Habitat Report - Hyrdothermal Vents PDF

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A habitat report of hydrothermal vents....

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Tall, Dark, Deep and Hot A Hydrothermal Vent Habitat Report by Christien Greaves

Photo source: http://marinbiologene.no/blogg/

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Contents Introduction"

3

Formulation and Development"

3

Ecology"

4

Threats"

7

Natural"

7

Anthropogenic"

8

Conservation and Management"

9

Conclusion"

11

Bibliography"

11

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Introduction This report will give a broad overview of the ecological factors affecting the hydrothermal vent habitat. An analysis will be made of these endemic environments, including their physical formation and the threats they are under. It will also aim to provide an understanding of the interactions and relationships between the inhabiting flora and fauna, to aid the formulation of appropriate conservational management.

Figure 1. Tube worms and anemones on the Galapagos Rift. Photo Credit: NOAA

Formulation and Development Deep sea hydrothermal vents (also known as black smokers) are large towers of volcanic rock that disgorge chemical rich fluids from the Earths core into the deep ocean, forming in a similar fashion to stalactites, by the steady deposit of minerals as they escape from the vent. They are found along the Mid-Ocean Ridge, the Earth’s largest feature, which wraps around the Earth for 65,000 kilometres (40,390 miles) (NOAA, 2014). It is located along divergent plate boundaries, where new ocean floor is created as a result of the Earth’s tectonic plates spreading. Molten rock rises to the sea floor as these plates move apart causing underwater volcanoes to erupt, spewing basalt into the deep ocean. The build up of this volcanic rock creates the gargantuan Mid-Ocean Ridge. Charles Wyville Thomson in 1872 discovered the Mid-Atlantic Ridge which helped provide evidence for Wegner’s theory of continental drift and the breakup of the hypothetical supercontinent Pangea some 180 million years ago, as the rise mimics both land masses on each side. The first vent (otherwise known as a black smoker) was discovered on the East

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Pacific Rise (Venture Deep Ocean, 2006) in 1977 by Dr. Robert Ballard from the Scripps Institution of Oceanography, and his team were the first humans to ever witness hydrothermal vent life. Ballard believes it was “probably one of the biggest biological discoveries ever made on Earth.” (Venture Deep Ocean, 2006) In 2008, through the use of seismometers, the scientific communities previous understanding of how black smokers form and develop was challenged. These seismometers were planted around the East Pacific Rise, around 565 miles southwest of Acapulco, Mexico and recorded 7000 tiny, shallow earthquakes over a 7 month period from 2003 to 2004. These quakes neatly cluster around where cold water seeps through tiny fissures (made by a kink in the mid ocean ridge), this cold water plunges straight down through this downflow chimney for around 700 metres straight down through the ridge, then ‘fans out into a horizontal band about 200 metres wide before bottoming out at about 1.5 kilometres, just above the magma.’ (Lamont-Doherty Earth Observatory, 2008). The quakes are a result of the cold water shocking hot rocks and cracking them. This energy is then absorbed by the water alongside the heat from the magma, superheating the water which then rises back up through a dozen vents about 2 kilometers north along the ridge (Tolstoy et al, 2008). Interestingly, biologists at Lamont-Doherty Earth Observatory (2008) used submersibles to discover that ‘the area around the downflow chimney is more or less lifeless’, which highlights the important role heat and chemosynthesis play in the hydrothermal vent ecosystem. A new hydrothermal vent field along the Mid-Cayman Rise at the depth of 4,960m, was discovered in 2012 along with the deepest black smoker, the Beebe Vent (named after William Beebe an American naturalist and ornithologist). This vent is 20% deeper than any other previously discovered vent, and like all vents emits mineral and chemical rich fluids, although has a buoyant plume that rises 1,100m, as opposed to the typical 200-400m, consistent with >400 °C (Connelly et al., 2012). This has significant implications for how far the minerals and other vent-derived chemicals may be traveling away from the vent field. Scientists know that ocean chemistry has a massive effect on our global ecosystem and ‘the other Co2 problem’ ocean acidification (Doney et al, 2009), and that hydrothermal vents have a big part to play, yet to what extent is fairly unknown. (Ingleton, 2014)

Ecology The discovery of hydrothermal ecosystems has actually redefined our understanding of the origins of life and its development, and a new food web was developed to reflect the role that chemosynthesis plays. Food webs are a useful tool to display an overview of the predation and prey movements in an ecosystem, but never truly portray the intricacies, complexities and sheer vast amounts of species interactions; as highlighted in Figure 2.

