Paleoecological reconstruction of coastal landscape change in James Bay, Canada

The reconstruction of past ecosystems is based on the investigation of individuals and communities of ancient organisms and their interactions with the changing environment.  After the death of the organisms traces of their existence remain preserved in soils and sediments. These traces include pollen grains from flowering plants, spores from non-vascular plants like mosses or some vascular plants like ferns, horsetails and Lycopods, and fossilized body parts (macrofossils) of plant and animals (e.g., insect exoskeleton, leaves, seeds).  

 Some marine or lacustrine single-cell plankton species form a cell wall (theca) resistant to decay and these preserve as fossils. Together with pollen and spores they form a category of micro-fossils known as PALYNOMORPHS. 

Because it combines a variety of different environmental indicators, palynomorph analysis is one of the best tools to reconstruct former ecosystems.

In James Bay the the shorelines are retreating due to isostatic rebound and the former sea floor is becoming dry land. Up until 9, 000 years ago, the region was covered by a huge ice sheet. The weight of the ice depressed the land, but eventually the ice sheet disappeared due to a warming climate. Since then the land began uplifting back to its original elevation. This process is called isostatic rebound and it is still happening today.

Part of my research in James Bay tries to trace back the retreating shoreline and understand the landscape change processes associated with shoreline retreat. One of the most vivid processes of landscape change on these retreating coastlines is the transformation of near-shore marine environments into inter-tidal ecosystems such as tidal flats and salt marshes. With continuing rebound salt marshes are replaced by fresh water ecosystems such as fens or bogs.

How fast are these ecosystems changing? How fast did they change in the past? How does a slow changing coastline look like as compared to a fast changing one? How does the differential rate of landscape change affect resource availability and human occupation? These are some of the questions I try to find answers to.

Pollen types common in eastern James Bay salt marshes

Ruppia maritima

Carex spp.

Potentilla spp.