Contributed by Madison Barbour

Our class has been conducting salinity tests which shows how much salt is in the water in different areas of the marsh. The reason why we have been taking these samples is because there could be saltwater in the marsh and alewives are supposed to spawn and develop in the fresh-water. We have been doing this so that we can understand why the alewives haven’t been returning. The only thing that we could really find in the stream waters were elvers.

On May 16th, 2018 the 7th grade class went to the marsh. We went at 11:15 am, about an hour before high tide. At the marsh we took two water samples and brought them back to the classroom and let the water get to room temperature. Once they were at room temperature we used the refractometer which shows the salinity of the water. For the salinity of fresh-water it is supposed to be 0 ppt (parts per thousand) which is what we got when we tested our samples from the marsh.

We are interested in taking more samples when the tide is over 10.3 feet and flooding the Marsh. The reason why we are interested in that is because the water could flood into the Marsh and put salt in there that doesn’t belong. Twenty days of this month had tides 10.3 ft and over.

We have been trying to determine why the alewives haven’t been returning. We have been taking the samples to gather information to find out why they haven’t returned.

Contributed by Maggie Gill

The watershed of our marsh is in trouble, especially for the alewives.

As you might already know, the alewives that used to thrive in our town disappeared for over 30 years, leaving everyone wondering ‘What happened?’ Two years ago we got another shock; they came back! But there might be another problem on our hands now…

In science class, we have been studying the salinity in the marsh. Using the refractometers that measure the salinity in water, we took two samples from the marsh and three different points near the stream and the culvert on May 16th. We took the samples back to the classroom and measured how much salt was in the water in each sample.  Fortunately, water coming directly from the marsh was found to have zero parts of salt per thousand parts of water (0 ppt). In the stream itself we found anywhere from 4-27 ppt because of the tidal influence. We do think that some tides bring salt waters right over the outlet and directly into the marsh.

 

Now, you may be thinking “Okay, so there’s a little bit of salt in the waters of the marsh. What’s the big deal? And how does this relate to the alewives?” Here’s the problem about the salt in our watershed; research suggests that alewife eggs develop best in less than 5 ppt of salinity. Now is where the other part of our studies comes in.

Along with studying salinity, we have been studying tides that can flood into the marsh. According to the ‘rule of twelfths” of a tide cycle, we can go down to the marsh at any time and find out if the coming (or leaving) tide will (or has) flood (or flooded) the marsh. Here’s an example of how to calculate the final height of the tide; Say it was 1 hour before the coming 8.7 foot high tide. First, we would measure the water in the culvert, and let’s say that that we measured 10 inches in the culvert. Then we go back to the classroom and start calculating, knowing the time we made the observation, the time of the high tide, and the predicted depth of the tide. First, we find 1/12 of the 8.7 foot tide since there is another hour of water to come in on the tide.  One-twelfth of 8.7 feet  is 0.73 feet. Then we find out how many inches 0.73 feet is.  That answer is 8 and 1/2 inches. The next step is to add this to our original measurement of 10 inches for a total of 18 and 1/2 inches.  Since the difference in elevation between the bottom of the culvert and the outlet of the marsh is approximately three feet, this high tide of 8.7 feet, with 18 – 1/2 inches of water in the culvert would not flood the culvert.

In conclusion, the marsh’s alewives run may be in even more trouble, even if you can’t see the damage as its happening. To keep you updated, you could check out our website, https://marshwatershed.edublogs.org/ .

 

Note:  Thanks to a grant from the Gulf of Maine Research Institute’s  “Vital Signs” Freshwater Investigations program, and direction from Paul Meinersmann, students are building a digital salinity sensor station to deploy in the marsh.  Students are reading and learning about how the different parts work, how they connect together, how to write code in order to give the sensor commands.  After testing, it will be ready to go.  Collecting salinity data over time will give us a better view of how tides influence the freshwater of the marsh and possibly the alewives.

 

Our grant application from the Gulf of Maine Research Institute was awarded and students are busy constructing a “remote salinity sensor station” that can digitally monitor the salinity of the marsh waters in the area near the outlet.

 

Contributed by Willow McConochie, Sophia Miller, Gwen Miller

Willow McConochie, James Cody, Jack Elwell, Sophia Miller, Gwen Miller, and Zeke Miller have been going up to the library every Thursday after lunch to work with Mr. Meinersmann to build a digital salinity sensor for the marsh. So far we have not done too much building, but we have been reading and learning about how the different parts work, and how they connect together.  We will have to solder the circuit board and its wires to connect the probe and program the circuit board to collect data at specific time intervals.  In order to do this we’ve been learning how to decipher code, and how to install it into the sensor to give it commands. After we are done building the sensor, we will test it indoors to see if it reads accurately before we put it into the marsh.

Testing the salinity of the marsh is important because research suggests there can only be five parts per thousand of salt in the marsh in order for alewive eggs to form properly. Last week we discovered that a tide greater than 10.3 feet will reach the outlet dam of the marsh. The only problem with that tide is that salt water will enter the marsh. Salt water will be able to reach the marsh. We wanted to be involved with this project because we thought it would  be fun to build this sensor and find out how all of the different mechanisms work, and to explore more about the marsh.

 

 .  Note from Mrs. England

In the meantime, our class has been collecting water samples from the marsh to manually test for salinity differences.  We used a refractometer and first tested a sample with distilled water and adjusted the scale to zero when needed.  Then we tested our marsh sample at room temperature.  We will be posting our data soon.  Some of the highest tides in May are occurring this week and weekend, so it’s important we collect as many samples during this time as we can.  Stay tuned!

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