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8-1980
A Limnological Investigation of a Tropical Fresh-Water Ecosystem: The Belize River, Belize, Central America
Victor J. Gonzalez Western Michigan University
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Recommended Citation Gonzalez, Victor J., "A Limnological Investigation of a Tropical Fresh-Water Ecosystem: The Belize River, Belize, Central America" (1980). Dissertations. 2642. https://scholarworks.wmich.edu/dissertations/2642
This Dissertation-Open Access is brought to you for free and open access by the Graduate College at ScholarWorks at WMU. It has been accepted for inclusion in Dissertations by an authorized administrator of ScholarWorks at WMU. For more information, please contact [email protected]. A LIMNOLOGICAL INVESTIGATION OF A TROPICAL FRESH-WATER ECOSYSTEM: THE BELIZE RIVER, BELIZE, CENTRAL AMERICA
by
Victor J. Gonzalez
A Dissertation Submitted to the Faculty of The Graduate College in partial fulfillment of the requirements for the Degree of Doctor of Philosophy Science Education
Western Michigan University Kalamazoo, Michigan August 1980
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGEMENTS
The author wishes to express his sincere appreciation
to Drs. Clarence J. Goodnight, George G. Mallinson, Richard
W. Pippen, and Dale Warren for their assistance during this
project. Sincere thanks also go to Edward Block, Thomas
Murphy, and members of the communities of Burrell Boom,
Bermudian Landing, Roaring Creek, and Spanish Lookout for
their assistance in the collection of data; the Robins and
the Reyes families for their encouragement; and the Belize
Water & Sewage Authority for their cooperation. Gratitude
is extended to The Graduate College of Western Michigan
University for the fellowship that made my graduate work
possible and for the research grant that helped to finance
this project.
Special thanks go to the members of my immediate family
for their encouragement and understanding over the past few
years.
Victor J. Gonzalez
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G o n za lez , V ictor J. Ba lth a za r
A LIMNOLOGICAL INVESTIGATION OF A TROPICAL FRESH-WATER ECOSYSTEM: THE BELIZE RIVER, BELIZE, CENTRAL AMERICA
Western Michigan University Ph.D. 1980
University Microfilms International 300 N. Zeeb Road, Ann Arbor, M I 48106 18 Bedford Row, London WC1R 4EJ, England
Copyright 1980
by Gonzalez, Victor J. Balthazar All Rights Reserved
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS
ACKNOWLEDGEMENTS ...... ii
LIST OF TABLES ...... V
LIST OF F I G U R E S ...... vii
Chapter
I. INTRODUCTION ...... 1
II. LITERATURE REVIEW ...... 9
Major Reviews on River Ecology ...... 9
Chemical Studies on Belize River ...... 11
Investigations of River Benthos ...... 16
Review of Riparian Planktonic Studies ...... 22
Review of Bacterial Investigations ...... 32
Review of Nektonic Surveys in Central America 36
III. STUDY DESIGN AND METHODOLOGY ...... 39
D e s i g n ...... 39
Methodology ...... 44
IV. RESULTS AND DISCUSSION ...... 55
Chemical Parameter ...... 55
Benthological Parameter ...... 80
Planktonic Parameter ...... 94
Microbiological Parameter ...... 106
Nektonic Parameter ...... 112
V. CONCLUSIONS AND RECOMMENDATIONS ...... 116
iii
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPENDICES
A. DATA FOR PHYSICAL AND CHEMICAL PARAMETERS OF ALL STATIONS DURING BOTH SEASONS ...... 119
B. DATA FOR INVERTEBRATE ORGANISMS COLLECTED AT EACH STATION DURING BOTH SEASONS ...... 14 5
C. DATA FOR PHYTOPLANKTON COLLECTED AT EACH STATION DURING BOTH SEASONS ...... 159
D. DATA FOR ZOOPLANKTON COLLECTED AT EACH STATION DURING BOTH SEASONS ...... 177
E. DATA FOR PLATE COUNTS OF TOTAL BACTERIA, TOTAL COLIFORM, AND YEAST/MOLD ...... 187
F. QUALITATIVE DATA FOR NEKTONIC FAUNA ...... 196
BIBLIOGRAPHY ...... 199
iv
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF TABLES
Table
1. Belize Municipal Water Supply Systems ...... 6
2. Station Number, Name, and Population Data for Vicinity of Each Station, Based on Census of 1970 ...... 42
3. Comparison of Metal and Cation Levels in Belize River at Station 1 ...... 56
4. Comparison of Metal and Cation Levels in Belize River at Station 2 ...... 57
5. Comparison of Metal and Cation Levels in Belize River at Station 3 ...... 58
6. Comparison of Metal and Cation Levels in Belize River at Station 4 ...... 59
7. Comparison of Metal and Cation Levels in Belize River at Station 5 ...... 60
8. Comparison of Metal and Cation Levels in Belize River at Station 6 ...... 61
9. Comparison of Metal and Cation Levels in Belize River at Station 7 ...... 62
10. Comparison of Metal and Cation Levels in Belize River at Station 8 ...... 63
11. Mean Values of Some Physical Factors of Belize River as They Occurred at All Stations During Both Seasons ...... 77
12. Percentages of Invertebrate Groups Occurring at Each Station During Dry Season ...... 86
13. Percentages of Invertebrate Groups Occurring at Each Station During Wet Season ...... 91
14. Species Diversity (d) and Equitability (e) of Algae with Summary Data for All Stations During Dry S e a s o n ...... 94
v
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 15. Species Diversity (d) and Equitability (ej of Algae with Summary Data for All Stations During Wet S e a s o n ...... 95
16. Percentages of Various Algal Phyla Occurring at Each Station During Dry Season ...... 97
17. Percentages of Various Algal Phyla Occurring at Each Station During Wet Season ...... 99
18. Relative Percentages of Major Zooplankton Groups Occurring at Each Station During Dry Season . . .103
19. Relative Percentages of Major Zooplankton Groups Occurring at Each Station During Wet Season . . 105
20. Mean Levels of Total Bacteria, Total Coliform, and Yeast/Mold Counts ± One Standard Deviation 107
vi
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OF FIGURES
Figure
1. Portion of the map of Central America ...... 4
2. The Belize River and its tributaries ...... 8
3. Station numbers and locations along the Belize R i v e r ...... 4 0
4. Occurrence of families of Tricoptera and Ephemeroptera at all stations during both s e a s o n s ...... 81
5. Occurrence of families of Diptera, Coleoptera, and Hemiptera at all stations during both s e a s o n s ...... 83
6. Occurrence of families of Odonata, Plecoptera, and Neuroptera at all stations during both s e a s o n s ...... 84
7. Occurrence of families of Oligochaeta and Gastropoda at all stations during both seasons 8 5
8. Histogram of summary data for total bacteria for all stations during wet and dry seasons . . 109
9. Histogram of total coliform counts for all stations during wet and dry seasons ...... 110
10. Histogram of yeast/mold counts for all stations during wet and dry s easons ...... 113
11. General distribution of the fish fauna of the Belize River as derived from the qualitative data collected ...... 114
vii
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER I
INTRODUCTION
Solving critical water problems for the world's popula
tion will be one of the major tasks facing those involved
with water resource management. Projections of water demand
and water supplies by the World Health Organization show that
the situation in most developing countries is critical and
that the rate of increase in community water supplies is not
sufficient to keep pace with the growing population. It was
estimated that by 1980, 55 percent of the urban population,
or some 390 million people, will not be served with adequate
drinking water. By the year 2000, the world's total annual
water demand, some 2,000 cubic kilometers in 1975, will
triple to 6,000 cubic kilometers (Van der Leeden, 1975).
Because the world's fresh-water supplies are limited
and unevenly distributed over the surface of the earth, it
is imperative that this valuable resource be managed effi
ciently. Yet, man has been modifying water sources in
harmful ways through his activities for centuries. Hynes
(1974) reviewed the history of water pollution and discussed
in detail the physical and biological degradation of rivers
resulting from pollution associated with man's activities.
The discharge of effluents is one of the major factors that
has produced changes. The effluents discharged into rivers
1
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. and other waterways are as varied as the human activities
that produced them. Inert suspensions of finely divided
matter are found in many waterways as a result of mining and
quarrying operations. An attempt to consolidate the immense
volume of literature associated with the various facets of
the problem between mining activity and its external environ
ment has been made (Down, 1978). A review of the whole range
of the environmental impacts of mining is presented along
with the ways for minimizing them.
Wastes from industrial plants are constantly introducing
harmful chemicals into rivers. Recently, an investigation
(Turner & Lindberg, 1978) was made to determine the distribu
tion of mercury in a river-reservoir system that continues to
receive effluents from an inactive chloralkali plant. Data
collected showed that mercury continues to leach from solid
wastes from the plant that closed in 1972 after twenty years
of operation. Elevated levels of mercury in downstream water,
suspended matter, and bottom sediments continue to exist.
Overall results of this study substantiate that the recovery
of the river-reservoir system formerly subjected to high dis
charges of mercury by the plant has been very slow and is far
from complete. Continued losses of mercury from contaminated
solid wastes stored at the plant site are implicated in this
slow recovery. Some chemicals such as ammonia are destroyed
fairly rapidly by oxidation. But others, such as phenolic
and cyanide compounds, are destroyed more slowly. Organic
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. residues constitute a major form of effluent material that
is discharged into rivers and streams. Organic residues
comprise the effluents from a great variety of activities
that include dairies, manure heaps and cattleyards, slaughter
houses, paper mills, cane-sugar factories, and most important
of all, domestic sewage. These effluents usually contain
unstable compounds that are readily oxidized and, in the
process, the dissolved oxygen in the water becomes substan
tially reduced, resulting in a limited aquatic biot.\.
Although the changes associated with effluent discharges
are usually recognized, there has been little documentation
of the conditions of rivers prior to those activities of man
that have resulted in degradation. Comprehensive case
studies of the course of events in a river ecosystem could
provide some guidelines with respect to preventing further
ecological disasters. They could also indicate how to main
tain, and possibly restore, a river's ecosystem in a condi
tion similar to that of its original state.
The developing country of Belize in Central America
(Figure 1) is experiencing population growth and industrial
development. One of the immediate outcomes of this growth
activity has been the development of stress on the country's
waterways. The New River running through the Orange Walk
District is said by the local population to have experienced
a significant decrease in its fish population as a result of
industrial effluent discharges into the river. It is common
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 4
100 200 300
Scale: 1/5.176.000 mile!
MEXICO
CARIBBEAN SEA
BELIZE
GUATEMALA
HONDURAS
EL SALVADOR
Fig. 1.— Portion of the map of Central America (adapted from National Geographic Atlas of the World, 4th ed., 1975).
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. knowledge that raw sewage is being dumped into the Belize
River as it flows through the city of Belize. With the
recent establishment of the new capital city and the
increased industrial activity in that region, the nearby
Belize River faces a potential threat of further degradation.
At present the water supply system for the country of
Belize is from both groundwater and surface water sources,
as is shown in Table 1.
With increasing demands being placed on the water
resources of Belize, adequate management programs for such
resources must be developed. These management programs would
require a clear understanding of the goals to be achieved,
the fundamental ecological information, and the means to
achieve the stated goals.
Serving as the water source for the city of Belmopan
and destined shortly to become the primary source of water
supply for the city of Belize, the Belize River is a strate
gic resource and warrants a fundamental understanding of its
physical and biological nature. The study described herein
aims at approaching a comprehensive understanding of the
ecosystem of the Belize River.
The Belize River flows in a west-easterly direction
across the country of Belize. The source of the river is
the Mountain Pine Ridge and the Department of El Peten in
Guatemala. These two branches are referred to as the Eastern
Branch and the Western Branch, respectively. On its way to
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.
10 10 miles from city to 400,000-gallon capacity storage tank in Belize City and distributed reservoir Water from Belize River is treated 200,000 gallons town stored in 50,000-galloncity storage capatank 2 reservoirs with total capacity of storage capacity, 360,000 gallons Water from Macal River pumped into Water SourceGround Description of System Water pumped from 3 shallow wells GroundSurface Water from 2 wells 1 mile west of Not available System capacity, 150,000 gallons
Source: National Water and Sewerage Authority, 1972. Total population in (pop. (pop. 40,000) TABLE 1.— Belize Municipal Water Supply Systemsa Belize City Municipality Belmopan Surface Benque Viejo del Carmen Ground Spring water pumped to storage Corozal Town San Ignacio Stann Creek Town Punta Gorda Rain and ground Rain water augmented by well; total urban areas served. tion) by public water systems: 33,000 (about 50% of urban popula
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 7
the sea, the river meanders over a distance of more than 100
miles. It flows by several small communities, the recently
established capital city of Belmopan, and meets the sea at
the large port city of Belize (Figure 2).
To avoid a severe degradation of the water quality in
this river, a continuing effort should be made to assess the
ecological relationships that exist within it. Bacterial
counts, chemical analyses, biota assessments, and other
parameters that are necessary in the determination of water
quality should be the major aspects of the continuing effort.
The information so gained will provide the fundamental envi
ronmental data that are necessary for the development and
reassessment of management programs. Control measures
applied to aquatic ecosystems in the absence of continuous
monitoring are apt to be inappropriate. Some measures may
overprotect the system at times and underprotect it at other
times, for the capacity of the ecosystem to receive waste
is not constant (Cairns, 1967).
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Landingj 30 25 Soaring Creek Labouring 20 Fig. 2.— The Belize River and its tributaries.
Lookout J J Spanish Scale: 1/500,000 Mountain Mountain Pine Ridge
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER II
LITERATURE REVIEW
A survey of the literature fails to indicate that many
significant studies have been carried out to provide infor
mation about the multidimensional aspects of tropical fresh
water ecosystems.
From a global perspective, river ecology has only
recently become the focus of increased attention. Indeed,
only recently, the first Institute of Potamology (potamos,
river) in North America was founded at the University of
Louisville, Kentucky, for the study of rivers.
Major Reviews on River Ecology
Over the past several years, a few books have been pub
lished that shed some light on the state of knowledge amassed
by riparian ecological researchers. One of the earliest
(Reid, 1961) was designed as an introduction to the elemen
tary factors and processes that operate in streams. This
work summarized some aspects of the knowledge that had been
gathered from the study of inland waters. These various
aspects included information in the areas of geology, hydrol
ogy, chemistry, and biology. Morisawa (1968) , in her account
of the dynamics and morphology of flowing waters, attempted
to explain some of the natural forces that govern the way
9
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. in which water works. This account presents the dynamic
principles guiding the activity of rivers in terms that are
understandable to those who have little or no previous
knowledge of the subject. Hynes (197 0) attempted to provide
a comprehensive and critical review of the then-current
literature on the biology of rivers and streams. His review
covered the physical and chemical aspects of river systems
and their relationships with the micro- and macro-aquatic
life forms present. In a more recent report, Hynes (1974)
focused on the theme of pollution in rivers and streams.
This report aimed merely at explainirg in fairly simple terms
the extent of present knowledge and at indicating by means
of references where more detailed information could be
obtained.
Like most of the preceding reports, that of Whitton
(1975) described in detail the physical and chemical aspects
of river systems and attempted to integrate the then-current
data into a comprehensive review. His detailed discussion
of the Amazon River represents one of the few comprehensive
reviews of a tropical fresh-water ecosystem. Sternberg
(1975) also assembled information on the Amazon River of
Brazil. His study deals primarily with the geophysical fea
tures of this river, and little reference is made to the
resident biological fauna and flora or to the chemical
composition of the system.
Rivers are generally thought to have widely varying
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. compositions because of the different solubilities of rocks,
the seasonal variations of rainfall and runoff, and the con
tributions of groundwater. In Belize, for example, where
rainfall may at times be heavy for short periods during the
rainy season, the Belize River is enriched almost entirely
by rainfall runoff transporting soluble products and enormous
masses of silt. During periods when the rainfall is light
or absent, as in the dry season, the river is enriched pri
marily by groundwater that, by its long contact with rocks,
has t greater concentration of dissolved material.
Chemical Studies on Belize River
For several years, studies relating to the Belize River
sought to determine the drinking quality of the water and
its potential as a source of potable water for the city of
Belize. In one early study (Newham, 1922), samples taken at
Gabb's Bank showed 40 parts of chloride per 100,000. At
Lord's Bank, this excess of solute was no longer evident.
It is worth mentioning that the Newham samples were taken
after abnormally dry weather in the month of May 1922. The
results of these analyses suggested that further testing
should be carried out and that if the water is to be taken
for the city supply, it should be subject to treatment
involving sedimentation, filtration, and chlorination.
In a follow-up study (Humphrey, 1925) , water samples
were taken for analysis from the same river between 9-1/2
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 12
miles and 15-3/4 miles from the mouth. The results indicated
that the quantity of solid matter in the water was high and
that a quarter of it was organic in nature. The salt con
centration was also high, but there was no reason to suspect
excretal contamination. The source of salinity was thought
to be primarily marine in nature. Dissolved oxygen was con
sidered to be within the acceptable limits, and the ammonia
not excessive. As the albuminoid ammonia exceeded those in
the free and saline states, the indication is that of vege
table and not animal contamination. The water was noted to
be neutral or slightly alkaline in nature, and its taste and
general appearance were of a rather high quality.
Some other studies involving chemical analyses were
primarily concerned with the chloride content and the hard
ness factor. In another study, Humphrey (1945) reviewed
data collected previously on these two aspects as well as
his own data. His water samples, after collection, were
sent to Jamaica for testing, and the results showed an
increased value when compared with the earlier data. While
it was concluded that the water was satisfactory for drinking
purposes, recommendations were made for softening the water
on the assumption that the water would be used for other
domestic purposes.
A later study (R. L. Walker, 1960), aimed at determining
the potential of the river system of Belize as a source of
hydroelectric power, reported on the volume and rate of flow
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 13
of the Western Branch of the river. From data gathered, it
was concluded that hydroelectric power potential in Belize
was substantial in terms of the present and foreseeable
demands. Recommendations were made that a hydrometric survey
be undertaken immediately to amass the basic data essential
to any future development.
In his report, Hickok (1964) sought to evaluate the
existing hydrologic data so that preliminary plans and cost
estimates could be prepared for the hydrologic studies needed
to determine the future water needs of Belize City. During
the course of this report, it was noted that permanent gaug
ing stations were not maintained on the Belize River and that
reliable dry season or low flow measurements were not found.
Thus, the recommendation was made that a systematic program
of river flow and water quality at selected locations along
the Belize River be initiated.
S. H. Walker (197 0) provided data from tests of water
from the Belize and Sibun rivers made by the hydrology sec
tion of the Land Resources Division at the end of the 1970
dry season. Data collected from other relevant investiga
tions were included and compared with those collected by the
hydrology section. On the Belize River, water from Davis
Bank downstream to 3 miles below the Boom Ferry was sampled
at ten stations. The total dissolved solids ranged from 640
to 790 mg/1 for the upstream nine stations, with an abrupt
rise from 74 5 to over 5,000 mg/1 at 24 feet below the surface
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 14
at the tenth station. Sodium chloride levels were 113 to
138 mg/1 and 68 to 83 mg/1, respectively, with hardness
levels ranging from 479 to 547 mg/1 across all ten stations.
The pH values were reported as being constant at 7.5, and
significant iron levels (less than 4.5 mg/1) were not found.
In addition to establishing and publicizing certain facts
about the two rivers, the author sought to identify the need
for appropriate planning and riparian legislation prior to
development of the area. It was concluded that there was a
need for a body to coordinate the task of data collection,
policy formation, planning, and legislation regarding water
use.
The 1961 feasibility report by Weston, on the subject
of water supply for Belize City, reviewed the entire existing
water situation of the city and provided alternatives to the
main source: well fields. Among the alternatives presented
was the use of water from the Belize River. It was recom
mended that salt-water intrusion, water quality, and dry
weather flow be checked on the Belize River and that the
feasibility of a salt-water barrier be investigated.
Several other reports followed that were prepared with
the same aim by the Canadian International Development
Agency. In each instance, ground wells in the immediate
vicinity of the Belize River were viewed as the most practi
cal and feasible source. With the river serving as the
ultimate source through filtration, the need for monitoring
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 15
the water quality was repeatedly mentioned (CBA Engineering
Ltd., 1971; PAHO/WHO, 1976). A more recent report (Stanley
Associates, 1977) claimed that the Belize River is an ade
quate source of water supply for the city. Water from the
river was sampled around the Double Run region for the pur
pose of determining its bacteriological and chemical quality.
Raw water turbidity was quite low, with a range of 5 to 10
JTU during the dry season and with a consequential increase
after periods of heavy rainfall. The range in the latter
case was approximately 30 to 35 JTU. Alkalinity values also
showed consequential differences between the seasons, with
the higher values occurring during the dry season. The pH
values fluctuated between 6.8 and 7.7 during the dry period
and between 6.5 and 7.2 during the wet season. Corresponding
differences were also noted in the concentrations of other
parameters such as hardness, chlorides, and sulfates because
of the dilution effect. The result of bacterial testing
showed a total coliform concentration of 3,500 colonies/100
ml of water sampled. It was concluded from the overall
results of these tests that the water quality of the Belize
River was relatively high and that conventional techniques
and equipment would suffice to treat the water so that it
could be brought to acceptable standards. Furthermore, it
was recommended that necessary steps be taken to prevent
pollution of the river from upstream sources.
Evidence was not found to indicate that the chemical
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 16
data on the composition of the Belize River described in the
above studies have been related to the other parameters of
the river's ecosystem. Whereas the study described herein
is aimed at identifying ecological relationships, the chemi
cal data so far gathered by previous investigators are of
great importance in that they serve as reference points.
Investigations on River Benthos
One of the characteristic features of tropical riparian
ecosystems is the presence of a diversified benthic fauna.
Stout and Vandermeer (1975) , in their quantitative comparison
of richness between tropical and mid-latitude species of
rheophile insects in three streams, found a significantly
higher degree of richness in the tropical water body. Within
the tropical stream, they further observed a greater number
of species during the dry season than in the wet season.
In a survey of the main fresh-water systems of tropical
Africa and their peculiar problems, Beadle (1974) also dis
cussed the great diversity of aquatic organisms in these
water bodies.
It is generally true that the numbers of species of
animals and plants in most habitats in the humid tropics are
much greater than at greater latitudes. The explanation of
this phenomenon has received a great deal of attention. Pub
lished reports on the subject have led to the general conclu
sion that the climate differences may result in differences
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 17
in the operation of natural selection (Dobshansky, 1959;
Fischer, 1960; Pianka, 1966). Cain (1969) explained that
at greater latitude the seasonal swing in climate, especially
in temperature, has put a premium on adaptation to the chang
ing physical environment. Destruction of species and their
habitats has occurred from time to time, and the seasonal
changes have demanded adaptations to at least two kinds of
climate or periodic migration to avoid the change. This
lack of environmental stability has prevented the development
of complex ecosystems like those found in the tropics. In
the tropics, selection seems to be concerned primarily with
relationships among organisms. With a relatively stable
climate, physical factors seem to be of less importance.
This situation has thus permitted the evolution by natural
selection of complicated ecosystems in which a great number
of species are adapted to a large number of habitats with
varied components.
