Hidden Worlds Beneath the Waves

 Hidden Worlds Beneath the Waves 🌊

                                                                                    The  majority of Earth's active volcanoes are situated underwater. Submarine eruptions, which most frequently take place around tectonic spreading centers, unleash molten rock from beneath the bottom. Underwater volcanoes are fascinating geological features that lie beneath the ocean's surface. These volcanoes can have significant impacts on both the marine environment and the Earth's atmosphere. 

One notable example is the Hunga Tonga-Hunga Ha’apai eruption in January 2022. This underwater volcano in the South Pacific Ocean erupted with such force that it sent a massive plume of water vapor into the stratosphere, enough to fill more than 58,000 Olympic-size swimming pools. The eruption also caused a tsunami and a sonic boom that circled the globe twice.  

The eruption of the Krakatoa volcano in 1883 remains one of the deadliest underwater eruptions in history, highlighting the destructive power of these natural phenomena.

Over time, repeated volcanic eruptions can build up enough material to form islands. Famous examples include the Hawaiian Islands and Iceland, which were formed by underwater volcanic activity. 

Hydrothermal vents are fissures on the seabed from which geothermally heated water discharges. They form when seawater seeps into the Earth's crust, gets heated by underlying magma, and then rises back to the ocean floor, carrying dissolved minerals with it. The temperature of the water emitted from hydrothermal vents can reach up to 400°C (752°F). Despite this, the surrounding water, just a few meters away, remains near freezing due to the deep ocean's cold temperatures.

Vents that emit dark, mineral-rich water that forms chimney-like structures made of iron sulfide, giving them their black color are called black smokers, and vents that release lighter-colored minerals like barium, calcium, and silicon, resulting in white deposits, are called white smokers.

Volcanoes and vent sites, albeit they are in places too dark for sunlight to drive food production, extinct, or even moderately active, frequently harbor a variety of animal populations that have adapted to use chemical energy, a process known as chemosynthesis to make food. The base of the food web around underwater volcanoes is primarily composed of chemosynthetic bacteria and archaea. Also, hydrothermal vents release nutrient-rich fluids that support dense microbial communities. These microbes form biofilms and mats on the vent surfaces and in the surrounding sediments. Chemosynthetic bacteria use chemicals such as sulfides and methane as a source of energy to produce organic material. Chemosynthetic bacteria are then grazed on by heterotrophs, which in turn are eaten by larger predators. Some of these bacteria even live inside vent fauna (such as tube worms and Bathymodiolus mussels) or grow on specialized appendages.

Many larger organisms, such as tube worms, clams, and mussels, have symbiotic relationships with chemosynthetic bacteria. These bacteria live within the tissues of their hosts and provide them with nutrients. 

Green sulfur bacteria are unique among hydrothermal vent bacteria because they require both chemical energy (from hydrogen sulfide) and light energy to survive. Green sulfur bacteria contain chlorosomes, organelles that are so efficient at harvesting light that green sulfur bacteria can grow at much lower light intensities than other light-requiring microbes. There is no sunlight at hydrothermal vents and instead, they capture energy from the weak radioactive glow emitted from geothermally heated rock. 

Animals are present in very high abundances, but there tends to be lower diversity, with communities being dominated by only a few taxa.

The organisms living around underwater volcanoes and hydrothermal vents have developed unique adaptations to survive in high-pressure, high-temperature, and low-light conditions. For example, some species of shrimp and crabs have specialized heat-resistant enzymes. 

Underwater volcanic activity can have a significant impact on global ocean chemistry. Underwater volcanic activity releases carbon dioxide into the ocean. While some of this carbon dioxide is absorbed by seawater, contributing to ocean acidification, it also plays a role in the global carbon cycle, influencing the Earth's climate over geological timescales. The minerals and chemicals released by hydrothermal vents and underwater volcanoes can alter the chemical composition of seawater. This impact is particularly notable in the deep ocean, where these features contribute to the distribution of elements like sulfur, iron, and silica. Hydrothermal vents release a variety of minerals and gases, including iron, sulfur, and methane, into the ocean. These substances are critical for nutrient cycling in the deep sea, supporting the growth of microorganisms and, consequently, the entire ecosystem.

Many underwater volcanoes are found along mid-ocean ridges, where tectonic plates are moving apart. The volcanic activity here contributes to seafloor spreading, a process that constantly renews the ocean floor and plays a crucial role in plate tectonics. The unique organisms found in hydrothermal vent ecosystems produce novel compounds that have potential applications in medicine. For example, enzymes from these organisms have been used in biotechnology, and there is ongoing research into their potential use.

Exploring hydrothermal vents is so exciting because it teaches us about the limits of life, organisms living there have to deal with mind-boggling extremes of temperature and chemistry. 

📝Dilhari Pussawala 

3rd  year (20/21 batch)

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