Pond algae: why the populations fluctuate?

Stormwater Management Workshop, 3/25/13
Pond algae: why the
populations fluctuate?
Serge Thomas, Ph.D.
10501 FGCU Blvd. S., Fort Myers, FL 33965-6565
239-590-7148
sethomas@fgcu.edu

What are algae?

Differentiation by size:
Macro algae
Large algae not requiring a microscope to be seen.
Composed of different algal cells which have different
functions and shapes.
Example is Chara vulgaris (stonewort)

Differentiation by size:
Micro algae
Microscopic algae requiring a microscope to be
seen.
Can be living alone or associated with other algae
(=colonies).
Colonies can have various spatial configurations

Differentiation by size:
Micro algae
Microscopic algae requiring a microscope to be
seen.
Can be living alone or associated with other algae
(=colonies).
Colonies can have various spatial configurations
A few cells can be specialized

Differentiation by color:
Green:
Yellow-brown (Diatoms):
Red:
Blue green:
Eukaryotes
Prokaryotes

Differentiation by location:
Open water algae (limnetic or pelagic)=
phytoplankton
Bottom algae (attached): Periphyton
Can be attached on bottom or not. If not attached,
can be resuspended by water mixing.
Can be attached to macroalgae (Chara) or aquatic
plants to “steal” their nutrients.

Role of algae:
Photosynthesis (primary producers):
CO 2 + H 2O C(H 2O) + O 2
Fuel the food chain
Give or take oxygen
Carnivores III
Carnivores II
Carnivores I
Primary producers
Grazers

Role of algae:
Photosynthesis (primary producers):
CO 2 + H 2O C(H 2O) + O 2
Fuel the food chain
10%
10%
10%
10%
Carnivores III
Carnivores II
Carnivores I
Primary producers
Grazers

Role of algae:
Photosynthesis (primary producers):
CO 2 + H 2O C(H 2O) + O 2
Fuel the food chain (bottom up control)
10%
10%
10%
10%
Carnivores III
Carnivores II
Carnivores I
Primary producers
Grazers

What controls the algae?
Photosynthesis (primary producers):
CO 2 + H 2O C(H 2O) + O 2
Light - Temperature

What controls the algae?
Photosynthesis (primary producers):
CO 2 + H 2O C(H 2O) + O 2
Light - Temperature
Nutrients:
macro nutrients: Phosphorus, Nitrogen, CO 2
micro nutrients: Iron, copper …

What controls the algae?
Photosynthesis (primary producers):
CO 2 + H 2O C(H 2O) + O 2
Light - Temperature
Nutrients:
macro nutrients: Phosphorus, Nitrogen, CO 2
micro nutrients: Iron, potassium…
Competition among algae and w/ the aquatic
plants

What controls the algae?
Photosynthesis (primary producers):
CO 2 + H 2O C(H 2O) + O 2
Light - Temperature
Nutrients:
macro nutrients: Phosphorus, Nitrogen, CO 2
micro nutrients: Iron, potassium…
Competition among algae and w/ the aquatic
plants

The top of the food chain can control
algae: top-down control
10%
10%
10%
10%
Carnivores III
Carnivores II
Carnivores I
Primary producers
Grazers

Let’s consider a freshly excavated pond…
Low nutrients in water = no phytoplankton

Let’s consider a freshly excavated pond…
Low nutrients in water = no phytoplankton = clear water

Let’s consider a freshly excavated pond…
Low nutrients in water = no phytoplankton = clear water
Light reaches Lake bed

Let’s consider a freshly excavated pond…
Low nutrients in water = no phytoplankton = clear water
Light reaches Lake bed
Some nutrients in the lake bed

Let’s consider a freshly excavated pond…
Low nutrients in water = no phytoplankton = clear water
Light reaches Lake bed
Rooted
aquatic
vegetation
Some nutrients in the lake bed

Let’s consider a freshly excavated pond…
Low nutrients in water = no phytoplankton = clear water
Light reaches Lake bed
Rooted
aquatic
vegetation
Rooted aquatic vegetation
and attached algae
intercept the nutrients
before getting to the
water
Attached algae
Some nutrients in the lake bed

Let’s consider a freshly excavated pond…
Low nutrients in water = no phytoplankton = clear water
Light reaches Lake bed
Rooted
aquatic
vegetation
Rooted aquatic vegetation
and attached algae
intercept the nutrients
before getting to the
water
attached algae
Some nutrients in the lake bed

Most of everywhere in the world, such a low
nutrient pond should look like that:

Most of everywhere in the world, such a low
nutrient pond should look like that:

Most of everywhere in the world, such a low
nutrient pond should look like that:
NOT SO
IN SOUTH FLORIDA

Instead we are getting this:

Instead we are getting this:

Instead we are getting this:
WHY?

