IDENTIFICATION, ECOLOGY AND CONTROL OF...

IDENTIFICATION, ECOLOGY AND CONTROL OF NUISANCE

FRESHWATER ALGAE

KENNETH J. WAGNER, Ph.D, CLMWATER RESOURCE SERVICES

PART 1: THE PROBLEMS

ALGAL PROBLEMS

Algal problems include:• Ecological imbalances

• Physical impacts on the aquatic system

• Water quality alteration

• Aesthetic impairment

• Taste and odor

• Toxicity

ALGAL PROBLEMSEcological Imbalances

High algal densities:• Result from overly successful growth processes

and insufficient loss processes

• Represent inefficient processing of energy by higher trophic levels

• May direct energy flow to benthic/detrital pathways

• May actually reduce system productivity (productivity tends to be highest at intermediate biomass)

ALGAL PROBLEMSAesthetic Impairment

High algal densities lead to:

• High solids, low clarity

• High organic content

• Fluctuating DO and pH

• “Slimy” feel to the water

• Unaesthetic appearance

• Taste and odor

• Possible toxicity

ALGAL PROBLEMSTaste and Odor

• At sufficient density, all algae can produce taste and odor by virtue of organic content and decay

• Some algae produce specific taste and odor compounds that are released into the water

• Geosmin and Methylisoborneol (MIB) are the two most common T&O compounds; these can induce T&O at very low concentrations


T&O by blue-greens• Anabaena, Aphanizomenon, Microcystis, and

Oscillatoria are most common T&O producers, but many other genera produce T&O as well

• Geosmin and MIB often produced• Odors usually include musty, grassy, and

septic• May be produced by planktonic or benthic

growths


T&O by greens• Chara, Cladophora, Chlorococcales

(Dictyosphaerium, Scenedesmus, Pediastrum, Hydrodictyon), Volvocales (Chlamydomonas, Volvox), and desmids (Staurastrum, Closterium, Cosmarium, Spirogyra) are primary greens causing T&O, but almost any genus can induce T&O at high density

• Main odors are fishy, skunky, musty, grassy and septic (wide range, species-specific)

• Not usually as severe as with blue-greens


T&O by diatoms• Melosira/Aulacoseira, Stephanodiscus,

Cyclotella, Asterionella, Fragilaria/Synedra, and Tabellaria are primary diatoms causing T&O, usually only at high density

• Main odors are geranium, spicy and fishy, with occasional musty or grassy scent

• Not as severe as with blue-greens unless diatom density is very high


T&O by goldens• Synura, Dinobryon, Mallomonas, Uroglenopsis,

and Chrysosphaerella are major T&O producers, others impart odor at high density Main odors are cucumber, violet, spicy and fishy

• Can produce substantial T&O even at low density


T&O by other algae• Dinoflagellates can produce a

fishy or septic odor at elevated densities

• Euglenoids can produce a fishy odor at elevated densities

• Major die-off of high density algae may produce a septic smell

• Actinomycetes, a non-photosynthetic bacterium, can also produce geosmin and MIB


Control of T&O• Minimizing algal density and specific T&O

producers is desirable for T&O control• Activated carbon removes most T&O, but

effective use is slow and increases treatment cost

• Aeration/mixing may oxidize/volatilize T&O compounds, but not completely effective

• Possible toxic link, but no severe direct health effects known from T&O; aesthetic issues can be major

ALGAL PROBLEMSToxicity-Cyanotoxins

• Cyanobacteria are the primary toxin threats to people from freshwater; acute toxicity is rare, but chronic effects may be significant and are difficult to detect.

• Research (e.g., 3 papers in Lake and Reservoir Management in September 2009) indicates widespread occurrence of toxins but highly variable concentrations, even within lakes.

• Water treatment in typical supply facilities is adequate to minimize risk; the greatest risk is from substandard treatment systems and direct recreational contact.

• Some other algae produce toxins - Prymnesium, or golden blossom, can kill fish; marine dinoflagellates, or red tides, can be toxic to many animals and humans.

