Littoral zone -- from high water area to area with no attached
plants; interface between land and water; highly productive
I. Aquatic Macrophytes -- almost all were originally land
plants
and are secondarily aquatic.
There are also some ferns, mosses, liverworts and
large algae.
NOTE: You only need to remember
(recognize) genus names in bold
(not others)
A. Importance of macrophytes
1. Structurally important
a. Define the littoral zone
b. Often considered nuisances
c. Slow currents and increase sedimentation
d. Habitat for invertebrates and fish
e. Increased species diversity
2. Functionally important
a. Very productive
b. Pump of nutrients from the sediments to the water
c. High rates of evapotranspiration may decrease lake water levels
d. Most of carbon fixed by macrophytes goes to the detrital/microbial
food
web
B. Ecological types of macrophytes – biodiversity
of macrophytes
1. Rooted in sediment
a. Rooted submersed
(1) (Type 1) Long stems and compound leaves. Flexible.
a) Potamogeton -- pond weed;
~80 species in a variety of habitats; variable size and shape; wildlife
food
b) Myriophyllum -- water milfoil
(M. spicatum – Eurasian water milfoil is exotic; native is M.
sibiricum)
c) Najas -- bushy pond weed;
d) Elodea -- water weed (has invaded Europe from N.
America)
e) Chara -- green algae, stoneworts, ‘musk
grass’;
precipitate calcium carbonate
reproduction -- sporangia
f) Nitella -- green algae; acidic and dilute waters
(2) (Type 2) -- plants with stiff leaves in a close rosette or on
short,
rigid unbranched stems
a) Ranunculus (in part) -- water crowfoot
buttercup family; lodewort; rams foot; sometimes fed to animals
b) Elatine -- waterwort
c) Isoetes -- quillwort; club moss; often in oligotrophic lakes
or deep in water
d) Eriocaulon – pipewort, hatpins;
e) Vallisneria - wild celery; tape grass; eel grass
b.
Rooted
floating (Type 3) - leaves mostly or entirely floating on the
surface;
lots of wind stress
a) Nymphaea -- water lily; nearly circular in shape;
notched
to the center
b) Brasenia – watershield; oval and shield shaped leaves.
Stalk attached at center of leaf blades;
undersides covered with viscous jelly-like substance
c) Nuphar -- yellow water lily; spatterdock; cow lily –
heart-shaped
leaves
d) Potamogeton
again, pondweeds most totally submersed; some have floating leaves
e) Trapa -- "water
chestnut"; exotic pest in Central N.Y.
c.
Rooted
emergent – (Type 4) more supportive material, plenty of sunlight;
very
productive, but often a low species diversity
a) Scirpus – bulrush
b) Juncus – rushes
c) Pontederia – pickerelweed
d) Typha – cattail
e) Eleocharis – spikerush
~150 spp.; Some are cultivated as human food; some are major food
for birds and other animals
f) Sagittaria – arrowhead; edible rhizomes
g) Carex – sedge; heavily used by wildlife
h) Equisetum -- horsetail/scouring-rush horsetail; consumed by
wildlife
2. Unrooted – (can not
get
nutrients from sediments)
a. Unrooted submersed
a) Ceratophyllum -- underwater flowers and mobile
pollen;
leaves are in whorls on the stem – ‘raccoon’s tail’
b) Utricularia -- bladderwort; carnivorous
b.
Unrooted
floating (Type 5 – entire plant floating)
a) Eichornia – water hyacinth; exotic pest in S. U.S.,
S.
