9.3 Deep-sea paleoecology and chemosynthetic communities
3 min read•august 7, 2024
Deep-sea ecosystems are fascinating worlds hidden beneath the waves. From to , these environments host unique life forms adapted to extreme conditions. , not sunlight, fuels these communities.
The deep sea is divided into distinct zones, each with its own challenges. As we descend, pressure increases, light fades, and temperatures plummet. Yet life finds a way, with bioluminescence lighting up the darkness.
Chemosynthetic Ecosystems
Hydrothermal Vents and Cold Seeps
Top images from around the web for Hydrothermal Vents and Cold Seeps
Frontiers | Microbially Mediated Hydrogen Cycling in Deep-Sea Hydrothermal Vents View original
Is this image relevant?
Frontiers | Comparative Study of Guaymas Basin Microbiomes: Cold Seeps vs. Hydrothermal Vents ... View original
Is this image relevant?
BG - On the formation of hydrothermal vents and cold seeps in the Guaymas Basin, Gulf of California View original
Is this image relevant?
Frontiers | Microbially Mediated Hydrogen Cycling in Deep-Sea Hydrothermal Vents View original
Is this image relevant?
Frontiers | Comparative Study of Guaymas Basin Microbiomes: Cold Seeps vs. Hydrothermal Vents ... View original
Is this image relevant?
1 of 3
Top images from around the web for Hydrothermal Vents and Cold Seeps
Frontiers | Microbially Mediated Hydrogen Cycling in Deep-Sea Hydrothermal Vents View original
Is this image relevant?
Frontiers | Comparative Study of Guaymas Basin Microbiomes: Cold Seeps vs. Hydrothermal Vents ... View original
Is this image relevant?
BG - On the formation of hydrothermal vents and cold seeps in the Guaymas Basin, Gulf of California View original
Is this image relevant?
Frontiers | Microbially Mediated Hydrogen Cycling in Deep-Sea Hydrothermal Vents View original
Is this image relevant?
Frontiers | Comparative Study of Guaymas Basin Microbiomes: Cold Seeps vs. Hydrothermal Vents ... View original
Is this image relevant?
1 of 3
- Hydrothermal vents form along mid-ocean ridges where tectonic plates are spreading apart and magma rises close to the seafloor
- Seawater seeps into cracks in the seafloor, becomes superheated by magma, and rises back to the surface through hydrothermal vents (black smokers)
- Vent fluid is rich in dissolved minerals and chemicals like hydrogen sulfide
- Cold seeps occur where methane and other hydrocarbons slowly leak from sediments on the seafloor
- Methane can originate from decomposing organic matter or from methane hydrates (ice-like substances composed of methane trapped within a crystal structure of water)
- Cold seeps often form along continental margins and in areas with thick sediment deposits (Gulf of Mexico)
Chemosynthesis and Extremophiles
- Chemosynthesis is the process by which certain microbes convert chemical energy from inorganic compounds into organic matter
- Chemosynthetic microbes form the base of the food web in hydrothermal vent and cold seep ecosystems
- Chemosynthesis does not require sunlight, unlike photosynthesis
- Extremophiles are organisms adapted to extreme environments like the high temperatures, high pressures, and toxic chemicals found in hydrothermal vents and cold seeps
- Chemosynthetic bacteria and archaea are examples of extremophiles that thrive in these harsh conditions
- Many extremophiles are anaerobic, meaning they do not require oxygen to survive
Unique Fauna of Chemosynthetic Ecosystems
- Tube worms (Riftia pachyptila) are iconic inhabitants of hydrothermal vents in the Pacific
- Tube worms lack a mouth and digestive system and instead rely on chemosynthetic bacteria living in their tissues for nutrition
- Tube worms can grow up to 2 meters in length and live in dense clusters around vent openings
- Giant clams (Calyptogena magnifica) are common in cold seep communities
- These clams host chemosynthetic bacteria in their gills which provide them with food
- Giant clams can reach over 25 cm in length and live for over 100 years
- Other unique fauna in chemosynthetic ecosystems include:
- Yeti crabs (Kiwa hirsuta) which farm chemosynthetic bacteria on their claws
- Pompeii worms (Alvinella pompejana) which are extremophiles that can withstand temperatures up to 80°C
Deep-Sea Zones
Bathyal Zone
