health and hazards

sprocketflipOil and Offshore

Nov 8, 2013 (3 years and 7 months ago)

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Coral Reefs

health and hazards

Dr. Maia McGuire

University of
Florida/Sea Grant

Photo by Mike
White, FKNMS

What is a Coral?

Animal, vegetable or mineral?

It’s an animal which
may live with a
plant and makes a
mineral
-
based
skeleton.

Illustration by Geoff Kelley in
JEN Veron (2000)
Corals of
the World
, AIMS, Townsville

Coral structure


Individual animals are called
polyps


Several polyps make up a
colony


Corals are closely related to jellyfish
and sea anemones

they all contain
stinging cells called
nematocysts
.

Coral reefs


Reef
-
building corals require clear,
warm water


Shallow areas


Most reefs are between 26
°

N and S
latitude


There are corals found off Alaska and
other cold waters, but they grow very
slowly and do not form reefs

Symbiosis


Many hard and soft corals (and some
jellyfish and sea anemones) contain a
symbiotic single
-
celled brown
dinoflagellate

(algae) called
zooxanthellae


This is a
mutualistic

symbiosis


Bleaching

occurs when corals lose
their zooxanthellae

E.C. Peters

Coral Bleaching


Response to stress


Temperature


UV


Oxygen


Darkness


Sedimentation


Who initiates bleaching?


Can corals recover?

J. Hoggesteger

Patterns of bleaching


Geographically, often
begins in the Caribbean
and spreads northwards


Physically, there are often
bleached patches on the
sides of large coral heads
(especially
Montastraea
s)


Seasonal

usually in summer


ENSO

Zooxanthellae “clades”


Three groups of zooxanthellae have
been identified


Each group has different environmental
tolerances and is found in different
locations on the coral head

Photo by Scott R. Santos,
SUNY Buffalo

Where do zooxanthellae go?


“Free” zooxanthellae are rarely
found in plankton samples


May become benthic, sessile


May go into dormant stage



Presumably free zooxanthellae do
exist

Coral reproduction


Asexual reproduction
(usually in branching
corals; often storm
-
related)


Sexual reproduction


Hermaphroditic

or
gonochoristic


Self
-

or cross
-
fertilization


Internal or external fertilization


Brooders

or
broadcast spawners


Richard Fitzpatrick

Bette Willis in J.E.N.
Veron
(1987)
Corals of Australia
and the Indo
-
Pacific
.
Hawaii University Press


Brooders


Eggs develop into larvae
internally and may be
brooded for several weeks


Larvae are released, often
at night, often in response
to the lunar cycle


Brooders may have up to
12 reproductive cycles per
year

R. Hays Cummins

Coral larvae (
planulae
)


Swim using tiny hairs (
cilia
)


May already contain
zooxanthellae


Swim for days to weeks before
they
settle

and
metamorphose


Settlement may be in response
to
chemical cues

and may be
gregarious

Bob Richmond

NOAA

Status of coral reefs


Globally, coral reefs are generally in
decline


Increasing human population
(especially in coastal areas) increases
the impacts on coral reefs

Human impacts on coral
reefs


Overfishing


Sedimentation


Nutrient enrichment


Chemicals/oil


Physical damage
(anchors, fishing,
groundings)


Overfishing


Changes
trophic structure


Many large predators are no
longer present


Grazing fish species are
being collected as food fish


May allow algal overgrowth
of corals

NOAA

Nutrient enrichment


Nutrients are elements needed for
growth


If there are not enough of certain
types of nutrients, they are said to be
limiting nutrients


Most common limiting nutrients in the
marine environment are N and P

Nitrogen


Available in water as
nitrate, nitrite,
ammonium or organic
nitrogen (e.g. urea,
plant or animal tissues)

Phosphorus


Available in water as
dissolved inorganic
phosphate or organic
phosphorus (dissolved
or particulate)


How does nutrient
enrichment occur?


Septic tanks/sewage


Leaks


Pumping into the ocean


Fertilizer runoff


Agricultural


Homeowners


Golf courses

Effects of increasing
nutrients


Cause increase in
plant (algae)
growth


Macroalgae


Microalgae
(
phytoplankton
)

HAB’s/Red tides


Blooms of “harmful algae”


Pfisteria


Cause human health
problems


Cause fish kills


May be killing dolphins,
manatees

FMRI

Mote Marine

Lab


Cause decrease in coral
growth


Direct chemical
interference with skeleton
formation


Result of overshading by
algae

Effects of increased nutrients
on corals

Jennifer M. Smith

The nutrient
-
calcification
mystery


If zooxanthellae help corals calcify,
then why do enriched corals, which
contain more zooxanthellae, calcify
less?


Zooxanthellae are N
-
limited


“Excess” photosynthate is given to coral


If zooxanthellae grow, there is less
photosynthate to give to the corals

But….



There are more zooxanthellae per cm² of
coral, so the animal receives the same
amount of carbon…






=



Is the type of carbon compound different
in enriched and control corals?

Chemicals/oil


Non point
-
source pollution


51% of the oil entering the oceans is
from runoff


5% is from big spills


19% is from routine maintenance


2% is from offshore drilling


13% is from burning fuels (e.g. car exhaust)


10% is from natural seeps

Physical damage


Fishing techniques in the South
Pacific include dynamiting or
poisoning reefs to collect aquarium
fish for export


Boat anchors and boat/ship
groundings cause damage that can
take thousands of years to re
-
grow

Thomas Heeger,
Philippines

Natural impacts

Marine debris


Suffocation risk


Balloons/bags


Entanglement/entrapment


Fishing line/ropes


Old nets


Abandoned traps/pots

What can you do?


Reduce, reuse, recycle


Motor oil


Fishing line


Read and follow instructions
on chemicals, including
fertilizers


Fix automotive leaks

What does the future hold?

The answer is up to you…

1988

1998

USGS

USGS