Ecology of Aquatic Environments Hydrothermal Vents Source Chamberlin

Ecology of Aquatic Environments: Hydrothermal Vents Source: Chamberlin & Dickey (2008). Figure 14 -15

Intended Learning Outcomes: Successful completion of this component will enable you to: 1. Describe the co-varying effects of physical, chemical and biological factors on the adaptations of deepsea organisms. co-vary - vary in the same time period (two random variables) 2. Evaluate the influence of variables co-varying with depth on communities, populations, and species. 3. Discuss the various sources of energy available to deep-sea organisms and their controls on community processes.

Factors Driving Deep Sea Systems • High pressure (1 atmosphere /10 m) • Low temperature (4◦C) • Depth • Lack of sunlight • Lack of photosynthesis • Scarcity of food resources • Expanse of the deep sea • Enormous volume of water further reduces encounter probability (mates, prey)

The deep sea is cold and dark • Food webs are only weakly supported by organic matter raining from above • Photosynthetic production of new organic matter is not possible due to lack of light • Most deep sea communities are adapted to: – Sparse food availability, and, – Low population density

Deep-sea benthic ecosystems cover 75% of the surface area of the planet • Yet they remain relatively unknown • Deep-sea benthic habitats are diverse: • Soft-bottom: ooze-rich abyssal plains & abyssal hills • Hard-bottom: seamounts, oceanic ridges, oceanic trenches, submarine canyons • Vent habitats: hydrothermal vents and cold seeps

Without photosynthesis to fuel production energy must come from elsewhere • What alternative energy sources exist - Deep Sea? – Phytodetritus: Fallen products of algal blooms – Food falls: Carcasses of animals falling to the sea bed – Chemosynthesis: Methane and sulfur-rich fluids provide energy for chemosynthetic bacteria in some deep sea communities Photosynthesis and chemosynthesis are both processes by which organisms produce food; photosynthesis is powered by sunlight while chemosynthesis runs on chemical energy.

Chemosynthesis requires high concentrations of chemicals such as hydrogen sulfide or methane. • Cold Seeps – Occur at tectonic active places in the seafloor where hydrogen sulfide, oil, highly saline water and methane leak out to form brine pools – Brine pools – underwater lakes – Salt conc more dense than ocean – Can be high or low sulphide conc

Hydrothermal Vents • … are the result of seawater percolating down through fissures in the ocean crust in the vicinity of spreading centers or subduction zones. • The cold seawater is heated by hot magma and reemerges to form the vents.

Hydrothermal vents • Places where hot, mineral and gas-rich fluids are ejected into the ocean • Seawater emitted may reach temperatures of over 340°C (700°F). • The hot seawater in does not boil because of the extreme pressure at these depths. Fig 17. 16 a, Segar (2007)

Hydrothermal vent chimneys • Discharged vent water contains high concentrations of iron, manganese and other sulfides • As these sulfides oxidise in seawater they are deposited as a chimney around the vent mouth Fig 17. 16 b, Segar (2007)

Smokers • “Black smokers” are chimneys formed from deposits of iron sulfide, which is black. • “White smokers” are chimneys formed from deposits of barium, calcium, and silicon, which are white. The longevity of vents (years to decades) makes these thriving, diverse ecosystems

Chemosynthesises organic material from inorganic substances • Chemosynthesis can sustain vibrant food webs in the complete absence of sunlight Unique communities: Microorganisms - basis of the food chain undertake chemosynthesis http: //www. teara. govt. nz/ files/di 8960 enz. jpg An example of a chemosynthetic reaction: 6 CO 2 + 6 H 2 O + 3 H 2 S C 6 H 12 O 6 + 3 H 2 SO 4 Carbon dioxide + Water + Hydrogen sulphide Sugar + Sulphur compounds

Deep sea hydrothermal vent communities Succession at vent fields: Ø Microorganisms move in (microbial mats and fill seawater) Ø Mobile vent fauna (amphipods, copepods, crabs) Ø Vestimiferan tube worms follow replacing parts of the mats Ø Later arrivals scavengers: include crabs, mussels and polychaetes. Ø Predators: vent crabs, octopi Community takes 3 yrs to reach maturity http: //tinyurl. com/BBC-Deep-Sea-Vent unexpectedly high organism densities & growth rates observed

Symbiosis in Hydrothermal Vents • Chemosynthetic bacteria – Basis of food chain • Symbiotic with primary producers (bacteria): – Tube worms, giant clams (e. g. Riftia pachyptila, Tevnia jerichonana)

Communities found at deep-sea hydrothermal vents are characterised by symbioses Polychaetes with ectosymbionts Shrimps with ectosymbionts on mouthparts & gills Gastropods with bacteria in gills From: Dubilier, N. , et al. (2008). Symbiotic diversity in marine animals: the art of harnessing chemosynthesis. Nature Reviews Microbiology 6: 725 -740

In chemosynthetic food webs symbionts are treated as primary consumers

Source: Chamberlin & Dickey (2008). Figure 14 -15

Factors driving Hydrothermal Vent Systems • High pressure • Low temperature • Depth • Lack of sunlight • Lack of photosynthesis • Scarcity of food resources • Enormous volume of water further reduces encounter probability • Counteracted by: • Chemosynthetic bacteria (primary producers) • Hot, mineral-rich water • Location – advantages and disadvantages

Self study assessment § Moodle site: EAE 2018 § Practical exercises: Hydrothermal vent chemosynthetic food web - http: //www. montereyinstitute. org/noaa/lesson 05/l 5 la 1. htm