Saturday, April 07, 2007

Phytoplankton adaption by modulation.

Recent work by two theoretical ecologists (Huisman & Weissing, 1999; 2001),has shown that competition for resources by as few as three species can result in long-term oscillations, even in the traditionally convergent models of plankton species growth. For as few as five species, apparently chaotic behavior can emerge. Huisman and Weissing propose these phenomena as one possible new explanation of the paradox of the plankton, in which the number of co-existing plankton species far exceeds the number of limiting resources, in direct contradiction of theoretical predictions. Continuously fluctuating species levels can support more species than a steady, stable equilibrium distribution.

Their results show that external factors are not necessary to maintain non-equilibrium conditions; the inherent complexity of the “simple” model itself can be sufficient.As we observed here with Bauers statement

"Only living systems never reach equilibrium, for they constantly work against stability" [4, p.43]. According to Bauer, the source of free energy(or” the work of structuring forces" and "structural energy" are the synonyms) is the nonequilibrium of molecular structure of living matter

For example, where we assume a fixed population size, their population size varies and is constrained only by the finite resources themselves normally the Liebig's Law of the Minimum where growth is determined by the availability of the scarcest resource nitrogen, phosphorous etc..

As carbon is not is short supply in the ocean-atmosphere interface we can expect changes to the assimilation and transformation to be unaffected by changes to ph levels in the ocean.( The processes of carbon chemical-biological cycle, air-water exchange and carbonate system transformation)

Indeed Yakushev, E.V. and Mikhailovsky, G.E., 1995. found some biological attenuation (modulation)of ph levels during phytoplankton blooms.

The dramatic increase in atmospheric carbon dioxide (CO2) concentrations observed during the past decades can be associated with the natural climatic oscillations or/and with anthropogenic influence. Concern about the potential role of CO2 as a “greenhouse gas” had led to necessity of investigation of this element global biogeochemical cycle peculiarities. The oceans play an important role in this cycle, containing large reservoirs of dissolved inorganic carbon as gaseous CO2(g), bicarbonate (HCO3-) and carbonate (CO32-) ions. Because of it, the ocean ultimately determines the atmosphere's CO2 content (Siegenthaler, Sarmiento, 1993). Information about the CO2 system behavior can be obtained by investigations of the processes which affect the carbonate system parameters distribution and variability.

One of the most interesting aspect of this problem is the role of marine biota. When we speak about this, we consider the aggregation of gaseous CO2 into particulate organic carbon (POC), which can be transported into the deeper layers, sedimented on the bottom and thereby excluded from the global cycle and also of the POC mineralization and respiration processes (so-called “soft tissue pump” (Gruber et al, 1996) . However during the phytoplankton bloom the decrease of CO2 is accompanied by disbalance of the system which can initialize the activity of the other “pumps”: (“solubility pump” - ocean-atmosphere CO2 exchange, and “carbonate pump” - and formation dissolution of calcium carbonates).

During the bloom the consummation of gaseous CO2 by phytoplankton leads to the disbalance of the carbonate system equilibrium. This results in increased pH values and therefore in changes in the carbonate system balance toward increases in carbonates and additional decreases in gaseous CO2. In other words, during the bloom the upper layer gaseous carbon dioxide decreases for two reasons - consummation of the organic matter synthesis and transformation from gaseous CO2 to CO3, initiated by pH changes.

In this case during the bloom period one can observe decrease of TCO2 and dissolved CO2 while the value of carbonate alkalinity (AlkC) remains constant to fulfill the sea water electricity neutrality equation (Millero, 1995, Dickson, 1992).


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