1. Nuisance
Algae
on
the
Southeast
Shore
of
Lake
Huron
David
Barton,
Department
of
Biology,
University
of
Waterloo
Todd
Howell,
Environmental
Monitoring
and
ReporEng
Branch,
Ontario
Ministry
of
the
Environment
Cherie-‐Lee
Fietsch,
Bruce
Power
3. QuesEons:
What
is
it?
How
does
it
get
on
the
beach?
Where
does
it
come
from?
Why
is
there
so
much
of
it?
4. Chara fouling
- Occurs periodically from April - November
- Fouling areas widely distributed and varied over time
- Beached algae dries out yielding coarse debris
- Has become a recurrent feature in recent years
- No history of shore fouling before ~2000
4
7. “periphyton” is a complex mixed coating of filamentous algae
(including Cladophora) and diatoms that grows on rocks
periphyton
muck
accumulated
on
the
shoreline
8. Where
does
the
algae
come
from?
Underwater
surveys,
1977,
2007,
2010
• Underwater
photos
taken
in
1977
by
Dr.
Norman
Rukavina
during
studies
of
nearshore
geological
features
• Underwater
video
survey
in
2007
• fine-‐scale
survey
in
2010
9. 1977
2007
15
m
depth
off
Amberly
Beach
Most
of
the
substratum
in
the
area
is
rocky
out
to
depths
>20m.
Almost
no
algae
were
visible
in
1977;
nearly
all
of
the
bo[om
was
covered
in
2007.
10. Periphyton is much more abundant than in the recent past
Eighteen Mile River: 2007 (~20m depth) Baie du Dore: 2007 (~20m depth)
40km
Eighteen Mile River: 1977 (~20m depth) Baie du Dore : 1977 (~20m depth)
1977 Photo Credit:
N.A.Rukavina
Environment Canada
11. Chara
was
found
only
near
Point
Clark
at
depths
<4m
There
was
a
strong
correlaEon
between
filamentous
algae
(Cladophora
and
other
periphyton)
and
mussels,
especially
near
Inverhuron
12. Chara
and
rooted
plants
were
largely
restricted
to
shallow
water.
The
percentage
of
the
bo[om
covered
by
periphyton
and
filamentous
algae
increased
with
increasing
depth
to
about
15m.
Mussels
were
most
abundant
at
depths
>10m.
14. Shoreline fouling was monitored
weekly from May through mid-
August 2010, at 14 sites.
Stranded material was identified and
quantified on each visit.
Wind and wave records from NOAA
buoy (Station 45008).
15. Figure 3. Total estimated amounts of algae (Chara, Cladophora and periphyton)
stranded at the study sites during summer 2010.
Abundances
of
Chara
and
Cladophora
were
greatest
near
areas
of
greatest
growth.
Periphyton
accumulated
around
shoreline
features.
16. Total estimated amounts of algae (Chara, Cladophora, periphyton) stranded at all study
sites on each sampling visit during summer 2010.
Intervals
between
peaks
of
Chara
and
Cladophora
probably
reflect
the
Eme
needed
for
growth
17. Waves
>1m
high,
especially
if
prolonged,
put
more
Chara
on
the
beach.
Cladophora
appears
to
be
easily
dislodged
when
filaments
are
long
enough.
Most
periphyton
was
stranded
during
a
single
2-‐day
event.
18. Why
has
the
amount
of
algae
increased?
Hypotheses:
- increased nutrient inputs (e.g. agriculture, cottage septic systems?)
- low lake level
- benthic enrichment by Dreissena (“the nearshore shunt”, Hecky et al. 2004)
- reduced numbers of grazing benthic invertebrates
19. Nutrients: Onshore-offshore Gradients and Alongshore Gradients
Point Clark Study Area conductivity as a tracer
August 10, 2010 of land-based inputs to
the shoreline and
nearshore mixing
elevated conductivity
along the shoreline
> correspond with areas of
locally stimulated growth
of Cladophora
kriged surface based on
field measurements from
waterline to 5 km offshore
20. Areas of Phosphorus Enrichment Along the Immediate Shoreline
conductivity
footprint
Point Clark Area
of the
shoreline
filtered TP elevated in
vicinity of multiple shore
discharge points
Conductivity map with
numeric values of
filtered TP overlain
21. Point Clark – red circle
Inverhuron – blue circle Nearshore Phosphorus Spring 2010
TP
TP levels below lake objective of 5 µg L-1
over most of the nearshore
Ambient TP (lake depth >3 m) in spring
Filtered TP 2010 :
2.7 µg L-1 at Point Clark
2.2 µg L-1 at Inverhuron
Sharp gradients from shoreline to open
lake
SRP Locally enriched P along the shoreline
suggested threshold of 2 µg L-1 SRP for
stimulation of Cladophora growth exceeded
at points along the Point Clark shoreline
22. Nutrient enrichment at the mouth of creeks
stimulates localized growth of Cladophora
2006
Numeric Values: Cladophora
Total
Phosphorus
(ug/L)
23. Intensive
sampling
near
sources
of
SRP
confirmed
that
Cladophora
is
responsive
to
local
inputs.
