identification, ecology and control of nuisance … · 2019. 5. 9. · algal problems...
TRANSCRIPT
IDENTIFICATION, ECOLOGY AND
CONTROL OF NUISANCE
FRESHWATER ALGAE
KENNETH J. WAGNER, Ph.D, CLM
WATER 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 PROBLEMS
Ecological 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 PROBLEMS
Aesthetic 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 PROBLEMS
Taste and Odor
• At sufficient density, all algae can produce taste and odor by virtue of organic content and decay
• Geosmin and Methylisoborneol (MIB) are the two most common T&O compounds, produced by cyanobacteria in water column or on bottom
• Additional compounds produced by golden algae and can impart cucumber, violet, spicy and fishy odors
• T&O presence does not guarantee toxicity, but with enough algae to cause T&O, toxicity should be checked
ALGAL PROBLEMS
Taste and OdorT&O by other algae
• Green algae, diatoms, dinoflagellates and euglenoids can produce fishy or septic odors 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
ALGAL PROBLEMS
Taste and Odor
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 PROBLEMS
Toxicity-Cyanotoxins• Cyanobacteria are the primary toxin threats to people in 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 2009) plus
NLA report indicate widespread occurrence of toxins but highly variable
concentrations, even within lakes, and rarely “high”.
• 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 PROBLEMS
Toxicity-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 PROBLEMS
Toxicity-Analytical Methods
Se
lec
tivit
y100
75
50
25
Bioassay(mouse)
mg ng pg
Sensitivity
MassSpec LC/MS
HPLC
ELISAPhosphatase Assay
ALGAL PROBLEMS
Toxicity- 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 PROBLEMS
Recommended Thresholds for Concern
WHO: Mod/High risk thresholds at >20,000 – 100,000 cells/mL, >10 - 50 ug/L chl-a, >10
- 20 ppb microcystin-LR
State thresholds in NEAPMS region:
• CT: Visible scums, 70,000 cells/mL, microcystin >15 ppb
• MA, RI: 70,000 cells/mL, visible scum, microcystin >14 ppb
• VT: Visible scums or mats present
• NH: Scum present with potential toxin producer >50% of cell count or 70,000
cells/mL
• ME, PA, NJ: Using WHO thresholds
• NY: Suspicious = unverified credible visual evidence Confirmed = BG chlorophyll a >
30 ug/l or MC-LR > 4 ug/L Confirmed with high toxins = MC-LR > 20 ug/L
ALGAL PROBLEMS
Recommended 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 Taxonomy
Just where to make the split between species or even genera is not always obvious
Layer cake
analogy from
Morales et al.
2002
Fragilaria
construens
Fragilaria
brevistriata
cruciate
biundular
elliptical
triradiate
linear
Algal TaxonomySplitters vs. Lumpers
• Lumping limits taxa, groups by “reliable”
differentiators (best if genetically based,
but was not always the case)
• Splitting proliferates taxa, separates
forms based on what may be genotypic or
phenotypic differences
• In characterizing environmental
conditions, splitting will be more useful
but requires more effort
Classification Features• Pigments
• Food storage
• Cell wall
• Flagella
o Cell structures
o Cell organization
Reproductive mode
Genetics
Culture response
Biochemistry
Cyanobacteria TaxonomyModern Classification of CyanobacteriaSubclass Synechococcophycideae
Order Synechococcales (e.g. Aphanocapsa, Coelosphaerium, Synechococcus,
Merismopedia, Snowella)
Order Pseudanabaenales (e.g. Pseudanabaena, Schizothrix, Spirulina, Planktolyngbya)
Subclass Oscillatoriophycideae
Order Chroococcales (e.g., Chroococcus, Microcystis)
Order Phormidiales (e.g., Arthrospira, Phormidium, Planktothrix)
Order Oscillatoriales (e.g., Lyngbya, Limnoraphis, Microseira, Oscillatoria)
Subclass Nostocophycideae
Order Nostocales (e.g., Nodularia, Anabaena, Dolichospermum, Aphanizomenon,
Cuspidothrix, Chrysosporum, Sphaerospermopsis, Trichormus, Anabaenopsis,
Cylindrospermum, Raphidiopsis, Gleotrichia, Rivularia, Scytonema, Tolypothrix, Stigonema)
Cyanobacteria Taxonomy
Some Major Findings of Polyphasic Analyses
• Distinction between coccoid and filamentous forms no longer
followed at the highest subclass level
• Division into subclasses based on thylakoid arrangement and
presence of differentiated cells (heterocytes/akinetes)
• Heterocytous cyanobacteria unified into one subclass
• Many genera shown to actually include more than one genus (e.g.
