Water trophic state

Dodds WK, Jones JR, Welch EB (1998) Suggested classification of stream trophic state distributions of temperate stream types by chlorophyll, total nitrogen, and phosphorus. Water Res 32 1455-1462... 

An example of a CCA biplot is shown in Figure 6. It was developed to explore the relationships between trophic state, several water chemistry... 

Figure 6. Canonical correspondence analysis for surface sediments of 41 lakes in British Columbia, Canada, that encompass a broad range of trophic states. Circles represent lakes and triangles represent the 25 most abundant diatom taxa. Arrows indicate environmental variables that correlate most strongly with the distribution of diatom taxa and lake-water chemistry, as detected by forward selection. Maximum depth (Zntax) and total phosphorus (TP) were transformed by using the In (x + 1) function. This analysis is discussed in detail in reference 46.

A crucial difference between aquatic and terrestrial ecosystems is that N additions do not commonly stimulate growth in aquatic systems, as seems to be the case in many terrestrial systems. N limitation may be the exception in aquatic systems rather than the rule. The question of whether N limitation is a common occurrence in surface waters will play a large role in determining whether N deposition affects the trophic state of aquatic ecosystems. 

Trophic state can be measured directly via indicators of phytoplankton biomass and nutrient concentrations or indirectly by measuring water transparency (Table 1). Water transparency can be an accurate indicator of phytoplankton productivity, even though it is affected by nonbio-logical particles suspended in the water column. Secchi disk depth is the oldest, simplest, and quickest quantitative measure of water clarity. A Secchi disk is a black and white disk that is... 

Because an increased supply of nitrogen in marine waters and/or phosphorus in freshwaters is typically responsible for eutrophication, directly measuring the concentration of these nutrients can indicate trophic state. Nutrients in water are either dissolved or bound to particulates produced in situ and deposited into water bodies from groundwater, atmospheric deposition, and drainage basin runoff. To measure trophic state, nutrient concentrations are measured in samples... 

The given examples presented in this section illustrated the potential of UV spectrophotometry for improving information on the quality of water bodies and highlighted the perspectives of their integration on new approaches on water management. The portable instrument is in particular useful for the spatial and temporal water quality survey (river basin, lake...) based on measurements of some well-known physico-chemical parameters (TSS, TOC, COD, BOD, NO3-, surfactants). Nevertheless, the UV spectrophotometry and the suitable software developed to enhance the deconvolution of UV spectra allows to propose others applications, in particular qualitative interpretation in order to assess, for example, the trophic states of lakes. 

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