Plankton composition

Other roles for noxious metabolites produced by certain phytoplankton species include mediation of allelopathic interactions [47]. Allelopathy covers biochemical interactions among different primary producers or between primary producers and microorganisms. These can provide an advantage for the producer in the competition among different photoautotrophs for resources. Although not directly involved in chemical defense, allelopathic metabolites can affect the dominance and succession of species in phytoplankton therefore they are crucial for understanding plankton composition. In contrast to the fresh water environment, the location of many studies on the role of allelopathic interactions, which have identified active compounds [47], only few studies have addressed this topic in the marine environment. 

Collier, R. W., and Edmond, J. M. (1983) Plankton Compositions and Trace Metal Fluxes from the Surface Ocean, in Trace Metals in Seawater, NATO Conf. Ser. 4, V. 9, Plenum, New York, pp. 789-809. 

Finland 1-2 depth integrated samples from 0 to 2 m from V in IX (X). Biomass classihcation method based on statistical analysis of reference sites almost finalised for some types. Method for plankton composition under development (proposed method Lepisto et al., 2006). Method for blooms under development, difficulties with defining reference conditions. The % of cyanobacteria intercalibrated within the Northern GIG. 

Redfield, A. C. (1934). On the proportions of organic derivatives in sea water and their relation to the composition of plankton. In "James Johnstone... 

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. 

Much of the geographic variability in sedimentary ( Paxs/ °Thxs) observed in modern sediments may be explained by variability in the composition of biogenic particles arising from variability in the structure of the planktonic ecosystem. This can be inferred from the composition-dependence of F(Th/Pa) (Fig. 8), and is shown explicitly by the relationship between sediment trap ( Paxs/ °Thxs) and the opal/calcite ratio of the trapped particles (Fig. 9). Sediment trap ( Paxs/ °Thxs) also exhibits a positive relationship with the mass flux of particles, but the correlation is poorer than that with particle composition (Fig. 9). Indeed, the relationship between particulate ( Paxs/ °Thxs)... 

Martin, J.H. and G.A. Knauer. 1973. The elemental composition of plankton. Geochim. Cosmochim. Acta... 

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. 

Deviations from the stoichiometry given in Eq. 8.4 have been observed. They are the result of several phenomena, such as variability in the elemental composition of plankton. Furthermore, not all of the POM that is respired is plankton. Other types of... 

One important determinant in setting the Redfield-Richards ratio is the species composition of the plankton. For example, green algae on average tend to have much higher N-to-P ratios (27) than the red algae (10). Even within a species, these ratios are somewhat variable as they depend on nutrient availability and physiological... 

In contrast to their rather low dissolved concentrations in seawater, some of the trace metals, e g., iron and aluminum, along with oxygen and silicon, comprise the bulk of Earth s crust. Some trace elements are micronutrients and, hence, have the potential to control plankton species composition and productivity. This provides a connection in the crustal-ocean-atmosphere fectory to the carbon cycle and global climate. 

Trace metals are resolubilized from the biogenic hard and soft parts in much the same way as the macronutrients. Thus, the depth profiles of the trace metals with high EFs tend to be similar in shape to those of the nutrients. Efforts have been made to develop a Redfield-Richards type ratio far the trace metals in marine plankton. Surprisingly, field and lab work suggests that a relatively constant composition can be defined for whole... 

The unique chemical composition of cosmogenous debris has provided some insight into why approximately 70% of the species of organisms on Earth were driven extinct over a relatively short time interval approximately 66 million years ago. Evidence for this mass extinction has been observed in marine sediments throughout all the ocean basins. In a contemporaneous layer deposited at the end of the Cretaceous period, the hard parts of many species of marine plankton abruptly vanished from the sedimentary record. This sedimentary layer is also characterized by a large enrichment in the rare element iridium. 

In some sediments, downcore variations in the bulk chemical composition are interpretable as records of temporal shifts in the elemental composition of the sinking POM. Such shifts are caused by changes in the production of sinking POM, which are in turn the result of fluctuations in the abundance and diversity of the overlying plankton community. In nearshore sediments, fluctuations in river runoff and lateral transport can lead to shifts in the supply rate of terrigenous organic matter. An example of a nearshore sediment core in which such fluctuations have been recorded is shown in Figure 23.18. 

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