 Temperature ~ Temperature is a primary control on many aquatic biological processes. Temperature, along with salinity, also controls the density of seawater. Sharp gradients in density between surface and deep waters, called a pycnocline, can block atmospheric oxygen from entering the deep water. Bacterial respiration of organic material in the deep water consumes oxygen and can result in low oxygen or anoxic zones. Such areas, often referred to as “Dead Zones” are of great concern as animals including fish and shellfish cannot survive without ample oxygen (effects of oxygen depletion begin at appx. 5 mg/L).
Salinity ~ Salinity measurements are based on the positive relationship of dissolved salts and electrical conductivity. Salinity measurements are unitless, but closely approximate grams of salt per liter of water. Sea salt is mostly sodium chloride (table salt), but seawater also contains small to trace amounts of sulfate, magnesium, calcium, potassium, bromide, strontium,boron, and fluoride. Through it’s control on density, salinity also effects the flow of water in estuaries and the open ocean.
Dissolved Oxygen ~ Dissolved oxygen is also measured with a electrodes on the YSI. Oxygen is supplied to the water column through diffusion of air, air bubble injection during wave action and through the photosynthetic activity of marine plants. Oxygen is removed from water column through diffusion into the atmosphere, bacterial respiration of organic material, and by animal respiration.
Dissolved Oxygen Saturation ~ An equilibrium oxygen concentration can be calculated for a given seawater temperature and salinity that reflect what the oxygen content of the water will be in the absence of other biological and physical factors. Plant photosynthetic activity that consumes Dissolved Inorganic Carbon (DIC) and produces oxygen often causes oxygen supersaturation (O2 saturation > 100%) while bacterial respiration of organic matter may cause oxygen undersaturation (O2 saturation < 100%). The effect of both processes can sometimes be seen in daily oxygen percent saturation plots that show supersaturations during daylight hours and undersaturations between dusk and dawn.
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Location of HPL on Maryland's Eastern Shore (above)
Location of HPL dock on HPL campus (below)
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pH ~ A measure of how acidic (pH < 7) or basic (pH > 7) the water is, pH is actually the – Log of the concentration (or it’s effective concentrations know as activity) of H+ ions. This measurement is also made with electrodes and pH often increases during periods of net plant production and decreases during periods of net respiration.
Turbidity ~ Turbidity is an analysis of the amount of particles suspended in the water and is measured by the amount of light (830 – 890nm) scattered in a known volume of water. Turbidity often rises sharply during storms that stir up sediments and rain events where runoff carries sediment from land to the water. High turbidity levels cause low water clarity and reduce the penetration of sunlight into the water. Marine plants, particularly Submerged Aquatic Vegetation (SAV) which is critical habitat for many juvenile fish and shellfish, suffer when turbid waters shade them from sunlight.
Chlorophyll ~ Chlorophyll is a common pigment used to capture the suns energy for growth in marine plants and is thus used as a rough indicator of phytoplankton abundance. When irradiated with light, chlorophyll fluoresces or emits light at a higher wavelength (lower energy). The YSI emits light at around 470nm (blue) and measures the excitation light between 650 and 700 nm (red). Similar to oxygen saturation and pH, chlorophyll plots often show a daily sinusoid reflecting light and dark cycles. Sharp peaks in chlorophyll may indicate the presence of a phytoplankton bloom. If these blooms are large enough to cause oxygen depleting or block sunlight from SAVs, they are considered Harmful Algal Blooms (HABs).
You can also down load the data text file. Please note that all of this data is preliminary and has not been validated for errors. |
