Wetlands

Wetland – “those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include swamps, marshes, bogs and similar areas.” --- EPA Clean Water Act enforcement definition

Wetlands Emergent macrophytes (vegetation)

effectively define wetlands.

Marsh = dominated by non-woody vegetation.

Swamp = dominated by trees. Aquatic Marginal Wetlands = emergent

macrophytes can grow around a body of surface water (lake, stream, ocean). – presence depends on substrate and water conditions (Can emergent macrophytes grow there?)

-Fringe wetlands – almost always wet

-Flood wetlands – seasonally or less frequently wet

Wetlands Mires = where emergent macrophytes can

grow BUT are not around an open body of water and are permanently waterlogged. –depend on groundwater and/or reliable runoff

-Fens – “fed” by groundwater and runoff; nutrient rich

-Bogs – “fed” runoff (above the water table); nutrient poor; mosses of the genus Sphagnum.

Lake to Fen to Bog

Sphagnum

Wetland Conditions Waterlogged soils

less/low/no oxygen (decomposition uses + low diffusion)

Usually low in Nitrate (N) because of effects of low oxygen on bacteria.

If organically rich, anaerobic bacteria create hydrogen sulphide (H2S).

If flooded and dried or f ringing and subject to water motion conditions usually have more oxygen and nitrate in the soil.

Cypress Knees

Carnivorous “Bog” Plants

Wetland Primary Production Primary production in some tropical

fringing marshes equals that in tropical rainforests.

Primary production in some polar fens and bogs is very low (equivalent to tundra).

Few organisms consume the emergent macrophytes directly (only some mammals), most energy in the system relies on detritus.

Many terrestrial and aquatic organisms depend upon wetlands as “visitors.”

Saltmarsh Food Web

Wetlands & Lakes

Wetland Human “Benefits” Riparian flood wetlands reduce flow

variation and intensity of flood events. (Katrina & New Orleans)

Ocean flood wetlands (salt marshes) reduce the effects of storm surge. (Katrina & New Orleans)

Serve as areas of groundwater infiltration. (Florida aquifers)

Fringing and flood wetlands remove sediments and nutrients from water flowing through them.

Wetlands: Human Impacts Development – Many drained and then built

upon or used for agriculture. Some have been removed for mosquito control.

Water diversion – Many wetlands have been eliminated because their water sources have been diverted for other use.

Sediment starvation – some salt marshes off New Orleans lost due to reduced sedimentation after Mississippi alteration.

Peat/Sphagnum mining – Many mires damaged or removed.

Whooping Cranes

Wetland Mitigation