ALGAL PROBLEMSToxicity-Cyanotoxins

• Dermatotoxins– produce rashes and other

skin reactions, usually within a day (hours)

• Hepatotoxins– disrupt proteins that keep

the liver functioning, may act slowly (days to weeks)

• Neurotoxins– cause rapid paralysis of

skeletal and respiratory muscles (minutes)

ALGAL PROBLEMSToxicity-Which Blue-Green Has Which

Toxin?Blue-Green Algae Microcystin Nodularin Cylindro-

spermopsin Anatoxin Saxitoxin Dermato-

toxin Anabaena X X X X Anabaenopsis X Aphanizomenon X X X Cylindrospermopsis X Cylindrospermum X X Hapalosiphon X Lyngbya X X Microcystis X X Nodularia X X Nostoc X Oscillatoria X X X Schizothrix X Umezakia X

More forms found each year – methods or actual increase?

ALGAL PROBLEMSToxicity-Analytical Methods

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Bioassay(mouse)

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MassSpec LC/MS

HPLC

ELISAPhosphatase Assay

ALGAL PROBLEMSToxicity- Key Issues

• Acute and chronic toxicity levels -how much can be tolerated?

• Synergistic effects - those with liver or nerve disorders at higher risk

• Exposure routes - ingestion vs. skin

• Treatment options - avoid cell lysis, remove or neutralize toxins

ALGAL PROBLEMSRecommended Toxicity Precautions

• Monitor algal quantity and quality

• If potential toxin producers are detected, increase monitoring and test for toxins

• For water supplies, incorporate capability to treat for toxins (PAC or strong oxidation seem to be best)

• For recreational lakes, be prepared to warn users and/or limit contact recreation

• Avoid treatments that rupture cells

PART 2: ALGAL FORMS

Algal FormsAlgal “Blooms”

♦ Water discoloration usually defines bloom conditions

♦ Many possible algal groups can “bloom”

♦ Taste and odor sources, possible toxicity

♦ Potentially severe use impairment

Algal FormsAlgal Mats

♦ Can be bottom or surface mats -surface mats often start on the bottom

♦ Usually green or blue-green algae

♦ Possible taste and odor sources

♦ Potentially severe use impairment

Algal Types: Planktonic Blue-greens

Aphanizomenon

Microcystis

Anabaena

Coelosphaerium

Algal Types: Planktonic Blue-greensPlanktolyngbya Planktothrix

(Oscillatoria)

Algal Types: Planktonic Blue-greensGloeotrichia

Algal Types: Planktonic Blue-greensCylindrospermopsis

•A sub-tropical alga with toxic properties is moving north.

•Most often encountered in turbid reservoirs in late summer, along with a variety of other bluegreens.

Algal Types: Mat Forming Blue-greens

Oscillatoria

Lyngbya/Plectonema

Algal Types: Planktonic GreensPediastrum

Scenedesmus

Lagerheimia Dictyosphaerium

Schroederia

Oocystis

(Order Chlorococcales)

Algal Types: Planktonic Greens

Chlamydomonas

Pyramichlamys

Carteria

Eudorina

Volvox

(Order Volvocales)

Algal Types: Mat Forming Greens

Cladophorales, with Cladophora (above), Rhizoclonium and Pithophora

Zygnematales, with Spirogyra (above), Mougeotia and Zygnema

Hydrodictyon, an unusual type of Chlorococcales

Oedogoniales, with Oedogonium and Bulbochaete

Algal Types: Mat Forming GreensZygnematales - Unbranched filaments, highly

gelatinous

MougeotiaSpirogyra

Zygnema

Mats trap gases and may float to surface

Cladophorales - Large, multinucleate cells, reticulate chromatophores, filamentous forms

Pithophora

RhizocloniumCladophora



Hydrodictyon

Oedogonium

Bulbochaete

Algal Types: Planktonic Diatoms

Aulacoseira

Asterionella

Cyclotella

Algal Types: Planktonic Diatoms

Fragilaria NitzschiaTabellaria

Algal Types: Plankton Goldens

Dinobryon

Synura

Chrysosphaerella

Prymnesium

Algal Types: Mat Forming GoldensTribonema

Vaucheria

Algal Types: Other Plankton

Ceratium

Peridinium

Euglena

Trachelomonas

Phacus

(Euglenoids)

