Premium
A small marine biosphere in the Proterozoic
Author(s) -
Laakso Thomas A.,
Schrag Daniel P.
Publication year - 2019
Publication title -
geobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.859
H-Index - 72
eISSN - 1472-4669
pISSN - 1472-4677
DOI - 10.1111/gbi.12323
Subject(s) - biosphere , proterozoic , nutrient , photosynthesis , environmental science , primary production , primary producers , limiting , phosphorus , heterotroph , ecology , oceanography , ecosystem , geology , biology , chemistry , phytoplankton , botany , mechanical engineering , paleontology , tectonics , organic chemistry , bacteria , engineering
Abstract The riverine supply of the globally limiting nutrient, phosphorus, to the ocean accounts for only a few percent of nutrient supply to photosynthetic organisms in surface waters. Recycling of marine organic matter by heterotrophic organisms provides almost all of the phosphorus that drives net primary production in the modern ocean. In the low‐oxygen environments of the Proterozoic, the lack of free oxygen would have limited rates of oxic respiration, slowing the recycling of nutrients and thus limiting global rates of photosynthesis. A series of steady‐state mass balance calculations suggest that the rate of net primary production in the ocean was no more than 10% of its modern value during the Proterozoic eon, and possibly less than 1%. The supply of nutrients in such a world would be dominated by river input, rather than recycling within the water column, leading to a small marine biosphere found primarily within estuarine environments.