User:MimiDeepSea/sandbox

= Human impact on the deep sea = The deep sea can be considered one of the last great wildernesses on Earth: it covers approximately 60% of the planet's surface, with only about 0.0001% biologically surveyed. With an average depth of 4 km, pressures reaching hundreds of bars, lack of sunlight, and temperatures near 0ºC, the deep sea is extremely inaccessible to humans.

Despite the remoteness of the deep sea, it provides crucial ecological services on a global scale and is sensitive to direct and indirect human pressures. Climate change and associated influences on CO2 cycling and ocean circulation will likely affect deep sea ecosystems. Millions of tons of waste has reached the deep sea floor, placing potential hazards to endemic organisms. Increasing demands for economically important mineral and oil resources, combined with exhausted reserves on land, have driven industries to mine and drill into the deep sea. The depletion of commercial fishing stocks in has extended fisheries into deeper waters, where slow-growing species are especially vulnerable to overfishing. These challenges facing the deep sea environment are widespread and predicted to intensify over time. Collaboration across scientific, industrial, and political organizations will be necessary to sustainably manage and conserve these ecosystems.

Carbon cycling
Deep water masses serve as major storage sites for carbon, as the buffering capacity allows for dissolved atmospheric carbon dioxide (CO2) to be sequestered. The deep sea has absorbed 25% of anthropogenic carbon emissions and 93% of the associated heat. Sequestration of carbon in the deep sea also buffers the ocean against pH change, slowing the detrimental effects of ocean acidification. The low temperatures and high densities of deep water masses prevents thermohaline circulation and maintains this storage for approximately 1,000 years before reaching the atmosphere again.

The microbial oxidation of methane occurs surrounding large deep sea reservoirs of methane and serves to rapidly consume the majority of gas released. This process leads to the precipitation of carbonate rocks, which sequesters the carbon from methane in a solid form. Mediation of methane release to the atmosphere is crucial, as methane is a potent greenhouse gas. In the geologic past, disruption to methane release is thought to have caused mass extinction events.


 * methane hydrates

Nutrient cycling
A portion of organic matter from overlying water sinks to reach the deep seafloor and is broken down, or remineralised, into simpler forms to be recycled as nutrients. Remineralisation is facilitated by microbes in deep-sea sediments and drives the cycling of carbon, nitrogen, silica, phosphorus, hydrogen, and sulfur. This process is key for the functioning of Earth's biological pump as the regenerated nutrients are eventually circulated to the surface to supply phytoplankton to undergo primary production through photosynthesis.

Biochemical potential
The deep sea is punctuated by environmental variations, such as oxygen minimum zones (OMZs), hydrothermal vents, and cold seeps, which support key biogeochemical reactions and hot-spots of microbial communities. Unique ecosystems of the deep sea host wide diversity of species, enzymes, and genetic resources with potential for biotechnology, medicine and pharmaceutical applications, as well as adaptive resilience to environmental changes.

Climate change and the deep sea
Modern industrial processes, including fossil fuel burning and deforestation, have increased CO2,emission to the atmosphere. Continued CO2 input causes Earth's average temperature to increase, which poses dire implications on the functional, physical and chemical characteristics of the deep-sea. Changes to the deep-sea have already been correlated with climate variation over the past 20 years, including increased water temperature, deoxygenation, lowered pH, and altered carbon cycling.

Temperature increase
The ocean serves as a major sink for heat produced by the greenhouse effect, helping to mitigate the increase in global temperature. Warming to the upper-ocean has been documented, and 19% of this heat is channeled to the deep sea. Studies suggest warming is occurring in abyssal (>3000 m) ecosystems at 0.01 to 0.1ºC per decade. Since deep-sea organisms are often adapted to a narrow range of temperature and salinity conditions, response to temperature changes on short time scales will likely be ineffective.