(Dinoflagellates)

PART 3: THE ECOLOGICAL BASIS FOR ALGAL CONTROL

ALGAL ECOLOGYKey Processes Affecting Abundance

Growth Processes• Primary production – controlled by light

and nutrients, algal physiology• Heterotrophy – augments primary

production, dependent upon physiology and environmental conditions

• Release from sediment – recruitment from resting stages, related to turbulence, life strategies


Loss Processes

• Physiological mortality – inevitable but highly variable timing – many influences

• Grazing – complex algae-grazer interactions

• Sedimentation/burial – function of turbulence, sediment load, algal strategies

• Hydraulic washout/scouring – function of flow, velocity, circulation, and algal strategy


Annual variability in growth/loss factors in dimictic temperate lakes

• Winter –– Possible ice cover, reverse stratification

– Under ice circulation is an important factor

– Low light and temperature affect production

– Variable but generally moderate nutrient availability

– Possibly high organic content

– Grazer density usually low



• Spring/fall –– Isothermal and well-mixed

– Relatively high nutrient availability

– Light increases in spring, decreases in fall

– Temperature low to moderate

– Stratification setting (spring) or breaking down (fall)

– Grazer density in transition (low to high in spring, high to low in fall)



• Summer –– Potential stratification, even in shallow lakes

– Often have low nutrient availability

– Light limiting only with high algae or sediment levels

– Temperature vertically variable – highest near surface

– Vertical gradients of abiotic conditions and algae

– Grazer densities variable, often high unless fish predation is a major factor

ALGAL ECOLOGYPhytoplankton Succession - Winter

• Under ice, mainly cryptophytes, chrysophytes, diatoms, naked dinoflagellates

• Some non-nitrogen fixing blue-greens, but also possibly Aphanizomenon

ALGAL ECOLOGYPhytoplankton Succession – Early Spring

• Most lakes experience rapid increase in algal density

• Diatoms, cryptophytes, and chrysophytes tend to dominate

• Temperature is a primary control factor

ALGAL ECOLOGYPhytoplankton Succession – Late Spring

• Diatoms tend to dominate, often with Chlorococcalean greens and cryptophytes

• Chrysophyte blooms possible

• The later the spring maximum, the less likely that diatoms will dominate

• Overwintering benthic colonies may be recruited to the plankton community

ALGAL ECOLOGYPhytoplankton Succession – Late Spring

• Increasing light cues spring blooms where nutrients are available

• Grazing and algal settling increases during spring with rising water temperature

• Clear water phase often results from loss processes overshadowing growth in

late spring

ALGAL ECOLOGYPhytoplankton Succession – Early Summer• Increasing light and temperature• Nutrient availability may decrease as internal sources

are isolated by stratification - N, P, Si• Grazing, sinking and metabolism all increasing• Composition will depend upon resource gradients -

low N:P favors blue-green Nostocales and green Volvocales, high N:P favors other chlorophytes, chrysophytes and dinoflagellates

• N:P ratio at sediment:water interface can be more important than ratio in epilimnion

• High variability among lakes and within lakes among years

ALGAL ECOLOGYPhytoplankton Succession – Early Summer

• Greens increase, especially Volvocales and Chlorococcales

• Some blue-greens appear at increased density

ALGAL ECOLOGYPhytoplankton Succession – Early Summer

• May get metalimneticblooms of cryptophytes, chrysophytes, dinoflagellates or blue-greens, especially Planktothrix

ALGAL ECOLOGYPhytoplankton Succession – Late Summer

• High bloom potential -most often blue-greens, but also thecate dinoflagellates, large desmids

• Temperature is a major factor in blooms


• Nitrogen-fixing blue-greens especially common bloomers

• May get blooms of non-N fixing blue-greens if N is high

• May get population oscillations between N-fixers and non-N-fixers


• May also get green or blue-green mats floating to the surface

• Most often Cladophorales or Oscillatoriales

• Mats tend to start on bottom, floating to surface after trapping gases


• A variety of other algae may be mixed in, but dominance by one taxon or a few taxa is typical in fertile lakes