A review of the literature has revealed that numerous
studies have been done on the ecological relationships of
benthic organisms to their environment. Although some of
the studies described do not deal with the tropics, they do
provide some insights into the possible relationships that
might be revealed during the present investigation. Williams
and Mundie (1978) investigated the selection by stream
invertebrates of environments of varying substrate particle
sizes and the influence of sand on the selection process.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 18
This field experiment demonstrated that, in running water,
benthic invertebrates exhibited a preference for different
substrate particle sizes. Maximal numbers and biomass
occurred on gravel that had a mean diameter of 24.7 mm. The
data also showed that diversity was greatest on larger gravel
that had a mean diameter of 4 0.8 mm. The addition of a
limited amount of sand to both gravel sizes seemed to affect
only a few species.
In a report on invertebrate distribution, Rabeni and
Minshall (1977) sought to identify the relationships between
microdistribution and physical factors such as current
velocity, substratum particle size, silt, and detritus. From
the data gathered, it was reported that substratum-detritus
interactions were the overriding influence on insect micro
distribution. Current velocity and mild deposition of silt
played only secondary roles. The results suggested that the
insects were colonizing in response to the amount of detri
tus. It was concluded that detritus is of primary importance
to insects' microdistribution, but that it was the physical
factor of substratum particle size that determined the dis
tribution of detritus.
Other investigations sought to determine the vertical
distribution of the invertebrate fauna in stream beds. Cole
man and Hynes (1970), in their report, described the use of
a sampler that permitted collection of benthic fauna to a
depth of 30 cm. In their investigation, the 30-cm depth was
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 19
divided into four layers of 7.5 cm each. The collections
made included various groups of organisms such as Oligochaeta,
Mollusca, Copepoda, Plecoptera, Ephemeroptera, and Chirono-
midae. The results showed that 20 percent of the total
number of organisms were in the top layer and 2 6 percent in
the bottom. The remaining percentage was evenly distributed
in the two middle layers. This type of distribution was
generally found for all the groups of organisms present.
Only Simulium appeared to be confined to the top.
A similar study was carried out in a Malaysian stream
bed. The apparatus employed in this investigation allowed
sampling of the benthic fauna to a depth of 50 cm. The
results demonstrated that stream animals occurred in signif
icant numbers deep in the bottom sediments. Furthermore, it
was shown that, at most, only about half the benthic organ
isms lived in the upper 10 cm. The significance of the deep-
living fauna was thought to be related to the regulation of
community density and to the recolonization of denuded areas
(Bishop, 1973).
Recently, Pecharsky (1979) sought to describe the effect
of varying faunal densities on the distribution of inverte
brates within the substrate of a stony stream. The param
eters of substrate, current, temperature, and dissolved
oxygen were kept constant so as to identify the biological
interactions that might occur. The data collected seem to
suggest that benthic invertebrates preferred low density
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areas of substrate to high density areas of comparable
physical and chemical quality. It was concluded that the
nature of the substrate habitats is usually responsible for
attracting particular sizes and assemblages of species.
These organisms then respond to each other's presence in a
density-dependent fashion. This interaction promoted the
achievement of a consistent optimal density within the par
ticular habitat. Densities thus reflect a capacity of
benthic invertebrates to detect each other's presence and
to colonize available habitats.
In studying the effects of water currents on fresh-water
snails, Moore (1964) exposed Stagnicola palustris and Physa
propinqua to six water velocities between .5 and 3.0 ft./sec.
on six different substrates. The snails were tested for
their ability to remain attached to the substrate under dif
ferent current speeds. Of the different sizes of snails
used, the middle-size group was dislodged more easily than
the other two size groups. Stagnicola was generally less
easily dislodged than Physa. The greatest dislodgement was
observed from sand followed by clay, caliche rock, plexi
glass, pea gravel, and basalt rock. Also, increased veloc
ities caused greater dislodgement.
In tropical situations during periods of heavy rainfall,
when flooding may induce scouring of the river bottom, the
entire benthis fauna may be wiped out or greatly reduced.
Yet, recolonization does occur and leads to the development
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of a fauna similar in density and diversity to that prior
to the scouring effect. Four factors are said to be involved
in the recolonization of stream bottoms that have been
denuded. They include downstream drift, upstream migration
within the water, vertical upward migration from within the
substrate, and aerial egg deposition, that is, oviposition
by adult insects.
In their attempt to illustrate the relative importance
of these four sources to the fully recolonized state, Wil
liams and Hynes (1976) used four different traps to collect
samples. From the results of their experiments, it was
apparent that all four sources of recolonizers were important
in repopulating denuded areas of the substrate. It was noted
that caution should be applied when attributing total recolo
nization of benthic organisms to one means and that any one
isolated source may take longer in allowing reestablishment
of previous density and diversity levels.
In periods of severe drought, the benthic fauna may also
be decimated. Yet, recolonization occurs. McLachlan (1974)
investigated the recovery of the mud substrate and its asso
ciated fauna following a dry phase in a tropical lake. It
was noted that after heavy rainfalls, refilling was completed
within five months. Six weeks after refilling, the benthic
insect population was up to 3,500 mg/m2. The pioneering
population in this instance was mainly the larvae of Chirono-
mus transvaalensis, that later gave way to a more diversified
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population.
Some attempts have been made to determine the effects
of the chemical composition of water on the ecology of ben
thic organisms. Feance (1978) investigated some aspects of
the biology and distribution patterns of Ephemerella funer-
alis in a watershed with streams of varying acidity. The
results indicated that E. funeralis decreased in abundance
with decreasing stream pH and decreasing organic matter. A
decrease in growth rate in acidified zones and a general
movement from low-velocity organic accumulations into
inorganic substrates where greater velocities occurred were
also noted.
In another study, Bell (1971) investigated the effect
of low pH on the survival and emergence of aquatic insects.
His results indicated that aquatic insects differed markedly
in pH tolerance. In general, the caddis flies appeared
highly tolerant to low pH. The stoneflies and dragonflies
were moderately tolerant and the mayflies were fairly
sensitive.
Review of Riparian Planktonic Studies
One of the major parameters of riparian ecosystems is
the existence of planktonic communities. The ecology of
these communities has been the subject of numerous investiga
tions. However, the major portion of the research studies
has been carried out on the communities of temperate water
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bodies. Blum (1956), in his work, attempted to determine
the relationship between the plankton population and the
physical and chemical attributes of the river. His effort
is one of the comprehensive surveys that summarizes much of
the data gathered previously. Another thorough review of
the literature on fresh-water phytoplankton is that of
Hutchinson (1967). The greater portion of this work is
devoted to the ecology of plankton, and many aspects of this
subject are treated in detail.
It is generally accepted that the phytoplankton of
fresh-water ecosystems is a diverse association of prokaryo
tic blue-green algae and eukaryotic greens, desmids, diatoms,
dinoflagellates, chrysophytes, and crytomonads. Similar
associations may be found in tropical regions, for, in
general, algae species are widely distributed throughout the
world owing to their easy dispersal and to the similarity of
aquatic environments. From this standpoint, the studies on
the ecology of temperate fresh-water algae are of signifi
cance to the study described in this paper. These studies
point to ecological associations that could well be reflected
in the ecosystem of the Belize River.
It is evident that numerous factors influence the ecol
ogy of fresh-water phytoplankton, and numerous studies have
been carried out to demonstrate the various relationships.
For example, Butcher (1964), in his study of riparian ecol
ogy, noted that as rivers become larger, certain changes in
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the potamoplankton can be expected to occur. Specifically,
these changes include the increase of the relative importance
of small greens and blue-greens over diatoms such as Synedra
and Fragilaria. These changes are considered to be succes-
sional and of importance to the river biota.
In general, the development of potamoplankton appears
to depend on the "age" of the water. Eddy (1934), seeking
to describe the plankton communities of fresh water, noted
that there is an initial increase in plankton with time and
distance going downstream. He presented the view that the
amount of plankton in river water depends upon the length of
time required for the water to pass downstream from head
water sources.
In a later study on the plankton community and the asso
ciated water quality conditions in the Sacramento River,
Greenberg (1964) noted that there was a gradual increase in
the total number of plankters as the water progressed down
stream. A statistical evaluation of the number of plankters
and the chemical and physical parameters of water quality
and movement indicated that water temperature was the single
most significant factor affecting plankton development in
that region of the river not affected by tidal action. Water
temperature, stream flow, and biological oxygen demand
accounted for about 60 percent of the variation in plankton
numbers. Diatoms, Synedra, Cyclotella, and Meiosira were
generally predominant. The data from this investigation
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indicated that the zooplankton population did not represent
a significant portion of the total plankton community.
Recently, Richards and Happey-Wood (1979) sought to
describe the distribution pattern of four species of plank
tonic algae: Asterionella formosa, Tabellaria flocculosa,
Chlorella vulgaris, and Chlamydomonas moewussi. By applica
tion of a pattern analysis technique, the surface distribu
tions in the standing crop were observed to be contiguous
with patterns of horizontal distributions that differ among
species in dimension and intensity. Extensive analysis of
the distribution of Asterionella at contrasting times of the
year indicated the patterns existing in horizontal distribu
tion are a recurrent phenomenon.
Several studies have been carried out to determine the
effect of water quality on plankton communities. Lane and
Levins (1977) investigated the effects of nutrient enrichment
on model plankton communities. Loop analysis was employed
to demonstrate the properties of a set of models containing
three kinds of algae and three kinds of nutrients. Many
unexpected effects appeared to be related to the interactions
within the network. However, it was evident that one-link
physiological effects could not be extrapolated to ecological
situations, and recommendations were made that a more holis
tic approach be taken when considering the effects of
nutrient enrichment on plankton communities.
In another study, Tilman et al. (1976) investigated the
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morphoraetric changes in Asterionella formosa colonies under
phosphate and silicate limitations. Steady state populations
of this organism showed that the numbers of cell/colony were
greatly influenced by both phosphate and silicate limita
tions. Under phosphate limitation, the numbers of cell/
colony decreased with decreasing steady state growth rate in
a linear manner. Under silicate limitations, the numbers of
cell/colony increased with decreasing steady state growth
rate in an approximately exponential manner.
Investigating the effect of current velocities on growth
rate, Whitford (1960a) submitted several species of fresh
water algae to varying current strengths. Eleven species
grew better in flowing water than they did in still water.
Ten species died when placed in still water, but survived in
a current. The results indicated that current velocities
must exceed 1/2 ft. or 15 cm/sec. to affect growth.
In another study, Whitford and Schumacker (1964)
attempted to demonstrate the effect of a current on respira
tion and mineral uptake in Spirogyra and Qedogonium. Respi
ration rates in the dark in still and running water were
determined by measurement of the carbon dioxide liberated.
Uptake of phosphorus (P33) was measured by radioactive count
ing. Both the lotic and lentic species studied had higher
rates of respiration and of phosphorus uptake in a current.
Lotic species showed a greater response to a current, thus
indicating a higher metabolic rate. Uptake of phosphorus
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was directly proportional to current speeds up to 4 0 cm/sec.
Apart from influencing the growth rate of fresh-water
algae, current velocities are also related to the distribu
tion of the plankton. Current attaining speeds greater than
5 m/sec. have been shown to reduce the algae flora to those
members that are firmly attached to the substrate. Examples
of such algae are Ulothrix zonata and Lemannea fluviatilis
(Whitton, 1975). At slower current velocities, the algae
community is dominated by Stigeoclonium, Oedogonium, and
Tribonema (McIntyre, 1966).
Other factors that are related to the plankton commu
nities of fresh-water bodies are those of temperature and
substrate-type. Generally, the mean temperature in streams
and rivers tends to increase from source to mouth, and vari
ous algae groups are distributed along this spectrum (Blum,
196 0). In the case of substrate-type, muddy substrates do
not favor, an abundant population of algae adapted for firm
attachment. Conversely, rocky substrate-types will not sup
port a community of algae that are not adapted for firm
attachment. Furthermore, the chemical composition of the
substrate may influence the type of algae that prevails.
For example, Cladophera glomerata tend to abound in waters
in which the alkalinity is contributed by the substrate
(Blum, 1960).
In a recent study, Cloern (1977) investigated the
effects of light intensity and temperature on the growth
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rate and nutrient uptake of Cryptomonas ovata. Specific
growth rates were measured on batch cultures at fourteen
light-temperature conditions. Both maximal growth rate and
optimal light intensity fit an empirical function that
increased exponentially with temperature up to an optimum
and then declined rapidly as the temperature exceeded the
optimum. Rates of phosphate, ammonia, and nitrate uptake
were measured separately at sixteen combinations of light
and temperature. The investigator noted that with substrate
saturated with nitrate, the uptake of the nitrate proceeded
at slow rates in the dark and was stimulated by both
increased temperature and light intensity. Ammonia uptake
was also stimulated by increased temperature and radiation.
The rates of ammonia uptake were higher at all temperatures
than were the rates of nitrate uptake. Below 20°C, phosphate
uptake was more rapid in the dark than in the light but was
light-enhanced at 26°C.
The planktonic community of fresh-water bodies also
interacts with the other aquatic life forms in the environ
ment. With the use of the scanning electron microscope and
autoradiographic techniques, Paerl (1976) showed that bac
teria are attached specifically at the polar regions of
heterocysts of Anabaena and Aphanizomenon. These algae are
known N2 fixers. Such attachments were recorded to be at
peak levels during bloom periods. It is thought that the
attached bacteria assimilated substances released by the
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heterocysts. If left to accumulate, these substances could
reduce the growth rate of the N2 fixers. Bacterial respira
tion of the organic substance may be effective enough to
allow for the concurrent high rates of algae photosynthesis
and N2 fixation during blooms.
Recently, Porter (1977) reviewed the ecological condi
tions at the plant-animal interface in fresh-water ecosystems.
The work described features of phytoplankton and zooplankton
that are pertinent to understanding their interactions and
documented the role that microscopic grazers play in deter
mining phytoplankton diversity and succession. It was noted
that microscopic grazers feed differentially on planktonic
algae. It was suggested that this discriminating feeding
behavior influences the phytoplankton community structure
and succession in ways that are analogous to the effects of
herbivores in terrestrial plant communities.
The phytoplankton also provides a food source for many
invertebrates and other organisms in the aquatic ecosystem.
Hynes (1970), in his work on the ecology of flowing waters,
discussed this topic in some detail.
Part of the planktonic community of rivers and streams
is made up of zooplankton. It is thought by .some aquatic
biologists that the zooplankton of rivers are transient,
that is, they do not originate in the river proper itself
but are introduced from the drainage basin ponds, lakes,
and backwaters (Whitton, 1975). However, some of the
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related literature shows that zooplankton may form an inte
gral and intrinsic part of a river's fauna and contribute
significantly to its productivity (Hutchinson, 1967; Hynes,
1970).
Some riparian studies in this area generally point out
that zooplankton constitute a relatively small portion of
the aquatic biomass. Reinhard (1931) , in his work on the
plankton of rivers, found that phytoplankton outnumbered
river zooplankton by a ratio of 5:1. In another study cited
earlier in this review, Greenberg (1964) found that the zoo
plankton were relatively insignificant in the Sacramento
River. Their contributions to the total plankton composition
ranged from 0 to 10 percent.
The major groups of zooplankton that generally occur in
river ecosystems are the non-pigmented Protozoa, the Roti
fers, the Cladocera, and the Copepoda. Of these, Rotifers
tend to be the most frequently occurring group. L. G.
Williams (1966), in his study on the distribution of zoo
plankton, collected samples routinely at 128 sampling sta
tions on the major rivers and the Great Lakes of the United
States. The data indicated that Rotifers were the most
numerous metazoans.
Lynch (1979) recently investigated the relationships
of predation to the structure of the zooplankton community
of a small fresh-water body. This investigation sought pri
marily to determine the mechanisms that were involved in the
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maintenance of the zooplankton community. The findings of
the study indicated that a mechanistic interpretation of the
structure of the community could not be made solely on the
basis of predation, but also requires an evaluation of the
relative competitive abilities of the herbivores.
In another study, the vertical migration in zooplankton
as a predator-avoidance mechanism was studied (Zaret &
Suffern, 1976). The findings showed that diel vertical
migration patterns of prey populations assumed distributions
which resulted in lessened predation by the dominant plank-
tivores. Such patterns apparently resulted when prey popula
tions were under intense selective pressure from visually
dependent predators.
Numerous factors influence the zooplankton community
of an aquatic ecosystem. It is generally accepted that zoo
plankton development is more pronounced in slower moving
portions of a river system where deeper water, reduced cur
rent velocities, and silt deposition tend to make such sites
indistinguishable from typical lentic habitats.
Light and temperature also exert some influence over
the development of zooplankton populations. These factors
affect phytoplankton productivity that in turn affects the
zooplankton.
One other factor that exerts influence on riparian
plankton communities is seasonal change. In the tropics,
where the amount of rainfall is the prominent feature in
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seasonal change, one may expect dramatic fluctuations in the
plankton population in accord with the amount of precipita
tion. Precipitation alters the chemical nature of the
aquatic system and thus leads to a change in the population
that can inhabit the system. Scouring, resulting from flood
situations during the rainy season, also alters the plankton
population. A review of the literature fails to reveal any
consequential information on the effects of seasonal changes
in the tropics on plankton communities.
Review of Bacterial Investigations
One of the commonly used parameters of raw water quality
is the quantitative determination of the presence and abun
dance of total bacteria, total coliform, and yeast/mold. The
general lack of information in this area of ecological defin
itiveness has been discussed by Hynes (1970). Escherichia
coli is the most widely used indicator of fecal pollution.
Many investigators, however, advocate the use of Streptococ
cus faecales as the indicative organism. It has been sug
gested that counts of both E. coli and S. faecales may be a
more accurate indication of fecal contamination. Direct
search for specific pathogens are both lengthy and impracti
cal for routine purposes. Today, simple and rapid tests
have been developed for the detection of intestinal organisms
that may be pathogenic in nature.
Contamination by sewage and human wastes is probably
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the greatest danger associated with drinking water. With
the Belize River being considered as the primary source of
water for the city of Belize, it was recommended that at all
points of supply the water quality should meet the chemical,
bacterial, and physiological standards as suggested by the
World Health Organization (PAHO/WHO, 1976).
Little has been done on the bacterial quantification
of water samples taken from the Belize River. One of the
few studies showed that samples taken from the Belize River
at a point 100 feet downstream from the confluence with
Roaring Creek had both higher total bacterial and coliform
counts than did water samples taken from the Roaring Creek
at Savannah Bank, 10 miles upstream from the village of
Roaring Creek (Scott et al., 1963). S. H. Walker (1970) did
not include bacterial tests in his work on the Belize River,
but did comment on the need for such testing to determine if
pathogens.are present since some contamination is inevitable
in surface waters. Recently, a study was made that included
one coliform count on the raw water of the Belize River. The
sample was taken from the Double Run region and showed 3,500
colonies per 100 ml (Stanley Associates, 1977).
No attempts were made in the above-mentioned studies to
determine the relationship between the occurrence of bac
terial populations and the physical, chemical, or biological
parameters of the river. It was demonstrated by Brasfield
(1972) that relationships do exist. After obtaining the
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data, Brasfield carried out stepwise multilinear regression
analyses to determine which environmental factors were sig
nificantly correlated with the numbers of bacteria present.
Log total bacteria were correlated positively with bicarbon
ate, phosphate, and detergent concentrations. Log coliforms
were correlated positively with phosphate and sulfate concen
trations and negatively with chloride concentrations. Log
fecal streptococci were correlated positively with bicarbon
ate and chloride concentrations.
In another study, Hendricks (1972) sought to determine
the relation of nutrient conditions and growth rate of
enteric bacteria present naturally in river water. Water
samples were taken 750 meters below a sewage outfall and
then autoclaved. The bacteria were then introduced into the
autoclaved water samples and allowed to grow. The data
gathered indicated that these organisms were able to grow
under stringent nutrient conditions. The study also showed
that there are sufficient nutrients in the autoclaved river
water to support limited bacterial growth.
The occurrence of any such relationships as those
described above will be discussed in this report if they
exist in the Belize River.
A search of the literature failed to reveal the exis
tence of any report dealing with yeast/mold counts made on
water samples taken from the Belize River or on water samples
taken from other tropical aquatic systems. Yet, a few
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studies have been conducted elsewhere in attempts to describe
the general ecology of yeasts that inhabit aquatic environ
ments. One such study (Ahearn et al., 1968) provides data
on the ecology of yeasts from aquatic regions of South
Florida. Results showed that while there are high yeast
densities in fresh water, the incidence of the organisms
decreased markedly with lowered organic content, increasing
salinity, and remoteness from land. Definite distribution
patterns were exhibited by certain species. For example,
Candida krusi was typical of fresh water, while Candida
diddensii was found only in sea water. Furthermore, adven
titious human pathogens, Candida albicans, and Torulopsis
glabrata were isolated infrequently and their presence
appeared to be related to organic pollution of animal origin.
In an earlier study (Cooke, 1961), an attempt was made
to determine the effects of pollution on fungal populations.
Water samples and stream-bed samples were taken from a stream
that was subjected to pollution by direct dumping of raw
sewage and sewage that had passed through a primary-type
treatment plant. Results of the analyses showed that the
fungal populations increased significantly with organic
enrichment.
Wollett and Hedricks (1970), in their report, presented
the results of a preliminary qualitative investigation of
yeast populations in thirteen polluted fresh-water habitats.
Included in the same report were data quantitatively
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comparing the yeast population in three of the thirteen
locations. The three locations were described as having
(a) low pollution levels, (b) heavy industrial waste pollu
tion, and (c) heavy domestic waste pollution. Results showed
that the presence of human wastes was especially associated
with large increases in the proportion of Candida yeasts in
the environment. The genus Rhodotorula was consistently
present in all locations, but the genus Cryptococcus was a
major component of the yeast population in non-polluted or
lightly polluted fresh water.
Although the above studies relating to yeast ecology
were not conducted in a tropical setting, they are important
in that they describe possible relationships that could well
exist in tropical fresh-water ecosystems.
Review of Nektonic Surveys in Central America
One final aspect of a tropical riparian ecosystem that
is worthy of comment is the nektonic fauna, particularly the
ichthyological fauna. An early attempt to review the ichthy
ology of Central America was carried out by Regan (1906-
1908). His work summarized the then-current knowledge of
the distribution of fresh-water fish in that .region. In
this survey, the distribution of fresh-water fish in all of
Mexico is included.
More recently, Miller (1966) undertook the task of
reviewing the geographical distribution of the fish in
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Central American fresh-water bodies. He noted that the con
tinental region from the Isthmus of Tehuantepec to the
Colombian border contains about 4 56 species of fishes. Of
these 456 species, over 75 percent include the Cryprinodonti-
dae, the Poeciliidae, the Cichlidae, and marine invaders
(peripheral fishes). About one-third of the latter has
taken up more or less permanent residence in fresh water.
Miller further reported that there are 104 primary species
in ten families, 165 secondary species in six families, and
some 187 peripheral species distributed among thirty fam
ilies. Poeciliids and cichlids are said to be particularly
rich and diverse. Together, they comprise about 139 species.
Characins are numerous only in the Panamanian region, which
they and five South American catfish families have recently
invaded. Except for gars, no North American family of fish
has reached beyond northern Guatemala.
In the country of Belize, one of the earliest studies
done in the area of fresh-water fish distribution is the
work of Hubbs (1935). He collected and classified fish pri
marily from the northern part of Belize and from the Belize
River.
Recently, Thomerson and Greenfield (1972.) made numerous
collections of the fish fauna of Belize and later devised a
classification system for the fresh-water fish of Belize.
