As I did not post previous week now we have bunch of interesting papers with various salt lakes studied. The range of lakes I mention below – from lake in Kenya with thousands of birds and wildlife around to salt lake/lagoon in Italy located in the city center and desert lake in Australia.
Papers we selected nicely demonstrate specific properties of salt lakes which make them interesting to study.
1. The level and salinity of many shallow lakes located in arid climate fluctuate which alters the species composition. It opens opportunity to paleolimnological research of sediment cores from saline lakes which links lake level, salinity, species composition with regional climate over the long period of time.
There are two perfect papers on this topic. One is on community turnover of water fleas (Daphnia) in response to environmental change in a fluctuating tropical lake Naivasha (Kenya). During the past 1800 years the habitat fluctuated between a small saline pond and a large freshwater lake.
First, results looks like bad news for those who consider salinity as a primer factor. The point is that the variance in community composition explained by changes in three important habitat conditions (lake depth, salinity, fish abundance) was relatively modest. What was important to explain species composition is the priority effect which explained, especially for the high water level, a much higher portion of variance in community composition than environmental change. However for the lowstands (shift from freshwater to saline habitat) priority effects decayed rapidly with time as Daphnia communities responded to environmental change.
The second paper reconstructs palaeosalinity records for lakes in the southwest Murray Basin from complex evidences including remainings of ostracod, diatom, charophyte, gastropod, foraminifera, Cladocera, and brine shrimp faecal pellets.
The records obtained at two lakes provide a detailed account of Holocene changes in salinity and precipitation in the region. Salinity decreased around 9600 yr and reached its Holocene minimum between 8900 and 5700 yr. Detected low-salinity events at 8800, 7200, 5900, 4800, 2400, 1300 and 400 yr are similar in timing and number to those recorded on Australia’s southern continental shelf, and globally, and support the existence of the ~1500-yr cycle in mainland southern Australia.
2. Small and relatively deep salt lakes very often become meromictic when mixing is prevented by the salinity gradient located at the specific depth. Such lakes offer unique habitats for microbial communities. The food web in meromictic lakes very often is reduced and the microbial communities inhabiting the salinity gradient plays important role in the overall productivity budget of the lake.
The paper I will mention is typical for studies of such ecosystems. Authors determine the vertical distribution of archaea and bacteria in a coastal saline meromictic Lake Faro (Messina,Italy).
The transition zone between oxic (mixolimnion) and anoxic (monimolimnion) layers in this lake located at the depth of 15 m. Bacteria decreased from surface to bottom. Archaea increased with depth and reached the maximum value at 30 m. At the chemocline high numbers of prokaryotic cells were present, mainly represented by Cyanobacteria, Chromatium okenii and Euryarchaeota, green sulfur bacteria and sulfate reducing bacteria, and Crenarchaeotaprevailed below the chemocline.
The research may be considered as routine. However what is interesting is an example of meromictic lake located at the populated area and loaded with aquaculture. Most probably many people living there have no idea on the complex structure of bacterial community in the depth of lake they exploited.