![Study area map: Colombo -Sri Jayewardenepura canal system 2.2. Data Collection Biological sampling and habitat assessments were made in ten sampling sites on monthly basis during the period of November 2008 to June 2009. After developing the index a new set of samples was obtained for validation test during the period of May to June 2011. It was included with 3 new sites. Macroinvertebrates were sampled using a D-framed kick net with a 400 µm mesh bag. It was dragged along both river banks within a known distance (10 meters). Collected macroinvertebrate samples were sorted and identified at least up to family level by using naked eye, a hand lens or microscope and according to both locally and internationally reputed keys and guides such as Mendis and Fernando (1962), Fernando, (1963, 1964, and 1969), The Waterwatch Australia Steering Committee (2004) and Bartlett (2009), then enumerated and computerized. Some of the physical and-chemical parameters like Temperature, pH value, Conductivity and Total Dissolved Solids (TDS) of the water were measured at the field using potable measuring instrument [Electrical Conductivity Metre (340-set1, WTW Co., Weilheim, Germany)]. For further water quality analysis, additional water samples were collected and brought into the laboratory. Then, other physical and chemical parameters were analyzed in the laboratory as mentioned below; dissolved oxygen (DO): Winkler Method, Biochemical Oxygen Demand (BOD): standard5-day BOD testing method, Alkalinity and Cl -concentration: Titrimetric.](https://www.researchgate.net/profile/L-G-Ruwini-Perera/publication/325292044/figure/fig1/AS:11431281125658440@1678385345315/Study-area-map-Colombo-Sri-Jayewardenepura-canal-system-22-Data-Collection-Biological_Q320.jpg)
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Perera et al., /Journal of Tropical Forestry and Environment Vol. 2, No. 01 (2012) 10-19
10
Development of a Macroinvertebrate–based Index of Biotic Integrity
(MIBI) for Colombo-Sri Jayewardenepura Canal System
L. G. R. Y. Perera
1
*, J. Wattavidanage
1
, and N. Nilakarawasam
1
1
Department of Zoology, Open University of Sri Lanka, Nawala, Nugegoda, Sri Lanka
Date Received: 10-06-2011 Date Accepted: 22-02-2012
Abstract
Macroinvertebrates have been identified as excellent indicators of stream/ wetland health as they
respond rapidly to environmental changes and provide short to medium term pollution history records.
Current study was aimed to develop a Macroinvertebrate-based Index of Biotic Integrity (M-IBI) which
is a new approach to monitor stream/wetland health of Colombo-Sri Jayewardenepura canal system.
Sixty eight macroinvertebrate samples were obtained using a D-framed kick net from ten stations
namely Kotte, Nawala, OUSL, Kirimandala Mw., Wellawatta, Orugodawatta, St. Sebastian, Beira Lake,
Buthgamuwa and Royal Park representing main branches of the system and marshes covering dissimilar
environmental conditions of the canal system during the period of Nov. 2008 to June 2009 on monthly
basis. Habitat characteristics and some water quality parameters also recorded. For the index
development, those ten stations were grouped into two as ’Reference’ and ‘Degraded’ based on their
environmental conditions. Then ten candidate metrics were selected out of 41 for M-IBI development
after evaluating their sensitivity and appropriateness. Validity of the index was tested with a new
independent data set. Scores acquired were positively correlated with DO values (r = 0.578). That
concluded the potential of using M-IBI developed for biological monitoring and improving biotic
integrity of streams/ wetlands.
Keywords:
Macroinvertebrates, stream health, biotic integrity, Multimetric index, Colombo-Sri
Jayewardenepura canal system
1. Introduction
The canal system which is in and around Colombo-Sri Jayewardenepura area is currently in such
an environmentally deteriorated condition due to rapid development and urbanization of the area. The
quality of water and habitat in most of the areas are influenced by industrial and public effluent
discharge to the canal system. According to the Beira Lake Restoration Study (1993) cited by Fernando
(1994), the data collected by the Central Environmental Authority during a period of 23 months (from
March 1991 to February 1993) has shown that St. Sebastian canal, which is a branch of the Colombo
canal system, had recorded high turbidity, BOD and COD values, richer in nutrients; reduction of nitrate
into nitrite and ammonia (due to eutrophication), high concentrations of metals and faecal coliform.