Apart from the distribution patterns and the classifi
cation schemes, little has been done on the ecology of
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Central American fresh-water fish, and a review of the
literature fails to reveal any such study done in the
country of Belize.
This review indicates that there is a void in the
literature relating to tropical fresh-water ecosystems. The
study described in this report aims at providing some basic
information on the limnology of a tropical fresh-water
system.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER III
STUDY DESIGN AND METHODOLOGY
Design
The ecological survey described in this report was con
ducted from 1977 through 1979. The region of the river sur
veyed extends from Spanish Lookout Ferry, in the Cayo
District, to Belize City. During each of these years, the
river was investigated for several months, generally from
May through August. This period coincided with the sequence
of the wet and dry seasons that the country of Belize
experiences.
Eight stations were established along the designated
length of the river, as shown in Figure 3. The stations
chosen by the investigator were selected partly because they
are ordinarily accessible even during the wet season when
road conditions tend to deteriorate rapidly.
Stations 1 and 2 are located in Belize City. This city
is the largest urban center of the country. Several indus
tries are located about a mile up-river from these two sta
tions. It is common knowledge that industrial wastes and
raw sewage are discharged into the river in this region.
Station 3 is located some 15 miles west of Belize City
and is near to Burrell Boom Ferry. The village of Burrell
39
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. O City Belize N Bermudic 35 3 0 Labouring 25 '•Roaring Creek 20 15 10 Fig. 3.— Station numbers and locations along the Belize River. 5 Pine Ridge Scale: /500,0001 0
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 41
Boom is a little over a mile up-river. There is little
industrial activity in this region. Some of the villagers
do small-scale farming, but the majority commute to Belize
City and other areas for employment.
Station 4 is located about 7 miles west of Burrell Boom,
near the village of Bermudian Landing. There is some agri
cultural and livestock activity in the region, but these are
all small-scale operations. There is a large rice-farming
operation 10 miles up-stream from the station site. Aerial
spraying is part of the operation, and this has caused some
complaints from small farmers who maintain that the spraying
contaminates the river water.
Station 5 is near the village of Never Delay. The few
people in the region are involved mainly in subsistence
farming. There is little industrial activity in the region.
However, about 5 miles up-river there is a large livestock
farm, Little Orange Walk.
Station 5 is about 5 miles up-river from the previous
station. It is immediately down-river from the village of
Roaring Creek. The recently established capital city,
Belmopan, is located about 2 miles south of this station.
The village of Roaring Creek serves as a main, terminal in
the highway transportation system. There is little agricul
tural or industrial activity in the immediate vicinity of
the station.
Station 7 is near the village of Teakettle. The people
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in this sparsely populated region are generally involved in
subsistence farming.
Station 8 is located between the communities of Central
Farm and Spanish Lookout. The former is the national
research center of the Belize government for both agricul
tural and animal husbandry. Spanish Lookout is a Mennonite
community that is involved in extensive agricultural
activity.
Table 2 lists the approximate populations in the afore
mentioned station sites.
TABLE 2.— Station Number, Name, and Population Data for Vicinity of Each Station, Based on Census of 1970
Number Station Name Population
1 Swing Bridge, Belize City 40,000 2 Belcan Bridge, Belize City 40,000 3 Burrell Boom Ferry 1,500 4 Bermudian Landing 800 5 Never Delay 400 6 Roaring Creek 6,000 7 Teakettle 700 8 Spanish Lookout 1,300
The river was sampled from June through August of 1977,
and from May through August of 1978. During 1979, the sam-
pling period began in the latter part of April and extended
through the latter part of July.
During the periods of non-flooding, the samples were
taken from as near the center of the river as possible.
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During flood conditions, water samples were taken closer to
the river banks. This procedure was adopted for safety
reasons. In both situations, the samples were taken at a
depth of about 2 feet. Stations 4, 5, and 7 were not sampled
as often as the other stations, the reason being that heavy
rains had led to deterioration of the roads leading to these
stations.
The equipment used for collecting water samples was a
2.1-liter Kemmerer Water Sampler. The samples were analyzed
for acidity, free and total; alkalinity; carbon dioxide;
chloride; chlorine; chromate, sodium; chromium, hexavelent;
copper; fluoride; iron; manganese; nitrogen, nitrite and
nitrate; dissolved oxygen; pH; phosphate, ortho and meta;
silica; sulfate; and turbidity. The samples were also tested
periodically for the presence of detergents. Microbial cul
tures were made to determine quantitatively the presence of
yeast/mold, total bacteria, and total coliform. Benthic-
sampling collection involved the use of the Peterson Dredge,
and a plankton tow net (No. 24) was used to collect the
plankton samples. Interviews with some members of the com
munity in the vicinity of each particular station were con
ducted to determine the qualitative character of the
nektonic fauna.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 44
Methodology
Chemical Parameter
The chemical composition of the water samples was deter
mined using the standard procedures outlined in the manual
for the Hac.h-DR/1 portable field kit. The samples were anal
yzed colorimetrically using a Hach Chemical Company Field
Test kit, model DR/1 Portable Colorimeter/pH Meter.
Acidity. Acidity was determined by titration of the
water sample with 0.IN sodium hydroxide in the presence of
an indicator. The indicator was bromoresol green-methyl
red. The results of the acidity measurements were reported
as mg/1.
Alkalinity. Measurement of alkalinity was accomplished
by direct titration of the water sample with 0.2N sulfuric
acid in the presence of phenolphthalein. The results were
reported as mg/1 of calcium carbonate.
Carbon dioxide. The quantitative determination of
carbon dioxide was carried out by direct titration of the
water sample with 0.0227N sodium hydroxide, using phenolph
thalein as an indicator. The sodium hydroxide combines with
carbonic acid to form sodium bicarbonate and water. Once
all the carbonic acid has been neutralized, the hydroxide
ionizes the phenolphthalein present and converts it from a
clear to a pink color. Results were reported as mg/1.
Chlorine. The DPD compound was used to detect the
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presence of chlorine. If bromine is present, it may also
react with the compound. Results were reported as mg/1.
Chlorides. Chloride analysis was carried out using
mercuric nitrate as a titrant and diphenylcarbazone as the
indicator. Results were reported as mg/1.
Chromium, sodium. Direct measurements were carried out
on the original water samples. Alkaline solutions of sodium
chromate give a yellow color. The intensity of the color is
directly proportional to the amount of sodium chromate pres
ent. Results were reported as mg/1.
Chromium, hexavalent. Hexavalent chromium was deter
mined using 1,5-diphenylcarbohydrazide. The addition of
this compound to the water sample forms a reddish-purple
color whose intensity is in direct proportion to the amount
of chromium present; color intensity indicates the chromium
concentration. Results were reported as mg/1.
Copper. Copper was detected by the quantitative reac
tion of 2,2-biquinoline-4,4-dicarboxylic acid with cuprous
ion. This method is referred to as the Bicinchoninate
method. Results were reported as mg/1.
Fluoride. Fluoride was measured using the SPADNS method
that involves the reaction of fluoride with a- dark-red zir
conium dye. The fluoride combines with part of the zirconium
to form a colorless zirconium-fluoride complex with the
effect of bleaching the color in an amount proportional to
the fluoride concentration. The color intensity of the
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resultant treated water is measured colorimetrically.
Results were reported as mg/1.
Hardness, total. The amount of calcium and magnesium
present in a sample of water is usually referred to as the
total water hardness and is expressed as mg/1 calcium car
bonate. The method used to determine the concentration of
total hardness involved titration with ethylenediethyl-
tetraacetic acid (EDTA) in the presence of Calmagite as
indicator.
Hardness, calcium. Calcium hardness was determined
quantitatively by direct titration of the water sample with
EDTA in the presence of CalVer II Calcium Indicator. Prior
to the titration procedure, the sample was made alkaline
with KOH to precipitate magnesium. Results were reported
as mg/1.
Iron. Iron (ferrous state) was measured using the
quantitative reaction between the ferrous iron with 1,10-
phenanthroline. Results obtained were reported as mg/1.
Manganese. The quantity of this element was determined
by periodate oxidation of an acidified sample. Results were
reported in terms of mg/1.
Nitrate. The analysis of nitrates involved their
reduction to nitrites with cadmium metal and the reaction
of the nitrite ion with sulfanilic acid. This leads to the
formation of an intermediate diazonium salt that, when
treated with gentisic acid, forms an amber-colored compound
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directly proportional to the nitrate concentration of the
water sample. Measurement of the color intensity gives an
indication of the nitrate present in the water. Results
were expressed as mg/1 .
Nitrites. The method involved the reaction of the
nitrite with sulfanilic acid to form an intermediate salt.
This salt reacts with chromotropic acid to produce a red-
orange complex. Colorimetric determination of the color
change that resulted from the reaction was then carried out.
The readings derived were expressed as mg/1.
Dissolved oxygen. The determination of dissolved oxygen
was accomplished by the reaction of oxygen with manganese
and further reduction of the manganese complex. Phenylarsine
was used as a titrant in the final step of the procedure.
Results were reported as mg/1.
pH. The pH of the water sample was determined directly
by immersion of a pH electrode probe in the sample. Results
were reported in terms of pH values.
Phosphate. The phosphates are generally grouped into
three categories: orthophosphate, metaphosphate, and
organically bound phosphate. Both orthophosphate and meta
phosphate concentrations were determined in this investiga
tion. Orthophosphate determination involved reacting acidic
ammonium molybdate with orthophosphate to produce a yellow
phosphomolybdate complex. Further reduction of the yellow
complex by ascorbic acid gave an intense blue color. The
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color intensity was measured colorimetrically, and the
results were reported as mg/1. To determine metaphosphate,
a total inorganic phosphate test was first carried out. The
orthophosphate reading was subtracted from the inorganic
phosphate reading. Results were reported as mg/1.
Silica. The method used in determining the silica con
centration is the Silicomolybdate method. It involves the
reaction of ammonium molybdate with silica and phosphate that
forms a yellow color. The addition of citric acid destroys
the phosphomolybdate acid complex, but not the silicomolyb
date acid complex. The remaining yellow color is then mea
sured with a colorimeter. Results were given as mg/1.
Sulfate. The quantitative determination of sulfate was
accomplished with the SulfaVer method. The procedure
involves the precipitation of barium sulfate with barium
chloride. After precipitation, the suspended sulfate was
measured photometrically and reported as mg/1.
Sulfide, hydrogen. The concentration of dissolved
hydrogen sulfide was carried out by the lead sulfide method.
The water sample is treated with sodium bicarbonate, and the
released gas reacts with a chemically treated disc. The
resultant color change of the disc was then related directly
to the hydrogen sulfide concentration and reported as mg/1.
Turbidity. Turbidity results from the suspension of
clay, silt, and other finely divided organic and inorganic
matter. The turbidity test measured an optical property of
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the water sample. The property measured results from the
scattering and absorption of light by the particulate matter
present. Results were reported as Formazin Turbidity Units
(FTU1 s) .
Benthological Parameter
Because of the substrate diversity of the Belize River,
a Peterson Dredge was used to collect benthic samples. This
equipment allows the taking of samples on hard bottoms such
as sand, gravel, marl, and clay combinations.
Immediately after the samples were collected, they were
sieved with a No. 2 0 mesh net, thus removing the bulk of the
sediment and facilitating the harvesting of the benthic
organisms. The organisms collected were then placed in
labeled vials (date and station number) containing 70-percent
ethanol as a preservative. The vials were flown back to
Western Michigan University, Kalamazoo, where each organism
was identified and counted. Numerous references were used
in the identification process (Chu, 1949; Edmondson, 1959;
Mason, 1968; Pennak, 1978; Usinger, 1956).
When opened, the dredge covers a sampling area of 1
square foot and depending on the substrate may sink several
centimeters. Given the area the dredge covers and the depth
to which it sinks, one can determine the volume of substrate
dredged and relate the calculated volume to the number of
benthic organisms identified. Because of the inherent
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difficulty in determining the biting depth of the dredge,
the results were reported as number of organisms per square
foot of surface.
The percentage composition of major taxonomic groups
at each station was determined.
Planktonic Parameter
Plankton samples were taken each time the stations were
visited. A 24-mesh plankton net with a ring diameter of
10 cm was submerged just below the surface and kept there
for a 2-minute interval. A 15-ml vial attached to the end
of the net was used to collect and concentrate the plankton
flowing into the net. Given the circumference of the ring,
the time the net was submerged, and the velocity of the
water, the volume of water passing through the net can be
calculated. After the sampling period, the net was withdrawn
from the water and the vials were removed, sealed, and
labeled.
The samples were processed as soon as possible after
collection. In most cases, this occurred within a 3-hour
period. In cases in which it was anticipated that micro
scopic examination of the sample would be delayed for more
than 3 hours, the sample was treated with 5 ml of a preserva
tive mixture that consisted of 5 percent formalin, 5 percent
glacial acetic acid, and 90 percent ethyl alcohol.
In carrying out the microscopic examination, the samples
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were inverted several times to ensure proper mixing of the
contents. A portion was then taken from the vial with a
5-ml pipette and added to a Sedgewick-Rafter counting chamber
that measured 50 mm long by 20 mm wide by 1 mm deep, for a
total volume of 1 ml. Care was taken to avoid the formation
of air bubbles in the chamber after the cover slip was placed
over it. When air bubbles did form, the cell contents were
disregarded and a new one prepared.
Using the 20x objective of a monocular Bausch and Lomb
microscope, the contents of the counting chamber, after it
had been allowed to sit for about 10 minutes, were examined
to determine the quantity and quality of the plankton
(Drouet, 1959; Edmondson, 1959; Lackey, 1959; Noland, 1959;
Thompson, 1959). The lack of a whipple grid made it neces
sary for the entire contents of the cell to be counted.
Three 1-ml aliquots were examined and the number of organisms
in each were totaled. The data from the replicate samples
were averaged and the results reported as the number of
individuals per ml. The relative percentages of each group
of organisms were also determined. The mean diversity and
the equitability were also determined for each station using
the formulae described below (Weber, 1973)':
5 = — --| 9-2-9'(H log10 N - lo r^)
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where N = the total number of individuals at the designated station over the complete period of study
n. = the total number of individuals in the ith species
s' = a tabulated value
s = the number of taxa in the sample.
Microbiologic Parameter
Three general types of cultures were made from the
water samples taken at each station. These cultures include
total bacteria, total coliform, and yeast/mold. The water
samples were collected originally in glass bottles that,
along with their caps, had been sterilized by boiling.
As soon as possible, the cultures were prepared with
the use of the Environmental Microbiology Experiment Kit
from the Millipore Company. The procedures employed were
those found in the accompanying manual, Millipore Experiments
in Microbiology.
Anticipating high values in the counts of total bacteria
and total coliform, a 1:10 dilution (1 ml of sample asepti-
cally pipetted into 9 ml of sterile buffer) was part of the
standard procedure. The buffer was prepared in the following
manner:
Stock Solution 1 : Dissolve 17.0 gm of potassium dihydrogen phosphate (KH2PO4 ) in 250 ml of deminer alized water. Adjust the pH to 7.2 with IN NaCH. Dilute to 500 ml with demineralized water to pro duce 500 ml of stock buffer solution.
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Stock Solution 2: Dissolve 25.0 gm of magnesium sulfate (MgS047H 20) in 500 ml of demineralized water.
Working Solution: Add 1.25 ml of Stock Solution 1 and 500 ml of Stock Solution 2 and dilute to 1 liter with demineralized water.
The buffer was sterilized using the membrane filter tech
nique. At Stations 1 and 2, a 1:100 dilution was used at
all times. This dilution was accomplished by taking a 1-ml
aliquot from a 1:10 dilution and mixing it thoroughly in
9 ml of sterile buffer.
In most instances, sterilization of the equipment was
accomplished by boiling, but in a few cases it was done by
total submersion of the aparatus to be used in 7 0 percent
ethyl alcohol for 3-5 minutes, as is recommended in the
manual.
Every time a station was visited, enough sample material
was taken to carry out two total bacterial cultures, two
coliform cultures, and two yeast/mold cultures. The data
obtained were averaged and results reported as number of
colonies per 100 ml.
Nektonic Parameter
The collection of quantitative data on the nektonic
biota of a riparian ecosystem is a tremendous task, involving
numerous pieces of equipment and techniques. Consequently,
in this investigation, only qualitative data were sought.
This data collection involved personal communication with
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members of the community in the vicinity of each particular
station. They were asked for a list of the various forms
of nektonic organisms that were present in the river. These
data were reported as a listing of such organisms.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER IV
RESULTS AND DISCUSSION
Chemical Parameter
After the raw data had been collected for the various
chemical parameters, mean dry- and wet-season levels were
determined along with the standard deviation for each param
eter during both seasons. These data are summarized in
Tables 3-10.
Acidity
Acidity of natural waters is generally very low unless
strongly acidic industrial waters have entered it. Further
more, it has been pointed out that natural waters high in
acidity are indicative of low calcium content.
From the analyses carried out, it was observed that the
acidity levels at all stations during both seasons measured
.0 mg/1 (Tables 3-10). This indicates that this water is
not of a corrosive nature and that its calcium content
should be high.
Alkalinity
Natural surface and well waters usually contain less
alkalinity (measured as calcium carbonate) than waters into
55
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 56 TABLE 3.— Comparison of Metal and Cation Levels in Belize River at Station 1 (data given as mean [mg/l]± one standard deviation)
Dry Season Wet Season
M SD M SD
Acidity: free .00 .00 .00 .00 total .00 .00 .00 .00 Alkalinity 2.5 x 102 18 2 .1 x 102 16 Carbon Dioxide 1.7 x 1 0 2 30 96 17 Chloride 2.0 x103 4.3 x 103 7.8 x l O 2 1.1 xlO2 Chlorine 1.2 .15 .07 .02 CM O Chromate, sodium 1.2 x 102 19 X 50 Chromate, hexavalent .05 .01 .03 .01 Cooper .19 .04 .09 .01 Fluoride 1.7 .41 1.9 .66 Hardness: calcium 3.1xio2 1 .3 x 103 2.5 x 102 4 . 3 x 10 total 1.3 x 1 0 3 1.2 x 103 3.8 x 1 0 2 8 . 3 x 10 Hydrogen sulfide .26 .15 .25 .14 Iron (ferrous) .22 •.04 .23 .04 Manganese .21 .02 .13 .02 Nitrogen: nitrate 59 8 77 7.0 nitrite .48 .11 .30 .09 Oxygen, dissolved 4 .8 3 1 DHa 6.5 .15 6.5 .25 Phosphate: ortho 2.1 .67 2.8 .85 meta .98 .24 1.3 .41 Silica 1.2 x 103 l.lxlO2 1 .1 x 102 97 Sulfate 2.7 x 102 57 3.2 x 102 54
aGiven as pH units.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 57 TABLE 4. — Comparison of Metal and Cation Levels in Belize River at Station 2 (data given as mean [mg/1]± one standard deviation)
Dry Season Wet Season Paramter M SD M SD
Acidity: free .00 .00 .00 .00 total .00 .00 .00 .00 Alkalinity 2.1x102 34 2.4 x 102 18 Carbon Dioxide 1.7 x102 23 1.3 x 102 33 Chloride 1.5 x 103 4.0 xlO2 6.8 x 102 34 Chlorine 1.1 .19 .57 .02 Chromate, sodium 1.3 x102 15 1.7 x 102 54 Chromium, hexavalent .04 .01 .03 .01 Cooper .16 .04 .04 .01 Fluoride 1.3 .18 1.2 .04 Hardenss: calcium 3.2 x 102 1.3 xlO2 2 .1 x 102 25 total 1 .1 x 103 3.6 xio2 3.5 x 1 0 2 55 Hydrogen sulfide .16 .09 .10 .11 Iron (ferrous) .23 .05 .21 .04 Manganese .08 .02 . .05 .01 Nitrogen: nitrate 48 6.0 64 7.0 nitrite .41 .07 .24 .09 Oxygen, dissolved 4 .8 4 1
pHa 7.1 .21 6.9 .15 Phosphate: ortho 2.0 .75 2.7 .67 meta .89 .52 1.1 .39 Silica 1.2 x 103 85 8.2 x 103 l.lx 102 Sulfate 2.2 x 102 32 2.7 x 1 0 2 43
aGiven as pH units.
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TABLE 5.— Comparison of Metal and Cation Levels in Belize River at Station 3 (data given as mean [mg/] ± one standard deviation)
Dry Season Wet Season Parameter M SD M SD
Acidity: free .00 .00 .00 .00 total .00 .00 .00 .00 Alkalinity 1.6 xlO2 13 1.3 x 102 18 Carbon dioxide 19 4.7 16 2.9 Chloride 48 11 43 9.0 Chlorine .19 .04 .09 .02 Chromate, sodium 62 13. 14 4.1 Chromiu, hexavalent .03 .01 .02 .01 Cooper .05 .01 .03 .01 Fluoride 1.1 .19 1.3 .23 Hardness: calcium 1.3 x l O 2 50 69 11 total 2.5 x l O 2 18 75 75 Hydrogen sulfide .10 .11 .10 .11 Iron (ferrous) .17 .02 .18 .05 Manganese .07 .05 .07 .02 Nitrogen: nitrate 38 6.0 34 5.3 nitrite .09 .05 .07 .02 Oxygen, dissolved 7 .6 7 .8 pHa 7.2 .14 7.1 .36 Phosphate:: ortho 2.9 .72 3.0 .78 meta 1.6 .45 1.4 .72 Silica 1.5 x l O 2 26 4.2 x 102 30 Sulfate 1.5 x l O 2 25 1.4 x IQ2 28
aGiven as pH units.
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TABLE 6.— Comparison of Metal and Cation Levels in Belize River at Station 4 (data given as mean [mg/1] ± one standard deviation)
Dry Season Wet Season Parameter M SD MSD
Acidity: free .00 .00 .00 .00 total .00 .00 .00 .00 Alkalinity 1.4 x 102 14 1.3 x 102 30 Carbon dioxide 20 3.1 12 3.1 Chloride 18 3.4 11 3.9 Chlorine .07 .02 .05 .01 Chromate, sodium 18 4.7 15 3.1 Chromium, hexavalent .04 .01 .02 .01 Cooper .14 .03 .12 .02 Fluoride .90 .14 1.4 .27 t>J H Hardness: calcium to o 45 65 13 total 2.2 x if)2 73 1 . 6 x l O 2 36 Hydrogen sulfide .10 .10 .10 .10 Iron (ferrous) .14 .04 .16 .03 Manganese .06 .01 .06 .01
Nitrogen: nitrate 42 to 47 7.6 nitrite .07 .01 .09 .04 Oxygen, dissolved 7 .6 7 1 pHa 7.2 .29 6.8 .27 Phosphate: ortho 3.1 .78 3.4 .79 meta 1.6 .50 1.9 .59 Silica 31 7.4 40 7.0 Sulfate 1.3 x 102 22 24
aGiven as pH units.
