Coexistence of dominant marine phytoplankton species sustained by nutrient specialization

Abstract

Prochlorococcus and Synechococcus are the two dominant picocyanobacteria in the low-nutrient surface waters of the subtropical ocean, but the basis for their coexistence in these biomes is still unclear. Here we combine in situ microcosm experiments and an ecological model to show that this coexistence can arise from specialization in the uptake of distinct nitrogen (N) substrates. In field incubations, the response of both Prochlorococcus and Synechococcus to nanomolar N amendments demonstrates N limitation of growth in both populations, but Prochlorococcus showed a higher affinity to ammonium whereas Synechococcus was more adapted to nitrate uptake. A simple ecological model demonstrates that the differential nutrient affinity of these species can explain their coexistence. Phylogenetic analysis of the presence of nitrate reductase and nitrite reductase further support the higher nitrate affinity of Synechococcus compared to Prochlorococcus. Our study suggests that the evolution of differential nutrient affinities is an important mechanism for sustaining coexistence of species under resource competition.

Diel Partitioning in Microbial Phosphorus Acquisition in the Sargasso Sea

“…Likewise, we found diel gene transcript abundances for phosphonate transporters with the heterotrophic bacterial order Rhodospiralles expressing phosphonate transporters in the morning (coinciding with phosphate transporters), Rhodobacter during the day, Prochlorococcus at dusk (coinciding with its phosphate transporters), and Synechococcus overnight (following its phosphate transporters). Our results suggest temporal partitioning of uptake for both phosphorus species, and coinciding timing of phosphate and phosphonate uptake on a taxon-by-taxon basis further suggests that substrate-level specialization is not necessarily sufficient to avoid competition for this scarce resource [25], and further suggests diel cycles in transporter gene transcription are not directly tied to changes in the relative pools of different phosphorus species.…”

“…Collectively, these results suggest temporal partitioning of uptake for both phosphorus species, and coinciding timing of phosphate and phosphonate uptake on a taxon-by-taxon basis further suggests that substrate-level specialization is not necessarily sufficient to avoid competition for this scarce resource [26], and further suggests diel cycles in transporter gene transcription are not directly tied to changes in the relative pools of different phosphorus species. Complementary evidence for diel temporal niche partitioning for distinct nutrients (N in the North Subtropical Pacific [28] and P in the Sargasso as shown here) may be indicative of complex, community-level metabolic plasticity across ocean basins.…”

Interannual changes in nutrient and phytoplankton dynamics in the Eastern Mediterranean Sea (EMS) predict the consequences of climate change; results from the Sdot-Yam Time-series station 2018-2022

“…The increase in NH 4 in the water column corresponded to the only period when Prochlorococcus was found throughout the water column (Figure 7). It is generally observed that Prochlorococcus uses preferentially NH 4 for its N source and shows a limited ability to use nitrate (Masuda et al 2023). Surprisingly, DIP did not increase even in the December 2021 sampling immediately after Storm Carmel.…”