Water Quality Analysis & Visualization

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Parameters

Nitrogen

As more people occupy coastal watersheds, the associated coastal waters receive increasing pollutant loads. Coastal embayments throughout the Commonwealth of Massachusetts are becoming nutrient-enriched. The primary nutrient causing the increasing impairment of our coastal embayments is nitrogen, with its primary sources being wastewater disposal, and non-point source runoff that carries nitrogen (e.g., fertilizers) from a range of other sources.

Explore Nitrogen:

Go to the interface and select:

1. a time period (e.g. 2016)
2. an embayment (e.g. Nantucket Harbor)
3. total nitrogen (TN)

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Phosphorus

Phosphorous is the limiting nutrient in freshwater systems and an important driver of harmful algal blooms of cyanobacteria (CyanoHAB). Phosphorous comes from detergent use, the weathering of rocks, streams, wastewater and fertilizer.

Explore Phosphorus:

Go to the interface and select:

1. a time period (e.g. 2016)
2. an embayment (e.g. Nantucket Harbor)
3. total phosphorus (TP)

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Dissolved Oxygen

Dissolved oxygen (DO) is the amount of oxygen in the water. Oxygen is needed to support aquatic animal and plant life. Low levels of oxygen (hypoxia) or no oxygen levels (anoxia) can occur when algal blooms are decomposed by microorganisms. During this decomposition process, DO in the water is consumed. Additionally, nutrients (and other pollutants) can be released from sediments at low oxygen conditions thus exacerbating problems.

Explore Dissolved Oxygen:

Go to the interface and select:

1. a time period (e.g. 2016)
2. an embayment (e.g. Nantucket Harbor)
3. dissolved oxygen (DO)

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Temperature & Salinity

Salinity is the dissolved salt content of a body of water. Salinity, along with temperature and pressure, helps govern physical characteristics of water such as density and heat capacity. Water temperature and salinity are two important physical properties of the marine environment, influencing many physical, chemical, and biological processes (metabolic processes, photosynthesis). Salinity and temperature also dictate the species and abundance of marine animals and plants, making them high-priority parameters to monitor as changing levels of salinity can impact aquatic organisms that are adapted to certain salinity concentrations.

Explore Temperature or Salinity:

Go to the interface and select:

1. a time period (e.g. 2016)
2. an embayment (e.g. Nantucket Harbor)
3. water temperature (wtemp) or field salinity

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Turbidity / Water Clarity

Turbidity is a measure of water clarity. Water clarity is a measure of material suspended in the water column and how far down light can penetrate through the water column.

High levels of turbidity can result from urban runoff, waste discharge, dredging, and boating, as well 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 (i.e., eelgrass) and animals. Clearer water allows for more sunlight to reach submerged aquatic vegetation, producing more oxygen in the water and providing habitat for fish and shellfish.

Explore Turbidity / Water Clarity:

Go to the interface and select:

1. a time period (e.g. 2016)
2. an embayment (e.g. Nantucket Harbor)
3. secchi average

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Chlorophyll a

Chlorophyll a is a green photosynthetic pigment found in most phytoplankton. Monitoring Chlorophyll a is a way to measure the amount of algae growing in the water. High chlorophyll levels are often a sign of nitrogen pollution. An excess of algae can negatively impact a waterbody causing green scums and foul odors and can result in decreased levels of dissolved oxygen. Waters with high levels of nutrients from fertilizers, septic systems, and urban runoff tend to have higher concentrations of chlorophyll a and excess amounts of algae.

Explore Chlorophyll a:

Go to the interface and select:

1. a time period (e.g. 2016)
2. an embayment (e.g. Nantucket Harbor)
3. chlorophyll a (chl-a)

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pH

pH is a scale used to specify how acidic or basic a solution is. In aquatic systems, a large variety of animals prefer a range of 6.5-8.0. A pH outside this range can stress the physiological systems of most organisms and can negatively impact reproduction. Low pH can also allow toxic elements and compounds to become mobile and “available” for uptake by aquatic plants and animals. Changes in acidity can be caused by atmospheric deposition (acid rain), surrounding rock, and certain wastewater discharges.

Explore pH:

Go to the interface and select:

1. a time period (e.g. 2016)
2. an embayment (e.g. Nantucket Harbor)
3. pH

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Metrics

Total Maximum Daily Load (TMDL)

The Massachusetts Department of Environmental Protection (MassDEP) finalized a nitrogen Total Maximum Daily Load (TMDL) for several embayments on Nantucket that established nitrogen limits/thresholds to restore water and habitat quality throughout the system. The TMDL is a regulatory limit required under the federal Clean Water Act for all surface waters that are impaired and failing to meet state standards.

The TMDL value for an embayment appears in the plot area whenever nitrogen is queried.

TMDL Limits for Embayments

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Trophic Health Index Score

The trophic state of an estuary is a quantitative indicator of its nutrient-related ecological health and is based on key ecological metrics: concentrations of inorganic and organic nitrogen, water clarity (secchi depth), lowest measured concentrations of dissolved oxygen (average of lowest 20% of summer measurements), and chlorophyll-a pigments (surrogate for phytoplankton biomass/blooms). Nutrient-related trophic health scales generally range from oligotrophic (healthy-low nutrient) to mesotrophic (showing some signs of deterioration of health due to nutrient enrichment) to eutrophic (habitats significantly impaired and degraded, high levels of nutrients and organic matter and community shifts). The Trophic Health Index Score used here is a standard numerical scale based on criteria for open water embayments and uses the above mentioned measured parameters to create a habitat quality scale (Howes et al. 1999).

Howes, B.L., Williams, T., Rasmussen, M. 1999. Baywatchers II: Nutrient related water quality of Buzzards Bay embayments: a synthesis of Baywatchers monitoring 1992-1998. The Coalition for Buzzards Bay. 150pp.

Explore Trophic Health Index Score:

Go to the interface and select:

1. a time period (e.g. 2016)
2. an embayment (e.g. Nantucket Harbor)
3. Trophic Health Index Score (with or without DO)

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Learn more about Buzzards Bay Coalition