Phytoplankton (Algae) Blooms - Revision history

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Jhurley at 19:12, 20 November 2019

2019-11-20T19:12:29Z

Jhurley: /* Phytoplankton */

2019-11-20T18:44:48Z

‎Phytoplankton

Jhurley at 18:40, 20 November 2019

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Jhurley: /* Bloom Mitigation Strategies */

2019-11-20T17:03:27Z

‎Bloom Mitigation Strategies

Jhurley: /* Bloom Mitigation Strategies */

2019-11-20T16:21:42Z

‎Bloom Mitigation Strategies

Jhurley at 16:14, 20 November 2019

2019-11-20T16:14:15Z

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 ==Consequences of Phytoplankton Blooms==
 </onlyinclude>
-<onlyinclude>Phytoplankton blooms threaten the health of aquatic organisms and the health of humans, pets, or livestock that use affected waters for drinking or recreation. High concentrations of phytoplankton during bloom conditions colors and clouds the water limiting the transmission of light in the water column. In shallow systems, light levels along the bottom may become insufficient to support beneficial submerged aquatic vegetation (SAV) that provide habitat, remove nutrients from the water column, and stabilize bottom sediments. Once the SAV is gone, suspension of destabilized sediments causes an increase in turbidity, which in turn often prevents the SAV from returning.  The nutrients that were previously consumed by SAV, are consumed by phytoplankton instead, further perpetuating blooms.  These feedback mechanisms can trap a water body in this undesirable alternative stable state</onlyinclude><ref>Scheffer, M.,  Jeppesen, E. 1998. Alternative Stable States. ''In:'' The Structuring Role of Submerged Macrophytes in Lakes (ed. E. Jeppesen, M. Sondergaard, M. Sondergaard & K. Christoffersen). Ecological Studies (Analysis and Synthesis), vol. 131, pp. 397-406. Springer, New York, NY [https://doi.org/10.1007/978-1-4612-0695-8_31 doi: 10.1007/978-1-4612-0695-8_31 ]</ref>.
+<onlyinclude>Phytoplankton blooms threaten the health of aquatic organisms and the health of humans, pets, or livestock that use affected waters for drinking or recreation. High concentrations of phytoplankton during bloom conditions colors and clouds the water limiting the transmission of light in the water column. </onlyinclude>In shallow systems, light levels along the bottom may become insufficient to support beneficial submerged aquatic vegetation (SAV) that provide habitat, remove nutrients from the water column, and stabilize bottom sediments. Once the SAV is gone, suspension of destabilized sediments causes an increase in turbidity, which in turn often prevents the SAV from returning.  The nutrients that were previously consumed by SAV, are consumed by phytoplankton instead, further perpetuating blooms.  These feedback mechanisms can trap a water body in this undesirable alternative stable state<ref>Scheffer, M.,  Jeppesen, E. 1998. Alternative Stable States. ''In:'' The Structuring Role of Submerged Macrophytes in Lakes (ed. E. Jeppesen, M. Sondergaard, M. Sondergaard & K. Christoffersen). Ecological Studies (Analysis and Synthesis), vol. 131, pp. 397-406. Springer, New York, NY [https://doi.org/10.1007/978-1-4612-0695-8_31 doi: 10.1007/978-1-4612-0695-8_31 ]</ref>.
 Of all the negative impacts of phytoplankton blooms, production of toxins by some bloom-forming species represents the most direct threat to human health. Cyanobacteria and [[wikipedia:Dinoflagellate |dinoflagellates]] are the most common toxin producing group of phytoplankton in fresh and marine waters, respectively. Cyanobacteria produce a wide variety of cyanotoxins including hepatotoxic (liver-damaging) microcystins, nodularins, and cylindrospermopsins, neurotoxic (nerve-damaging) saxitoxins and anatoxins, and dermatoxic (skin-damaging) lyngbya toxins<ref>Humpage, A. 2008. Toxin types, toxicokinetics and toxicodynamics. ''In:'' Hudnell, K. (Ed). Cyanobacterial harmful algal blooms: State of the science and research needs. Advances in Experimental Medicine and Biology Volume 619, pp 383-416, Springer.  [https://link.springer.com/chapter/10.1007/978-0-387-75865-7_16  doi: 10.1007/978-0-387-75865-7_16]</ref>.