• Growth often nutrient limited, but dense surface growths may create light limitation below

• Grazing may be high, may be selective

ALGAL ECOLOGYPhytoplankton Succession - Autumn

• “Leftover” blue-greens may remain abundant well into autumn, exception is Cylindrospermopsiswhich often blooms late summer into mid-fall

• Metalimnetic growths often reach surface upon mixing

• Diatoms often assume dominance after turnover

ALGAL ECOLOGYPhytoplankton Succession - Autumn

• Desmids also respond positively to mixing

• As the water cools, the oil-laden Botryococcus may become abundant

• Nutrients tend to be abundant after turnover

ALGAL ECOLOGYPhytoplankton Succession - Notes

• Biomass can vary by 1000X from winter minimum to late summer maximum in temperate to polar waters

• Primary productivity and biomass may not correlate due to time lags, cell size and nutrient or light limitations

• Highest productivity normally at intermediate biomass (Chl a = 10 ug/L)

• High pH during blooms may trigger resting cyst formation

ALGAL ECOLOGYTrophic Gradients

• Based on decades of study, more P leads to more algae

• More algae leads to lower water clarity, but in a non-linear pattern

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Total Phosphorus vs. Secchi Disk Transparency


• As algal biomass rises, a greater % of that biomass is cyanobacteria. So more P = more algae + more cyanobacteria.

From Canfield et al. 1989 as reported in

Kalff 2002


• High P also leads to more cyanobacteria, from considerable empirical research. Key transition range is between 10 and 100 ug/L

(10 ug/L) (100 ug/L)From Watson et al. 1997 L&O 42(3): 487-495

Three step process:– Don’t lose your head– Get ducks in a row– Don’t bite off more than you can chew

PART 4: METHODS OF ALGAL CONTROL

Algal Control: Watershed Management

Understand the watershed and

manage it!

Algal Control: Watershed Management♦ Source controls• Banning certain high-impact actions• Best Management Practices for minimizing risk of

release

♦ Pollutant trapping• Detention• Infiltration• Uptake/treatment• Maintenance of facilities

Watershed management should be included in any successful long-term algal management plan

Algal Control: In-Lake ManagementData needs include:♦ Algal types and quantity (planktonic and benthic)♦ Water quality (nutrients, pH, temp., oxygen,

conductivity, and clarity over space and time)♦ Inflow and outflow sources and amounts, with

water quality assessment♦ Lake bathymetry (area, depth, volume)♦ Sediment features♦ Zooplankton and fish communities♦ Vascular plant assemblage All of which facilitate a hydrologic and nutrient

loading analysis and biological assessment essential to evaluating algal control options

Algal Control: In-Lake Management

In-lake detention and wetland

systems to limit nutrient inputs

Fulfilling a watershed

function in the lake

Algal Control: In-Lake ManagementDredging

♦ Dry (conventional)

♦ Wet (bucket/dragline)

♦ Hydraulic (piped)

♦ Removes nutrient reserves

♦ Removes “seed” bank

♦ Potential mat control


Harvesting

♦ Not feasible for many algal nuisances

♦ Possible to collect surface algal mats


Dilution and Flushing

♦ Add enough clean water to lower nutrient levels

♦ Add enough water of any quality to flush the lake fast enough to prevent blooms

Algal Control: In-Lake ManagementSelective withdrawal

♦ Often coupled with drawdown

♦ May require treatment of discharge

♦ Best if discharge prevents hypolimnetic anoxia

Algal Control: In-Lake ManagementDye addition

♦ Light limitation -not an algaecide

♦ May cause stratification in shallow lakes

♦ Will not prevent all growths, but colors water in an appealing manner

Algal Control: In-Lake ManagementSonication

♦ Disruption of cells with sound waves – may break cell wall or just dissociate plasma from wall

♦ Used in the lab to break up algal clumps

♦ Won’t eliminate nutrients, but may keep algae from growing where running all the time

