*Lagoon Environments around the World - A Scientific Perspective*

the *Artemia*-gut microbiota composition. The phylum Bacteroidetes was the most common in brines of both lagoons in agreement with the study described earlier [30]. Proteobacteria and Cyanobacteria (de la Sal lagoon) were less represented. At the genus level, the diversity is high, *Psychroflexus* predominating, though a significant diversity remains unidentified. The microbiota of individuals collected in Cisnes lagoon contains a reduced amount of Bacteroidetes, whereas the proportion of Proteobacteria and Firmicutes is higher. The most frequent genera in the *Artemia* gut of Cisnes lagoon individuals are *Halolactobacillus*, *Psychroflexus*, *Halomonas*, and *Vibrio*, a pattern similar to that previously described [30]. The observation that some bacteria present in the gut of *Artemia* individuals are in low frequency in the environment, or not found, supports the idea that in some polyextremophile environments like Salar de Atacama, microbial habitats are serving as a refuge, i.e.,

#### **Figure 4.**

*Bacterial diversity in brines of Patagonian lagoons De la Sal and Cisnes and bacterial communities in the Artemia gut of individuals from Cisnes lagoon (bottom).*

**65**

quorum sensing [46].

*Hypersaline Lagoons from Chile, the Southern Edge of the World*

in natural brines such as *Halomonas* and *Halolactobacillus*.

the so-called endolithic habitats [38]. From data in **Figure 4**, it is possible to think that the *Artemia*-gut microbiota could also serve as a refuge to bacteria uncommon

**4. The salt-lover brine shrimp** *Artemia***: adapted to critical life conditions**

The brine shrimp *Artemia* is a branchiopod crustacean well adapted to the harsh conditions of hypersaline environments impose on survival and reproduction and hence is considered a model extremophile or a salt-lover sensu Wharton [39]. It displays remarkable adaptations at different domains, one of the most striking being a highly efficient osmoregulatory system to withstand high salinities (up to 340 g/L) [6]. Also, *Artemia* females can perceive when the environment becomes suboptimal, an ability that makes *Artemia* an indicator of ecosystem quality. Under suboptimal conditions, i.e., when a shallow lagoon dries up, females switch to produce encysted offspring (oviparity), in other words, cysts or diapause embryos highly resistant to extreme conditions. Instead, offspring in the form of free-swimming nauplii (ovoviviparity) allows rapid population expansion under optimal environmental conditions. The cyst shell protects from UV irradiation, large temperature fluctuations, osmotic pressure, dryness, and other stresses, so cysts remain viable practically dehydrated [40–42]. Such evolutionary solution for populations to escape extinction when conditions become unfavorable suggests that cysts contain a memory of the past [6] that can be retrieved when cyst resurrect (sensu [43]) either naturally or experimentally, i.e., resume metabolic activity and hatch once the environment returns to normal. Since cysts deposited in saline lagoons at different times accumulate at shores and all have the chance to hatch at the same time when the environment allows it, females face a critical mating decision of choosing the right male to maximize their reproductive output. They can mate either contemporary males (hatched from cysts of the same age), males from the past (hatched from older cysts), or males from the future (hatched from more recent cysts). Females tend to select contemporary males, which would be a demonstration of male-female coevolution [44]. The sophisticated mate choice behavior of *A. franciscana* would be a consequence of such coevolution [45]. The question of how females perceive in advance when conditions will become unfavorable remains unclear, but it would be reasonable to advance the hypothesis that bacterial communication (quorum sensing) to maintain their functional diversity in extreme ecosystems could be involved. This is possible as bacteria interact with all kind of life forms in a given ecosystem, and such interaction may affect the adaptation of other species. For example, the microalgae *Dunaliella salina*, commonly found in saline environments, responds to

In Chile, two out of the six regionally endemic and highly divergent sexual species co-occur, *A. franciscana* Kellogg, 1906 and *A. persimilis* Piccinelli and Prosdocimi, 1968 [6, 24]. The latter was previously thought endemic to Argentina, though it is now clear that inhabits Chilean Patagonia lagoons [47, 48]. Both species are segregated by a latitudinal barrier coincidently with their differential ability to colonize and cope with different environments, which is the case of *A. franciscana*, the most widely distributed of all, and considered a younger species in evolutionary expansion [24]. The species inhabits lagoons of the Atacama Desert in northern Chile, which is the southern limit of a broad north-south distribution in the Americas (North, Central, South). Instead, *A. persimilis* is restricted to Patagonia, with a probable hybrid zone between both species in solar saltworks of central Chile [49, 50]. Other sexual species are restricted to the Mediterranean area (*A. salina*), Lake Urmia and some lakes in Ukraine (*A. urmiana*), China (*A. sinica*), and Tibetan Plateau

*DOI: http://dx.doi.org/10.5772/intechopen.88438*

*Lagoon Environments around the World - A Scientific Perspective*

the *Artemia*-gut microbiota composition. The phylum Bacteroidetes was the most common in brines of both lagoons in agreement with the study described earlier [30]. Proteobacteria and Cyanobacteria (de la Sal lagoon) were less represented. At the genus level, the diversity is high, *Psychroflexus* predominating, though a significant diversity remains unidentified. The microbiota of individuals collected in Cisnes lagoon contains a reduced amount of Bacteroidetes, whereas the proportion of Proteobacteria and Firmicutes is higher. The most frequent genera in the *Artemia* gut of Cisnes lagoon individuals are *Halolactobacillus*, *Psychroflexus*, *Halomonas*, and *Vibrio*, a pattern similar to that previously described [30]. The observation that some bacteria present in the gut of *Artemia* individuals are in low frequency in the environment, or not found, supports the idea that in some polyextremophile environments like Salar de Atacama, microbial habitats are serving as a refuge, i.e.,

*Bacterial diversity in brines of Patagonian lagoons De la Sal and Cisnes and bacterial communities in the* 

**64**

**Figure 4.**

*Artemia gut of individuals from Cisnes lagoon (bottom).*

the so-called endolithic habitats [38]. From data in **Figure 4**, it is possible to think that the *Artemia*-gut microbiota could also serve as a refuge to bacteria uncommon in natural brines such as *Halomonas* and *Halolactobacillus*.
