Plankton productivity

Figure 7 Diagram of the feedback loop involving climate and planktonic production of DMS. The ( + ) under biological production of DMS in the ocean indicates the uncertainty in the direction of the net feedback loop (Taken from Bigg," with permission of Cambridge University Press)...

Figure 7 Diagram of the feedback loop involving climate and planktonic production of DMS. The...

In the preceding sections, we have discussed the marine processes that control calcium carbonate s formation, dissolution, and delivery to the seafloor. Their combined effects determine the geographic distribution of calcium carbonate in marine sediments seen in Figure 15.5. As noted earlier, the global distribution of calcareous sediments does not seem to follow that of plankton production. This points to the overriding importance of the processes that control the dissolution and sedimentation of calcium carbonate. 

In the case of plankton, cell lysis that occurs shortly after death causes ATP to be released into seawater. Like most biomolecules, ATP is rapidly degraded in seawater by microbes. Thus, high surfece concentrations in Figure 22.5 reflect a rapid supply supported by the high rates of plankton production characteristic of the photic zone. Below the surface, concentrations decrease with increasing depth beneath the photic zone and, hence, distance from the biosynthetic source of the ATP... 

Longhurst, A.R. and Harrison, W.G., The biological pump profiles of plankton production and consumption in the upper ocean, Prog. Oceanogr., 22, 47, 1989. 

Matrai, P.A., and Vetter, R.D. (1988) Particulate thiols in coastal waters The effect of light and nutrients on their planktonic production. Mar. Chem. 33, 624—631. 

Keywords Benthos Biodiversity Fauna Necton Phytoplankton Plankton Productivity... 

Williams, P. J., and Robertson, J. I. (1989). A serious inhibition problem from a Niskin sampler during plankton productivity studies. Limnol. Oceanogr. 34, 1300—1305. 

With a simple underway technique for measuring pH, a strong correlation previously was found between pH, coastal upwelling, and the resulting planktonic production 6-8). However, discussions of these measurements were limited to changes that were greater than 0.1 pH units because, previously, pH was measured electrometrically and the electrometric measurement of pH may involve an absolute error of 0.1 pH units (9) thus, no attempt was made to look at the finer structure. 

The high bioavailability of Cd in the marine environment from Terra Nova Bay was ascribed to upwelling of deep nutrient rich water nearshore (70). Cadmiun has a nutrient-like concentration gradient in the water column, lower close to the surface and increasing with depth (75). In the water column, Cd would be absorbed by the phytoplankton, during the summer bloom, thus becoming available for benthic molluscs in which the Cd is bioaccumulated. Ecological studies undertaken in the inner and outer part of Potter Cove showed that after seasonal ice retreat no phytoplankton bloom occured (35). In spite of the low planktonic production, rich benthic animal comunities are found in the area (29). 

The role of Fe as a limiting nutrient has been well established in the last decade in the so-called high-nutrient low chlorophyll regions of the oceans. A series of massive iron seeding experiments carried out to test the iron hypothesis advanced by Martin and Fitzwater (1988) have unequivocally shown that iron supply limits plankton production in one third of the world s oceans, despite the perennially high surface concentration of macronutrients (Fig. 7.1). The dynamics of phytoplankton blooms are limited by iron supply, which... 

Barber, R. T., Hilling, A. K., 2003. History ofthe study of plankton productivity. In Williams P. J. 1. B., Thomas D. N., Reynolds C. S. (Eds.), Phytoplankton productivity. Carbon Assimilation in Marine and Freshwater Ecosystems. Blackwell Science Ltd.,Oxford, pp. 16-43. 

Upwelling. The rising of cold, deep water rich in nutrients due to the earth s rotation, but strongly dependent on local factors, and causing an increase in the planktonic production. 

All phytoplankton can assimilate the more labile forms of dissolved inorganic Fe(ll) and Fe(lll), and this is the main assimilation mode for bacteria under iron-replete conditions (Granger Price 1999). Extracellular bioreduction is an important route to these labile forms, but the photoreductive dissociation of Fe(lll) chelates in oceanic surface waters may play a major role in sustaining phyto-planktonic productivity (Sunda Huntsman 1995), as has been proposed for the aquachelins (Barbeau et al. 2001). 

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