Tidal Fish - Water Quality

photo of a biologist lowering a Hydrolab into the water to measure water quality parameters.
A biologist lowers a HydrolabTM into the water to measure water quality parameters.
Water Quality measurements are taken at each station using a HydrolabTM and a secchi disk.   Temperature, dissolved oxygen, conductivity, salinity and pH measurements are taken at three depth intervals (surface, mid water and bottom) using a HydrolabTM.  The HydrolabTM is a self contained meter that instantaneously measures water quality parameters.  Water clarity is measured using a Secchi disk (see photo on bottom left).  The Secchi is lowered into the water until it just disappears.  The depth of light penetration (where the disk just disappears) is recorded.  These measurements give us insight into the condition of the local habitat.
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photo of a Secchi disk being lowered to measure water clarity.
A Secchi disk being lowered to measure water clarity.

Of particular interest is the dissolved oxygen concentration throughout the water column. If oxygen concentrations in the water column become too low, fish will become stressed and leave the area or die off.

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For more information, please contact Margaret McGinty (mmcginty@dnr.state.md.us) of the
Maryland Department of Natural Resources at (410)260-8630.

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