Plants and the Littoral Zone

Ecology and Diversity

Growth Habits and Locations of Plant Types in the Littoral Zone

Emergent Macrophytes

• Rooted in the substrate• Leaves fully exposed to air• Usually rhizomatous• Stems and leaves usually with aerenchyma or

lacunae• Nutrient uptake from the sediment and

inorganic carbon from the air

Examples of emergent macrophytes

• Typha: commonly called cattail, is very characteristic of wetland communities. Typha is a monocot related to grasses.

Examples of emergent macrophytes

• Glyceria: mannagrass, is an aquatic grass with leaves that are very rough to the touch

Examples of emergent macrophytes

• Phragmites: called common reed, is a grass that grows aggressively in aquatic and semi-aquatic environments

Examples of emergent macrophytes

• Zizania: wild rice, is related to the grass, Oryza, true rice

Examples of emergent macrophytes

• Eleocharis: spikerush (more appropriately spikesedge), is a grass-like plant in the sedge family. The genus is similar to a diminuitive Scirpus in that it makes spike-like stems without leaves.

Examples of emergent macrophytes

• Scirpus: commonly called bulrushes, are in the sedge family. They are rhizomatous with hollow stems. Leaves are associated with the inflorescence, which is subapical.

Examples of emergent macrophytes

• Carex: the dominant genus of sedges (>1500 species). These grass-like plants have stems that are triangular in x-section.

Examples of emergent macrophytes

• Juncus: rush, superficially resembles Eleocharis. However, it forms a tuft of spike-like stems that grow from a basal rosette of leaves.

Examples of emergent macrophytes• Polygonum: smartweed or

knotweed, is recognized by having swollen nodes and has many species, but only a few are aquatic. The native species is frequently found associated with the margins of lakes, ponds, reservoirs, and in backwater areas of rivers and creeks. Japanese Knotweed, an invasive from Asia, also is found associated with wet areas, but rarely in the water.

Examples of emergent macrophytes

• Equisetum: horsetail. The common one found in water is E. fluviatile, the river horsetail. These plants are related to ferns.

Floating-leaved rooted macrophytes

• Generally rhizomatous• Floating leaves with cuticle on upper surface• Petiole usually very long• Nutrient uptake from the sediments and

inorganic carbon often from both the water and air

Floating-leaved macrophytes, rooted

• Nuphar: spatterdock or cow lily, is rhizomatous with large floating leaves. All stems and roots are in the mud. The plant is common to aquatic systems throughout the northern hemisphere.

Floating-leaved macrophytes, rooted

• Nymphaea: waterlily is very similar to Nuphar but it has a large showy flower, which makes it a favorite of water gardens.

Floating-leaved macrophytes, rooted

• Brasenia: watershield is similar to Nuphar, but smaller. The stems, though technically rhizomatous, emerge from the substrate.

Floating-leaved macrophytes, rooted

• Nelumbo, lotus, resembles Nymphaea. However, some of its leaves are emergent. One species is native to North America.

Floating-leaved macrophytes, rooted

• Potamogeton: pondweed is rooted with elongate stems and floating leaves.

Unrooted floating-leaved macrophytes

• Many have gas-filled floats or tissue• Some have leaves that are entirely aerial • All have a hanging root system (or modified

tissues that operate as roots), thus nutrient uptake entirely from water but inorganic carbon from the air

• Stems are highly reduced

Floating-leaved macrophytes, not rooted

• Lemna: duck weed, a common floating plant throughout the northern hemisphere.

Floating-leaved macrophytes, not rooted

• Wolffia, water meal, is the world’s smallest flowering plant. Often, it is found together with Lemna.

Floating-leaved macrophytes, not rooted

• Eichhornia, water hyacinth is a large free-floating plant from South America that has become a noxious weed of waterways in the southern US.

Floating-leaved macrophytes, not rooted

• Pistia, water lettuce, was first found in Egypt near the Nile. Now it has been dispersed by humans to nearly all tropical and subtropical waterways. It has become a pest in the US on some waterways.

Free-floating unrooted macrophytes

• Plants are almost entirely submerged, but may float at the surface

• In general, the leaves are highly-dissected• Fragmentation a major form of reproduction

and dispersal• Roots rare; thus, nutrient uptake entirely from

water

Free-floating macrophytes, not rooted

• Utricularia: bladderwort, is an aquatic carnivorous plant. There are more than 250 species and the genus has global distribution. Some species have become pests in some regions.

