2015 Annual Science Report

Massachusetts Institute of Technology Reporting  |  JAN 2015 – DEC 2015

Evolution of Precambrian Life and Primary Producers

Project Summary

Life on Earth is sustained by photosynthesis, both on land and in the sea. New research provides novel perspectives on the evolution of diatoms, responsible for 25% of all photosynthesis in today’s oceans. Also, new fossils from Russia strengthen the relationship between early eukaryotes and environmental conditions in Proterozoic oceans.

4 Institutions
3 Teams
4 Publications
1 Field Site
Field Sites

Project Progress

Research in this area focused on three distinct projects. The first, led by MIT postdocotral fellow, Benjamin Kotrc, completed long term research on the evolution of diatoms, among Earth’s most abundant primary producers. Morphospace analysis corroborates the hypothesis that diatoms achieved most of their present day structural variety early in their evolutionary history and also shows that morphospace studies can be influneced by sampling insentisty, just as tabulations of species richness can (Kotrc and Knoll, 2015, a b, c).

In the second, we completed research on well preserved microfossils from ca. 1500 million year old rocks in Russia. Samples of carbonaceous shale from the Kaltasy Formation were collected from drill cores and processed in the lab for microfossils. Abundant and well preserved microfossils document 34 distinct biological entities (Figure 1), including some problematic eukaryotes. Ornamented microfossils found in coastal successions of other lower Mesoproterozoic basins are absent, but large filamentous microfossils interpreted as possible benthic photosynthetic eukaryotes are recorded, drawing comparisons to relatively deep water shales in Siberia. In overall aspect, the Kaltasy microfossils are consistent with other broadly co-eval assemblages, but they highlight the importance of environment, as well as age, in determining the distributions of remains that record the early diversification of marine eukaryotes (Sergeev et al., 2015; a second, monogrpahic paper is currently in review).

Figure 1. Microfossils recovered from 1500 ma basinal shales in Russia (single scale bars = 10 microns; double bars = 100 microns)

In the third, we completed field-based research, conducted with members of the Australian Centre for Astrobiology, on ca. 2400 million year old carbonates from northwestern Australia (Figure 2), documenting distinctive stromatolite morphlogies at a time of large-scale environmental change — the Great Oxygenation Event.

Figure 2. Distinctive, void-rich stromatolites from 2400 Ma carbonates in Australia.

Finally, we contributed two reviews, one of early microbial evolution (Knoll, 2015) and one discussing the evolution of biomineralization by protists and its biogeochemical consequences (Knoll and Kotrc, 2015)