*
Correspondence: ousl.ruvini@gmail.com
Tel-++ 94 77236 8009
ISSN 2235-9370 Print / ISSN 2235-9362 Online ©2012 University of Sri Jayewardenepura
Perera et al., /Journal of Tropical Forestry and Environment Vol. 2, No. 01 (2012) 10-19
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These records have already shown an unhealthy condition of the canal system for living beings. Also it
has been severely affected on well being of the community live around the canal system. Aquatic
macroinvertebrates are organisms that are large enough to be seen with the naked eye, lack of a
backbone and inhibit all types of waters including lentic, lotic and muddy habitats (Viklund, 2011).
They are capable of indicating any change in the environment through their responses at different levels
of organization, ranging from the individual animal to the total invertebrate community (Hodkinson and
Jackson, 2005). Since they live in the water for all or most of their life cycle, are exposed directly to the
stress of pollution and the prevailing conditions of the aquatic environment, are easy to collect, differ in
their tolerance to amount and types of pollution, are easy to identify, often live for more than one year
thus well suited to long-term observation of stresses. Their high species diversity which means many
potentially different reactions to many different environmental effects can be used as bioindicators for
assessing and monitoring the state of health of aquatic environments (Invertebrates as indicators, 2008).
The biological integrity of a stream or an aquatic ecosystem means how well the habitat can support
biological communities, including algae, invertebrates, fish, aquatic mammals and birds. For a given
habitat, to have high biological integrity, it should be unimpaired or minimally disturbed by human or
other activities and must contain a diverse assemblage of naturally occurring plants and animals (Jensen,
2007).
Multimetric indices are commonly used for evaluating the biological condition of water bodies.
Most multimetric indices consist of a number of measures or metrics (attributes), describing a specific
assemblage like fish or macroinvertebrates, which are combined into a single ‘multimetric’ value
representing the condition of a water body (Blocksom, 2003). These metrics can represent a wide range
of ecological characteristics, including taxa richness, taxonomic composition, pollution tolerance,
functional feeding groups, and behavioural habits. The Indices of Biotic/Biological Integrity (IBI) are
one form of Multimetric index that focuses on Fish, Periphyton, or Benthic communities. These IBIs are
region-specific due to the variations in communities across a wide range of ecological habitats.
Therefore it is only applicable only for regions that show same environmental conditions (Wittman and
Mundahl, 2002).
This study was aimed to develop a macroinvertebrate-based multimetric index of biological
integrity as an alternative for other conventional methods like chemical and instrumental which are
much expensive and need advance laboratory facilities.
2. Methodology
2.1. Study Area
Colombo-Sri Jayewardenepura (Diyawanna Oya) canal net work is a man made canal system
which is located on the left bank of the lower valley of Kelani Ganga. It is situated in the Western
province, Colombo district of Sri Lanka, latitudes 6 52’ 55” - 6 55’ 45” N and longitudes 79 52’ 35” - 79
55’ 15” E. Main catchment areas of the canal system are the low-lying marshlands known as
Kolonnawa, Heen Ela and Kotte marsh (Figure 1). These are also important as major flood detention
zones in the city of Colombo (Colombo Flood Detention Areas, 1995). Total area of the marsh is around
400ha. The canal system has 3 outfalls to the sea namely Mutwal (underground tunnel system),
Wellawatta and Dehiwala (last two are open drains). The average depth of these canals is about 1.5
meters. It may vary seasonally due to heavy sedimentation of silts and bank erosion in the rainy season
and it was frequently clogged with floating weeds & dumps (polythene, plastics & domestic wastes). It
has been found that 43.5% of the families in the study area dump their household garbage into the marsh
(Colombo Flood Detention Areas, 1995). Present study was carried out covering an extensive area of the
canal network. Ten sites were selected considering human factors (such as density of settlements,
Perera et al., /Journal of Tropical Forestry and Environment Vol. 2, No. 01 (2012) 10-19
12
industries, etc.), habitat characteristics (such as availability of marshlands and riparian vegetation) and
representing significant canals and streams.