Free-floating macrophytes, not rooted

• Ceratophyllum, hornwort or coontail, is global in distribution and usually found in hard water ponds and lakes.

Submerged rooted aquatic plants

• In general, the leaves are highly dissected• Nutrient uptake both from water and

sediment

Submerged rooted macrophytes

• Myriophyllum, water milfoil, is native to Eurasia and has become a pest in many relatively still bodies of water.

Submerged rooted macrophytes• Elodea: waterweed is

submerged and native to North America. It can root in sluggish streams. They can be very abundant in nutrient-rich lakes and ponds. Used globally as an aquarium plant.

Submerged rooted macrophytes• Vallisneria: water

celery or tape grass, is a rooted plant with broad leaves that is frequently found in local creeks.

Submerged rooted macrophytes• Isoetes, quillwort is

a fern ally with corm-like bases to the leaves. An indicator of acid-sensitive water. Sometimes they are emergent.

Submerged rooted macrophytes

• Chara, muskgrass or skunkweed, is a non-vascular plant. Many of the species have a fetid odor. This genus usually is found in hard water ponds and lakes.

Submerged rooted macrophytes

• Nitella, stoneworts or brittleworts, are related to Chara but may occur in soft water ponds and lakes. They do not deposit calcium carbonate in their cell walls as many Chara species do, and therefore, are soft to the touch.

Zonation in Ozera Nero

• From the shore to the lake center– Salix– Phragmites– Typha– Scirpus– Equisetum– Potamogeton– Nuphar– Lemna (in all

emergent plants)– Ceratophyllum

Sam Rayburn Reservoir

• Marginal macrophytes make tight concentric bands of:– Nitella– Potamogeton– Elodea

Main Stem of the Susquehanna River

• Beds of macrophytes in backwater areas and in the clear water of the West Branch– Vallisneria– Polygonum– Glyceria

Impacts of macrophyte dominance

• High primary production• Decreased turbulence• More efficient (than algae) nutrient uptake

and sequestration??• Increased water clarity• High organic load

Heterophylly• Many aquatic plant species

show differences in leaf shape when in or out of the water.

Reproduction, dispersal, and dormancy

• Asexual: e.g. Potamogeton– Winter buds– Agamospermy

• Vegetative: e.g. Myriophyllum• Sexual: – Insect pollination e.g. Nuphar– Wind pollination e.g. Typha– Water pollination e.g. Potamogeton and Elodea

Movement of gases

• Diffusion-dependent throughflow convections.

• e.g. Fig 18-2

Movement of gases

• Nonthroughflow• Venturi-induced throughflow• Methane to atmosphere very high for

emergent and floating-leaved rooted plants.• Oxygen transport in submerged macrophytes• Lacunae in roots and rhizomes may promote

an oxidizing area around the roots which protects from H2S

Carbon uptake

• CO2 diffusion much slower in water than air• No cuticle in submerged leaves• Chloroplasts in epidermis• Many can decarboxylate bicarbonate• Often high release of CO2 from sediments in

areas with macrophytes• Can recirculate CO2 within plant via lacunae

CAM Metabolism

• Found in certain aquatic plants and certain desert plants.

• Allows for CO2 uptake at night when inorganic carbon highest in water.

CAM photosynthesis

Keeley, J.E. 1985. The role of CAM in the carbon economy of the submerged-aquatic Isoetes howellii. Verh. Internat. Verein. Limnol. 22: 2909-2911.

Phosphate and nitrate enrichment relative to biomass

Plants and Water Velocity

Relationship between pH and alkalinity

RIVERS RESERVIORS LAKES

Littoral zone/wetland

Land-water interface well developed

Land-water interface poorly developed

Land-water interface well developed

Macrophyte community structure

With emergent, floating, and submerged macrophytes

Wetland macrophytes in riverine portion, limited submerged plants, floating plants dominant

Well-developed emergent, floating, and submerged macrophytes

Nutrient acquisition Mainly through roots Mainly through roots Most from sediments

Light acquisition Limited by canopy in low order streams and by turbidity and algae in high order streams

Limited to shallow areas due to turbidity

Mostly unrestricted except for submerged macrophytes

Macrophyte biomass and production

High in floodplain; low in low order streams, highest in mid-order streams and low in high order streams

Low to moderate, mainly in riverine wetlands; floating-leaved macrophytes can be very productive

High to very high, mainly with emergent macrophytes