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TABLE 7.— Comparison of Metal and Cation Levels in Belize River at Station 5 (data given as mean (mg/1] ± one standard deviation
Dry Season Wet Season PHr&iriGtiGr MSD MSD
Acidity: free .00 .00 .00 .00 total .00 .00 .00 .00 Alkalinity 1.6 x 102 18 1 .,4 x io2 15 Carbon Dioxide 25 5.8 19 3.1 Chloride 29 15 21 5.8 Chlorine .06 .01 .06 .02 Chromate, sodium 37 7.6 24 11 Chromium, hexava1ent .03 .01 .02 .01 Cooper .14 .04 .13 .04 Fluoride 1.4 .21 1.3 .21 ; n X Hardness: calcium o 35 91 13 i i total 2.8 x 102 67 1 ,.7 x 102 30 Hydrogen sulfide .10 .10 .10 .10 Iron (ferrous) .13 .03 .15 .01 Manganese .06 .01 .10 .20 Nitrogen: nitrate 41 7.5 49 6.7 nitrite .11 .05 .05 .01 Oxygen, dissolved 8 .8 8 1
p h s 7.3 .10 7.3 .02 Phosphate: ortho 2.7 .56 3.2 .67 meta 1.10 .59 1.4 .47 CN CO Silica 1.3 x 102 30 28 Sulfate 82 3 38 5.5
aGiven as pH units.
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TABLE 8.— Comparison of Metal and Cation Levels in Belize River at Station 6 (data given as mean [mg/1] ± one standard deviation)
Dry Season Wet Season Parameter M SD M SD
Acidity: free .00 .00 .00 .00 total .00 .00 .00 .00 Alkalinity 1 .7 x 102 17 1 ..6 x if)2 16 Carbon dioxide 16 3.0 22.37 8.8 Chloride 25 3.9 14 4.4 Chlorine .07 .02 .07 .03 Chromate, sodium 42 6.2 12 3.8 Chromium, hexavalent .03 .01 .02 .01 Cooper .08 .01 .08 .01 Fluoride 1.1 .18 1.1 .35 Hardness: calcium 1 .3 x 102 18 98 26 total 1 .9 x 102 47 1 .5 x 10 32 Hydrogen sulfide .10 .10 .10 .10 Iron (ferrous) .12 .02 .09 .01 Manganese .05 .02 .08 .02 Nitrogen: nitrate 44 7.4 52 6.4 nitrite .09 .04 .07 .03 Oxygen, dissolved 7.5 .55 8.0 1.0 7.2 .64 6.9 .25 Phosphate: ortho 2.8 .73 3.00 .66 meta 1.2 .39 1.3 .37 Silica 20 7.5 23 4.8 Sulfate 16 6.5 16 2.9
aGiven as pH units.
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TABLE 9.— Comparison of Metal and Cation Levels in Belize River at Station 7 (data given as mean [mg/1] ± one standard deviation)
Dry Season Wet Season Parameter MSDMSD
Acidity: free .00 .00 .00 .00 total .00 .00 .00 .00 Alkalinity 1.5 x l O 2 16 1.2 x 102 10.40 Carbon dioxide 18 5.8 11 3.0 Chloride 14 3.5 9.6 3.4 Chlorine .05 .01 .04 .01 Chromate, sodium 27 12 21 9.0 Chromium, hexavalent .02 .01 .02 .01 Cooper .10 .05 .18 .03 Fluoride 1.3 .17 .60 .13 Hardness: calcium 1.2 x 102 12 1.0 x 102 26 total 2.2 x 102 29 1.4 x 102 37 Hydrogen sulfide .10 .10 .10 .10 Iron (ferrous) .13 .03 .11 .04 Manganese .12 .02 .09 .03 Nitrogen: nitrate 41 8.6 58 8.8 nitrite .13 .04 .06 .02 Oxygen, dissolved 8 .8 8 1 pH3 7.3 .13 7.2 .22 Phosphate: ortho 2.9 .63 3.4 .52 1 H meta 1.6 .69 00 .48 Silica 46 11 74 15 00 00 Sulfate 27 51 16
aGiven as pH units.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE 10.— Comparison of Metal and Cation Levels in Belize River at Station 8 (data given as mean [mg/1] ± one standard deviation)
Dry Season Wet Season Parameter M SD M SD
Acidity: free .00 .00 .00 .00 total .00 .00 .00 .00 Alkalinity 1.7 x 1 0 2 12 1.4 x 102 13.25 Carbon dioxide 15 3.3 33.75 7.5 Chloride 19 6.2 14.00 5.0 Chlorine .04 .01 .04 .01 Chromate, sodium 26 11 20 8.4 Chromium,hexavalent .03 .01 .02 .01 Cooper .09 .01 .04 .02 Fluoride 1.20 .20 .30 .11 Hardness: clacium 1.2 x 102 13 86 20 total 2.1x102 53 1.5 x 102 23.31 Hydrogen sulfide .10 .10 .10 .10 Iron (ferrous) .12 .01 .11 .04 Manganese .10 .01 .08 .02 Nitrogen: nitrate 45 7.1 57 9.8 nitrite .15 .06 .11 .06 Oxygen, dissolved 8 .7 7 .6 pHa 7.1 .16 7.0 .27 Phosphate: ortho 3.1 .70 3.4 .62 meta 1.7 .51 1.7 .44 Silica 33 5.3 62 16 Sulfate 21 2.9 51 9.1
aGiven as pH units.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 64
which sewage or waste water is dumped. Generally high levels
of alkalinity indicate the presence of a strongly alkaline
industrial waste. The alkalinity levels at the eight sta
tions studied indicate that during the dry season the levels
are higher than they are during the wet season (Tables 3-10).
The highest levels were measured during both seasons at
Stations 1 and 2. Industrial waste and raw sewage may well
be the causative agents for these high values. It was worth
noting that at Station 2 there was a higher level of alka
linity during the wet season. This increase may be attrib
uted to the alleged dumping of industrial wastes by the
industries located above this station.
Among the other stations, high levels of alkalinity were
obtained at Stations 6 and 8 during the wet season. Runoff
introducing both industrial and human waste may be the con
tributing factor for the observed increases. This possible
introduction of waste, in a similar manner, may affect the
alkalinity level of Station 5. The decreased level observed
at Station 4 could well have resulted from a dilution effect
produced by the tributaries entering the main stream between
these two stations.
Carbon Dioxide
Carbon dioxide is always present in natural waters. It
occurs as a product of aerobic and anaerobic metabolism of
organic matter. Its presence is not harmful to humans;
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however, it has been suggested that carbon dioxide concen
trations exceeding 10 mg/1 may be fatal to many types of
fresh-water fish (Hach, 1977) . With sufficient plant pro
ductivity, high concentrations would be decreased and con
tinuous fish growth would be promoted.
The data collected at Stations 1 and 2 during both
seasons indicate extremely high levels of carbon dioxide
(Tables 3-4). These high levels can be accounted for
indirectly by the discharge of organic effluents into the
river around the regions of these two stations. The organic
effluents stimulate microbial activity leading to the pro
duction of great amounts of carbon dioxide.
At the other stations, the levels of carbon dioxide
were generally around 20 mg/1 (Tables 5-10). Although this
level is higher than the level considered harmful to some
fresh-water fish life, no major problem appeared to arise.
During the wet season, Station 6 showed a reading of slightly
more than 20 mg/1 carbon dioxide. One can safely assume that
runoff during this season introduced organic effluents that
produced the observed increase. At Station 8 during the
same season, a mean value of 33 mg/1 was obtained. This high
value may result from the introduction of agricultural and
livestock waste produced in the region. The sharp decrease
noted at Station 7 could have resulted from a dilution effect
great enough to mask the activities of Station 8. Dilution
effects could also explain the decreases in the sparsely
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populated regions of Stations 4 and 5. Finally, the slight
increase at Station 3 may be attributed to human activities
in that region.
Dry season measurements were generally consistent, with
the exception of Station 5.
Chloride
Chlorides are always present as a component of potable
water. When present as salts of calcium or magnesium, the
chloride level may exceed 1,000 mg/1. Although water quality
standards may vary from one country to another, it is gener
ally accepted that chloride concentrations of 250 mg/1 in
drinking water are the maximum allowable (EPA, 1973). As
with the preceding chemical factors, chloride values were
higher in the dry season than they were in the wet season
(Tables 3-10). The wet-season low values can be attributed
to the dilution effect resulting from precipitation and
runoff.
Stations 1 and 2 revealed the highest mean chloride
levels during both seasons. This situation can be explained
by the intrusion of ocean water into the region of these
two stations.
The chloride levels for Stations 3-8 were below 50 mg/1
during both seasons. Stations 4-8 showed levels in the range
of 30 mg/1 and 15 mg/1. High levels in this range occurred
at Stations 5 and 6 during the wet season.
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Chlorine
Chlorine is often added to swimming pools, sewage
treatment plant effluents, and drinking water supplies to
destroy bacteria. It is not considered a naturally occurring
component of streams and rivers.
The data obtained for chlorine levels at all stations
during both seasons showed total chlorine levels to be below
1.3 mg/1 (Tables 3-10). During the dry season, levels of
chlorine were generally higher. They showed a decline as
one proceeded from Station 1 toward Station 8. A slight
increase was observed at Station 6.
During the wet season, the chlorine levels were at or
below the .09 mg/1 level, except for Station 2 where a marked
increase was registered. One may assume that results from
waste discharged into the river around this region.
Chromium, Sodium
The introduction of sodium chromate to natural waters
is usually brought about by the input of industrial wastes.
This compound is added to cooling water to inhibit corrosion
of metal pipes and fittings.
Only at Stations 1 and 2 did sodium chromate readings
exceed the 100 mg/1 level. All other values during both
seasons tended to fall within the 45- to 10-mg/l range
(Tables 3-10), with the exception of the dry season value of
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Station 3 which was around 62 mg/1. No apparent reason is
evident for the increased value at this station. The
increased values at Stations 5 and 6 may be the product of
urban and industrial activities around Station 6.
Chromium, Hexavalent
Hexavalent chromium generally indicates the presence of
industrial wastes, and concentrations greater than .05 mg/1
are considered sufficient reason to avoid using such water
supplies (EPA, 1973).
The water samples from the stations studied revealed
that a mean value of .05 mg/1 level was obtained only at
Station 1 during the wet season. This high value most likely
results from industrial wastes being emptied into the river
farther up-stream. Stations 2 and 4 both show levels of
.04 mg/1 and, while one may expect such a mean value to occur
at Station 2, there is no apparent reason for its occurrence
at Station 4. All other mean values fell within the .03 mg/1
level and the .02 mg/1 level (Tables 3-10). This range may
be considered safe and the water usable.
Copper
Copper may at times be present in natural waters. It
may also occur in industrial wastes and wastewater discharges.
Although copper is not generally considered a health hazard,
concentrations above 3.0 mg/1 copper are sufficient reasons
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for avoiding the use of such water. For public drinking
water supplies, a maximal level of 1.0 mg/1 copper is
recommended (EPA, 1973).
Analyses of water samples from all eight stations during
both seasons show the copper levels fall within the range of
.19 mg/1 and .03 mg/1 (Tables 3-10). The average concentra
tion of copper in potable water is .03 mg/1 and occasionally
will range up to .06 mg/1 in natural waters from some areas.
Thus, from the standpoint of copper concentrations, the water
of the Belize River is fairly safe. Although variations
among the mean values of the stations did occur, such varia
tions are well within the limits of allowable concentrations.
Fluoride
Many waterways have fluoride occurring naturally, and
a level of 1.0 mg/1 is usually maintained in public drinking
water (EPA, 1973).
From the data obtained by analyses, dry-season levels
at all stations were above the 1.0 mg/1 level (Tables 3-10),
with the exception of Station 4 where there was a level of
.9 mg/1. This low level may be attributed to a dilution
effect produced by the flow of water from tributaries enter
ing the river above this station.
The wet-season mean values also showed levels greater
than 1.0 mg/1 at Stations 1-6. Stations 7 and 8 during the
wet season had levels of .6 mg/1 and .3 mg/1, respectively.
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Although the wet-season fluoride levels ranged from 2.0 mg/1
to .3 mg/1, these levels are not considered physiologically
harmful. Dilution effect and introduction of fluoride
through runoff may well account for the wide range.
The dry-season levels ranged between 1.7 mg/1 and .9
mg/1. These values are within allowable limits. Thus, it
appears that the fluoride content of the water samples from
the various stations indicates that the river water is
acceptable.
Hardness, Total
The amount of calcium and magnesium present in a sample
of water is usually referred to as the total hardness of the
water. Levels in the region of 500 mg/1 total hardness make
water undesirable for domestic use, and most drinking water
supplies have a mean of about 250 mg/1 (EPA, 1973).
The mean dry-season levels of total hardness were
observed to be greater at all stations than the mean wet-
season values (Tables 3-10). The range of the levels for
all stations fell between 1,365 mg/1 at Station 1 and 196
mg/1 at Station 6. The levels of total hardness were
markedly different between Stations 1 and 2 and the other
stations. The levels that were above the 1,000 mg/1 level
at the first two stations may be attributed to the intrusion
of sea water into the region where these two stations are
located. At all other stations, levels fell below 300 mg/1.
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Even lower levels were obtained in the wet season. Thus,
it seems that the water may be used for domestic purposes
and for drinking without treatment for this parameter.
Calcium Hardness
Excessive amounts of calcium in water supplies are
generally considered undesirable for domestic and industrial
uses. One of the main problems of excess calcium is that
the calcium compounds tend to precipitate out of solution,
causing blockage of pipes.
As has been generally observed with the other chemical
factors, calcium levels were generally higher in the dry
season. During the wet season, levels across the eight sta
tions ranged from a high of 316 mg/1 calcium hardness at
Station 2 to a low of 118 mg/1 calcium hardness at Station 4
(Tables 3-10). A marked increase was noted at Station 5
during this season. The reasons for this increase, however,
are not clear.
During the wet season, the calcium hardness levels
ranged from 255 mg/1 at Station 1 to 65 mg/1 at Station 4.
The higher levels obtained for Stations 3-8 during the
dry season may be attributed to enrichment from ground
sources. The soil in these regions is comprised primarily
of clay and limestone. The lower wet-season levels may have
been caused by dilution through rainfall precipitation.
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Hydrogen Sulfide
Sulfides are toxic by-products resulting from bacterial
decomposition. They are usually found in sewage and indus
trial wastes.
Data obtained from analyses of water samples (Tables
3-10) failed to reveal any differences among the hydrogen
sulfide concentrations for Stations 3-8. This observation
applied for both seasons. At Stations 1 and 2, however, much
higher levels of hydrogen sulfide were detected. It is safe
to assume that these high levels are a direct product of
bacterial action on the organic and sewage effluents dis
charged into the river in the region of these two stations.
Iron
Iron compounds are found in natural waters usually in
minor amounts. Iron is generally present in the ferrous
state, which easily oxidizes to ferric or insoluble iron on
exposure to air. While usually present in minor amounts,
iron concentrations in natural waters may increase as a
result of the leaching or natural deposits, iron-bearing
industrial waste effluents, pickling operation effluents,
or acidic mine drainage.
The data collected reveals that during both seasons
there was a general decrease in iron levels as one proceeded
up-stream (Tables 3-10). No great differences were observed
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Station 6 showed a marked decline, however, during the wet
season. No apparent reason can be given for this decline.
Levels of ferrous iron in the wet season ranged from a high
of .23 mg/1 at Station 1 to a low of .08 mg/1 at Station 6 .
Dry-season levels ranged from .23 mg/1 at Station 2 to
a level of .12 mg/1 at Station 6. Water used in industrial
processes usually contains less than .2 mg/1 total iron.
Domestic water supplies containing more than .3 mg/1 total
iron are not generally used due to staining and taste con
siderations. Water samples obtained from Stations 3-8 show
concentrations of ferrous iron below the .2 mg/1 level.
Thus, the water may be considered suitable for domestic and
industrial use from the standpoint of its iron concentration.
Manganese
Manganese is a natural component of groundwater. In
natural water the level rarely exceeds 1.0 mg/1, but it is
generally thought that levels above .1 mg/1 are sufficient
grounds for not using the water. The maximal allowable man
ganese level in public water supplies is .05 mg/1 (EPA,
1973) .
Analyses of water samples gathered from the eight sta
tion sites (Tables 3-10) show that only at Station 2 did the
manganese level reach the .05 mg/1 level during the wet
season. All other station samples fell within the .06 mg/1
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level and the .13 mg/1 level. During the dry season, only
at Station 6 did the level fall to the .05 mg/1 level. The
highest level occurred at Station 1, where the mean manganese
concentration recorded was .21 mg/1. The level nearest to
the .05 mg/1 observed for Station 6 was .06 mg/1 at Station 5.
Thus, it seems that, when considering the water of the
Belize River as a domestic source, some care must be taken in
its use based on the observed manganese levels.
Nitrate
Nitrates are generally found as a component of natural
waters. Both bacterial action and other naturally occurring
phenomena contribute to the presence of nitrates in water.
High levels are generally indicative of biological wastes in
the final stages of stabilization or runoff from heavily
fertilized fields. Nitrate-rich effluents into rivers or
streams can lead to water quality degradation by encouraging
excessive algal growth. The maximal allowable nitrate level
in public drinking water supplies has been established at
45 mg/1 (EPA, 1973).
From the data collected (Tables 3-10) , it was noted that
both Stations 1 and 2 had levels over the maximum allowable.
In this region, raw sewage is discharged into the river and
thus accounts for the high levels of nitrates.
In general, wet-season levels of nitrates were higher
than those of the dry season, with the exception of Station 3
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where the dry-season level was about 4 mg/1 greater. During
the wet season, most of the levels were greater than the
maximal allowable limit. It is worth noting that Stations
7 and 8 registered rather high levels of nitrate. Evidently,
material from the fertilized fields in this agricultural
region and organic waste from livestock were introduced into
the river and contributed to the high values observed. The
drop in nitrate level at Station 6 may have been influenced
by the increased volume of water introduced by the Roaring
Creek stream into the river. A similar dilution effect may
have contributed to the decreases observed at the other
stations farther downstream.
Dry-season levels at Stations 3-8 were in the range of
4 5 mg/1 and 34 mg/1. These values are below the maximal
allowable limits in drinking water.
Nitrite
Nitrites are not generally found in surface water since
they tend to oxidize to nitrates. Their presence may indi
cate the existence of excessive industrial wastes or par
tially decomposed organic waste material. Public drinking
water supplies seldom have more nitrite than .1 mg/1 (EPA,
1973).
The data obtained from the determination of nitrite
levels (Tables 3-10) reveal that highest levels during both
seasons were obtained at Stations 1 and 2. The high levels
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are indicative of the highly organic effluent that enters
in this section of the river. All other stations had levels
that were in the .15 mg/1 and .05 mg/1 range.
During the wet season, Station 5 had the lowest mean
nitrite level, .05 mg/1. Station 8 had a level of .11 mg/1.
This high value may have been caused by the introduction of
livestock waste into the river. The same explanation can be
offered for the .15 mg/1 level recorded during the dry season
at this same station. Station 7 also had a high value during
the dry season. This value was probably the result of
up-stream activity. The other mean values were generally
below the .1 mg/1 level. No major seasonal differences were
noted for nitrites.
Dissolved Oxygen
Dissolved oxygen is one of the important components used
to determine the quality of natural waters. High levels of
dissolved oxygen are generally associated with fairly clean
waters. The predictive power of this parameter is supple
mented by the presence of a diversified biota.
The mean levels of dissolved oxygen were lowest at
Stations 1 and 2 (Tables 3-4). For both these stations, the
mean levels were below 4.5 mg/1 dissolved oxygen. At the
other stations (Tables 5-10) , the mean values for both sea
sons were generally between 7 mg/1 and 8 mg/1 dissolved
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. oxygen. Mean levels during the wet season were generally
higher. Perhaps the lower mean temperature and the faster
water movement during this period may have contributed to
the increase (Table 11). Conversely, higher temperatures
and slower water movement may have contributed to the lower
dry-season values.
TABLE 11.— Mean Values of Some Physical Factors of Belize River as They Occurred at All Stations During Both Seasons
Temperature Velocity Turbidity Color (C°) (m/sec) (FTU's ) (APHA1s) Station Wet Dry Wet Dry Wet Dry Wet Dry
1 27.5 29.3 .04 . 05 253 219 168 104 2 27. 3 30.2 .05 . 05 174 202 128 133 3 27.5 30.1 .10 . 07 74 66 58 41 4 23.2 26. 6 . 09 . 06 78 31 44 28 5 22.7 27.4 .08 . 04 89 41 55 29 6 23.1 29.0 .09 . 04 98 33 48 30 7 23.4 28.1 .09 . 07 80 30 70 32 8 22.8 28.6 .10 . 05 86 37 67 33
pH
Most natural waters are generally found to have a pH
in the range of 4.0 to 9.0. Other pH values than these can
be associated with industrial wastes and can be considered
harmful to the general biota of the water system.
The mean pH levels (Tables 3-10) show that Station 1
during both seasons was slightly acidic. At Station 7 the
mean pH level during the wet season was slightly acidic, but
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was slightly alkaline during the dry season. At the other
stations, mean acidic levels were noted twice during the wet
season. The locations showing this condition were Stations
4 and 6. At all other stations, mean pH levels for both
seasons were basic in nature.
Phosphate
The natural form in which phosphorus occurs in water is
primarily in the form of phosphates. A certain amount of
phosphate is essential to organisms in natural waters and is
often the limiting nutrient for growth. Too much phosphate
can lead to eutrophication of water bodies, especially if
great amounts of nitrates are present. Phosphates are intro
duced into the water from several sources. These include
agricultural fertilizer runoff, water treatment chemicals,
and biological wastes and residues. Meta phosphates are the
forms commonly used in treating water systems and boilers
and in detergent formulations. After being dissolved in
water, these are converted to orthophosphates at different
rates depending on factors such as temperature and pH.
The data gathered show that mean orthophosphate levels
were higher than metaphosphate levels at all stations for
both seasons (Tables 3-10). It is worth noting that high
levels of orthophosphate were recorded at Stations 4, 7, and
8. These stations are in close proximity to large agricul
tural operations or are not too far downstream from such
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operations. Station 4 is downstream from a major rice
plantation, and Station 7 is below the national agricultural
research station. Levels of orthophosphate were generally
lower in the first two stations. These phenomena were
observed to occur during both seasons.
Basically similar trends were noted with metaphosphate
occurrence. High levels were associated with Stations 4, 7,
and 8. It can be assumed that these high levels are pri
marily the product of agricultural fertilizer runoff.
Silica
Silica occurs naturally in most bodies of water and
exists as an oxide or as a silicate.
Mean values of silica concentrations show that there
were no consequential seasonal differences among the various
levels (Tables 3-10). However, during both seasons the mean
levels decreased appreciably as one proceeded up-stream.
Sulfate
Sulfates occur in natural waters in varying concentra
tions. Standard norms call for not more than 250 mg/1 of
sulfate in drinking water because of the cathartic action of
sulfate (EPA, 1973). Sulfates enter the water system by the
infiltration of mine waters and industrial effluents.
Measurements of mean levels of sulfate concentrations
during both seasons at all stations failed to show major
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differences between seasonal levels (Tables 3-10). Mean
values for Stations 1 and 2 were greater than 200 mg/1. The
mean values at the other stations were below 150 mg/1.
Benthological Parameter
One of the important parameters of fresh-water eco
systems is the presence of a benthic community. During this
investigation, seventy-two bottom samples were sieved and
the organisms in the sample collected. Identification of
these organisms was later carried out to the family level
only. Ninety-six bottom samples were treated similarly
during the wet season. Samples were taken only at Stations
3-8.
The identification indicated that ten major taxonomic
groups were present in the Belize River. These included
Tricoptera, Ephemeroptera, Odonata, Plecoptera, Neuroptera,
Diptera, Coleoptera, Hemiptera, Oligochaeta, and Gastropoda.