@@ Line 13: / Line 13: @@
 *[https://www.epa.gov/nutrientpollution/harmful-algal-blooms US EPA - Harmful Algal Blooms]
 <onlyinclude>
-==Phytoplankton==</onlyinclude>
+==Phytoplankton==
 <onlyinclude>[[wikipedia:Phytoplankton | Phytoplankton]] are microscopic, unicellular, filamentous, or colonial, photosynthetic microalgae or cyanobacteria that live in water </onlyinclude>(Figure 1)<onlyinclude>. A [[wikipedia:Algal_bloom | phytoplankton bloom]] is the development of a level of phytoplankton biomass that is uncharacteristically high for a given water body</onlyinclude><ref>Carstensen, J., Henriksen, P. and Heiskanen, A.S., 2007. Summer algal blooms in shallow estuaries: definition, mechanisms, and link to eutrophication. Limnology and Oceanography, 52(1), pp.370-384. [https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.2007.52.1.0370 DOI:10.4319/lo.2007.52.1.0370]</ref><onlyinclude>. Often, but not always, blooms are formed by a single species.</onlyinclude>
 [[File:Hall1w2Fig1.png|thumb|Figure 1. Phytoplankton come in many shapes and sizes.]]
@@ Line 37: / Line 38: @@
 The reciprocal of dilution rate is the water residence time which is the average amount of time that a parcel of water spends within a body of water. Generally, water bodies with residence times of a few days or less will not develop phytoplankton blooms.  In water bodies with long residence times (e.g. more than a couple of weeks), phytoplankton blooms are more likely to develop. In addition to natural flow conditions, residence time and bloom development can be affected by water control infrastructure<ref>Gasith, A. and Gafny, S., 1998. Importance of Physical Structures in Lakes: the Case of Lake Kinneret and General Implications.  ''In:'' The Structuring Role of Submerged Macrophytes in Lakes (ed. E. Jeppesen, M. Sondergaard, M. Sondergaard & K. Christoffersen). Ecological Studies (Analysis and Synthesis), vol. 131, pp. 331-338. Springer, New York, NY. [https://doi.org/10.1007/978-1-4612-0695-8_24 doi:10.1007/978-1-4612-0695-8_24]</ref><ref>Hall, N.S., Paerl, H.W., Peierls, B.L., Whipple, A.C. and Rossignol, K.L., 2013. Effects of climatic variability on phytoplankton community structure and bloom development in the eutrophic, microtidal, New River Estuary, North Carolina, USA. Estuarine, Coastal and Shelf Science, 117, pp.70-82. [https://doi.org/10.1016/j.ecss.2012.10.004 doi: 10.1016/j.ecss.2012.10.004]</ref><ref>Scavia, D. and Liu, Y., 2009. Exploring estuarine nutrient susceptibility. Environmental Science & Technology, 43(10), pp.3474-3479. [https://doi.org/10.1021/es803401y doi: 10.1021/es803401y]</ref>. Dams and other flow manipulating structures (e.g. causeways, pumping stations, locks etc.) can significantly increase the residence time and can therefore greatly increase the potential for phytoplankton bloom development.
 <onlyinclude>
-==Consequences of Phytoplankton Blooms==</onlyinclude>
+==Consequences of Phytoplankton Blooms==
 <onlyinclude>Phytoplankton blooms threaten the health of aquatic organisms and the health of humans, pets, or livestock that use affected waters for drinking or recreation. High concentrations of phytoplankton during bloom conditions colors and clouds the water limiting the transmission of light in the water column. In shallow systems, light levels along the bottom may become insufficient to support beneficial submerged aquatic vegetation (SAV) that provide habitat, remove nutrients from the water column, and stabilize bottom sediments. Once the SAV is gone, suspension of destabilized sediments causes an increase in turbidity, which in turn often prevents the SAV from returning.  The nutrients that were previously consumed by SAV, are consumed by phytoplankton instead, further perpetuating blooms.  These feedback mechanisms can trap a water body in this undesirable alternative stable state</onlyinclude><ref>Scheffer, M.,  Jeppesen, E. 1998. Alternative Stable States. ''In:'' The Structuring Role of Submerged Macrophytes in Lakes (ed. E. Jeppesen, M. Sondergaard, M. Sondergaard & K. Christoffersen). Ecological Studies (Analysis and Synthesis), vol. 131, pp. 397-406. Springer, New York, NY [https://doi.org/10.1007/978-1-4612-0695-8_31 doi: 10.1007/978-1-4612-0695-8_31 ]</ref>.

