Biology at SCC
Freshwater Ecology & Watershed Research

Cyanobacteria · Chapter 7

Bloom Prevention and Biological Control

Outline · full text in Phase 2 Last reviewed 2026-11-05

Learning objectives

After studying this chapter, you should be able to:

  1. Explain why reducing nutrient inputs is the foundation of bloom prevention.
  2. Evaluate in-lake measures (mixing, algaecides, hydrogen peroxide) and their limits.
  3. Describe biomanipulation and the conditions under which it succeeds or fails.
  4. Distinguish contained laboratory research with modified organisms from environmental release, and outline ecological risk assessment.
This chapter is an outline The introduction, planned sections, key terms and references below are reviewed and citable. Full textbook text for each section will be added in Phase 2.

The most reliable way to prevent blooms is to reduce the nutrients that fuel them, which means working in the watershed — on fields, pastures, wastewater and stormwater — and accepting that results may take years, especially where phosphorus is stored in lake sediments [1, 2]. In-lake measures can buy time or protect a specific use, but each has limits. A review of interventions in Dutch lakes found that many marketed approaches — air-bubble screens, surface mixers, low-energy ultrasound, "effective micro-organisms" and fish introductions — had little or no effect, while others worked under particular conditions [3, 4]. Artificial mixing helps mainly in deep systems [5]; algaecides kill cells but release toxins and do not address causes [6]; and a carefully staged whole-lake trial showed that dilute hydrogen peroxide can selectively suppress cyanobacteria for a time [7].

Biological approaches seek to strengthen grazing. Biomanipulation — removing plankton-eating fish so that large grazers increase — can improve clarity, but long-term success usually requires nutrient reduction as well [8, 9]. The discovery that grazers can evolve tolerance and that gut microbiomes influence it raises research questions about coevolution and biological control [10, 11, 12]. Genetic engineering of grazers or microbes is sometimes proposed. It is an emerging research possibility, not an established environmental treatment: experiments in contained laboratories are very different from deliberate environmental release, which would require case-by-case ecological risk assessment and regulatory review [13, 14].

Planned sections

7.1 Nutrient management

Source reduction for nitrogen and phosphorus; why dual reductions matter in many systems [1, 15]; Kentucky's Nutrient Reduction Strategy [16].

7.2 Watershed restoration and riparian buffers

Buffers, wetlands, livestock exclusion and stream restoration; time lags, especially in karst [17].

7.3 Aeration and mixing

When mixing works and when it fails [5, 4].

7.4 Algaecides and their limitations

Copper, peroxide and other compounds; toxin release; non-target effects [6, 7].

7.5 Biomanipulation

Food-web manipulation and its track record [8, 9].

7.6 Zooplankton grazing and coevolution

Grazer–cyanobacteria arms races and local adaptation [10, 18, 12].

7.7 Microbiome-associated tolerance

Evidence from gut microbiota transplants in Daphnia [11].

7.8 Experimental biotechnology and risk

Genetic modification and gene drives as research ideas; contained use versus release; risk assessment of unintended effects and regulatory considerations [13, 14].

Connection to local research

At Allen Branch and nearby waters

Bloom control is not a local need at Allen Branch, where no bloom has been observed. The relevant local work is upstream of any problem: understanding nutrient sources and connectivity, and — in the laboratory only — studying grazer tolerance with non-toxic cultures.

Related: biological-control mechanisms (laboratory only).

Key terms

Biomanipulation
Changing a food web to reduce algae.
Algaecide
Chemical used to kill algae or cyanobacteria.
Riparian buffer
Vegetated strip along a stream that slows runoff.
Contained use
Laboratory work designed to prevent release of organisms.
Ecological risk assessment
Structured evaluation of possible harms before an action.