Four families of the Tricoptera order were present
(Figure 4). The predominant forms were members of the fam
ilies Hydropsychidae and Hydroptilidae. They were present
at virtually every station during the dry season, but showed
a limited wet-season distribution. The other two families—
Leptoceridae and Psychomyiidae— were present only in the dry
season.
The Ephemeroptera had the greatest number of representa
tive families (Figure 4). Of the nine families,
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Key: ***** Wet season ----- Dry season Station 3 4 5 6 7
TRICOPTERA
Hydropsychidae ***********
Hydroptilidae ******************
Leptoceridae
Psychomyiidae
EPHEMEROPTERA
Siphlonutidae
Tricorythidae ************************
Baetidae ******______
Heptageniidae ______
Ephemerellidae _
Leptophlebiidae ************
Caenidae
Ametropodidae ********
Fig. 4.— Occurrence of families of Tricoptera and Ephemeroptera at all stations during both seasons.
Tricorythidae was dominant and was present during both sea
sons. Although limited in their distribution among the sta
tions, members of the families Baetidae, Siphlonuridae, Lep-
tophlebidae, and Ametropodidae were also found during both
seasonal periods. The presence of Heptageniidae, Ephemerel
lidae, Ephemeridae, and Caenidae appeared to be restricted
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to the dry season only.
The order Diptera was represented by five families
(Figure 5). These families were Chironomidae, Heleidae,
Culicidae, Tipulidae, and Scimyzidae. Of these, only members
of the Chironomidae and the Heleidae were found during both
seasons.
Six families of the Coleoptera were encountered in the
Belize River during the course of this investigation (Figure
5). The families present were Elmidae, Hydroscaphidae,
Chelonaridae, Psephenidae, Curculionidae, and Helodidae.
Members of the Hydroscaphidae and the Curculionidae were
found during the dry season only. All the other families
were represented during both seasons.
The order Hemiptera was represented by five major fam
ilies (Figure 5). The most predominant forms were members
of the Naucoridae family, which was present during both
seasons. Three families— Mesoveliidae, Veliidae, and
Hebridae— were present in the dry season only. The family
Gerridae was present during both seasons, but showed a
limited distribution pattern.
Representatives of three other insect orders that were
present in the Belize River were Odonata, Plecoptera, and
Neuroptera (Figure 6).
Agrionidae and Gomphidae were the representative fam
ilies of the Odonata. The former was the more predominant
group. It was present at most of the stations during the
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Key: ***** wet season
----- Dry season Station 5 6
DIPTERA
Chironomidae ***********************
Heleidae ******************
Culicidae
Tipulidae
Scimyzidae
COLEOPTERA
Elmidae *************
Hydroscaphidae
Chelonariidae
Psephenidae
Curculionidae
Helodidae
HEMIPTERA
Naucoridae **********
Mesoveliidae
Veliidae
Gerridae
Hebridae
Fig. 5.— Occurrence of families of Diptera, Coleoptera, and Hemiptera at all stations during both seasons.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 84
Key: ***** Wet season
----- Dry season Station 5 6 7
ODONATA
Agrionidae
Gomphidae
PLECOPTERA
Peltoperlidae
Pteronarcidae
NEUROPTERA
Sialidae
Fig. 6.— Occurrence of families of Odonata, Plecoptera, and Neuroptera at all stations during both seasons.
dry season, but was restricted to two stations only during
the wet season.
Peltoperlidae and Pteronarcidae were the only families
of the order Plecoptera that were found (Figure 6). Both
families were limited in distribution.
The order Neuroptera was represented only by the family
Sialidae (Figure 6). Members of the family were present at
several stations during the dry season, but were limited to
one station only during the wet season.
Another major taxonomic group that was observed by the
river was the Oligochaeta (Figure 7). This group was repre
sented by the Tubificidae and the Naididae families.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Key: ***** wet season
Dry season Station 5 6
OLIGOCHAETA
Tubificidae
Naididae
GASTROPODA Pla.no rbidae *************************
Bulminidae ************
Physidae ****** ******
Lyranaidae
Unionidae
Fig. 7.— Occurrence of families of Oligochaeta and Gastropoda at all stations during both seasons.
Although members of both were present during each season,
representatives of the former showed a wider distribution
range.
Five families of the order Gastropoda were found in the
Belize River. These were Planorbidae, Bulminidae, Physidae,
Lymnaidae, and Unionidae (Figure 7). Of these families,
members of the Planorbidae were the most prevalent forms.
They were present at virtually all the stations during both
seasons. The other families were also present during both
seasons, but they showed a less wide distribution range.
The percentages of the invertebrate groups per square
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foot were determined for both seasons. These percentages
appear in Tables 12 (dry season) and 13 (wet season).
During the dry season, representative organisms from
ten major taxonomic groups were collected. The groups repre
sented were Tricoptera, Ephemeroptera, Diptera, Coleoptera,
Hemiptera, Odonata, Plecoptera, Oligochaeta, Gastropoda, and
Neuroptera.
At Stations 3, 4, and 5, members of the order Tricoptera
were more numerous than at Stations 6, 7, and 8 (Table 12).
TABLE 12.— Percentages of Invertebrate Groups Occurring at Each Station During Dry Season
Station
3 4 5 6 7 8
Tricoptera 16.2% 13. 9% 13.8% 8.5% 2.9% 10.1%
Ephemeroptera 14.5 20.4 15.4 12.4 21. 6 10.1
Diptera 11.1 17.6 12.4 15.5 14.7 16.2
Coleoptera 6.8 16.7 15.2 17.1 14.7 13.0
Hemiptera 7.8 2.8 4.8 6.9 6.1
Odonata 3.4 2.7 3.1 6.9 8.1
Plecoptera 5.1 12.0 4.1 3.9
Oligochaeta 9.5 10.1 11.7 19.4 18. 6 11.1
Gastropoda 25.4% 6.5% 13.1 12.4 14.7 21. 2
Neuroptera 6.2% 4.7% 1.9% 4.1%
The highest percent of 16.. 2 was observed at Station 3. The
lowest percent of 2. 9 was observed at Station 7 Among the
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other stations, the range was from 8.5 percent at Station 6
to 13.9 percent at Station 4.
Members of the order Ephemeroptera were present at all
stations sampled (Table 12). Stations 4 and 7 showed the
high percentages of this group, which were 20.4 percent and
21.6 percent, respectively. These stations are in regions
where there is relatively minimal human activity. At the
other stations, the range was between 10.1 percent at Station
8 and 15.4 percent at Station 5. The three lowest percent
ages occurred in regions where there are major villages and
high levels of human activity. Perhaps these situations may
have contributed in some form to the low percentages noted.
These three stations— 3, 6, and 8— ranged between 10.1 per
cent at Station 8 and 14.5 percent at Station 3. At Station
5, the percent calculated was 15.4. This station lies
several miles below Station 6, and the external influences
on the ri.ver at Station 6 might have been diminished and
thus account for the slightly greater percentage at Station 5.
The percentages of the order Diptera showed fluctuations
across the six stations investigated (Table 12). The higher
percentages were obtained at Stations 4, 6, and 8. The range
was between 15.5 percent at Station 6 and 17..6 percent at
Station 4. Probably, this pattern of abundance is influenced
largely by the substrate. At Stations 3, 5, and 7, the range
was from 11.1 percent at Station 3 to 14.7 percent at Station
7. Station 5 had a percent of 12.4.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Members of the insect order Coleoptera were found at
all the stations sampled (Table 12). The lowest percentage
occurred at Station 3; the value was 6.8 percent. It is
worth noting that there was a general trend in which the
abundance of members of this order increased as one proceeded
down river from Station 8 to Station 4. The values at Sta
tions 4 and 8 were 16.7 percent and 13 percent, respectively.
Station 6 deviated somewhat from this general trend with a
percent value of 17.1. The abrupt decrease at Station 3 may
be attributed to occasional salt-water intrusion at lower
depths at the station.
The order Hemiptera fluctuated greatly in percentage
distribution (Table 12). Its presence was not observed at
Station 7. At Station 3, the highest percentage was recorded.
Here the percent was 7.8, whereas at Station 4 it was only
2.8 percent. It is worth noting that the highest percentages
obtained were at Stations 3, 6, and 8. These stations are
associated with regions of human populations and agricultural
activity. The values among these three stations ranged from
6.1 percent at Station 8 to 7.8 percent at Station 3. In
the sparsely populated regions of Stations 4, 5, and 7, the
relative values ranged from 0 percent at Station 7 to 4.8
percent at Station 5.
Table 12 shows that members of the order Odonata were
absent from Station 4. It may be that the lack of aquatic
vegetation at this station may have reduced the likelihood
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of its presence. Pennak (1978) noted that the immature
forms of this insect tend to occur in regions where such
vegetation is present. The highest percentage of this insect
order was found at Station 8. Here the value was 8.1 percent.
The lowest percentage was found at Station 5. At Stations 3,
6, and 7, the relative values ranged from 3.1 percent at
Station 6 to 6.9 percent at Station 7.
Another major invertebrate group that was observed in
the Belize River was the insect order Plecoptera (Table 12).
The highest percentage of this taxonomic group was found at
Station 4 (12 percent). At Stations 3, 5, and 7, the values
ranged from 3.9 percent at Station 7 to 5.1 percent at Sta
tion 3. The percent at Station 4 was 4.1. Members of the
order Plecoptera were not observed to occur at Stations 6
and 8. This may result from current velocity and substrate
type. Representative forms of this order are generally found
in fast-flowing water and stony substrates (Pennak, 1978).
Members of the order Oligochaeta were present at all
stations investigated (Table 12). The high percentages
occurred at both Stations 6 and 7, which were 19.4 percent
and 18.6 percent, respectively. At Stations 4, 5, and 8, the
percentages were fairly similar. The range among these sta
tions was between 10.1 percent and 11.7 percent. The lowest
value occurred at Station 3, where the percent was 9.5.
Several forms of the order Gastropoda were present among
the six stations sampled (Table 12). High values were
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recorded at Stations 3 and 8, namely, 25.4 percent and 21.2
percent. The lowest percentage was at Station 4, where the
value was 6.5 percent. At Stations 5, 6, and 7, the range
was between 12.4 percent at Station 6 and 14.7 percent at
Station 7. Station 5 had a percent of 13.1.
The last major taxonomic group occurring in the Belize
River was the insect order Neuroptera (Table 12). Its pres
ence was primarily restricted to Stations 5-8. Among these
stations, the values ranged from 6.2 percent at Station 5 to
1.9 percent at Station 7. At Stations 6 and 8, the values
were 4.7 percent and 4.1 percent, respectively.
The taxonomic groups described above were not so abun
dant during the wet season (Table 13). Scouring effects and
increased turbidity may be among the major factors contribut
ing to this condition.
Representatives of the order Tricoptera were not found
at Stations 6, 7, and 8 (Table 13). These three stations
showed lower percentages than did the others during the dry
season. At the other three stations, lower percentages were
noted in the wet season. The percentages increased as one
proceeded downstream from Station 5 to Station 3. The range
was between 5.6 percent at Station 5 and 13.6- percent at
Station 3. As velocity decreased further downstream, some
of the organisms from further up-river may have lodged on
the substrate. Those present in this region originally may
not have been easily dislodged.
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 91
TABLE 13.— Percentages of Invertebrate Groups Occurring at Each Station During Wet Season
Station Group 3 4 5 6 7 8
Tricoptera 13.6% 8.0% 5.6%
Ephemeroptera 9.1 6.0 5.6 6.5% 8.3% 8.7%
Diptera 9.1 22. 0 24.1 9.7 16.6 39.1
Coleoptera 4.5 12. 0 9.3 12. 9
Hemiptera 2.2 2.0 3.2
Odonata 2.2 3.6
Plecoptera 4.5
Oligochaeta 9.1 18.0 33. 3 45.1 66.7 39.1
Gastropoda 45.5% 32. 0% 12.9 22. 6% 8.3% 13. 0%
Neuroptera 5.5%
Members of the order Ephemeroptera seemed to be more
resistant to flood conditions. Their presence was observed
at all stations (Table 13). The overall range was between
5.6 percent at Station 5 and 9.1 percent at Station 3. Sta
tions 4, 6, 7, and 8 had fairly similar percentages.
Representatives of the insect order Diptera were also
found at all stations during the wet season (Table 13). In
general, this taxonomic group had higher wet-season percent
ages at most of the stations. At Stations 3 and 6, low
values were recorded, namely, 9.1 percent and 9.7 percent.
Although these percentages were somewhat lower than the
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. dry-season values, across the other stations the wet-season
percentages were higher. These values ranged from 16.6 per
cent to 39.1 percent. Stations 4 and 5 had fairly similar
values, namely, 22 percent and 24.1 percent.
In the wet season, the order Coleoptera was not found
at Stations 7 and 8 (Table 13). As mentioned previously,
scouring effects may have been responsible for this condi
tion. The lowest percentage was found at Station 3. Among
Stations 4, 5, and 6, the highest percentage was observed at
Station 6 and the lowest at Station 5. Similar percentage
trends were noted during the dry season. As with most
orders, the Coleoptera was less abundant in the wet season.
Members of the order Hemiptera were also less abundant
in the wet season. It was observed only at Stations 3, 4,
and 6 (Table 13). In the dry season, it was observed at two
other stations. The values were generally similar at Sta
tions 3 and 4, namely, 2.2 percent and 2 percent. The
Hemipteran value at Station 6 was 3.2 percent.
Members of the order Odonata were noted to be present
only at two stations during the wet season, namely, Stations
3 and 5 (Table 13). The values were 2.2 percent and 3.6
percent, respectively.
The least abundant insect order during the wet season
was the order Plecoptera. It was found only at Station 3,
where the value was 4.5 percent (Table 13). Both scouring
and turbidity effects may have produced this limited
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 93
abundance and distribution.
Oligochaetes were observed at all stations and generally
showed much higher percentages during the wet season (Table
13). High percentages were found at Stations 6 and 7, and a
similar trend was noted in the dry season. The wet-season
values were 45.1 percent and 66.7 percent, respectively.
Gastropods were also present at all stations in the wet
season (Table 13). Their values were generally higher in
this season, ranging from 8.3 percent at Station 7 to 45.5
percent at Station 3. Stations 5 and 8 had almost the same
values, namely, 12.9 percent and 13 percent. The values at
Stations 4 and 6 were 32 percent and 22.6 percent.
The last major taxonomic group that was found in the wet
season was the order Neuroptera (Table 13). Members of this
group were observed only at Station 5, whereas in the dry
season they were found at Stations 5-8. The value at Station
5 during the wet season was 5.5 percent.
The data discussed above indicated that the benthic
fauna of the Belize River is comprised of numerous families
of aquatic organisms. However, seasonal changes produced a
marked shift in this fauna. Although numerous factors might
have contributed to the changes noted, heavy sedimentation
that may result from runoff is said to cause predictable
shifts in the community composition. Typical changes would include a decrease in most Ephemeroptera, Plecoptera, and
Tricoptera. Sediment-resistant forms include some Baetidae,
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 94
some Chironomidae, and some Elmidae (Barton, 1977; Bjornn et
al., 1977; Duchrow, 1977; Maughan, 1977).
Planktonic Parameter
After the number of individuals of phytoplankton per one
milliliter of sample was determined, the species diversity,
equitability, total number of genera, and total number of
individuals at each station during both seasons were calcu
lated. Tables 14 (dry season) and 15 (wet season) list these
values.
TABLE 14.— Species Diversity (d) and Equitability (e) of Algae with Summary Data for All Stations During Dry Season
Species Total Number Station Prinitabiiitv Total Number Diversity Equitability Individuals Genera
1 1.74 .27 631 15 2 1.84 .29 571 17 3 4.26 .80 640 35 4 4.45 .80 981 40 5 3.84 . 60 957 35 6 4 . 05 .73 784 33 7 3.90 .81 435 27 8 3. 52 .80 619 21
In general, it seems that the planktonic populations
tend to be greater in the dry season than in the wet season.
The most pronounced seasonal differences were noted at Sta
tions 1, 2, and 6. During both seasons, Stations 4 and 5
were observed to have the greatest number of individuals
Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE 15.— Species Diversity ( Species Total Number Total Number Station Equitability Diversity Individuals Genera 1 2.02 .33 462 18 2 2.56 .50 317 16 3 3.13 .72 562 18 4 4.31 .91 1017 32 5 3.80 .75 1009 28 6 2.83 .52 362 19 7 3.15 .86 466 15 8 2.70 .53 608 18 (Tables 14 and 15). It was observed that the total numbers of individuals per one milliliter generally increased during the wet season as one moved from Station 1 through Station 5. This increase was followed immediately by a marked decrease in number of individuals per one milliliter at Station 6. A slight increase was observed at Station 7, and this trend was also observed at Station 8. A similar pattern was observed across all stations during the dry season. The lowest dry- season value was observed at Station 7, and the lowest wet- season values were observed at Stations 2 and 6. An examination of the calculated values.reveals that species diversity was generally higher during the dry season than during the wet season (Tables 14 and 15). At Stations 1 and 2, wet-season values were greater than for the dry season but were generally lower at the other stations. The Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 96 lowest diversity values were noted at these two stations. The high incidence of organic effluent present in the river in this region undoubtedly created an environment that restricted the diversity and abundance of the phytoplankton present. It has been suggested that species diversity values between the range of 3 and 5 are indicative of clean, non polluted waters. Values lower than 3 are indicative of polluted conditions (Weber, 1973). The equitability factor is closely related to species diversity. Tables 14 and 15 show that lowest equitability values were obtained at Stations 1 and 2, whereas higher values were obtained generally at the other stations. It has been suggested that equitability values below the .5 level are indicative of polluted waters. Values above this level are generally considered indicative of clean, non-polluted waters (Weber, 1973). From the standpoint of species diversity and equita bility as derived from the phytoplankton data, it is evident that the waters at Stations 1 and 2 are polluted, and at the other stations the water can be considered non-polluted. Tables 14 and 15 indicate the number of .representatives of genera that were observed at each station during both seasons. Generally speaking, individuals representing the greatest number of genera occurred during the dry season at most of the stations. The scouring effect of flooding that Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 97 takes place during the wet season may be responsible for the low number of genera generally present. Stations 1 and 2 had the lowest number of genera during both seasons. As mentioned earlier, the high incidence of effluent present in the river may have restricted the algal population. High numbers of genera were observed at Stations 3-6, with the highest value at Station 4 and a relatively low value at Station 8. Table 16 shows the percentages of each of the major taxonomic groups of algae that were observed at the eight stations during the dry season. TABLE 16.— Percentages of Various Algal Phyla Occurring at Each Station During Dry Season Phylum Station Cyano Chloro- Chryso- Rhodo- Pyrro- Eugleno- phyta phyta phyta phyta phyta phyta 1 91. 6% 4 . 3% 2.4% . 9% .8% 2 85.9 3.0 2.7 5.8 2.1 .5% 3 17.0 35.6 41.2 2.6 2.7 . 9 4 12.8 45.4 32.5 2.8 3.7 2.7 5 17.6 38. 6 29.8 .8 3.1 8.8 6 9.9 39.8 35.7 1.4 1.2 12.0 7 6.7 38.8 40.5 1.1% 6.9 6.0 8 13. 8% 43.8% 41.3% ' .1% .8% Members of the Cyanophyta were the predominant group at Stations 1 and 2. However, at the other stations the per centages of this group present were considerably less. At Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 98 these stations, its presence ranged from 6.7 percent at Station 7 to 17.6 percent at Station 5. The high percentages may be attributed to the great organic effluent present at these two stations. Members of the Chlorophyta showed a fairly even distri bution pattern at Stations 3-8 (Table 16). The values ranged between 35.6 percent at Station 3 and 4 5.4 percent at Station 4. At Stations 1 and 2 the values of this group were 4.3 percent and 3 percent, respectively. It is possible that the effluent present in the river may have hindered their growth rate. Members of the Chrysophyta group showed the widest per centage range at the last six stations. The range was 29.8 percent at Station 5 to 41.3 percent at Station 8. Like the representatives of the Chlorophyta, this group was much less abundant at the first two stations, the values being 2.4 percent and 2.7 percent, respectively (Table 16). The highest incidence of members of the Rhodophyta was observed at Station 2, namely, 5.8 percent (Table 16). At Station 1 the value was .9 percent, but between Stations 3 and 7, Rhodophyta ranged from .8 percent (Station 5) to 2.8 percent (Station 4). None of this taxonomic group was detected at Station 8. The limited abundance of members of this group is not surprising since some members are fresh water inhabitants, whereas most are believed to inhabit brackish water (Bold & Wynne, 1978). Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 99 Only small populations of Pyrrophyta were found at any station (Table 16). The highest value, 6.9 percent, was observed at Station 7 and the lowest percentages at Stations 1 and 8. At the other stations, the values ranged from 1.2 percent at Station 6 to 3.7 percent at Station 4. Members of the Euglenophyta were not detected at Station 1 (Table 16), although at Station 2 the value was .5 percent. However, there was a marked increase as one proceeded up-river through Station 6. Here the value was 12 percent, but at Station 7 the value was only 6 percent. There was a further decrease at Station 8 where the value was .8 percent. As shown in Table 17, the percentages of the various algal divisions were different in the wet season. TABLE 17.— Percentages of Various Algal Phyla Occurring at Each Station During Wet Season Phylum Station Cyano- Chloro Chryso- Rhodo Pyrro Eugleno Phaeo- phyta phyta phyta phyta phyta phyta phyta 1 81. 2% 12. 3% 4.1% . 7% . 9% . 6% . 2% 2 67.1 11.8 11.8 1.5 5.6 2.1 3 13.2 35.4 47.1 1.1 2.8 .4 4 19.2 43.1 35.5 2.5 3.2 2.6 5 19.2 40.2 35.2 .2% 3.4 1.8 6 6.1 47.2 43.4 1.1% 2.2 7 22.5 39.3 37.8 .2 8 9.2% 40.1% 50.3% .3% Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 100 Cyanophyta individuals were again predominant at Sta tions 1 and 2 (Table 17). Although not so abundant as in the dry season, they were substantially more abundant at these two stations than the other major groups. At the other stations during the wet season, the values ranged from 6.1 percent at Station 6 to 22.5 percent at Station 7. No appar ent reason can be given for this major difference between these adjacent stations. During the dry season, Cyanophyta were more abundant at Stations 3, 6, and 8. Fairly similar percentages were observed at Station 4 during both seasons. In the wet season, greater percentages were observed for Stations 5 and 7. Chlorophyta showed a higher percentage at Stations 1 and 2 in the wet season than during the dry season (Table 17). Flooding conditions may have increased their numbers at these two stations. However, at the other stations, the percentages did not seem to differ greatly between seasons. Only minor increases were noted at Stations 5, 6, and 7 during the wet season. At Stations 4 and 8, the dry-season percentages were slightly higher. Representative members of Chrysophyta were more abundant at Stations 1 and 2 in the wet season than in the dry season (Table 17). At the other stations, the values ranged from 35.2 percent at Station 5 to 50.3 percent at Station 8. Higher wet-season percentages were observed at all these stations. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 101 During the wet season, representatives of the Rhodophyta were not detected at Stations 6, 7, and 8 (Table 17). This phenomenon could be predicted since their abundance at these stations during the dry season was quite limited. The scour ing effect of flooding may have contributed to their dis appearance from these stations. At Stations 3, 4, and 5, greater percentages were observed during the dry season. However, the abundance at each of these stations during both seasons showed a fairly similar pattern. The lowest percent ages were observed at Station 5 and the highest percentages at Station 4. Greater dry season percentages were also noted for Stations 1 and 2, with the higher percentage values occurring in both cases at Station 2. Pyrrophyta were not observed at Stations 7 and 8 during the wet season (Table 17). At Stations 1, 2, and 3, the wet- season values were higher than those of the dry season. The differences, however, were not great. Whereas members of the division Euglenophyta were pres ent at all stations during the wet season (Table 17), they were generally less abundant than during the dry season. They were observed in greater numbers only at Station 2. The values during this season ranged from .2 percent at Sta tion 7 to 2.6 percent at Station 4. Representatives of the Phaeophyta were observed at Sta tion 1 only during the dry season. They did not appear at any of the stations during the wet season. This taxonomic Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 102 group is primarily restricted to brackish water and salt water. Its presence in fresh water is rare (Bold & Wynne, 1978). In conclusion, the data show that Cyanophyta representa tives were the most prevalent group at Stations 1 and 2. At the other stations, Chlorophyta and Chrysophyta were the most abundant, but neither was substantially more abundant than the other. The data collected from the various stations showed that the zooplankton organisms were greatly outnumbered by the phytoplankton. This finding is not surprising, as earlier studies showed that this is generally the case (Greenberg, 1964; Reinhard, 1931). The percentages of the major zooplankton groups were calculated and appear in Tables 18 (dry season) and 19 (wet season). Representatives of four major groups were observed in the Belize River, namely, Protista, Rotifera, Cladocera, and Copepoda. During the dry season, all four groups were present. However, at Stations 1 and 2 only three of the four groups were observed (Table 18). The dominant group at both these stations was the Protista, the values being 87.5 percent and 96.4 percent, respectively. Rotifers and cladocerans were two other taxonomic groups present. At Station 1, Rotifera were more abundant than Cladocera. The value of the former was 8.9 percent and the latter, 3.5 percent. Both groups were present in like number Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 103 TABLE 18.— Relative Percentages of Major Zooplankton Groups Occurring at Each Station During Dry Season Group Station Protista Rotifera Cladocera Copepoda 1 87. 5% 8.9% 3.5% 2 96.4 1.8 1.8 3 23.2 64.2 7.1 5.3% 4 27.9 32.8 31.1 8.2 5 32.1 54.7 7.5 5.6 6 23.8 52.4 7.1 16.6 7 35.3 44.1 11.7 8.9 8 24.3% 46.4% 19.5% 9.7% at Station 2, the percent being 1.8. Across the other stations, the percentage of protistans was noticeably lower. The range of values among the stations was between 23.2 percent at Station 3 and 35.3 percent at Station 7. Stations 6 and 8 showed fairly similar values, namely, 23.8 percent and 24.3 percent. The values at Sta tions 4 and 5 were higher, the former being 27.9 percent and the latter, 32.1 percent. Rotifers were present in markedly higher percentages at Stations 3-8. At these stations, the rotifers were the dominant forms (Table 18). A similar occurrence was observed from a sampling of the major rivers of the United States (Williams, 1966). The rotifer values ranged from 32.8 per cent at Station 4 to 64.2 percent at Station 3. In general, there was a trend toward increased rotifer percentages as Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 104 one proceeded down the river. A discrepancy in this trend was observed at Station 4, where there was a marked decrease. At Stations 5 and 6, the values were 54.7 percent and 52.4 percent, respectively, and at Stations 7 and 8 they were 44.1 percent and 4 6.4 percent. Members of the Cladocera were observed at all stations (Table 18). The low percentages of this group were obtained at Stations 1 and 2, with 3.5 percent and 1.8 percent, respectively. Stations 3 and 6 had like values of 7.1 per cent, while Station 5 had a value of 7.5 percent. Higher values ranged between 11.1 percent at Station 7 and 31.1 percent at Station 4, with the value at Station 8 being 19.5 percent. Copepods were present only at Stations 3-8 (Table 18). In general, they were the least abundant forms occurring in the river. The highest percentage was observed at Station 6, where the value was 16.6 percent. The lowest value was obtained at Station 3, namely, 5.3 percent. Station 5, with 5.6 percent, had a value similar to that of Station 3. Sta tions 4 and 7 showed similar values of 8.2 percent and 8.7 percent, respectively. At Station 8, the copepod value was 9.7 percent. A marked difference in zooplankton composition was noted between the wet and dry seasons, the organisms being gener ally less abundant during the wet season. Factors such as scouring and turbidity may have caused this difference. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 105 As in the dry season, members of the Protista were the dominant form observed at Stations 1 and 2 (Table 19), the values at these stations being 94.2 percent and 93.3 percent, respectively. The rotifer and the cladoceran percentages were similar at Station 1 in the wet season, the value being 2.8 percent. This value was less than that obtained in the dry season. At Station 2, the value of rotifers was 2.2 per cent and that of the cladoceran, 4.3 percent. At this sta tion, these values were higher than those of the dry season. TABLE 19.— Relative Percentages of Major Zooplankton Groups Occurring at Each Station During Wet Season Group Station Protista Rotifera Cladocera Copepoda 1 94.2% 2.8% 2.8% 2 93.3 2.2 4.3 3 24. 0 76.0 4 50. 0 40.0 10.0 5 30.8 69.2 6 30.7 61. 5 7.7 7 37.5 50. 0 12.5% 8 30.0% 70.0% Among the other stations, Protista values ranged from 24 percent at Station 3 to 50 percent at Station 4. Stations 5, 6, and 8 showed approximately the same values, these being 30.8 percent at Station 5; 30.7 percent at Station 6; and 30 percent at Station 8. The value at Station 7 was 37.5 percent. In general, these percentages were higher than the Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 106 dry-season values. The rotifers were the major forms collected during the wet season, with their percentage values being generally higher than the dry-season values. The highest percentage was obtained at Station 4, with a value of 40 percent. Sta tions 5 and 8 had approximately the same values, the former being 69.2 percent and the latter, 70 percent. At Stations 6 and 7, the values were 61.5 percent and 50 percent, respectively. The next major taxonomic group present in the wet season was Cladocera (Table 19), but only present at three stations, namely, 4, 6, and 7. Both Stations 4 and 7 had higher per centage values in the wet season than in the dry season. In the wet season, the value at Station 4 was 10 percent and at Station 7, 12.5 percent. At Station 6, the wet-season value was 7.7 percent, which was lower than the dry-season value. Microbiological Parameter After the original data had been collected for total bacteria, total coliform, and yeast/mold, the average number of colonies for both seasons together with the standard deviation were determined for each station. The results of these calculations appear in Table 20. An examination of the data collected indicates that, for total bacteria, the wet-season counts were generally higher at all stations. The data also show that the highest Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 107 904 770 950 960 116 118 100 100 120 128 160 139 203 117 104 157 + ± + ± + + + + + + + + + + + + 125 271 166 375 487 1 ,250 1 ,875 738 960 178 1,380 175 2,065 218 1,2001,280 183 250 1,3802,220 258 306 2,050 1,507 1,687 1,348 21,000 15,900 1 ,937 22,300 12,790 1 ,500 ± + + + + + + ± + ± + + + + + + 2,583 3,500 2,100 3,166 3,250 1,333 3,071 3,333 56,250 33,333 8,017 8,140 4,875 9,714 71,500 48,333 59,900 83,500 72,000 48,125 11,800 13,130 11,600 12,933 12,800 2,166 10,820 10,04013,580 2,583 11,807 4,625 + + + + + + + + + + ± + + + + + 99,750 83,583 658,750 460,000 384,166 517,500 105,333 123,375 115,500 100,214 118,000 134,250 103,500 122,928 137,937 113,000 One Standard Deviation (given as number of colonies per 100 ml) Dry- Wet Dry Wet Dry Dry Dry Dry Wet Wet Wet Dry Dry Wet Wet Wet Station/Season Total Bacteria Total Coliform Yeast/Mold TABLE 20.— Mean Levels of Total Bacteria, Total Coliform, and Yeast/Mold Counts ± Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 108 counts during both seasons were obtained at Stations 1 and 2 (Figure 8). The wet-season bacterial counts at Stations 1 and 2 were both above 500,000 colonies per 100 ml of water sample. In the dry season, the mean number of colonies at these two stations ranged from 360,000 to 425,000 colonies per 100 ml. These extremely high values may be attributed to the high incidence of organic effluent present in the river at these two stations. The counts were fairly similar for the other stations, the highest being observed at Stations 6 and 8. These two sites are regions that are populated, and Station 8 is also the site of much livestock activity. These factors may have contributed to the different counts recorded at the latter six stations. Station 4 showed the fewest colonies per 100 ml during both seasons. This region is thinly populated and thus does not place major stress on the river. The major rice-growing operation up-river does not seem to have stimu lated the growth of bacteria. Figure 9 illustrates the differences of total coliform counts per 100 ml among the various stations. It is evident that Stations 1 and 2 had the highest counts during both seasons. Wet-season mean values were, on the whole, higher at all stations. Possibly the runoff brought about the intro duction of coliform spores into the river and the presence of moisture triggered their growth. A similar explanation Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced o l sain drn e ad r seasons. dry and wet during stations all for Number of colonies i. —Hsormo smaydt fr oa bacteria total for data summary of Histogram .— 8 Fig. 4 5 6 1 2 3 0 1 2 5 4 3 Stations 6 e season Wet r season Dry 7 8 109 110 60 50 - Wet season 40 - J Dry season 30 o rH Cfl 0) ■H o r—I o o o u QJ 1 2 3 4 5 6 7 8 Stations Fig. 9.— Histogram of total coliform counts for all stations during wet and dry seasons. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 111 may apply to the higher wet-season total bacterial counts mentioned earlier. The high counts at Stations 1 and 2 may be attributed to the input of raw sewage into the river near these two stations. Among the other stations, 6 and 8 showed high counts that were similar, ranging between 4,500 and 4,900 colonies per 100 ml during the dry season. These high mean levels most likely are the result of human activities at these two sites. The wet-season levels for Stations 3, 5, and 7 were between 3,000 and 3,500 colonies per 100 ml. The dry-season levels ranged from slightly more than 2,000 colonies per 100 ml at Station 5 to about 2,700 colonies per 100 ml at Stations 3 and 7. The lowest mean values were obtained at Station 4, the mean value during the wet season being about 2,100 colonies per 100 ml and, during the dry season, about 1,400 colonies per 100 ml. It has been suggested that if samples are taken from river water and analyzed for total coliform counts, the coli form population is likely to be in the range of 10 to 10,000 colonies per 100 ml in clear, unpolluted river water. In the case of turbid, polluted river water, the range has been estimated to be between 2,000 and 1,000,000 colonies per 100 ml (Hach, 1977) . On the basis of the number of colonies found per 100 ml, Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 112 it seems that the portion of the river between Stations 3 and 8 can be considered fairly clean. Figure 10 illustrates the major differences among the stations in yeast/mold colony counts during both seasons. Both Stations 1 and 2 had colony counts greater than 1,000 per 100 ml, this situation existing during both seasons. It seems that the high incidence of organic effluents present in the river has contributed to the increased number of colonies present. Among the other stations, high counts were obtained at Stations 6 and 8, the introduction of livestock waste pos sibly triggering these high counts. The high mean values at Station 7 during the wet season probably reflects only up-stream activities and not local conditions in the immedi ate vicinity of this station. Stations 3, 4, and 5 had wet-season mean values ranging from 180 colonies per 100 ml at Station 4 to 250 colonies per 100 ml at Station 5. Their dry-season mean levels all were below 200 colonies per 100 ml, ranging from 125 colonies per 100 ml at Station 4 to 185 colonies per 100 ml at Station 5. Nektonic Parameter From the qualitative data collected on the nektonic fauna of the Belize River, general distribution patterns of the various fish families were determined (Figure 11). Of Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 113 2 0 0 0 - Wet season Dry season 1000 500 - w 200 100 ~ 1 2 43 5 6 7 8 Stations Fig. 10.— Histogram of yeast/mold counts for all stations during wet and dry seasons. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 114 Station Family 12345678 Ictaluridae **************************************** Pimelodidae ****************************** Poeciliidae *********************************** Cyprinodontidae ****************************** Characidae ************************* Cichlidae **************************************** Sparidae ******************** Centropomidae **************************************** Elopidae **************************************** Saranidae ******************** Carcharhinidae *************** Orectolobidae *************** Belonidae *************** Pristidae *************** Lutjanidae ********** Gerridae ***** Pomadasyidae ***** Mugilidae ******************** Fig. 11.— General distribution of the. fish fauna of the Belize River as derived from the qualitative data collected. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 115 the eighteen families said to be present in the river, mem bers of the families Ictaluridae, Cichlidae, CentropomMae, and Elopidae were the most prevalent, being observed at all the stations visited. The families Pimelodidae, PoeciMidae, Cyprinodontidae, and Characidae were the next most widely distributed families, with distribution patterns over Stations 2-8. Three families of fish appeared to be limited to Sta tions 1-4. These were Sparidae, Saranidae, and Mugi1ifhe. The families Sparidae and Mugilidae are generally marire organisms, but a few species have been observed in fresh water bodies (Miller, 1966). The families Lutjanidae, ffier- ridae, and Pomadasyidae were restricted primarily to Station 3 (Figure 11). These fish families are primarily marina organisms, but some species of these families are known to move into brackish water, and even fresh water (Miller, 1966). It is possible that these fish were introduced into the river where the river meets the sea just below Haulover Creek. The remaining four families— Carcharhinidae, Orectolo bidae, Belonidae, and Pristidae— were observed only at Sta tions 1, 2, and 3 (Figure 11). These are primarily marine fishes. It is evident from the data gathered that the fish fauna of the Belize River is diverse and reflects non-polluted conditions. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. CHAPTER V CONCLUSIONS AND RECOMMENDATIONS From the data gathered, it seems that the water at Sta tions 1 and 2 is of low quality. At both these stations, the chemical composition of the water showed levels of metals and cations that were far greater than those generally allowed in domestic water supplies. It is evident that the discharge of human and industrial wastes has led to the degradation of the water quality at these two sites. At the other stations, the water quality may be considered generally acceptable based on a comparison with standard norms. At a few stations, however, some chemical levels were higher than those normally allowed in domestic water supplies. Alkalinity levels at Stations 6 and 8 and carbon dioxide levels at Station 8 were greater than those considered acceptable. Manganese levels generally were above those allowed in drinking water. In these loca tions, both human and industrial activities may have con tributed to the high levels encountered. Samples of the benthic fauna collected at Stations 3-8 reflect a great diversity, with numerous groups usually asso ciated with high water quality being found. On the basis of their presence, it can be assumed that this region of the Belize River is generally non-polluted. Algal samples collected from the eight stations support 116 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 117 the fact that the water quality is low at Stations 1 and 2; values for species diversity and equitability so indicate. At the other stations, the values obtained indicate that the water is clean. From the bacterial cultures prepared, evidence pointed to fecal contamination of the water at Stations 1 and 2. This finding is not surprising in that it is common knowledge that raw sewage is emptied into the water in these regions. At the other stations, the bacterial counts were much lower. However, Stations 6 and 8 showed slight increases that could have possibly resulted from the introduction of human and livestock wastes. Finally, the qualitative data showed the presence of a diversified fish fauna in the Belize River at Stations 3-8. This condition helps to support the general conclusion that the Belize River in this region is an unpolluted system. Although the evidence gathered in this investigation supports the conclusion that the major portion of the Belize River is currently of a high quality, it is recommended that every effort be made to limit the pollution of the river in the regions of Stations 1 and 2. Adequate sewage treatment and specific legislation governing the dumping of industrial wastes need to be implemented. In the regions of the other stations, it is recommended that continuous monitoring of the river be undertaken. The technical staff of the Belize Water and Sewage Authority may Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 118 be the appropriate body to carry out this task. Finally, the need to protect waterways should be brought to the attention of the Belizean public. This task may be accomplished primarily through the educational system. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPENDIX A DATA FOR PHYSICAL AND CHEMICAL PARAMETERS OF ALL STATIONS DURING BOTH SEASONS Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 120 Key: ACF = Free acidity, mg/1 ACT = Total acidity, mg/1 ALK = Alkalinity, mg/1 CO2 = Carbon dioxide, mg/1 CL- = Chloride, mg/1 CL = Chlorine, mg/1 NA2CRO4 = Sodium chromate, mg/1 CR-^ = Hexavalent chromium, mg/1 CU = Copper, mg/1 FL = Fluoride, mg/1 DO - Dissolved oxygen, mg/1 pH = Hydrogen ion conc. H2S = Hydrogen sulfide, mg/1 HCAL = Calcium hardness, mg/1 HTOT = Total hardness, mg/1 FE = Iron, mg/1 MN = Manganese, mg/1 NO^ = Nitrate, mg/1 NO~ = Nitrite, mg/1 O-PO^ = ortho phosphate, mg/1 m-PO^ = meta phosphate, mg/1 SI = Silicon dioxide, mg/1" SO^ = Sulphate, mg/1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Station \ \ \ \ \ \ \ \ 5/25/79 0 0 278 160 1050 1.30 110 .04 121 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Station 1 (Continued) 5/11/79 210 1450 .25 .20 71 .37 2.5 .8 1325 360 122 123 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Station 5/25/79 0 0 220 150 1100 .95 ' 130 .04 124 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Station 2 (Continued) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Station 2 (Continued) \ \ \ \ \ 5/25/79 30.5 29.5 .06 50 2.1 190 130 126 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Station 5/12/79 0 0 177 25 50 .20 58 .02 .04 127 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Station 3 (Continued) 5/27/79 250 370 .19 .08 30 .11 3.7 1.2 140 155 128 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Station 3 (Continued) 5/12/79 34.0 29.2 .13 129 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Station 5/12/79 0 0 139 18 24 .05 15 .05 .13 130 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Station 4 (Continued) \ \ \ \ \ \ 5/27/79 165 310 .10 .07 46 .09 2.8 1.9 40 160 131 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Station 4 (Continued) G H U U +J Eh -H o \ o g D M CD cu £ in o o ro oo oo 5/12/79 36.0 24. 132 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Station S/21/19 0 0 159 22 20 .05 35 .03 .13 133 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Station 5 (Continued) 5/27/79 180 310 .08 .06 38 .08 2.6 1.3 150 134 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Station 5 (Continued) 5/12/79 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Station 136 6/12/79 0 0 159 14 24 .07 45 .02 .07 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Station 6 (Continued) 5/14/79 120 170 137 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Velocity Width Depth Turbidity Color (m/sec) (m) (m) (FTU's) (APHA1 4/30/79 35. 138 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Station 5/29/79 0 0 135 25 18 .06 139 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Station 7 (Continued) \ \ \ \ 5/15/79 120 270 .10 .11 140 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Velocity Width Depth Turbidity Color 5/29/79 33.0 29.5 .05 26. 141 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Station 5/29/79 0 0 170 12 12 .06 30 .03 .08 142 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Station 8 (Continued) N O t— CO ON \ \ \ \ \ \ \ \ \ \ \ \ N N CN O CN H h O cn) CN H co o m CO O N O — O VO ON I— VO CN LO . \ \ N. \ — iI i—ICM i—I i—I O O O r- O N n o CN ro m cn CN on on co 5/29/79 140 210 .13 .11 42 .11 143 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. without prohibited reproduction Further owner. copyright the of permission with Reproduced Station 8 (Continued) 5/01/79 34.2 30.4 .03 34. 144 APPENDIX B DATA FOR INVERTEBRATE ORGANISMS COLLECTED AT EACH STATION DURING BOTH SEASONS (GIVEN AS NUMBER OF ORGANISMS PER SQUARE FOOT) 145 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 146 Key: agri = Agrionindae me so = Mesoveliidae amet = Ametropodidae naid = Naididae baet = Baetidae nauc = Naucoridae bulm = Bulminidae pelt = Peltoperlidae caen = Caenidae phys = Physidae chel = Chelonariidae plan = Planorbidae chir = Chironomidae psep = Psephenidae culi = Culicidae psyc = Psychomyiidae cure = Curculionidae pter = Pteronarcidae elmi = Elmidae scim = Sciomyzidae ephe = Epheraerellidae sial = Sialidae ephm = Ephemeridae tubi = Tubificidae gerr = Gerridae unio = Unionidae gomp = Gomphidae veli Veliidae hebr = Hebridae hele = Heleidae helo = Helodidae hydo = Hydroptilidae hydr = Hydropsychidae hyds = I-Iydroscaphidae lepo = Leptoceridae lept = Leptophlebiidae lymn = Lymnaeidae Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 147 Station 3 (Wet season) 1977 1978 1979 7/08 7/20 8/13 5/28 6/04 8/13 6/30 7/18 hydr 6 3 0 5 7 4 0 3 hydo 0 3 1 3 0 4 2 2 siph 2 0 1 1 2 1 1 0 trie 3 1 3 2 0 2 1 3 baet 0 1 2 1 1 0 2 1 chir 6 3 3 4 2 5 2 7 elmi 1 0 1 3 1 0 2 0 psep 2 0 0 2 0 1 1 1 nauc 1 2 0 0 0 2 1 1 meso 0 0 0 0 0 0 0 0 agri 0 1 0 1 1 1 0 1 pelt 4 1 2 1 1 2 0 1 tubi 3 7 2 6 2 5 3 4 plan 7 3 11 6 9 13 5 4 bulm 4 11 5 3 7 4 10 5 phys 7 6 13 11 7 3 4 5 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 148 Station 3 (Dry season) 1978 1979 5/06 4/21 4/30 5/12 5/27 6/10 hydr 17 8 10 7 19 12 hydo 9 11 5 7 6 4 siph 4 3 5 2 6 3 trie 13 7 5 9 11 8 baet 4 2 7 3 4 6 chir 18 9 20 11 15 7 elmi 2 4 1 3 3 4 psep 7 3 2 6 4 9 nauc 2 1 3 4 3 5 meso 8 3 4 7 5 3 agri 7 3 4 3 6 2 pelt 5 7 3 9 6 5 tubi 17 9 13 10 6 11 plan 19 12 6 10 15 9 bulm 13 8 5 7 11 6 phys 9 17 6 11 13 5 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 149 Station 4 (Wet season) 1977 1978 1979 7/08 7/22 8/20 5/28 6/09 8/19 6/30 hydr 4 1 2 3 5 1 3 hydo 2 1 0 1 1 2 0 lept 0 0 0 0 0 0 0 siph 0 0 0 0 0 0 0 trie 4 2 3 5 1 0 1 baet 0 0 0 0 0 0 0 hept 0 0 0 0 0 0 0 ephe 0 0 0 0 0 0 0 lept 2 0 1 1 2 0 2 chir 9 17 11 7 12 7 5 hele 0 1 2 2 1 0 3 elmi 0 3 2 1 5 1 0 hyds 0 0 0 0 0 0 0 chel 4 1 0 3 1 1 3 psep 2 0 1 1 1 0 2 nauc 0 1 2 0 0 1 1 pelt 0 0 0 0 0 0 0 pter 0 0 0 0 0 0 0 tubi 13 5 9 11 8 10 7 plan 2 0 0 1 1 0 1 lymn 0 0 0 0 0 0 0 bulm 13 3 7 11 4 9 3 phys 0 0 0 0 0 0 0 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 150 Station 4 (Dry season) 1978 5/12 4/21 4/30 5/12 5/27 6/10 hydr 13 7 9 11 7 5 hydo 3 7 4 1 6 3 lept 4 3 1 0 2 3 siph 11 5 3 7 4 5 trie 15 8 13 10 5 7 baet 3 5 1 0 3 2 hept 7 3 1 4 2 3 ephe 2 1 1 0 1 2 lept 0 0 0 0 0 0 chir 21 9 17 13 7 11 lele 6 1 3 4 7 4 elmi 9 3 1 1 7 4 hyds 7 5 1 3 0 1 chel 8 7 3 7 2 1 psep 11 5 2 4 9 7 nauc 7 2 0 4 1 3 pelt 12 7 5 9 15 4 pter 3 7 5 1 1 3 tubi 17 8 11 7 9 13 plan 7 3 1 0 1 5 lymn 7 9 1 3 5 2 blum 1 3 7 0 3 2 phys 4 2 0 7 6 3 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 151 Station 5 (Wet season) 1977 1978 1 9 7 9 7/09 7/22 5/31 6/09 8/20 7/01 hydr 0 0 0 0 0 0 hydo 7 1 0 4 3 1 psyc 0 0 0 0 0 0 siph 0 0 0 0 0 0 trie 0 2 1 1 4 2 baet 0 0 0 0 0 0 hept 0 0 0 0 0 0 ephm 0 0 0 0 0 0 lept 1 0 0 0 2 2 caen 0 0 0 0 0 0 chir 12 7 7 15 10 9 hele 3 6 2 5 0 2 elmi 1 5 3 1 7 2 chel 0 0 0 0 0 0 psep 0 0 0 0 0 0 cure 0 0 0 0 0 0 helo 4 1 0 3 0 5 nauc 0 0 0 0 0 0 veli 0 0 0 0 0 0 agri 4 0 0 4 1 1 pelt 0 0 0 0 0 0 sial 5 6 1 2 1 1 tubi 14 7 19 21 9 18 naid 1 0 7 3 6 1 plan 0 8 7 0 4 3 bulm 0 0 0 0 0 0 phys 0 0 3 6 1 9 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 152 Station 5 (Dry season) 1978 1979 5/12 4/21 4/30 5/12 5/27 6/10 hydr 7 3 12 6 9 3 hydo 15 7 5 10 5 13 psyc 6 9 3 0 1 3 siph 7 3 0 1 5 1 trie 13 5 9 5 10 7 baet 3 9 1 0 2 4 hept 7 7 0 3 6 2 ephm 1 0 0 2 1 2 lept 5 9 0 1 0 1 caen 3 1 0 1 0 0 chir 21 9 7 17 13 10 hele 11 3 2 8 5 3 elmi 7 4 4 11 3 8 chel 7 3 3 2 0 1 psep 2 4 0 7 1 4 cure 5 0 2 1 0 2 helo 3 9 7 11 5 7 nauc 0 5 1 3 9 7 veli 6 3 0 5 3 0 agri 0 7 3 0 9 5 pelt 11 3 3 5 9 6 sial 13 4 4 9 15 8 tubi 25 13 9 17 20 17 naid 0 0 0 0 0 0 plan 4 7 12 3 9 6 bulm 6 3 6 1 1 0 phys 4 17 9 11 4 9 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 153 Station 6 (Wet season) 1977 1978 1979 7/10 7/23 8/20 5/31 6/10 8/20 7/01 7/18 hydr 0 0 0 0 0 0 0 0 hydo 0 0 0 0 0 0 0 0 trie 2 2 0 1 1 0 1 2 lept 0 0 0 0 0 0 0 0 amet 0 0 1 1 2 2 0 0 chir 0 3 7 0 5 7 3 1 hele 0 0 0 0 0 0 0 0 culi 0 0 0 0 0 0 0 0 tipu 0 0 0 0 0 0 0 0 elmi 3 2 0 6 1 3 0 3 chel 0 0 0 0 0 0 0 0 psep 0 0 0 0 0 0 0 0 cure 0 0 0 0 0 0 0 0 helo 3 0 1 0 0 3 1 1 nauc 0 0 0 0 0 0 0 0 meso 0 0 0 0 0 0 0 0 veli 0 0 0 0 0 0 0 0 gerr 0 1 1 0 1 0 1 2 sial 0 0 0 0 0 0 0 0 tubi 15 8 13 5 11 9 17 8 naid 4 1 3 3 7 2 5 1 plan 11 3 9 6 3 4 5 5 phys 0 0 0 0 0 0 0 0 unio 3 0 1 1 2 2 0 1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Station 6 (Dry season) 1978 1979 5/14 4/22 4/30 5/14 5/28 6/12 hydr 9 7 3 3 11 7 hydo 8 4 6 1 0 3 trie 15 7 11 4 7 9 lept 3 11 4 2 2 0 amet 9 3 0 3 1 2 chir 7 11 17 19 7 9 hele 2 1 0 0 1 1 culi 3 3 1 4 9 4 tipu 7 2 2 0 6 3 elmi 7 13 7 3 4 9 chel 9 7 2 0 2 4 psep 2 0 3 1 1 2 cure 7 3 4 2 2 6 helo 9 2 6 5 2 4 nauc 4 1 0 3 3 2 meso 6 3 1 1 0 5 veli 0 2 1 1 2 0 gerr 3 7 1 1 4 2 sial 1 3 9 3 6 5 tubi 9 22 20 9 13 17 naid 9 17 5 12 6 11 plan 13 5 9 4 10 13 phys 4 4 8 0 3 3 unio 3 4 0 3 5 1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 155 Station 7 (Wet. season) 1977 1978 1979 7/16 7/23 8/21 6/02 6/11 8/23 7/03 hydr 0 0 0 0 0 0 0 trie 0 0 0 0 0 0 0 ephe 0 0 0 0 0 0 0 ephm 0 0 0 0 0 0 0 lept 0 0 0 0 0 0 0 amet 1 0 0 2 1 1 1 chir 4 1 1 0 2 2 4 hele 0 0 0 0 0 0 0 scim 000 000 0 elmi 0 0 0 0 0 0 0 helo 0 0 0 0 0 0 0 gerr 0 0 0 0 0 0 0 agri 0 0 0 0 0 0 0 gomp 1 0 1 2 1 0 1 pter 0 0 0 0 0 0 0 sial 0 0 0 0 0 0 0 tubi 4 10 8 11 7 4 5 naid 0 0 0 0 0 0 0 plan ' 2 2 1 0 1 0 1 lymn 0 0 0 0 0 0 0 unio 0 0 0 0 0 0 0 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 156 Station 7 (Dry season) 1978 1979 5/17 4/23 5/01 5/15 5/29 6/13 hydr 6 3 0 3 0 5 trie 9 7 11 4 3 4 ephe 6 3 0 1 6 1 ephm 13 5 4 5 8 7 lept 3 8 5 4 0 3 amet 3 1 0 0 4 3 chir 17 9 5 10 5 12 hele 7 1 1 3 0 6 scim 0 5 1 3 1 2 elmi 13 8 9 8 6 4 helo 12 5 4 5 2 4 gerr 5 2 0 3 0 1 agri 4 7 2 3 7 2 gomp 3 5 5 2 0 1 pter 7 3 4 4 6 0 sial 1 4 0 3 4 1 tubi 9 7 13 9 24 15 naid 3 5 9 7 7 3 plan 7 9 15 9 7 5 lymn 5 7 3 0 1 0 unio 2 5 5 0 2 1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 157 Station 8 (Wet season) 1977 1978 1979 7/17 7/24 8/21 6/02 6/11 8/23 7/03 7/20 hydr 0 0 0 0 0 0 0 0 hydo 0 0 0 0 0 0 0 0 trie 0 0 0 0 0 0 0 0 amet 2 3 0 1 1 4 3 1 chir 13 11 5 7 5 13 9 7 elmi 0 0 0 0 0 0 0 0 psep 0 0 0 0 0 0 0 0 helo 0 0 0 0 0 0 0 0 nauc 0 0 0 0 0 0 0 0 meso 0 0 0 0 0 0 0 0 hebr 0 0 0 0 0 0 0 0 agri 0 0 0 0 0 0 0 0 gomp 0 0 0 0 0 0 0 0 sial 0 0 0 0 0 0 0 0 tubi 13 7 9 5 6 11 7 13 plan 0 0 0 0 0 0 0 0 bulm 0 0 0 0 0 0 0 0 lymn 2 0 5 3 1 1 0 3 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 158 Station 8 (Dry season) 1978 1979 5/17 4/23 5/01 5/15 5/29 6/13 hydr 3 7 4 4 2 6 hydo 2 9 6 6 6 3 trie 6 3 0 0 5 4 amet 7 9 1.1 4 7 4 chir 27 9 11 17 21 9 elmi 14 5 3 9 7 3 psep 7 3 3 7 2 4 helo 3 1 0 4 2 1 nauc 6 3 1 0 3 5 meso l 0 4 4 1 3 hebr 1 0 0 3 1 0 agri 3 9 3 7 5 4 gomp 2 3 7 3 0 1 sial 7 6 3 3 1 4 tubi 11 17 9 7 15 9 plan 13 9 5 8 8 5 bulm 7 10 6 5 . 5 9 lymn 7 5 1 3 9 3 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPENDIX C DATA FOR PHYTOPLANKTON COLLECTED AT EACH STATION DURING BOTH SEASONS (GIVEN AS NUMBER OF ORGANISMS PER MILLILITER) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 160 anab = Anabaena peri Peridinium anac = Anacystis phac Phacus anki = Ankistrodesmus phor Phormidium asta = Astasia pinn Pinnularia aste = Asterionella poly Polysiphonia calo = Caloneis porp Porphyridium cera = Ceratium rivu Rivularia chla = Chlamydomonas seen Scenedesmus chlo = Chlorella spir Spirogyra clad = Chadophera stau Staurastrum clos = Closterium step Stephanodiscus cycl = Cyclotella stig Stigeoclonium cymb = Cymbella syne Synedra diat = Diatoma synu Synura ecto = Ectocarpus tabe Tabellaria eugl = Euglena trac Trachheloraonas eutr = Eutreptia trie Trichodesmium frag = Fragilaria ulot Ulothrix gomp = Gomphonema volv Volvox goms = Gompsopogon zygn Zygnema gymn = Gymnodinium lema = Lemanea lyng = Lyngbya melo = Melosira micr = Microcoleus mico = Microcystis navi = Navicula nedi = Nedium nitz = Nitzschia oedo = Oedogonium osci = Oscillatoria pand = Pandorina pedi Pediastrum Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 161 Station 1 (Wet season) 1977 1978 1979 7/02 7/19 8/06 5/27 6/03 8/05 6/29 7/16 osci 330 292 360 310 260 285 319 325 anab 49 64 43 52 53 47 55 47 phor 13 9 11 8 9 10 12 11 hyng 7 11 / 9 8 / 12 7 ulot 7 9 8 6 10 7 10 9 clad 13 / 9 / 7 5 12 / chlo 31 26 28 30 22 24 21 23 chla 7 13 9 6 9 10 7 11 stig / 12 / 5 7 / 5 17 nitz 9 7 7 6 8 7 6 9 navi / 4 3 / 2 4 / 2 frag 3 4 4 2 / / 3 3 aste 9 5 7 6 5 9 4 8 ecto 2 1 3 / 11 / 2 porp / 3 5 5 / 6 / 5 gymn 6 2 4 / 7 9 7 / eutr / 2 1 2 /I 2 1 phac // 3 2 / 4 4 / Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 162 Station 1 (Dry season) 1978 1979 5/05 4/20 4/28 5/11 5/25 6/OS osci 490 517 349 410 360 421 trie 31 43 41 36 39 32 anab 102 90 82 75 87 104 lyng 11 9 13 7 14 9 phor 7 13 11 5 10 8 ulot 17 13 10 / 9 15 chlo / 7 11 12 14 10 clad 11 7 5 9 8 / nitz 13 9 / 14 17 19 gomp 2 / 4 / 1 / navi 3 / 4 4 / 1 porp 9 6 / 7 4 / poly 2 4 2 / 1 2 peri / 3 1 2 / 5 cera 4 5 / 2 3 2 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 163 S ta tio n 2 (Wet season) 1977 1978 1979 7/02 7/19 8/06 5/27 6/04 8/12 6/29 7/16 gymn 13 9 12 / 17 / 13 / cera 9 6 5 11 / 7 9 6 peri 4 / 2 / 3 / 3 2 osci 198 170 176 186 169 152 191 166 anab 54 36 42 39 59 29 46 41 phor 11 13 7 / 5 11 8 7 nitz 33 23 29 31 34 25 21 33 navi 11 7 9 15 6 9 7 8 aste 2 / 4 3 / 4 / 3 porp 9 7 4 / 3 / 8 12 chlo 19 21 19 25 22 18 20 31 clad 12 17 / 13 9 7 / 12 stig 2 // 1 1 2 / / oedo / 5 7 / / 9 3 / volv / 19 / 17 / 11 // eutr 13 / 9 / 16 / 9 11 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 164 Station 2 (Dry season) 1978 1979 5/05 4/20 4/28 5/11 5/25 6/09 osci 410 402 368 397 371 404 anab 81 68 73 65 71 74 lyng 13 9 7 11 14 12 phor 11 / 9 13 17 12 micr 5 1 7 8 / 6 nitz 17 13 9 11 10 12 navi / 4 / 3 2 3 frag 4 2 4 / 3 / porp 11 17 / 12 13 / poly 13 7 9 7 / 12 chlo 23 27 32 29 34 29 chla 2 / 2 / 3 1 ulot / 3 / 7 5 4 eutr 5 3 / / 7 4 gymn 11 / 10 7 8 7 cera 7 4 2 5 / / peri / 2 / 4 5 3 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 165 S ta tio n 3 (Wet season) 1977 1978 1979 7/08 7/20 8/13 5/28 6/04 8/13 6/30 7/18 osci 16 23 29 31 18 24 23 23 anab 11 47 33 29 46 37 43 38 rivu 15 / 18 19 / 20 23 / chlo 131 174 164 123 143 149 132 147 seen / 2 4 / 4 / 7 9 ulot 19 9 11 7 13 6 14 9 anki 12 9 16 / 21 / / 8 volv 17 13 8 9 12 22 13 12 clos 24 17 13 26 15 19 20 18 navi 121 143 114 129 136 119 127 132 frag 57 29 37 49 43 44 41 44 nitz 101 86 91 81 95 93 87 94 pinn 2 1 / 3 / 1 2 / aste 6 2 / 4 3 6 / 2 phac / 3 1 / 2 / 1 2 cera 9 13 / 17 8 19 / 6 gymn / 9 13 / 14 / 11 7 goms 11 1 17 10 / 12 // Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 166 Station 3 (Dry season) 1978 1979 6/05 4/21 4/30 5/12 5/27 6/10 lyng 23 19 21 17 13 20 anab 17 13 17 19 23 15 osci 69 45 51 57 49 53 rivu / 13 12 9 21 / anac 17 9 11 15 / 7 chla 41 51 29 44 37 46 pedi 17 8 19 / 15 9 chlo 48 93 87 76 69 59 seen 9 7 11 4 9 / mico 12 / 11 19 17 / ulot 8 5 9 / 13 / clos 41 27 33 29 31 26 anki 17 9 21 13 26 19 pand 1 1 2 4 / / volv 23 29 14 10 18 9 stig 6 9 8 / 7 5 oedo / 7 3 5 2 2 zygn 4 // 2 1 1 spir 17 / 12 13 19 24 navi 90 79 89 86 98 75 step / 10 / 7 / 9 frag 85 69 73 76 68 63 aste 7 6 9 / 14 11 nitz 84 59 68 61 73 66 syne 4 8 / 6 / 5 pinn / 12 / 13 / 19 tabe 11 / 7 9 5 / melo 6 / 7 7 9 5 diat 9 11 / 4 6 7 phac / 3 7 // 2 eugl 3 4 6 / 5 2 cera 11 21 / 19 7 15 gymn 7 4 3 / 6 1 lema 13 12 9 16 11 7 goms 17 13 / 12 / 11 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Station 4 (Wet season) 1977 1978 1979 7/08 7/22 8/20 5/28 6/09 8/19 6/30 chla 109 92 97 84 89 86 95 vovl 41 19 28 17 34 25 31 spir 21 11 17 13 7 23 15 anki 19 9 / 11 9 / 13 ulot 79 39 59 48 69 54 57 clad 53 43 36 29 33 31 25 seen 36 21 29 41 17 19 23 chlo 93 76 104 82 89 91 87 clos 73 70 65 60 67 58 51 stig / 4 9 11 / 13 / zygn 22 19 21 / 10 15 11 phac 31 18 19 27 12 9 16 trac 9 / 5 / 9 / 7 asta / 6 / 9 / 5 / cera 31 19 21 24 17 26 12 gymn 13 8 10 15 8 9 12 navi 23 56 49 46 ■43 63 59 step 4 7 / 7 2 / 3 frag 133 131 126 119 103 115 109 syne 2 / 6 9 / 4 3 pinn / 17 13 10 19 / 5 melo 16 5 7 / 9 3 / aste 61 32 45 52 37 29 44 tabe ' 9 / 7 / 6 11 / osci 80 54 77 61 68 74 63 anab 53 31 27 36 41 29 51 anac 7 14 / 11 / 9 / rivu 13 17 7 9 11 15 5 lygn 9 8 15 11 7 17 10 lema 24 9 12 / 17 / 19 goms 19 10 17 13 21 7 ' 9 nitz 117 131 126 119 103 115 109 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Station 4 (Dry season) 1978 1979 5/12 4/21 4/30 5/12 5/27 6/10 chla 47 51 43 39 29 32 mico / 7 / 9 1 3 volv 103 81 87 95 93 86 spir 31 29 24 17 15 23 anki 29 27 49 34 43 38 oedo / 14 / 12 9 ulot / 9 15 12 11 18 7 stau 17 9 11 13 8 6 clad 13 29 9 15 32 17 seen 10 13 32 15 23 19 chlo 107 101 86 91 95 89 clos 76 71 63 69 81 stig 67 7 11 9 13 8 / zegn 12 9 13 7 11 9 phac 17 11 8 13 6 11 eugl / 9 13 / 15 7 trac 12 19 13 ’ 24 11 9 asta 2 / 1 1 2 / navi 130 98 102 114 107 110 step 7 11 9 8 17 10 frag 117 92 109 96 104 122 nitz 27 51 49 37 41 39 syne 3 2 / / 4 2 pinn 21 17 15 19 9 11 melo 27 21 11 17 7 19 cycl / 4 9 / 7 6 aste 1 1 2 / 1 tabe / 5 7 / 6 2 synu / 16 / 19 7 13 / osci 80 74 68 59 ■ 64 71 aban 41 39 35 49 52 33 anac 2 / 5 5 ’/ 3 rivu 2 4 / 3 1 / lyng 7 9 11 15 6 3 cera 34 17 27 15 29 ] 2 gymn 9 3 / 11 7 10 peri 5 4 11 6 9 2 lema / 12 5 / 9 / goms 7 9 3 11 5 7 porp 9 16 31 12 15 17 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Station 5 (Wet season) 1977 1978 1979 7/09 7/22 5/13 6/09 8/20 7/01 navi 121 112 106 113 131 109 step 63 39 41 47 59 34 syne 41 32 23 41 30 26 cycl 3 / 8 / 10 5 aste 21 19 15 11 12 23 calo 12 9 5 11 7 10 pinn / 7 / / 9 4 melo 40 29 22 31 39 27 frag 113 86 81 92 101 109 lyng 17 9 10 7 13 5 osci 107 83 93 79 97 101 anab 96 86 69 47 58 74 rivu 12 19 27 21 17 19 cera 24 17 19 11 12 18 gymn 9 21 27 11 20 15 spir 57 39 31 43 2.8 51 chlo 61 32 43 41 53 44 ulot 31 37 26 21 24 19 oedo 11 19 17 13 24 9 pedi 12 / 17 / 24 / anki 82 63 54 47 79 69 clos 81 47 65 72 57 66 zygn 17 9 12 15 7 13 mico ' / 3 / 9 10 / chla 134 129 119 124 107 113 goms 3 4 1 // 2 phac 15 7 11 9 13 10 trac 9 13 7 10 / 5 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 170 Station 5 (Dry season) 1978 1979 5/12 4/21 4/30 5/12 5/27 6/10 navi 161 153 139 154 142 131 step 13 20 24 16 11 17 syne 27 32 61 53 41 37 cycl 8 12 15 // 9 aste 17 14 77 14 9 / calo 15 21 // 16 24 diat 17 9 5 7 11 16 pinn 88 14 / 19 / 11 melo / 23 15 21 / / nedi 5 / 7 / 3 1 frag 23 17 15 9 11 13 cymb /// 9 8 / lygn 17 9 / 6 / 5 osci 121 142 131 115 127 152 anab 33 27 24 31 20 17 rivu 9 / 13 17 11 / cera 17 21 32 19 24 27 gymn 7 / 3 9 / 5 peri / 2 3 / 7 5 spir 48 52 43 41 29 32 chlo 119 155 139 142 148 129 ulot 16 / 13 / 9 18 oedo 12 21 19 18 27 16 pedi 14 9 17 5 / 3 anki 39 29 46 31 43 35 clos 37 53 44 41 33 35 zygn 7 6 / 9 13 8 stau 23 / 19 17 / 15 mico 13 11 // 9 5 chla 97 72 89 79 . 