FREE ESSAY ON EFFECTS OF DEPTH AND SEDIMENT CONCENTRATION ON THE PENETRATION OF PHOTOSYNTHETICALLY

EFFECTS OF DEPTH AND SEDIMENT CONCENTRATION ON THE PENETRATION OF PHOTOSYNTHETICALLY

Effects of Depth and Sediment Concentration on the Penetration of Photosynthetically
Active Radiation in Water
Introduction The purpose of this study plan is to measure the effects of light on
sedimentary particles in water. This study plan will include information pertaining to
equipment, procedures, and analysis. This plan will also discuss problems that could
arise during the sampling.
Objectives The objective of this study is to observe whether sedimentary accumulation at
various depths will effect the penetration of light energy. One reason for monitoring
light penetration is to determine if sufficient energy is available for photosynthesis.
This energy is effected by the amount of sedimentation that is suspended in the water. In
order to ensure the data's scientific validity this study needs to include the main
principles. These include selecting a control; a control will be the measurement that all
other data is compared to. Second, the selection of the sample sites must be non-bias and
random. This ensures that the experiments are not predictable or foreseeable. Finally the
experiments must be described in great detail so that they can be replicated at a later
date.
Literature Energy is distributed throughout the world's oceans in several usable forms.
The heat transmitted during absorption is responsible for ocean waves, temperature and
currents. Light penetration in water will measure in units of quanta. This measurement
refers to the amount of sunlight that penetrates the water at various depths. The light
energy is absorbed and scattered by suspended particles, dissolved substances, and the
water itself (USGS). Other factors include attenuation coefficient: rate at which light
decreases with depth. This means that each site studied may have a different attenuation
coefficient. An example of a high coefficient would indicate a rapid decrease in light
penetration, therefore, high sedimentation. Another factor to be aware of is the color of
the water. Color can effect the light penetration and intensity. Also the turbidity which
is a measure of water clarity and how much material is suspended in the water. Suspended
material could include soil particles, algae, plankton, microbes, and other substances
(EPA). The sources of the turbidity could include erosion, waste, runoff, and bottom
feeders (EPA). 
Equipment The instruments used to make photosynthetic measurements is called a Li-Cor
Quantum/Radiometer/Photometer model #189. The sensory device is connected by a long cord
and is used to measure at depth. It's called an underwater PAR sensor; Li-Cor #1925. This
sensing device or photocell can also be used to measure surface PAR. Other devices to be
used during the data sampling include lowering frame Li-Cor #20095, various weights and
cables. The cables and weights will used to hold the sensors in the water column at the
proper depths. Another instrument could be used to calculate the amount of PAR that is
received at the surface. This instrument is called a pryanometer. It is not a requirement
to use two different instruments for surface PAR, but just a suggestion that might give
more scientific validity to the data being collected.
Procedure While conducting this experiment it is necessary to have at least two people
present to take the measurements. One person will lower the sensor in the selected site
locations. The other person will record the PAR measurements from the display and
calculate range values. The measurements will be taken within a four-hour period, two
hours on either side of the solar noon. Solar noon is half way between sunrise and
sunset; not 12:00 noon. Solar noon is at 1:15 PM, Central Daylight Time. This is the time
when light energy is at the maximum. Samples are taken between 11:15 AM and 3:15 PM and
are taken every 30 minutes; and data recorded at 10 second intervals. Before the samples
can be taken it is imperative that the Quantum Radiometer be clean and free of debris and
calibrated. This calibration will correct errors that may occur. Also the collection of
the control data must be present. This control must be free of errors and represent the
selected site. Another measurement must be made of the surface PAR. This data will help
determine the amount of light energy present at the surface. Next the determination of
water columns is important. These sites must be chosen randomly and cover the entire
site. Later others can concentrate studies in points of interest. These measurements are
taken using the underwater sensor attached to the lowering frame. Each water column will
be measured at every 10 cm. These recordings will continue until the photometer can no
longer detect light energy. The underwater sensor must be perpendicular to the bottom
surface so that light intensity will be scattered at a 90-degree angle. Each column will
be tested twice so that representative data is present. These samplings should be
recorded in a table format, and be divided into proper water column, and depth
categories. The temperature of the outside environment should be determined and placed in
the table format along with the descriptions of the sample sites and surface PAR data.
The number of water columns is dependent on the sample site. Remember sample columns must
be representative of area being tested. 
Analysis Other factors that may effect the data collected include not returning to the
same sample site later to measure the same water column. This can be corrected by placing
some type of marker on the shore if the sample column is near shore. Other marking
devices are needed if the sample area is in the middle of the water where no references
can be determined. These marking devices include floating buoys, and floating balls.
These devices are necessary to make the data consistent and accurate. Another problem
that can effect samples is shadows. It is important not to take the measurements when the
area is being shaded. If there is abundant cloud cover out it is necessary to wait until
clouds dissipate, or discontinue taking measurements for that period. 
Conclusion A high sediment concentration in the water will increase water temperature
because the material suspended absorbs more heat. Unfortunately this also leads to the
decrease in light penetration because the particles block the light from reaching the
bottom. Therefore reducing the amount of photosynthesis that will occur in the water.
While conducting this study plan it could be said that light and depth are proportionate
to each other. This means that the depth of the sensor effects the amount of light that
can be measured through the sediment filled water.