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.