Diana Getty, William Mills,  Amy O’Donnell, Melanie Revere, James Whelan.
 

INTRODUCTION

The demand for potable water is rising in direct proportion with the rise of the world’s population. The increase in human use of freshwater has drastically altered aquatic ecosystems and interrupted watersheds and wetland filtration systems. The demand for drinking water is not the only stress placed on aquatic ecosystems. Agricultural runoff, acid rain, industrial waste and fecal matter pollute freshwater systems worldwide.

Scientists are searching for ways to clean up watersheds all over the world. Though these emergencies are addressed  locally, the problem is global in nature. Some efforts are directed at finding alternatives to our current water supply such as purifying ocean water. Conservation efforts are being directed at freshwater systems in an effort to preserve aquatic species. Unfortunately, the problem is complicated and a simple solution is not in sight.

San Vito is a small town in Costa Rica in the Coto Brus region.  The local inhabitants were forced to locate an alternative water source when their local river, the Rio Jaba, became too polluted for human consumption.  They now rely on an aquifer containing water brought in from a nearby mountain source.  The inhabitants of San Vito are also currently using septic tanks to contain their wastewater.  It would seem with these steps that the river would eventually became clean again, but that is not the case.  There are still industries in town that use the river for a dumping ground.  Locals complain that the slaughterhouse dumps its organic wastes directly into the stream, causing it to “flow red”.  (Tomasovich, 1998)

We believe that urban runoff is the reason for continued water pollution problems in this town.  We want to find out to what extent biota and water chemistry change as the stream flows through this urban environment.  We believe that the composition of the biota will decrease in diversity after the Rio Jaba has passed through the town of San Vito.  We also believe that the chemistry will be altered, showing an increase in nitrogen, phosphate, and suspended particulates while the dissolved oxygen and the pH will decrease.
 

METHODS

The Rio Jaba was selected because of the activity on the river and locale.  The human activities include an urban community of 50,000 people, a slaughterhouse, coffee plant, and cement plant.  A topographic map was used for choosing the sites. The first site was chosen because the stream flowed through forest with minimal human impact.  It was 200 meters north of the slaughterhouse and above the town of San Vito,.  The second site was 2000 meters downstream of the town, slaughterhouse, coffee plant, and cement plant.

Abiotic Sampling Procedures
   1. Collection
     a.  The stream quality was tested by using a Hock Surface Water Testing Kit, the focus was towards DO (dissolved oxygen), pH, phosphates,
            nitrates, and temperature.  The testing was conducted on site.
     b.  Stream velocity was measured at each site. This was achieved by measuring the amount of time an orange took to float for a ten meter length
            of river. The test was repeated three times at each site and an average was taken.
     c.  Water was collected in two 950 ml ball jars to take back to the lab to test for turbidity.
   2. Examination
     d.  The chemical tests that were collected were compared to EPA water quality standards.(EPA Standards)
     e.  The water samples were filtered and the sediment was removed by using nylon mesh.  The mesh was weighed before and after the filtration process
            on an OHAUS electronic scale.

Biotic Sampling Procedures

1. Collection
    a.  Six substrate samples were randomly collected from the stream bottom across the study area for each site.  Submerged rock and plant materials
           were placed in plastic bags for microscopic examination.
    b.  Two standard aquatic sweep nets were used to survey for macro-invertebrates.  The survey was conducted by sweeping the study area for three
           minutes with each net.
2. Examination
    c.  The two sweeps for macro-invertebrates were examined in the field.  Each sample collected was examined by eye and using a hand lens for visible
          organisms.  All visible organisms were sorted, counted and a type sample was collected for each.
    d.  The six substrate samples were observed using a stereoscope.  All observed invertebrates were identified and counted.  Two slides were
          prepared from each site for microscopic examination.  Three fields were randomly selected from each slide for analysis.  Each field was observed
          and all organisms were counted.  For all counts the following relative abundance scale was used:  0 = none; 1 = 1 to 3 organisms observed; 2 = 4 to
          10 organisms observed; 3 = greater than 10 organisms observed.
 