Anabaena, Aphanizomenon, Synechocystis, Phormidium, Lyngbya)
• Planktonic Anabaena and Aphanizomenon species closely related at
the generic level; continuum of genera in between
• Morphology based species concept for Microcystis not supported
Cyanobacteria Taxonomy
Sphaerospermopsis aphanizomenoides Chrysosporum ovalisporum
• Anabaena and Aphanizomenon appear to constitute a gradient of multiple genera
• Anabaena do not have aerotopes, do not float, and are benthic. Anabaena with
aerotopes split off mostly into Dolichospermum with a few intermediate genera
(Sphaerospermopsis, Chrysosporum, and Trichormus) based mostly on akinete and
heterocyte features
Dolichospermum Anabaena
Cyanobacteria Taxonomy
Cuspidothrix
Aphanizomenon
Filaments with long attenuated end cells split
from Aphanizomenon into Cuspidothrix
Separating Cyano Species
• Cell shape and Size
• Color
• Granulation
• Presence/Absence of Aerotopes
• Habitat• Cell Arrangement
• Mucilage features
• Trichome morphology
• Presence/Absence and Nature of
Sheath
• Presence/Absence of
Constrictions at Cross-walls
• Shape, Size and Location of
Heterocytes and Akinetes
• Motility
• End Cell Shape
Algal Taxonomy
Scenedesmus
Splitting by molecular analysis for other algal groups too!
• Green algae order Chlorococcales split into Chlorellales and Sphaeropleales
• Green algae genus Scenedesmus split into Scenedesmus, Acutodesmus and Desmodesmus
• Green algae genus Pediastrum split into at least 3 genera
Bottom line is that taxonomy is now based on molecular techniques more than visual
features, but we still have to do identification by eye. Molecular determination are therefore
walked back to find visual features we can use whenever possible, but it compromises
identification certainty.
DesmodesmusAcutodesmus
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-greensAphanizomenon
(Cuspidothrix)
Microcystis
Dolichospermum
(Anabaena)
Woronichinia
Algal Types: Planktonic Blue-greens
Planktothrix
(Oscillatoria)
Limnoraphis
(Lyngbya)
Planktolyngbya
(Lyngbya)
Algal Types: Planktonic Blue-greens
Gloeotrichia
Algal Types: Planktonic Blue-greens
Rhaphidiopsis
(Cylindrospermopsis)
•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 Greens
Lagerheimia
Oocystis
Order Chlorellales
(previously Chlorococcales)
Chlorella
Dictyosphaerium
Gloeocystis
Algal Types: Planktonic GreensPediastrum
Desmodesmus
(Scenedesmus)
Schroederia
Order Sphaeropleales
(previously Chlorococcales)
Pseudopediastrum
(Pediastrum)
Monactinus (Pediastrum)
Acutodesmus (Scenedesmus)
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 Greens
Zygnematales - Unbranched filaments, highly
gelatinous (slimy to the touch)
Mougeotia
Spirogyra
Zygnema
Mats trap
gases and
may float
to surface
Cladophorales - Large, multinucleate cells, reticulate chromatophores,
filamentous forms (coarser feel)
Pithophora
RhizocloniumCladophora
Algal Types: Mat Forming Greens
Algal Types: Mat Forming Greens
Hydrodictyon
Oedogonium
Bulbochaete
Algal Types: Planktonic Diatoms
Aulacoseira
(Melosira)
Asterionella
Cyclotella
Algal Types: Planktonic Diatoms
Fragilaria
Tabellaria
Nitzschia
Algal Types: Plankton Goldens
Synura
Prymnesium
Chrysosphaerella