Figure 1: Study area map: Colombo - Sri Jayewardenepura canal system
2.2. Data Collection
Biological sampling and habitat assessments were made in ten sampling sites on monthly basis
during the period of November 2008 to June 2009. After developing the index a new set of samples was
obtained for validation test during the period of May to June 2011. It was included with 3 new sites.
Macroinvertebrates were sampled using a D-framed kick net with a 400 µm mesh bag. It was dragged
along both river banks within a known distance (10 meters). Collected macroinvertebrate samples were
sorted and identified at least up to family level by using naked eye, a hand lens or microscope and
according to both locally and internationally reputed
keys and guides such as Mendis and Fernando
(1962), Fernando, (1963, 1964, and 1969), The Waterwatch Australia Steering Committee (2004) and
Bartlett (2009), then enumerated and computerized. Some of the physical and-chemical parameters like
Temperature, pH value, Conductivity and Total Dissolved Solids (TDS) of the water were measured at
the field using potable measuring instrument [Electrical Conductivity Metre (340-set1, WTW Co.,
Weilheim, Germany)]. For further water quality analysis, additional water samples were collected and
brought into the laboratory. Then, other physical and chemical parameters were analyzed in the
laboratory as mentioned below; dissolved oxygen (DO): Winkler Method, Biochemical Oxygen Demand
(BOD): standard5-day BOD testing method, Alkalinity and Cl
-
concentration: Titrimetric.
2.3. Data Analysis
Following steps were used to analyse data collected to develop the Macroinvertebrate-based
Index of Biotic Integrity (M-IBI).
Step 1. Identification of Reference and Degraded sites (sampling stations): Reference and Degraded sites
were identified and designated based on selection criteria (Table 1) that comprise both laboratory and
field survey records (DO value, BOD value, urban land and Forested land use practices of the area).
1
4
2
6
3
5
7
8
10
9
v1 v2
v3
N
Marshlands
Paddy fields
Study area
Flow direction
Main canals
Sampling Sites:
1. Kotte
2. Nawala
3. OUSL
4. Kirimandala Mw.
5. Wellawatta
6. Orugodawatta
7. St. Sebastian
8. Beira Lake
9. Budhgamuwa
10. Royal Park
Extra sites used for
Validation:
V1. Torrington
V2. Kotte Lake
V3. Kotte Bridge
Map of Sri
Lanka
Perera et al., /Journal of Tropical Forestry and Environment Vol. 2, No. 01 (2012) 10-19
13
Table 1: Criteria used for designating reference and degraded sampling sites
Reference site Degraded site Reference
DO value >= 2.5
Urban land use <= 50%
Forested/Marshy land use > 25%
BOD value < 5mg/L
DO value < 2.5
Urban land use > 50%
Forested/ Marshy land use < 25%
BOD value >= 5mg/L
(Stribling et al., 1998)
(Stribling et al., 1998)
(Stribling et al., 1998)
(Chauhan et al., 2011)
Step 2. Compiling and calculating candidate metrics: Candidate metrics for testing and potential
inclusion in the M-IBI were nominated primarily by assessing the previous work done, parallel studies
or documents/ protocols/ guidelines published by varies authors or institutes such as Stribling (1998),
Chirhart (2003), Macroinvertebrates as bio-indicators (2008), Jensen (2007), Calculating and
Interpreting the Genus-Level B-IBI (2001), Bennett and Rysavy (2003), Wittman and Mundahl (2002),
Weigel et al. (2002), Mandaville (2002) and Karr et al. (2002). These Macroinvertebrate based 41
candidate metrics were grouped in to five and listed out with their possible response to environmental
stresses (stream impairment) in Table 2.
