THE CHEMISTRY OF CORAL BLEACHING

WHAT IS A CORAL?

• CORALS ARE MARINE INVERTEBRATES (ANIMALS)• THEY CAN TAKE MANY SHAPES!

• THEY USUALLY LIVE IN COLONIES OF TINY POLYPS• GENETICALLY IDENTICAL

• OF THE SAME PHYLUM AS JELLY FISH AND SEAANEMONE (CNIDARIA)• STINGING CELLS CALLED NEMATOCYSTS

• THERE ARE TWO TYPES OF CORALS• HERMATYPIC (HARD, STONY CORAL)• AHERMATYPIC (SOFT CORAL)

ACTIVITY: BUILDING A CORAL POLYP

• ONE 3" X 3" STICKY NOTE • PENCIL OR PEN • TRANSPARENT TAPE • SCISSORS • 1 EGG CARTON CUP (1/12 OF AN EGG CARTON)

STRUCTURAL AND CHEMICAL MAKE-UP

THE REEF BUILDERS• POLYPS BUILD HARD LIMESTONE CUPS AROUND

THEIR BASES• THE CUPS CEMENT TOGETHER TO MAKE A CORAL

COLONY• REEFS ARE MADE OF HUNDREDS OF HARD CORAL

COLONIES NEXT TO AND ON TOP OF EACH OTHER• REEF-BUILDING CORALS CAN ONLY SURVIVE IN FAIRLY

SHALLOW AREAS WHERE SUNLIGHT CAN PENETRATE• REFERRED TO AS THE TROPICAL RAINFOREST OF THE

OCEAN• REEFS ARE THE LARGEST STRUCTURES MADE BY

LIVING CREATURES!

WHY ARE CORAL REEFS IMPORTANT??

• USED FOR FOOD AND MEDICINE • ECONOMIC BENEFITS (TOURISM, JOBS AND FOOD)

- $375 BILLION A YEAR• BREEDING GROUNDS FOR MARINE ANIMALS

(FISH)• PROTECTS SHORES FROM WAVES AND STORMS• HOME & SHELTER TO 25% OF THE FISH IN THE

OCEAN• SOURCE OF NITROGEN AND OTHER NUTRIENTS

ESSENTIAL FOR THE FOOD CHAIN

PLANT PIGMENT IDENTIFICATION MINI-LAB

Adopted from : J. Chem. Educ. 2013, 90, 755−759

The whitening of corals due to the loss of their symbiotic zooxanthellae or the pigments associated with the algae.

WHERE IS THE PIGMENTATION IN CORAL?SYMBIOSIS

• MANY HARD AND SOFT CORALS (AND SOME JELLYFISH AND SEA ANEMONES) CONTAIN A SYMBIOTIC SINGLE-CELLED DINOFLAGELLATE (ALGAE) CALLED ZOOXANTHELLAE

• THIS IS A MUTUALISTIC SYMBIOSIS• ZOOXANTHELLAE (LIVING WITHIN

CORAL TISSUES) CONTAIN THE PIGMENTS THAT GIVE CORALS THEIR COLOR!

FROM THIS…

TO THIS…

DAY 2CORAL BLEACHING

FROM THIS…

TO THIS…

WHAT IS CORAL BLEACHING?

CORAL BLEACHING IS A STRESS RESPONSE IN CORAL REEFS THAT INVOLVES THE WHITENING OF CORALS DUE TO THE BREAKDOWN OR LOSS OF THEIR

SYMBIOTIC ZOOXANTHELLAE OR THE PIGMENTS ASSOCIATED WITH ALGAE

IMPORTANCE OF ZOOXANTHELLAE THE ZOOXANTHELLAE PROVIDE CORAL WITH THEIR BEAUTIFUL COLORS.

WITHOUT THE ALGAE CORALS ARE CLEAR OR WHITE PHENOMENON KNOWN AS CORAL BLEACHING

ZOOXANTHELLAE THAT LIVES IN CORAL TISSUE PROVIDE NUTRIENTS SUCH AS SUGARS AND OXYGEN THAT ARE ESSENTIAL FOR THE PRODUCTION OF CALCIUM CARBONATE (CORAL REEF SKELETON).