@@ Line 1: / Line 1: @@
-Blooms of [[wikipedia:Phytoplankton | phytoplankton]] or [[wikipedia:Algae | algae]] can cause major environmental problems. [[wikipedia:Algal blooms | Harmful algal blooms (HABs)]] occur when phytoplankton (algae and [[wikipedia:Cyanobacteria | cyanobacteria]]) rapidly increase or accumulate, producing harmful conditions that negatively impact people, freshwater and marine ecosystems, and economies. Certain environmental conditions including high nutrient concentrations from stormwater runoff or wastewater and insufficient mixing of the water column can trigger HABs.
+<onlyinclude>Blooms of [[wikipedia:Phytoplankton | phytoplankton]] or [[wikipedia:Algae | algae]] can cause major environmental problems. [[wikipedia:Algal blooms | Harmful algal blooms (HABs)]] occur when phytoplankton (algae and [[wikipedia:Cyanobacteria | cyanobacteria]]) rapidly increase or accumulate, producing harmful conditions that negatively impact people, freshwater and marine ecosystems, and economies. Certain environmental conditions including high nutrient concentrations from stormwater runoff or wastewater and insufficient mixing of the water column can trigger HABs. </onlyinclude>
 <div style="float:right;margin:0 0 2em 2em;">__TOC__</div>
@@ Line 12: / Line 12: @@
 *[https://oceanservice.noaa.gov/facts/eutrophication.html NOAA Eutrophication]
 *[https://www.epa.gov/nutrientpollution/harmful-algal-blooms US EPA - Harmful Algal Blooms]
+<onlyinclude>
-==Phytoplankton==
+==Phytoplankton==</onlyinclude>
-[[wikipedia:Phytoplankton | Phytoplankton]] are microscopic, unicellular, filamentous, or colonial, photosynthetic microalgae or cyanobacteria that live in water (Figure 1). A [[wikipedia:Algal_bloom | phytoplankton bloom]] is the development of a level of phytoplankton biomass that is uncharacteristically high for a given water body<ref>Carstensen, J., Henriksen, P. and Heiskanen, A.S., 2007. Summer algal blooms in shallow estuaries: definition, mechanisms, and link to eutrophication. Limnology and Oceanography, 52(1), pp.370-384. [https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.2007.52.1.0370 DOI:10.4319/lo.2007.52.1.0370]</ref>. Often, but not always, blooms are formed by a single species.
+<onlyinclude>[[wikipedia:Phytoplankton | Phytoplankton]] are microscopic, unicellular, filamentous, or colonial, photosynthetic microalgae or cyanobacteria that live in water </onlyinclude>(Figure 1)<onlyinclude>. A [[wikipedia:Algal_bloom | phytoplankton bloom]] is the development of a level of phytoplankton biomass that is uncharacteristically high for a given water body</onlyinclude><ref>Carstensen, J., Henriksen, P. and Heiskanen, A.S., 2007. Summer algal blooms in shallow estuaries: definition, mechanisms, and link to eutrophication. Limnology and Oceanography, 52(1), pp.370-384. [https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.2007.52.1.0370 DOI:10.4319/lo.2007.52.1.0370]</ref><onlyinclude>. Often, but not always, blooms are formed by a single species.</onlyinclude>
 [[File:Hall1w2Fig1.png|thumb|Figure 1. Phytoplankton come in many shapes and sizes.]]
@@ Line 36: / Line 36: @@
 The reciprocal of dilution rate is the water residence time which is the average amount of time that a parcel of water spends within a body of water. Generally, water bodies with residence times of a few days or less will not develop phytoplankton blooms.  In water bodies with long residence times (e.g. more than a couple of weeks), phytoplankton blooms are more likely to develop. In addition to natural flow conditions, residence time and bloom development can be affected by water control infrastructure<ref>Gasith, A. and Gafny, S., 1998. Importance of Physical Structures in Lakes: the Case of Lake Kinneret and General Implications.  ''In:'' The Structuring Role of Submerged Macrophytes in Lakes (ed. E. Jeppesen, M. Sondergaard, M. Sondergaard & K. Christoffersen). Ecological Studies (Analysis and Synthesis), vol. 131, pp. 331-338. Springer, New York, NY. [https://doi.org/10.1007/978-1-4612-0695-8_24 doi:10.1007/978-1-4612-0695-8_24]</ref><ref>Hall, N.S., Paerl, H.W., Peierls, B.L., Whipple, A.C. and Rossignol, K.L., 2013. Effects of climatic variability on phytoplankton community structure and bloom development in the eutrophic, microtidal, New River Estuary, North Carolina, USA. Estuarine, Coastal and Shelf Science, 117, pp.70-82. [https://doi.org/10.1016/j.ecss.2012.10.004 doi: 10.1016/j.ecss.2012.10.004]</ref><ref>Scavia, D. and Liu, Y., 2009. Exploring estuarine nutrient susceptibility. Environmental Science & Technology, 43(10), pp.3474-3479. [https://doi.org/10.1021/es803401y doi: 10.1021/es803401y]</ref>. Dams and other flow manipulating structures (e.g. causeways, pumping stations, locks etc.) can significantly increase the residence time and can therefore greatly increase the potential for phytoplankton bloom development.
+<onlyinclude>
-==Consequences of Phytoplankton Blooms==
+==Consequences of Phytoplankton Blooms==</onlyinclude>
-Phytoplankton blooms threaten the health of aquatic organisms and the health of humans, pets, or livestock that use affected waters for drinking or recreation. High concentrations of phytoplankton during bloom conditions colors and clouds the water limiting the transmission of light in the water column. In shallow systems, light levels along the bottom may become insufficient to support beneficial submerged aquatic vegetation (SAV) that provide habitat, remove nutrients from the water column, and stabilize bottom sediments. Once the SAV is gone, suspension of destabilized sediments causes an increase in turbidity, which in turn often prevents the SAV from returning.  The nutrients that were previously consumed by SAV, are consumed by phytoplankton instead, further perpetuating blooms.  These feedback mechanisms can trap a water body in this undesirable alternative stable state<ref>Scheffer, M.,  Jeppesen, E. 1998. Alternative Stable States. ''In:'' The Structuring Role of Submerged Macrophytes in Lakes (ed. E. Jeppesen, M. Sondergaard, M. Sondergaard & K. Christoffersen). Ecological Studies (Analysis and Synthesis), vol. 131, pp. 397-406. Springer, New York, NY [https://doi.org/10.1007/978-1-4612-0695-8_31 doi: 10.1007/978-1-4612-0695-8_31 ]</ref>.
+<onlyinclude>Phytoplankton blooms threaten the health of aquatic organisms and the health of humans, pets, or livestock that use affected waters for drinking or recreation. High concentrations of phytoplankton during bloom conditions colors and clouds the water limiting the transmission of light in the water column. In shallow systems, light levels along the bottom may become insufficient to support beneficial submerged aquatic vegetation (SAV) that provide habitat, remove nutrients from the water column, and stabilize bottom sediments. Once the SAV is gone, suspension of destabilized sediments causes an increase in turbidity, which in turn often prevents the SAV from returning.  The nutrients that were previously consumed by SAV, are consumed by phytoplankton instead, further perpetuating blooms.  These feedback mechanisms can trap a water body in this undesirable alternative stable state</onlyinclude><ref>Scheffer, M.,  Jeppesen, E. 1998. Alternative Stable States. ''In:'' The Structuring Role of Submerged Macrophytes in Lakes (ed. E. Jeppesen, M. Sondergaard, M. Sondergaard & K. Christoffersen). Ecological Studies (Analysis and Synthesis), vol. 131, pp. 397-406. Springer, New York, NY [https://doi.org/10.1007/978-1-4612-0695-8_31 doi: 10.1007/978-1-4612-0695-8_31 ]</ref>.
 Of all the negative impacts of phytoplankton blooms, production of toxins by some bloom-forming species represents the most direct threat to human health. Cyanobacteria and [[wikipedia:Dinoflagellate |dinoflagellates]] are the most common toxin producing group of phytoplankton in fresh and marine waters, respectively. Cyanobacteria produce a wide variety of cyanotoxins including hepatotoxic (liver-damaging) microcystins, nodularins, and cylindrospermopsins, neurotoxic (nerve-damaging) saxitoxins and anatoxins, and dermatoxic (skin-damaging) lyngbya toxins<ref>Humpage, A. 2008. Toxin types, toxicokinetics and toxicodynamics. ''In:'' Hudnell, K. (Ed). Cyanobacterial harmful algal blooms: State of the science and research needs. Advances in Experimental Medicine and Biology Volume 619, pp 383-416, Springer.  [https://link.springer.com/chapter/10.1007/978-0-387-75865-7_16  doi: 10.1007/978-0-387-75865-7_16]</ref>.

