Paleaeobioindicators II

This one is more focused on paleooceanography (Environmental Archives - Oceans)

Overview

Form 50% of global primary production

Marine algae with calcaerous shells
Form massive blooms in the Arctic ocean
Only in marine sediments
Even if the hard shell is not preserved (below the calcite compensation depth), their biomarkers like alkenones, steoles and pigments can be preserved in the sediement

Second most important oceanic primary producer (after diatoms), but they can also be mixotrophs or heterotrophs (diverse group)
A few groups form resting stages called cysts which can be studied
- They will preserve even in environments where silica and calcite dissolve
Based on their current distribution/temperature optima you can calculate past sea surface temperature
Sometimes the cysts are difficult to assign to a taxa and need to be cultured in a lab to identify (even if they're hundreds of years old)
- These can be used to identify older species
- Also because of this - if the conditions are right, tons of spores can wake up into a massive algal bloom (red tide)

Another kind of calcaerous plankton forming calcaerous ooze (zooplankton)
Also only in marine sediments
There are both planktic and benthic species but mostly benthic
- Benthic species are less well known
They can form symbiosis with other species
Some species incorporate bits of sand or other materials into their testa
Isotopic and geochemical analysis of the testa can be used to reconstruct
Similar method to plant macrofossil analysis - using a stereomicroscope since they are quite large (0.01 - 100mm)
- Unlike many other species you need a light microscope and slide mount (diatoms, pollen, etc)
Classic proxy for sea surface temperature, water depth, bottom water oxygenation, productivity and carbon cycling.
They are distributed according to latitude - polar seas only have one species