Diel cycling

Nimick, D.A., Gammons, C.H., Cleasby, T.E. et al. (2003) Diel cycles in dissolved metal concentrations in streams occurrence and possible causes. Water Resources Research, 39(9), HWC21-HWC217. 

Petit, M., G. P. Alves, and P. Lavandier. 1999. Phytoplankton exudation, bacterial reassimilation and production for three diel cycles in different trophic conditions. Archiv fiir Hydrobiologie 146 285-309. 

There is considerable debate regarding the marine environment and the possibility of it being a major source of H2S. In a coastal area, integrated over tidal and diel cycles, a rate of H2S of 0.10 g S nr2 yr1, has been reported (26). 

In order to establish the sources of DMS we have made measurements of dimethylsulphoniopropionate (DMSP the precursor of DMS) and attempted to relate the two compounds to phytoplankton species and abundance. We have also investigated variations in DMS and DMSP with depth through the water column, with respect to diel cycling and monitored the effect of high and low nitrate concentrations on DMSP levels in laboratory cultures and in the N. Sea. 

Another consideration when calculating f-ratios is the diurnal variabUity of N versus carbon (C) metaboUsm. When relating new production to C export (sensu Eppley and Peterson, 1979), stoichiometric calculations of C export from N uptake can be in error when C and N uptake are not evaluated over appropriate timescales. Diel variability in uptake rates of various N compounds has been demonstrated (e.g., Cochlan and Harrison, 1991b Cochlan et al., 1991a Tremblay et al., 2000 Wilkerson and Grunseich, 1990) and faUure to integrate daUy uptake rates over an entire diel cycle may seriously bias estimates of f-ratios. 

Macisaac, J. (1978). Diel cycles of inorganic nitrogen uptake in a namral phytoplankton population dominated by Gonyaulax polyedra. Dmnol. Oceanogr. 23, 1—9. 

Blaaberg, V. K., Mouritsen, K. M., and Finster, K. (1998). Diel cycles of sulphate reduction rates in sediments of a Zostera marina bed, Denmark. Aquat. Microbiol. Ecol. 15, 97—102. 

Winter, C., Herndl, G. J., and Weinbauer, M. G. (2004a). Diel cycles in viral infection of bacterioplankton in the North Sea. Aquat. Microb. Ecol. 35, 207—216. 

Figure 3. Schematic of the time vs. depth distribution of floats released at various times during a diel cycle of nocturnal mixing and diurnal stratification in the Labrador Sea [E. D Asaro and G. Dairiki unpublished data as shown in 2]. The heavy line (a composite of three separate float deployments) depicts a possible depth history of a non-motile plankton over the 24 h period. Note that trajectories are terminated once they enter the stable diurnal thermocline since they actually start to ascend due to very slight positive buoyancy of the floats.

Depth related CPD patterns, diel cycles and mixing effects. 303... 

Figure 7. Diel cycles of CPD abundance in two bacterioplankton size fractions in the Gulf of Aqaba. (A) cell numbers of the major plankton groups (B) in situ sampling at water surface 0.2-0.8 fim (C) in situ sampling at water surface 0.8-10 /xm. [Redrawn from...

In summary, all the published diel cycles for DNA damage induction in marine bacterio- and phytoplankton indicate that, even when photorepair occurs, it will play a rather limited role. Photorepair does not hinder rapid build up of damage during the day. As a result, damage accumulation patterns are often found to roughly follow the DNA effective UV-B dose, especially after noon. 

R.D. Vetter, A. Kurtzman, T. Mori (1999). Diel cycles of DNA damage and repair in eggs and larvae of northern anchovy Engraulis mordax, exposed to solar ultraviolet radiation. Photochem. Photobioi, 69, 27-33. 

Dimethyl sulfide (DMS), CH SCH, is the largest natural contributor to the global sulfur flux (see Section 2.2.1). The DMS-OH rate constant, approximately 5 X 10 cm molecule s at 298 K, exceeds that of DMS-NO, by a factor of 4. (In contrast, the reactions of H2S and CH,SH with NO, are, respectively, 6000 and 40 times slower than that with OH.) The DMS lifetime in the marine atmosphere as a result of both OH and NO, reactions is on the order of one to several days, with the majority of the path occurring by OH at low latitudes and by NO, in colder, darker regions. Because of the photochemical source of OH, DMS removal by OH occurs only during daytime, leading to a pronounced diel cycle in DMS concentration. 

COS is produced in the ocean by photochemical oxidation of organic sulfur compounds whereby dissolved organic matter acts as a photosensitizer. The aqueous concentration of COS manifests a strong diel cycle, with the highest concentrations in daytime (concentration range on the order of 0.03-0.1 nmol U ). COS hydrolyzes in water to H2S at rates dependent on water temperature and pH. The flux of oceanic COS to the atmosphere may represent about one-third of the global COS flux. 

Nimick DA, Gammmis CH, Cleasby TE, Madismi JP, Skaar D, Brick CM (2003) Diel cycles in dissolved metal coneentrations in streams Oeeurrence and possible causes. Water Resourc Res 39. doi 10.1029/2002WR001571... 

Chapin TP, Nimick DA, Gammons CH, Wanty RB (2007) Diel cycling of zinc in a stream impacted by acid rock drainage initial results from a new in situ Zn analyzer. Environ Monit Assess 133 161-167... 

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