Table 2: Candidate metrics and their predicted response to increasing stressors
Candidate Metric Predicted response
1. Taxonomic Richness
(i). Overall Species Richness Decrease
(ii). Tot no of individuals of the sample (Average ) Decrease
(iii). Tot EPT
(Ephemeroptera+Plecoptera+Tricoptera) Decrease
(iv). No of Diptera Taxa Decrease
(v). No of Molluscs Taxa Decrease
(vi). No of Odonata Taxa Decrease
(vii). No of Hemiptera Taxa Decrease
(viii). No of Coleoptera Taxa Decrease
(ix). No of Annelida/Policheata Taxa Decrease
(x). No of Crustacea Taxa Decrease
(xi). No of Chironomidae Taxa Decrease
2. Taxonomic composition & Abundance
(xii). % of Diptera Increase
(xiii). % of EPT Decrease
(xiv). % of Molluscs Decrease
(xv). % of Odonata Decrease
(xvi). % of Hemiptera Decrease
(xvii). % of Coleoptera Decrease
(xviii). % of Annelid/ Polycheats Decrease
(xix). % of Crustacen Decrease
(xx). % of Chironomids Increase
(xxi). Most abundant species and % Decrease
Table 2 continues …
Perera et al., /Journal of Tropical Forestry and Environment Vol. 2, No. 01 (2012) 10-19
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3. Pollution Tolerance / Intolerance
(xxii) Hilsenhoff family biotic index (FBI) Increase
(xxiii) No of Intolerant Taxa Decrease
(xxiv) No of Intolerant Individuals Decrease
(xxv) % Intolerant Ind of the sample Decrease
(xxvi) No of Tolerant Taxa Increase
(xxvii) No of Tolerant Individuals Increase
(xxviii) % Tolerant Ind of the sample Increase
4. Trophic Structure (Functional Feeding Groups)
(xxix) No of Predator Taxa Decrease
(xxx) No of Collector - Gatherer Taxa Variable
(xxxi) No of Collector - Filter Taxa Variable
(xxxii) No of Scraper Taxa Decrease
(xxxiii) No of Shredder Taxa Decrease
(xxxiv) % Predator Individuals Decrease
(xxxv) % Collector - Gatherer Individuals Decrease
(xxxvi) % Collector - Filter Individuals Decrease
(xxxvii) % Scraper Individuals Decrease
(xxxviii) % Shredder Individuals Decrease
5. Incorporated Diversity
(xxxix) Shannon-Wiener diversity index (H) Decrease
(xxxl) Simpson's Diversity Index (1-D) Decrease
6. Proportional Metrics
(xxxli) Heterogeneity Decrease
Step 3. Selecting Candidate Metrics: The criterion used for the selection of Candidate Metrics was based
on;
1. Their sensitivity to stream impairment/ human influences: Each candidate metrics was tested to
determine its correlation with environmental parameters such as DO, Cl
-
, TDS and Conductivity by
using Pearson’s Product-Moment Correlation method. Metrics showed significant correlation (r >= 0.5
/ -0.5) with those environment parameters were considered further.
2. Their ability to distinguish between Reference and Degraded sites: The distributions of metric values
of Reference and Degraded sites were compared using a non parametric statistical test (t test). Metrics
whose values differed between reference and degraded sites (p < 0.05) were retained for further
analysis, whereas those metrics having similar medians and distributions in reference and degraded
sites were eliminated.
3. Their contribution of non-redundant information to the M-IBI: Many metrics are sensitive to the
same change in conditions of stream habitat. These metrics that are highly correlated with one another
do not contribute much new information to the M-IBI score (Stribling, 1998). Hence the redundancies
among these metrics were calculated using Pearson’s product-movement correlation method.
Redundant metrics (r >= 0.75) were used in index combinations only if inclusion increased the index
classification efficiency.
