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Harmful Algal Blooms (HABs)
I. Re-introduction to phytoplankton and HABs
II. Hypoxia and disruptive blooms
III. Toxic microalgae
IV. Regional Case Studies
Outline
“Phytoplankton” is a messy word
• Literally = errant or wandering plant
• Often called “algae” or “microalgae”
• Any single-celled organism (usually protists or bacteria) in aquatic systems that performs photosynthesis
• They aren’t plants (but it helps to call them that)
http://www.artinsteel.co.uk/userimages/diatom01.jpg
http://farm3.static.flickr.com/ http://ux.brookdalecc.edu/staff/sandyhook/taxonomy
Phytoplankton are a Functional Group
• Grouped by what they do, not who they are• Ex. – Mammals are a taxonomic group, put different
function (grazers, scavengers, predators)
• Many problems with this grouping as well• Some live on the bottom – “microphytobenthos”• Some are predators and don’t always do
photosynthesis • Some are parasites • Incredible genetic and functional diversity
SeaWiFS/ORBIMAGE
www.surrey-arg.org.uk/fishweb.ifas.ufl.edu http://assets.nydailynews.com
Global Importance• 45-50% of global primary
productivity (fixing carbon into food)
• Production of oxygen
• Responsible for large fraction of global carbon burial (deep ocean)
• Base of almost every aquatic food web
• Role in C cycle gives them a key role in climate change
• Bloom = domination by one species/group or a rapid, dense proliferation of phytoplankton (a poor definition)
• “Harmful” for several possible reasons
• Produce toxins
• Hypoxia (low oxygen)
• Exclusion/Shading - disruptive to other phototrophs
• Physically harmful -obstruct fish gills, form large mats or foams
serc.carleton.eduserc.carleton.edu
“HAB” is also a messy word
Falkowski et al 2004
• Toxic or otherwise harmful species across many taxa
• Variety of physiology, ecology, and toxicology to consider
• Beware of broad explanations or solutions for HABs
…and covers a wide taxonomic range
HABs are not new…• Believed to be one or more of the Biblical
Seven Deadly Plagues (Ehrenkranz and Sampson, 2008)
• Red tides and toxic fish noted by Spanish explorers in 1600-1700s Florida (Tester and Steidinger 1997)
• Many human mortalities from HAB shellfish poisoning in last 300 years (Lewitus et al. 2012)
• Toxic bloom in California, 1961 inspired “The Birds” (Bargu et al. 2012)
• A local “jubilee” of seafood is a hypoxia event
• Many other historical accounts indicate hypoxia and toxic algae events
The Daily Telegraph
…but they are on the rise• Global increase in HABs was previously under debate• Strong scientific consensus that HABs are increasing due to anthropogenic influence (Heisler et al. 2008)
• Increased eutrophication (nutrient pollution)• Climate change• Invasive species
• Strong link between local nutrient pollution and increases in HABs
Anderson et al. 2002
Parsons et al. 2002
Climate change likely to exacerbate HABs, particularly cyanobacteria
Paerl et al. 2011
Paerl et al. 2011
• Phytoplankton growth generally increases with temperature
• Cyanobacteria (blue-green algae) more likely to dominate due to high termperature tolerance
• Many toxic cyanobacteria, also can be ecologically unfavorable (poor food source for higher trophic levels)
• Warming implicated in many cyanobacteria HAB problems world wide (Ex. Lake Taihu, China)
Invasions may also play a role in HAB expansion
• Some HABs linked to ballast water exchange (Hallegraeff, 1998) and known HAB species found in many ballast water surveys (Burkholder et al. 2007; Doblin et al. 2007)
• HABs that form resting stages (cysts) or can survive long periods of darkness are prime candidates for ballast water invasion
• Bio-fouling on ships may also be an important source of invasive species (Lopez-Rodas et al. 2010)
Safety4sea.com physicscentralcom
Hypoxia
Longislandsoundstudy.net
• Profound ecological and economic consequences
• Eutrophication implicated in the global rise in hypoxic zones (Diaz et al. 2001)
• Hypoxia formation actually relies on several factors:
• Physical processes (i.e. wind and mixing)
• Nutrient inputs to supply phytoplankton growth
• Sufficient phytoplankton growth and export to bottom waters
• Sufficient bacterial decomposition in bottom waters to deplete oxygen
Hypoxia and Fisheries Decline
Hugo Ahlenius, UNEP/GRID-Arendal
• In addition to sporadic fish kills, hypoxic zones drive down overall fisheries production (finfish and shellfish)
• Louisiana Dead Zone – Causes and estimated fisheries loss of 470 million pounds of seafood (Conservation and economic loss)
• Most costly effect of eutrophication/ over abundance of phytoplankton
www.cop.noaa.gov
HABs can be dispruptive by excluding other species
• Dense blooms due to eutrophication can shade other important
• Made worse by overfishing/loss of key grazers