MORE THAN 50% OF THE CORALS’ NUTRIENTS ARE DERIVED FROM PHOTOSYNTHETIC PRODUCTS PRODUCED BY ZOOXANTHELLAE

PRODUCTION OF LARGE AMOUNTS OF MOLECULAR OXYGEN (O2) THAT ALLOWS FOR EFFICIENT RESPIRATION BY THE CORAL HELPS PREVENT INFECTION

PHOTOSYNTHESIS

Photosynthesis is the process by which plants, some bacteria, and some protezoans use the energy from sunlight to produce sugar. The conversion of unusable sunlight energy into usable chemical energy, is associated with the actions of the green pigment chlorophyll.

BALANCED PHOTOSYNTHESIS EQUATION

ENVIRONMENTAL FACTORS THAT CAUSE THE RELEASE

OF ZOOXANTHELLAE (SYMBIODINIUM)TEMPERATURE FLUCTUATION OF LOW AND HIGH SEA TEMPERATURE ACCOMPANYING INTENSE

UPWELLING WINTER: CHANGE FROM -3 C TO -5 C FOR 5 TO 10 DAYS SUMMER: CHANGE FROM 1 TO 2 C FOR 5 C TO 10 DAYS (MORE COMMON)

OCEAN ACIDIFICATIONABSORPTION OF CO2 BY SEAWATER IS A CHEMICAL REACTIONS THAT REDUCE THE PH OF SEAWATER CAUSING THE WATER TO BECOME MORE ACIDIC

UV RADIATION HIGH LEVELS OF PHOTOSYNTHESIS LEADS TO HIGH AMOUNTS OF NITRIC OXIDE

PRODUCTION BY ZOOXANTHELLAE SALINITY

ZOOXANTHELLAE ARE SENSITIVE TO LOW SALINITY DUE TO PRECIPITATION AND RUNOFF NEAR SHALLOW, CLEAR WATERS (NO DEEPER THAN 100M) WITH PLENTY OF SUNLIGHT.

OCEAN ACIDIFICATIONWHEN CO2 DISSOLVES IN SEAWATER, CARBONIC ACID IS PRODUCED VIA THE REACTION:

CO2 + H2O H2CO3

THIS CARBONIC ACID DISSOCIATES IN THE WATER, RELEASING HYDROGEN IONS AND BICARBONATE:

H2CO3 HCO3- + H+

ONE RESULT OF THE RELEASE OF HYDROGEN IONS IS THAT THEY COMBINE WITH ANY CARBONATE IONS IN THE WATER TO FORM BICARBONATE (A BASE)

CO32- + H+ HCO3

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CORALS AND CHEMISTRY MINI-LAB

TEMPERATURE

• CLIMATE CHANGE (GLOBAL WARMING) IS A MAJOR CONCERN:• IF TEMPERATURES CONTINUE TO INCREASE TO 1-2 C, FOR THE NEXT 20

YEARS THERE WILL BE MASS CORAL BLEACHING WORLDWIDE.• THE HIGH SEAWATER TEMPERATURE ELEVATION WILL AFFECT OVER 95%

OF THE SPECIES LIVING WITHIN THE CORAL AND LEAD SPECIES TO BECOME EXTIRPATED OR EXTINCT.

• BLEACHING EVENTS ALSO OCCUR DURING SUDDEN TEMPERATURE DROPS• -3 C TO –5 C FOR 5-10 DAYS), SEASONAL COLD-AIR OUTBREAKS

FORECASTING BLEACHING EVENTS MINI-LAB

DOES BLEACHING MEAN DEATH??IF THE STRESS-CAUSING BLEACHING IS NOT TOO SEVERE AND IF IT DECREASES IN TIME, THE AFFECTED CORALS USUALLY REGAIN THEIR SYMBIOTIC ALGAE WITHIN SEVERAL WEEKS OR A FEW MONTHS. IF ZOOXANTHELLAE LOSS IS PROLONGED. THUS, IF THE STRESS CONTINUES AND DEPLETED ZOOXANTHELLAE POPULATIONS DO NOT RECOVER, THE CORAL HOST EVENTUALLY DIES. 

PROTECT THE CORALS THAT PROTECT YOU!