Invasive Aquatic Species

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Invasive Aquatic Species

• Mark Sytsma
• Center for Lakes and Reservoirs
• Portland State University
• Western Horticulture Inspection Society
• 6-9 October 2008
• Portland, OR

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Introduction

• Invasive aquatic species can be especially
  problematic because
• Many species are easily confused with native or
  legally imported species,
• Common names are confusing and often misapplied,
• Many aquatic weeds reproduce vegetatively from
  small fragments,
• Hitchhikers can be very small and/or transported
  in planktonic lifestages,
• Once they become established they are often
  difficult or impossible to eradicate

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Aquatic Weed Impacts Submersed plant monocultures
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Emergent Weed Impacts Ecological Engineering
SAR 1 cm/yr in Willapa Bay (Sayce 1988)
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Aquatic Weeds to Watch For

• Submersed
• African elodea Lagarosiphon major
• Brazilian elodea Egeria densa
• Oxygen weed, Anacharis Egeria najas
• Hydrilla Hydrilla verticillata
• Eurasian watermilfoil Myriophyllum spicatum
• Twoleaf watermilfoil Myriophyllum heterophyllum
• Curly leaf pondweed Potamogeton crispus

• Emergent
• Parrotsfeather Myriophyllum aquaticum
• Yellow flag iris Iris pseudacorus
• Purple loosestrife Lythrum salicaria
• Common reed Phragmites australis
• Narrowleaf cattail Typha angustifolia
• Floating leaf
• Yellow floating heart Nymphoides peltata
• Water chestnut Trapa natans
• Water hyacinth Eichhornia crassipes
• Salvinia molesta

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SubmersedAquatic Weeds
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Lagarosiphon majorAfrican elodea, oxygen weed
Problematic aquatic weed in UK, NZ. Popular for
ponds and aquariums

• Identification
• stems brittle, branch every 10-12 nodes.
• leaves submersed greatly recurved stiff
  alternate, spiral along the stem to 16 mm (1
  in.) long by 2 mm (1/16 to 1/8 in.) wide leaves
  3-veined with visible midvein
• leaf margins minutely toothed at stem tips,
  leaves are very densely crowded

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Egeria densa Brazilian waterweed, Brazilian
elodea, South American waterweed, common
waterweed, anacharis, oxygen weed

• Identification
• leaves are small and strap-shaped, about one inch
  long and 1/4 inch wide.
• leaf margins have very fine saw teeth that
  require a magnifying lens to see. Leaves occur in
  whorls of three to six around the stem but
  typically 4.
• Distinct double nodes (8 leaves/whorl) about
  every 10 nodes

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Egeria najas oxygen weed, narrow leaf egeria

• Aquarist and fish farm favorite easy to care for
  and grows fast

• Identification
• leaves show a prominent seration to the leaf
  edge, narrower leaves and 5 leaves per whorl
• A distinctive feature of this plant is the sharp
  downward curve of each leaf
• Very easily confused with hydrilla

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Hydrilla verticillataWater thyme

• Leaves in whorls around the stem (generally five
  leaves per whorl).
• Serrations or small spines along the leaf edges
  and along midrib (plant feels rough)
• Monecious and dioecious biotypes - monecious in
  more cold tolerant

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Hydrilla verticillata

• Tubers and turions are distinguishing,
  macroscopic features

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Elodea canadensisE. nutallii

• Native species - ubiquitous
• Leaves in whorls around the stem (generally three
  leaves per whorl).

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Differentiating Common Species in the
Hydrocharitaceae
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Myriophyllum spicatum Eurasian Watermilfoil

• Feathery leaves divided into leaflets. 3 to 5
  leaves grow in a whorled pattern around the stem.
  
• When out of water, leaves lose their rigidity and
  collapse around the stem.
• Flower spikes with inconspicuous flowers

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Myriophyllum heterophyllumtwo-leaf watermilfoil
Native to mid-N. America

• Identification
• Leaves may exhibit two distinctly different
  forms.
• Submerged Leaves fine and numerously dissected,
  yielding a delicate, feather-like or "coontail"
  appearance. reddish or greenish brown in color.
• Emergent Leaves small, bright green, and oval in
  shape, with or without teeth along the edges, up
  to ¼" wide, borne in whorls on a stalk-like
  portion of the stem, rising 6"-8" above the
  water. Emergent growth is generally associated
  with mature stages and may not be evident until
  late summer.
• stem stout, simple or branching, 3mm-8mm in
  diameter, often tinged in red to 3' or longer.
  Rather stout, smooth, branched.
• flowers in green to reddish spikes raised above
  the water's surface

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Potamogeton crispus curly leaf pondweed

• Identification
• leaves are sessile, oblong, stiff, 1.6-3.9 in.
  (4-10 cm) long, 0.2-0.4 in. (5-10 mm) wide,
  translucent and have noticeably curly margins
  (resemble lasagna noodles).
• Leaves often a reddish color
• flowers are brown, inconspicuous and wind
  pollinated.
• Forms distinctive turions (compressed stem tips)

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EmergentAquatic Weeds
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Myriophyllum aquaticum parrotfeather milfoil,
Brazilian watermilfoil
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Iris pseudocorus yellow flag iris, water flag
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Lysimachia vulgarisGarden loosestrife
Lythrum salicaria Purple loosestrife
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Phragmites australis
www.invasiveplants.net/phragmites/morphology.htm
ssp. americanus
ssp. altissimus
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Typha angustifolia narrowleaf cattail
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Floating Leaf Aquatic Weeds
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Nymphoides peltata yellow floating heart, asaza,
entire marshwort, floating heart
ODA
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Trapa natansEuropean waterchestnut
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Eichhornia crassipesWater hyacinth
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Salvinia molesta
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Pond
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Hitchhikers

• Snails
• New Zealand Mudsnail Potamopyrgus antipodarum
• Bivalves
• Zebra/Quagga mussels Dreissena sp.

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Potamopyrgus antipodarum New Zealand mudsnail
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NZMS
Full grown shell, fairly elongate with 5-6
whorls, maximum length usually 5mm, occasionally
6 mm
Ranges from light to very dark brown and may be
encrusted with algae, etc.
Operculum only visible on live snails
Dextral opening to the right of the animal
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Dreissena sp. Zebra and Quagga mussels
The name derives from stripes on the shellbut
stripes not always present

• Freshwater
• Grow in dense clusters
• Attach to many surfaces with byssal threads

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Questions?Mark Sytsma503 725
3883sytsmam_at_pdx.edu