• Coral reefs
• Macroalgae such as kelp
Usac.org.uk
• Particularly damaging to seagrass• Microalage and macroalgae have caused much of seagrass die-off (Duarte
1995; Hauxwll et al 2003) due to shading
• Eutrophication can shift overall production from benthos to water column. Loss of benthic production enhances resuspension making seagrass recovery harder (Olesen 1996)
News.fiu.org
…or by being a poor food source
• Some species are harmful by displacing better food sources
• Cyanobacteria lack essental fatty acids (e.g. sterols) give them poor nutritional quality for zooplankton (Martin-Creuzberg et al. 2008) and bivalves (Basen et al. 2012)
• Toxic cyanos such as Microcystis produce colonies near zooplankton and reduced grazing
Wikipedia
Wikipedia
Newswise.com
MacIntyre et al 2004
…or both!• Aureococcus anophagefferens –
The Brown Tide
• Blooms originated due to eutrophication
• Tiny cells were a poor food source for bay scallops and grazers. Dense blooms out-competed other phytoplankton
• Like seagrass problem, shifting biomass from benthos (microphytobenthos growing on bottom) to water column
• Destablizes sediment, more resuspension
• Dark environment perfect of Aureococcus (adapted to low light)
• Persistent blooms wiped out bay scallop industry in New York
Alternate Stable States
www.theshallowresearcher.com
Stable State Tipping Point
Two Stable States
• In reality, ecological disturbance changes the shape of the curves
• Process can be irreversible on short time-scales (human time)
• In a stable state, ecosystem can receive some amount of disturbance, but will tend to return to natural state
• If disturbed enough, dominance of stable state species is lost
• Conditions shift to favor a new stable community
Toxin-producing HABs• Large mortalities of fish or shellfish
• Mortalities of wildlife such as birds or marine mammals
• Direct toxic effects to humans
• Human poisonings through contaminated seafood
• Large economic impacts due to monitoring, medical costs, fisheries closures
• Challenge: Aside from understanding HAB ecology and toxin production, must also assess trophic transfer, biotransfomation , and pharmacology of toxins
ADPH
Most toxin producers are dinoflagellates
bewiki.kenyon.eduComenius.susqu.edu
• Most ecological, human health, and economic costs are due to dinoflagellate HABs
• Pose unique challenges for HAB research
• They are mixotrophic (act as plants and animals), more difficult to describe ecology
• Some cause harm at very low concentrations, hard to detect
• They have enormous genomes, difficult for full sequencing
With some important exceptions
wikipedia
Gulfbase.org
Pseudo-nitzchia – the toxic diatom
Microcystis – colony forming cyanobacteria that produces neuro- and hepatotoxins
Prymnesium parvum – Small prymnesiophyte that produces parvotoxins, plagues aquaculture systems
Variety of toxins and diseasesSaxitoxins – Paralytic Shellfish Poisoning (PSP)• Alexandrium (a dinoflagellate) and some cyanos• Major problem in Northeast U.S. and Pacific
Northwest
Brevetoxins – Neurotoxic Shellfish Poisoning (NSP) • Caused by Karenia (dino)• Major problem for wildlife, tourism, and fisheries in
Florida
Ciguatoxins – Ciguatera Fish Poisoning (CFP)• Gambierdiscus (dino) • Only in tropics, poorly understood• Most common disease due to HABs, 2nd most
common illness due to fish
Domoic acid – Amnesic Shellfish Poisoning (ASP)• Pseudo-nitzschia (diatom) • Global problem for wildlife and shellfish
Okadaic acid – Diarrheic Shellfish Poisoning (DSP)• Emerging problem in Gulf of Mexico and Pacific NW
Whoi.edu
All structures – Botana 2008
Pseudo-nitzschia
AP
Texas PWD
• Diatom that occurs in temperate waters worldwide, dominant community member
• Major bloom former in northern Gulf of Mexico
• Produces domoic acid, accumulates in prey species and poisons their consumers.
• Similarities in bloom conditions• Pulses of nutrients• Mixing• Upwelling, estuaries, oceanic
fronts
• Appears to have a ruderal (weedy) growth strategy (MacIntyre et al. 2011)
A persistent threat to fisheries and wildlife
AP
• First human poisonings raise attention• 1987, Prince Edward Island, CA• 3 killed, ~10 brain damaged, ~100 sickened• Consumption of domoic acid contaminated blue
mussels• Causes many shellfish closures in Pacific
Northwest
• Poisonings since in wildlife• Frequent sea lion mortalities
(Scholin et al. 200)• Bird mortalities (Work et al. 1993)• Possible whale and dolphin
illnesses (Twiner et al. 2009; Fire et al. 2011
• Found in commercial fisheries in GOM (Liefer et al. 2013; Del Rio et al. 2012)
Liefer et al. 2013
Gambierdiscus and Ciguatera
Maria Faust - NMNH
University of Guam
Maria Faust - NMNH
• Ciguatera Fish Poisoning (CFP) is the most common illness due to phycotoxins; 25,000 – 500,000 cases per year.