← Older revision		Revision as of 19:12, 20 November 2019
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−	'''CONTRIBUTOR(S):''' [[Dr. Nathan Hall]] and [[Dr. Katie Werkhoven]]	+	'''CONTRIBUTOR(S):''' [[Dr. Nathan Hall]] and [[Dr. Katie van Werkhoven]]

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 '''Phytoplankton Mortality. ''' Consumption by organisms at higher trophic levels generally constitutes the largest source of mortality for phytoplankton. Grazing by protistan zooplankton is often the dominant source of mortality for phytoplankton in marine waters<ref>Schmoker, C., Hernández-León, S. and Calbet, A., 2013. Microzooplankton grazing in the oceans: impacts, data variability, knowledge gaps and future directions. Journal of Plankton Research, 35(4), pp.691-706. [https://doi.org/10.1093/plankt/fbt023 doi: 10.1093/plankt/fbt023]</ref>, while grazing by crustacean zooplankton is often more important in freshwaters<ref>Tessier, A.J., Bizina, E.V. and Geedey, K.C., 2001. Grazer - resource interactions in the plankton: Are all daphniids alike. Limnology and Oceanography, 46(7), pp.1585-1595. [https://doi.org/10.4319/lo.2001.46.7.1585 doi: 10.4319/lo.2001.46.7.1585]</ref>. In shallow systems with a relatively low ratio of volume to [[wikipedia:Benthic zone | benthic]] surface area, grazing by benthic bivalves can be substantial and dominate grazing losses<ref>Cloern, J.E., 1982. Does the Benthos Control Phytoplankton Biomass in South San Francisco Bay. Marine Ecology Progress Series. Oldendorf, 9(2), pp.191-202. [https://doi.org/10.3354/meps009191 doi:  10.3354/meps009191 ]</ref>. Infections by viruses, fungi, bacteria, and protists can also contribute substantially to phytoplankton mortality. High cell densities of a single-species bloom favor the spread of infections during blooms, and can result in rapid bloom termination<ref>Lehahn, Y., Koren, I., Schatz, D., Frada, M., Sheyn, U., Boss, E., Efrati, S., Rudich, Y., Trainic, M., Sharoni, S. and Laber, C., 2014. Decoupling physical from biological processes to assess the impact of viruses on a mesoscale algal bloom. Current Biology, 24(17), pp.2041-2046. [https://doi.org/10.1016/j.cub.2014.07.046 doi: 10.1016/j.cub.2014.07.046]</ref><ref>Von Donk, E. and Ringelberg, J., 1983. The effect of fungal parasitism on the succession of diatoms in Lake Maarsseveen I (The Netherlands). Freshwater Biology, 13(3), pp.241-251. [https://doi.org/10.1111/j.1365-2427.1983.tb00674.x doi: 10.1111/j.1365-2427.1983.tb00674.x]</ref>.
-'''Sedimentation.''' Phytoplankton are typically 3 to 5 percent denser than their surrounding environment. Consequently, most phytoplankton are constantly sinking and require turbulent mixing to stay in the upper mixed layer where light levels are appropriate for growth. According to [[wikipedia:Stoke’s law | Stoke’s law]], larger and more dense phytoplankton tend to sink faster (0.1-1 m/d) while settling velocities are negligible for the smallest phytoplankton (0.001 m/d)<ref>Fogg, G.E., 1991. The phytoplanktonic ways of life. New Phytologist, 118(2), pp.191-232. [https://doi.org/10.1111/j.1469-8137.1991.tb00974.x doi: 10.1111/j.1469-8137.1991.tb00974.x]</ref>. Many phytoplankton, particularly bloom-forming taxa, avoid settling losses by having either flagella that allow them to swim or ballast mechanisms that provide buoyancy<ref>Paerl, H.W., 1988. Nuisance phytoplankton blooms in coastal, estuarine, and inland waters 1. Limnology and Oceanography, 33(4part2), pp.823-843. [https://doi.org/10.4319/lo.1988.33.4part2.0823 doi: 10.4319/lo.1988.33.4part2.0823]</ref>. Cyanobacteria are notorious for accumulating by flotation into dense surface scums (Figure 2).
+'''Sedimentation.''' Phytoplankton are typically 3 to 5 percent denser than their surrounding environment. Consequently, most phytoplankton are constantly sinking and require turbulent mixing to stay in the upper mixed layer where light levels are appropriate for growth. According to [[wikipedia:Stokes’ law | Stokes’ law]], larger and more dense phytoplankton tend to sink faster (0.1-1 m/d) while settling velocities are negligible for the smallest phytoplankton (0.001 m/d)<ref>Fogg, G.E., 1991. The phytoplanktonic ways of life. New Phytologist, 118(2), pp.191-232. [https://doi.org/10.1111/j.1469-8137.1991.tb00974.x doi: 10.1111/j.1469-8137.1991.tb00974.x]</ref>. Many phytoplankton, particularly bloom-forming taxa, avoid settling losses by having either flagella that allow them to swim or ballast mechanisms that provide buoyancy<ref>Paerl, H.W., 1988. Nuisance phytoplankton blooms in coastal, estuarine, and inland waters 1. Limnology and Oceanography, 33(4part2), pp.823-843. [https://doi.org/10.4319/lo.1988.33.4part2.0823 doi: 10.4319/lo.1988.33.4part2.0823]</ref>. Cyanobacteria are notorious for accumulating by flotation into dense surface scums (Figure 2).
 [[File:Hall1w2Fig2.png|thumb| Figure 2.  Surface scum of the cyanobacteria, ''Microcystsis sp.'' in the Chowan River, NC. Photo credit, Chowan/Edenton Environmental Group]]

