Distribution and Elemental Composition of Picoplankton in the North Pacific Ocean
Date
2021-01-05T12:38:51Z
Authors
Bradet-Legris, Jonathan
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Abstract
Marine picoplankton account for a considerable portion of primary
production in the Ocean, particularly in the oligotrophic regions. Picoplankton
are dominated by three major groups: Prochlorococcus, Synechococcus
and picoeukaryotes, whose populations are controlled by many complex interacting
factors. We analyze a rich dataset from a cruise in the North
Pacific Ocean to model the distribution and elemental composition of each
picoplankton group using only environmental data as predictors. Linear regression,
generalized additive models, and random forests were used to make
models of phytoplankton abundances and carbon biomasses. Elemental composition
for each phytoplankton group was modeled using Bayesian linear regression
by regressing elemental C, N, and P concentrations on picoplankton
biovolumes. Our species distribution models show temperature and salinity
are consistently the most important predictors to explain variation in abundance
and biomass. Along the full transect, nutrient concentrations (PO4,
Fe, Mn, Cu) provide useful insights on sharp population shifts over short
distances and our results support the claim that iron and phosphorus are
limiting nutrients in the North Pacific Ocean’s oligotrophic gyre. Our elemental
quota model show that the composition and cellular C:P, N:P and
C:N ratios varies substantially among the three picoplankton groups. Average
carbon content for Prochlorococcus, Synechococcus and picoeukaryotes
were 167 fg C/um (95% CR: 6:89-457:8), 538 fg C/um (95% CR: 307:2-
771:5), and 297 fg C/um ( CR: 13:74-804:6) respectively. This model provides
a method for estimating individual elemental content of each phytoplankton
group, which is otherwise unmeasurable directly from field samples.
Description
Keywords
Statistics, Oceanography