Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Harmful Algal Blooms 2010: Synopsis and Insight

1,723 views

Published on

Synopsis and insight into the harmful algal blooms that hit Grand Lake St. Marys in 2010.

  • Be the first to comment

Harmful Algal Blooms 2010: Synopsis and Insight

  1. 1. William E. Lynch Jr. Aquatic Ecosystem Management Specialist Ohio State University Extension Program
  2. 2. Winter (ice – 39 F) Low biomasses of all types Early Spring (40 – 50 F) Diatom bloom Spring – Early Summer (50 – 72 F) Green algae bloom P Limited Systems N Limited Systems Mid - Late Summer (72 – 80+ F) Green algae Mid - Late Summer (72 – 80+ F) Cyanobacteria bloom Fall (80+ – 50 F) Green algae or cyanobacteria early Diatom bloom late
  3. 3. Large Lakes and Reservoirs 2009
  4. 4. Large Lakes and Reservoirs 2010 2009
  5. 5. Those Where Microcystin > 20ppb ( WHO Recreational Standard ) 2010: Microcystin > 20 ppb Note: Nearly all were less than 1 ppb; WHO’s drinking water standard 2010
  6. 6. Why warnings for waters with low microcystin levels? <ul><li>Some also had low levels of anatoxin and saxotoxin. </li></ul><ul><li>WHO has not defined contact and drinking water standards for those two toxins. </li></ul><ul><li>Research has indicated they are more detrimental to human health, and quite likely at low levels. </li></ul><ul><li>Agencies across the U.S. often issue warnings when anatoxin and saxotoxin are detectable. “Better safe than sorry” strategy. </li></ul>
  7. 7. Ponds & Small Lakes Suspected based on provided description Confirmed based on site visit or provided sample
  8. 8. Have HAB’s Really Increased? <ul><li>Yes, to an extent. An increase in ponds and small lakes. </li></ul><ul><li>Calls and emails to OSU Extension’s Aquatic Ecosystem Specialist have increased noticeably. </li></ul><ul><li>However, nearly 40% of contacts reported their ponds have had these blooms in the past, often 10 years ago. </li></ul># of Contacts Note: nearly all occurred in August and Sept.
  9. 9. Are They New to Ohio’s Waters? <ul><li>No, cyanobacteria are have been in Ohio from the very beginning. </li></ul><ul><li>Thus, they are not a recent invasive from a distant global location; </li></ul><ul><li>Nor are they recent mutations now capable of causing problems. </li></ul><ul><li>Simply, they remain at low densities until ecological conditions are created that allow them to reproduce quickly and create dense blooms. </li></ul>
  10. 10. What Creates Favorable Ecological Conditions for Cyanobacteria? <ul><li>First and foremost, development of a nuisance algae bloom is indicative of elevated nutrients, particularly an excess of phosphorus. </li></ul><ul><li>Nitrogen : phosphorus ratios greater than 20:1 promote filamentous and good planktonic algae while ratios less than 10:1 promote development of HABs. </li></ul><ul><li>High water temperatures do not cause HABs directly, but can cause minor blooms in waters with slightly elevated nutrient levels. </li></ul>
  11. 11. Nitrogen – Phosphorus Ratio Important <ul><li>N:P ratios > 30:1 results in blooms of planktonic green algae that are beneficial to aquatic food webs. Ratios > 20:1 acceptable. </li></ul><ul><li>N:P ratios between 10:1 and 20:1 can support cyanobacteria blooms, particularly in warm water. </li></ul><ul><li>N:P ratios < 10:1 typically result in HAB’s as cyanobacteria flourish in nitrogen limiting systems. Remember many HAB species can fix nitrogen. </li></ul>
  12. 12. 0 25 30 20 15 10 5 Summer N:P Ratio Cyanobacteria Abundance (%) of Algal Community 0 25 50 75 100 oligotrophic mesotrophic eutrophic hypereutrophic Adapted from: United Nations Environment Program Div. Of Technology, Industry, & Economics
  13. 13. N:P Ratio 4/15 5/10 6/9 acceptable desirable No HAB’s
  14. 14. N:P Ratio – Grand Lake St. Mary's Example N:P Ratio 4/15 5/10 6/9 acceptable desirable 7/14 No HAB’s *** Toxins first detected in late June
  15. 15. N:P Ratio – Grand Lake St. Mary's Example N:P Ratio 4/15 5/10 6/9 acceptable desirable 7/14 No HAB’s *** Toxins first detected in late June 8/19 9/15 10/7 HAB’s Widespread
  16. 16. Grand Lake St. Mary's 2010 P Levels Phosphorus 4/15 5/10 6/9 Target (<34 ppb) 7/14 8/19 9/15 10/7 ppb
  17. 17. Grand Lake St. Mary's 2010 N Levels Nitrogen 4/15 5/10 6/9 Target (<930 ppb) 7/14 8/19 9/15 10/7 ppb
  18. 18. Summer Water Temperatures Play A Role! <ul><li>High N:P ratio: </li></ul><ul><ul><li>No HAB </li></ul></ul><ul><li>High N:P ratio: </li></ul><ul><ul><li>No HAB </li></ul></ul><ul><li>High N:P ratio: </li></ul><ul><ul><li>HAB’s rare </li></ul></ul>< 74 o F 74 o F - 80 o F >80 o F
