GENETIC REGULATION ON CARBON

SEQUESTRATION BY MOLLUSCS

SUBMITTED BY-

SHAYANTIKA MAJUMDER

CARRIED OUT AT-

DEPT. OF BIOTECHNOLOGY

SESSION-2013-2015

SUBMITTED ON-

18th November,2013.

TECHNO INDIA UNIVERSITY,

SALT LAKE, SECTOR-V

CONTENTS-

1. Abstract

2. Introduction

3. The Greenhouse Effect

4. Carbon Cycle

5. Ocean Acidification

6. Review of literature

7. Conclusion

8. References

ABSTRACT-

Ocean Acidification and the elevated level of CO2 impose a serious threat to the marine

biodiversity arising a question of their survival. Ocean acidification decreases the ph level and

availability of carbonate ions thus directly affecting the calcareous marine organisms. However

Oysters belonging to phylum Mollusca are seen to adapt souring of oceanic water and survives

as well. The question is how they are surviving in acidified waters instead of being affected by

ocean acidification. Several analysis were made and various techniques have been used to

sequence oyster genome revealing their adaptability and survival in CO2 driven acidified water.

INTRODUCTION –

Greenhouse Gas (sometimes abbreviated GHG) is a gas in an atmosphere that absorbs and emits

radiation within the thermal infrared range. Greenhouse gases are those that can absorb and emit

infrared radiation, but not radiation in or near the visible spectrum. In order, the most abundant

greenhouse gases in Earth's atmosphere are: Water vapour (H2O), Carbon dioxide (CO2),

Methane (CH4), Nitrous oxide (N2O), Ozone (O3) and CFCs. Greenhouse Gases causes rise in

Temperature, rise in Sea level and extreme Climatic change.

THE GREENHOUSE EFFECT

The most abundant greenhouse gas causing ill effects is Carbon dioxide (CO2).CO2 is believed

to be responsible for a significant rise in global temperature over the past several decades.

Global-scale climate modeling suggests that the temperature increase will continue, at least

over the next few hundred years, leading to glacial melting and rising sea levels. Increased

atmospheric CO2 also leads to ocean acidification, which will have drastic consequences for

marine ecosystems. As the global atmospheric emissions of carbon dioxide (CO2) and other

greenhouse gases continue to grow to record-setting levels, so do the demands for an efficient

and inexpensive carbon sequestration system.

More than half of the C02 emitted is removed from the atmosphere. The atmospheric lifetime of

CO2 is estimated of the order of 30–95 years. This figure accounts for CO2 molecules being

removed from the atmosphere by mixing into the ocean, photosynthesis, and other processes.

CARBON CYCLE –

The atmosphere is one the global CO2 reservoir. Oceans contain about 39,000 Gt of Carbon,

while soils, vegetation and detritus contain 2000 Gt Carbon and Carbonate rocks (limestone,

marble, chalk).CO2 exchange currently sequesters roughly half the annual anthropogenic global

CO2 emissions into oceans and soils.

THE GLOBAL CARBON CYCLE

OCEAN ACIDIFICATION –

Exchange of CO2 between the atmosphere and ocean is so rapid that the increase in the

atmospheric concentration of CO2 has effects on marine chemistry. Oceans absorb more than a

quarter of anthropogenic carbon dioxide(co2) emitted to the atmosphere, co2 dissolves in water

forms Carbonic acid(HCo3) and causes a drop of pH value and effects physiological,ecological

and evolutionary stages of marine biodiversity.

Higher CO2 concentrations lead to increase in the partial pressure of CO2 in the surface layers of

the ocean .The ph of the ocean’s surface water has already decreased by 0.1 units and model

calculations indicate that there may be a ph decrease by 0.3-0.4 units. The CO 2-driven ocean

acidification leads to a decrease in calcium carbonate (CaCO3) saturation state in the ocean and

has potential impacts on calcifiers like corals, algae, mollusks, coralline algae and foraminifera

leading to Shell dissolution and Ontogenic effects(early developmental and reproductive stages).