Perera et al., /Journal of Tropical Forestry and Environment Vol. 2, No. 01 (2012) 10-19
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Step 4. Index development and scoring: Finalized metrics for the index development were further taken
into consideration and the calculated metric values were converted to metric scores. Quartile statistics
for each of the final metrics were calculated for both reference and degraded data sets. Metric values that
are equal or above 25
th
percentile of reference sites were scored as 5 while metric values equal or lower
than 25th percentile of degraded sites were scored as 0 and those were in between these two boundaries
were scored as 3. To obtain the final M-IBI for a given site, scores obtained for all metrics simply added
together. Metrics those expectations were reversed were scored conversely. Finally the qualitative
ratings and the stream condition that describe the status of the canal assessed were developed for five
rating categories as excellent, good, fair, poor and very poor by dividing the total index score into five
equal classes.
Step 5. M-IBI testing and validation: Once the M-IBI was developed it was tested using a new
independent data set of macroinvertebrates collected from ten sites of Colombo-Sri Jayawardhanpura
Canal system during the period of April-May, 2011. Apart from seven sampling stations used for index
development there were three (3) new sampling sites namely, Torrington, Kotte Lake (near renovation
site) and Kotte Bridge (near Lion’s club). Also to test the validity and to check if any relationship
existed between the M-IBI and habitat parameters used in conventional monitoring, M-IBI scores were
plotted against habitat parameters (DO value) for all ten sites.
3. Results and Discussion
3.1. Habitat assessment and designation of sampling stations
Based on the criteria developed for designating reference and degraded sites; Kotte, Nawala,
OUSL, Buthgamuawa and Royal Park sites were declared as reference sites whereas the others were as
degraded sites. Evaluation criteria and the scores obtained for sites are given in Table 3.
Table 3: Evaluation and designation of sampling stations base on their DO, BOD values, urban land use
and Forested land use practices of the surrounding area
Sampling Station
DO
value >
2.5
BOD
value <
5mg/L
Urban
Land Use
< 50%
Forested
Land Use
> 25%
Total
Score
Category
(Reference>=3/
Degraded <3)
Kotte 1 1 1 1 4 Reference
Nawala 1 1 0 1 3 Reference
OUSL 1 1 0 1 3 Reference
Kirimandala MW 0 1 0 1 2 Degraded
Wellawatta 0 1 0 0 1 Degraded
Orugodawatta 0 1 0 0 1 Degraded
St. Sebastian 0 1 0 0 1 Degraded
Beira Lake 0 0 0 0 0 Degraded
Buthgamuwa 1 1 1 1 4 Reference
Royal Park 1 1 1 1 4 Reference
3.2. Metric selection and evaluation
Results for the first step of metrics evaluation was obtained by finding the correlation between
41 candidate metrics and DO, Cl-, TDS and Conductivity values, also between reference and degraded
sites. Thirty one candidate metrics resulted Pearson’s correlation coefficient value as (r) >=0.50 or -0.50
and got the conclusion as ‘Positive’. As for the second step, again a t- test was done for all candidate
metrics and out of them 11 metrics resulted as ‘Positive’. Collectively, fifteen candidate metrics
representing five main categories (ecological characteristics) were qualified for the next step which was
Perera et al., /Journal of Tropical Forestry and Environment Vol. 2, No. 01 (2012) 10-19
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for the redundancy. After considering the redundancy test results, ten metrics that had less occurrence of
obtaining redundancy value (r) >= 0.75 were considered for the index development. However candidate
metrics like; (i) overall species richness, (x) no of crustacean taxa, (xxx) Shannon-wiener index and
(xxxli) Heterogeneity were included to the final list as to increase the classification efficiency.
3.3. Index development and scoring
As the final outcome, ten (10) out of forty one (41) candidate metrics were designated for the M-
IBI development. Then their values were converted to unitless M-IBI scores as in Table 4.
Table 4: Scoring Criteria for the ten metrics used in Macroinvertebrates based Index of Biological
Integrity (M-IBI)
Finally, the status or the narrative ratings of the M-IBI and their score were classed into five
ranges (rating categories) as excellent, good, fair, poor and very poor as given in Table 05.