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Figure 2. An example of a hydrothermal vent food web with many species not included. Photo source: NOAA (no date)

In 1880, a Russian scientist called Sergei Winogradsky discovered Beggiatoa, one of the first ever bacteria (believed now to be the biggest biomass on the planet). Beggiatoa is an example of a sulfide-oxidising chemoautotrophic bacteria, the primary producers in this ecosystem. Over billions of years it developed the ability to metabolise hydrogen sulphide (taken straight from the chemical rich fluids that escape out of black smokers) to produce the energy for making carbohydrates, a process known as chemosynthesis (Dailey, 1994). If photosynthesis is the solar power of the natural world, chemosynthesis is the battery power (Olins, 2015). The discovery of this process implies that the ‘abiotic synthesis of chemical compounds, origin and evolution of ‘precells’ and ‘precell’ communities and, ultimately, the evolution of free-living organisms’ started at hydrothermal vents, the only contemporary geological environment that could be considered as primeval, as it’s analogous to the Archean ocean (Baross and Hoffman, 1985). Further evidence from Nye (2008) supports the hypothesis that this is where life began, because some of the most ancient organisms known seem to be heat loving hyperthermophiles (organisms that prefer temperatures above 80°C) (Olins, 2015). This microbial discovery has huge implications for extraterrestrial life, and astrobiologists are interested in hydrothermal vents as it is possible that volcanic activity on distant worlds such as Io, Europa (two of Jupiter’s moons) or Titan (Saturn’s largest moon) may form hydrothermal vents which would be potential energy sources for chemosynthetic life (Bell, 2011).

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Beggiatoa (a vent bacteria; see figure 2 and 3) grows in large white or orange mats, and provide nutrients to many consumers such as crabs, snails, shrimp (NOAA, 2014) and nematodes (Spies and DesMarais, 1983), ‘the most numerous multicellular animals on earth’ (University of Nebraska-Lincoln, no date). Nematodes are still a fairly unexplored species in regards to research, but it is known that they play a key role in trophic levels and are considered an indicator species for many ecosystems around the world (Vanreusel et al., 2010). To keep themselves near food sources, nematodes use the ecosystems flagship primary consumer the Giant Tube Worm (riftia pachyptila) (see figure 1) as an anchor; who can grow to lengths of 9ft, and have an interesting and unique symbiotic relationship with another chemosynthetic bacteria.

Figure 3. Beggiatoa under different microscopic lenses. Photo source: Ian McDonald and Mandy Joye (2010)

The relationship between the Giant Tube Worms and a similar hyperthermophile bacteria differs to other endosymbiotic relationships within the ecosystem. Usually bacteria is found close to the external environment, on the gills of molluscs for example or the chelipeds of the Yeti Lobster, except for the Tube Worm (Fisher, Childress, and Minnich, 1989). The worms release their eggs into the water to be fertilised, once hatched, the larvae swim down and attach themselves to the rock (Fothergill and Attenborough, 2015). They consume the endosymbiotic, sulfide-oxidising, chemoautotrophic bacteria and then bring it to their gut. As

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the larvae develop, their mouths and guts disappear, trapping the bacteria inside them. The bacteria is stored internally in an organ called the trophosome, located in the trunk of the worm. Haddad et al. (1995) proposed ‘that this bacterial population participates in either the nutrition of the worm or in detoxification of the worm's immediate environment’. The tube worms bright red plume is a specialised organ that is used for exchanging compounds such as oxygen, carbon dioxide, and hydrogen sulphide with the seawater, allowing the bacteria to more efficiently convert the chemicals from the vents into organic molecules that provide food for the worm (Fisher, Childress, and Minnich, 1989). These tube worms also provide shelter for shrimp and crustaceans, as well as a small food source (NOAA, 2014). One of these primary consumer crustaceans, that find sanctuary amongst the Giant Tube Worms, harbours another interesting symbiotic relationship. The Yeti Lobster has chelipeds covered in dense setae and a species of epibiotic bacteria (Ott, 2006). The Yeti Lobster and this bacteria are in another mutualistic symbiotic relationship as the host crustacean literally dances in the warm hydrothermal fluids in order to facilitate the growth of its epibionts by providing an attachment substrate, and through its continual cheliped movement, the lobster facilitates increased epibiont productivity as well (Thurber et al., 2011). The Yeti Lobster then consumes the carbohydrates produced by the bacteria for its main food source, but it is believed that they also nibble on the fleshy red plume of the Giant Tube Worm (NOAA, 2014). Each hydrothermal vent ecosystem has vast distances between them and are completely isolated from any other ecosystems (other than the endless deep-water open ocean), each hydrothermal ecosystem uniquely develops depending on ocean currents, position on the planet and which specific part of the Mid-Ocean Ridge the vent is located. Dando and Juniper (2001) elucidate ‘some vent fields and regions are already known to have a high degree of endemism… possibly as a result of geographic isolation or unique habitat conditions.’

