Seasonal and interannual variability of ocean color and composition of phytoplankton communities in the North Atlantic, equatorial Pacific and South Pacific

Abstract

Monthly averaged level-3 SeaWiFS chlorophyll concentration data from 1998 to 2001 are globally analyzed using Fourier's analysis to determine the main patterns of temporal variability in all parts of the world ocean. In most regions, seasonal variability dominates over interannual variability, and the timing of the yearly bloom can generally be explained by the local cycle of solar energy. The studied period was influenced by the late consequences of the very strong El Niño of 1997-98. After this major event, the recovery to normal conditions followed different patterns at different locations. Right at the equator, chlorophyll concentration was abnormally high in 1998, and then decreased, while aside from the equator, it was low in 1998, and increased later when equatorial upwelled waters spread poleward.

Evaluation of the global oceanic isoprene source and its impacts on marine organic carbon aerosol

“…However, the low NO x concentrations characteristic of the remote marine atmosphere (on the order 10 pptv or less) will produce substantially smaller SOA yields through this process. Ervens et al (2008) found yields of between 2 and 3% at [C 5 H 8 ]/[NO x ] concentration ratios similar to those found under typical marine conditions with our 1.9 Tg/yr isoprene source (∼30pptv isoprene, ∼10 pptv NO x ). These are close to the 3% yields observed during studies of isoprene SOA production under gas-phase oxidation in low-NO x conditions (Kroll et al, 2006).…”

“…An increase in the isoprene SOA yield would translate to an increased significance for oceanic isoprene in marine OC. Yields of SOA from in-cloud processing of isoprene oxidation products of up to 42% have recently been observed under elevated NO x ([C 5 H 8 ]/[NO x ] ∼0.05) (Ervens et al, 2008). An upper limit of 0.78 TgC/yr of SOA from the top-down 1.9 Tg/yr isoprene source is obtained by applying the maximum 42% SOA yield globally.…”

“…Recent advances in satellite retrieval algorithms have allowed the spatial distribution of four different PFTs in the global oceans to be obtained from space for the first time. The method relies on the detection of spectral signatures from water-leaving radiances in the visible wavelengths, previously determined using the SeaWiFS (Sea Wide Field-ofview Sensor) satellite instrument and in-situ measurements from ship cruises (Dandonneau et al, 2004). The PHYSAT model (Alvain et al, 2005), uses this spectral information from SeaWiFS to produce global distributions of the dominant PFTs from four major phytoplankton groups (haptophytes, prochlorococcus, cyanobacteria and diatoms).…”

ENSO related variations in biogeochemistry of AA and HA in settling particles along the equatorial Pacific Ocean

“…Moreover, an eastbound subsurface water current, equatorial undercurrent (EUC), is also important from the viewpoint of affecting the sinking particle flux along the equator (Hansell et al, 1997). Satellite-based SeaWiFS data and an in-situ data study suggest interannual and seasonal changes in chlorophyll-a in the equatorial region (Dandonneau et al, 2004), and unusually large-scale planktonic blooms occurring under changing ENSO conditions in the western and eastern ends of the study area (Ryan et al, 2002).…”

“…Owing to effect of ENSO fluctuations, changes in the diversity of microphytoplankton in the equatorial Pacific (Liu et al, 1996), copepods along the west coast of Baja California, Mexico (HernandezTrujillo, 1999), and fish in the global ocean (Worm et al, 2005) have been widely reported. Since plankton species composition affects the efficiency of the biological carbon pump (Dandonneau et al, 2004), a change in plankton diversity may be reflected in minor changes in AA and HA compositions of settling particles, as revealed by the discriminant analysis. In a few recent studies, changes in AA composition have been attributed to the changes in planktonic diversity (Braven et al, 1995;Petersson and Floderus, 2001;Kalachova et al, 2004;Brucet et al, 2005).…”