• Seafood containing ciguatoxins (CTXs), lipophilic Na-channel activating toxins
• Ciguatoxins originate from gambiertoxins, produced by species of Gambierdiscus, benthic dinoflagellate
• Common in shallow tropics. Florida Keys, Hawaii, Puerto Rico, and USVI
• Endemic in regions like USVI, Puerto Rico, parts of South Pacific (>5% of population likely has had it)
Complex trophic transfer of Ciguatera
Inter- and intra-specific variation in gambiertoxin production and composition
High variation in substrate types and selection
Variety of primary consumers
Mesopredators/ large herbivores
Highest toxin concentrations, most toxic congeners, mobile vectors of an immobile toxin source
Amberjack
Queen Triggerfish Red Hind White Grunt
Parrotfish Gastropods Crustaceans Surgeonfish
Macroalgae Turf Algae
Epiphytic Gambierdiscus
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Karenia brevis
noaa.gov
whoi.edu
• The infamous “red tide”
• Forms mono-specific blooms in Gulf of Mexico, mostly in Texas and Florida
• Human poisonings are rare, usually from recreational harvest in closed areas
• A major threat to Florida wildlife
Hu et al. 2006
• One of the only HABs directly toxic to humans – waves will break Karenia cells, toxin gets in the air. Causes respiratory problems in humans
• Toxin has caused large fish kills in western Gulf of Mexico
• Widespread 2005 bloom killed things at all trophic levels (Landsber et al. 2009)
A wide-ranging threat
ADPH
ADPHFowl River
• Several large dolphin die-offs (Twiner et al. 2012 and others)
• Dolphins consume small planktivorous fish (like menhaden) that graze on toxic bloom
• Can be very quick process
• Manatees (Bossart et al.1998), including 829 last year
• Florida manatee population already highly endangered and declining
• Est. population = <10,000
• Some events (ex. 2005 bloom) killed everything in some locations (invertebrates, finfish, sea turtles, sharks)
• Risk to endemic species
Florida FWC
Florida FWC
Karenia red tides and endangerd/protected species
Conservation Implications of HABs
• Impact of hypoxia and toxic blooms to already dwindling fisheries
• Shifts in sensitive ecosystems (ex. Seagrass, corals) to algal dominance due to eutrophication and reduction of grazing fish
• Threats to endangered/protected species, particularly those endemic to a small region (ex. Florida Manatees)
• Loss of Confidence?• Effect on conservation interest as seafood resources are
lost• Effect on conservation interest if eco-tourism is lost
Coping with HABs• Reminder: HABs and hypoxic zones have occurred naturally,
inherent aspect of many ecosystems
• Most of the HAB problems are highly complex• Phytoplankton communities are incredibly diverse and
unstable• A wide variety of nutrient sources for eutrophication• Toxin production varies with conditions • Some toxins must accumulate and transform to have
impacts
• Three key approaches to HABs (and most conservation issues)• Mitigation• Monitoring• Prevention
HAB Mitigation
WHOI
• Biological Treatments• Macroalgae extracts (allelopathy)
• Chemical Treatments• Clays• Copper sulfate
• Physical disturbance• Boat mixing• Turbines
• All of these options and other proposed ones have key drawbacks• Ecosystem effect difficult to
predict• Costly • Long-term effectiveness?
HAB Monitoring • The only option for many HABs
• Dinophysis -> DSP at low abundances• Gambierdiscus -> Ciguatera while
being rare and not blooming
• Monitoring and seafood safety• No known illnesses from Amnesic
Shellfish Poisoning since 1987• Automated monitoring prevented a DSP
outbreak in Texas during a shellfish festival (2011)
• Challenges• Better understanding of ecology, toxin
production • Require highly skilled labor, technology• Blooms are “cryptic”• Expanding monitoring in undeveloped
nations
cop.noaa.gov
baynews9.com
HAB Prevention • “An ounce of prevention is worth a pound of
cure” – especially true for HABs
• Addressing the key causes• Eutrophication• Climate Change• Species Invasion
• Reducing eutrophication seems most likely to happen and most effective
1. Maintaining natural filters• Wetlands• Dissipating river outputs
2. Agricultural nutrient reduction • Run off buffers on farms• Fertilization methods
3. Human Development• Impermeable surfaces• Waste water treatment
Less of this
More of this!
Less of this