Transcript Chesapeake Bay Grasses

Chesapeake Bay Grasses
Introduction
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Wild Celery
Southern Naiad
Red-Head Grass
Water Stargrass
Widgeon Grass
Common Waterweed
Eelgrass
Salinity and the
Chesapeake Bay
• Submerged aquatic
vegetation has
specific salinity
requirements,
although some have a
wide salinity tolerance
range.
Terms and
Salinity levels
Euryhaline vs. Stenohaline
• “eury” means wide
• Organisms that are adapted to
tolerate a wide variety of
salinities.
• Euryhaline organisms are
commonly found in habitats
such as estuaries and tide
pools where the salinity
changes regularly.
• Some organisms are
euryhaline because their life
cycle involves migration
between freshwater and
marine environments, as is the
case with striped bass and
eels.
• “steno” mean narrow
• Organisms that can only
survive within a narrow range
of salinities.
• Most freshwater organisms are
stenohaline, and will die in
seawater, and similarly most
marine organisms are
stenohaline, and cannot live in
fresh water.
• Includes crayfish, most species
of trout, and darters
Plant Anatomy
Rhizome – mass of roots
Turion - specialised overwintering bud
produced by aquatic herbs
Monocot – single cotyledon
seed
Dicot – two seed halves
Wild Celery
(Vallisneria americana Micheux)
• This perennial monocot has long
slender leaves with a light green
stripe down the center of the leaf.
• It is found throughout the Bay in
fresh water but can tolerate salinities
of up to 12-15 ppt.
• Wild celery stabilizes shorelines and
tolerates wave
• action better than most SAV.
• It spreads vegetatively through
turions, rhizomes,and seeds (male
flowers produce pollen that when
released at surface, fertilize the
female flowers).
• The plants are excellent food for
waterfowl and provide habitat for fish
and invertebrates. Vallisneria has
been used to monitor pollution in
rivers.
Southern Naiad
(Najas guadalupensis (Spreng) Magnus)
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Submerged annual monocots form
dense mats of vegetation.
Small flowers and fruits are almost
entirely hidden at the leaf bases.
Leaves are dark green to greenish
purple, opposite or in whorls of
three.
Naiads grow primarily in
freshwater streams, and
freshwater to brackish tidal Bay
tributaries.
Southern naiad reproduces by
seeds and fragmentation.
Fragments can be seen floating at
the water’s surface.
Pollination takes place
underwater.
Naiad vegetation and seeds are
consumed by waterfowl and in
some cases are second only to
wild rice as a food source.
Redhead Grass
(Potamogeton perfoliatus L.)
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Redhead grass is a perennial SAV
commonly found in fresh to
brackish water of up to 20ppt
salinity.
It produces winter buds that allow
it to establish itself vegetatively,
while pollination occurs as spikes
of tiny flowers emerge from leaf
axils on ends of plant stems.
Flower spikes extend above the
water surface and the pollen is
carried by wind.
As fruits mature they sink below
the surface where they release
seeds.
This SAV is an excellent food
source for waterfowl.
Water Stargrass
(Heteranthera dubia (Jacq.) MacMillan)
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A perennial monocot with dark
green leaves with small starshaped yellow flowers that float or
rise above the water surface.
The plants grow in large, tangled
rooted masses.
Found in quiet bodies of water
with salinities of up to 5 ppt.
The plants spread both
vegetatively through the roots, and
through seed.
Flowers that do not reach the
water’s surface remain closed and
self-pollinate.
The leaves are eaten by ducks
and other waterfowl, and the
plants provide habit for fish and
invertebrates.
Common Waterweed
(Elodea canadensis Micheaux)
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Perennial monocot with branching
stems; narrow leaves in whorls of
3 at stem nodes, with whorls
closer together at tips of plant.
Elodea is found in fresh to
brackish slow-moving or calciumrich waters; their salinity tolerance
is not well documented.
Male flowers rise on long stalks
and split open, spreading pollen
onto the water's surface where it
drifts to fertilize female flowers.
Ducks, beaver and muskrat
consume this plant.
Widgeon Grass
(Ruppia maritime)
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Linear, thread-like leaves are 3 to 10 cm (1 ¼ in to 4
in) long and 0.5 mm (<1/32 in) wide; these are
arranged alternately along slender, branching stems.
Leaves have a basal sheath and a rounded tip.
Widgeon grass has an extensive root system of
branched, creeping rhizomes that lack tubers.
Tolerates a wide range of salinity, from the slightly
brackish upper and mid-Bay tributaries to near
seawater salinity in the lower Bay, has also been
reported to grow in the freshwater parts of some
estuaries.
Can also be found growing in ditches alongside
roads and agricultural fields where it derives its other
common name, ditch grass
In more saline lower Bay areas, widgeon grass and
eelgrass are the dominant bay grass species.
Widgeon grass is most common in shallow areas
with sandy substrates, although it occasionally grows
on soft, muddy sediments.
High wave action can damage the slender stems and
leaves of widgeon grass.
It is also one of the more valuable waterfowl food
sources and all parts of the plant have nutritional
value
Eelgrass
(Zostera marina)
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Zostera marina is found on sandy
substrates or in estuaries submerged or
partially floating.
Most Zostera are perennial. They have
long, bright green, ribbon-like leaves, about
1 cm wide. Short stems grow up from
extensive, white branching rhizomes.
The flowers are enclosed in the sheaths of
the leaf bases, the fruits are bladdery and
can float.
Zostera beds are important for sediment
deposition, substrate stabilization, as
substrate for epiphytic algae and microinvertebrates, and as nursery grounds for
many species of economically important
fish and shellfish.
Zostera often forms beds in bay mud in the
estuarine setting.
It is an important food for Brant Geese and
Wigeons, and even (occasionally)
caterpillars of the grass moth Dolicharthria
punctalis.