♦ Varied algal susceptibility

Algal Control: In-Lake ManagementAlgaecides

♦ Relatively few active ingredients available

♦ Copper-based compounds are by far the most widely applied algaecides

♦ Peroxides gaining acceptance

♦ Some use of endothall

♦ Effectiveness and longevity are issues

Algal Control: In-Lake ManagementAbout copper

♦ Lyses cells, releases contents into water♦ Formulation affects time in solution and

effectiveness for certain types of algae♦ Possible toxicity to other aquatic organisms♦ Long term build up in sediment a concern, but no

proven major negative impacts♦ Resistance noted in multiple nuisance blue-greens

and greens♦ Usually applied to surface, but can be injected

deeper by hose♦ Less effective at colder temperatures

Algal Control: In-Lake ManagementAbout peroxide

♦ Lyses cells, but more effective on thin walled forms; less impact on most diatoms and greens

♦ Degrades to non-toxic components; adds oxygen to the water, may oxidize some of the compounds released during lysis

♦ Typically applied to surface, but may reach greater depth with adequate activity (slower release/reaction rate)

♦ No accumulation of unwanted contaminants in water or sediment

♦ Considerably more expensive than copper

Algal Control: In-Lake ManagementProper Use of Algaecides

♦ Prevents a bloom, not removes one♦ Must know when algal growth is accelerating♦ Must know enough about water chemistry to

determine most appropriate form of algaecide♦ May involve surface or shallow treatment where

nutrients are fueling expansion of small population♦ May require deep treatment where major migration

from sediment is occurring♦ May require repeated application, but at an

appropriate frequency - if that frequency becomes too high, recognize that the technique requires adjustment or will not be adequate for the long-term


Phosphorus inactivation - anti-fertilizer

treatments

Algal Control: In-Lake Management♦ Iron is the most

common natural binder, but does not hold P under anoxia

♦ Aluminum is the most common applied binder, multiple forms, permanent results, toxicity issues

♦ Calcium used in some high pH systems

♦ Used for water column or sediment P


Factors in Planning LakeTreatments:

• Existing P load, internal vs external

• Sources and inactivation needs – field and lab tests

• System bathymetry and hydrology

• Potential water chemistry alteration - pH, metals levels, oxygen concentration

• Potentially sensitive receptors - fish, zooplankton, macroinvertebrates, reptiles, amphibians, waterfowl

• Accumulated residues - quantity and quality


Lake Water Column Treatment:

• Doses vary - need 5-20 times TP conc.

• Can achieve >90% P removal, 60-80% more common

• Effects diminish over 3-5 flushings of the lake

Algal Control: In-Lake ManagementLake Sediment

Treatment:

• Can reduce longer-term P release

• Normally reacts with upper 2-4 inches of sediment

• Dose usually 25-100 g/m2 - should depend upon form in which P is bound in sediment

Algal Control: In-Lake ManagementSediment Dose Calculation

1. Oldest approach is to treat at maximum level that maintains pH >6; may need to do jar tests and repeat application over time to achieve goal

2. Alternative older method is to measure accumulated hypolimnetic P during stratification, or change in lake P over a dry period, or release from incubated sediment, translate into sediment P concentration (per square meter), then treat with dose at least 10 times that level on areal basis – buffer if necessary to control pH

3. Most current approach is to determine available P in sediment (Rydin and Welch method), treat aliquots of sediment slurry with aluminum, re-test for P availability, graph results and evaluate in context of target P level, diminishing returns, and cost; dose of 10 to 100 times available sediment P level expected

Algal Control: In-Lake ManagementMethods for Minimizing Aluminum Toxicity

Aluminum dose at any one time should be <10 mg/L, preferably <5 mg/L

When buffering alum with aluminate, use a 2:1 ratio of alum to aluminate, by volume, to avoid pH change (can be adjusted – 1.8 to 2.1 common)

Treat defined areas of the lake in a pattern that minimizes contiguous area treated at once (patchwork with adjacent blocks not treated sequentially)

