Transcript Undergrad Marine Conservation 2014

Harmful Algal Blooms (HABs)
Outline
I. Re-introduction to phytoplankton and HABs
II. Hypoxia and disruptive blooms
III. Toxic microalgae
IV. Regional Case Studies
“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
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
fishweb.ifas.ufl.edu
SeaWiFS/ORBIMAGE
www.surrey-arg.org.uk/
http://assets.nydailynews.com
“HAB” is also a messy word
• 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.edu
serc.carleton.edu
…and covers a wide taxonomic range
• Toxic or otherwise
harmful species
across many taxa
• Variety of physiology,
ecology, and
toxicology to
consider
• Beware of broad
explanations or
solutions for HABs
Falkowski et al 2004
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
Parsons et al. 2002
Anderson et al. 2002
Climate change likely to exacerbate HABs,
particularly cyanobacteria
• 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)
Paerl et al. 2011
Paerl et al. 2011
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
• 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
Longislandsoundstudy.net
Hypoxia and Fisheries Decline
• 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
Hugo Ahlenius, UNEP/GRID-Arendal
HABs can be dispruptive by excluding other
species
• Dense blooms due to eutrophication can shade
other important
Usac.org.uk
• Made worse by overfishing/loss of key grazers
• Coral reefs
News.fiu.org
• Macroalgae such as kelp
• 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)
…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
…or both!
• Aureococcus anophagefferens –
The Brown Tide
Newswise.com
• Blooms originated due to eutrophication
• Tiny cells were a poor food source for bay
scallops and grazers. Dense blooms outcompeted 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
MacIntyre et al 2004
Alternate Stable States
• 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
Stable State
Tipping Point
• Conditions shift to favor a new stable community
Two Stable States
• In reality, ecological
disturbance changes the
shape of the curves
• Process can be
irreversible on short timescales (human time)
www.theshallowresearcher.com
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
• 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
Comenius.susqu.edu
bewiki.kenyon.edu
With some important exceptions
Pseudo-nitzchia – the
toxic diatom
Microcystis – colony
forming cyanobacteria
that produces neuroand hepatotoxins
Prymnesium parvum – Small
prymnesiophyte that produces
parvotoxins, plagues aquaculture
systems
wikipedia
Gulfbase.org
Variety of toxins and diseases
Saxitoxins – Paralytic Shellfish Poisoning (PSP)
• Alexandrium (a dinoflagellate) and some cyanos
• Major problem in Northeast U.S. and Pacific
Northwest
Whoi.edu
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
All structures – Botana 2008
Pseudo-nitzschia
• Diatom that occurs in temperate
waters worldwide, dominant
community member
• Major bloom former in northern
Gulf of Mexico
•
AP
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)
Texas PWD
A persistent threat to fisheries and wildlife
• 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
AP
• 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
• 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)
Maria Faust - NMNH
Maria Faust - NMNH
University of Guam
Queen
Triggerfish
Parrotfish
Red Hind
Gastropods
Highest toxin concentrations,
most toxic congeners, mobile
vectors of an immobile toxin
source
White Grunt
Mesopredators/
large herbivores
Crustaceans Surgeonfish
Variety of primary
consumers
Epiphytic Gambierdiscus Inter- and intra-specific
variation in gambiertoxin
production and composition
Macroalgae
Turf
Algae
High variation in substrate types and selection
Biomagnification
Amberjack
Biotransformation
Increasing Ciguatoxicity
Complex trophic transfer of Ciguatera
Karenia brevis
• The infamous “red tide”
• Forms mono-specific blooms
in Gulf of Mexico, mostly in
Texas and Florida
noaa.gov
Hu et al. 2006
whoi.edu
• Human poisonings are rare,
usually from recreational
harvest in closed areas
• A major threat to Florida
wildlife
A wide-ranging threat
• 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)
Fowl River
ADPH
ADPH
Karenia red tides and endangerd/protected species
• 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
Florida FWC
• Some events (ex. 2005 bloom) killed
everything in some locations (invertebrates,
finfish, sea turtles, sharks)
• Risk to endemic species
Florida FWC
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
•
•
•
•
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?
WHOI
HAB Monitoring
cop.noaa.gov
baynews9.com
•
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
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
Agricultural nutrient reduction
•
Run off buffers on farms
•
Fertilization methods
Human Development
•
Impermeable surfaces
•
Waste water treatment
2.
3.
Less of this
Less of this
More of this!