gov/health/environmental/water/cleanwater/prc/pdf/LAS.CRLBP_fnl_3-22-04.pdf.
Environmental Protection Agency (EPA). 2005. Handbook for Developing Watershed Plans to
Restore and Protect Our Waters. Diane Publishing Co, Darby, PA.
Erickson, T. A. and C. F. Pottock. 2006. Hawai'i Wetland Field Guide: an ecological and
identification guide to wetlands and wetland plants in the Hawaiian Islands. Bess Press
Books, Honolulu, HI.
Harrigan, J. and S. Burr. 2001. Waimānalo Stream TMDL Implementation Plan. EPA and
Hawai’i Department of Health, Environmental Planning Office.
Kailua Bay Advisory Council (KBAC). 2002. Ko‘olaupoko Water Quality Action Plan.
L. Koch, D. Penn and H. Lao. 2007. State of Hawai’I Water Quality Monitoring and
Assessment Report: Integrated Report To The U.S. Environmental Protection Agency
and The U.S. Congress Pursuant To Sections §303(D) and §305(B), Clean Water Act
(P.L. 97-117).
Laws, E.A. and L. Ferentinos. 2003. Human impacts on fluxes of nutrients and sediment in
Waimānalo Stream, O'ahu, Hawaiian Islands. Pacific Science 57, 2:119-140.
Pukui, M.K. and S.H. Elbert. 1986. Hawaiian Dictionary. Revised and enlarged edition.
Honolulu: University of Hawai’i Press.
Sabater, F., A. Butturini, E. Marti, I. Munoz, A.Romani, J. Wray and S. Sabater. 2000. Effects
of Riparian Vegetation Removal on Nutrient Retention in a Mediterranean Stream.
Journal of the North American Benthological Society 19, 4:609-620.
Tomlinson, M.S. and De Carlo, E.H. 2003. The need for high-resolution time series data to
characterize Hawaiian streams. Journal of the American Water Resources Association
(JAWRA) 39:113-123.
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Appendix 1. Grow box experimental layout.
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