Underwater Video as a Method for Detecting and Quantifying Rare Individuals

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Underwater Video as a Method for Detecting and
Quantifying Rare Individuals

• Applied to Zebra/Quagga Mussels (Dreissena spp.)
  and Burrowing Mayflies (Hexagenia spp.)
• in Lake Erie

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This presentation was funded by the Ohio Sea
Grant College ProgramProject No. R/ER-66-PD

• Kenneth A. Krieger, Heidelberg College
• Matthew A. Thomas, F.T. Stone Laboratory, The
  Ohio State Univ.
• Natalie J. Johnson, Heidelberg College
• Michael T. Bur, US Geological Survey

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Acknowledgements

• The Ohio Sea Grant College Program and Franz
  Theodore Stone Laboratory
• Ryan Allen Information Technology, Heidelberg
  College
• The Ohio Lake Erie Commission, Lake Erie
  Protection Fund (Project SG 232-04)

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Project Hardware and Software

• Research Vessels R/V Erie Monitor (OSU),
  R/V Bowfin (USGS)
• Remotely Operated Vehicle Phantom XTL
• ROV monitor and video system Deep Ocean
  Engineering OSD-379
• Analog video digitization and editing
  Roxio Easy Media Creator 7
• This Presentation Microsoft PowerPoint

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Captain Al Duff and student Natalie Johnson about
to launch Stone Labs remotely operated vehicle
(ROV) from the stern of the R/V Gibraltar III,
summer 2003
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Ponar Grab for soft sediments In photo Don
Schloesser, USGS
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Introduction

• Grab samplers have historically been used to
  sample soft lake sediments to estimate the
  distribution and abundance of benthic
  macroinvertebrates.

• When the macroinvertebrates of special interest,
  such as burrowing mayflies, are rare, their
  presence may not be detected by grab samplers
  because they typically sample an area lt0.05 m2.
• By surveying a much greater area, video imaging
  promises to be much more effective at detecting
  and quantifying rare individuals that provide
  visible signs of their presence.

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Lake Erie
Study Area
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5B
6K
6.35K
6.30K
6.265K
67K
BRD16D
7K
BRD16C
BRD16B
LV67
1CP
BRD15N
2CP
Lorain
Sandusky
Huron
Stations where sediment was sampled in 2003 and
2004 for burrowing mayflies and zebra/quagga
mussels.
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Major members of the benthic invertebrate
community of soft sediments in well-oxygenated
bottom waters of Lake Eries western and central
basins include

• Zebra and Quagga Mussels
• Burrowing Mayflies
• Midges

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Zebra Quagga MusselsDreissenidae Dreissena
polymorpha D. bugensis
Photos Dave Barton
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Hexagenia spp. burrowing mayflies
male
female
male adult
nymphs
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Chironomidae midges
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Dreissenid mussels (Dreissena bugensis and D.
polymorpha) reside at the sediment surface . . .
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Zebra/quagga mussels on the bottom of Lake Erie
Live dreissenids
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Video with a brown tint like this was
photographed using the ROV lights.
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Video with a green tint like this was
photographed using natural light reaching the
lake bottom.
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In this video of soft sediment on the bottom of
Lake Erie, note the slightly open shells of the
live dreissenid mussels as they are filtering
food from the lake water.
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Unlike dreissenid mussels, the larvae of
burrowing mayflies (Hexagenia spp.) and midges
(fly Family Chironomidae) live within burrows in
soft sediment.
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Still shot
Hexagenia burrow holes

• Holes in top of grab sample w quarter for scale

View of sediment surface inside an Ekman grab.
Note the well-oxygenated brown sediment overlying
the gray reduced sediments.
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Grab samplers and video might be similarly
effective at quantifying the numbers, and perhaps
even the size distributions, of mussels and
burrowing mayfly nymphs where they are common,
such as seen in this video of dreissenids near
the east end of Middle Bass Island.
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In the next video, note the clumps (druses) of
live dreissenid mussels, then many Hexagenia
burrow holes in the sediment near the Bass
Islands.
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Video of mussels and burrows
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Hexagenia burrows are usually U-shaped and thus
have two holes, though some have three or more.
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• The following video gives a close-up look at a
  mayfly burrow hole. Notice the high resolution
  of the ROV camera. The horizontal distance
  between the two red laser points is 6 cm.

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Burrow hole
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As one travels from the edge of the western basin
into the eastern basin, the abundance of
Hexagenia nymphs and dreissenid mussels declines
sharply.

• In the next video (poor quality), the ROV passes
  over ridges of sand and valleys of silt and
  shells, all devoid of live mussels and mayflies.
  

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Ridges and valleys
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• In this video, the ROV moves along a sand ridge
  that forms part of a series of ripples in the
  sediment at 46 feet (14 m) in the central basin.

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• Small holes may be the openings of midge tubes
  rather than of Hexagenia burrows.

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On the next video, watch the red midge larva
retreat into its tube. Visibility is
relatively poor because of material resuspended
off the bottom.
midge
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Midge video
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Small bits of debris may appear to be midge or
mayfly burrow holes until viewed at close range
a potential drawback to the use of video for
surveying small individuals.
See this example.
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Video of specks
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Underwater video can also be useful for finding
other uncommon animals that are too sparsely
populated to be sampled adequately with a grab.

• Here are a couple of examples, both from Station
  67K at a depth of 45 feet (14 m) in the central
  basin.

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A snail and its trackBrown patches of diatoms
are visible here at a depth of 45 feet.
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Snail and track video
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A string of fish eggs
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Fish egg video
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The final photos show the method of selecting an
area of video image within which to quantify
burrow holes.To be accurate, the lasers must be
kept at the same position in the image, i.e.,
camera angle must be constant.
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2
400 cm
6 cm
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Numerous Hexagenia burrow holes, generally two
per burrow (natural light)
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For more information on burrowing mayflies in
Lake Erie . . .

• Visit
• www.heidelberg.edu/wql/research-activities.html

For information zebra and quagga mussels and
other Great Lakes research covering many topics .
. .
Visit www.sg.ohio-state.edu