Microbes and Plants - Freshwater Ecology: Concepts and Environmental Applications - page 149

TABLE 8.5 Important Trees Associated with Wetlands in North America

Common name Scientific name Distribution

Black spruce Picea mariana Boreal wetlands

Tamarack Larix laricina Boreal wetlands

Red maple Acer rubrum Temperate wetlands

Northern white cedar Thuja occidentalis Northeast temperate North America

Atlantic white cedar Chamaecyparis thyoides Southeast United States

Cypress Taxodium spp. Southeast United States, deepwater swamps

Tupelo Nyssa aquatica Southeast United States, deepwater swamps

Cottonwood Populus spp. Riparian wetlands

Willow Salix spp. Riparian wetlands

Red mangrove Rhizophora spp. Brackish tropical waters

Black mangrove Avicennia spp. Brackish tropical waters

habitats. Of the angiosperms, the monocots are relatively more important
in aquatic habitats than they are in terrestrial habitats (Hutchinson, 1975).
Aquatic ecologists tend toward classifications of plants based on func-
tional roles and habitats (Fig. 8.12). The traditional categories include:
(i) floating unattached macrophytes (roots not attached to substratum),
(ii) floating attached plants (leaves floating at the surface, and roots an-
chored in the sediments), (iii) submersed plants (entire life cycle, except
flowering, under water; generally attached to sediment), and (iv) emergent
(growing in saturated soils up to a water depth of 1.5 m and producing
aerial leaves).
Distinguishing aquatic plants on the basis of morphology can be diffi-
cult because there is tremendous variation in morphology of plant struc-
tures within genera. Also, leaf size and shape can change appreciably in the
same species grown under different environmental conditions (Fig. 8.13) or
even in the same plant above and below water (Fig. 7.2).
A wide variety of plant groups have given rise to aquatic species; some
of the representative genera are listed in Table 8.4 and shown in Figs. 8.14
and 8.15. Trees associated with wetlands are important in defining wetland
types (Table 8.5). The genera of submersed plants tend to be confined to
aquatic habitats, but emergent genera also have many representatives in
terrestrial habitats (Hutchinson, 1975). The aquatic plants form a vital
part of the ecosystem, but some have become serious invaders or pests. An
example of this is invasion of North American wetlands by purple loose-
strife (Lythrum salicaria) (Sidebar 8.4).

SUMMARY

1. Viruses are common in natural waters and have important
consequences in terms of diseases of aquatic organisms and human
health.
2. Archaea are important in extreme habitats and for some types of
biogeochemical cycling, particularly the formation of methane.