Apply aluminum at enough depth to create a surface refuge (can even treat below thermocline)

Secchi Disk Transparency in Hamblin Pond, 1992-2003

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Treatment Date

SDT = 1.22 m

Hamblin Pond ExampleCape Cod, MA

P levels dramatically reduced, water clarity substantially increased

Long Pond ExampleCape Cod, MA

P levels dramatically reduced, but only for a year; clarity remains high through 3 years

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Algal Control: In-Lake ManagementSelective nutrient

addition♦ Addition of nutrients

(most likely N or Si) to shift ratio (N:P:Si) to favor more desirable algae

♦ Sometimes practiced in association with fertilization for fish production, but rare in water supplies or recreational lakes


Aeration/Mixing

Algal Control: In-Lake ManagementAeration/mixing can work by:

♦ Adding oxygen and facilitating P binding while minimizing release from sediments

♦ Physical mixing that disrupts growth cycles of some algae

♦ Alteration of pH and related water chemistry that favors less obnoxious algal forms

♦ Turbulence that neutralizes advantages conveyed by buoyancy mechanisms

♦ Creation of suitable zooplankton refuges and enhancement of grazing potential

Algal Control: In-Lake ManagementKey factors in aeration:

♦ Adding enough oxygen to counter the demand in the lake (usually about 75% from sediment) and distributing it where needed in the lake

♦ Maintaining oxygen levels suitable for target aquatic fauna (fish and invertebrates)

♦ Having enough of a P binder present to inactivate P in presence of oxygen

♦ Not breaking stratification if part of goal is to maintain natural summer layering of the lake

Algal Control: In-Lake ManagementDestratifying aeration:

Lake is mixed, top to bottom, input of oxygen comes from bubbles and interaction with lake surface

Algal Control: In-Lake ManagementNon-destratifying aeration:

Bottom layer is aerated, but top layer is unaffected; oxygen input comes bubbles (can be air or oxygen)

Algal Control: In-Lake ManagementKey factors in mixing:

♦ Moving enough water to prevent stagnation; may mix whole lake or just the top layer (if any)

♦ Fostering greater homogeneity in mixed zone and greater interaction with the atmosphere (oxygen and pH effects may be large)

♦ Getting enough motion or change in water quality to disrupt target algal species; moving algae to dark zone helps, but may be possible to disrupt with only surface layer mixing

Algal Control: In-Lake ManagementMixing systems:

Algal Control: In-Lake ManagementBarley straw as an algal

inhibitor

♦ Decay of barley straw appears to produce allelopathic substances

♦ Bacterial activity may also compete with algae for nutrients

♦ Limited success with an “unlicensed herbicide” in USA

Algal Control: In-Lake ManagementViral controls were

attempted without much success in the

1970s, but recent research suggests renewed potential.

Virus SG-3 in tests at

Purdue Univ.

Algal Control: In-Lake ManagementBacterial additives

♦ Many formulations, details proprietary

♦ Seem to focus on limiting N; competitive with algae

♦ Claims of sediment reduction

♦ Often paired with aeration/mixing

♦ Variable results, inadequate scientific documentation

Algal Control: In-Lake ManagementBiomanipulation -

altering fish and zooplankton

communities to reduce algal

biomass

Algal Control: In-Lake ManagementAlewife and other planktivore control - cascading effects

Algal Control: In-Lake Management“Rough” fish

removal -limiting nutrient

regeneration


Rooted plant assemblages as algal inhibitors

Algal Control: In-Lake ManagementTechniques that didn’t quite make the list

Algal Control: In-Lake ManagementTechniques for algal control with highest

probability of success♦ Watershed management (where external load is high)

♦ Phosphorus inactivation (for internal load or inflow)

♦ Aeration/mixing (possibly with dyes or bacteria)

♦ Dredging (where feasible, especially for mats)

♦ Algaecides (with proper timing, limited usage)

♦ Sonication (for susceptible algae, ltd nutrient control)

♦ Biomanipulation (but with high variability)

♦ Other techniques as scale and circumstances dictate (do not throw away any tool!)

The End

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