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Abstract Climate change is projected to modify the physical and chemical environment of the ocean, but the quantitative impact on the distribution of phytoplankton groups is unclear. Most Earth System Models (ESMs) predict future declines of phytoplankton in low latitude waters, contradicting observations showing that picophytoplankton can reach high abundance in warm waters. Here, we used a historic and three climate scenarios along with quantitative niche models to projectProchlorococcus,Synechococcus, and picoeukaryotic phytoplankton distributions for the year 2100. First, we found global responses with up to 50% and 9% increase forProchlorococcusandSynechococcusabundances, respectively, and 8% decrease for picoeukaryotic phytoplankton. All groups increased in abundance at low latitude, andSynechococcusand picoeukaryotic phytoplankton showed bands of decreases and increases in mid‐ and high‐latitudes, respectively.Prochlorococcustemporal trends were consistent among ESMs and increased with the strength of the scenario, whileSynechococcusand picoeukaryotic phytoplankton showed mixed results. Second, we evaluated sources of uncertainty associated to future projections. The anthropogenic uncertainty, associated to climate scenarios, increased with time and was relevant forProchlorococcus. The environmental and biological uncertainty, associated to ESMs and niche models, respectively, represented the largest fraction but differed among lineages. Quantifying uncertainties is key because the predicted differences in the future distribution and abundance can have large‐scale consequences on ocean ecosystem functioning.
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High‐frequency sampling captures variability in phytoplankton population‐specific periodicity, growth, and productivity
Abstract The Hawaii Ocean Time‐series (HOT) at Station ALOHA (22.75°N, 158°W) in the North Pacific Subtropical Gyre (NPSG) serves as a critical vantage point for observing plankton biomass production and its ecological implications. However, the HOT program's near‐monthly sampling frequency does not capture shorter time scale variability in phytoplankton populations. To address this gap, we deployed the SeaFlow flow cytometer for continuous monitoring during HOT cruises from 2014 to 2021. This approach allowed us to examine variations in the surface abundance and cell carbon content of specific phytoplankton groups: the cyanobacteriaProchlorococcus,Synechococcus, andCrocosphaeraas well as a range of small eukaryotic phytoplankton ( 5 μm). Our data showed that daily to monthly variability inProchlorococcusandSynechococcusabundance matches seasonal and interannual variability, while small eukaryotic phytoplankton andCrocosphaerashowed the highest seasonal and interannual fluctuations. The study also found that eukaryotic phytoplankton andCrocosphaerahad higher median cellular growth rates (0.076 and , respectively) compared toProchlorococcusandSynechococcus(0.037 and , respectively). These variances in abundance and growth rates indicate that shifts in the community structure significantly impact primary productivity in the NPSG. Our results underscore the importance of daily to monthly phytoplankton dynamics in ecosystem function and carbon cycling.
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- Award ID(s):
- 2241005
- PAR ID:
- 10542500
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Limnology and Oceanography
- Volume:
- 69
- Issue:
- 11
- ISSN:
- 0024-3590
- Format(s):
- Medium: X Size: p. 2516-2531
- Size(s):
- p. 2516-2531
- Sponsoring Org:
- National Science Foundation
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