Sediment plates and Long-term data!

by CJ Carroll

This blog summarizes the past two activities completed by the Research Methods in Marine Ecology class.





On October 6, 2009, we collected and analyzed sediment plates that were submerged in the creek behind SSU for about 6 weeks. This was completed to determine what organisms would settle and grow on the plates. Also, pairs of plates were set at different levels in the water column to determine if different things settle in different areas. The three areas in the water column were the surface, the middle of the water column, and the lower intertidal area. After six-weeks on being in the water the sediment plates were pulled up with the aid of a net to capture any vagile organisms (opposite of seesile organisms) that are hanging on to the plates. If organisms were large enough to distinguish individuals or individual colonies with the naked eye, then the individuals and colonies were counted. For organisms that were not large enough to see with the naked eye the percent of composition on the plate was determined. All six plates were analyzed at the dock, photos taken and then plates clean.
The surface sediment plates were dominated by sea squirts, different types of algae, and mobile invertebrates (e.g. crabs and shrimp). The middle of the water column plates contained different types of algae, shrimp, and crabs, but not in the levels seen at the surface. Also, bryozoan colonies and titan acorn barnacles were found in the middle of the water column. The lower intertidal plates were either a muddy slime or mostly empty. A little bit of green filamentous algae, titan acorn barnacles, and bivalves were also found. Diversity was calculated for each area using the Shannon-Wiener Biological Diversity Index, which measures on a 5 point scale with 5 being diverse and 1 not diverse. The lower intertidal area was the least diverse with an index of 0.91 and the middle of the water column was the most diverse with an index of 1.53.


This is a photo of one of the surface plates covered in green filamentous algae, sea squirts, and brown-green algae.


This is a photo of one of the plates that was lowered into the middle of the water column. It is covered in brown algae, brown filamentous algae and bryozoan colonies.


On October 13, 2009, we downloaded long term data from the National Data Buoy Center’s website. The data was downloaded from the 2008 Standard Meteorological Data and provides information about offshore conditions. The erroneous data was deleted and the wind speed and wave height separated. Averages and standard deviations of both categorized and graphed. When comparing the two graphs over one another, a clear trend presents itself. As the wind speed decreases, the wave height decreases. As the wind speed increases, the wave height increases. This correlation leads to the hypothesis that the wind speed has an effect on the wave height.

Sediment sampling

Written by Dana Davis

On September 29, 2009, our class went into the marsh at low tide behind Savannah State University's marine science building and collected sediment samples. Push corers were used to collect sediment from 5 different sites. The push corers used were clear, hard plastic tubes that opened on each end, similar to a paper towel roll. By pressing the push corer straight into the ground until sediments reached a marked line of 10 cm, the sediments were collected with little disturbance of the environment. The sample sites began at the outer edge of the marsh and continued towards the creek at intervals of about 3-5 m apart. Next, the sediment samples were taken back to the lab to be sieved and weighed. A sieve consists of several plates with different sizes of mesh in between in order to separate the different sized sediment particles. For each sample, the sediment was placed on the top of a sieve beginning with 500 micrometers, then 250, 125, and ending with 63 micrometers. Tap water was used to help transfer the sediment through to each plate. This was a time-consuming task, and 4 of the 5 samples were separated out. Next, the sediments were placed into the dryer on pre-measured tins for 24-48 hrs. The sediments were then re-measured when completely dry.

The 500 micrometer sieve was not included in further calculations due to the large amounts of plant matter, debris, and rocks in all samples. The largest percent of sediment for all 4 samples was deposited in the 125 micrometer sieve consisting of fine sand. For sites 1 and 3, the samples collected farthest from the creek, the majority of sediment was composed of fine sand particles followed by medium sand particles. Sites 4 and 5 were collected closer to the creek and were comprised of mostly fine sand particles with very fine sand being the next abundant sediment.

The picture above shows a sediment sample after sieving and drying. The top left is the 500 micrometer collection then going clockwise to the 250, 125, and 63 micrometer samples.

The figure above shows the percentage of different sized sediments (250, 125, and 63 micrometers) for each site.