Threats Natural Although this ecosystem and its inhabitants have developed in one of the most extreme places on earth, they are still considered extremely fragile (Dando and Juniper, 2001). Since their discovery vents have been known as ‘ephemeral habitat islands’ (Van Dover, 2014). The entire ecosystem is based upon the hot, chemical rich fluid that is constantly pumped from the Earth’s core, and with just little shifts in seismic activity, an eddy is created in the underlying molten rock and the fluid gets cut off from the existing vent. All of the unique and exciting creatures that depend on these fluids wither and die. ‘Scientists have returned to once thriving vent sites only to find them completely cold and dead’ (Knight, 2015).

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Figure 4. Natural and Anthropogenic Threats to Hydrothermal Vent Ecosystems. Photo source: Cindy Lee Van Dover (2014)

Alternatively, volcanic activity could shift and the area becomes too hot, cooking and burying its inhabitants. Anecdotal evidence suggest that once a vent stops, conventional deep sea creatures start to use the site (Education Department of the American Museum of Natural History, 2002). The organisms that dwell in this ecosystem have learnt to deal with tidal variations to earthquakes and volcanic eruptions yet mining is seen to be the biggest threat to hydrothermal vent ecosystems (see figure 4).

Anthropogenic Extremophiles, are organisms that are adapted to the extreme thermal and chemical conditions, and they are of interest to those who are application-minded because they might

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make compounds that could benefit humanity, for example by being useful medically as drugs or by having chemical properties that make them valuable in some industrial settings. According to Leary (2004), enzymes developed from vent bacteria thus far include: Pyrolase™ 60, Valley Ultra-Thin™ by Diversa Corporation, ThermalAce™ DNA Polymerase by Invitrogen Corporation, and Deep VentR® DNA Polymerase amongst others by New England Biolabs Inc. Scientific investigation has a high ‘knowledge value’ measured by both the number of publications resulting from this research and their impact factors (Godet et#al., 2011). The greatest impact scientific investigation has on the ecosystem is through the use of HOV’s (Human-Operated Vehicles) and ROV’s (Remotely Operated Vehicles), as they are large and heavy (could accidentally crush seabed species) and emits intrusive light. Shrimp with damaged thoracic eyes have been recorded in areas of HOV/ROV investigation (Van Dover, 2014), but Copley et al (2007) suggests that this has no immediate conservational risk. However, this light could also cause changes in their behaviour, which in turn would effect the results of any Figure 5. Concept instillation schematic investigation (Stoner et#al., 2008). design of a vent submarine generator. Photo source: Hiriart et al (2010)

Hydrothermal and geothermal energy sources have been considered since vents were first discovered and are still under study. Parada et al (2012) envisioned the extraction of vent minerals and hydrogen fuel production (Bubis at al., 1993) using thermo-electric generators that power offshore gigawatt power stations. See figure 5.

Conservation and Management Unfortunately for the ecosystem, the commercial exploitation of hydrothermal vents is increasing (Hannington et al., 2011). However, Patrick Collins et al. (2013) explains that ‘management and conservation efforts precede industrial exploitation and can provide an anticipatory, rather than reactionary, assessment of the environmental impacts of deep-sea mining’. The United Nations Convention on the Law of the Sea (UNCLOS) is an international legal framework that manages the exploitation of these benthic habitats (Parada et al., 2012) and ‘defines the rights and responsibilities of nations with respect to their use of the world's oceans, establishing guidelines for businesses, the environment, and the management of marine natural resources’ (National Oceanography Centre, no date).