Did I hear nutrients?

Did I hear nutrients?
NO, with proper management
Practices, you still are getting this:
WHY?

Looks familiar?

Looks familiar?

Looks familiar?

The Everglades !

Why is the Everglades so unique?

Rooted
aquatic
vegetation
attached algae

Rooted
aquatic
vegetation
attached algae

Rooted
aquatic
vegetation
attached algae

Rooted
aquatic
vegetation
attached algae

The native plants and attached algae of the Everglades need:
Light
CO2
Warm temperature
BUT, paradoxically,
VERY little nutrients such as Nitrogen and Phosphate.
The system seems enriched but it actually is the most pristine
of the world.

The Key component are the attached algae (periphyton):
http://www.youtube.com/watch?v=a8nWCXbEBhc&feature=plcp
“Periphyton is a complex community of
microscopic organisms and especially
algae that are adapted to remove the tiny
bits of nutrients from the water.
These nutrients are then transferred from
the periphyton to the other inhabitants of
the Everglades which thrive out of
proportions.
In addition to being the foundation of the
Everglades, periphyton creates ideal
conditions that promotes limestone
making.
This limestone slowly builds up over time,
thus creating new land in a similar fashion
to the coral building reefs. “

The Key component are the attached algae (periphyton):
http://floridacoastaleverglades.blogspot.com/2012/07/scum-isnt-always-bad.html

The Key component are the attached algae (periphyton):
The good periphyton:
- Is the base of the food chain
- Provides with most oxygen in the water column
- Arbors beneficial bacteria and invertebrates
- Disappears when the temperature is low (but especially grows during the rainy
season)
- Does not release much nutrients when it decays
- Does not create odors when it decays likely because of its high calcium carbonate
(chalk) content.
- When it decomposes, it creates a “slab” of limestone which isolates the lake bed. This
is mostly inorganic calcium carbonate or chalk (low sediment built up).
- Can lock phosphorus as it dries up. Limestone is a trap for phosphorus.
- Can remove nitrogen through denitrifying bacteria

Why the floating mats? (After all, we would be happy if they would
not float)

Why the floating mats? (After all, we would be happy if they would
not float)
Periphyton grows as a thin layer first.
As periphyton gains in thickness, oxygen bubbles issued from the photosynthesis process
get trapped
Because the mat grows thick, the basal periphyton no longer receives light and dies
The periphyton is no longer attached and it floats on the surface.
Eventually, it gets exported to open water or sink back to the bottom if the photosynthesis
stops (periphyton dies, or if light is not present e.g. night).

Why the floating mats? (After all, we would be happy if they would
not float)
Periphyton can also grow on submerged unrooted plants such as the low nutrient
adapted Utricularia purpurea .
When the pond has a little bit more nutrients, the periphyton will grow on Chara
vulgaris and unroot it.

How do I control the good periphyton and its associated plants?
As long as you can cope with an Everglades looking pond, there is normally no
management required: you are saving $$ and you are doing something good for the
environment.
- the periphyton will grow on the shallow shelf of the pond
- the periphyton will stay confined within the vegetation growing on the shelf.
- the periphyton will not grow in the deepest part of the pond UNLESS, the
pond is too shallow.
If too shallow, the pond can be covered with floating mats.
MAYBE dyes can be used with parsimony in that
situation. The dye concentration must be adjusted so that the
periphyton and the plants growing on the shelf remain unaffected.

How does the good periphyton can give place to the bad and worst,
the ugly phytoplankton (scum forming) blooms?
The good periphyton was wrongly identified and killed with chemicals. Its mass
decomposition released nutrients to the water
and/or
Nutrients loading coming from the surrounding lawns renders the low nutrient
adapted good periphyton incapable of competing with the bad periphyton

The scenario when the good periphyton is killed, and
nutrient loading increases.
Light reaches Lake bed
Rooted
aquatic
vegetation
X
X
periphyton
Some nutrients in the lake bed
Nutrients

The scenario when the good periphyton is killed, and
nutrient loading increases.
Light reaches Lake bed
Rooted
aquatic
vegetation
BAD periphyton
Some nutrients in the lake bed
Nutrients

The scenario when the good periphyton is killed, and
nutrient loading increases.
The bad periphyton is very different than the good one:
- It does not have any calcium carbonate and thus
- It does not lock phosphorus
- It does not create limestone
- When it decays, it releases a lot of nutrients and it can generate odors
- It does not arbor as many good bacteria and invertebrates
- Its decomposition process uses a lot of oxygen
- When it decays, it fills the pond with black very organic muck, which
releases nutrients

The nutrient loading and the release of nutrients from
the bad periphyton generate phytoplankton: The water
clarity decreases gradually.
Rooted
aquatic
vegetation
BAD periphyton
phytoplankton
Nutrients

