**1. Introduction**

Hypersaline lakes or brines (over 40 g/L) [1] are unique ecosystems with unique extremophile biodiversity and scientific value, which also have economic, esthetic, cultural, and recreational value [2, 3]. They represent a significant volume (~45%) of inland waters [4] and hence are essential components of the biosphere, mostly located in arid and semiarid regions around the world where high evaporation rates exceed rainfall. However, they also occur in unusually cold places such as Tibet in China and Patagonia in southern Chile and Argentina [5, 6]. Due to their wide ecological diversity related to their coastal (thalassohaline) or inland origin (athalassohaline) [7, 8], altitude, salinity, and island-like distribution, these lagoons display unique extreme biodiversity and limnological features. Besides, hypersaline lagoons are also affected by the combined effect of multiple stressors such as UV exposure, temperature, pH, low nutrient, and oxygen availability [8], which means these lagoons are polyextremophile environments. As a consequence, the microscopic and macroscopic biodiversity reflects their evolution to cope with multiple stresses that are unbearable for most organisms.

Since biodiversity declines as salinity increases, hypersaline lagoons are relatively low-diversity ecosystems with simple food webs [9] and hence are considered suitable natural laboratories [10] to address fundamental questions of biology. Due to the multiple stressors shaping such unique biodiversity and the potent mutagenic role variation in ionic strength has on DNA-protein interactions, and protein structure, the biodiversity of these lagoons exhibits an accelerated rate of evolution, at least as demonstrated for brine shrimps (*Artemia*) [11]. Among the relevant biological questions salty ecosystems allow to investigate are those related to the origin of life from simple forms, and what are the limits and prominent features of life in extreme environments, topics addressed by the new discipline of astrobiology [12]. Likewise, what is the microbiological and macroscopic (zooplanktonic) diversity salty lagoons harbor, and how latitudinal, climatic, lagoon-specific conditions, or anthropic perturbations modulate such diversity? Their microbiological diversity has received significant attention due to the potential economic benefits attached to the metabolic responses evolved to cope with extreme conditions (antioxidant pigments, hydrolytic enzymes) [13–15]. While the stress response in the prokaryotic world tends to be unidimensional, multicellular systems experience critical life conditions at all levels of functionality; in other words, adaptation takes place at different domains, from the individual (molecular-cellular-physiological) to the population level. As discussed later on in this chapter, the brine shrimp *Artemia* is a relevant extremophile model to understand what means to survive and reproduce under harsh conditions [6].

From a more practical perspective, hypersaline lagoons are considered lowdiversity natural laboratories to understand how simple ecosystems function to provide economic services like mining salt and brine shrimp (*Artemia*) biomass, like in the Great Salt Lake in Utah, an example of a well-managed lake to allow the coexistence of economic and noneconomic services like waterbird habitat. The lake is the main source of *Artemia* cysts for world aquaculture [16], but the *Artemia* biomass required to harvest tonnes of cysts also attracts local and migratory waterbirds that need to be protected, some of which are endangered [17, 18]. Hypersaline lakes and lagoons around the world are, however, shrinking at an alarming rate due to climate oscillations and water or brine diversion for mining [19]; hence, there is a need to conserve their unique biodiversity, properties, and services to comply with international treaties on biodiversity, ecosystem, and wetland conservation. The lack of systematic and long-term spatial and temporal studies on most hypersaline ecosystems that are often in remote places and tend to exhibit high seasonal variation in their biodiversity [9] makes difficult to understand or predict how they will respond to climate oscillations and increased anthropic pressures.

The importance of saline lakes and lagoons in the twenty-first century was highlighted by Williams [3], who in 2003 predicted they would be shrinking by 2025. Other reviews have also highlighted the fragility of these unique ecosystems [2, 4], while recent literature pinpoints the biotechnological importance of the microbiological diversity they harbor [12–15] as an argument to protect them [14]. This chapter focusses on Chilean hypersaline lagoons (or Lagunas) located at contrasting latitudinal and altitudinal settings at the southern edge of the world, i.e., southwest of South America (below 18° latitude south). In the north, inland (athalassohaline) lagoons are an integral part of mineral-rich evaporitic basins or salars (salt crusts) scattered at different altitudes in the hyperarid Atacama Desert. The aridity of the desert has raised the question if life can persist in water-less environments, and because of this and other soil characteristics, the desert is considered a terrestrial model of Mars and hence a target of astrobiological research as already mentioned.