America and Africa;
clogs waterways; increases rate of evaporation of water; not many
things
eat it;
floats into littoral zone and decomposes -- decreases oxygen, hurts
fish
breeding zones;
can block off light penetration
b) Lemna – duckweed
c) Spirodela - largest of the duckweeds
d) Salvinia - water fern; in waters with high organic content;
has
root-like structures that are actually modified fronds
e) Pistia - water lettuce
C. Zonation of macrophytes
1. Physical --
a. Temperature
b. Light
c. Pressure -- affects gas transport; limits distribution
d. Wind and waves
e. Substrate -- rocks and sand are difficult, do better in soft and
organic
sediments
2. Biological (not as
well
studied)
a. competition -- light, nutrients, space
b. herbivory -- not as important compared to grazing on terrestrial
plants
or in the pelagic; << 25% of aboveground biomass
D. Adaptations of macrophytes -- how they deal
with
mostly physical limitations
1. Water is buoyant --
reduced
amount of supportive tissue
2. Reduced light
a. leaves only a few cells thick
b. leaves are finely divided -- more surface area per volume
3. CO2
availability
-- diffusion slower than in air
a. assimilation of HCO3-
b. lacunae
c. finely divided leaves
d. heterophylly -- plasticity of shape of plant -- leaves are
more
finely divided as get lower –
CO2 concentrations or temperature
4. Nutrient availability
a. most uptake through roots
b. increased leaf length increases turbulent flow; then can take up
nutrients
through leaves as well.
5. Many can reproduce
vegetatively
-- turions (winter buds) or rhizome sprouting
6. Produce secondary defense
compounds to inhibit algae, epiphytes, and grazers
II. Filamentous algae
- concentrated in the littoral zone
- must grow in shallow water where there is adequate
light, but can go deeper than macrophytes (no lacunae; extra
photosynthetic pigments)
- no roots, no leaves
- nutrients from sediments
- can cause problems/nuisances in small ponds
- often are chlorophytes (green algae; e.g. Spirogyra,
Cladophora)
or cyanobacteria
III. Periphyton – algae (and associated microbes) that live attached
to other objects,
including
macrophytes
- Aufwuchs -- plants and animals that live
attached to something
- can't be moved out of euphotic zone easily
- macrophytes are leaky and release nutrients
through
stems and leaves; algae take up nutrients from macrophytes
- If periphyton gets dense it will shade the
macrophytes
-- macrophytes keep growing to try to avoid shading
Wetlands (intermittently to permanently flooded regions)
I. Peat forming (accumulate partially decayed plant matter;
‘mires’)
A. Bogs --
o sphagnum-moss dominated
communities
o only water source is
rainwater
(ombrotrophic)
o low in nutrients
o low in primary production
o form acidic peats (lack
of decomposition allows peat to build up)
o support acidophilic
vegetation
B. Fens
o Receives nutrients from
sources other than precipitation, usually from groundwater
o may range from acidic
to non acidic
o can have grasses, sedges,
or reeds
o peat can develop due to
lack of decomposition in acidic areas, or to high production in
non-acidic
areas
II. Non peat forming
- swamps -- mineral
soils rather than peat; ground permanently or seasonally submerged;
vegetation dominated by trees or shrubs (in US common usage)
- marshes –
frequently
or continually wet areas with herbaceous vegetation adapted to
saturated
soil conditions
- wet meadows –
grasslands
with water-logged soil near the surface, but without standing water for
most of the year
Wetland and Littoral Management
I. Wetland destruction
· ~1/2 of all wetlands lost in the contiguous
U.S. since 1780
· agricultural drainage; health reasons
· loss of birds, mammals and fish
II. Wetland restoration
· resemblance to the original?
· Peatlands
III. During eutrophication littoral plants are often outcompeted by
phytoplankton (shading)
IV. Macrophyte control
· Mechanical harvesting
· Herbicides
· Biocontrol – grass carp; insects
Interested in
wetlands/macrophytes and wetlands? Two
good recent sources are:
Mitsch, W.J. and J.G. Gosselink. 2000. Wetlands. 3rd edition. John Wiley
& Sons, Inc. 920 pp.
Naiman, R.J., H. Décamps, and M.E.
McClain. 2005.
Riparia: Ecology, Conservation and Management of Streamside Communities Elsevier Academic Press. 430 pp.