On the Relationship between a Novel Prorocentrum sp. and Colonial Phaeocystis antarctica under Iron and Vitamin B12 Limitation: Ecological Implications for Antarctic Waters

Abstract

We collected live mixed natural samples from the northeastern Ross Sea during the austral summer of 2017 and isolated a novel Prorocentrum sp. (Dinophyceae) associated with mucilaginous Phaeocystis antarctica (Coccolithophyceae) colonies. The haptophyte P. antarctica is a key species of the phytoplankton community in the Ross Sea, where blooms are subjected to iron limitation and/or co-limitation with other micronutrients (e.g., vitamin B12) during the summer. We first performed preliminary genetic analyses to determine the specific identity of the novel Prorocentrum sp., which indicated that it represented a previously undescribed species. The formal description of this new species is in process. To further assess its relationship with P. antarctica, we obtained their monospecific and mixed cultures and evaluated their responses to different irradiance levels and iron and vitamin B12 limitation. Our results indicated differential susceptibility of the two species to iron limitation and differential photosynthetic plasticity under high irradiance. Iron limitation reduced colony formation in P. antarctica and decreased the chlorophyll-a content in Prorocentrum sp., whereas B12 limitation did not affect growth or photosynthetic efficiency in either species. In addition, P. antarctica could photosynthesize efficiently under different irradiance levels, due to its ability to modulate the light adsorption cross-section of PSII, whereas Prorocentrum sp. exhibited lower photosynthetic plasticity and an inability to modulate both the maximum photochemical efficiency and effective adsorption cross-section of PSII under high irradiance. The trophic interaction between Prorocentrum sp. and P. antarctica could present ecological implications for the food webs and biogeochemical cycles of the Antarctic ecosystem. Considering the predicted climate-driven shifts in global ocean surface light regimes and changes in iron or vitamin B12 transfer, which are most likely to impact changes in the phytoplankton community structure, our results present implications for carbon export to deeper waters, ecological functioning, and associated biogeochemical changes in the future.

Spatial-Related Community Structure and Dynamics in Phytoplankton of the Ross Sea, Antarctica

“…In addition, an intense bloom of loricate choanoflagellates in the central Ross Sea has been reported by Escalera et al (2019) and a discovery of a novel dinoflagellate species (Prorocentrum sp.) associated with mucilaginous Phaeocystis antarctica colonies has been reported by Bolinesi et al (2020). Therefore, these findings could help to reevaluate the role of the planktonic mixotrophic and heterotrophic compartment in the Antarctic food web, also in relation with recently reported changes within phytoplankton communities (e.g., Montes-Hugo et al, 2009;Kaufman et al, 2017;Mangoni et al, 2019).…”

Molecular phylogeny of the spiny‐surfaced species of the dinoflagellate Prorocentrum with the description of P. thermophilum sp. nov. and P. criophilum sp. nov. (Prorocentrales, Dinophyceae)

“…It is especially abundant in the Ross Sea where it has been isolated in 2017, 2019, and 2021. The species is associated with the blooms of the haptophyte Phaeocystis antarctica (Bolinesi et al 2020). Due to the small size (9-12 lm), the species is inefficiently sampled by plankton nets, and it appears in non-concentrated water samples.…”

Shark Microbiome Analysis Demonstrates Unique Microbial Communities in Two Distinct Mediterranean Sea Shark Species

“…DNA was extracted from the skin samples using a modified phenol–chloroform extraction protocol [ 23 , 24 ] and used for the shark species identification. DNA visualization was performed by agarose gel electrophoresis, and DNA quantification was determined by NanoDrop spectrophotometer (Thermo Fisher Scientific, Roma, Italy).…”