- The bathyal zone extends from 200 to 2,000 meters below sea level and includes the continental slope and rise
- Temperature, pressure, and light levels vary greatly within the bathyal zone
- Temperatures range from 4-20°C depending on depth and location
- Pressure increases by about 1 atmosphere every 10 meters of depth
- Light levels decrease rapidly with depth, with the lower bathyal zone receiving no sunlight
- Biodiversity and biomass generally decrease with depth in the bathyal zone, but there are exceptions like whale fall communities and cold seep ecosystems
Abyssal Zone
- The abyssal zone extends from 2,000 to 6,000 meters below sea level and includes the vast, flat abyssal plains that cover much of the deep ocean floor
- The abyssal zone is characterized by relatively uniform environmental conditions
- Temperatures are constantly near freezing (0-4°C)
- Pressures exceed 200 atmospheres
- No sunlight penetrates to abyssal depths, resulting in a region of permanent darkness
- Despite the challenges of living in the abyssal zone, a surprising diversity of life can be found here
- Abyssal organisms are adapted to the constant cold, high pressure, and lack of light and primary production
- Many abyssal animals like sea cucumbers and brittle stars rely on detritus raining down from above as their main food source
Bioluminescence in the Deep Sea
- Bioluminescence is the production and emission of light by living organisms
- Over 90% of animals in the bathyal and abyssal zones are bioluminescent
- Bioluminescence is used for a variety of purposes including attracting prey, deterring predators, and finding mates in the darkness
- Examples of bioluminescent deep-sea organisms include:
- Anglerfish which use a bioluminescent lure to attract prey
- Vampire squid which emit a cloud of bioluminescent particles to confuse predators
- Lanternfish which have bioluminescent photophores along their bellies for counterillumination camouflage against predators looking up from below
Key Terms to Review (18)
Anoxia Tolerance: Anoxia tolerance refers to the ability of certain organisms to survive and function in environments with little to no oxygen. This capability is particularly significant in deep-sea habitats where oxygen levels can be extremely low or absent, impacting the types of life forms that can thrive there. Understanding anoxia tolerance is essential for studying ecosystems that rely on chemosynthesis, as many organisms in these communities have adapted to live under such extreme conditions.
Benthic oxygen isotopes: Benthic oxygen isotopes refer to the ratios of oxygen isotopes (primarily $$^{16}O$$ and $$^{18}O$$) found in the calcified structures of organisms that live on or near the seafloor. These isotopes are crucial for reconstructing past ocean temperatures, salinity, and other environmental conditions, helping scientists understand the history of deep-sea ecosystems and chemosynthetic communities.
Carbon cycling: Carbon cycling refers to the continuous movement of carbon atoms through various reservoirs, including the atmosphere, oceans, soil, and living organisms. This process is essential for maintaining the balance of carbon in the environment and plays a crucial role in regulating Earth's climate. Understanding carbon cycling helps illustrate how different ecosystems, particularly in marine settings, interact and respond to changes over time.
Chemosynthesis: Chemosynthesis is the biological process through which certain organisms convert inorganic compounds, such as hydrogen sulfide or methane, into organic matter using chemical energy, rather than sunlight. This process is crucial for sustaining life in extreme environments, particularly in deep-sea ecosystems where sunlight does not penetrate, and forms the foundation of chemosynthetic communities that thrive around hydrothermal vents and cold seeps.
Cold seeps: Cold seeps are areas on the ocean floor where fluids such as methane and hydrogen sulfide seep up from beneath the Earth's crust, creating unique environments that support specialized ecosystems. These ecosystems are characterized by chemosynthetic organisms that derive energy from the chemicals in the seep, forming communities distinct from those found in sunlight-driven ecosystems.