  19. 19. Summer Water Temperatures Play A Role! <ul><li>High N:P ratio: </li></ul><ul><ul><li>No HAB </li></ul></ul><ul><li>Mod. N:P ratio </li></ul><ul><ul><li>No HAB </li></ul></ul><ul><li>High N:P ratio: </li></ul><ul><ul><li>No HAB </li></ul></ul><ul><li>Mod. N:P ratio </li></ul><ul><ul><li>No HAB </li></ul></ul><ul><li>High N:P ratio: </li></ul><ul><ul><li>HAB’s rare </li></ul></ul><ul><li>Mod. N:P ratio </li></ul><ul><ul><li>HAB’s uncommon </li></ul></ul>< 74 o F 74 o F - 80 o F >80 o F
  20. 20. Summer Water Temperatures Play A Role! <ul><li>High N:P ratio: </li></ul><ul><ul><li>No HAB </li></ul></ul><ul><li>Mod. N:P ratio </li></ul><ul><ul><li>No HAB </li></ul></ul><ul><li>Low N:P ratio </li></ul><ul><ul><li>HAB’s rare </li></ul></ul><ul><li>High N:P ratio: </li></ul><ul><ul><li>No HAB </li></ul></ul><ul><li>Mod. N:P ratio </li></ul><ul><ul><li>No HAB </li></ul></ul><ul><li>Low N:P ratio </li></ul><ul><ul><li>HAB’s common </li></ul></ul><ul><li>High N:P ratio: </li></ul><ul><ul><li>HAB’s rare </li></ul></ul><ul><li>Mod. N:P ratio </li></ul><ul><ul><li>HAB’s uncommon </li></ul></ul><ul><li>Low N:P ratio </li></ul><ul><ul><li>HAB’s common </li></ul></ul>< 74 o F 74 o F - 80 o F >80 o F
  21. 21. Sources of Nutrients <ul><li>External – little P input </li></ul><ul><li>Internal – little P input </li></ul>“ All is Fine Scenario”
  22. 22. <ul><li>External – large increase in watershed P loading </li></ul><ul><li>Internal – little P input, but slowly increasing </li></ul>“ Beginnings of a Problem”
  23. 23. <ul><li>External – continued large watershed P loading </li></ul><ul><li>Internal – large P inputs from bottom sediment build-up </li></ul>“ The Worst of Problems”
  24. 24. <ul><li>External – watershed P loadings reduced </li></ul><ul><li>Internal – large P inputs from bottom sediment build-up </li></ul>“ The Long Road to Recovery”
  25. 25. Internal Sources of Excessive Phosphorus <ul><li>50% of particulate organic P deposited on bottom is biologically regenerated and returned to water above as phosphate. </li></ul><ul><li>Internal P cycling from anoxic bottom sediments during summer stratification. </li></ul><ul><li>Shallow lakes (e.g. Grand Lake) rarely stratify, but localized oxygen depletions in muck laden bays and creek mouths will allow release of phosphorus. </li></ul>
  26. 26. External Sources of Excessive Phosphorus <ul><li>Very small watersheds allow “local” sources to have major effects. </li></ul><ul><li>Runoff from small scale domesticated animal paddocks (the pet horse) </li></ul><ul><li>Lawn fertilizer </li></ul><ul><li>Canada geese </li></ul><ul><li>Leaking septic systems </li></ul><ul><li>Feeding fish </li></ul>Ponds & Small Lakes
  27. 27. External Sources of Excessive Phosphorus Large Lakes & Reservoirs <ul><li>Very large watersheds allow “widespread” sources to accumulate and have major cumulative effects. </li></ul><ul><li>Runoff from manure applied to fields. </li></ul><ul><li>Agricultural fertilizer runoff. </li></ul><ul><li>Particulate P problem enough but . . </li></ul><ul><li>Dissolved reactive P is a major problem (100% bio-available) </li></ul>
  28. 28. Also Play a Role . . . <ul><li>Lake Retention Time – once a molecule of water enters a lake, how long is retained in the lake before going out the outlet. Calculated as volume / discharge rate. </li></ul><ul><ul><li>High retention times a major HAB concern if water is high in phosphorus. </li></ul></ul><ul><ul><li>Low retention times discourage HAB’s due to nutrient flushing plus high clay turbidity levels. </li></ul></ul><ul><li>Aquatic Vegetation Community – the more abundant the plant and filamentous algae community, the less likely an intense HAB will occur. </li></ul><ul><li>Intensity & Timing of Rainfall Events – Wet springs followed by dry summers enhance development of HAB’s. </li></ul>
  29. 29. Keeping a Perspective . . . <ul><li>Waters with high nutrient loadings and low N:P ratios will experience HAB blooms, even in cool summers. </li></ul><ul><li>Many of the HAB blooms in 2010 were “small scale”. In larger waters, they were very localized to bays and headwater areas. Most were caused by Microcystis, a non-nitrogen fixing cyanobacteria. </li></ul><ul><li>Very high water temperatures likely caused many of the “small scale” HAB’s. A cooler summer in 2011 may cause HAB numbers to decrease markedly. </li></ul><ul><li>Given the lack of definitive, science-based data on anatoxin and saxotoxin toxicity, warnings will continue to be posted on state lakes for the foreseeable future. </li></ul>
  30. 30. Final Thoughts <ul><li>HAB’s is ponds and small lakes are correctable with bottom aeration, nearby land use adjustments, algaecides, and even alum treatments. Improvements attained quickly. </li></ul><ul><li>Intense HAB’s in large lake and reservoirs are more difficult to correct and will require major changes in watershed management and adoption of agricultural BMP’s. Quick fixes are costly and fleeting given the external sources of nutrients constantly entering the water body. </li></ul>Questions?

×