Global demand for food over the next 40 years is expected to double. Under present production technologies, meeting this demand and achieving global food security will require a doubling of water consumption levels. Meanwhile, the chemically fueled “Green Revolution” has run its course, leaving soil moistures depleted, and unclear climate change patterns threaten a looming agricultural water crisis. According to a study by McKinsey, a third of the world’s population lives in regions facing water shortages; by 2030 global water requirements could be as much as 40 percent higher than the currently accessible supply.
Ironically, 70 percent of our planet is covered with seas offering more economical protein production without depleting scarce water resources. However, wild fisheries around the world have reached or exceeded their maximum sustainable harvest so the United Nations is projecting a 40 million ton seafood shortage by 2030. Therefore, the $50 billion worldwide marine aquaculture industry - the deliberate farming of ocean species that provides half the world’s edible seafood - will continue to be the fastest growing form of food production in the world.
While global aquaculture has grown at a rate of about 8 percent over the past three decades, there are concerns that finfish farming may not be sustainable and its environmental impact is controversial. The cultivation of shellfish is recognized as the only form of aquaculture with no negative impact. Furthermore, in contrast to traditional shellfish farming in congested and increasingly polluted bays and estuaries, the cultivation of shellfish in pristine offshore waters is an emerging paradigm that is gaining recognition.
Bivalve shellfish are low-trophic (scientific-speak) because they are close to the plant base of the marine food web pyramid. Species feeding low in the food chain efficiently utilize natural resources. Each level up the food chain inflates costs related to the use of resources and the production of waste and the maintenance of water quality.
The phenomenon of upwelling elevates deep offshore nutrients to the sea surface for the propagation of phytoplankton: the foundation of the bountiful marine food web. Phytoplankton is the feedstock for filter-feeding bivalve shellfish. Unlike other forms of aquaculture, bivalve shellfish do not require costly external feed inputs fomenting the contentious sustainability issue.
Fast growing shellfish crops require little attention as they feed on drifting phytoplankton, are easily harvested and processed, and have a long shelf life for extended distribution. This is attracting the attention of private sector investors: no external feed, no negative environmental impact and harvest times less than a year reduces risk and generates a phenomenal return on investment.
The Prolific Pacific Oyster
Native to Japan, the Pacific oyster (Crassostrea gigas) has colonized worldwide as an aquaculture crop and now boasts the highest annual production of any freshwater or marine organism amounting to about 4.2 million metric tons and worth $3.5 billion. According to the Food and Agriculture Organization (FAO), Pacific oyster introductions have been recorded in: Ecuador, Belize, Costa Rica, Puerto Rico, the United States Virgin Islands, Brazil, Israel, Philippines, Malaysia, Romania Ukraine, Seychelles, Fiji, French Polynesia, Guam, Palau, Samoa, and Vanuatu.
The Pacific oyster was introduced to Northwest America in the 1920s and has grown into a $72 million industry. The Pacific oyster was then introduced to France in the 1970s with 562 tons of adult oysters from Canada and 5 billion spat brought in from Japan. By 2000 this alien shellfish represented 95% the country’s harvest amounting to 180,000 tons per annum. Today, the Pacific oyster in France generates $842 million annually and nearly all the harvest is consumed locally.
Globally, Pacific oysters have become the gold standard for replacing stocks of indigenous oysters that have been severely depleted by over-fishing or disease. The Pacific oyster with its large size, vitality, resilience to adverse conditions, resistance to deceases, rapid growth and reproductive capacity is ideal for cultivation. Thus, it is the most widely farmed oyster species in the world and has created a multi-billion dollar industry across the globe where none previously existed.
Cracking the Oyster Genome
All life forms are subject to the primacy of the genetic code (ACGT), which governs heritability, the ability to reproduce, and the propensity to evolve. As society faces the challenges of insufficient food production and environmental degradation, genetics will become a sustainable survival tool for humanity.
For as long as plants and animals have been domesticated, the tendency has been to select species for improvement like better growth, disease resistance, or any characteristic producing a better yield. With the advancement of shellfish hatchery technology over the past thirty years, the shellfish industry has employed these techniques to improve their crops.
On September 19th 2012, an international team of 75 researchers published the full genome of the Pacific oyster comprising 800 million DNA base pairs, including around 20,000 genes. A close look at the genes of the Pacific oyster immune system will reveal why it is largely resistant to plaguing diseases. Oysters can tolerate 100-degree water but also can withstand being covered with ice. They can survive out of water for weeks, if kept cool. They inhabit water where salinity varies seven-fold depending on season and weather. Now that disease-resistant genes have been identified, this could lead to a “molecular breeding” program in which oysters carrying them are raised in large numbers and used for greater yields in aquaculture.
The oyster genome may also shed light on the consequences of climate change, which could threaten marine organisms’ ability to form shells as the ocean becomes more acidic. Although oysters have high fertility, their offspring are very vulnerable and tend to die soon after birth. With the advent of ocean acidification, combined with the certitude of climate change, defined shifts in gene expression related to environmental stresses will provide transcriptional clues to the adaptations oyster employ for survival.
Stress response pathway enriched in the oyster genome, Nature. 2012 Sep 19
Pacific oyster genes are also specialists in inhibiting “apoptosis,” the process by which a cell kills itself in an orderly fashion once it suffers serious damage, gets old, weak or unneeded. Pacific oysters have 48 genes coding for proteins that inhibit apoptosis. The human genome has eight. Could the complexity of the oyster genome shed light for cracking the code for longevity?
With global population forecast to reach 9 billion by 2050, there will be many more mouths to feed and perhaps more if the oyster gene reveals the code for inhibiting apoptosis in humans. This “Next Big Thing” of sequencing the oyster gene will allow scientists and shellfish farmers to increase yields with higher survival rates to help meet the monumental challenge of feeding an aging and burgeoning population.