Original Post by John Glover:

There are two major factors oxidizing sediments in a Mangrove swamp. One is an animal and one is not. What are they and how do they change the chemistry of the sediment?

The two major factors that oxidize sediments in a Mangrove swamp are crabs and tides and storms. Crabs play a major role in oxidizing sediments by burrowing in the sediment of mangrove swamps. The crabs will eat decomposing plant material and some mangrove seedlings, and in doing so have to burrow through sediments. Their movement allows oxygen to enter the soil. By allowing oxygen to enter the system, crabs also play a vital role in flushing out sulfide and ammonium that can build up in mangrove soils over time from natural bacterial activity (Mitsch and Gosselink, 2015).

Tides and storms also oxygenate Mangrove swamp sediment through physical force. The disturbance of soil from tides and storms allows oxygen to permeate deeper into the sediment. Large storms, hurricanes in particular, can generate a significant amount of disturbance that can aerate soil. The salt water entering the system also reduces competition for mangrove trees, which are much more salt tolerant than other vegetation (Mitsch and Gosselink, 2015).

How do mangrove swamps function as nurseries? How would destruction of mangrove environments affect other ecosystems?

Mangrove swamps create a unique physical coastal environment with a thriving ecosystem. The network of deep roots and prop roots that extend into the water create a unique habitat where fish have cover to hide in. This creates an ideal nursery habitat for developing marine fish. Because fish must go through a larval and juvenile phase before they reach their full development, they are very vulnerable in the open ocean as young. Being able to hide in the network of roots reduces predation. Furthermore, there is an extensive supply of food in the mangrove swamp. The food chain begins in the detrital peat in the swamps. Fungi, bacteria and protozoa break down decomposing material to generate energy. These organisms are then fed on by phytoplankton and benthic algae. The food chain continues with small invertebrates and eventually the developing fish.

The destruction of mangrove swamps is already having a significant impact on marine fisheries. Some studies estimate more than over 50 percent of the world’s mangroves have disappeared. Furthermore, half of the remaining mangrove forests are considered to be in poor condition (AMNH, n.d.). Without safe nurseries to develop in, future marine fisheries stocks will be severely threatened. Entire fisheries could collapse if they are not replaced successfully by younger generations. This is a massive human crisis because roughly 3 billion people worldwide rely on seafood as their primary source of protein (WWF, n.d.).

Why are freshwater marshes used to clean up water and effluent from corporate pig farm operations in the USA?

Animal agriculture operations like pig farms have high rates of nitrogen and phosphorus runoff into streams and rivers due to the manure (EPA, n.d.). Runoff from agricultural operations is becoming a serious issue in the United States, particularly in the Mississippi River Basin. Excess runoff from farms has created a growing dead zone in the Gulf of Mexico. This zone is hypoxic because of toxic red algae that feed on the excess nitrogen and phosphorus (Union of Concerned Scientists, 2020). Freshwater marshes can serve as a crucial management tool because of their ability to remove excess nutrients from water that enters their system.

Therefore, planting freshwater marshes to clean water running off from animal agriculture operations can help remove excess nutrients before they enter water systems like rivers and streams. Freshwater marshes have high rates of productivity, and as the plants grow they remove nitrogen and phosphorus from the water and soil. Marshes can also slow the rate that water enters rivers and streams as runoff. The water will remain in marshes as standing water for an extended period of time, allowing more nutrients to be pulled from the water. When marshes become oversaturated with nutrients, however, they can leak nutrients out if overwhelmed (Mitsch and Gosselink, 2015).

Reference List:

American Museum of Natural History (AMNH). “Mangrove Threats and Solutions.” https://www.amnh.org/explore/videos/biodiversity/mangroves-the-roots-of-the-sea/mangrove-threats-and-solutions (Links to an external site.)

Environmental Protection Agency (EPA). N.d. “Estimated Animal Agriculture Nitrogen and Phosphorus from Manure..” https://www.epa.gov/nutrient-policy-data/estimated-animal-agriculture-nitrogen-and-phosphorus-manure (Links to an external site.)

Mitsch, William J., and James G. Gosselink. 2015. Wetlands. John Wiley & Sons, Inc.

Union of Concerned Scientists. 2020. “Nitrogen Washing Off Midwest Farms Cause Billion in Annual Damage to Gulf of Mexico Fisheries and Marine Habitat, Study Finds.” https://www.ucsusa.org/about/news/nitrogen-farms-cause-24-billion-gulf-dead-zone-damage (Links to an external site.)

World Wildlife Fund (WWF). N.d. “Sustainable Seafood.” (Links to an external site.)https://www.worldwildlife.org/industries/sustainable-seafood

My Comment:

Hi John (responding to the powerpoint project),

I found it so useful to see the context of your wetland in terms of surrounding location. Great job showing where the wetlands are relative to the rest of the park. That trail map of the Rocky Mountain Arsenal helped put the remainder of the presentation into perspective. It is also fascinating to see the acre distribution broken down by habitat type. Great job defining the various wetland types, as well. 15,000 acres is a gigantic Refuge considering its close proximity to Denver. It is interesting to place that next to the 674 ares of wetland in the Refuge. In general, listing the total amount of species types helps illustrate its diversity and adds value to its restoration. Specifically, the 275 species of bird is remarkable! Identifying the species of concern helps advocate for diligent wetland management under the Endangered Species Act. Also phenomenal point about wetlands providing a rare, great habitat for aquatic reptiles in the dry state of Colorado. I also appreciate the way that you defined the tree types partly by their water-tolerance. Then, going into how specific herbaceous obligate wetland plants respond to drought tied the whole project together.