Comparison of the Performance of Four Biotic Indexes
Developed for Use on Puerto Rico Streams
Report prepared by:
Approved by:
Z/-^/ v 1
James Kurtenbach, Aquatic Biologist
Monitoring Operations Section
Johi^^^iwara, Chief ^
Monitoring and Assessment Branch
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TABLE OF CONTENTS
List of Figures ii
List of Tables iii
List of Acronyms iv
Executive Summary v
Introduction 1
Methods 1
Results 4
Discussion 6
Literature Cited 7
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LIST OF FIGURES
1. Map of stream sites sampled in the Rio Piedras, Puerto Rico 2
2. Map of stream sites in Puerto Rico 3
3. Comparison of biotic index scores corresponding to a water pollution gradient in the Rio
Piedras 4
4. Box and whisker plots of biotic index scores for reference and test stream sites 5
ii
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LIST OF TABLES
1. Spearman's correlation of four macroinvertebrate biotic indexes with selected measures
of human disturbance 5
iii
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LIST OF ACRONYMS
BMWP'PR Index Biological Monitoring Working Party
DOC dissolved organic carbon
EPA Environmental Protection Agency
GIS Geographic Information System
IBF'PR Index Biotic Family
Mil Macroinvertebrate Integrity Index
PMA Percent Model Affinity
PREQB Puerto Rico Environmental Quality Board
TOC total organic carbon
TSS total suspended solids
iv
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EXECUTIVE SUMMARY
Few examples of studies in the Caribbean exist in documented literature on the use of biotic
indexes to assess water quality of streams, and until very recently water quality practitioners
working in Puerto Rico lacked stream bioassessment protocols and indexes to directly assess and
report on biological conditions. The primary objective of this study was to evaluate four newly
developed indexes, Macroinvertebrate Integrity Index (Mil), Percent Model Affinity (PMA),
Index Biological Working Party (BMWP'PR), and Index Biotic Family (IBF'PR),
This report describes the results from testing the performance of four newly developed biological
indexes for water quality assessment of Puerto Rico streams.
Index scores were calculated using macroinvertebrate data collected from the Rio Piedras and
other stream sites located throughout the island, and performance of each index was tested to
determine differences in the responses along gradients related to land use, water chemistry, and
physical habitat.
BMWP'PR, Mil, PMA, and IBF'PR scores all showed strong responses to the pollution gradient
in the Rio Piedras and were strongly related to several potential stressors. BMWP'PR scores
increase in response to stress, while Mil, PMA, and IBF'PR scores decrease in response to
stress. Land use response of the BMWP'PR, Mil, PMA, and IBF'PR distinguish reference from
deforested stream sites with some degree of separation. Discriminatory power was greatest for
the BMWP'PR, Mil, and IBF'PR indexes with no overlap of the interquartile ranges, while the
PMA index had some overlap of the interquartile ranges.
Results of this study will be used to make recommendations to the Puerto Rico Environmental
Quality Board (PREQB) for their stream monitoring and assessment program. All four newly
developed indexes could have the potential to provide the PREQB with a suite of assessment
tools to implement biological criteria in their water quality program, more accurately determine
aquatic life use support, and prioritize streams for protection and restoration.
v
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Introduction
Bcnthic maeroinvertebrates have a long history of use as biological indicators of water quality.
In temperate regions of the world, bioassessment methods used to survey benthic
maeroinvertebrates have been developed and successfully implemented in biological monitoring
programs. However, few examples of studies in the Caribbean exist in documented literature on
the use of biotic indexes to assess water quality of streams, and until very recently water quality
practitioners working in Puerto Rico lacked stream bioassessment protocols and indexes to
directly assess and report on biological conditions (Kurtenbach 2011, Kurtenbach 2015,
Guiterrez-Fonseca et al. 2016). This has been attributed to the slow development of biological
assessment protocols applicable to the Caribbean and throughout the neotropics.
As a result of the development of these indexes there is a need to compare and determine the
performance of each index to assess environmental conditions. Each index may respond
differently to environmental gradients of degradation and may contribute different information to
a final assessment of water quality. Studies show a range of agreement when indexes are
compared for their similarity of water quality assessment results (Czemiawska-Kusza 2005, Gray
and Delaney 2007, Geng et al. 2012).
The primary objective of this study was to evaluate four newly developed biotic indexes
(Kurtenbach 2011, Kurtenbach 2015, Guiterrez-Fonseca et al. 2016), Macroinvertebrate Integrity
Index (Mil), Percent Model Affinity (PMA), Index Biological Monitoring Working Party
(BMWP'PR), and Index Biotic Family (IBF'PR). Index scores were calculated using
macroinvertebrate data collected from the Rio Piedras and other stream sites located throughout
the island, and performance of each index was tested to determine differences in the responses
along environmental gradients related to land use, water chemistry, and physical habitat.
Results of this study will be used to make recommendations to the Puerto Rico Environmental
Quality Board (PREQB) for their stream monitoring and assessment program. All four newly
developed indexes could have the potential to provide the PREQB with a suite of assessment
tools to implement biological criteria in their water quality program, more accurately determine
aquatic life use support, and prioritize streams for protection and restoration.
