Diversity of parasitic fungi associated with phytoplankton in Hawaiian waters

ABSTRACT

Parasitic fungi infect large phytoplankton species in freshwater, playing a fundamental role in their host's health and habitat range. However, those associated with the marine phytoplankton community remain largely unknown. This study investigated the infectivity and biodiversity of phytoplanktonic parasitic fungi in three ecosystems of Hawaiian waters, with contrasting trophic statuses – oligotrophic (Waikiki Beach), mesotrophic (Kaneohe Bay) and eutrophic (Ala Wai Canal). The occurrence of fungal parasites (e.g. attached spores) was primarily associated with diatom cells (i.e. the most vulnerable populations) as well as various pelagic fungal forms (i.e. zoosporic, yeast and mycelial), suggesting the coexistence of different fungal lifestyles. Phylogenetic analysis categorized our retrieved fungal sequences from six clone libraries into five taxonomic orders that belonged to the phyla of Ascomycota and Basidiomycota, along with culturable fungal endophytes and pathogens from diverse host resources. The great majority of these sequences (∼93%) were associated with three taxonomic orders of Ascomycota (Pleosporales, Hypocreales and Saccharomycetales). There was greater infectivity and diversity of fungal species in eutrophic (Ala Wai) waters compared with oligotrophic (Waikiki Beach) waters, and both factors were significantly (P < 0.05) correlated to nutrient P levels at the sampling sites. This is the first report of the occurrence and phylogenetic diversity of phytoplankton-associated fungi in Hawaiian waters and may bring new insights into our understanding of marine fungal communities.

RESPONSIBLE EDITOR:

• Mathias Middelboe

KEYWORDS:

• Diversity
• Hawaiian waters
• parasitic fungi
• phytoplankton

Ackowledgements

We thank the SOEST Flow Cytometry Facility, University of Hawaii at Manoa for their support during the sampling, sorting and epifluorescence microscopic analysis. We also thank Elliott Roberts for his help with English.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was partially funded by National Natural Science Foundation of China grant 31170109 (GYW) and NOAA grant