93 85 goras 6 4 / 3 3 / lema 4 / 9 7 ' 8 / phac 107 83 86 91 79 93 trac 3 5 2 2 3 4 asta / 2 2 / 1 / Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 170 Station 5 (Dry season) 1978 1979 5/12 4/21 4/30 5/12 5/27 6/10 navi 161 153 139 154 142 131 step 13 20 24 16 11 17 syne 27 32 61 53 41 37 cycl 8 12 15 // 9 aste 17 14 77 14 9 / calo 15 21 // 16 24 diat 17 9 5 7 11 16 pinn 88 14 / 19 / 11 melo / 23 15 21 // nedi 5 / 7 / 3 1 frag 23 17 15 9 11 13 cymb / / / 9 8 / lygn 17 9 / 6 / 5 osci 121 142 131 115 127 152 anab 33 27 24 31 20 17 rivu 9 / 13 17 11 / cera 17 21 32 19 24 27 gymn 7 / 3 9 / 5 peri / 2 3 / 7 5 spir 48 52 43 41 29 32 chlo 119 155 139 142 148 129 ulot 16 / 13 / 9 18 oedo 12 21 19 18 27 16 pedi 14 9 17 5 / 3 anki 39 29 46 31 43 35 clos 37 53 44 41 33 35 zygn 7 6 / 9 13 8 stau 23 / 19 17 / 15 mico 13 11 / / 9 5 chla 97 72 89 79 . 93 85 goras 6 4 / 3 3 / lema 4 / 9 7 • 8 / phac 107 83 86 91 79 93 trac 3 5 2 2 3 4 asta / 2 2 / 1 / Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 171 Station 6 (Wet season) 1977 1978 1979 7/10 7/23 8/20 5/31 6/10 8/20 7/01 7/18 osci 29 22 7 6 18 12 15 9 anab / / 17 11 / 7 22 / chlo 161 119 123 115 136 141 131 121 oedo 12 / 5 / 17 / 11 13 clos 7 5 / 9 / 2 / 2 ulot / 17 9 9 / 20 / 12 volv 14 9 21 / 8 / 3 6 chla 11 / 9 7 / 15 / 5 anki 9 7 / 15 / 4 10 3 stig 4 3 4 / 5 1 / / cera / 9 / 2 11 13 // navi 112 102 115 119 123 109 127 131 frag 21 12 9 26 H 21 16 14 pinn / 1 / 3 / 4 // tabe 7 9 / 2 // 6 / aste 23 12 9 / 15 / / 27 syne // 13 11 / 9 21 17 phac / 2 / 3 6 5 / 3 trac 8 / 9 11 / 7 / 22 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 172 Station 6 (Dry season) 1978 1979 5/14 4/22 4/30 5/14 5/28 6/12 osci 34 19 21 24 31 26 anab 14 29 26 • 19 33 17 anac 13 19 11 6 9 7 rivu 26 19 11 15 21 18 chlo 56 49 29 37 44 32 spir 29 24 43 39 32 34 clos 39 41 27 32 38 46 oedo 25 14 / // 13 ulot 11 9 / 13 17 / volv 14 11 6 / 17 / chla 93 91 109 87 97 82 stau 51 32 23 39 41 44 anki 19 17 11 7 9 13 zygn 12 7 9 14 5 7 mico 17 9 7 15 11 8 seen / 3 1 1 / 6 stig / 1 2 1 / 3 cera 17 9 1 21 / 8 gymn / 6 4 g 1 / navi 146 157 131 119 123 112 frag 127 101 97 121 . 109 113 diat 3 9 15 / 13 / pinn 9 / / 12 6 11 melo 17 / 9 11 / 12 cycl 1 / 2 // 2 tabe 9 7 / 5 / 13 aste / 5 4 3 / / syne / 3 / 7 9 / cymb 7 13 / 5 17 / goms / 19 19 / 15 / lema 2 / / 7 / 5 phac 102 86 74 92 '3 2 79 trac // 3 6 2 6 eugl 5 7 / 9 3 / asta 1 1 // / 3 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 173 Station 7 (Wet season) 1977 1978 1979 7/16 7/23 8/21 6/02 6/11 8/23 7/03 osci 70 76 64 53 57 63 61 anab 35 47 41 51 34 39 42 clos 37 24 19 32 27 18 44 chlo 78 85 104 92 76 97 89 ulot 18 6 22 14 9 7 8 volv / 3 / 1 6 / / stau / 12 / 16 26 / 8 spir 6 / 9 / 12 7 5 chla 46 29 31 42 37 34 40 navi 97 109 93 84 117 94 87 pinn / 1 1 / 2 2 1 melo 19 5 / 9 13 // aste 11 / 17 // 9 21 frag 69 67 61 41 59 77 65 phac 1 / 2 / 1 1 1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 174 Station 7 (Dry season) 1978 1979 5/17 4/23 5/01 5/15 5/29 6/13 osci 27 11 15 9 21 18 anab 5 11 / 13 8 17 rivu 3 / 6 7 2 / clos 23 19 13 17 9 21 chlo 73 63 72 82 59 81 volv 4 / 3 2 1 / seen / 7 4 / 9 11 ulot 9 7 / 13 11 4 stau 21 9 7 12 19 17 spir / 15 / 7 8 8 anki 12 9 13 16 5 19 chla 32 29 42 27 19 36 zygn 3 / 7 2 / 6 oedo 2 / 1 1 / 2 navi 99 93 85 74 88 79 syne 4 10 9 7 6 / pinn / 7 / 9 / 6 cycl 12 9 4 7 13 2 raelo 12 9 3 / 13 19 aste 10 4 3 9 7 11 frag 42 57 61 51 63 47 phac 4 11 9 11 17 6 trac 13 7 9 12 / 14 eugl / 6 9 / 12 7 goms 4 / 11 / 9 7 cera 27 21 11 13 19 24 gymn 17 9 6 11 13 9 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 175 Station 8 (Wet season) 1977 1978 1979 7/17 7/24 8/21 6/02 6/11 8/23 7/03 7/20 osci 63 36 47 55 39 41 52 46 anab / 19 / 26 / 9 / 15 stau 11 / 13 / 14 / 10 9 anki 15 21 15 19 23 31 18 12 chla 33 26 17 19 27 18 11 21 seen 34 8 5 7 3 1 4 / chlo 191 171 148 197 175 152 184 169 spir 6 / 2 4 / 9 ./ / volv 4 / 11 / 7 3 / / ulot 9 21 7 14 6 4 10 7 clos 22 12 / 4 / 9 / 16 navi 189 178 134 148 159 137 186 141 pinn 2 / 6 1 / 3 / 2 melo // 12 / 19 / 7 11 aste / 11 / 7 9 / 3 / frag 157 117 131 129 148 123 139 137 phac 1 / 2 / 11 2 / trac 3 1 / 2 /I / 2 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 176 Station 8 (Dry season) 1978 1979 5/17 4/23 5/01 5/15 5/29 6/13 osci 81 91 62 59 74 71 anab 4 17 11 19 9 6 rivu / 4 / 6 3 1 stau 31 24 19 17 11 13 anki 59 39 47 41 33 29 chla 36 43 46 52 39 61 seen 11 9 / 8 11 4 chlo 131 106 97 117 121 94 spir 7 / 19 / 21 6 volv / 2 7 6 / 5 clos 36 46 24 21 13 19 navi 121 97 106 110 91 113 pinn 12 9 17 5 6 9 melo 13 27 26 19 11 31 aste 11 13 31 27 / 19 ulot 7 / 9 / 13 18 frag 86 79 97 93 109 91 syne / 5 8 / 77 6 phac 4 9 3 / 7 2 trac 1 1 2 1 1 / cera 2 1 / 2 1 1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPENDIX D DATA FOR ZOOPLANKTON COLLECTED AT EACH STATION DURING BOTH SEASONS (GIVEN AS NUMBER OF ORGANISMS PER MILLILITER) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 178 Key: arce = Arcella amoe = Amoeba bodo = Bodo brae = Brachionus colp = Colpoda cycl = Cyclops daph = Daphnia diap = Diaphanosoma fili = Filinia fron = Frontonia kera = Keratella oiko = Oikomonas vort = Vorticella sten = Stentor Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 179 Date bodo oiko fili daph amoe vort (Wet season) 7/02/77 21 9 . . 1 • • 3 7/19/77 19 7 2 . . 3 8/06/77 23 9 . . 3 • • 7 5/27/78 27 11 3 . . 7 1 6/03/78 29 13 . . 1 • • 1 8/05/78 21 10 1 . . 3 6/29/79 24 8 . . 1 2 3 7/16/79 27 7 3 3 - • 1 (Dry season) 5/05/78 29 13 4/20/79 31 19 4/28/79 41 11 5/11/79 34 9 5/25/79 27 12 6/09/79 10 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 180 Station 2 Date bodo vort fron oiko daph fili amoe (Wet season) 7/02/77 19 5 . . 3 3 7/19/77 21 7 3 5 1 1 1 8/06/77 26 11 . . . . 1 3 . . 5/27/78 20 9 9 3 . . 2 1 6/04/78 17 7 . . 2 . . . . 1 8/12/78 18 6 3 . . 2 1 . . 6/29/79 30 8 6 1 3 . . 2 7/16/79 21 10 1 . . 2 1 . . (Dry season) 5/05/78 37 15 10 4 1 . . 2 4/20/79 32 9 . . 3 . . 3 1 4/28/79 40 11 7 . . 3 1 . . 5/11/79 36 17 5 1 1 . . 1 5/25/79 41 13 . . 2 . . 2 . . 6/09/79 25 8 3 1 2 . . 1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Station 3 Date fill brae kera colp vort cycl sten daph (Wet season) 7/08/77 7/20/77 8/13/77 5/28/78 9 6/04/78 11 8/13/78 10 6/30.79 14 7/18/79 7 (Dry season) 5/06/78 10 4/21/79 11 24 4/30/79 9 28 5/12/79 . . 32 5/27/79 7 29 6/10/79 13 17 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 7 /0 8 /7 7 7/22/77 8/20/77 5/28/78 6/09/78 8/19/78 6/30/79 3 (Dry season) 5/12/78 2 4/21/79 4/30/79 3 9 19 5/21/79 1 17 15 5/27/79 4 12 6/10/79 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Date kera sten brae vort oiko daph amoe cycl (Wet season) 7/09/77 7/22/77 5/31/78 6/09/78 8/20/78 7/01/79 (Dry season) 5/12/78 17 13 4/21/79 9 9 4/30/79 12 19 11 5/12/79 11 11 5/27/79 13 16 6/10/79 9 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Date brae sten amoe cycl arce kera diap (Wet season) 7/10/77 7/23/77 7 8/20/77 6 5/31/78 9 6/10/78 3 8/20/78 7 7/01/79 4 7/18/79 6 (Dry season) 5/14/78 11 4/22/79 17 4/30/79 7 5/14/79 11 5/28/79 16 4 6/12/79 21 9 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Station 7 Date diap brae cycl sten vort kera colp (Wet season) 7/15/77 . . 3 7/23/77 1 7 8/21/77 . . 1 6/02/78 . . 1 6/11/78 2 6 8/23/78 . . 3 7/03/79 1 (Dry season) 5/17/78 7 4/23/79 3 5/01/79 6 5/15/79 . . 5/29/79 3 10 6/13/79 4 19 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 186 Station 8 Date cycl vort brae diap colp amoe (Wet season) 7/17/77 . . 3 9 7/24/77 . . 0 3 1 8/21/77 . . 2 6/02/78 . . 0 6 1 6/11/78 . . 1 8/23/78 . . 4 6 2 7/03/79 . . 3 3 7/20/79 . . 1 7 1 (Dry season) 5/17/78 2 4 13 9 3 4/23/79 7 9 21 5 3 2 5/01/79 . . 2 24 8 2 5/15/79 3 7 17 12 1 2 5/29/79 4 6 19 5 6 6/13/79 6 9 23 6 1 1 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPENDIX E DATA FOR PLATE COUNTS OF TOTAL BACTERIA, TOTAL COLIFORM, AND YEAST/MOLD (GIVEN AS NUMBER OF COLONIES COUNTED) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 188 Station 1 Date Total Bacteria* Total Coliform* Yeast/Mold** (Wet season) 7/02/77 61 9 2 57 7 3 7/19/77 73 6 2 69 3 3 8/06/77 68 5 2 59 7 1 5/27/78 71 8 3 65 3 2 6/03/78 74 5 3 63 3 1 8/05/78 69 4 3 62 3 1 6/29/79 54 9 2 67 6 2 7/16/79 73 7 1 68 5 0 (Dry season) 5/05/78 54 7 1 39 5 1 4/20/79 47 4 2 42 7 1 4/28/79 46 6 0 37 3 2 5/11/79 43 4 1 37 7 0 5/25/79 51 5 3 57 3 1 6/09/79 42 4 1 56 3 2 *1:100 dilution. **1:10 dilution. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 189 Date Total Bacteria* Total Coliform* Yeast/Mold** (Wet season) 7/02/77 59 1 48 2 7/19/77 53 3 66 1 8/06/77 42 2 57 2 5/27/78 45 1 61 1 6/04/78 47 4 49 3 8/12/78 44 1 53 1 6/29/79 54 2 42 2 7/16/79 49 1 59 3 (Dry season) 5/05/78 23 1 39 0 4/20/79 44 2 51 1 4/28/79 36 1 42 2 4/11/79 27 3 39 1 5/25/79 42 2 47 1 6/09/79 42 2 29 2 *1:100 dilution. **1:10 dilution. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 190 Station 3 -Date Total Bacteria* Total Coliform* Yeast/Mold (Wet season) 7/08/77 131 2 3 107 4 1 7/20/77 146 7 5 121 6 2 8/13/77 117 3 1 133 2 2 5/28/78 119 1 3 131 7 1 6/04/78 121 4 2 103 3 1 8/13/78 107 3 2 123 2 2 6/30/79 124 1 4 137 2 2 7/18/79 133 3 1 121 6 3 (Dry season) 5/06/78 89 2 1 97 3 1 4/21/79 107 4 0 121 3 2 4/30/79 103 4 3 90 1 i 5/12/79 117 2 4 102 1 ' 2 5/27/79 93 5 1 109 2 1 6/10/79 124 3 2 112 1 3 *1:10 dilution. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 191 Station 4 Date Total Bacteria* Total Coliform* Yeast/Mold** (Wet season) 7/08/77 119 2 3 93 3 1 7/22/77 78 2 2 99 3 0 8/20/77 93 3 1 109 1 1 5/28/78 89 2 2 114 3 2 9/06/78 97 1 3 121 3 1 8/19/78 108 0 1 89 2 3 6/30/79 111 3 2 83 2 3 (Dry season) 5/12/78 91 2 2 99 1 0 4/21/79 87 1 1 73 1 0 4/30/79 79 1 2 91 2 3 5/12/79 89 0 2 81 2 0 5/27/79 73 1 1 79 2 1 6/10/79 77 2 2 84 1 1 *1:10 dilution. **1:100 dilution. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 192 Station 5 Date Total Bacteria* Total Coliform* Yeast/Mold (Wet season) 7/09/77 131 4 3 117 3 3 7/22/77 97 2 2 104 5 5 5/31/78 121 1 2 113 2 1 6/09/78 92 3 3 112 4 2 8/20/78 121 5 4 129 3 2 1/07/79 116 2 2 133 4 1 (Dry season) 5/12/78 112 5 1 121 3 0 4/21/79 87 2 3 94 1 1 4/30/79 117 3 0 93 1 2 5/12/79 83 2 4 89 1 3 5/27/79 109 3 2 98 2 2 6/10/79 106 2 1 88 1 3 *1:10 dilution. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 193 S t a t i o n 6 Date Total Bacteria* Total Coliform* Y e a s t/M o ld (Wet season) 7/10/77 146 5 4 129 7 3 7/23/77 127 8 6 131 3 1 8/20/77 146 4 3 133 2 2 5/31/78 119 3 4 134 3 2 6/10/78 126 9 4 139 6 1 8/20/78 147 5 3 130 7 2 1/07/79 142 3 4 129 2 3 7/18/79 131 4 5 139 7 2 (Dry season) 5/14/78 121 4 3 111 3 2 4/22/79 107 7 4 101 2 1 4/30/79 131 2 3 112 3 5 5/14/79 136 3 0 119 3 2 5/28/79 130 4 3 125 3 1 6/12/79 109 2 2 114 3 5 *1:10 dilution. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 194 Station 7 Date Total Bacteria* Total Coliform* Yeast/Mold (Wet season) 7/16/77 103 5 3 117 2 2 7/23/77 121 2 4 141 3 1 8/21/77 136 1 5 119 2 3 6/02/78 116 3 1 129 7 2 6/11/78 141 5 4 130 3 3 8/23/78 119 3 3 101 4 4 7/03/79 133 2 1 115 1 2 (Dry season) 5/17/78 89 3 1 106 1 3 4/23/79 111 0 1 103 2 2 5/01/79 97 3 0 114 4 2 5/15/79 89 3 1 97 5 1 5/29/79 120 4 3 112 1 1 6/13/79 95 2 3 109 3 2 *1:10 dilution. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 195 Station 8 Date Total Bacteria* Total Coliform* Yeast/Mold (Wet season) 7/17/77 151 7 6 139 6 7 7/24/77 157 3 5 136 7 3 8/21/77 129 5 2 147 2 5 6/02/78 127 3 7 133 7 9 6/11/78 152 6 3 125 8 6 8/23/78 146 4 4 153 7 3 7/03/79 119 4 2 137 3 5 7/20/79 124 3 4 132 2 7 (Dry season) 5/17/78 111 2 3 117 6 5 4/23/79 121 4 6 106 3 2 5/01/79 99 2 4 114 3 3 5/15/79 119 5 7 127 2 3 5/29/79 95 2 2 107 4 3 6/13/79 123 3 3 117 4 4 *1:10 dilution. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. APPENDIX F QUALITATIVE DATA FOR NEKTONIC FAUNA (GIVEN AS LISTING OF COMMON NAMES OF ORGANISMS) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 197 Station 1 Fishes: Catfish Shad Jewfish (mudfish) Bull shark Cichlids Nurse shark Sheepshead Hammerhead shark Snook Sawfish Tarpon Mullet Station 2 Fishes: Catfish Jewfish Mosquito fish Bull shark Cichlids Nurse shark Sheepshead Sawfish Snook Needle fish Tarpon Mullet Shad Arthropod: Stone crab Station 3 Fishes: Catfish Jewfish Baka Bull shark Mosquito fish Nurse shark Billiam Needle fish Cichlids Sawfish Sheepshead Red snapper Snook Mojarra Tarpon Grunts Shad Mullet Reptiles: Loggerheads Turtles (two kinds) Station 4 Fishes: Catfish Snook Mosquito fish Tarpon Billiam Shad Swordtail Jewfish Cichlids Red snapper Sheepshead Reptiles: Loggerhead Turtles (two kinds) Arthropods: Fresh-water lobster Stone crab Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 198 Station 5 Fishes: Catfish Swordtail Baka Cichlids Mosquito fish Snook Billiam Tarpon Reptiles: Loggerhead Turtles (two kinds) Arthropods: Stone crab Fresh-water lobster Station 6 Fishes: Catfish Swordtail Baka Cichlids Mosquito fish Snook Billiam Tarpon Reptiles: Loggerhead Turtles (two kinds) Arthropod: Fresh-water lobster Station 7 Fishes: Catfish Swordtail Baka Cichlids Mosquito fish Snook Billiam Tarpon Reptiles: Turtles (two kinds) Arthropods: Stone crab Fresh-water lobster Station 8 Fishes: Catfish Cichlids Baka Snook Mosquito fish Tarpon Billiam Reptiles: Turtles (two kinds) Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. BIBLIOGRAPHY 199 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. BIBLIOGRAPHY Aaronson, S. B . , De Angelis, 0. F., and Baker, H. 1971. Secretion of vitamins and amino acids into the environ ment by Ochromonas danica. J. Phycol. 7:215-18. Ahearn, D. G., Roth, F. J., and Meyers, S. P. 1968. Ecology and characterization of yeasts from aquatic regions of South Florida. Marine Biol. 1:291-308. Allen, L., Grindley, J., and Brooks, E. 1953. Some chemical and bacterial characteristics of bottom deposits from lakes and estuaries. J. Hyg♦ 51:105-94. Armitage, K. B. 1966. Distribution of riffle insects of the Firehole River, Wyoming. Hydrobiologia. 27:152-74. Barton, B. A. 1977. Short-term effects of highway construc tion on the limnology of a small stream in southern Ontario. Freshwater Biology. 7:99-108. Beadle, L. C. 1974. The inland waters of tropical Africa: An introduction to tropical limnology. New York: Longman. Bell, H. L. 1971. Effect of low pH on the survival and emergence of aquatic insects. Wat. Res. 5:313-19. Bishop, J. E. 1973. Observations on the vertical distribu tion of the benthos in a Malaysian stream. Freshwater Biology. 3:147-56. Bjornn, T. C., Brusven, M. A., Molnau, M. P., Milligan, J. II., Klamt, R. A., Chacho, E., and Schaye, C. 1977. Trans port of granitic sediment in streams and its effect on insects and fishes (Bull. No. 17). Moscow: University of Idaho, Forest, Wildlife and Range Experiment Station. Block, E. M., and Goodnight, C. J. 1972. A new species of tubificid oligochaete from Central America, Limnodrilus bulbiphallus n. sp. Trans. Amer. Micros. Soc. 91(4): 579-85. Blum, J. L. 1956. The ecology of river algae. Bot. Rev. 22:291-341. ______. 1960. Algae populations in flowing waters. Spec. Pubis. Pymatuning Lab. Fid. Biol. 2:11-21. 200 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 0 1 Bold, H. C., and Wynne, M. J. 1978. Introduction to the algae. Englewood Cliffs, N.J.: Prentice-Hall. Brasfield, H. 1972. Environmental factors correlated with size of bacterial populations in a polluted stream. Appl. Microbiol. 24:349-52. Brook, A. J . , and Rzoska, J. 1954. The influence of the Zebel Aulyia Dam on the development of Nile plankton. J. Anim. Ecol. 23:101-14. Brown, D. S. 1961. The food of the larvae of Choeon dipterum L. and Baetis rhondani (Pictet) (Insecta, Ephemeroptera). J. Anim. Ecol. 30:55-75. Butcher, R. W. 1964. Studies on the ecology of rivers. VII. The algae of organically enriched water. J. Ecol. 35:186-91. Cain, A. J. 1969. Speciation in tropical environments: Summing up. Biol. J. Linn. Soc. 1:233-36. Cairns, J., Jr. 1967. The use of quality control techniques in the management of aquatic ecosystems. Wat. Resour. Bull. 3:47-53. ______, and Dickson, K. L. 1971. A simple method for the biological assessment of the effects of waste discharge on aquatic bottom-dwelling organisms. J. Wat. Pollut. Control Fed. 43: 755-72. CBA Engineering Ltd. 1971. Belize City prefeasibility study: Water supply and sewerage, vol. 2 (Report No. 718). Vancouver, Canada: CIDA. Chapman, V. J. 1961. The marine algae of Jamaica. Part I. Myrophaceae and Chlorophyceae. Bull. Inst. Jamaica, sci. ser. 12(2). ______. 1963. The marine algae of Jamaica. Part II. Phaeophyceae and Rhodophyceae. Bull. Inst. Jamaica, sci. ser. 12(2). Chu, F. H. 1949. How to know the immature insects. Dubuque, la.: Wm. C. Brown. Cloern, J. E. 1977. Effects of light intensity and tempera ture on Cryptomonas ovata (Crytophyceae) growth and nutrient uptake rates. J. Phycol. 13:389-95. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 2 0 2 Coleman, M. J. , and Hynes, H. B. N. 1970. The vertical dis tribution of the invertebrate fauna in the bed of a stream. Limnol. Qceanogr. 15:31-40. Cooke, W. B. 1961. Pollution effects on the fungus popula tion of a stream. Ecology. 42:1-18. Cummins, K. W. 1966. A review of stream ecology with special emphasis on organism substrate relationships. Spec. Pubis. Pymatuning Lab. Fid. Biol. 4:2-51. ______. 1973. Trophic relation of aquatic insects. Annual Review of Entomology. 18:183-206. ______, and Lauff, G. H. 1969. The influence of substrate particle size on the microdistribution of stream macro benthos. Hydrobiologia. 34:145-81. Curtis, E. J. C., and Harrington, D. W. 1970. Effects of organic wastes on rivers. Process Biochemistry. 5:44-46. Dobzhansky, T. 1959. Evolution in the tropics. Am. Sci. 38:209-21. Down, C. G. 1978. Environmental impact of mining. Essex, England: Applied Science Publishers Ltd. Drouet, F. 1959. Myxothyceae. Fresh-water biology (2nd ed.). Edited by W. T. Edmondson. New York: John Wiley & Sons. Duchrow, R. M. 1977. The effects of barite tailings pond dam failure upon the water quality of Mill Creek and Gib River, Washington County, Missouri. Missouri Department of Conservation. Eddy, S. 1934. A study of fresh-water plankton communities. Illinois Biol. Monographs. 12:1-93. Edmondson, W. T . , ed. 1959. Fresh-water biology (2nd ed.). New York: John Wiley & Sons. 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