Lagrangian studies of marine production: a multi-method assessment of
productivity relationships in the California Current Ecosystem upwelling
region
Abstract
Upwelling of nutrient rich waters along continental shelves generates
highly productive marine ecosystems affectingplanktonic communities from
coastal to offshore domains. Methods to constrain pelagic productivity
are often based on different physiological or ecosystem processes, hence
describe different biogeochemically important processes. Here, we
present a multi-method process-oriented investigation of diverse
productivity measures in the California Current Ecosystem (CCE)
Long-Term Ecological Research study region, a complex physical
environment. The data are from seven multi-day deployments over two
field expeditions (spring 2016 and summer 2017) and cover a transition
region from high to low productivity. Employing a Lagrangian study
design, we aimed to follow the water parcels over several days,
comparing 24 h in-situ measurements (C and NO, uptake, sediment trap
export, dilution estimates of phytoplankton growth and microzooplankton
grazing) with high-resolution productivity measurements by Fast
Repetition Rate Fluorometry (FRRF) and Equilibrium Inlet Mass
Spectrometry (EIMS). Our results show the importance of accounting for
temporal and fine spatial scale variability when estimating ecosystem
production. FRRF and EIMS measurements resolved diel patterns in gross
primary and net community production. Diel productivity changes agreed
well with comparable more traditional measurements. While differences in
productivity metrics calculated over different time intervals were
considerable, as those methods rely on different base assumptions, our
data can be used to explain ecosystem processes which would otherwise
have gone unnoticed. The processes resolved from this method comparison
can help to further our understanding of the coupling and decoupling of
surface productivity and potential carbon burial in coastal and offshore
ecosystems.