Microplastics in the ocean have become a major environmental concern. There is concern that microplastics have entered the food chain and will impact biodiversity. Kaua'i’s coastline has intertidal habitats which host many important species such as sea urchins. Tidepools have limited circulation so they may be sinks for microplastics. Bottom feeders living in tidepools like sea urchins might be affected by the accumulation of micro-plastics. I wondered if there was a way to link microplastic pollution to the health of intertidal habitats, which is why I focused on sea urchins.
This might indicate that increased microplastic concentration impacts sea urchin density. What happens in tidepools is an indicator for what may happen ocean-wide as microplastic pollution continues. My conclusion is that the biodiversity and microplastics in tidepools should be carefully monitored.
In the future, I would like to improve my methodology. I had many challenges especially in my lab work. For example, not all the microplastics in the samples may have been located because they were difficult to identify or maybe my modified sediment microplastic isolation unit was flawed.
Even though (from this experiment) microplastics have a weak negative correlation to sea urchins, there are many other things impacting sea urchins in tide pool habitats which the experiment did not account for.
If done again, I can acquire a wider variety of samples and a larger number of samples. Another approach is to count other tide pool life. The microplastics could also be affecting smaller, less resilient benthic life. I would like to continue marine science research.
I took sediment samples from four tidepools in southeast Kaua'i using a homemade collector. In each pool, I measured total tidepool volume and conducted a sea urchin survey – visually identifying the number of urchins from 3 species. I purposely selected pools with sandy bottoms so I could sample the sediment for microplastics.
After my field work, I then made a modified sediment-microplastic isolation unit (SMI) to separate out the microplastics from the samples. A zinc chloride solution was used as the separation medium. The SMI was based on the prototype in Coppock, et. al. (2017) but modified so I could use materials available on Kauai. I then ran a correlation analysis on the number of microplastic strands per sample to the density of sea urchins (urchins/cubic meter) of all four pools.
The analysis found that tidepool samples contained more microplastics than the control sample. This indicates that tidepools collect and hold microplastics. The correlation coefficient of -0.67 shows a weak negative correlation between the microplastic concentration and sea urchin density.
I would like to thank my Biology teacher Mr. Matthews who inspired me to do research. I also want to thank the authors of Coppock, et. al. (2017) whose sediment microplastic isolation unit prototype inspired me to
make my own version.
Coppock, Cole, Lindeque , Queirós, and Galloway (2017, November). A small-scale, portable method for extracting microplastics from marine sediments. Environmental Pollution.