Colonization of Microplastics by Mangrove- and Seaweed- Associated Fungi

Colonization of Microplastics by Mangrove- and Seaweed- Associated Fungi

Joannalyn S Montemayor1,2,3,4*, Thomas Edison E dela Cruz1,2,4, Nikki Heherson A Dagamac,1,3,4, and Melfei E Bungihan1,2,5

1The Graduate School, University of Santo Tomas, España Blvd. 1015 Manila, Philippines

2Fungal Biodiversity, Ecogenomics & Systematics-metabolomics (FBES) Group, Research Center for the Natural and Applied Sciences, University of Santo Tomas, España Blvd. 1015 Manila, Philippines,

3Initiatives for Conservation, Landscape, Ecology, Bioprospecting, and Biomodeling (ICOLABB) Group, Research Center for the Natural and Applied Sciences, University of Santo Tomas, España Blvd. 1015 Manila, Philippines,

4Department of Biological Sciences, College of Science, University of Santo Tomas, España Blvd. 1015 Manila, Philippines, and

5Department of Chemistry, College of Science, University of Santo Tomas, España Blvd. 1015 Manila, Philippines

*Email: joannalyn.montemayor.gs@ust.edu.ph

Microplastics, despite its small size of less than 5 mm, is one of the most prevalent debris in marine environments. In this study, we explored fungal endophytes (FE) associated with the mangrove Rhizophora apiculata and the seaweed Sargassum sp. for its ability to colonize microplastics. Thirty-four FE, of which 19 FE were isolated from the mangrove host while 15 selected FE were from the obtained seaweed. From these, we screened 15 selected FE for their ability to utilize low-density polyethylene (LDPE) using an agar-based method. Our results showed eight FE identified as Ramichloridium apiculatum, Flavodon flavus, Cladosporium haloterans, Westerdykella sp. (2 strains), Penicillium parvum, Xylaria feejeensis, and Talaromyces indigoticus as capable of growth on Czapek Dox agar with LDPE as the sole carbon source. The promising FE were further investigated for their ability to colonize microplastics as sole carbon sources using a microtiter plate assay. After 30 days of incubation, a colonization rate ranging from 4.17–100% was recorded for the different types of microplastics- plastic acetate, polyethylene, and polystyrene . With the recent increase in disposable mask pollution brought about by COVID-19, we also tested our fungi’s capacity to colonize KN95 masks. Cladosporium haloterans isolated from Sargassum sp. had the highest colonization rate at 100%, indicating its potential use for the bioremediation of disposable mask pollution. Scanning electron microscopy analysis revealed strong adhesion of fungal hyphae, as indicated by various holes, erosions, and deformations on the microplastics.