Cyanobacteria Blooms:

1
Cyanobacteria Blooms Effects on Aquatic
Communities
Karl E. Havens University of Florida /
IFAS Department of Fisheries and Aquatic Sciences
March 2007 US-China Harmful Cyanobacteria Workshop
2
Recent Microcystis blooms in the USA
Lake Okeechobee, FL (Summer 2005)
St. Johns River, FL (Summer 2005)
What impacts do these event have on the aquatic
biota?
3
EVENT
DIRECT EFFECT
POTENTIAL IMPACT

• Light limitation plants, epiphyton, benthic
  algae, phytoplankton

Reduced Transparency

• Sub-lethal and lethal impacts
• to fish populations

Elevated pH
BLOOM FORMATION

• Altered competitive interactions
• among phytoplankton

Reduced CO2

• Impacts on zooplankton grazing and food web
  efficiency

Increased Algal Size

• Allelopathy, sub-lethal and lethal toxic
  effects on fish, zooplankton,
  macro-invertebrates, wading birds, other aquatic
  vertebrates

Toxin Production
Hypoxia / Anoxia
BLOOM COLLAPSE

• Fish kills, sub-lethal and lethal impacts on
  other biota

Ammonia
4
Community Impacts - 1 Plants and Alternative
States
5
Stabilizing processes
Alternative
States
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Community Impacts - 2 Plankton Food Webs
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Effects on grazing zooplankton

• Mechanical interference
• Toxic effects
• P limitation at high CP ratios

Results in

• Reduced growth rates
• Reduced fecundity
• Reduced longevity
• Increased mortality
• Large Daphnia most sensitive
• Food web effects

8
Size
Zooplankton
Phytoplankton
Nutrients
9
Gliwicz, Z.M. 1969. Studies on the feeding of
pelagic zooplankton in lakes with varying
trophy. Ekologia Polska 17 663-708.
10
Hillbricht-Ilkowska, A. 1977. Trophic relations
and energy flow in pelagic plankton. Polish
Ecological Studies 3 3-98.
11
Lake Okeechobee (from Work, Havens and East 2005,
J. Plankton Res.)
During an Anabaena circinalis bloom
With small Lyngbya limnetica dominance
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Lake Okeechobee response of plankton food web
(ugC/L) to NP after 6-day incubation with
Cylindrospermopsis dominance
13
Lake Okeechobee response of plankton food web
(ugC/L) to NP after 6-day incubation with diatom
and small Lyngbya dominance
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Community Impacts - 3 Benthic Communities
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Potentially Impacted by CHAB
Palmer, M.A., A.P. Covich, S. Lake et al. 2000.
Linkages between aquatic sediment biota And life
above sediments as potential drivers of
biodiversity and ecological processes. BioScience
50 1062-1075.
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Community Impacts - 4 Direct and Indirect
Effects of Toxins
17
Some Documented Effects of Cyanobacterial Toxins

• Suppression of zooplankton grazing (Gilbert 1990)
• Allelopathy on other phytoplankton (Suikkanen et
  al. 2004)
• Hepatotoxic effects on fish (Ernst et al. 2001)
• Renal failure in fish (Kotak et al. 1996)
• Inhibition of fish gill Na/K-ATPase activity
  (Bury et al. 1998)
• Accumulation in copepod body tissues and fecal
  pellets and potential for accumulation in higher
  trophic levels in plankton and benthos
  (Lehtiniemi et al. 2002)
• Accumulation in crayfish tissues and potential
  for transfer to higher trophic levels (Liras et
  al. 1998)
• Mass mortality of ducks reported during a
  Microcystis bloom in Japan (Matsunaga et al. 1999)

Most results from controlled lab experiments
and toxic effects occurred at high doses of toxins
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Common Themes

• Use of purified microcystin LR in many studies
  little work with other congeners of MS or other
  toxins
• Single species experiments with ideal conditions
  are the norm little work with natural stressors
• Lack of consideration of behavioral or
  physiological modulation
• Lack of consideration of effects of simultaneous
  or sequential exposure to different toxins
• Greater biotic response to crude cell lysates
  than pure toxins not well understood, but other
  cell components suspected (e.g., LPS, capsule)
• Few studies at community level
• Insufficient information about biomagnification
  although results to date suggest it does not
  occur for MS

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Synthesis / Information Gaps
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HAB
Toxins
Other Effects
Individual and Population Effects Effects of
chronic vs. acute and episodic exposures Exposure
with other stressors (low DO, NH4,
etc.) Effects on physiology, pathology,
genotoxicity, behavior, reproduction
Cyanotoxin Exposure Single vs. multiple or
sequential toxin exposures Presence of other
bioactive compounds
Community and Ecosystem Responses Dependent on
direct and indirect effects of toxins Dependent
on the many other impacts of blooms