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In 2013, VentBase (a workshop held at the National University of Ireland, Galway) made sure they abided by the six guidelines Interidge (2011) created in its attempt to confront the impacts of scientific research, whilst developing an appropriate three stage management plan. Stage one will involve regional mapping to better define the physical elements of the site. Stage two involves video surveying the site to define the chemical and biological elements, and stage three involves ‘targeted biological sampling’ (VentBase, 2013). During this workshop, standardised sampling methodologies were created: ‘sample triage, video survey, hard sampling benthic fauna, plankton sampling, taxonomic protocols, sample quality assurance/ control and sampling for molecular studies.’ The International Seabed Authority (ISA) were requested to include these methodologies in their forth-coming development and exploration policies (VentBase, 2013), which revolve specifically around polymetallic nodules but it is currently developing a regulated system for exploring polymetallic sulphides, cobalt-rich crusts and other new resources. The International Marine Minerals Society (IMMS) is helping by creating a ‘code of conduct’ to assess potential marine mining sites (Dando and Juniper, 2001) as it is clear that an Environmental Impact Assessment (EIA) is necessary before any commercial activities occur (Van Dover, 2014; Dando and Juniper, 2001). This EIA is a requirement by the ISA and must conform to the standard criteria used by other marine EIA’s which are as following: Defining the type of disturbance, approximation of the amount of vent habitat lost, identifying the organism that will be affected and ‘dose-response characteristics of plume fallout’ (Dando and Juniper, 2001). It is easy to a adopt a narrow attitude and fight against the ever moving machine of commercialism, and from first glance this would seem like the appropriate mind-set. However a broader picture must be taken into account. Humans are currently facing massive energy resource problems, and our current methods (fossil fuels, oil, etc.) are rapidly running out. Until we can develop renewable, green energy (solar power, wind power, etc.) to be so effective that it can keep up with with our current rates of consumption, an alternative source must be used (UK Department of Energy and Climate Change, 2013). In an ideal world, the Human race would regulate and distribute consumption to a manageable level and live within our means, but this would be a naive and dangerous attitude. Instead we must endeavour to obtain other energy resources to cover the gap between now and total renewable energy. Hiriart et al. (2009) calculated that if 1% of the Earths vents were utilised practically, a huge 160,000 MW of electricity could be generated! In perspective, this could power 14,635.9321 American homes for an entire year at the current energy consumption rates (U.S. Energy Information Administration, 2015). At critical times like this, we must ask ourselves: Is the possible salvation of the planet worth the possible disturbance of a percentage of hydrothermal ecosystems?

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Conclusion The utmost care must be taken to ensure the continuous survival of the hydrothermal ecosystem, for the benefit of the local fauna and flora, but for the beneficial global implications as well. Ecologically significant species are found at these sites and are mostly endemic, exhibit unusual symbioses and physiological adaptations, and could be classed as evolutionary relics. These reasons alone are enough to demand adequate protection, yet there are a myriad of other reason. The origins of life on Earth, the implications of extraterrestrial life, the contributions to the scientific community, the possibility of a relatively non-intrusive alternative energy, the list continues. However, due to the unstable nature of the ecosystem, huge efforts to try and maintain the ecosystem at a level of ‘naturalness’ could prove to be a pointless endeavour, as the magma flow could shift, wiping out the ecosystem and any efforts made. What we can do is ensure that we, as a species, are not furthering the likelihood of collapse by monitoring and managing our own impacts. Conservation should be reduced to minimising anthropogenic involvement, and as it seems that exploitation is unavoidable, then the creation of a sustainable plan is imperative.

Bibliography Baross, J. A. and Hoffman, S. E. (1985) ‘Submarine hydrothermal vents and associated gradient environments as sites for the origin and evolution of life’, Origins of Life and Evolution of the Biosphere, 15(4), pp. 327–345. doi: 10.1007/bf01808177. Barriga, F. J., Relvas, J. M., Santos, R. and Pascoal, A. (2013) Estimating and finding seafloor and sub-seafloor sulfide mineralization: Optimists versus pessimists?. Available at: http:// www.underwatermining.org/UMI2013/downloads/UMI2013_Abstract_Barriga_et_al.pdf (Accessed: 7 December 2015). Bell, E. M. (2011) Life at extremes: Environments, organisms, and strategies for survival. Edited by E. M. Bell....