“Big” Irma at the GTM

By Shannon Dunnigan

We’re still here!

It has been a crazy few weeks for us NERRds with “Big Irma” and we were unable to contribute to our monthly blog post schedule (we release new content the first and third Wednesday of every month). We hope everyone that was affected by Irma is on their way to recovery. Post-Irma cleanup efforts are still underway here at the GTM and we have been working very hard to clean the debris on our beaches and waterways that Irma left in her wake.

We figured the best way to get back and active on our blog would be to share with you fellow NERRds some of the data we collected from Irma. She’s still on everyone’s mind and she brought some interesting impacts to our water quality.

Today will be a brief post as we are still working on a more comprehensive study into the effects of Irma (so keep an eye out for more!) at the GTM. One of the first things that we like to look into is salinity (how salty the water is) because it is a good indicator for rainfall during a storm. Additionally, being on the east coast of Florida, we also can see trends in salinity that are indicative of wind direction!

Did you know that when we get nor’easterly winds, they tend to push seawater into our estuary?

When that happens, the salinity of the water tends to increase because we are getting more water from the ocean. The salinity of ocean water tends to be around 36 practical salinity units (psu). We started our investigation into the effects of Irma by examining salinity patterns at our northernmost water quality station. Our Pine Island station is located near Pine Island in the Tolomato River. This station typically has a salinity around 29 psu.


Average daily salinity quartiles plot with overlay of current year daily averages. Dark gray represents 25-75% quartile range (where the majority of the data lies) and includes data from 2002-2016. The light gray represents the minimum and maximum values that fall outside of the quartile range, also includes 2002-2016 data. The 2017 daily average salinity values are indicated with the red line.


During Irma, we experienced an average daily salinity value of almost 2 psu! That was a new record low average for this time of year. You can see that large drop in salinity from Irma just after the 09/01 date in the figure above. Not only that but Tropical Storm Emily (which cut across the state of Florida July 31-August 1) also resulted in lower salinities than average at that time frame, too.


Yeah, that was a great way to start investigations into our data.

We’re expecting to see a lot more effects of freshwater input from rains brought in by Irma. Our next steps are going to be expanding into other stations (we have four at the reserve!) and including some of the meteorological data as well (precipitation and wind speeds).

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One Comment Add yours

  1. Debbie Dix says:

    Interesting, thanks!

    Liked by 1 person

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