Diel patterns

Inputs from WWTP effluents can also affect the hydrologic and nutrient concentration regimes of recipient streams at different temporal scales. Daily variations of these parameters may be exacerbated in streams below the WWTP input by the diel patterns of the effluent discharge associated with plant operation [46]. In contrast, at the annual scale, seasonal variations of physical and chemical parameters upstream of the WWTP may be dampened by the constant input of additional water and nutrients from the WWTP. At its extreme, naturally intermittent or ephemeral streams may turn into permanent streams downstream of WWTPs [28, 30]. In these effluent-dominated streams, the relative contribution of WWTP inputs may vary widely on an annual basis, as shown by the 3-100% range measured in a Mediterranean stream [47]. Finally, WWTP inputs also cause shifts in the relative availability of N and P as well as in the relative importance of reduced and oxidized forms of N in the stream [30, 47]. The magnitude of these shifts depends on the level of wastewater treatment (i.e., primary, secondary, or tertiary treatment), the type of WWTP infrastructure (e.g., activated sludge reactor. 

Wang B, Neue HU, Samonte HP. 1999. Factors controlling diel patterns of methane emission via rice. Nutrient Cycling in Agroecosystems 53 229-235. 

Detailed studies of H202 distribution in marine systems and factors affecting its formation have resulted primarily from the work of Zika and co-workers (9, 11, 12, 20-24, 30, 31). These studies indicated that the surface ocean, 5 m and less deep, was close to 100 nM in H202. Some diel variability was reported in subtropical surface waters, but the variation from night to day was approximately 10-20%. Initial studies of Jacks Lake, Ontario, Canada (13), showed surface water (1 m and less) diel variability of from <10 nM at night to >500 nM during the day. The contrasting diel pattern observed in the two systems led us to the next phase of our experiments. 

Although the diel patterns of H2S emission from the water surface and the soil surface over the Disticlis spicata are reversed (Figure 6), the overall (integrated) emission rate is about the same (60 and 56 /ig S nr2 hr1, respectively). Integrated emission rates of DMS were also similar from the two different surfaces, 6.8 and 62 ng S nr2 hr1, respectively. Greater than 90% of the DMS emission from the D- Spicata/soil surface occurred between the hours of 09 00 and 20 00. 

Their studies revealed a diverse assemblage of diazotrophs contribute distinct diel patterns that vary over the seasonal cycle depending on the exact composition of the diazotrophic assemblage. 

Benthic cyanobacteria also show strong diel patterns which depend on the composition of the cyanobacterial population. Mats dominated by heterocyctous cyanobacteria generally show a daytime maximum while those dominated by non-heterocystous forms exhibit maximum nitrogenase activity at night (e.g., Paerl et al., 1988 Stal and Krumbein, 1987 Steppe and Paerl, 2005). 

Pettersson, K., and Sahlsten, E. (1990). Diel patterns of combined nitrogen uptake and intracellular storage of nitrate by phytoplankton in the open Skagerrak. J. Exp. Mar. Biol. Ecol. 138, 167-182. 

Currin, C., and Paerl, H. (1998b). Environmental and physiological controls on diel patterns of N2 fixation in epiphytic cyanobacteria communities. Microb. Ecol. 35, 34—45. 

Harris, R. P., and Malej, A. (1986). Diel patterns of ammonium excretion and grazing rhythms in Calanus helgolandkus in surface stratified waters. Mar. Ecol. Prog. Ser. 31, 75—85. 

P. Boelen, A.F. Post, M.J.W. Veldhuis, A.G.J.Buma (2002). Diel patterns of UVBR induced DNA damage in picoplankton size fractions from the Gulf of Aqaba, Red Sea, Microb. Ecol, in press. 

Several researchers have also suggested that bacteria mediate mercury reduction [54,55]. SicUiano et al. [56] recently examined the role of microbial reduction and oxidation processes in regulating DGM diel (over a 24h period) patterns in freshwater lakes. The authors demonstrate that photochemi-cally produced hydrogen peroxide regulates microbial oxidation processes and may account for the diel patterns observed in DGM data. Overall, the mechanisms responsible for mercury reduction and the relative contributions of biotic and abiotic processes are still unclear but solar radiation appears to be a common instigator of photo-reduction. 

Holomuzki, J. R. 1986. Predator avoidance and diel patterns of microhabitat use by larval tiger salamanders. Ecology, 67, 737-748. 

Zotz, H Winter, K (1996). Diel Patterns of CO2 Exchange in Rainforest Canopy Plants. In Tropical Forest Plant Ecophysiology, S.S. Mulkey, R.L. Chazdon A.P. Smith, (Eds), 89-113, Chapman Hall, ISBN 0412035715, New York. 

Our mechanism of Br activation can thus also account for the presence of Cl atoms in MBL [1,2]. The simulated overnight accumulation of a Cl- and Br-atom precursor in conjunction with the daytime formation of HCl agrees with diel patterns observed by Pzenny et al. [2]. The main fate of Cl atoms is reaction with ozone, and to a smaller extent with methane. The additional methane loss on the second model day is small ( 2 %, considering recycling on sulphate aerosol), but may reach 18 %, if the sea-salt aerosol content is increased by a factor of five. If recycling... 

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