Biota phytoplankton

The oceanic biota reservoir (4) is also within the surface layers. Although organisms reside at all depths within the ocean, the overwhelming majority reside within the photic zone where phytoplankton dominate. The oceanic biota reservoir only contains roughly 1 /30 as much P as the land biota reservoir. This is primarily because oceanic biomass is composed of relatively short-lived organisms, while land biomass is dominated by massive long-lived forests. 

Table 10.3 Estimated Equilibrium (tf, ipw, A",lipoc) versus Measured Lipid-Normalized Bioaccumulation Factors BAFm) and Biota-Sediment Bioaccumulation Factors (BSAFilipoc) for Three PCB Congeners in Phytoplankton and Various Sediment-Dwelling Organisms in Western Lake Erie0...

The model applies equilibrium partitioning to estimate chemical concentrations in phytoplankton, macrophytes, zooplankton, and benthic invertebrates. Chemical concentrations in sediment and water, along with environmental and trophodynamic information, are used to quantify chemical concentrations in all aquatic biota. This model can be applied to many aquatic food webs and relies on a relatively small set of input parameters which are readily accessible. 

Wang, J.S., Chou, H.N., Fan, J.-J., Chen, C.-M. (1998) Uptake and transfer of high PCB concentrations from phytoplankton to aquatic biota. Chemosphere 36, 1201-1210. 

Hofmann and Ambler, 1988). The Hofmann and Ambler (1988) model had 10 compartments which included NO3 and NH4, large and small phytoplankton size classes and a copepod submodel (Fig. 33.3). The latter included parameterizations for N assimilation, excretion, egg production, molting and predation. Steele and Frost (1977) incorporated comparable levels of detail more than 10 years earlier. Although not, strictly speaking, an N-based model, it specified N as the limiting inorganic nutrient and assumed a fixed C/N ratio for biota defined in carbon units, so the distinction is to some degree semantic. 

Figure 1 Diatoms are one of the most abundant biota containing siliceous skeletal material in the marine environment. Radiolaria, silicoflagellates, and siliceous sponges also deposit this amorphous phase for structural support. The diatoms in the figure (Corethron sp.) were collected from the Antarctic continental shelf, occurring as a monotypic assemblage in a large phytoplankton bloom. The siliceous frustules in this figure t3fpically are 100-...

The hypolimnion of this lake is titrated with biota (sinking phytoplankton). Estimate the concentration of the various species that develop during this titration (e.g., progressive time of stagnation during summer stratification versus pe). The titrant , that is, the sinking biota, can be looked at as an electron complex that is, we can titrate with electrons. Such a calculation is of course only partially correct, but it shows synoptically how anoxia progresses in such a situation. We can use, as a first approximation, the constants valid for 25°C ... 

ROS may also affect microorganisms through the production of toxic trace metal species. For example, the photolysis of organic Cu-complexes and interactions with 02 may increase the Cu bioavailability and hence Cu toxicity to phytoplankton. This interaction with transition metals is likely to be one of the main processes through which photochemically produced 02 , or other charged ROS, can have an adverse affect on aquatic biota but further studies are needed to ascertain the ecological impact of these types of reactions in natural waters. 

The role of ectoenzymes in Fe cycling is not known presently, but we have some evidence of Fe(III) reduction in phytoplankton cultures, and Fe(III) complexes are reduced by plasmamembrane reductases. Hydrogen peroxide can oxidize Fe(II) (Waite and Morel, 1984) and probably reduce Fe(III) in light, thus implying that the biota may promote this reaction through the activity of their extracellular enzymes. 

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