Deep lakes

The destiny of most biological material produced in lakes is the permanent sediment. The question is how often its components can be re-used in new biomass formation before it becomes eventually buried in the deep sediments. Interestingly, much of the flux of phosphorus is held in iron(lll) hydroxide matrices and its re-use depends upon reduction of the metal to the iron(ll) form. The released phosphate is indeed biologically available to the organisms which make contact with it, so the significance attributed to solution events is understandable. It is not clear, however, just how well this phosphorus is used, for it generally remains isolated from the production sites in surface waters. Moreover, subsequent oxidation of the iron causes re-precipitation of the iron(lll) hydroxide floes, simultaneously scavenging much of the free phosphate. Curiously, deep lakes show almost no tendency to recycle phosphorus, whereas shallow... 

Aeration of the hypolimnion (lower, colder layer of water in a stratified lake) without disruption of stratification has been used in deep lakes. This has the advantage of not increasing the temperature of the hypolimnion and prevents the advection of nutrient-rich water into the epilimnion (upper, warmer layer of water in a stratified lake). Oxygen injection is preferred in order to prevent the build up of nitrogen super-saturation which is toxic to fish. "... 

Straskraba M (1998) Limnological differences between deep valley reservoirs and deep lakes. Int Rev Hydrobiol 83 1-12... 

Alexi and his friends ran down the hill to a swampy part of the woods that contained a deep lake that they called the black hole . No one knew how deep the lake was in the middle, but it was quite shallow near to one end. Here there was an island about 20 yards out from the edge. They had waded out to the island the summer before and the water had come up to just above their knees.There had been a lot of rain in the previous couple of weeks and the water now looked a bit deeper. Robin suggested that they wade out again, and began to take her shoes and socks off. (C)... 

Seasonally-Charged Deep Lake Water Cooling (DLWC)... 

C because water is at its most dense at this temperature. Summer warming penetrates only to about a 60-m depth. Thus, a deep lake such as Lake Ontario has within it a very large volume of naturally cold water that is seasonally replenished each winter. 

Morofsky, E., 2002. Seasonally-Charged Deep Lake Water Cooling (DLWC) for Downtown Toronto, published in the Proceedings of Terrastock 2000, Stuttgart, Germany. 

Canadian Urban Institute, 1991. Deep Lake Water Cooling, Report on the Conference, 16-18 June, 66 pp. 

Scientific American, 1999. In The Drink Cities Try Cooling Off with Deep Lake Water, October, pp. 47-48. 

D. Kaufman, Dating Deep Lake Sediments by Using Amino Acid Racemization in Fossil Ostracodes, Geology, 31, 1049 1052 (2003). 

A lake mixes on some time scale so it might be modeled as a stirred reactor for times longer than the mixing time, and it is a tubular reactor for shorter times. Most lakes turn over seasonally because of the density rrtirtimum of water at 4°C so they are mixed on at least a 1 year time scale. Small lakes are mixed effectively by wind on shorter time scales. Deep lakes exhibit an upper layer that turns over and mixes and a lower layer that does not. The inlets to a lake are aU the rivers that flow into it and also water coming from rainfall, and the outlets are aU the rivers that flow out of it and evaporatiorr... 

In Part IV we repeatedly used box models for describing the dynamics of chemicals in lakes. In this chapter we will summarize this information. As a first step, Fig. 23.1 illustrates the one-box model approach for the average total concentration of a chemical, Ct, in a well-mixed water body such as a pond, a shallow lake, a subcompartment of a deep lake or ocean (e.g., the mixed surface layer), or even an engineered system like a completely stirred reactor. 

Figure 3. Reconstructions of (A) diatom-based and (B) chrysophyte-based monomeric Al for Big Moose Lake, and diatom-based monomeric Al for (C) Deep Lake, (D) Upper Wallface Pond, and (E) Windfall Pond in the Adirondack Mountains, New York. Reconstructions are bounded by bootstrapping estimates of the root mean-squared error of prediction for each sample. Bars to the right of each reconstruction indicate historical (H) and Chaoborus-based (C) reconstructions of fishery resources. The historical fish records are not continuous, unlike the paleolimnological records. Intervals older than 1884 are dated by extrapolation. (Reproduced with permission from reference 10.

Frenzel P., Thebrath B., and Comad R. (1990) Oxidation of methane in the oxic surface layer of a deep lake sediment (Lake Constance). FEMS Microbiol. Ecol. 73, 149-158. 

Hauck S., Benz M., Brune A., and Schink B. (2001) Ferrous iron oxidation by denitrifying bacteria in profundal sediments of a deep lake (Lake Constance). FEMS Microbiol. Ecol. 37, 127-134. 

When water, as in a pond or lake, is healed by warm air above it, it remains stable, does not move, and forms a warm layer of w ater on (op of a cold layer, Consider a deep lake (1 = 0.6 W/m K,c = 4.179 kJ/kg K) that is initially at a uniform temperature of 2°C and has its surface tempeiature suddenly increased to 20°C by a spring weather front. The temperature of the water 1 m below the surface 400 hours after this change is... 

The following concentrations were measured in a 35-m deep lake during summer stagnation ... 

A third lake, Kivu in Rwanda, has been highlighted in a survey of deep lakes in Africa and Indonesia as another location where this type of disaster could happen from a massive geological event, that is, an earthquake or volcanic eruption. Lake Kivu was found to have high concentrations of dissolved CO2 in its bottom water, and is one of the largest and deepest lakes in Africa with two million people living on its shore. 

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