FUTURE CARBON EMISSION SCENARIO TO PREDICT HOW OCEAN PH WILLS CHANGE.AS EMISSIONS INCREASE, OCEANIC PH DECREASES AND CAUSES OCEAN ACIDIFICATION

REVIEW OF LITERATURE

ANTHROPOGENIC OCEAN ACIDIFICATION OVER THE 21st CENTURY AND ITS IMPACT ON CALCIFYING ORGANISMS-

Increasing atmospheric carbon dioxide (CO2) concentration reduces oceanic ph. and carbonate

ions concentration thus leads to calcium carbonate (CaCO3) saturation. It severely affects the

Benthic Biodiversity including tropical reef-building corals, cold-water corals, crusts coralline

algae, Halimeda, benthic mollusks, echinoderms, coccolithophores, foraminifera, pteropods, sea

grasses, jellyfishes, and fishes. Experimental studies suggests that if this trend continues then

marine organisms like corals and planktons will have difficulty in the formation of their CaCO3

skeletons. Evidences say that Southern Ocean surface waters will become under saturated with

respect to aragonite by the year 2050 and could extend the whole Southern ocean and the

subarctic Pacific Ocean by 2100.Potential changes in species distribution effects trophic level of

marine food web.

Due to repeated Ocean acidification there rises a question that if this trend continues to go on

then what is the chance of survival of the marine biodiversity, especially calcifiers, if so then

how and why. Thus significant studies and experimental analysis carried out by scientists and

marine biologists answered this question.

EFFECTS OF OCEAN ACIDIFICATION ON OYSTERS

OCEAN ACIDIFICATION KILLING OYSTER LARVAE BY INHIBITING SHELL FORMATION

George Waldbusser, Oregon State University, College of Earth, Ocean, and Atmospheric Sciences.

A study led by George Waldbusser, at Oregon State University answered the question that why

for past several years, the Pacific Northwest Oyster industry encountered high mortality rates of

the oyster larvae. George Waldbusser found out that increased CO2 level in ocean waters leads

to shell dissolution by zapping the energy reserves they need to build their shell and feeding

organ. The young oysters solely rely on the energy they derive from the egg as they do not have

yet developed their feeding organ. Under exposure to increased co2 acidified water, adult oysters

and bivalves grow slowly but the growth rate of the oyster larvae in its first two days of

development is not hampered. In this phase the oyster larvae needs a large amount of energy to

build its shell before the waters become more corrosive CaCO3 precipitation requires more

energy for higher rate of shell formation. But this study revealed that the more corrosive the

water is, more amount of energy is needed for shell formation and less energy is available for

growth and development. He even stated that the rate of co2 can be lessened by adding CaCO3

in oyster hatcheries.

Image shows 1-day old Pacific oyster larvae from the same parents, raised by the Taylors Shellfish Hatchery in natural waters of Dabob Bay, Wash. The larvae on the left were reared in favorable carbonate chemistry; on the right in unfavorable chemistry.

INFLUENCE OF ACIDIFICATION ON OYSTER LARVAE CALCIFICATION AND GROWTH IN ESTUARIES

A.Whitman Miller, et al. (2009)

Larvae of two Oyster species-Eastern oyster (Crassostrea virginica), and Suminoe oyster

(Crassostrea ariakensis) were collected to study the influence of co2 induced water on

calcification and growth of oysters. Species were grown under four pCO2 regimes, 280, 380, 560

and 800 µatm to stimulate atmospheric conditions in the pre-industrial era, present and future

concentrations in 50 and 100 years respectively. With the help of an automated negative

feedback control system the pCO2 was controlled and manipulations were made in the

experiment aquaria.

Larval growth and Calcification was measured using image analysis and chemical analysis of

calcium in the shells respectively. When pre-industrial and end of 21st century pCO2 treatments

were observed C. virginica showed 16%decrease in shell area and 42% reduction in calcium

content whereas, C. ariakensis showed no changes in growth rate or calcification. When

aragonite was under saturated both species showed net calcification and growth.

It was concluded from the study that temperate estuarine and coastal ecosystems poses a threat to

the growth and calcification of oysters due to increased CO2.

Effects of pCO2 treatment on apparent aragonite shell thickness for two oyster species.

Effects of pCO2 treatment on larval shell growth and calcification.

Effects of pCO2 treatment on cumulative size frequency of larval shells (µm2/shell) for two oyster species.

EFFECTS OF INCREASED ACIDITY ON THE SHELL INTEGRITY AND BODY SIZE OF C. Virginica: A Comparison of Oyster Populations in Northeast Florida

Margaret Rudd, et al. (2013)

This study was conducted in Florida to observe the effects of lower pH effects on Crassostrea

virginica (Atlantic Oysters)shell tolerance and to determine the level of shell dissolution due to

acidified water while the organism was not in the shell.

Materials and Methods- Two methods namely Field Method and Labarotary Method was used.

Field Method-C. Virginica live specimens were collected from Guana Tolomato Mantanzas

National Estuarine Research Reserve(GTM-NERR) and Saint Augustine Marina during

morning,afternoon and early evening and kept in buckets containing water from the area they

were collected.At each location salinity, pH level, and temperature of both water and air,mass

and length of the organism,mass of the tissue was recorded.

