Original Post by Genevieve Johnston-Grier:

1. The hydrologic complexity of salt and tidal freshwater marshes was clear from the websites and in the power points. The onset of global warming is now almost universally accepted (except maybe for Exxon/Mobil). What will happen to both kinds of marshes as sea level rises? Describe the hydrology then pick 2 other aspects of these wetlands to discuss the changes we will see in North America.

In the past normally salt and tidal freshwater marsh wetlands could keep pace with changing sea levels. But with climate change and the projected higher continued rates of sea-level rise at the coast will “drown” many coastal wetland ecosystems as they are unlikely to be able to accumulate sediment at a high enough rate to protect from ocean water intrusion. Where freshwater marshes at higher than sea level could accumulate settlement at rates that would protect from rising levels (Mitsch 2015). Sea levels could get to a point where many of the inland freshwater tidal marshes become saltwater marshes. And a large issue is that urbanization has cut into many of these existing freshwater marshes ecosystems and sometimes has cut them off from their historical water inner changes. At the coastal salt marshes could be protected if there is an increase of root material build-up in marsh soils while continuing the trapping of sediment that is carried into the marsh during flood tides that humiliates at the same rate as the seawater rises but without this occurring there will be a continued to erosion of marsh soils, die-off of plants, and the loss habitat the marshes create for species that rely on them (NOAA 2021).

The largest geomorphology change caused by climate change on salt and tidal marshes is likely the intrusion of saltwater from the oceans further inland into historically freshwater areas is going to cause a lot of changes to the functions of the stability of the marshes and how they function as ecosystems. With the loss of further salt marshes, property damage from storms and flooding will further increase and damage interdependent marine and wildlife land habitats (Binns 2021).

2. You are the manager of a wetland area that includes a salt marsh. You have noticed a portion of your marsh is dead and it happened suddenly. So you go to check the water and find the pH is 3, the salinity is low, and no crabs are present. You send a sediment sample to be tested and it comes back high in arsenic, cadmium, and chromium. What is the problem and how do you find the culprits?

As a manager of a wetland area that includes a salt marsh where a portion of the marsh has suddenly died off, a water pH of 3, and with sediment samples analyses test high in arsenic, cadmium, and chromium. The problem most likely is pollution from human developments and activities. My first step would be to set up wildlife cameras to rule out intentional dumping of pollution into the protected habitat. If this is ruled out I would check water sources interactions into the habitat for runoff of pollution from human developments and activities. I would also start a campaign with any local human habitat centers to make people aware of the effects dumping chemicals into sewer systems that go straight into the water table untreated affect the ecosystems of the wetlands around them. If there are nearby industrial centers that could be the highest potential source of the pollution entering the ecosystem, I would likely first attempt contact with the management to correct the situation and stop the pollution at its source potentially. And if a solution could not be reached by this contact, then possibly search for legal action against the sources to help fund the rehabilitation of the marsh area.

Resources

Bins, Holly, and Joseph Gordon. n.d. “11 Facts About Salt Marshes and Why We Need to Protect Them.” The Pew Charitable Trusts. Accessed July 6, 2021. https://www.pewtrusts.org/es/research-and-analysis/articles/2021/03/01/11-facts-about-salt-marshes-and-why-we-need-to-protect-them.

Flanagan, Kathryn. 2021a. “Salt Marshes.” PowerPoint.

Flanagan, Kathryn. 2021b. “Tidal Freshwater Marshes.” PowerPoint.

Mitsch, William J. and James G. Gosselink. 2015. Wetlands. 5th ed: John Wiley and Sons, Inc.

“Salt Marsh Ecology in an Era of Sea Level Rise.” 2021. NCCOS Coastal Science Website. February 5. https://coastalscience.noaa.gov/project/salt-marsh-ecology-era-sea-level-rise/.

Comment by John Glover:

Hi Genevieve,

Great post this week! I want to respond to both of your prompts.

I’ll start with a point you make on Question 1 first.

You say “…coastal salt marshes could be protected if there is an increase of root material build-up in marsh soils while continuing the trapping of sediment that is carried into the marsh during flood tides that humiliates at the same rate as the seawater rises but without this occurring there will be a continued to erosion of marsh soils, die-off of plants, and the loss habitat the marshes create for species that rely on them.”

This is an interesting point, because I do not think the current rate of sediment deposition would be enough to help stave off sea level rise. It would take massive amounts of soil to create rises of several feet along the coast. What do you think would be a possible solution to help increase sediment deposition without having negative environmental consequences?

Personally, I think we should focus on creating, restoring, or repairing habitat in the expected ranges of climate change. Cities like New York, New Orleans, and Miami could all benefit massively by creating wetlands along their costs to absorb some rising sea levels. Additionally, other coastal communities could “install” wetlands as a barrier to sea level rise if they are at or near expected sea level rise values.

For Question #2 I wanted to add something to your attempts to verify the source.

Nonpoint source pollution is difficult to trace, but not impossible. One strategy would be to test the tributaries of the wetland for pollution. This would help you identify which watershed the pollution originated in. Once you had a specific geographical area to investigate, you could then narrow down your list of culprits.

My Comment:

Hi Genevieve and John (Question 2),

John mentioned it is not entirely impossible to trace pollution from nonpoint sources (NPS). Further, while it is difficult to manage pollution from NPS, it is not impossible.

I found a study in which the authors introduced a methodological approach to the application of riparian buffer zones for mitigating pollution from NPS at coastal regions, reflected by river-based simulation (Kim et al. 2019). They used a simulation program for the watershed of Unmun Dam, Korea. It simulated the watershed hydrology with water quality for NPS contaminated runoff including the fate and transport of pollutants in stream channels (Kim et al. 2019). They applied a riparian buffer to the prepared watershed to estimate the reduction efficiency of pollution from NPS according to the size of buffer zone (Kim et al. 2019). Five scenarios (five different zone sizes of riparian buffer zones: 0.1 ha, 0.2 ha, 0.4 ha, 0.8ha, 1.6 ha) were investigated to determine the optimal zone size at the one site in the Unmun Dam Watershed (Kim et al. 2019). From there, the authors determined that the construction of more than 0.8 ha of riparian buffer in the watershed of Unmun Dam would be effective in reducing the NPS pollution (Kim et al. 2019).

Reference:

Kim, J., Lee, S., Baek, J., Shin, H., & Kwon, S. 2019. “Reasonable Selection of Riparian Buffer Zone for the Reduction of Non-Point Sources Pollution in Coastal Area”. Journal of Coastal Research. 256-260. Accessed July 11 2021. https://www.jstor.org/stable/26852517

Reply by Genevieve:

Mary,

That is an encouraging finding, here in Orange county they just put into operation a water filtration facility to process out PFAS. This is acritical about it. (Links to an external site.)

This will allow the county to cut back on the amount of water they need to import of the needs of the community and reopen many of the wells that had been closed in the last year.

Thank you for your response,

Genevieve