The nutrient loading and the release of nutrients from
the bad periphyton generate phytoplankton: The water
clarity decreases gradually.
Rooted
aquatic
vegetation
phytoplankton
Nutrients

The nutrient loading and the release of nutrients from
the bad periphyton generate phytoplankton: The water
clarity decreases gradually.
Rooted
aquatic
vegetation
phytoplankton
Nutrients

The nutrient loading and the release of nutrients from
the bad periphyton generate phytoplankton: The water
clarity decreases gradually.
phytoplankton
Nutrients

The nutrient loading and the release of nutrients from
the bad periphyton generate phytoplankton: The water
clarity decreases gradually.
diffusion
nutrients
phytoplankton
Nutrients

The pond is nutrient enriched, phytoplankton blooms
and wind resuspension keep the pond turbid. No
periphtyon, no aquatic plants, just phytoplankton
RESUSPENSION
diffusion
nutrients
phytoplankton
Nutrients

The pond is nutrient enriched, phytoplankton blooms
and wind resuspension keep the pond turbid. No
periphtyon, no aquatic plants, just phytoplankton
RESUSPENSION
diffusion
nutrients
phytoplankton
Nutrients

What if we keep the phytoplankton in check with
chemicals?
RESUSPENSION
diffusion
nutrients
phytoplankton
Nutrients

What if we keep the phytoplankton in check with
chemicals?
Light reaches Lake bed
RESUSPENSION
diffusion
nutrients
Nutrients

What if we keep the phytoplankton in check with
chemicals? Bad periphyton eventually grows or
phytoplankton come back (unless chemicals are added
at all times)
Light reaches Lake bed
RESUSPENSION
BAD periphyton
diffusion
nutrients
Nutrients

What if we keep the phytoplankton in check with
chemicals? Bad periphyton eventually grows or
phytoplankton come back (unless chemicals are added
at all times)
RESUSPENSION
diffusion
nutrients
phytoplankton
Nutrients

Each time a treatment is done, algae (or plants) are killed and
this adds to the muck layer thus releasing more nutrients in the
pond, consuming oxygen and reducing the volume of water that
could dilute the nutrient concentration (less buffering capacity).
RESUSPENSION
diffusion
nutrients
phytoplankton
Nutrients

Filamentous green algae
(the bad)

Pithophora: horsehair algae
Coarse alga, feels like cotton when water is squeezed out. Made of numerous
branching filaments. Yellowish to pale green.

Cladophora: Blanket weed
Green filamentous branching alga.
Feels a bit rough and sometimes a bit gritty.

Filamentous blue green algae
Some bad, some very ugly

Microcystis aeruginosa (43%), scum forming

Microcystis aeruginosa (43%)
Toxin: microcystin (hepatotoxic). 1ug/L is the threshold.
Can remain in post treated water
High persistence, high water solubility, high chemical
stability
http://en.citizendium.org

Cylindrospermopsis raciborskii (40%), suspended in water
Toxin name: cylindrospermopsin
Can cause liver damage and even death in humans (water supply)
Potentially carcinogenic in humans
Creates skin reactions by contact
Fish kill, cattle death, affects snails.
Toxin bioaccumulates in molluscs, crayfish.

Anabaena (29%), scum forming
Toxin: Microcystin, Anatoxin-a (nerve damage)
Saxitoxin (nerve’s axons)

Planktothrix (Oscillatoria) (14%), scum forming
Toxin: Microcystin, Anatoxin-a (nerve damage),
Aplysiatoxin (skin)
http://www.epa.ohio.gov/

Aphanizomenon flos-aquae (7%), scum forming
Toxin: Cylindrospermopsin, saxitoxin (nerve’s axon)

Coelosphaerium (4%), scum forming
Toxin: Microcystin

Lyngbya (1%), scum forming
Dark green or nearly black thick mats .Musty or foul odor.
Toxin: Lygbyatoxin-A, debromoaplysiatoxin, saxitoxin (nerve’s axon)
Severe dermatis in swimmers

Spirogyra, floating mat forming
Feels like silk,
bright green and slimy to the touch
Toxin: not known to produce toxins

What to do with the bad and ugly stages?
1. If funds were reserved for dredging. Dredge the pond
and reset it. A pond normally is designed to be
dredged every 25++ years
- Often, the sediment contains heavy metals and
copper at higher levels than what is set for the dispose
of residential soil. This adds up to the cost of dredging.

Sediment accumulation

Sediment accumulation

Sediment accumulation

Nutrients accumulation

Nutrients accumulation

Arsenic accumulation

Copper accumulation

What to do with the bad and ugly stages?
2. Slow down the sedimentation rate by preventing algal
growth
- Adding chemicals
- Raking out algae mats, but inefficient for
phytoplankton
- Adding aerators
- Use dyes
- Use bacteria/enzymes
- Wetland filtration
- Floating islands
- Phoslock and Alum treatment
- ultrasounds
NOTE: Most of these above solutions are against the good functioning of a detention
pond: Detain pollutants through bio uptake (beside the straight sedimentation).

