Salt Marsh Ecosystems

What are the four salt marsh stresses?

1. Wave stress

2. Nutrient stress

3. Oxygen stress

4. Desiccation stress

Why are salt marshes impacted by waves simply? Why do salt marshes suffer from oxygen stress simply?

This is because they live in ocean environments. Since they are muddy environments, they deal with this and have to figure out how to get oxygen down into the roots

Why are salt marshes affected by desiccation stress simply?

This is because they are land plants that re-invaded the ocean so their internal salinities are lower than external salinities

What limits wave stress in the marsh? What part of the marsh is exposed to wave stress?

Shallow water and thick vegetation. Outer edge of marsh

What species in the salt marsh adapted to wave stress at the marsh edge? How?

Spartina alterniflora because they bind sediment with dense network of roots and rhizomes

What are roots? Rhizomes?

Roots are getting the nutrients while rhizomes are the reproductive structures

What is found at the marshes edge in terms of nutrients? Why?

Deposition of organic rich sediment at the edge. This is because muds and organic matter move around. At the edge we are slowing down the flow because of the dense networks of grasses so we deposit a lot of it here, which provides a source of nutrients

What is their a landward decrease in?

Nutrient availability (more nutrient stress)

Why is there low oxygen in salt marshes?

This is because they have lots of muddy, organic rich sediment. Muds have a lot of surface area to bind organic matter. When you break this matter down you use oxygen and need to replace it. But this is hard because muds have low permeability so it is hard to get new oxygen rich water in there.

How have salt marsh plants adapted to oxygen stress? What is this?

Through an aerenchyma which is a low resistance channel in the blades that provides an oxygen pathway to the roots

Why do salt marsh plants undergo desiccation stress?

This is because the water that these plants live in is salter than internal tissues, which leads to desiccation. Water will diffuse out and it is not replaced (instead only salt is coming back in).

What are two adaptations that salt marsh plants have came up with to fight desiccation stress?

1. Excrete salt through salt glands (concentrate salt and then excrete it)

2. Retain water through succulent leaves (tough and leathery) which limits water loss