Tracking Microplastics Through A Food Web

This week I spent more time working on my microplastics side project, but I am happy to report that I can soon talk about the Tipping Points project and its outcomes in more detail. We will be presenting this work to the local government in a few weeks and then, as far as I know, we will be uploading the completed report. Stay tuned.

​In the picture above you can see a really early example of tracing microplastics through a subcomponent of a northern Gulf of Mexico food web. You can see the groups in the food web in the top left, with groups 18-22 not visible, and I have the nematodes (1A, 1B, 2A) group plotted with their cumulative microplastic concentrations from the model start to end. In this example, you can see that as the simulation years increase, the cumulative microplastic concentration in these nematodes also increases, with variability and you'll notice that the rate of increase is large between 2000 and 2005 and then decreases from 2005 to 2020. This current model run is based on some potentially inaccurate numbers, though, because I still need to perform additional calculations. For example, the amount of microplastics I set to enter the system every year was based on the amount of microplastics found in Mississippi River water sampled at New Orleans, but I have based the environmental concentrations for the rest of this project on microplastics in the sediment. Therefore, I need to calculate the proportion of river microplastics that will sink to the seafloor, and how quickly that process will take so that I can adjust my initial concentrations. These concentrations are based on data from later than my model start, year so I want to calculate the expected concentrations for 2000 so that I am generating as realistic a model as possible. Additionally, I have to make adjustments to the model fit. That is, the current model has some irregularities as it runs from year to year, and irregularities in the predator-prey interactions will undoubtedly affect microplastic transfer between model groups.

Once I have smoothed out these current issues, I will move on to testing model scenarios. I will be adjusting the microplastic input rates-how many particles are entering the ocean and therefore sediments-to test how proposed and expected management scenarios may impact the concentrations of particles found within charismatic organisms, like blue crabs and Kemp's ridley sea turtles, but also less charismatic organisms, like nematodes and copepods. 

For all this and more, stay tuned. Be ready for two exciting blogs in these next two weeks as I have a cool research excursion on the horizon.

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