Shallow lakes

There is a further complication in shallow lakes containing macrophytes (aquatic flowering plants, pteridophytes, and macroalgae). These take up and accumulate nutrients from the water and from the aquatic soil in which they are rooted (sediment). Although these plants are sometimes classed as nuisance weeds, they nevertheless act as an important alternative sink for nutrients which are denied to the plankton. In recent times, a key role of macrophytes in the successful and sustained management of water quality has been identified and explained. ... 

In smaller shallow lakes, where the internal re-cycling of phosphorus can be... 

It is becoming increasingly clear that, in shallow lakes which have high rates of phosphorus sediment re-cycling, bio-manipulation is an essential element of successful restoration. 

Observations of the ratio of oxidized plutonium to reduced plutonium may provide some insight to the observations of erratic formation and lack of equilibration in laboratory solutions at ORNL versus fairly consistent and predictable behavior in oligo-trophic lakes and marine systems. In coastal water and the relatively shallow Lake Michigan, Pu(V) is about 90 percent of the soluble plutonium, but in the upper waters of the open ocean, where it does not interact with the seafloor due to the depths,... 

In 1968, reports from Sweden, subsequently confirmed in other industrial countries, noted that shallow lakes with low concentrations of divalent cations were becoming more acidic with consequent decreases in aquatic plants and animals. In severely affected lakes and ponds, only acidophilic algae survived. Increased acidity and the runoff of solubilized aluminum and other metal ions from surrounding watersheds are now known to be primarily responsible for formation of these almost sterile bodies of water. 

Carvalho L, Kirika A (2003) Changes in shallow lake functioning response to climate change and nutrient reduction. Hydrobiologia 506 789-796... 

The Ebro headwaters flow on calcareous substratum, specifically sandstone and calcium marls, from the Triassic, Cretacic, and Jurassic. During the Quaternary, at the plain of La Virga (Reinosa), a shallow lake accumulated the deposits of siliceous sandrocks. This old highland lake is now the Embalse del Ebro reservoir. From that point downstream to Conchas de Haro the main channel flows on calcareous rocks from the Cretacic, highly resistant to the erosion. 

Shallow lakes are open water bodies a few metres deep. Only considered foe temperate and tropical regions in polar and boreal regions it is difficult to separate shallow lakes from bogs and fens. 

This model qualitatively explains the deviation of isotopic compositions away from the Meteoric Water Line because molecular diffusion adds a non-equilibrium fractionation term and the limited isotopic enrichment occurs as a consequence of molecular exchange with atmospheric vapor. It is mainly the humidity which controls the degree of isotope enrichment. Only under very arid conditions, and only in small water bodies, really large emichments in D and are observed. For example, Gonfiantini (1986) reported a 5 0-value of +31.3%c and a 8D-value of +129%c for a small, shallow lake in the western Sahara. 

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. 

In most of the study lakes organic content is poorly correlated with lake depth, a feature that may be partially attributed to the fact that fine-grained sediments are only weakly focused in small shallow lakes (6, 18). Indeed, sediments do become somewhat more organic with depth in the two deepest lakes, Thrush and Kjostad. The perception of uniform sediment composition also results from sampling bias, because few littoral cores were actually retained for analysis. Visibly inorganic sediments were assumed to represent nondepositional sites for purposes of calculating a Hg flux and were simply mapped and discarded. 

To attain the same level of accuracy, large or steep-sided basins with heterogeneous sediments may require 4 times the number of cores needed for small shallow lakes with more uniform sediments. 

Annual isotopic variation is substantial in shallow lakes with relatively short residence times. These variations reflect the dominance of summer evaporation and spring snowmelt. In addition, these variations may prove useful for examining atmospheric exchange rates with lakes and for quantifying periods of episodic water input. 

Factors Controlling Rates of Sulfate Reduction. Factors typically cited as controlling sulfate reduction include temperature, sulfate concentration, and availability of carbon substrates. Although sulfate-reducing bacteria typically exhibit steep responses to temperature (rates increase 2.4- to 3.7-fold per increase of 10 °C 85, 101, 105), neither differences between deep and shallow lakes (Table I) nor seasonal variation have been observed in rates of sulfate reduction (78, 85, 101). This apparent lack of response of sulfate reduction rates to changes in temperature may indicate that rates are limited by other factors. 

BORAX. This hydrated sodium borate mineral, NaiBtOy 101 1, O, is a product of evaporation from shallow lakes and plays. Borax crystallizes in the monoclinic system, usually in short prismatic crystals. Its color grades from colorless through gray, blue to greenish. Vitreous to resinous luster of translucent to opaque character. Hardness of 2-2.5, and specific gravity of 1.715. 

The electrolysis of saturated sodium chloride solution (brine) is the basis of a major industry. In countries where rock salt (sodium chloride) is found underground it is mined. In other countries it can be obtained by evaporation of sea water in large shallow lakes. Three very important substances are produced... 

Reitner, B., G. J. Herndl, and A. Herzig. 1997. Role of ultraviolet-B radiation on photochemical and microbial oxygen consumption in a humic-rich shallow lake. Limnology and Oceanography 42 950-960. 

Because of the high area of solid surfaces covered with biofilms, these biofilms dominate the heterotrophic metabolism in many aquatic ecosystems. In streams, rivers, and shallow lakes, bacterial activity in epilithic and epiphytic biofilms may be several times higher on an areal basis than the activity of free living bacteria. By the differential use of specific DOM fractions, biofilm bacteria influence the biogeochemical composition of DOM in these ecosystems. Biofilms thus can control biogeochemical fluxes of DOM and are important sinks of organic matter. 

Theil-Nielsen, J., and M. Sondergaard. 1999. Production of epiphytic bacteria and bacterio-plankton in three shallow lakes. OIKOS 86 283—292. 

Scheffer M. 1998. Ecology of shallow lakes. London (UK) Chapman Hall, 357 p. 

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