Maria Gallegos


The purpose of this research was to see if turbidity can have a large impact on community structures. Oyster reefs are a very important part of our ecosystem. They assist in reducing the amount of erosion caused by the ocean. Many small ocean creatures live in oyster reefs. Previous studies found that turbidity can have large impacts on community structure.  Joey’s study is to see if the cloudiness of the water or turbidity has an effect on the types of predators that are in the oyster reef and if humans responsible for these turbid waters are harming the environment.  In areas of high turbidity, communities were dominated by chemo-sensory organisms like crabs. In low turbidity sites, visually oriented predators such as fish tend to dominate the community.
Does turbidity alter these communities at different levels of turbidity?
How it affects different atrophic levels?
And ultimately how these effects scale up to the entire community?
Turbidity – the cloudiness of water
Chemo-sensory – sensitive to chemical stimuli, odor detection
Refractometer  –  used to measure salinity


Methods & Procedures

Sometime in May, thirty sites were picked on oyster reefs. They were marked with pvc pipe so they could be located in the water. Three cages were placed at each site. They used an open cage, a small mesh cage and a large mesh cage.


 Oyster shells were placed at the bottom of each cage to imitate oyster reefs. We came into the study when the cages had been out in the water for approximately 2 months. Our job in the experiment was to help pick up the cages and collect the samples. They planned on collecting 30 cages a day and it ended up taking 4 days instead of 3. (There was also other information being collected for other labs being run by grad students). We located the cages, placed a mesh net around each one of the cages in an attempt to catch anything round it. Once the mesh net was placed the cage was removed and taken to the boat. The sample was picked through collecting fish, crabs or shrimp.  The samples we collected were placed in a solution with ½ water and ½ ethanol to be sorted, labeled and measured at a later date. While the sample was being picked through, others were at the mesh netting and were sweeping it, collecting any fish, crabs or shrimp caught. If the sample was of good size, it was measured and documented there then released back into the water.


I did have the opportunity to start going through the samples and this was not an easy task. We first separated the specimens. Example: grass shrimp to brown shrimp and snapping shrimp a count was taken. If there were less than 22 then they were all measured. If there were more than 22 a total count was recorded and what were measured were the smallest, the biggest and 20 random samples. We repeated with the crabs however if the crab was missing a claw or was less than 10 mm in size they were all put into an uncategorized group. We also recorded the number of crabs that were sponging (carrying eggs). We did the same for the fish. Joey used the microscope when needed to identify the different types of fish in the sample.





This is the one part of the experience I didn’t like. The sorting through the samples is going to go on for some time. There isn’t a big urgency to get it done, especially in the time frame that we work in the labs. I don’t know the results and might not ever know them. They are looking at how community structure differed between locations of high, low, and variable levels of turbidity along oyster reefs. We used three different types of cages (open cages, small-mesh cages, and large mesh cages) to look at how oyster reef communities respond to varying levels of predation at different levels of turbidity.

Lesson Plan

8.11B investigate how organisms and populations in an ecosystem depend on and may compete for biotic and abiotic factors such as quantity of light, water, range of temperatures, or soil composition
Prior to lesson need to make sure students know definition of: ecosystem, community, population, abiotic, and biotic


Show students video below:
 Why Oyster Reefs Matter to You


Explore how population affects a community and how a community affects an ecosystem.


Ask students to think/pair/share the meaning of a population? A community? Advantages? Disadvantages?
Ask students why they think water clarity matters in the case of the of the oyster reefs.


Students will participate in a lab.
The classroom will be mimicked as best as it can to imitate an oyster reef. Some students will be selected as crabs, some as shrimp and some as fish. Students representing organisms will be divided into 2. Two groups of crabs, fish and shrimp. Half will have their vision impaired and the other half will not to represent different levels of turbidity. In low turbidity sites visually oriented predators such as fish tend to dominate whereas areas of high turbidity chemo-sensory organisms such as crabs do. They will be timed and given an opportunity to search for food and survive in different conditions.


Students will be asked to type a one page report discussing their findings. Give their opinion on if they think different levels of turbidity affect the survival of organism and answer the following question:  When a predator is out-competed for biotic resources (prey) by other better adapted species what choices can it make? They will also include a drawing representing their understanding of an ecosystem.