**59**

agriculture and other sources.

**of the world**

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

Instead, in Patagonia, there are subantarctic low-altitude lagoons, some of which are relatively close to the Pacific coast but cannot strictly be considered thalassohaline. The unique feature of these hypersaline lagoons is their location in an area where freshwater lakes of glacier origin abound. Both contrasting latitudinal settings represent useful case studies to address how their prokaryotic and eukaryotic diversity evolved. The brine shrimp *Artemia*, a key taxon in the food web of these salty lagoons, becomes relevant in the discussion on how these lagoons function to provide suitable habitat for waterbirds, as the abundance of this crustacean seems to be a good predictor of their presence [17] and the animal is also considered an indicator of environmental quality. In this context, some of the remarkable animal's adaptations are discussed, including the sort of symbiotic *Artemia*-bacteria relationship and other factors affecting *Artemia* fitness and hence the abundance of this crustacean. The aims of this chapter are as follows: (1) To provide a glimpse to the ecological characteristics of hypersaline lagoons of Chile, which are unique ecosystems located at contrasting latitudinal edges. They are a natural heritage harboring unique extremophile biodiversity that provides conditions to host a significant waterbird diversity. (2) To review studies on their microbiological communities that coexist with *Artemia*. (3) To get insights on *Artemia* species inhabiting such contrasting environments, and their ability to tolerate high salt concentration (salt-lover), and to perceive ecosystem quality. The *Artemia*-bacteria interaction is also discussed as it contributes to *Artemia* fitness and abundance. (4) To highlight the need to monitoring hypersaline lagoon dynamics on a long-term basis to predict waterbird presence. (5) To alert on the fragility of these ecosystems increasingly affected by climatic oscillations and human-driven perturbations like mining.

**2. Hypersaline lagoons from Chile: natural heritage at the southern edge** 

Chile is a sort of biogeographical island at the southern edge of the world, isolated by the hyperarid Atacama Desert on the north, the Antarctic ice on the south, the Andes Mountains on the east, and the Pacific Ocean on the west. This long and narrow land (**Figure 1**) exhibits a wide latitudinal (18°–56°S latitude, excluding the Antarctic) and altitudinal range, from sea level to the high Andes. Natural hypersaline lagoons or brines exist at both latitudinal and climatological extremes. The Atacama Desert (17°–27°S latitude) is the driest, oldest, and most extreme world environment [20, 21], wellknown as a terrestrial Mars analog, as already mentioned, with microbial life similar to what could be expected to exist in the red planet [21, 22]. This desert contains numerous inland athalassohaline lagoons (**Figure 1A** and **B**), i.e., with salt proportions different from seawater [7, 8], which are an integral part of different evaporitic basins, salars, or salt crusts, located at different altitudes, just to name a few: Salar de Llamará (21°18′S, 69°37′W) at 850 m; Salar de Atacama (23°30′S, 68°15′W) over 2300 m, the largest in

68°50′W), a protected National Park and Ramsar site at 4000 m; and Salar de Surire (18°48′S, 69°04′W) at 4245 m. Only Andean countries like Perú, Bolivia, Argentina, and Chile share the geomorphological, climatic and hydrological conditions that

The Chilean Patagonia belongs to the administrative region of Magallanes and Chilean Antarctica. This steppe-like landscape with cold, semi-humid climate and very windy condition are characteristic of this region where few lagoons exist. Although some are close to the coast such as Laguna Cisnes (**Figure 1D**), it is difficult to classify it as thalassohaline (marine origin) [8] due to mineral runoff from

); Salar de Huasco (20°18′S,

the Altiplano-Puna region of the Central Andes (~3000 km2

originated these salars and hypersaline lagoons [7, 20–23].

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