Trophic Diatom

Revised form of Trophic Diatom Index (TDI Kelly et al.. 2006)... 

In quality-control studies, Kelly (2001) used benthic diatom specimens to compare performance of a trained counter and an auditor. The Trophic Diatom Index counts for 58 UK river samples varied by as much as 30 per cent between counters, with 13 of the 58 counts having more than 10 per cent discrepancy. It seems in these circumstances that the errors are non-linear, with the most error-prone counts obtained from those samples with low degrees of species Bray-Curtis similarity (defined in Gauch, 1982 i.e. most variety within the sample). 

Mason RP, Reinfelder JR, Morel EMM. 1996. Uptake, toxicity, and trophic transfer of mercury in a coastal diatom. Environ Sci Technol 30 1835-1845. 

Figure 11. Uptake rates of inorganic Hg (a) and of methylmercury (b) by a marine alga as a function of the octanol-water distribution ratio of the Hg-species under various conditions of pH and chloride concentrations. The neutral species HgCl and CH5HgClH diffuse through the membranes. Reprinted with permission from [79] Mason, R. P. et al. (1996). Uptake, toxicity, and trophic transfer in a coastal diatom , Environ. Sci Technol., 30, 1835-1845 copyright (1996) American Chemical Society...

In addition to serving as the major food source to heterotrophic bacteria, DOM plays an important ecological role in enabling marine organisms to control various aspects of their environment including trophic interrelationships. This is accomplished by the secretion or exudation of specific molecules, called secondary metabolites. These are generally LMW compounds that tend to be species specific in their source and targets. Some act as toxins that repel or kill competitors or predators. As noted earlier, some diatoms... 

Fig.1 Generalized pelagic food web [ 13]. The old view of a simple food chain vertical line in this figure) with phytoplankton (mainly diatoms) at the base, herbivorous mesozoo-plankton (mainly copepods) at the second trophic level, and planktivorous fish has been extended to a pelagic food web including nanoplankton (<20 pm), picoplankton (<2 pm), and their protozoan feeders lower left). Herbivorous tunicates and jellyfish as primary carnivores also play a role, as do mixotrophic flagellates. The main pathway of energy flow depends on the nutrient scenarios [13]. DOC=dissolved organic carbon, HNF=heterotrophic nanoflageUates. From [13] with permission of Kluwer Academic Press...

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.

Hansen B, Tande KS, Berggreen UC (1990) On the trophic fate of Phaeocystis pouchetii (Hariot). III. Functional responses in grazing demonstrated on juvenile stages of Calanus finmarchicus (Copepoda) fed diatoms and Phaeocystis. J Plankton Res 12 1173-1187... 

Houde SEL, Roman MR (1987) Effects of food quality on the functional ingestion response of the copepod Acartia ton-sa. Mar Ecol Prog Ser 40 69-77 Huntley M, Tande K, Eilertsen HC (1987) On the trophic fate of Phaeocystis pouchetii (Hariot). II. Grazing rates of Cal-anus hyperboreus (Krpyer) on diatoms and different size categories of Phaeocystis pouchetii. J Exp Mar Biol Ecol 110 197-212... 

Several ecosystem models with Phaeocystis and diatoms as dominant primary producers but various trophic resolution, have been implemented to describe seasonal cycles of ecosystem constituents and elemental fluxes in areas where Phaeocystis blooms have been recorded the Barents Sea (Wassmann and Slagstad 1993), the southern North Sea (Gypens et al. 2004 Lancelot et al. 2005 Lacroix et al. 2006), and the Southern Ocean (Arrigo et al. 2003 Pasquer et al. 2005 Tagliabue and Arrigo 2005,2006). 

Phaeocystis blooms in the southern North Sea without impacting on diatoms should decrease nitrate loads. Further MIRO simulations showed that (i) a significant sink of atmospheric C02 was associated with Phaeocystis blooms in the southern North Sea (Gypens et al. 2004), (ii) the coastal ecosystem had a low nutrient retention and elimination capacity, (iii) the trophic efficiency of the planktonic system was low, and (iv) both were modulated by meteorological forcing (Lancelot et al. 2005). 

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