Labaratory Method-Fourteen living species were shucked and had their shells divided.One-half

shell from each individual was made free of detritus and other foreign materials and after

measuring their mass and length were stored in seven containers,each container containing two

specimens each.InstantOcean aquaria salt and laboratory grade distilled water (Aqua

Solutions)used to make artificial seawater were added to the containers to fully submerge the

shells.ph of seven containers were measured one of which seven was selected as the control.

Results-

Field Result- The tissue mass and the overall organism size did not differ in tissue mass or

organism size of NERR and Marina species.Marina species experiences a greater range of ph

than other calcifiers and have developed adaptations to these conditions.

Labaratory Result-Experimental species showed a degradation of ph but din’t affect the shell

integrity and developed adaptavity.

LARVAL AND POST LARVAL STAGES OF PACIFIC OYSTERS(Crassostrea gigas) ARE RESITANT TO ELEVATED CARBON DIOXIDE

Ko W. K. Ginger, et al. (2013)

Changes in oceanic ph poses serious threats to Pacific Oysters especially in their larval

stages.Multiple physiological studies and life stages and their effect on long term exposure to pH

8.1, 7.7 and 7.4 on larval shell growth,metamorphosis,respiration and filtration rates at the time

of metamorphosis along with the juvenile shell growth and structure of the C.gigas was

studied.pH din’t affect the growth rate and survival,between 8.1 to 7.7 the metabolic,feeding and

metamorphosis rates of larvae were similar.At pH 7.4,the larvae showed reduced weight specific

metabolic rate but were able to sustain post larval growth stages.Thus the analysis showed that

larval and post larval stages are resistant to elevated CO2 and decreased near-future pH scenarios

and are also adapted to the rapid pH changes in future.

OYESTER GENOME ADAPTATION AND SURVIVAL IN CO2 DRIVEN

ACIDIFIED WATER

Guofan Zhang, et al. (2012)

Studies showed that several gene families related to defense pathways including protein folding,

oxidation and anti-oxidation, apoptosis and immune responses are expanded in oysters. The

oyster genome contains 88 Heat Shock Protein70(HSP70)genes, which protects shells from heat

and other stresses. Cytochrome P450 and Multi copper oxidase gene families important for the

Biotransformation of xenobiotic and endobiotic chemicals and extracellular superoxide

dismutases important for defense against oxidative stress are present in oyster.

Further,48 genes coding for inhibitor of apoptosis(IAPs) indicating a powerful anti-apoptosis

system in oysters are also found. Genes encoding lectin-like proteins, including C-type lectin,

fibrinogen related protein and C1q domain containing proteins playing roles in innate immune

response in invertebrates are found in oysters. Thus presence of these genes in oysters makes

them able to survive in CO2 driven acidified waters even after being slightly affected in the early

stages of development and reproduction. The calcified shells of oyster provide critical protection

against predation and dessication in sessile marine animals like oyster. Molluscan shells contain

calcium carbonate crystals of either aragonite or calcite embedded in an elaborate organic

matrix.Chitin and silk protein provides matrix structure whereas acidic proteins controls the

growth andnucleation of calcium carbonate crystals.

POPULATION OF SYDNEY ROCK OYSTERS( Saccostrea

glomerata)VARY IN RESPONSE TO OCEAN ACIDIFICATION

L.M. Parker, et al. (2011)

Acute studies suggest that over the next century impacts of climatic changes on marine

biodiversity and ecosystem will be catastrophic. In this study it was seen that the ecologically

and economically important Sydney rock oyster Saccostrea glomerata, are resistant to ocean

acidification than wild species. When subjected to oceanic waters, it showed only 25% reduction

in shell growth whereas the wild species showed 64%reduction. Through this study it was seen

that among same species different sensitivities can be observed, which may be a solution for

aquaculture industries to overcome near-future effects of ocean acidification.

RESPONSE OF MOLLUSCS TO THE IMPACT OF OCEAN

ACIDIFICATION

Laura M. Parker, et al. (2013)

The following bar diagram shows the Percentage of studies which show negative effects of ocean

acidification on one or more processes for each mollusc group.

CONCLUSION-

The present study revealed that though oysters are affected by the CO2 driven ocean

acidification on the early stages of growth and development, it has the ability to adapt and

survive in acidified water. Thus the study of oyster genome concluded that oysters have certain

genes which make them susceptible to high concentration of carbon dioxide.

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Shellfish Face Uncertain Future in High CO2 World: Influence of Acidification on

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10.1371/journal.pone.0005661.

2. George Waldbusser. Ocean Acidification killing oysters by inhibiting shell formation

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