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 '''Water Column Mixing. ''' Artificial vertical mixing can reduce the intensity of cyanobacteria blooms through two mechanisms. First, mixing oxygenated surface waters downward reduces sediment loading of N and P that results when sediments become anoxic. Second, vigorous vertical mixing negates the floating ability of cyanobacteria which leads to lower light availability and minimizes the competitive advantage buoyant taxa have over more desirable, negatively buoyant taxa (e.g. green algae and diatoms)<ref>Huisman, J., Sharples, J., Stroom, J.M., Visser, P.M., Kardinaal, W.E.A., Verspagen, J.M. and Sommeijer, B., 2004. Changes in turbulent mixing shift competition for light between phytoplankton species. Ecology, 85(11), pp.2960-2970. [https://doi.org/10.1890/03-0763 doi: 10.1890/03-0763]</ref>. Energy requirements to produce sufficiently vigorous mixing are high, and attempts to mix large water bodies with low powered mixers have been unsuccessful<ref>Olson, I., 2016. Evaluating the effectiveness of water remediation techniques for nutrient reduction and the control of cyanobacteria blooms in municipal drinking water reservoirs in the SE United States. Master's Thesis, N.C. State University.  [[media:2016-Olson-Evaluating_the_effectiveness_of_water_remediation_techniques.pdf| Report.pdf]]</ref><ref>Upadhyay, S., Bierlein, K.A., Little, J.C., Burch, M.D., Elam, K.P. and Brookes, J.D., 2013. Mixing potential of a surface-mounted solar-powered water mixer (SWM) for controlling cyanobacterial blooms. Ecological Engineering, 61, pp.245-250. [https://doi.org/10.1016/j.ecoleng.2013.09.032 doi: 10.1016/j.ecoleng.2013.09.032]</ref>. For large water bodies, nutrient control and, where possible, prevention of long residence time conditions are the most feasible, long term solutions to bloom problems<ref name= "Paerl2011"/>.
-'''Legacy Nutrient Removal. ''' Organic-rich sediments that result from decades of nutrient over-enrichment can continue to provide high internal nutrient loads that fuel blooms even after external sources of N and P have been reduced<ref name= "Paerl2011"/>.  Application of alum or modified clay has been used successfully in small to medium sized freshwater bodies to flocculate P and phytoplankton cells out of the water column. Once the clay has settled, it can form a cap on the sediments to prevent P from diffusing back to the water column during anoxic periods. Physical removal of organic rich surficial sediments by dredging has also been used effectively but the high cost of both clay application and dredging largely restricts this practice to small water bodies<ref name= "Paerl2011"/>. Nutrients in a water body can also be intercepted and removed from a water body by intentionally growing and harvesting macroalgae in a relatively new process called algal turf scrubbing <ref>Craggs, R.J., Adey, W.H., Jenson, K.R., John, M.S.S., Green, F.B. and Oswald, W.J., 1996. Phosphorus removal from wastewater using an algal turf scrubber. Water Science and Technology, 33(7), pp.191-198. [https://iwaponline.com/wst/article-pdf/33/7/191/28477/191.pdf doi: 10.2166/wst.1996.0138]</ref>.
+'''Legacy Nutrient Removal. ''' Organic-rich sediments that result from decades of nutrient over-enrichment can continue to provide high internal nutrient loads that fuel blooms even after external sources of N and P have been reduced<ref name= "Paerl2011"/>.  Application of alum or modified clay has been used successfully in small to medium sized freshwater bodies to flocculate P and phytoplankton cells out of the water column. Once the clay has settled, it can form a cap on the sediments to prevent P from diffusing back to the water column during anoxic periods. Physical removal of organic rich surficial sediments by dredging has also been used effectively but the high cost of both clay application and dredging largely restricts this practice to small water bodies<ref name= "Paerl2011"/>. Nutrients in a water body can also be intercepted and removed from a water body by intentionally growing and harvesting macroalgae in a relatively new process called algal turf scrubbing <ref>Craggs, R.J., Adey, W.H., Jenson, K.R., St. John, M.S., Green, F.B. and Oswald, W.J., 1996. Phosphorus removal from wastewater using an algal turf scrubber. Water Science and Technology, 33(7), pp.191-198. [https://iwaponline.com/wst/article-pdf/33/7/191/28477/191.pdf doi: 10.2166/wst.1996.0138]</ref>.
 '''Biological and Chemical Controls. ''' For some water bodies, blooms can be managed by manipulating the food web (e.g. removing certain fishes) to increase the numbers of zooplankton grazers<ref>Carpenter, S.R., Kitchell, J.F. and Hodgson, J.R., 1985. Cascading trophic interactions and lake productivity. BioScience, 35(10), pp.634-639. [https://doi.org/10.2307/1309989 doi: 10.2307/1309989]</ref><ref>Triest, L., Stiers, I. and Van Onsem, S., 2016. Biomanipulation as a nature-based solution to reduce cyanobacterial blooms. Aquatic Ecology, 50(3), pp.461-483. [https://doi.org/10.1007/s10452-015-9548-x doi: 10.1007/s10452-015-9548-x]</ref>. As a very short-term fix, algaecides can be used to control phytoplankton blooms. Copper-based algaecides can effectively kill most phytoplankton groups, and algaecides containing hydrogen peroxide can be equally effective on cyanobacteria<ref>Matthijs, H.C., Visser, P.M., Reeze, B., Meeuse, J., Slot, P.C., Wijn, G., Talens, R. and Huisman, J., 2012. Selective suppression of harmful cyanobacteria in an entire lake with hydrogen peroxide. Water Research, 46(5), pp.1460-1472. [https://doi.org/10.1016/j.watres.2011.11.016 doi: 10.1016/j.watres.2011.11.016]</ref>, without potential unintended toxic effects on higher trophic levels<ref>Willis, B.E. and Bishop, W.M., 2016. Understanding fate and effects of copper pesticides in aquatic systems. Journal of Geoscience and Environment Protection, 4(05), pp. 37 - 42. [https://doi.org/10.4236/gep.2016.45004 doi: 10.4236/gep.2016.45004]</ref>. High costs of algaecide also largely restrict its use to small water bodies.