Methods
Study area
Benthic macroinvertebrate data used in the analysis of index performance was obtained from
samples collected from the Rio Piedras and other stream sites located throughout the island
(Figures 1 and 2). The area of study included three geographical regions, humid east central,
rainy west central, and rainy Luquillo Mountains, all characterized by relatively heavy rainfall
and steep topography. The island's climate is humid subtropical, with rainfall weakly related to
season and amounts generally greater with tropical disturbances September through November.
Stream size ranged first through fourth order, exclusively high and moderate in gradient and
dominated by riffle-run-pool habitat. Streams bottom substrates consisted of boulders (large,
medium, small), cobble, and varied amounts of gravel, sand, and silt.
1
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1994, 2006, 2009, 2011
Puerto Rico Biological Stream Survey's
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2009 Probabilistic n = 50
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Figure 2. Map of stream sites in Puerto Rico.
Study design
Data used to establish the environmental gradients for testing index performance were taken
from stream sites sampled during the period 1994 - 2011. First, index performance was tested
for their response to water pollution in a small urbanized watershed named the Rio Piedras. The
Rio Piedras is known for water pollution typical of highly urban watersheds, including chemical
contamination from stormwater runoff and raw sewage (Lugo et al. 2011, Potter et al. 2013,
Ramirez et al. 2014), and provided a longitudinal gradient of declining water chemistry, physical
habitat, and land use condition. Second, responses of each index were evaluated against a land
use gradient consisting of stream sites of reference quality (Stoddard et al. 2006) and those with
high deforestation. For a site to qualify as meeting reference condition, stream watersheds were
required to have a minimum 85% forest cover since the period of the 1950's until present. This
information was obtained from historical forest maps and current GIS land cover data.
Field sample collection
3
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At each stream location a single riffle area was chosen closest to a predetermined x-site for
collection of a benthic macro invertebrate sample. Macro invertebrates were collected from rock
substrates (cobble and small boulder) using a large frame rectangular kick net, constructed with
800 x 900 um mesh net (Bode 1991). Sample collection was accomplished by placing the kick
net on the stream bottom, mid-stream in the riffle, while gradually working the net downstream
and laterally (approximately two net widths) for 5 minutes. The bottom substrate was vigorously
disturbed by foot so that sufficient organisms would be dislodged and swept into the net.
After a sample was collected, large debris were removed from the net, inspected for organisms
and discarded. Macroinvertebrates retained in the net were placed in a one-liter container and
preserved with 10% buffered formalin. Sample containers were labeled with the appropriate site
information and delivered to the EPA Edison laboratory. The kick net was thoroughly rinsed and
cleaned between stream sites.
In situ measures of water temperature, specific conductance, pH, and dissolved oxygen were
taken at each site. Further for the Rio Piedras, water chemistry samples were collected and
analyzed for 18 parameters (e.g., major anions/cations, nutrients, DOC, TOC, TSS, turbidity).
Measurements of habitat quality were performed using EPA's visual habitat assessment method
(Barbour et al. 1999). All these attributes combined may be directly or indirectly altered by
human activities in watersheds.
Results
BMWP'PR, Mil, PMA, and IBF'PR scores all showed strong responses to the pollution gradient
in the Rio Piedras (Figure 3) and were strongly related to several potential stressors (Table 1).
BMWP'PR scores increase in response to stress, while Mil, PMA, and IBF'PR scores decrease
in response to stress.
BMWP'PR, Mil, PMA, & IBF'PR Scores for Rio Piedras, Puerto Rico
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Figure 3. Comparison of biotic index scores corresponding to a water pollution gradient in the
Rio Piedras.
4
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BMWP'PR
IBF'PR
Mil
PMA
Parameter
P
r
P
r
P
r
P
% Urban
-0.788
0.000000200
0.876
0.000000200
-0.841
0.000000200
-0.923
0.000000200
HSI
0.799
0.000000200
-0.652
0.00586
0.765
0.000159
0.664
0.00472
[CI-]
-0.832
0.000000200
0.737
0.000723
-0.863
0.000000200
-0.788
0.000000200
[N]
-0.750
0.000434
0.839
0.000000200
-0.875
0.000000200
-0.842
0.000000200
[P]
-0.786
0.000000200
0.804
0.000000200
-0.805
0.000000200
-0.845
0.000000200
TSS
-0.405
0.131
0.228
0.403
-0.136
0.620
-0.189
0.489
Turbidity
-0.163
0.533
l,
0.235
0.372
-0.246
0.348
j; _
-0.143
0.586
Table 1. Spearman's correlation of four macroinvertebrate biotic indexes with selected measures
of human disturbance. Yellow cells indicate very significant correlations and green cells indicate
moderately significant correlations.
Land use response of the BMWP'PR, Mil, PMA, and IBF'PR distinguish reference from
deforested stream sites with some degree of separation (Figure 4). Discriminatory power was
greatest for the BMWP'PR, Mil, and IBF'PR indexes with no overlap of the interquartile ranges,
while the PMA index had some overlap of the interquartile ranges.
