Welcome to the Manatee Project

Today, our group drove about one and a half miles south to an area called Matlacha Canals. Mote Marine Laboratories has a boat docked out there as well. Sherri Barton, Mrs. Frederick, and I worked off of the Matlacha boat called "Wellie". Teresa, Rachel, and the other Earthwatch volunteers drove MERV down on a trailer, and put him into the water up there as well.

Sherri is completing a three year study of the Matlacha canal system, and we did some data collection with her today, to help her get closer to some conclusions. Since Sherri's study is quite involved, I am going to explain it in a format that you all know so well, so that it will be easy to understand.

I. Problem - Why do manatees use the Matlacha canal in the winters, even though there is no warm water source? Why don't they use similar canals in the area?

II. Research - We basically know that manatees cannot be in waters that drop below 60 degrees Fahrenheit, or they will die from cold stress. Manatees usually migrate in the winter to warmer waters, or congregate around power plants.

III. Hypotheses:

1. Fresh water seeps may be present (fresh water seeps up through the canal floor), and they may keep the water warm.

2. Since Matlacha is only one canal, that branches off into several, there is less water flushed in and out, so the air temperature would have less of a cooling effect.

(Before I get into today's procedure, let me tell you what Sherri has already discovered. The salinity in Matlacha is not very different from anywhere else. Which hypothesis does this rule out?)

Do you remember what this piece of equipment is called, that we use to test for salinity?

IV. Procedure

A. Materials:

1. Boat - We used Wellie today.

2. A sectioned rope to record the depths of the water. One end of the rope had a sinker on it. This allowed us to lower the rope into the canal, and the sinker would tell us where the bottom was.

This rope was also equipped with a bead that marked every foot, and a cluster of three beads every five feet.

When I lowered the rope into the water, and the sinker hit bottom, I marked where the surface of the water was on the rope. This allowed me to record the depth of that particular spot in the canal.

3. A tape measure was used to be sure that my measurements were accurate, if the depth did not fall exactly on a bead.

4. What did I forget that should always be in the materials list? We did have these on the boat as you will see shortly.

B. Directions

1. Sherri drove the boat around the canal and positioned it for measurements.

2. One of us used the sectioned rope to find the depth in certain areas.

3. The third person marked off areas on a map where we measured the depth, and recorded all of our results in feet and inches on a data chart.

(Mrs. Frederick and I took turns, which is why you can see me in both roles.)

V. Recording Data

This is a map of the Matlacha canal area. The areas in white are the canals where we recorded depths today. Lets all look at Site # 2 as an example. When we got to Site #2, Sherri wanted us to take three readings in each cross section. What that means is that in the far right on your map, we took our first cross section called A. In that area, I took three depth measurements. I took one on the south bank (closest to you), one in the center, and one on the north bank (furthest from you). We followed this same method for all of the cross sections you see labeled on the canals.

On the data sheet above, the data recorder was in charge of writing down those depths. If you look at the first row, you can see that the site we are looking at is Site #2, the one we just examined on the map. The cross section on the first line is A, the section we also just referred to on the map. We had to write down the time of each reading, so you can see that we started this at 10:39 this morning. After that you can see the three depth measurements which run from the south to the north. The water near the bank closest to you on the map was 6 feet, 2 inches. The water in the center of that cross section was 7 feet, 3 inches. Finally, the water near the bank furthest from you was 8 feet, 3 inches.

We followed that same procedure for each cross section in every site in Matlacha canal. This process took close to three hours!

We did have a few manatees swim by to check out what we were doing, but since we were working on data collecting for Sherri's study, we did not take any photo ID pictures today.

V. Results:

Here is where you can help Sherri! In order for her to figure out how much water is displaced when the tides come in, she needs to do some math with the data collected today. First, you need to copy down the section of our data chart from today. You must have all information from sites 2, 7C and 7B.

So that Sherri can get an average depth for each area, you need to find the mean (the average) of the depths for her. For example, take all of the depths recorded for Site #2 and add them up. Divide them by the number of depths you have. Do the same for the other two sites. I will ask Mrs. Knight to e-mail me your results. You need to send back a mean depth for Site #2, a mean depth for Site #7C, and a mean depth for Site #7B. We look forward to using your results!

VII. Conclusion - In order for Sherri to draw a conclusion from our data, she had other people doing other things today. Some earthwatch volunteers were on a dock to measure the tides. This will allow Sherri to compare that to our data and determine what percent of the total volume of water in the canal is exchanged during a tide cycle.
She also had another group out on MERV taking water depths in two other small canal systems close by. That way she can compare our data with theirs and see if there is something special about Matlacha canal that draws the manatees there each winter. If less water is exchanged during a tide cycle in Matlacha, then she will have proved her hypothesis. We do know that it stays at least 5 degrees warmer than the other canals, hopefully you can help us figure out why!