What to do with the bad and ugly stages?
2. Slow down the sedimentation rate by preventing algal
growth
- Adding chemicals
Several chemical are available. All must be handled
properly as they could be a hazard for the wildlife.
Ohio State University has a brochure which
explains how to use these chemicals:
- Copper sulfate (but watch for Copper
accumulation in the sediment and the pollution
to Naples bay)
- Copper Chelate
- Diquat Dibromide
- Endothall amine salts
www.ohioline.osu.edu/a-fact/pdf/A_3_09.pdf

What to do with the bad and ugly stages?
2. Slow down the sedimentation rate by preventing algal
growth
- Adding chemicals
Sodium Carbanate Peroxhydrate seems to be a
better and safer alternative to Copper.
www.ohioline.osu.edu/a-fact/pdf/A_3_09.pdf

What to do with the bad and ugly stages?
2. Slow down the sedimentation rate by preventing algal
growth
- Raking out algae mats, but inefficient for
phytoplankton
It is labor intensive, but it does remove algae and
their associated nutrients.
It does not work for phytoplankton

What to do with the bad and ugly stages?
2. Slow down the sedimentation rate by preventing algal
growth
- Adding aerators
Relatively costly but if done correctly, positive results can be
expected:
- oxygen supply will
- limit Fish kill
- limit odors such as H 2S (rotten egg)
- allow organic matter degradation
(the contrary of photosynthesis)
C(H 2O) + O 2 CO 2 + H 2O
- allow phosphorus lock by the iron in
the sediment
- mixing will have the algae travel up and down the
water column, thus limiting a steady light access.

What to do with the bad and ugly stages?
2. Slow down the sedimentation rate by preventing algal
growth
- Use dyes
Dyes will not work if the pond is too shallow (less
than two feet) or if most of the pond has shallow
shelves (normally a 1/3 of the surface area)
Dyes will block some of the useful wavelengths
available for photosynthesis.
Dyes also kill submersed aquatic plants.

What to do with the bad and ugly stages?
2. Slow down the sedimentation rate by preventing algal
growth
- Use bacteria/enzymes
A hot topic right now. Need more evidence that it
works.
It seems that a LOT need to be added to hope for a
positive result.
The bacteria and enzymes are there: there is just a
need to get the environment right to have them
grow and compete with algae with nutrients while
reducing the muck layer.
Should be used in conjunction with aerators.

What to do with the bad and ugly stages?
2. Slow down the sedimentation rate by preventing algal
growth
- Wetland filtration
Wetlands are the kidneys of ecosystems. When
well managed, a wetland can filter water and
sequester phosphorus while promoting
denitrification and particulate filtration.
Using pond water to water the lawns is, to some
extent, doing wetland filtration. However, be sure
that your water is right before doing so.

What to do with the bad and ugly stages?
2. Slow down the sedimentation rate by preventing algal
growth
- Floating islands
Floating islands or gardens seem to draw positive
results despite their size.
My graduate student is trying to figure this paradox
out.
Floating island replace the use of wetlands and
their maintenance is actually not that prohibitive.

What to do with the bad and ugly stages?
2. Slow down the sedimentation rate by preventing algal
growth
- Floating islands

What to do with the bad and ugly stages?
2. Slow down the sedimentation rate by preventing algal
growth
- Floating islands

What to do with the bad and ugly stages?
2. Slow down the sedimentation rate by preventing algal
growth
- Phoslock and Alum treatment
Alum treatment and phoslock are supposed to lock
the phosphate so that it is permanently
sequestered.
Alum has more research background than
phoslock.
Alum seems to give mixed results especially over
the long term.

What to do with the bad and ugly stages?
2. Slow down the sedimentation rate by preventing algal
growth
- Ultrasounds
Ultrasound destroy the membranes of algae. Some
research is currently ongoing.

REMEMBER!
Detention ponds are designed to detain nutrients and
other pollutants. If you kill the vegetation and the algae,
the free nutrients will pollute the bay.
Chemicals used to treat the pond eventually make their
way to the Bay (e.g. Copper), with drastic consequences
on the natural ecosystems
Ponds are supposed to be dredged. They are a sediment
trap on top of being a biofilter.

REMEMBER!
The chicken and the egg:
Detention ponds are often the reason of your
residential development.

Thanks to :
- Naples botanical garden and Kapnik Center
- UF (IFAS) and Doug Caldwell for inviting me
- Chad Washburn from the garden
- FIU periphyton lab and other anonymous for the pictures
- AND ULTIMATELY, YOU GUYS FOR YOUR ATTENTION