Plankton growth

Much of the trace metal demand of plankton in the open ocean may be supplied by the aeolian transport of dust. If trace metals limit plankton growth, the factors that control the transport of dust will also ultimately control the ocean s biological pump and, hence, atmospheric CO2 levels. This suggests the existence of powerful feedbacks among the processes that control global climate. For example, shifts in climate that lead to regional... 

The problem with this fixed nitrogen is that its use as a fertilizer requires land application. While some of the nitrogen is retained by the plants, much is carried off the land as stormwater runoff This increases the concentration of DIN in groundwater and river-water. Drainage of these waters into the coastal ocean supplies nutrients that stimulate plankton growth. Remineralization of the plankton biomass can lead to development of hypoxic and anoxic conditions in coastal waters. 

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. 

Because of the high concentrations of inorganic carbon in surface waters of the ocean, it is rarely thought about as a potential hmiting factor for plankton growth. However, several recent studies taking confluent research tracks have shown elevated Die stimulates both growth and N2 fixation in Trichodesmium. 

This stoichiometry cannot he taken very seriously at this point as it is variable from species to species, and it is sure to evolve as more data become available. None the less, it clearly demonstrates the order of magnitude of the concentration of trace metals necessary for plankton growth. Iron and manganese have concentrations ten times higher than the other trace metals, but still 100 times lower than the macronufrient phosphorus. 

The plankton was collected from several ponds situated in the vicinity of the river Po. The ponds were fed by the Po water downstream to a power plant. The relatively high water temperature accelerated plankton growth, allowing the collection of the total amount necessary for the reference material within a relatively short period. The collection was done with a manually-operated net with 125 pm apertures. The wet material collected was packed in double-layer polythene bags and kept at -20 C until freeze-drying. 

Slagstad, D. and Stple-Hansen, K. (1991) Dynamics of plankton growth in the Barents Sea. Model studies. Polar Research, 10, 173-186. 

Iron is the most abundant transition element in the Earth s crust and, in general, in all life forms. An outline of the distribution of iron in the Earth s crust is shown in Table 1.2. As can be seen, approximately one-third of the Earth s mass is estimated to be iron. Of course, only the Earth s crust is relevant for life forms, but even there it is the most abundant transition element. Its concentration is relatively high in most crustal rocks (lowest in limestone, which is more or less pure calcium carbonate). In the oceans, which constitute 70 percent of the Earth s surface, the concentration of iron is low but increases with depth, since this iron exists as suspended particulate matter rather than as a soluble species. Iron is a limiting factor in plankton growth, and the rich... 

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