Transcript Occurrence of Labyrinthula in Florida Bay

Threats to Marine Ecosystems
and Biodiversity
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General
Habitat Loss and Degradation
Resource Extraction
Species Invasions and Diseases
Climate Change
EXXON Valdez Oil Spill Trust Counciil; photolib.noaa.gov
Source: NOAA
General
• Human pressures on coastal resources are
compromising many of the ecosystem services
crucial to the well-being of coastal economies
and peoples
• The greatest threat to coastal systems is
development-related loss of habitats and
services
• Coastal ecosystems and islands face greater
numbers of threats than others, because
pressures are greater and because they are the
downstream recipients of degradation from afar
Habitat Loss and Degradation
• The most serious consequences of biodiversity
loss occur when changes are irreversible: e.g.
habitat loss, species extinctions, population
extirpations, regime shifts
• The most important driver behind these large
scale impacts on biodiversity is land conversion
(including coastal/marine habitat loss)
• The other drivers behind biodiversity loss differ
in various ecosystems, and include overexploitation, pollution, and climate change
Resource Extraction
• Many fisheries exceed
sustainable limits of use
• The removal of small-scale
heterogeneity associated with
the homogenization of habitats
is an important cause of the
loss of biodiversity
Source: T. Agardy
• Both over-exploitation beyond
sustainable levels and fishinginduced or coastal
development-related habitat
destruction are major issues
NOAA
Overfishing (= Intense Predation)
• The global marine catch has increased more than four
times in the past 40 years.
• Overfishing has pushed many fish populations into
steep declines. Catches are falling, even though fleets
are fishing harder, and spending more time, effort and
money than ever before.
• The U.N. Food and Agriculture Organization (FAO)
reports that seven of ten commercially targeted fish
stocks are either fully or heavily exploited (44
percent), overexploited (16 percent), depleted (6
percent), or slowly recovering from previous
overfishing (3 percent).
Pillaging the North Atlantic: species and the
year that > fishing effort = no increase in
yield: ‘overfishing!’
C= cod
H=haddock
P=plaice
R=redfish
Hk=hake
Hg=herring
Ocean Fisheries
• > 109 people (mostly developing nations)
depend upon marine fish for primary
source of protein
• a 40 y ‘fishing boom’ has now ended:
catch increasing steadily since 1950, but
since 1989 world catch has stayed the
same
• catch of ‘high value’ fish decreasing; catch
of low value fish increasing
Exploitation of global fisheries
Overfishing: Gear Impacts
• Trawlers often scrape the same area several
times each year. Sea-floor species can be
crushed and displaced, and the types and
availability of nutrients changed.
– Sediments stirred up by trawling can make
water a thousand times cloudier than normal,
limiting resettlement and feeding of plants
and animals
Trawling
Beam
trawlhow to
destroy
benthic
habitats
Effects of scallop dredging
on a gravel bottom:
George’s Bank: 84 m depth
Un-fished area
Fished area 500 m away
Frequency of trawling in some
representative areas
The rapid decline of the orange
roughy fishery
Red: est. biomass
Blue: catch
Overfishing: Continued
• There is great difficulty in sustaining global fisheries
production. In response to declines of big, slower
growing species, fishers have begun "fishing down
the food chain", targeting smaller species of less
value, but which can play critical roles in food webs.
• The most glaring crises of global fisheries include:
– over-capitalization of the industry which has led
to the buildup of excessive fishing fleets,
particularly of the larger-scale vessels catching too
many fish.
Overfishing: Continued
• Government subsidies enabled vessels to operate in
conditions that are uneconomic and environmentally
unsound. Fleets migrate globally to find more lucrative
fishing opportunities. Subsidies also supported a spree
in new vessel construction in recent years.
• Increased fishing pressure and competition among
fishing nations severely stresses fish stocks and the
marine environment. The use of unselective fishing
gear results in millions of tons of unwanted bycatch
being dumped overboard annually. Many millions of
other animals are incidentally killed by fishing fleets.
“Discards” in
the fishing
industry:
A.K.A.
‘BYCATCH’
Overfishing: Indirect Effects of Fishing
on Food Webs (bycatch cont.)
• Driftnets drowned by-catch
– With nearly invisible filament mesh, enormous
driftnets catch and hold fish by the gills.
• Driftnets also entangle and drown birds, sharks,
whales, and dolphins.
– The by- catch problem was so dire that the UN
banned large- scale driftnetting on the high seas in
1993.
• Smaller driftnets are still used in coastal waters,
including those of the U.S
The high seas
driftnet fishery
Overfishing: Impacts on Biodiversity
• At the genetic level, fishing can be an agent of directional
selection, affecting age distribution, age and length at maturity,
and growth rates.
• At the species level, fishing can alter species composition and
interactions among fished species and their prey.
