Local students monitor water quality in the Osa

by Pilar Bernal, Environmental Education and Community Outreach Program Manager


Local students perform tests to measure water quality of streams in the Osa.


Osa’s Ant Defenders, an environmental club composed of 15 fourth grade students from the Saturnino Cedeño School in Puerto Jiménez, have started a program to monitor the water quality of Osa’s waterways this past November – starting with Quebrada la Ignacia, a stream that passes through town. These students will be analyzing the physical, chemical, and biological characteristics of the stream once a month.



With the help of Allegheny College in Pennsylvania and its program Creek Connections, Osa’s Ant Defenders will have the opportunity to perform chemical tests such as levels of dissolved oxygen, nitrates, phosphates, pH and alkalinity, and biological tests of coliform bacteria and aquatic macroinvertebrates. With the results of these tests, it’s possible to analyze the stream’s water quality, its changes over time, and possible sources of contamination that are affecting it. Here are the results from our first test on November 8:

Test Result
Temperature 79.7 degrees Fahrenheit
pH 8.15
Dissolved solids 140 mg / mL
Dissolved oxygen levels 7 mg / mL
Nitrates 0 mg / mL
Phosphates 0.025 mg  / mL
Total Alkalinity 85 mg / mL
Turbidity 25.5 JTU
Coliform bacteria 382.8 NMP / 100 mL

These results show favorable conditions for aquatic life in Quebrada la Ignacia. Nevertheless, the level of phosphates and the presence of coliform bacteria in the water reveals possible contamination from domestic wastewater in the stream. With the help of Osa Conservation, these students will continue to monitor the water quality of the stream and see how these values change in the coming months. The results will also be reported to our environmental board, with the goal of educating the community about the quality of its water sources and the importance of their conservation.


Osa Conservation
[email protected]
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