Environmental Engineering Reference
In-Depth Information
Figure 3.
Typical depth profile of water chemistry of the Black Sea, from data collected at
different times and stations, based on Millero [80]. Profiles indicated vary with depth depending
upon the sampling location. The profile shows typical distributions of water chemistry parameters
important for N
2
fixation.
sediment deposits, sapropels, also indicate that blooms of rhizosolenid diatoms
that can harbor endosymbiotic N
2
-fixing cyanobacteria have co-occurred with
the anoxic periods [109]. Endosymbiotic diazotrophs could be an important
source of new nitrogen into the Mediterranean Sea [24].
6.3 Mono Lake
Mono Lake is a hypersaline alkaline lake that may mimic life on early Earth.
For many years, Mono Lake was meromictic (Fig. 4), with an oxycline that
was within the photic zone and a chemocline that was below the photic zone.
Productivity in the lake is believed to be nitrogen limited, but below the oxycline
there are high concentrations of ammonia/ammonium [56].
Diverse N
2
-fixing microorganisms are found throughout the oxic and anoxic
portions of the Mono Lake's water column [123].
NifH
genes found in Mono
Lake include a relatively high abundance of genes grouping with Cluster III
nifH
genes, including many anaerobes (Fig. 1). Many
nif
genes that clustered
with genes from sulfate reducers, clostridia, and green sulfur bacteria were
