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Water Quality Monitoring Program

Devereux Slough

The biological trends of fish and invertebrates in the Devereux Slough can often be attributed to physical and chemical properties of the water. For example, when the mouth is open to tidal influence, the slough may see more marine species that prefer salty water. The goal of the Devereux Slough Monitoring Program (DSMP) is to collect water data twice a week from fixed stations to determine the status and yearly, seasonal, and daily trends. The DSMP interns use a YSI-85 Handheld Dissolved Oxygen, Conductivity, and Salinity Meter and a Sechhi Disk to collect the following measurements:

  • Temperature
  • Salinity
  • Dissolved Oxygen
  • Turbidity

Water quality characteristics often help determine the relative health of the aquatic ecosystem of the Devereux Slough. The data collected by the DSMP interns will help create baseline measurements for future development or pollution issues in the Devereux Slough Watershed.

Temperature

Water temperature is a parameter that influences biological activity and chemical reactions. It is closely related to oxygen concentration and affects photosynthesis rates, metabolism, migration, and reproduction. Temperature fluctuates in an estuary based on: water depth, season, mixing from wind and tides, stratification (layering), temperature of inflow, and human influences. Temperature shifts of more than 1o-2o C can cause thermal stress and shock, and long-term temperature changes can affect the distribution and abundance of certain animals in the Devereux Slough.

LINK TO TEMPERATURE DATA (under construction)

Salinity

Salinity, the concentration of salts dissolved in water, changes drastically in the Devereux Slough depending on the season and the amount of fresh and saltwater inputs. It affects the types of species living in the estuary (marine vs. freshwater vs. tolerant to both), and also influences chemical and physical processes like stratification. Saline water is denser than freshwater and sinks to the bottom of the estuary, carrying fine particles and inhibiting mixing with surface water.  Salinity is expressed in parts per thousand (ppt). Normal ocean salinity is 35 ppt, while the slough's salinity can varvaries from 0ppt to over 70ppt.

LINK TO SALINITY DATA (under construction)

Dissolved Oxygen

Oxygen enters the water column from photosynthesis in aquatic plants and from diffusion from the atmosphere. Once dissolved, it is used by animals and plants for respiration and by microbes during the decomposition of organic matter. The amount of oxygen that can be dissolved in water is affected by temperature and salinity. Dissolved oxygen (DO) is measured by an electronic meter and reported in milligrams per liter of water (mg/l). When oxygen levels are depleted below 3 mg/l (hypoxic conditions), many organisms will die or move, and depletion below 1 mg/l (anoxia) kills all animals requiring oxygen to survive. The water may become stratified, with anoxic water at the bottom and oxygen rich water on top. Also, when pollution or fertilizers deliver extra nutrients to the system, the system becomes over productive with algae which then die. In the process, decomposers take up some or all of the oxygen produced by plants, decreasing oxygen levels and sometimes dramatically affecting aquatic habitat.

LINK TO DISSOLVED OXYGEN DATA (under construction)

Turbidity

Turbidity is the clarity of the water, and it is influenced by suspended particles such as sediment, organic material, or plankton. It is measured by visually determining the ability of the water to transmit light, using a Secchi disk or a turbidity meter. Turbidity naturally increases during storms, after erosion events, and from seasonal blooms of plankton or algae. Excessive erosion caused by construction, forestry, or agriculture can cause unnaturally high turbidity, along with waste discharge, urban runoff, or blooms caused by high nutrient levels, or eutrophication. Regularly high turbidity levels can choke fish gills, cause reduced growth rates, disease resistance, and egg development in fish, foul filter feeding clams and mussels, or even prevent predators from seeing their prey. Sediments also carry pollutants from fertilizers or urban areas upstream, and can remain suspended or settle to the bottom. Settling sediment is a concern in the Devereux Slough because it affects the circulation of water and functioning of the estuary. Turbidity is measured in milligrams per liter (mg/l)

LINK TO TURBIDITY DATA (under construction)

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