Water Quality Parameters


Key in this study will be to map out the spatial and temporal variability in nutrient fluxes in the bay, focusing specifically on nitrogen and phosphorous. In this program we test for Dissolved Inorganic Nutrients (nitrate/nitrite, ortho-phosphate, ammonia, and silicate) and Total Nutrients (total nitrogen and total phosphate).

The measurement of nitrogen is a key component of the Center for Coastal Studies water quality monitoring program. Samples from surface and bottom waters are analyzed for several different nitrogen compounds including nitrate+nitrite, ammonia and total nitrogen. Most of the nitrogen that enters coastal waters on Cape Cod is from anthropogenic (human) inputs and is in the form of dissolved inorganic nitrogen (DIN) such as ammonia, nitrate and nitrite. These inputs originate primarily from wastewater, runoff and atmospheric deposition. Dissolved inorganic forms of nitrogen are biologically available for uptake by primary producers such as algae and phytoplankton. Excessive amounts of these forms of nitrogen entering our waters are behind most major problems affecting coastal ecosystems, such as eutrophication, phytoplankton blooms and hypoxia (low oxygen). It is therefore important that we establish baseline data for these waters and continue to closely monitor nutrient levels to address existing and imminent problems.

Chlorophyll a

Chlorophyll a is a green photosynthetic pigment found in most phytoplankton and plant cells. It is a commonly measured parameter of water quality as it can be used as an estimate of the amount of organic matter produced within the bay. By keeping tract of trends in chlorophyll a, we are able to assess effects of nutrients entering the bay and better understand the delicate balance between photosynthetic rates, nutrient inputs, and oxygen levels in our bay waters.

Dissolved Oxygen

Dissolved oxygen concentrations are a measure of how well the water is aerated. This parameter is one of the best and most immediate indicators of a system’s health (EPA). Because oxygen is needed to support animal and plant life, consequences of declining D.O. levels will set in quickly. This immediate impact on plant and animal life makes measuring the level of oxygen an important means of assessing water quality. Additionally, at low oxygen conditions, nutrients (and other pollutants) will be released from sediments thereby exacerbating problems.

Temperature and Salinity 

A CTD is deployed to measure temperature, salinity and depth.

A CTD is deployed to measure temperature, salinity and depth.

Water temperature and salinity are two of the most important physical properties of the marine environment, influencing many physical (density), chemical (capacity to hold D.O., sensitivity to toxic wastes), and biological processes (metabolic processes, photosynthesis) as well as dictating the types, distribution and abundance of marine flora and fauna. Monitoring levels of these properties, and more importantly, changes in the levels, will provide a direct indication of potential problems.






Turbidity, a measure of water clarity or how much the material suspended in the water column decreases light penetration, will also be measured as an indicator of the quality of the water in the bay. High levels of turbidity can result from anthropogenic disturbances such as urban runoff, waste discharge, dredging, and boating, as well as natural disturbances such as storms, wave action, and bottom feeding animals. Highly turbid waters are detrimental to the entire ecosystem from sediment quality, to water chemistry, to the survival of plants and animals. Some of the associated negative impacts of high levels of turbidity include lowering the rates of photosynthesis, smothering benthic organisms, and altering bottom material and sediment size.

A Secchi disk is used to measure turbidity (water clarity).

A Secchi disk is used to measure turbidity (water clarity).


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