Today we did a different type of data collection. On most days our major purpose has been to locate manatees, photograph them, and record their scar patterns. Today we traveled south to Matlacha Isles (see if you can locate this spot on your map and estimate the distance from Mote) and did a series of depth readings in the canal there. Let me give you some background to explain why we did that.
As you know from your research on manatees, they like warm water. When the water temperature gets below 60 degrees manatees migrate; otherwise they will die of cold water stress. Usually they migrate to areas around power plants where there is warm water discharge or to areas where there are thermal (warm) springs. Observers have noticed that manatees aggregate in the winter at Matlacha. Sherri Barton, a staff biologist working on her master's degree, is trying to determine what attracts manatees to this particular location. Preliminary studies have ruled out the presence of hot springs in the area. Here is a picture of Sherri driving the other manatee research vehicle, nicknamed "Wellie".
Fortunately there are two canal systems very near Matlacha which have very similar conditions, yet manatees do not aggregate there in the winter. These neighboring canal systems, West Island and the top of Pine Island, are serving as a basis for comparison, similar to a "control group" when you do a scientific experiment.
You know that when scientists investigate a situation they make a hypothesis. Sherri's first hypothesis was that the winter temperatures in Matlacha were higher than at the other locations. Studies conducted over the past two years have confirmed that the winter water temperatures at Matlacha are consistently warmer than the other two locations by approximately 5 degrees.
The next question is WHY? They have tested for warm water seeps and have pretty much ruled that out. Follow up studies by a geologist using sophisticated sonar equipment will be done to completely rule this out. Sherri is working on another hypothesis however. The Matlacha canal system, while relatively large, has only one major entry and it is relatively small. Her hypothesis is that there is less water exchange during tides; as a result water within the canal stays warmer. To determine whether this is the case the tide range for each of the three canals in the study are being conducted. We collected data for that today. Here is how we did it:
First we started with MAPS - here is that geography again! We had a map of each of the canals. We broke into groups and each took depth readings in one of the canal systems. Look at the map below; it is the Matlacha canal where I worked today. It identifies 9 sites within the canal. At each site we usually took 3 transcets (across) and labeled them A, B, C. At each of the three transcets we took 3 readings - one close to each bank and one in the center. We had to label each N-S or E-W so that future readings will be done in the same locations. I know this sounds confusing! It was! Miss Plante and I worked together - one took the depth readings and the other recorded the data. We took turns with each task. We had to be extremely careful with both.
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Map of Matlacha Canal |
Data Collection sheets |
| Here is a picture of me recording data. I had to listen carefully and record accurately. I had to consult the map to make sure I was placing the readings in the correct location. My map reading skills came in handy today. You never know when you will need them! |
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Here I am taking the depth readings. The equipment used for this data collection is not very "high tech", but it gets the job done. A rope with a sinker on the end is used to measure depth. At one foot intervals there is a bead. At five foot intervals there is a cluster of several beads. At the specified locations the rope is dropped until you feel the bottom. You then pull up the rope, count the beads and determine the depth of the canal at that location. At first I had difficulty determining when I felt the bottom, but with a little practice it became easy. It definitely was a "learn by doing" experience. Because canals are made by dredging, the depth varied widely at different locations. |
My earthwatch partner, Miss Plante, and I double checking our data.
Two other members of our Earthwatch team spent the day taking tidal readings at a set location. This information will be used to adjust the depth readings we took based on the tide. Back in the lab Sherri will use the ArcView GIS computer program to calculate the length of the 3 canal systems. Using the depth readings we took today, it will be possible to calculate the volume of water in each canal. Using yet another computer program Sherri will be able to determine if the data supports her hypothesis that there is less tidal flushing at Matlacha and that explains the warmer winter temperatures. Today was "heavy duty" science! I hope this makes some sense to you.
While the main focus of today's exploration was not to photograph manatees, we did see a few. We also saw the spot where the scientists catch the manatees in nets, pull them to shore and attach the tags with transmitters. Here is a picture of that location.
Another thing we did while we were out today was to pick up temperature probes which had been in the water recoding temperature changes all season. It was amazing how encrusted in barnacles they had become in just a few months. I am sorry I did not take a picture to show you. When we got back to Mote we had to do the daily clean up. Today one of our tasks was to clean these probes. You cannot imagine what a difficult job it was! We scraped and scrubbed for almost two hours to get them clean. Once again, not all science is glamorous....
| The last point I would like to leave you with today is that not all people in Florida like manatees. When we were in Matlacha we saw this sign at a bait shop. SMC stands for Save the Manatee Club. Note the spelling of "to". What does that tell you? |  |