References

  1. Paerl, H. W., Scott, J. T., McCarthy, M. J., Newell, S. E., Gardner, W. S., Havens, K. E., Hoffman, D. K., et al. (2016). It Takes Two to Tango: When and Where Dual Nutrient (N & P) Reductions Are Needed to Protect Lakes and Downstream Ecosystems. Environmental Science & Technology, 50(20), 10805-10813. https://doi.org/10.1021/acs.est.6b02575
  2. Søndergaard, M., Jensen, J. P., & Jeppesen, E. (2003). Role of sediment and internal loading of phosphorus in shallow lakes. Hydrobiologia, 506-509(1-3), 135-145. https://doi.org/10.1023/b:hydr.0000008611.12704.dd
  3. Lürling, M., & Mucci, M. (2020). Mitigating eutrophication nuisance: in-lake measures are becoming inevitable in eutrophic waters in the Netherlands. Hydrobiologia, 847(21), 4447-4467. https://doi.org/10.1007/s10750-020-04297-9
  4. Lürling, M., Waajen, G., & de Senerpont Domis, L. N. (2016). Evaluation of several end-of-pipe measures proposed to control cyanobacteria. Aquatic Ecology, 50(3), 499-519. https://doi.org/10.1007/s10452-015-9563-y
  5. Visser, P. M., Ibelings, B. W., Bormans, M., & Huisman, J. (2016). Artificial mixing to control cyanobacterial blooms: a review. Aquatic Ecology, 50(3), 423-441. https://doi.org/10.1007/s10452-015-9537-0
  6. Jančula, D., & Maršálek, B. (2011). Critical review of actually available chemical compounds for prevention and management of cyanobacterial blooms. Chemosphere, 85(9), 1415-1422. https://doi.org/10.1016/j.chemosphere.2011.08.036
  7. Matthijs, H. C. P., Visser, P. M., Reeze, B., Meeuse, J., Slot, P. C., Wijn, G., Talens, R., et al. (2012). Selective suppression of harmful cyanobacteria in an entire lake with hydrogen peroxide. Water Research, 46(5), 1460-1472. https://doi.org/10.1016/j.watres.2011.11.016
  8. Shapiro, J., & Wright, D. I. (1984). Lake restoration by biomanipulation: Round Lake, Minnesota, the first two years. Freshwater Biology, 14(4), 371-383. https://doi.org/10.1111/j.1365-2427.1984.tb00161.x
  9. Jeppesen, E., Søndergaard, M., Lauridsen, T. L., Davidson, T. A., Liu, Z., Mazzeo, N., Trochine, C., et al. (2012). Biomanipulation as a Restoration Tool to Combat Eutrophication. In Advances in Ecological Research (pp. 411-488). Elsevier. https://doi.org/10.1016/b978-0-12-398315-2.00006-5
  10. Hairston, N. G., Lampert, W., Cáceres, C. E., Holtmeier, C. L., Weider, L. J., Gaedke, U., Fischer, J. M., et al. (1999). Rapid evolution revealed by dormant eggs. Nature, 401(6752), 446-446. https://doi.org/10.1038/46731
  11. Macke, E., Callens, M., De Meester, L., & Decaestecker, E. (2017). Host-genotype dependent gut microbiota drives zooplankton tolerance to toxic cyanobacteria. Nature Communications, 8(1), 1608. https://doi.org/10.1038/s41467-017-01714-x
  12. Ger, K. A., Urrutia-Cordero, P., Frost, P. C., Hansson, L.-A., Sarnelle, O., Wilson, A. E., & Lürling, M. (2016). The interaction between cyanobacteria and zooplankton in a more eutrophic world. Harmful Algae, 54, 128-144. https://doi.org/10.1016/j.hal.2015.12.005
  13. Snow, A. A., Andow, D. A., Gepts, P., Hallerman, E. M., Power, A., Tiedje, J. M., & Wolfenbarger, L. L. (2005). Genetically engineered organisms and the environment: current status and recommendations. Ecological Applications, 15(2), 377-404. https://doi.org/10.1890/04-0539
  14. National Academies of Sciences, E. (2016). Gene Drives on the Horizon. National Academies Press. https://doi.org/10.17226/23405
  15. Conley, D. J., Paerl, H. W., Howarth, R. W., Boesch, D. F., Seitzinger, S. P., Havens, K. E., Lancelot, C., et al. (2009). Controlling Eutrophication: Nitrogen and Phosphorus. Science, 323(5917), 1014-1015. https://doi.org/10.1126/science.1167755
  16. Kentucky Energy and Environment Cabinet (2022). Kentucky's Nutrient Reduction Strategy, a step forward in improving water quality. Naturally Connected (Cabinet news). https://kydep.wordpress.com/2022/10/10/kentuckys-nutrient-reduction-strategy-a-step-forward-in-improving-water-quality/ (accessed 2026-11-05)
  17. Currens, J. (2002). Changes in groundwater quality in a conduit-flow-dominated karst aquifer, following BMP implementation. Environmental Geology, 42(5), 525-531. https://doi.org/10.1007/s00254-001-0515-6
  18. Sarnelle, O., & Wilson, A. E. (2005). Local adaptation of Daphnia pulicaria to toxic cyanobacteria. Limnology and Oceanography, 50(5), 1565-1570. https://doi.org/10.4319/lo.2005.50.5.1565