Microbial rhodopsins are simple light-harvesting complexes that, unlike chlorophyll photosystems, have no iron requirements for their synthesis and phototrophic functions. Here, we report the environmental concentrations of rhodopsin along the Subtropical Frontal Zone off New Zealand, where Subtropical waters encounter the iron-limited Subantarctic High Nutrient Low Chlorophyll (HNLC) region. Rhodopsin concentrations were highest in HNLC waters where chlorophyll-a concentrations were lowest. Furthermore, while the ratio of rhodopsin to chlorophyll-a photosystems was on average 20 along the transect, this ratio increased to over 60 in HNLC waters. We further show that microbial rhodopsins are abundant in both picoplankton (0.2–3 μm) and in the larger (>3 μm) size fractions of the microbial community containing eukaryotic plankton and/or particle-attached prokaryotes. These findings suggest that rhodopsin phototrophy could be critical for microbial plankton to adapt to resource-limiting environments where photosynthesis and possibly cellular respiration are impaired.
Bibliographical noteFunding Information:
The authors would like to thank the captain and crew of R/V Polaris II, and Hannah Adams for her assistance with pigment extractions. This research was supported by Grant No OCE1924464 from the United States National Science Foundation (NSF) to L.G.‐C. and by Grant No 2019612 from the United States‐Israel Binational Science Foundation (BSF) to L.S., as well as the Rutherford Discovery Fellowship to F.B.
© 2021 Society for Applied Microbiology and John Wiley & Sons Ltd.
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Agricultural and Biological Sciences (miscellaneous)