BMWP'PR tor Reference & Test Silas m Puerto R>co
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^ Reference S85N forest cover) N = Q
2 Tea S«« s (-1J.S toiefl cover) N = 26
IBF'PR for Refcrenc • 4 Test Stte* to PuertoRIco
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\ Reference S«es (>85°*> forea cover) ft = 4?
2 Teg S4esfi5Sfofesi cov«). N = 26
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Mil for Reference 5 Test Sttes In Puerto Rico
1 Reference (>B5N forest cyvei) N -
2 Tea S85% forest cover) N = 42
2 Teat S»t«s(
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Discussion
Use of the Mil, PMA, BMWP'PR, and IBF'PR indexes can be viewed as a starting point in the
development and implementation of stream biological assessment in Puerto Rico, Until the
recent development of these indexes, no macroinvertebrate-based index of biological integrity
had been developed in Puerto Rico and only a limited number of biological assessments of
streams have been performed in Puerto Rico (De Jesus 2008, Ruperto 2008, Ramirez et al. 2009,
de Jesus-Crespo and Ramirez 2011) and throughout the Caribbean islands (Soldner et al. 2004).
Based on the data collected, all four indexes performed well on Puerto Rico streams with
pollution gradients and various land use characteristics. However, additional data is required to
determine the long term credibility and usefulness of the indexes. For now. these indexes
provide water resource managers with additional biological tools to assess and scale the
condition of water quality. In the long term, index data will need examination for their degree of
accuracy, variability (natural and seasonal), and repeatability. In addition, for the development
of biological criteria, index score expectations must be established for reference conditions and
thresholds set that indicate distinct condition classes based on their percent range of deviation.
The Mil and PMA have been through this process of threshold development. Refinement and
application of these indexes will only be enhanced through further analysis of existing data and
the gathering of new data.
There are also advantages and disadvantages on the use of each index from a taxonomic
expertise perspective. Use of the Mil requires the most taxonomic training because
macroinvertebrates are identified to the genus level. Both the BMWP'PR and IBF'PR indexes
rely on intermediate taxonomic resolution at the family level. The PMA requires the least
taxonomic effort with specimen identifications at the major organism level of order and class.
Currently in Puerto Rico there is a lack of broad taxonomic keys and skills required by water
quality professionals to identify macroinvertebrates at and below the family level of taxonomy.
The utility of the PMA index is the ease in which biological conditions could be determined
without the need for extensive information on invertebrate taxonomy. However, in this study the
discriminatory ability was better for the Mil, BMWP'PR, and IBF'PR compared to the PMA
when analyzed for a land use stressor gradient. This might suggest that higher levels of
taxonomic resolution are required for greater discriminatory efficiency in the assessment of some
environmental conditions. Selection of one index or several in combination will be a
compromise between the data quality objectives and taxonomic resources available.
With some modifications each of these indexes have the potential for use throughout the
Caribbean and other regions of the Neotropical zone. The conceptual basis and technical
underpinnings for the original indexes were developed for streams in temperate North America
and Europe, but were modified to take into account zoogeographical differences of aquatic fauna
found in Puerto Rico. Likewise, if these indexes were developed for application in other islands
of the Caribbean they would need to reflect any geographical or sampling method differences.
6
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Literature Cited
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protocols for use in streams and wadeable rivers: periphyton, benthic macroinvertebrates and
fish. Second edition. EPA/841 -B-99-002. U. S. Environmental Protection Agency, Office of
Water, Washington, DC.
Bode, R.W., M. A. Novak, and L.E. Able. 1991. Methods for rapid bioassessment of streams.
New York State Department of Environmental Conservation, Division of Water, Albany, NY.
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system and several biological indices based on macroinvertebrates for water-quality assessment.
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Gray, N. F. and E. Delaney. 2008. Comparison of benthic macroinvertebrate indices for the
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Gutierrez-Fonesca, P.E, Alonso-Rodriguez, A.M., and A. Ramirez. 2016. Aquatic
macroinvertebrates of Puerto Rico as bioindicators of environmental quality. University of
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Kurtenbach, J. K. 2015. Development and use of a percent model affinity for assessment of
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Lugo, A. E., Gonzales, O. M. R. and C. R. Pedraza. 2011. The Rio Piedras watershed and its
surrounding environment. Vol FS-980. US Department of Agriculture, Rio Piedras.
Potter, J. D., W. H. McDowell, A. M. Helton, and M. L. Daley. 2013. Incorporating urban
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Biochemistry.
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Ramirez, A. R., De Jesus-Crespo, D. Martino-Cardona, N. Martinez-Rivera, and S. Burgos-
Caraballo. 2009. Urban streams in Puerto Rico: what can we learn from the tropics? Journal of
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Ramirez, A., K. G. Rosas, A. E. Lugo, and O. M. Ramos-Gonzalez. 2014. Spatio-temporal
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Soldner, M., I. Stephen, L. Ramos, R. Angus, N. C., and M Crane. 2004. Relationship between
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