Foraminifera: Foraminifera are a group of single-celled protists characterized by their intricate shell-like structures called tests, which are often made of calcium carbonate. They play a crucial role in paleoecology as they provide valuable insights into past environmental conditions and can be used as biological proxies to interpret historical climate changes and marine ecosystem dynamics.
Hydrothermal vents: Hydrothermal vents are underwater geysers that release heated, mineral-rich water from the Earth's crust, typically found along mid-ocean ridges. These vents create unique ecosystems that support diverse life forms, primarily through chemosynthesis, which relies on chemical reactions rather than sunlight for energy.
Methanogenic Archaea: Methanogenic archaea are a group of microorganisms that produce methane as a metabolic byproduct in anoxic conditions. These organisms play a crucial role in deep-sea ecosystems, particularly in chemosynthetic communities, where they contribute to carbon cycling and support various life forms by providing an energy source through methane production.
Oceanic ridges: Oceanic ridges are underwater mountain ranges formed by the tectonic processes associated with seafloor spreading at divergent plate boundaries. These features play a critical role in shaping ocean basins and are hotspots for unique ecosystems, particularly chemosynthetic communities that thrive in extreme conditions.
Primary Producers: Primary producers are organisms that can produce their own food through photosynthesis or chemosynthesis, serving as the foundational level of the food web. In deep-sea environments, these organisms, particularly certain bacteria and archaea, harness chemical energy from inorganic compounds to create organic matter, supporting entire ecosystems that thrive in extreme conditions.
Sediment composition: Sediment composition refers to the specific materials that make up sediment, including mineral particles, organic matter, and chemical precipitates. Understanding sediment composition is crucial as it influences the physical and chemical properties of sedimentary environments, such as water retention, nutrient availability, and the types of organisms that can thrive in these areas. The analysis of sediment composition also provides insights into past environmental conditions and biological communities, especially in extreme environments like the deep sea.
Sediment coring: Sediment coring is a technique used to collect cylindrical samples of sediment from the seafloor, allowing scientists to analyze layers of sediment that have accumulated over time. This method provides critical insights into past environmental conditions, biological activity, and geological processes, particularly in deep-sea settings where traditional sampling methods may be challenging.
Submersible Surveys: Submersible surveys are scientific explorations conducted using submersible vehicles that operate underwater to collect data on marine environments, particularly in deep-sea ecosystems. These surveys allow researchers to gather valuable information about biodiversity, geological features, and the dynamics of ecosystems like chemosynthetic communities, which thrive in extreme conditions where sunlight does not penetrate.
Sulfur cycling: Sulfur cycling refers to the natural process through which sulfur moves through various environmental systems, including the atmosphere, lithosphere, hydrosphere, and biosphere. This process plays a critical role in the functioning of ecosystems, particularly in deep-sea environments, where sulfur compounds serve as energy sources for chemosynthetic communities that thrive in extreme conditions.
Symbiosis: Symbiosis refers to the interaction between two different organisms living in close physical proximity, which can be beneficial, neutral, or harmful to one or both parties involved. This relationship can take various forms, including mutualism, commensalism, and parasitism, and plays a critical role in ecological dynamics and evolution, especially in complex marine ecosystems.
Thermophily: Thermophily refers to the preference of certain organisms, known as thermophiles, for high-temperature environments, typically above 45°C (113°F). These organisms thrive in extreme conditions such as hot springs, hydrothermal vents, and other geothermal habitats, and they have specialized adaptations that allow them to survive and reproduce in such harsh environments.
Trophic levels: Trophic levels refer to the hierarchical positions that organisms occupy in a food web, based on their feeding relationships and energy flow within an ecosystem. These levels typically include producers, primary consumers, secondary consumers, and tertiary consumers, each representing different roles in energy transfer and ecological dynamics.
Tubeworms: Tubeworms are marine invertebrates that belong to the class Polychaeta and are known for their tube-shaped structures made of chitin or calcium carbonate. These organisms play a crucial role in deep-sea ecosystems, particularly in chemosynthetic communities, where they thrive near hydrothermal vents and cold seeps, relying on symbiotic bacteria to convert toxic chemicals into energy.