Dynamics of phytoplankton community structure in the South China Sea in response to the East Asian aerosol input

[摘要] Recent studies have demonstrated atmospheric deposition as an importantsource of bioreactive compounds to the ocean. The South China Sea (SCS),where aerosol loading is among the highest in the world, however, is poorlystudied, particularly on the in situ response of phytoplankton communitystructures to atmospheric deposition. By conducting a series of microcosmbioassays at different hydrographical locations and simulating differentaerosol event scales, we observed both positive and negative responses tothe input of East Asian (EA) aerosol with high nitrogen (N) and trace metalcontents, in terms of biomass, composition and physiological characteristicsof phytoplankton communities. High levels of aerosol loading relievedphytoplankton nitrogen and trace metal limitations in SCS, and thusincreased total phytoplankton biomass, enhanced their physiologicalindicators (e.g. photosynthetic efficiency) and shifted phytoplanktonassemblages from being dominated by picoplankton to microphytoplanton,especially diatoms. However, under low levels of aerosol loading, thecomposition shift and biomass accumulation were not apparent, suggestingthat the stimulation effects might be counterbalanced by enhanced grazingmortality indicated by increased abundance of protist grazers. Trace metaltoxicity of the aerosols might also be the reason for the reduction ofpicocyanobacteria when amended with high EA aerosols. The magnitude andduration of the deposition event, as well as the hydrographical and trophicconditions of receiving waters are also important factors when predictingthe influence of an aerosol deposition event. Our results demonstrateddifferent responses of phytoplankton and microbial food web dynamics todifferent scales of atmospheric input events in SCS and highlighted the needfor achieving an accurate comprehension of atmospheric nutrient on thebiogeochemical cycles of the oceans.

[学科分类] 地球化学与岩石