Why go water sampling?

It seems that many of my blog posts are not only the result of my experiences at the Charles River Watershed Association (CRWA), but also conversations with my friends about my internship at CRWA. While my first friend-inspired post resulted in five fun facts about the Charles River, this post focuses on the water sampling project that Cait, Bruce, and I will be working on throughout the summer. Our aim is to collect data that will help CRWA understand how invasive water chestnuts are affecting the river.

After trying to explain to my friend, Will, what my work entails I realized that I was doing to him exactly what I did on the blog; I wrote the what and how of water sampling with the hydrolab and that important to us are pH, conductivity, dissolved oxygen (DO), temperature, and phycocyanin levels; however, I never explained why!

Thus, here are the parameters I listed, and a little information about them:


pH scale (courtesy of Creative Commons)

pH - is a measurement of acidity or alkalinity (base). Measured on a scale of 0.0 to 14.0, neutral water is 7.0 and acid rain is around 5.6.

Changes in pH can indicate pollution from factors such as atmospheric deposition (acid rain), wastewater discharge (sewage overflows, industrial waste), and degradation of surrounding rock. Levels can also be influenced by surrounding soil and flora.

Most aquatic life has adapted to a certain level pH so levels on either extreme of the spectra are deadly for fish and other aquatic organisms. Eggs, young fish, and amphibians are especially sensitive to low pH.

pH can also affect behavior of other chemicals in the water, so changes in acidity or basicity may cause heavy metals to dissolve and become more toxic.

Recommended freshwater level for aquatic life is 6.5-9.0 (Environmental Protection Agency).

Conductivity (specific conductance) - is an estimate of the ion concentration, essentially the total dissolved solid (TDS, mainly salt). Measures the ability of water to pass an electrical current.

Conductivity gives indication to the presence of inorganic dissolved solids such as chloride, sulfate, sodium, calcium and others. It is also directly affected by the surrounding geology. Granite bedrock will lower conductivity, while limestone and clay will increase conductivity.

Changes in conductivity can indicate groundwater input or pollution from factors such as wastewater discharge (sewage overflows, industrial waste, urban runoff - especially in the winter from road salt, agricultural runoff). High water temperature results in higher conductivity, as well as dry periods and low flow conditions.

 Recommended conductivity level for aquatic life is 150 to 500 µS/cm (FOSC). 

DO requirements for aquatic life (courtesy of
Integration and Application Network, University 
of Maryland Center for Environmental Science)

Dissolved oxygen (DO) - measures the amount of oxygen dissolved in water.

DO is dependent on temperature and salinity. Colder water can hold more DO, more saline can hold less DO.

Plants and animals can not use the oxygen in water (H2O) and thus depend on the dissolved oxygen (O2) for respiration.

In the Charles River a big problem are the invasive water chestnuts. Though dissolved oxygen is produced through plant photosynthesis, large mats of water chestnut consume more oxygen than they produce and dead plant decomposition requires DO; this results in stress for native species that must compete with the invasives for resources.

Included in the chart to the left is oxygen requirement for American shad, a fish species recently restored to the Charles!

Recommended DO level for aquatic life is 5.0 mg/L or above (EPA).

Temperature - I think this is self-explanatory...

Temperature is important because aquatic life depends on temperature. Organisms are accustomed to certain temperatures and temperature has an impact on many other parameters and is affected by factors such as weather conditions and pollution.

Phycocyanin - is a blue pigment attached to photosynthetic membranes. Present in cyanobacteria and can be an indicator for cyanobacteria presence and concentration.

Cyanobacteria levels, also known as blue-green algae (but not an algae!), are important to measure because exposure can have direct human health effects. In abundance, cyanobacteria also prevents light and oxygen from penetrating the surface of the water, resulting in negative effects on other aquatic life.

Changes in cyanobacteria levels, for example, severe algae blooms, can be caused by factors such as rainstorms that bring nutrients to the river from sewer overflows, etc, by other pollution, or by warm temperatures.

During the summer, when bacteria levels are especially high, CRWA runs a daily flagging program.

Recommended cyanobacteria level to prevent adverse human health effects is 70,000 cells/mL or below (Massachussets Department of Public Health). 

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So Will, and any other readers, I hope this was informative and helps you to understand our work a little better!

Check out the CRWA water quality monitoring page  if you're interested in learning about some of the other parameters CRWA occasionally tests for such as ammonia, fecal coliform, and nitrates, and why they are so important.

Stay sunny!
- Ingrid