The sun is the source of light and heat energy in marine ecosystems. All plant life (plankton, algae, and macro plants) need light for photosynthesis, the basis for all energy flow in the environment. Water must be clear if light is to reach organisms lower down in the water column, thereby still allowing photosynthesis to take place.
The depth of light penetration in water is determined by the nature of light and water's ability to filter out specific wavelengths. Light is made up of different wavelengths that we perceive as different colors. Not all colors are equally transmitted through water. Red wavelengths are filtered out in the upper layers while the blues reach farthest into the depths.
The depth of light penetration in water is determined by the nature of light and water's ability to filter out specific wavelengths. Light is made up of different wavelengths that we perceive as different colors. Not all colors are equally transmitted through water. Red wavelengths are filtered out in the upper layers while the blues reach farthest into the depths.
Students watch as they are shown how to use the equipment for measuring the turbidity of the Bay of Islands.
Dissolved and suspended material such as tannins and sediments color water and affect the clarity, and thus the penetration of light through the depths. If water is cloudy, it will reduce light penetration and is said to be turbid. We will determine the clarity fo the water by using a Secchi Disc, which indicates the depth to which light can penetrate. This measurement by itself, however, does not indicate water quality even though the clarity of water can give an indication of the health of an aquatic system. Clear water may be good for light penetration, but the water may be clear due to a high level of acidity (low pH), and water organisms may have been killed by this acidity. While turbid (cloudy) water may prevent light penetration, the turbidity may be caused by plankton, which indicate the presence of abundant nutrients. A Secchi disc reading alone should not be the only indicator of water quality.
The graph to the left shows the turbidity measurements from 10 Bay of Islands sites in the years 2005 & 2006.
The data used to generate the graph was collected in the Fall season of 2005 & 2006.
A copy of the Microsoft Excel spreadsheet containing the data used to generate the graph may be downloaded here.
The data used to generate the graph was collected in the Fall season of 2005 & 2006.
A copy of the Microsoft Excel spreadsheet containing the data used to generate the graph may be downloaded here.
Environmental Education - Science & Research - Community Engagement
Initiative Supported By
ACAP Humber Arm Environmental Association Inc.
P.O. Box 564, Corner Brook, NL, Canada, A2H 6E6
P.O. Box 564, Corner Brook, NL, Canada, A2H 6E6