Photosynthesis in the oceans

Like all matter, carbon can neither be created nor destroyed it can just be moved from one place to another. The carbon cycle depicts the various places where carbon can be found. Carbon occurs in the atmosphere, in the ocean, in plants and animals, and in fossil fuels. Carbon can be moved from the atmosphere into either producers (through the process of photosynthesis) or the ocean (through the process of diffusion). Some producers will become fossil fuels, and some will be eaten by either consumers or decomposers. The carbon is returned to the atmosphere when consumers respire, when fossil fuels are burned, and when plants are burned in a fire. The amount of carbon in the atmosphere can be changed by increasing or decreasing rates of photosynthesis, use of fossil fuels, and number of fires. 

As shown in Fig. 10-13, there is also a flux of O2 produced during net photosynthesis from the ocean to the atmosphere and an export flux of particulate and dissolved organic matter out of the euphotic zone. For a steady-state system, new production should equal the flux of O2 to the atmosphere and the export of organic carbon (Eppley and Peterson, 1979) (when all are expressed in the same units, e.g., moles of carbon). Such an ideal state probably rarely exists because the euphotic zone is a dynamic place. Unfortunately, there have been no studies where all three fluxes were measured at the same time. Part of the difficulty is that each flux needs to be integrated over different time scales. The oxygen flux approach has been applied in the subarctic north Pacific (Emerson et al, 1991) and subtropical Pacific (Emerson et al, 1995, 1997) and Atlantic (Jenkins and Goldman, 1985). The organic carbon export approach has... 

To understand the distribution and pathways of organic material in the ocean the key question is "What happens to that 99% of the phytoplankton biomass that is remineralized between photosynthesis and burial "... 

Because of the role these algae play in the oceans biological productivity and their impacts on climate due to the removal of carbon dioxide, satellite sensors have been employed to measure the chlorophyll a contents in oceans, lakes, and seas to indicate the distribution and abundance of biomass production in these water bodies. Detection is set at the specific reflectance and absorption wavelengths of the light from the upper layer of the ocean where photosynthesis occurs. 

Likewise, the ability of the oceans to take in atmospheric carbon could be increased. Algae, plankton, and other organisms carry on photosynthesis as do green plants on land They take in carbon dioxide and release oxygen. In fact, about half of the oxygen we breathe is produced by these organisms. Experiments to fertilize plankton growth in the oceans have already been completed, but the method has not yet been implemented as a way to increase the ocean s carbon contents. 

It is a matter of conjecture as to whether sunlight was involved in the buildup of early organic molecules which eventually formed DNA, RNA and proteins. Photosynthetic bacteria may well have been the very first independent life forms, and from the time of the growth of green plants the atmosphere must have become gradually richer in oxygen, since it appears as a byproduct in the major process of photosynthesis. It is generally accepted that early life developed in the oceans, and it may be surmised that its eventual development on land was made possible by the formation of the protective ozone layer in the upper atmosphere. 

Finally, it must be realized that photosynthesis is not the sole prerogative of the higher plants. More than half the photosynthesis on the earth s surface is carried, out in the oceans by phytoplankton. 

For example, in the carbon cycle consider the balance between terrestrial photosynthesis and respiration-decay. If the respiration and decay flux to the atmosphere were doubled (perhaps by a temperature increase) from about 5200 x 1012 to 10,400 x 1012 moles y-l, and photosynthesis remained constant, the CO2 content of the atmosphere would be doubled in about 12 years. If the reverse occurred, and photosynthesis were doubled, while respiration and decay remained constant, the CO2 content of the atmosphere would be halved in about the same time. An effective and rapid feedback mechanism is necessary to prevent such excursions, although they have occurred in the geologic past. On a short time scale (hundreds of years or less), the feedbacks involve the ocean and terrestrial biota. As was shown in Chapter 4, an increase in atmospheric CO2 leads to an increase in the uptake of CO2 in the ocean. Also, an initial increase in atmospheric CO2 could lead to fertilization of those terrestrial plants which are not nutrient limited, provided there is sufficient water, removal of CO2, and growth of the terrestrial biosphere. Thus, both of the aforementioned processes are feedback mechanisms that can operate in a positive or negative sense. An increased rate of photosynthesis would deplete atmospheric CO2, which would in turn decrease photosynthesis and increase the oceanic evasion rate of CO2, leading to a rise in atmospheric CO2 content. More will be said later about feedback mechanisms in the carbon system. 

Our planet was created in such a way that plants will consume C02, while animals generate it. The concentration of C02 in the atmosphere reflects the balance between plant and animal life on the planet. Prior to the industrial age, the movement ("flux") of carbon between the atmosphere, the land, and the oceans were kept in balance by nature s photosynthesis. In the last centuries, this balance has been upset not only by overpopulation and deforestation, but also by lifestyle changes—resulting in increased per capita energy consumption. 

The total quantity of carbon on Earth is about 41,000 billion metric tons (92% in the oceans, 6% on land, and 2% in the atmosphere). Prior to the Industrial Age, the concentration of C02 in the atmosphere was stable and balanced. Two hundred and ten billion tons of carbon dioxide entered the atmosphere and approximately the same amount was taken from the atmosphere by the photosynthesis of plants. That balance has been upset by fuel combustion, deforestation, and changing land use as the population increased. 

Biological strategies to remove C02 from the atmosphere, although not the focus of this report, deserve mention. These strategies remove carbon from the atmosphere by photosynthesis. On land, storage usually takes place at the same site as that of capture—for example, in a tree. Increases in atmospheric C02 enhance plant growth up to a point that is yet to be fully understood. In the ocean, capture is via various organisms at the surface that then sink into the deep ocean. 

Conditions of deposition of silica from natural waters. At the present time it is considered to be firmly established that only biological extraction of silica from river and ocean waters sharply undersaturated in Si02 is possible (Strakhov, 1960, 1966). In the oceans this process takes place mainly in the uppermost layer, where photosynthesis occurs. Diatomaceous plankton sink down when they die and the silica gradually begins to dissolve (Bogoyavlenskiy, 1966). Despite strong solution of suspended silica during deposition, 0.01-0.1 of the silica reaches the surface layer of the bottom sediments. 

What you are saying is very interesting. I was just wondering if this is not possible with the presence of the extra activity in this period of algae or other phytoplankton, which can under particular conditions have increased the photosynthesis in water, in the oceans. 

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