The Boss Has A Plan

This week has been a busy week but we've mostly been writing papers, making revisions, and crafting a grant proposal at the lab. Unfortunately, none of these are the usual exciting updates I provide. I will, instead, talk briefly about Kim's great idea and how Hannah and I tested a prototype and will hopefully be testing the updated version soon.

When we go to the field to conduct our water quality sampling work, we perform three sets of data collection and/or sample collections. We complete a vertical profile, where one or two team members lower a multi-parameter water quality device slowly to get readings every 0.5 or 1.0 meters, depending on the water depth. The water quality device has a digital screen that shows the team member(s) various measurements as the device goes through the water, and the team member(s) record those measurements on our waterproof data sheets. At the same time, our BlueBoat uncrewed surface vessel drives itself across the water to collect surface measurements every 1-2 minutes. Here, we are gathering more points at the surface to help our hydrodynamic modeling team and we are collecting an additional variable that our multi-parameter device cannot record: nitrogen (nitrate). Nitrate is a limiting nutrient in the ocean, which means that a lack of nitrate limits the growth of primary producers, like seagrasses and phytoplankton. Too much nitrate, however, causes algal blooms, which you've likely heard about in the news, as these harmful algal blooms often occur off the coast of Florida, when excess nutrients end up in coastal waterways. For our work, understanding the amount of nitrogen in our water and its distribution helps us understand the primary productivity in our system and informs the base of our food web model.

The third type of data we collect in the field for these water quality trips are water samples. As most water quality meters do not have sensors for important nutrients like nitrate, nitrite, sulfate, and others, we instead collect water samples at the water surface, mid-way down, and right above the bottom of the water column to send to our colleagues who can analyze the nutrients in the lab. For these water collections, we lower a LaMotte horizontal water sampler, shown in the picture here, until we get to our depth and then we let the metal messenger slide down the rope which hits two latches and seals the ends of the tube, trapping the water sample inside. We can then bring the device to the surface, open it, and quickly transfer the water to our labeled sample bottles and get it on ice as fast as possible. We need to get it on ice quickly because the microbes and phytoplankton in the water sample will continue to use the nutrients in the water unless we can slow down their metabolism by cold shocking them. A major challenge we have been experiencing with this device, however, is that the river and ocean currents we experience during sampling occasionally cause our water sampler to drift. This means that the exact depth of our sample may not be consistent and can lead to possible challenges when we need to interpret our nutrient data. After some searching, we learned that others don't seem to have this challenge or if they do, they aren't reporting. 

Kim had the great idea to attach weights to the LaMotte and we purchased two flag counterweights, which are 1lb waterproof bags that won't hang when we attach them to our water sampler. Earlier this week, Hannah and I tried attaching one with rope to the water sampler and we successfully took the device in the field and collected water. We did find that the counterweight was not exceptionally secure, but we did notice the whole process was easier and the device was vertical in the water. After thinking about how to improve our prototype, I got zip ties and fastened the counterweight to the LaMotte, which I hope keeps the counterweight more secure. I'm not sure if the 1lb weight is going to be enough weight, so I will likely be adding the other counterweight to make one heavy sampling device rather than two moderately heavy devices. This will reduce our sampling speed but our goal is to improve accuracy, which may come at the cost of speed. Our first true test with our new device will be in two weeks when we are in the field for our first summer field sampling session, and I'll let you know how it goes.

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