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. 2011Paerl 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!

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