Transcript Wetlands

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