Dinobryon
Algal Types: Mat Forming Goldens
Tribonema
Vaucheria
Algal Types: Other Plankton
Ceratium
Peridinium
Euglena
Trachelomonas
Phacus
Euglenoids
Dinoflagellates
Field vs. Microscope (courtesy of West Bishop of SePRO)
Algae name Phylum Characteristics
Lyngbya/
Plectonema
Mat forming
Cyanophyta
Filamentous, toxin/taste and odor
producer, mucilaginous, mat-former
Algae name Phylum Characteristics
Microcystis,
Dolichospermum,
Aphanizomenon,
Planktothrix
Planktonic
Cyanophyta
Colonial, filamentous, toxin producer,
mucilaginous, planktonic, scum-former
Algae name Phylum Characteristics
Euglena Euglenophyta Unicellular, potential toxin-producer,
planktonic, scum-former, flagellated
Algae name Phylum Characteristics
Spirogyra
“silk algae”
Chlorophyta Filamentous, mucilaginous, mat-former
(also Mougeotia and Zygnema)
Algae name Phylum Characteristics
Pithophora
“Horsehair algae”
Chlorophyta Filamentous, mat-former, branched,
also may get similar growths from
Cladophora and/or Rhizoclonium
Algae name Phylum Characteristics
Prymnesium parvum Haptophyta Unicellular, toxin producer, planktonic,
flagellated (rare in northeastern USA)
Algae name Phylum Characteristics
Nostoc Cyanophyta Colonial, soft gel, potential toxins
(like Anabaena in gelatin)
Algae name Phylum Characteristics
Didymosphenia
“Rock Snot”
Bacillariophyta Mucilaginous, mat-former, stalked, mainly
in flowing water, invasive
Algae name Phylum Characteristics
Chara
“Muskgrass”
Charophyta Plant-like, smelly, rough texture
(Nitella is similar, without smell)
PART 3: THE ECOLOGICAL
BASIS FOR ALGAL CONTROL
ALGAL ECOLOGY
Key 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
ALGAL ECOLOGY
Key Processes Affecting Abundance
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
ALGAL ECOLOGY
Key Processes Affecting Abundance
• Light – differential use of light by algae by virtue of different
pigments in cells
• Temperature – differentially affects metabolism of food storage
products
• pH – affects forms of carbon available, differential use of carbon
forms by algal groups
• Mixing – differential effects as some algae settle faster, some can
swim, some can float
• Grazing by zooplankton – some algae are more edible than others
ALGAL ECOLOGY
Phytoplankton Succession - Notes
• Biomass can vary by 1000X over time, function of growth and loss
processes interacting with other influences on algae
• 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 ECOLOGY
Trophic 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
0102030405060708090
100110120130140150160170180190200
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200
Ch
l (u
g/l)
TP (ug/l)
Total Phosphorus vs. Chlorophyll a
0
1
2
3
4
5
6
7
8
9
10
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 190 200S
DT
(m
)TP (ug/l)
Total Phosphorus vs. Secchi Disk Transparency
ALGAL ECOLOGY
Trophic Gradients
• As algal biomass
rises, a greater
% of that
biomass is
cyanobacteria.
So more P =
more algae +
more cyanos.From Canfield et al.
1989 as reported in
Kalff 2002
ALGAL ECOLOGY
Trophic Gradients
• 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
The End
QUESTIONS?
After that, we
might need
another one
of these…