The Need for More Research in How Microplastics Affect Crab Species

I have always found the topic of plastics in our oceans fascinating due to how destructive they can be individual organisms, a whole species, and the entire ecosystem. Plastics are not just a problem due certain marine animals eating them and dying or because of animals becoming entangled in them, but they also break down further into microplastics. 80 to 85% of marine pollution is caused by plastics, and these plastics breakdown into microplastics by UV light (Auta et. al, 2017). 

These plastics are also easier to consume due to their small size making them a threat to most marine biota, and consuming these plastics has led to problems with reproduction and growth rate (Auta et. al, 2017). However, I wanted to zone in crustaceans (crabs to be more specific) since many species will spend their time both as marine and terrestrial which means they are exposed to microplastics in the water and microplastic that may be found in sediment.

European green crabs have been found to not only consume microplastics, but microplastics will also get trapped in their gills as they breathe. These microplastics can persist in their gills for up to 21 days and in their muscles for up to 14 days (Beckett et. al, 2014). Mud crabs have been found to take in more microplastics and store them in their tissues than the filter feeder, eastern oyster (Donnelly et. al, 2018).  Fiddler crabs were also found to have microplastics in their gills, stomach, and hepatopancreas which shows that microplastics can go to other organs (Appel et. al, 2015). These are just a few examples of crabs that are being affected by microplastics; however, I could have listed even more. There are a multitude of papers that look into microplastics in crab species, but it would be way too many for me to list. It seems that most crab species are taking in these microplastics.

Most of the research that I could find pertaining to crabs and microplastics was if crabs had the presence of microplastic in their tissues, but it does not seem like much work has been done pertaining to how these microplastics affect a crab’s function and their development. I was able to find that crabs who have breathed in microplastics have been found to have trouble taking in oxygen, and these affects would last for at least 16 hours (Galloway et.al, 2016), and that female mole crab had an increase in mortality and decrease in retention of egg clutches (Granek et.al, 2019). 

I believe that more research needs to be done on the effects that microplastics have on different crab species. The two papers I mentioned above only looked at mole crabs and green crabs, but I don’t feel like we can apply those findings in these papers to all crabs even though I do believe that it shows that these studies are warranted for other species. With the amount of studies showing that a lot of crab species are consuming and breathing in microplastics, I hope that this urges researchers to find out more about the effects such as whether it can be transferred to their larvae, how does it affect certain organ functions, does it have an effect on development, etc. I want to believe that these microplastics do have an effect on all the problems that I mentioned, but I can’t be sure until research is done.

I also believe that it is also important to look into how these microplastics are moving from the crabs to their predators. In many papers that I have read, most of the time microplastics are transferred from prey to predator when the predator consumes them, but there are few studies where this is not the case. This is important since so many species eat crabs. Everything from birds to fish to humans and even other crabs consume crabs, and these other species may now be vulnerable to microplastics.

Overall, I believe that more work should be done to look at microplastics. They are abundant, and they have even been found in arctic regions where there is very little to no human activity (Auta et. al, 2017). The amount of these microplastics keep growing as well, and they may have even more severe impacts on certain marine species than we thought they would. Understanding microplastics and how they affect different organisms will help us get a better grasp of how to deal with microplastic and fully realize the threat that they are.

 

Citations:

Appel, D., Brennecke, D., Costa, T.M.M., Ferreira, E.C., Gama, B.A.P., and Lenz, M.

(2015). Ingested microplastics (>100um) are tranlocated to organs of the tropical fiddler crab Uca rapax. Marine Pollution Bulletin. 96(1-2). 491-495.

Auta, H.S., Emenike, C.U., and Fauziah, S.H. (2017). Distribution and importance of

microplastics in the marine environment: A review of the sources, fate, effects, and potential solutions. Environment International. 102, 165-176. https://doi.org/10.1016/j.envint.2017.02.013.

Beckett, S.J., Galloway, T.S., Goodhead, R.M., Lewis, C., Moger, J., Tyler, C.R., and

Watts, A.J.R. (2014). Uptake and Retention of Microplastics by Shore Crab

Carcinus maenas. Environmental Science and Technology. 48(15). 8823-8830.

Donnelly, M.J., Waite, H.R., and Walters, L.J. (2018). Quantity and types of

microplastics in the organic tissues of the eastern oyster Crassostrea virginica and the Atlantic mud crab Panopeus herbstii from a Florida estuary. Marine Pollution Bulletin. 129(1). 179-185. https://doi.org/10.1016/j.marpolbul.2018.02.026

Galloway, T.S., Goodhead, R., Lewis, C., Moger, J., Urbina, M.A., and Watts, A.J.R.

(2016). Effect of Microplastics on the Gills of the Shore Crab Carcinus maenas. Environmental Science and Technology. 50(10). 5364-5369.

Granek, E.F., Horn, D.A., and Steele, C.L. (2019). Effects of environmentally relevant

    concentration of microplastic fiber on Pacific mole crab (Emerita analoga) mortality and

    reproduction.