Indicator Bacteria (Escherichia coli):The presence of E. coli bacteria is an indicator of sewage inputs, suggesting that other pathogens may also be present. By tracking E. coli bacteria, Harbor Watch can identify point sources of pollution input. Typical culprits are illegal sewage hookups, leaking septic systems, and aging infrastructure.
Dissolved Oxygen: DO is a measurement of the amount of oxygen present in the water. DO can be an indicator of the health of a water body because without oxygen, most organisms cannot survive. Oxygen levels are effected by water temperature (colder water can hold more oxygen), flow (the faster the flow, the greater the chance of oxygen becoming trapped in the water), and the presence of decomposing material (decomposition depletes oxygen). The State of Connecticut Department of Energy and Environmental Protection criteria state that dissolved oxygen levels should not fall below 5 mg/L in a healthy water body.
Conductivity: Conductivity is the measurement of an electrical current passing through water, which is related to the presence of dissolved solids in water and is strongly correlated with salinity. Most organisms are highly sensitive to fluctuations in salinity, so changes in conductivity in an ecosystem can be indicative of stressors on the biological community.
Temperature: Since many aquatic and marine organisms have narrow ranges of temperature preference, monitoring of water temperature helps us to understand changes in species composition of the community over time. Unusual temperature observations can also indicate a sewage pollution source nearby.
pH: The pH of a fluid is measured on a 14-point scale, where pure water has a pH of 7. pH is related to the concentration of hydrogen ions present in the water, with a higher concentration relative to hydroxide ions indicating more acidic water. pH can impact multiple processes, both chemical and biological. Species’ tolerances for different pH levels vary. For example, shellfish who build calcium carbonate shells are highly sensitive to changes in pH.
Turbidity: Used to measure turbidity (or the clarity of water), secchi discs are a simple way to measure the depth at which light can penetrate through the water. Turbidity can be an important factor because when there are high levels of sediment in the water, organisms that require sunlight to live may not be able to survive.
Benthic Fish Community: Trawling for juvenile benthic marine fish allows Harbor Watch to collect species abundance and richness data on the harbor. These species are critical to the food chain and their presence is indicative of harbor health.
Nutrients: We also conduct measurements of nutrients such as chlorine, iron, nitrogen and phosphorous, which can be indicators of a variety human influences.