**1. Introduction**

Chemodiversity usually refers to small molecules that have a signaling (offensive or defensive) function, sometimes protective. This leaves aside larger molecules that are purely structural and those that participate in essential metabolic functions, and make up the bulk of the organic body mass of living organisms.

From cyanobacteria and bacteria to the largest metazoans, chemistry is the preferred mode of aquatic communication, thanks to the extraordinary solvation properties of water. Bacteria create biofilms inside which they communicate using their own chemical repertoire before colonizing new media, substrates or organisms. Microalgae form blooms which are maintained by releasing semiochemicals for cell-cell recognition. Fish rely on their extraordinary sense of smell to hunt or to migrate to some specific breeding spot. The extraordinary biodiversity of coral reefs is maintained by a highly complex chemical network of toxins and pheromones, some soluble, some dispersed with a mucus carrier or surface-coated. But not only: the amazing colors used for warning or for camouflage, the bioluminescence used in the dark correspond to very sophisticated assemblages of pigments, small metabolites or proteins, each organism having its own strategy to be visually recognized or to blend into the background.

Humans have only recently been aware of the extraordinary potential marine molecules for the design of new drugs, cosmetics and nutraceutics. Well over 20000 natural molecules have been studied so far, and several have responded to the need for novel anticancer, antibiotic, anti-inflammatory or anti-pain agents etc. The necessity to preserve this exceptional resource, however, has only manifested itself in the delineation of protected areas and in the imple‐ mentation of codes of good practices regarding non-destructive boating and durable sampling protocols.

© 2014 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Over the last three decades, warning messages have been sent to the community about the destructive consequences worldwide economic development will have on biodiversity, both terrestrial and marine, during the 21st century. Direct impacts are caused by overexploitation and mismanagement of natural resources and improper recycling and disposal of waste products. Indirect impacts are caused by the accelerating volatilization of greenhouse mole‐ cules and their accumulation in the atmosphere where they may undergo undesirable speciation. Restitution of sulfur emissions to land may cause acidic rains and transfer of carboncontaining emissions to seawater increases its acidity, both leading to biodiversity destructive scenarios. Not to mention the release of man-made (synthetic) molecules, some of which like CFCs destroy the anti-UV ozone shield, others like PCBs accumulating along food chains and eventually killing top consumers. Synthetic molecules may respond to specific needs and criteria, but they will never replace natural molecules, in the same way as genetically trans‐ formed organisms will never replace wildlife diversity. Moreover, freak biological or chemical species should be eliminated safely once the purpose for which they were created has been fulfilled.

had been available to combine with hydrogen, yet early planet Earth was most likely very hot and dry, precluding life and any of the complex chemistries it produces. This characterized the Hadean, the first geologic eon (4.6 to 4.0 billion years until conflicting evidences such as the presence of high d18O (oxygen isotopic ratios) in zircons tentatively dated as early as 4.4 billion years led to a reassessment of the transition between the "molten" planet (and formation of the moon) and the "solid" planet with a solid crust, a low temperature, and an atmosphere of sorts, and the possible presence of liquid water. As well as this "cool early earth" hypothesis [1], a partial explanation about the formation of oceans is that asteroids and perhaps comets carrying huge amounts of ice collided with our planet, adding to the putative *de novo* conden‐ sation into water during the degassing of rocks of the cooling planet. In the primitive atmos‐ phere, heavier carbon dioxide became partly quenched by dissolving in oceanic waters, and

Marine Biodiversity and Chemodiversity — The Treasure Troves of the Future

http://dx.doi.org/10.5772/57394

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Any life form necessitates the capacity to harvest energy for its own benefit, to manage chemical reactions within molecular boundaries that define it as an entity distinct from the

Irrespective of when the right conditions were first met for life to emerge, a small set of small organic molecules (reactants) is a prerequisite for the abiotic generation of life-essential molecules, in the presence of water and of some catalytic trigger, and later of thermodynam‐

Different approaches have attempted to address the question of the chemical origin of life, leading to apparently conflicting conclusions: the "prebiotic soup theory" and the "pioneer organism theory", fueling heated debate among specialists, and also reflecting the uncertainties that still remain on the greatest mystery in science. The following paragraph attempts to follow

The prebiotic soup theory stems from the early experiments of Stanly Miller and Harold Urey [2] which led to the condensation within days of a suite of five amino acids by exposing a sterile mixture of methane (CH4), ammonia (NH3), carbon monoxide (CO) and hydrogen (H2) - i.e. the "primitive gases", to a constant flux of hot water (H2O), while discharging electric sparks (to simulate thunder) into the gas mixture. New species such as hydrogen cyanide (HCN), formaldehyde (HCHO) and reactive intermediates (acetylene, cyanoacetylene etc.) are formed in one-step, while amino acids and other biomolecules are formed from these reactants under

Some 50 years later, Bada and collaborators (in [3]) reanalyzed archived samples of Stanly Miller's experiments in which the gaseous mixture included hydrogen sulphide (H2S), methane (CH4), ammonia (NH3), and carbon dioxide (CO2). In the case of this experiment (unreported by Miller at the time), no less than 27 compounds, including the 20 "regular" amino acids and 3 new ones were found. Specifically, the presence of hydrogen sulphide and carbon

partly trapped under plate tectonic movements.

ically favorable conditions for polymers to be built.

*2.2.1. The Miller-Urey laboratory experiments*

reducing conditions (Fig. 1), i.e. the Strecker synthesis.

**2.2. The chemical origin of life on earth — Chemodiversity goes organic**

environment, i.e. *self* vs. *non-self*, and to have the potential to replicate itself.

the most generally accepted views and the most plausible scenario.

To-date, very little is said or written on the fate of natural chemodiversity within the context of local or general biodiversity collapse, both terrestrial and marine. After a brief historical account of the intricate connections between chemodiversity and biodiversity since life appeared on our planet, this chapter attempts to demonstrate that natural molecular diversity is a treasure to preserve for future generations, using a series of marine examples.
