Vertical and temporal distribution of chytrids infecting diatoms in the Gulf of Naples (Italy, Mediterranean Sea)

摘要

The presence of phytoplankton parasites along the water column was explored atthe Long-TermEcological Station MareChiara (LTER-MC)in the Gulf of Naples(Mediterranean Sea) in October 2019. Microscopy analyses showed diatoms dominatingthe phytoplankton community in the upper layers (0–20m). Metabarcodingdata from the water column showed the presence of Chytridiomycota predominantlyin the upper layers coinciding with the vertical distribution of diatoms. Laboratoryincubations of natural samples enriched with different diatom cultures confirmedparasitic interactions of some of those chytrids—includingmembers of Kappamyces—withdiatom taxa. The temporal dynamics of diatoms and chytrids was also exploredin a 3-yearmetabarcoding time-series(2011–2013)from surface waters of the studyarea and in sediment samples. Chytrids were recurrently present at low relative abundances,and some taxa found to infect diatoms in the incubation experiments werealso identified in the ASV time-series.However, co-occurrenceanalyses did not showany clear or recurrent pairing patterns for chytrid and diatom taxa along the 3 years.The chytrid community in the sediments showed a clearly different species compositioncompared with that recorded in the water column samples, with higher diversityand relative abundance. The combination of observations, incubations, and metabarcodingconfirmed that parasites are a common component of marine protist communitiesat LTER-MC.Host–parasiteinteractions must be determined and quantified tounderstand their role and the impact they have on phytoplankton dynamics.