Microplastics-Bound Cyanobacteria: Toxicity and Carbon Contribution to the Chesapeake Bay Ecosystem

Proposed Research Project

This proposal aims to understand the diversity, toxicity, and biogeochemical impacts of microplastics-bound cyanobacteria in the Chesapeake Bay.

Researcher: Dr. Feng Chen

Expected outcomes:

Best Case: The best-case outcome includes: 

1. Microplastics-associated cyanobacterial isolates from the Bay and their toxicity; 
2. Carbon budget contributed by cyanobacteria on microplastics;
3. Microbial functions and interactions on the microplastics.

Worst Case: The worst-case outcome could be due to inaccurate estimates of cyanobacterial cells on microplastics.

What has happened so far: We have conducted in situ incubation of two major microplastics (polypropylene and polystyrene) in the Baltimore Inner Harbor and observed the development of biofilms and cyanobacteria on their surfaces. Microbial samples from the plastic surface were taken for sequencing analysis. Meanwhile, microplastic beads were smeared on the surface of cyanobacterial culture plates. We have observed the growth of different cyanobacteria on the culture plates after one month. Cyanobacteria tend to grow more slowly than most bacteria in the lab. It usually takes more than one month for cyanobacterial colonies to develop. Regardless, we have successfully transferred them to new culture plates two times now for further purification and isolation. We achieved a major step in getting cyanobacterial cultures from microplastics.

Probable Ancillary Benefits: Some of these Chesapeake Bay cyanobacteria could be novel and may have interesting biological and ecological implications. The project will train two interns. One undergraduate student from Baltimore Community College, Miranda Janello, is currently working on this project. A high school intern, Marti Anthony, will join us this summer to work on this project.

Results: We are making good progress towards our goals. Although cyanobacteria grew slowly on the plates, we increased the temperature and light to boost their growth. The morphology of cyanobacterial colonies was routinely checked under the microscope, and images were recorded. We have seen different morphotypes of cyanobacteria growing on culture plates, and they include both unicellular and filamentous cyanobacteria. The unicellular one appears to be Microcystis spp. The filamentous cyanobacteria appear to be more diverse and vary in shape and size. Together, these results suggest that various types of cyanobacteria can form biofilm on microplastics. Once cyanobacterial isolates are purified, we will identify them by sequencing their partial 16S rRNA gene and will perform toxin analysis. PCR primers have been ordered. We have measured the biomass increase on microplastics and will calculate the carbon contribution from microplastics-bound cyanobacteria.