RESULTS
Clean water standard Site 1 Site 2
pH 6.5 - 8.5 6.5 6.5
Phosphates 1 PPM 0 6 PPM
Nitrates 10 PPM 4 PPM 0
Dissolved Oxygen greater than 4 PPM 4.2 PPM 3.8 PPM

Stream flow for each site:
? Site 1 width 8.8 m, Av. Depth 0.32 m and velocity 0.6 m/sec. Sediments 0.001 g/ml  Water Temp. 180 C
? Site 2 width 8.8m. Av. Depth 0.40 m and velocity 0.7 m/sec. Sediments 0.03 g/ml Water Temp. 220 C

Biotic Survey using relative abundance scale

Organism Site 1 Site 2
Chirnomid larvae 3 2
Simuliidae larvae 2 1
Coleopetra larvae 0 1
Hygrobiidae larvae 0 1
Hemipterin adults 2 0
Coleopteran adults 2 1
Dolichopodidae larvae 1 0
Trichoptera, non-tube type larvae 2 0
Rhyacophlidae larvae 1 0
Plecoptera larvae 2 0
Water mites 1 0
Nematodes 1 0
Water molds 0 3
Moss 2 0
Flagellates 1 3
Diatoms 3 1
Green Algae 3 0
Blue green algae 3 1
Abundance number total 29 14
Total number of groups present 16 10
 

Discussion

Site one was a clear flowing stream with mats of algae and moss covering the submerged rocks. It was visually pleasing. All of the abiotic factors were within the Clean Water Standards.(EPA Standards)  It appeared to be a clean, free flowing mountain stream. Much of the stream was covered with forest canopy keeping it cool.

Site two was completely different. There was a strong organic chemical odor.  The water was a cloudy-gray color. The bottom was covered with a gray slime. The dissolved oxygen level was below the freshwater standard for sustaining fish.  Phosphates were six times higher than the Clean Water Standard.  The accuracy of these numbers is dubious, as the chemicals available to test dissolved oxygen and phosphates were past their expiration dates. Water temperature was four degrees higher than Site one, probably due to the lack of canopy cover over the stream.  Our findings indicate the San Vito community has caused significant changes to the water quality of the Rio Jaba.
 

Analysis of the organisms found:

Comparing the two sites, a greater abundance of organisms and a higher level of diversity was found at Site 1. The analysis of samples from Site one yielded sixteen different groups, whereas only ten groups were identified from Site 2 samples. Organisms such as Chirnomid larvae and Simuliidae larvae (both Diptera), Flagellates and diatoms were found at both locations, though all types were more abundant at Site 1. Interestingly, crustaceans, rotifers, and ciliates were missing from the samples from both locations.
 

Site 2 was overrun with a fibrous water mold which clung to the rocks and fallen leaves on the streambed. This fungal mat caught sediments creating a thick undulating layer of slime. Mosses, and algae were virtually absent from Site 2. These missing food sources may be partly responsible for the absence of animal groups found upstream.
 
 

Causes and Global Implications

A slaughterhouse, coffee processing plant and cement manufacturer are all located within one kilometer of each other along the Rio Jaba. According to some of the locals, the slaughterhouse causes the river to flow red when in operation. Green leakage has also been witnessed leaving the slaughterhouse and entering the water.

The coffee plant has been seen discharging pulp and waste water. This kind of dumping is illegal, though Tomasovich (1998) has noted this is done. The cement plant is also responsible for adding silt and sediment to the river.

Our findings indicate that these pollution sources are affecting the biota of the stream.  Even though some of the contaminates are organic in nature, the huge volume released will drastically impact the local watershed as well as other areas.  Additional studies in this area and at other sites down river should be conducted.  Small cities, such as San Vito, are common all over Central America and controls to inhibit the amount of pollutants entering watersheds are usually not very sophisticated enough or, most likely, non-existent.  This problem is not uncommon throughout the world and the exponential effect will continue to pollute waterways all over the world.  Solutions could range from using organic wastewater systems (such as marshlands) to government funded water treatment facilities in communities in third world countries.
 
 

Classroom Connections

Everyone lives in a watershed and everyone depends on the local waters for one reason or another.  Conducting tests of surface and ground water in local communities will enhance the understanding of how important water quality is to humans as well as the organisms which depend on clean water.   Establishing a relationship and communicating with businesses and facilities that effect the cleanliness of local water areas will further assist students in understanding the importance of clean water.
 
 

Literature Cited

EPA Standards:  website:  www.epa.gov

Tomasovich, S., (1998)  A physical and chemical comparison of three point-source pollution sites along the Rio Jaba in Coto Brus, Cost Rica.  UCEAP Las Cruces.