• Fisheries often begin on large predators but their reduced
numbers may lead to increased numbers of prey species,
which may themselves become fished.
• Intense fishing can lead to dominance by r-selected species,
which often become major parts of mature fisheries. Other
species can also be affected; for example, fishery discards have
caused long-term changes in seabird species composition.
Overfishing: Indirect Effects
Overfishing: large marine herbivores
• Losses of herbivorous
green turtles and fishes
are thought to be partly
responsible for low levels
of seagrass grazing and
algal overgrowth of coral
reefs
Overfishing: A few success stories
• One success story,
Spanish mackerel in
the Gulf of Mexico are
no longer overfished
and, in fact, have
become a sustainable
fishery.
• Pompano are also
recovering in the Gulf
The three main “failings” of
fisheries
• Oceans are a ‘free for all’, a
‘hunter/gatherer’ philosophy: regulatory
bodies make weak commitments to
preserve stocks and then fail to follow
through
• Fishing fleets are subsidized by nations: $20
billion worldwide
• Conservation measures: there are few
closed seasons and limits to total catch
Exotic Species in the Oceans
• Invasion of marine areas by non-native species is a major
threat. The National Research Council's study
"Understanding Marine Biodiversity: A Research Agenda
for the Nation“ says it is one of the five most critical issues
facing marine life.
• The ecological consequences of invasions include:
– habitat loss and alteration
– altered food webs
– creation of novel and unnatural habitats that may be
colonized by other exotic species
– abnormally effective filtration of the water column
– hybridization with native species
– highly destructive predators; and
– introductions of pathogens and disease
Ecosystem characteristics that may
favor successful invasions
• The invaded habitat is climatically matched with the
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original habitat
The existing community is in an early successional state;
thus, there may be vacant niches, low diversity and absence
of similar species. This suggests a role for disturbance in the
success of invaders
Lack of natural enemies
Low connectance in local food webs
– lack of keystone species
Heavily polluted or disturbed environments
Possible characteristics of
successful invaders
• r-selected species with short generation times,
high fecundity, high population growth rates
– but some suggest a role for shifts between r
and K strategies
Non-native Pathways of
Introduction
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Aquaculture
Aquarium trade
Biological control
Boats and ships
Channels, canals, locks
Live bait
Nursery industry
Scientific research institutions, schools and public
aquariums
Recreational fisheries enhancement
Exotic Species: Ballast Water
T
• To maintain stability ships fill
ballast tanks with water. Large
ships often carry millions of
gallons of ballast water. As a
ship loads ballast it also loads
many organisms. Ballast water
is carried from one port to
another, where the water may
be discharged.
Exotic Species: Ballast Water (2)
• Perhaps 3,000 alien species per
day are transported around the
world. Not all survive, but some
do thrive in their new homes.
These invaders can cause
disruptions to ecosystems,
economies, and may carry
human diseases.
• What can we do?
• The Int’l Maritime Org. and the
U.S. government recommend
open ocean ballast water
exchange; however, very few
countries have adopted this.
Exotic Species: Nutria
• Nutria, natives of South America,
were introduced into Maryland
and La. in 1940’s & 50s for fur
production. Since the 1970s, there
has been a weak demand for fur
• Common nutria damage results
from burrows, which normally
extend 4 to 6 ft. into marshes
(but may be as long as 150 ft.).
• Damage first noted in the early
1990's, and $millions in damages
have accumulated even though
only 14% of the marsh canals
were heavily damaged.
Exotic species: Nutria (2)
• Nutria herbivory that can
have dramatic impacts on
coastal landscapes
• The nutria has been
implicated in large scale
losses of marsh in Maryland.
• What was once continuous
marshland (above) now
appears as fragmented
remnants
Solutions to the Nutria Problem
• From the Dallas Morning News on July 7, 1997
“A nutria a day helps keep erosion at bay:
Louisianians urged to eat rodents, save coast”
• "A young nutria tastes a lot like rabbit," Mr.
Windom (a La. Wildlife and Fisheries biologist)
said, adding that they can be fried, barbecued or
cooked numerous other ways.
Eutrophication
• Increased population density within watersheds has
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led to dramatic increases in nutrient inputs to coastal
waters
– increases range between 2 and 20 fold over
preindustrial age
Consequences of eutrophication
– elevated phytoplankton production coupled with
stratification of the water column leads to hypoxia
and anoxia
– fish kills, reduced light for seagrasses, increased
incidence of harmful algal blooms
Worldwide “Dead Zones”
Eutrophication: Harmful Algal
Blooms
Marine Diseases
Are much more prevalent in the world’s oceans in the
past few decades, and this has spurred a great deal of
research into the causes of these disease outbreaks.
