Philadelphia’s Diatom Archive Is a Way, Way, Wayback Machine

As sea levels rise, the sea has dominated the once dynamic coastal margin. The sea level in New Jersey has risen by more than twice the global average over the last 100 years. The sea could rise by over a meter by the year century's end.

Several of the marshes along New Jersey's coastline have already succumbed to the sea due to the dramatic rise in sea level. Environmental monitoring only dates back a few decades so it's hard to know the full extent of the wetlands' loss.

Ecological restoration is difficult if there is no sense of a wetlands natural environment. Enache says that having that information is important. You are not in the light without it. The academy has a cache of diatoms.

Sea level rise is something New Jersey is familiar with. Sea ice slurped up stores of seawater when New Jersey was covered in ice. The New Jersey coastline is more than 100 kilometers farther into the Atlantic Ocean than it was around 18,000 years ago.

Sea levels climbed after the last ice age ended. It was caused by retreating ice sheets. The combination of subsidence and melt proved to be a potent mix for sea level rise.

Walker looked at the past to put New Jersey's current sea level rise in perspective. We can project changes in the future if we understand how temperatures, atmosphere, and sea level changes are all connected.

She and her team looked at the shells of single-celled protists called foraminifera that are finely tailored to the environment. They are a good proxy for reconstructing sea level shifts. New Jersey's coast is experiencing the fastest rise of sea level in 2,000 years because of certain foraminifera species.

In order to understand how coastal marshes responded to the rising sea, the NJDEP wanted to use diatoms. Each of the diatom species is very sensitive to the environment. The Nitzschia microcephala's shells are a sign of nitrogen pollution. The Diploneis smithii, a species that has a slender trilobite, prefers the salty water. Their inland location is a good indication of the intrusion of the sea in the past.

To find out where these indicators used to be, the NJDEP sent a team of researchers into several marshes along the coastline, ranging from heavily polluted wetlands in the north to near-pristine tidal marshes in the south. They cored into the marsh muck at all of the sites. As you cut deeper, you are going back in time from the steaming pancake just off the griddle to the soggy pancake deposited at the bottom of the stack. The researchers traveled back in time. They collected nine core from five wetlands.