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 '''Reduce External Nutrient Loading. ''' The first step in designing nutrient controls is determining what nutrient(s) limit phytoplankton growth. Nitrogen (N) and phosphorus (P) have been commonly assumed to be the limiting nutrients for fresh and marine waters<ref name= "Howarth1988"/>, respectively.  However, recent studies<ref>Lewis Jr, W.M. and Wurtsbaugh, W.A., 2008. Control of lacustrine phytoplankton by nutrients: erosion of the phosphorus paradigm. International Review of Hydrobiology, 93(4‐5), pp.446-465. [https://doi.org/10.1002/iroh.200811065 doi: 10.1002/iroh.200811065]</ref><ref>Paerl, H.W., Scott, J.T., McCarthy, M.J., Newell, S.E., Gardner, W.S., Havens, K.E., Hoffman, D.K., Wilhelm, S.W. and Wurtsbaugh, W.A., 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), pp.10805-10813. [https://doi.org/10.1021/acs.est.6b02575  doi: 10.1021/acs.est.6b02575]</ref> have shown that the limiting nutrient can change seasonally. Once the limiting nutrients have been identified, nutrient reduction targets are generally formulated using models that relate nutrient loads to phytoplankton biomass. These models may be experimental models with natural water containing the natural phytoplankton communities, simple nutrient budget-based models, or mechanistic, coupled circulation/water quality models. Mechanistic circulation/water quality models are the primary means of designing mitigation options for large water bodies. Enacting watershed-based controls on nutrient sources is the best strategy for large water bodies<ref name= "Paerl2011">Paerl, H.W., Hall, N.S. and Calandrino, E.S., 2011. Controlling harmful cyanobacterial blooms in a world experiencing anthropogenic and climatic-induced change. Science of the Total Environment, 409(10), pp.1739-1745. [https://doi.org/10.1016/j.scitotenv.2011.02.001 doi: 10.1016/j.scitotenv.2011.02.001]</ref>.
-'''Water Column Mixing. ''' Artificial vertical mixing can reduce the intensity of cyanobacteria blooms through two mechanisms. First, mixing oxygenated surface waters downward reduces sediment loading of N and P that results when sediments become anoxic. Second, vigorous vertical mixing negates the floating ability of cyanobacteria which leads to lower light availability and minimizes the competitive advantage buoyant taxa have over more desirable, negatively buoyant taxa (e.g. green algae and diatoms)<ref>Huisman, J., Sharples, J., Stroom, J.M., Visser, P.M., Kardinaal, W.E.A., Verspagen, J.M. and Sommeijer, B., 2004. Changes in turbulent mixing shift competition for light between phytoplankton species. Ecology, 85(11), pp.2960-2970. [https://doi.org/10.1890/03-0763 doi: 10.1890/03-0763]</ref>. Energy requirements to produce sufficiently vigorous mixing are high, and attempts to mix large water bodies with low powered mixers have been unsuccessful<ref>Olson, I., 2016. Evaluating the effectiveness of water remediation techniques for nutrient reduction and the control of cyanobacteria blooms in municipal drinking water reservoirs in the SE United States. Master's Thesis, N.C. State University [[media:2016-Olson-Evaluating_the_effectiveness_of_water_remediation_techniques.pdf| Report.pdf]]</ref><ref>Upadhyay, S., Bierlein, K.A., Little, J.C., Burch, M.D., Elam, K.P. and Brookes, J.D., 2013. Mixing potential of a surface-mounted solar-powered water mixer (SWM) for controlling cyanobacterial blooms. Ecological Engineering, 61, pp.245-250. [https://doi.org/10.1016/j.ecoleng.2013.09.032 doi: 10.1016/j.ecoleng.2013.09.032]</ref>. For large water bodies, nutrient control and, where possible, prevention of long residence time conditions are the most feasible, long term solutions to bloom problems<ref name= "Paerl2011"/>.
