Extremophilic Life in Our Oceans as Models for Astrobiology

Earth harbors vast ecosystems that support life (psychrophilic, barophilic and chemosynthetic) adapted to conditions that may occur on other planets in the universe. We define organisms that inhabit severe ecosystems as extremophiles whether this life persists on Earth or other planets. The Southern Ocean harbors marine life which has adapted to near-freezing conditions, coupled with new low oxygen zones that can lead to hypoxic zones as in the upwelling low-latitude areas of the eastern edges of the world's oceans. In my research in the Southern Ocean around Antarctica, I encountered austral summer blooms of diatoms and vast biomass of krill aggregations (swarms) along the western Antarctic Peninsula (WAP); but now krill and its predators (penguins, baleen whales and seals) are threatened by the rapid warming of recent decades and further adversely impacted by formation of low pH and low oxygen zones in the deep water column of the Amundsen Sea, where ice shelves melted (1973–2003), creating the new Elizabeth City State University Bay. Secondly, in the past four decades we have also discovered unique hydrothermal warm deep-sea chemosynthetic communities and cold seepage ecosystems with peculiar marine life adapted to a toxic marine environment. This chapter discusses how life originated, and comments on the evolution of life that perhaps exists on planets other than Earth. A third ecosystem discussed in this chapter is the so-called ultra-abyssal or hadal zone that supports unique fauna in extreme depths (6,000–10,000 meters) and, therefore, under perpetual hyperbaric conditions in the trenches of the world's oceans. This chapter also focuses on the Puerto Rico Trench, the only trench in the North Atlantic Ocean. Climate-change-induced processes may even slow down major ocean currents such as the Antarctic bottom water (AABW) flowing into the lower hadal or ultra-abyssal zone at a depth greater than 8000 meters in the Puerto Rico Trench, with potential creation of hypoxic hadal zones at extreme ocean depths.