Phytoplankton elemental composition

Relationship between the trace elemental composition of phytoplankton, continental crust and seawater. Phytoplankton and crustal abundances are normalized to phosphorus (ppm trace metal ppm P). Seawater trace elements abundances are normalized to phosphate (ppb trace metal ppb P as phosphate). Source-. From Quigg, A., et al. (2003). Nature 425, 291-294. 

In all cases where complete elemental analyses have been found, samples were isolated by SPE using XAD resins. As discussed earlier, this method isolates mainly hydrophobic organic compounds from seawater and is strongly biased against N-containing compounds. Polar ionic solutes have little or no affinity for XAD resins. There are perhaps more published results than have been found in this review, but the data in Table 11.4 are hopefully representative of elemental analyses for isolated samples of marine DOM. For reference, two calculated estimates of the bulk chemical composition of marine phytoplankton are included in Table 11.4. All elemental compositions in Table 11.4 are expressed as molar quantities in Redfield format, using an empirical formula that contains 106 moles of C. 

Smith EM (1998) Coherence of microbial respiration rate and cell-specific bacterial activity in a coastal planktonic community. Aquat Microb Ecol 16 27-35 Smith WO Jr, Nelson DM, DiTullio GR, Leventer AR (1996) Temporal and spatial patterns in the Ross Sea phytoplankton biomass, elemental composition, productivity and growth rates. J Geophys Res 101 18455-18466 Smith WO Jr, Marra J, Hiscock MR, Barber RT (2000) The seasonal cycle of phytoplankton biomass and primary productivity in the Ross sea, Antarctica. Deep-Sea Res II 47 3119-3140... 

Ho T-Y, Quigg A, Finkel ZV, Milligan AJ, Wyman K, Ealkowski PG, Morel EMM. The elemental composition of some marine phytoplankton. J. Phycol. 2003 39 1145-1159. 

Table 1 Elemental composition of marine phytoplankton from cultures and plankton tows.

The overall consequence of the co-evolution of oxygenic photosynthesis and the redox state of the ocean is a relatively well-defined trace-element composition of the bulk phytoplankton. Analogous to Redfield s relationship between the macronutrients, trace-element analyses of phytoplankton reveals a relation for trace elements normahzed to cell phosphorus of (C125N16P1S13... 

Figure 7 The excess trace element composition in black shales compared with that of calculated marine phytoplankton, and the relationship between trace elements in seawater and phytoplankton (inset) (source Quigg...

Humic and fulvic acids are presumed to arise by two classical natural processes. Terrestrial humates are found in the following pathway plants soil humates peat — coal. Aquatic humates start with soil leachates or marine phytoplankton and go through a sequence sediments kerogen petroleum. There are conditions which mix the two processes as well. As a result, there are a host of names and symbols applied to these compounds, such as peat humic acid, coal fulvic acid, soil humic acid, and so on. Depending on their oxidation state, they may be heavily bound to metal ions. Within each class of humic acid, there are subclassifications, such as Podzol Bj, humic acid, lignite fulvic acid. Other types are classified by geological age, depth in a sediment, and type of aquatic environment. The following discussion will attempt to relate elemental composition to these broad classes of humates. 

Biogeochemical explanations of variations in phytoplankton floristic composition work at two levels. The first level is qualitative, and concerns the crude distinctions between algae that require silicon (diatoms and some others) and those that don t, or between cynaobacteria able to assimilate N2 and all other pelagic photoautotrophs. The second level is quantitative, and concerns the idea that optimum ratios of the nutrient elements required for growth may... 

Burkhardt S, Riebesell U (1997) C02 availabihty affect elemental composition (C N P) of the marine diatom Skeletonema costatum. Mar Ecol-Prog Ser 67-76 10 Burkhardt S, Riebesell U, Zondervan 1 (1999a) Effects of growth rate, CO2 concentration, and cell size on the stable carbon isotope fractionation in marine phytoplankton. Geochim Cosmochim Acta 62 3729-3741... 

The simplest way of describing the ehemieal nature of biomass is by its elemental composition. For marine phytoplankton as primary producers a relationship was found to the nutrients available in seawater whieh led to the definition of the Redfield ratio as C N P = 106 16 1 (Redfield et al. 1963). Derived from this is an average molecular formula of phytoplankton organic matter related to the general process of phytosynthesis (of which the reverse signifies remineralization) ... 

This equation was originally proposed for "average" plankton, a category that included both zooplankton and phytoplankton. This mean elemental ratio of C/N/P = 106/16/1 by atoms is highly conserved (Falkowski et al., 1998) and reflects the average biochemical composition of marine phytoplankton and their early degradation products. 

Redfield (1934), who analyzed the major elemental content of many samples of mixed plankton (phytoplankton and zooplankton) caught in nets towed through the surface ocean. They compared the carbon, nitrogen, and phosphorus composition of these collections to concentration profiles of dissolved inorganic carbon (DIC), NOs, and P04 throughout the water column. This pioneering research demonstrated that these three elements are continually redistributed in the ocean by selective removal into plankton cells and their remains (i.e., fecal pellets), which are then efficiently respired as they sink through the marine water column. 

Selective changes in the relative abundance of bioactive elements delivered by rivers/estuaries also results in changes in the Redfield ratio, which can in some cases cause significant shifts in the composition and abundance of coastal phytoplankton. 

Proton and C-NMR data compare well with each other and suggest that surface ocean HMWDOM has a H C ratio of approximately 1.8—1.9 (Aluwihare, 1999 Benner et al, 1992) and an 0 C ratio between 1 and 1.1. These H C and 0 C ratios are very close to those of a pure carbohydrate with a general hexose structure (e.g., C6H12O6). In comparison, humic substances isolated from seawater have an H C ratio between 1.2 (direct elemental analyses) and 1.4 (based on NMR estimates) and are therefore, relatively C-rich (Hedges et al, 1992). The H C and 0 C composition of phytoplankton as estimated by NMR spectroscopy is approximately 1.7 and 0.3, respectively (Hedges et al, 2002). In comparison to phytoplankton... 

Of particular interest in relation to Si N interactions and diatoms is the relatively recent finding that iron provides a strong regulating influence on the species composition of phytoplankton assemblages, as well as on the elemental ratios of diatoms. Fe and Si supply appear to be particularly important in several large areas where high concentrations of other macro nutrients (N, P) are present in surface waters. These HNLC areas (Minas et al, 1986) are characterized by low phytoplankton biomass... 

Then there are wider questions about the possible limiting roles of various trace elements in key biogeochemical processes Do trace elements other than iron limit phytoplankton growth and primary production Is the composition of phytoplankton assemblages controlled by trace elements Are various processes in the cycle of nitrogen limited by trace elements (e.g., N2 fixation by iron N2O reduction by copper) What are the links between trace elements and the reduced sulfur cycle in surface seawater ... 

Although nitrogen is the element primarily controlling eutrophication in estuaries and coastal seas, and phosphorus is the element primarily controlling eutrophication in lakes, other elements can have a major influence on the community structure of aquatic ecosystems and can influence the nature of the response to eutrophication. A key element in this regard is silica (silicon), an element required by diatoms. The availability of silica in a water body has little or no influence on the overall rate of primary production, but when silica is abundant, diatoms are one of the major components of the phytoplankton. When silica is in low supply other classes of algae dominate the phytoplankton composition. 

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