+'''Water Column Mixing. ''' Artificial vertical mixing can reduce the intensity of cyanobacteria blooms through two mechanisms. First, mixing oxygenated surface waters downward reduces sediment loading of N and P that results when sediments become anoxic. Second, vigorous vertical mixing negates the floating ability of cyanobacteria which leads to lower light availability and minimizes the competitive advantage buoyant taxa have over more desirable, negatively buoyant taxa (e.g. green algae and diatoms)<ref>Huisman, J., Sharples, J., Stroom, J.M., Visser, P.M., Kardinaal, W.E.A., Verspagen, J.M. and Sommeijer, B., 2004. Changes in turbulent mixing shift competition for light between phytoplankton species. Ecology, 85(11), pp.2960-2970. [https://doi.org/10.1890/03-0763 doi: 10.1890/03-0763]</ref>. Energy requirements to produce sufficiently vigorous mixing are high, and attempts to mix large water bodies with low powered mixers have been unsuccessful<ref>Olson, I., 2016. Evaluating the effectiveness of water remediation techniques for nutrient reduction and the control of cyanobacteria blooms in municipal drinking water reservoirs in the SE United States. Master's Thesis, N.C. State University.  [[media:2016-Olson-Evaluating_the_effectiveness_of_water_remediation_techniques.pdf| Report.pdf]]</ref><ref>Upadhyay, S., Bierlein, K.A., Little, J.C., Burch, M.D., Elam, K.P. and Brookes, J.D., 2013. Mixing potential of a surface-mounted solar-powered water mixer (SWM) for controlling cyanobacterial blooms. Ecological Engineering, 61, pp.245-250. [https://doi.org/10.1016/j.ecoleng.2013.09.032 doi: 10.1016/j.ecoleng.2013.09.032]</ref>. For large water bodies, nutrient control and, where possible, prevention of long residence time conditions are the most feasible, long term solutions to bloom problems<ref name= "Paerl2011"/>.
 '''Legacy Nutrient Removal. ''' Organic-rich sediments that result from decades of nutrient over-enrichment can continue to provide high internal nutrient loads that fuel blooms even after external sources of N and P have been reduced<ref name= "Paerl2011"/>.  Application of alum or modified clay has been used successfully in small to medium sized freshwater bodies to flocculate P and phytoplankton cells out of the water column. Once the clay has settled, it can form a cap on the sediments to prevent P from diffusing back to the water column during anoxic periods. Physical removal of organic rich surficial sediments by dredging has also been used effectively but the high cost of both clay application and dredging largely restricts this practice to small water bodies<ref name= "Paerl2011"/>. Nutrients in a water body can also be intercepted and removed from a water body by intentionally growing and harvesting macroalgae in a relatively new process called algal turf scrubbing <ref>Craggs, R.J., Adey, W.H., Jenson, K.R., John, M.S.S., Green, F.B. and Oswald, W.J., 1996. Phosphorus removal from wastewater using an algal turf scrubber. Water Science and Technology, 33(7), pp.191-198. [https://iwaponline.com/wst/article-pdf/33/7/191/28477/191.pdf doi: 10.2166/wst.1996.0138]</ref>.
 '''Biological and Chemical Controls. ''' For some water bodies, blooms can be managed by manipulating the food web (e.g. removing certain fishes) to increase the numbers of zooplankton grazers<ref>Carpenter, S.R., Kitchell, J.F. and Hodgson, J.R., 1985. Cascading trophic interactions and lake productivity. BioScience, 35(10), pp.634-639. [https://doi.org/10.2307/1309989 doi: 10.2307/1309989]</ref><ref>Triest, L., Stiers, I. and Van Onsem, S., 2016. Biomanipulation as a nature-based solution to reduce cyanobacterial blooms. Aquatic Ecology, 50(3), pp.461-483. [https://doi.org/10.1007/s10452-015-9548-x doi: 10.1007/s10452-015-9548-x]</ref>. As a very short-term fix, algaecides can be used to control phytoplankton blooms. Copper-based algaecides can effectively kill most phytoplankton groups, and algaecides containing hydrogen peroxide can be equally effective on cyanobacteria<ref>Matthijs, H.C., Visser, P.M., Reeze, B., Meeuse, J., Slot, P.C., Wijn, G., Talens, R. and Huisman, J., 2012. Selective suppression of harmful cyanobacteria in an entire lake with hydrogen peroxide. Water Research, 46(5), pp.1460-1472. [https://doi.org/10.1016/j.watres.2011.11.016 doi: 10.1016/j.watres.2011.11.016]</ref>, without potential unintended toxic effects on higher trophic levels<ref>Willis, B.E. and Bishop, W.M., 2016. Understanding fate and effects of copper pesticides in aquatic systems. Journal of Geoscience and Environment Protection, 4(05), pp. 37 - 42. [https://doi.org/10.4236/gep.2016.45004 doi: 10.4236/gep.2016.45004]</ref>. High costs of algaecide also largely restrict its use to small water bodies.
 ==References==