Concentration in phytoplankton

The accumulation of HOCs in phytoplankton plays an important role in food-web bioaccumulation. Both the increased times to steady state and the effect of dilution decrease accumulation in phytoplankton. This decrease results in a lower phytoplankton body burden and a decreased exposure in higher organisms. As a result, an equilibrium-based model will tend to overestimate concentrations in phytoplankton, and this overestimate will be evident throughout the food web. 

V pg-kg-1 lipid lipid-normalized chemical concentration in phytoplankton... 

Gobas (1993) published a foodweb bioaccumulation model to predict chemical concentrations in phytoplankton, macrophytes, zooplankton, benthic invertebrates, and fish, based... 

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. 

Kotak, B.G. et al., Role of chemical and physical variables in regulating microcystin-LR concentration in phytoplankton of eutrophic lakes. Can. J. Fish. Aquat. ScL, 57, 1584, 2000. 

Fig. 9.6. Model simulation for Hg. Curve 1 gives the values for Hg-concentration in lake water. The values do not reach a perfect steady-state level due to the fact that so much Hg has been accumulated in the catchment area during the last 50 years (initial amount in the catchment is 15 000 g in the entire catchment situated in central Sweden data for our "mean" lake), the outflow rate from the catchment is 0.0025 (1/year). Curve 5 illustrates a simulated liming during year 20 which would increase pH from 6 to 6.7. Curves 2, 3 and 4 show the effects of such a liming on Hg-concentrations in phytoplankton, prey (bottom fauna, zooplankton, small fish) and predatory fish (pike, large perch, etc.)...

Peech Cherewyk 2002 Tsui and Wang 2004). Phytoplankton have a constrained trophic position are not consumed by fish, wildlife, or humans, and are indirectly relevant to the pnbhc or the policy commnnity. They wonld respond veiy rapidly — within minntes or honrs — to changes in MeHg concentrations in water. Phytoplankton obtain MeHg directly from water (Mason et al. 1996), and algal density can inlinence concentrations of MeHg in phytoplankton via biomass dilntion (Pickhardt et al. 2002). 

Little is known about MeHg in phytoplankton, particnlarly freshwater phytoplankton (Becker and Bigham 1995). Concentrations of MeHg in freshwater phytoplankton are related to those in water bnt the partitioning of MeHg between water and phytoplankton is strongly affected by concentrations of dissolved organic matter (Watras et al. 1998). 

In water, the concentration of DDT is usually higher than that of its metabolytes in phytoplankton the ratio is close to that observed in water in zooplankton, there is more DDT present than its metabolytes. In fish, the ratio usually changes in favor of the metabolytes in organs and tissues, DDD, and especially DDE, concentrations are at the same level, if not higher, than that of DDT (Table 4.10). 

Assimilation At the end of each month phytoplankton concentrations in the surface level were adjusted according to the MERIS satellite chlorophyll-a concentrations of the corresponding month. The data assimilation is only done for shallow waters, with a water depth lower than 250 m (see Figure 2.1). 

Fig. 2.7 Mean phytoplankton concentration in shelf zones, AGG versus MERIS Case 2 (left) and SAT versus MERIS Case 2 (right).

Dimethyl sulfide is derived primarily from the enzymatic hydrolysis of dimethylsulfoniopropionate(CH3)2S+CH2CH2COO DMSP),an osmoregulatory compound produced by a wide variety of marine phytoplankton [313,317]. Intracellular DMSP hydrolysis has been shown in phytoplankton [318], in macro algae [319], and also in bacteria following uptake of DMSP from seawater [320]. Reported seawater concentrations of dissolved dimethyl sulfide (< 0.1-90 nM) and DMSP (1 -1000 nM) vary with increasing depth, spatially from coastal areas to the open ocean, and also temporally from winter to summer [313-316]. 

Sunda, W. G. and Huntsman, S. A. (1995). Regulation of copper concentration in the oceanic nutricline by phytoplankton uptake and regeneration cycles, Limnol. Oceanogr., 40, 132-137. 

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