Genetic regulation on carbon sequestration by mollusks
CARRIED OUT AT-
DEPT. OF BIOTECHNOLOGY
TECHNO INDIA UNIVERSITY,
SALT LAKE, SECTOR-V
3. The Greenhouse Effect
4. Carbon Cycle
5. Ocean Acidification
6. Review of literature
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.
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
George Waldbusser, Oregon State University, College of Earth, Ocean, and
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
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
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
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.
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
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
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
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.
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.
1. A. Whitman Miller mail, Amanda C. Reynolds, Cristina Sobrino, Gerhardt F. Riedel.
Shellfish Face Uncertain Future in High CO2 World: Influence of Acidification on
Oyster Larvae Calcification and Growth in Estuaries May 27, 2009DOI:
2. George Waldbusser. Ocean Acidification killing oysters by inhibiting shell formation
3. Guofan Zhang,Xiaodong Fang, Ximing Guo,Li Li,Ruibang Luo,Fei Xu, Pengcheng
Yang, Linlin Zhang,Xiaotong Wang, Haigang Qi,Zhiqiang Xiong,Huayong Que,Yinlong
Xie, Peter W. H. Holland,Jordi Paps, Yabing Zhu,Fucun Wu, Yuanxin
Chen,Jiafeng Wang, Chunfang Peng, Jie Meng,Lan Yang, Jun Liu,Bo Wen,Na Zhang, et
al. The oyster genome reveals stress adaptation and complexity of shell formation Nature
490, 49–54 (04 October 2012) doi:10.1038/nature11413.
4. James C. Orr, Victoria J. Fabry, Olivier Aumont, Laurent Bopp, Scott C. Doney, Richard
A. Feely, Anand Gnanadesikan, Nicolas Gruber, Akio Ishida, Fortunat Joos, Robert M.
Key, Keith Lindsay, Ernst Maier-Reimer, Richard Matear, Patrick Monfray, Anne
Mouchet, Raymond G. Najjar, Gian-Kasper Plattner, Keith B. Rodgers, Christopher L.
Sabine, Jorge L. Sarmiento, Reiner Schlitzer, Richard D. Slater, Ian J. Totterdell, Marie-
France Weirig, Yasuhiro Yamanaka & Andrew Yool . Anthropogenic ocean acidification
over the twenty-first century and its impact on calcifying organisms, Nature 437, 681-686
(29 September 2005) | doi:10.1038/nature04095.
5.Ko W. K. Ginger ,Chan B. S. Vera ,Dineshram R, Choi K. S. Dennis, Li J. Adela, Ziniu
Yu,Vengatesen Thiyagarajan. Larval and Post-Larval Stages of Pacific Oyster (Crassostrea
gigas) are Resistant to Elevated CO2 May 28,2013DOI: 10.1371/journal.pone.0064147.
6. Laura M. Parker 1, Pauline M. Ross, Wayne A. Connor, Hans O. Portner,Elliot Scanes
and John M. Wright. Predicting the Response of Molluscs to the Impact of Ocean
Acidification 2013, 2, 651-692; doi:10.3390/biology2020651.
7. Margaret Rudd,Kyle Jennette,Becky Duey,Arnel Selman and Terri J. Seron. The Effects of
Increased Acidity on the Shell Integrity and Body Size of C. Virginica: A Comparison of
Oyster Populations in Northeast Florida February 2013 | Vol. 25 Issue 2,2013 Journal of
8. Parker, L.M., Ross, P.M. and O'Connor, W.A. 2011 Population of Sydney rock oysters
(Saccostrea glomerata)vary in response to ocean acidification May 2011, Marine Biology