Table 5: M-IBI score ranges and corresponding narrative ratings
3.4. M-IBI testing and validation
M-IMI scores and stream conditions obtained from the validation test done with the independent
data set (ten sites) are shown in Table 06. The M-IBI scores ranged from 17 to 40 for the tested sites.
According to the test results, none of the sites were ranked as ‘Excellent’. Site named as Royal Park was
ranked as ‘Good’ while others were ‘Fair’ for 6 sites (Nawala, OUSL bridge, Kirimandala Mw.,
Torrington, Kotte Lake & Buthdamuwa), ‘Poor’ for the sites called Senanayake Ground (Kotte) and
Kotte bridge, and “Very Poor” for Wellawatta. These M-IBI scores were positively correlated (r =
0.578) with habitat parameter (DO values) recorded from same tested sites. Additional tests are needed
to be conducted with more sites for further improvements
.
Metrics
Predicted
response to
increasing
stressors
M-IBI Score
5 3 1
Overall Species Richness Decrease >14.67
14.67 - 6.67
<6.67
No of Hemiptera Taxa Decrease >1.75
1.75 - 0.00
<0.00
No of Coleoptera Taxa Decrease >2.67
2.67 - 0.00
<0.00
No of Crustacea Taxa Decrease >2.25
2.25 - 0.25
<0.25
% of Diptera Increase <2.33%
2.33 - 51.79%
>51.79%
% of Odonata Decrease >2.04%
2.04 - 0.52%
<0.52%
No of Intolerant Taxa Decrease >1.25
1.25 - 0.50
<0.50
No of Collector - Gatherer Taxa Decrease >5.50
5.50 - 2.67
<2.67
Shannon-Wiener diversity index (H) Decrease >1.95
1.95 - 1.59
<1.59
Heterogeneity Increase <67.44%
67.44 - 87.77%
> 87.77%
M-IBI Score Stream condition (Narrative rating)
50 – 46 Excellent
38 – 45 Good
28 – 37 Fair
18 – 27 Poor
10 – 17 Very Poor
Perera et al., /Journal of Tropical Forestry and Environment Vol. 2, No. 01 (2012) 10-19
17
Table 06: M-IBI scores and narrative rating (stream condition) of ten tested sites
Tag No Site location
Canal name
M-IBI score
Stream condition
(Narrative rating)
1 Senanayake lane
Kotte canal
20
Poor
2
Nawala Road
Kotte canal
30
Fair
3
Narahenpita Rd
- OUSL bridge
Kotte
canal 36
Fair
4 Kirimandala Mawatha
Heen ela (canal)
32
Fair
5
Near St Peter's College
Wellawatta canal
17
Very Poor
6 Heen Marsh
Torington canal
28
Fair
7 Wetland restoration site
Kotte lake
28
Fair
8 Kotte bridge - near Lion's club
Kotte canal
18
Poor
9 Buthgamuwa - Kolonnawa
Marsh
Kolonnawa canal
36
Fair
10 Heen Marsh - near Royal Park
Heen ela (canal)
40
Good
Figure 2: Overview of the stream condition from the scores obtained for ten sites tested
4. Conclusion
The M-IBI has shown the potential of using it for biomonitoring and improving biotic integrity
of streams/ wetlands. Excluding monitoring the health of a natural freshwater ecosystem, M-IBI can be
used for monitoring the progress of restored or constructed ecosystems particularly for a renovated
wetland like Diyawannawa Oya. It is ready to be introduced to any government authorities institutes,
neighbouring schools, universities, etc. who engaged in stream health monitoring.
Acknowledgements: Authors wish to express their sincere thanks to Asian Development Bank (ADB)
for providing financial aid, to Dean/Faculty of Natural Sciences, The Open University of Sri Lanka
(OUSL), to all academic and non-academic staff of the Department of Zoology, OUSL and also to the
admin staff and the field crew of Research & Development Division, SLLRDC for their immense
support given to make this effort a success.
Perera et al., /Journal of Tropical Forestry and Environment Vol. 2, No. 01 (2012) 10-19
18
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