24. Chara Distribution at the Shoreline
Measurements of percent cover and
height from shoreline to ~1m depth
High surface coverage in some
locations; sparse to absent at other
No clear association with proximity to
drain
discharge points
Maximum bed height 6 - 7 cm
25. Benthic Survey to Quantify Algae, Invertebrates
and Round Gobies on the Lakebed, August 2010
• Quantifying the amounts of bottom-dwelling algae,
grazers and fish is impossible from the surface
• Professional divers were hired to collect samples
using specialized techniques developed through
research
25
26. Inverhuron
Point Clark
Inverhuron
Point
Clark
Methods
3 transects centered at both Point Clark and Inverhuron were sampled by
divers during July 2010
Airlift fitted with 200 µm aperture mesh collecting bag was used to collect 3
samples of invertebrates from 15x15cm quadrats at depths of 1, 3, 6, 10 and
20m
Benthic algae were sampled concurrently
Relative abundances of Round Goby were ranked from Absent (0) to Very
Abundant (4)
27. Chara
was
found
only
once
at
depths
>3m
DensiEes
of
mussels
were
very
low
28. Cladophora
was
usually
associated
with
dreissenid
mussels,
oben
growing
as
clumps
on
mussels
But,
the
total
mass
of
algae
was
not
correlated
with
density
of
mussels,
so,
nutrient
cycling
by
mussels
does
not
appear
to
influence
local
algal
abundance
29. The
density
of
Cladophora
was
low
where
numbers
of
invertebrates
were
high:
Grazing
by
invertebrates
may
reduce
abundance
of
Cladophora:
31. Very
few
historical
data
for
comparison:
QualitaEve
airlib
collecEons
from
depths
1-‐2m
at
Point
Clark,
July
1974
and
July
2004
(Barton
2004)
2
transects
brackeEng
Point
Clark
were
sampled
by
Ministry
of
Environment
in
late
September
1980,
at
depths
of
5,
10
and
20m
(Barton
&
Griffiths
1984)
(quanEtaEve
airlib)
32. RelaEve
abundances
of
larger
potenEal
grazers
(snails
and
insects)
were
lower
in
2010
than
in
1974.
34. Round
gobies
were
common
to
abundant
at
nearly
all
sampling
sites
in
2007
-‐
2010
Round
gobies
are
a[racted
to,
and
prefer
to
eat,
insects
and
amphipods,
but…
35. Round
gobies
also
eat
mussels
that
are
large
enough
to
bite
(>2mm)
and
small
enough
to
swallow
(<13
-‐
15
mm)
36. Low Water Level in Recent Years May Benefit Chara
Water Level
May to August
Goderich Surface area of lakebed from 1 to 3m depth has
likely increased over the Point Clark study area since 2000
- 32% increase comparing 1997 with 2010
contours ( 4.20 vs 6.18 km2 over study shoreline)
lines are at
chart datum
data used in calculation:
- 1m bathymetry contours
- mapping of shoreline in 2010
- water level at Goderich
37. What
is
it,
and
how
does
it
get
on
the
beach?
Beach
fouling
is
caused
by
Chara,
Cladophora
and
“periphyton”
Chara
and
Cladophora
grow
most
luxuriantly
in
shallow
water
(>3m
deep)
low
lake
level
may
have
increased
the
amount
of
potenEal
habitat
“periphyton”
occurs
on
all
rocky
surfaces,
becoming
more
abundant
as
depth
increases
to
ca.
15m
Beach
stranding
of
Chara
and
periphyton
seems
to
require
waves
at
least
1m
high
Large
stranding
events
are
most
likely
to
occur
only
aber
periods
of
calm
weather
38. Why
is
there
so
much
algae?
ConcentraEons
of
phosphorus
are
high
only
immediately
along
the
shore
Cladophora
density
is
correlated
with
higher
phosphorus
concentraEons
Chara
showed
no
clear
response
to
nutrient
inputs
Periphyton
biomass
was
greatest
further
offshore
where
nutrient
concentraEons
are
very
low
DensiEes
of
zebra
and
quagga
mussels
were
very
low,
generally
<300
m-‐2
in
2010,
and
showed
no
relaEonship
with
algal
standing
stocks
39. .
Weak
inverse
relaEonships
between
densiEes
of
invertebrates
and
a[ached
algae
suggest
grazing
pressure
might
be
important.
The
relaEve
abundances
and
densiEes
of
grazing
invertebrates
appear
to
have
declined
since
the
1970’s,
probably
because
of
predaEon
from
round
gobies