Marine Diseases:Black Band Disease
and Coral Reef Losses
• Black band disease caused
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significant coral losses
– 1973-74 in Bermuda and
Florida Keys.
– 1978: Acropora corals in
Florida .
– 1985-86: in Florida Acropora.
The major component is a
filamentous cyanobacterium and
other microorganisms, including
sulfate-reducing bacteria and
heterotrophic bacteria
White Band Disease
• Gladfelter first reported tissue
slowly peeling off elkhorn and
staghorn corals at Tague Bay,
U.S. V. I.
– The loss of tissue resulted in a
band of white skeleton and this
was named white-band disease
(WBD).
– Unlike BBD, despite intensive
study, no microorganisms
could be found at the junction
of sloughing tissue and the
coral skeleton.
Additional coral diseases
 Dark Spots Disease
 Rapid Wasting Disease
 Red Band Disease
 White Plague
 Yellow Band Disease
Marine Diseases: The loss of
Diadema in the Caribbean
• Black urchin plague occurred
in D. antillarium in the
Caribbean and caused 98%
mortality within 10 days of
the first signs of the disease
in a new locality.
– Unlike other diseases,
which were localized, black
urchin plague spread from
Venezuela to Bermuda,
reducing populations to 17% of former levels.
Consequences of Diadema Dieoff
• Algal overgrowth of
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coral reefs
Loss reef
productivity & cover
Lost ecosystem
productivity
Marine Diseases-Seagrasses
• Labyrinthula is a slime mold
that could be responsible for
mass mortality of seagrass .
• In 1931, observers noticed
blackish-brown discolorations,
a loss of leaves and death of
the eelgrass along the U.S.
east coast
• y 1933, this "disease" had
decimated 90% of all
eelgrass in the North Atlantic.
Occurrence of Labyrinthula in
Florida Bay
Climate Change
• The geographically largest scale impacts to coastal
systems are caused by global climate change
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Warming of the world’s seas affects species by:
- Changing sea level faster than most can adapt;
- stressing temperature-sensitive organisms such as
corals;
- changing current patterns to interfere with
important processes like recruitment
• Global warming also changes the temperature and
salinity of estuarine and nearshore habitats and
exacerbates the problem of eutrophication
Climate Change and Disease
• Warming can increase the transmission rates of
pathogens and hasten the spread of many forms
of human and non-human disease.
• In most if not all cases, global climate change
impacts act in negative synergy with other
threats to marine organisms, and can be the
factor sending ecosystems over the threshold
levels for stability and productivity.
Methods to Conserve Marine
Biodiversity
1. Spatial management
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through zoning and
marine protected areas
Restoration
Fisheries Management
Integrated coastal zone
management
Regional & international
agreements/treaties
Kevin Frey © CBC-AMNH
West Andros Island, Bahamas
Source: T. Agardy
Spatial management through zoning
and marine protected areas
(MPAs)
Individual sites recognized for their
valuable services are sometimes protected
through zoning regulations and other
spatial management interventions such as
marine protected areas (MPAs)
Restoration
• Some key coastal habitats
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such as mangrove forests,
marshes, and seagrass
meadows can be, and are
being, restored
In general, however, the
costs of restoration far
exceed costs of protecting
the natural habitat
Fisheries Management
• Management of living marine resource use has
been practiced for several centuries
• Modern fisheries management has moved away
from stock-by-stock and single species
management to broader, ecosystem-based
management
• Fisheries management tools include quotas on
take, gear restrictions, access restrictions,
seasonal or other timing restrictions, and MPAs
Integrated coastal management
• Though coastal management is spreading
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around the world, management has not kept
pace with degradation
Specific approaches have shortcomings in
managing complex issues such as biodiversity
An integrated management response is needed
to conserve most aspects to biodiversity,
especially at the ecosystem level
Regional & intl. agreements/ treaties
• Most marine species cross the boundaries of
individual countries, making regulation beyond
the control and responsibility of any individual
nation (e.g., spiny lobsters and corals in the Fla.
Keys)
• International/Regional treaties provide a legal
framework for marine conservation action,
resource regulation, and scientific research on a
broad scale
Constraints to Marine Conservation
• Time Lags between perturbation to a system and
the eventual effects on the system mean that
anticipating effects is difficult
• Incomplete ecological understanding (and
corollary incomplete sociological understanding), can
be a major constraint in effective conservation
• Lack of funding (for research, for monitoring and
for enforcement of regulations) is a hindrance
• The lack of awareness and political will to
change policies is perhaps the biggest constraint
Conclusions
•Marine ecosystems are extraordinarily complex and
ecological understanding of marine ecosystems is
limited, but enough is known that better management
action can be taken
•Establishing adaptive management regimes will allow
us to gain important marine ecological information
quickly
•Integrated approaches and international cooperation
are needed to conserve marine ecosystems and marine
biodiversity