Circulation change
Increasing surface water temperatures resulting from global warming are predicted to intensify stratification, or de-coupling, of shallow and deep ocean water masses. Climate models also suggest that effects of climate change and global warming could slow down the Atlantic overturning circulation, which in some regions has already demonstrated a 40% transport decrease since 1957. Stratification and slowed circulation would reduce the export of carbon to deep sea-organisms from primary producers in surface waters, and also limit the nutrient exchange provided to the phytoplankton from deep-sea processes. Climate changes in Earth's history have drastically affected deep sea-floor ecosystems, in some cases reducing crustacean communities by over 50%, taking over 4,000 years to recover.

Oxygenation decrease
Stratification predicted to occur from ocean warming would reduce the mixing of O2 between shallow and deep waters. Since O2 is also less soluble in warmer waters, the increased stratification and decreased solubility together are predicted to create widespread ocean deoxygenation. Over the last 50 years, waters in the bathyal zone (1,000 - 4,000 m) have already demonstrated considerable O2 loss and expansion of oxygen minimum zones (OMZs). Deep sea biodiversity is demonstrated to decline with decreasing O2 levels, an important deep sea ecosystem functions, like carbon and nitrogen cycling, can be highly sensitive to O2 variation. These changes in nutrient cycling would ultimately impact the flow of energy between trophic levels. Warming events during the last deglaciation led to massive expansions of OMZs to significantly alter deep sea communities and ecosystem function.

Carbon flux alteration
A portion of the organic carbon generated though primary production in overlying water sinks to the sea floor and provides the sole energy supply to most deep sea fauna. Climate change will affect phytoplankton primary production because stratification and melting sea-ice reduce nutrient availability, and increased turbidity from erosion reduces the light reaching these photosynthetic organisms. Reduced primary productivity in the surface would reduce the POC reaching the seafloor. Seafloor ecosystem patterns, abundances, and processes co-vary with the POC reaching the sediments in a matter of weeks to months. Microbial respiration and nutrient remineralisation — key global biogeochemical processes — would decreased with reduced POC. Deep sea animals are predicted to face reduced body size, metabolic rates and reproduction potential with decreasing POC.

reference to natural CO2 lake off japan

Litter
Each year, roughly 6.4 million tons of litter are dumped into the oceans, a portion of which sinks to the deep sea floor. Even the most remote parts of the ocean contain litter, one of the fastest growing threats to global oceans. Seafloor litter has been primarily comprised of consumer plastic bags and derelict fishing gear.

Organisms can mistakenly ingest litter and pass the consumed plastic to higher trophic levels. This process amplifies once plastic is degraded into small particles, or microplastics. Consumed plastic consumption may contain chemicals like PCBs and dioxins which are lethal to a variety marine organisms. Organisms can also be entangled by derelict plastic fishing gear on the seafloor.

Industrial
A variety of sources have contributed to industrial waste disposed in the deep sea. Historically, steam-powered ships dumped overboard the residues of coal burning, or clinker. More recently, clinker has been demonstrated to represent more than 50% of the hard material on the of the northeastern Atlantic seafloor, appearing toxic to some species.

Millions of tons of sewage sludge have been dumped into the deep sea until recent prohibitions. Sewage sludge increases the turbidity and reduces oxygen concentrations of surrounding waters and physical buries organisms, clogs feeding organs, and increases exposure to toxic compounds.

Radioactive waste from nuclear power plants, fuel cycle operations, and medical and research industries was disposed in the deep sea until a 1983 moratorium. From WWII through 1976, several million tons of weapons were dumped into waters around Europe, as well as munitions, chemical weapons, radioactive elements resulting from weapons testing in the USA which ultimately reached the deep sea. Radionuclide contamination has been recorded in a variety of deep sea organisms, including anemones, and crustaceans.


 * include figure of litter items on seafloor
 * include figure of litter items on seafloor
 * include figure of litter items on seafloor
 * include figure of litter items on seafloor
 * include figure of litter items on seafloor

Vulnerable Ecosystems
The notion of life existing below 300 m was debated until the 19th century, with subsequent scientific investigations establishing the deep sea is actually the largest ecosystem on Earth. Below 200 m depth, there is a distinct transition in the types of fauna present. Deep sea ecosystems are unique in that they lack sunlight, and thus cannot undergo photosynthetic primary production, a key process characterizing nearly all terrestrial and shallow marine environments. Organisms inhabiting deep water sediments primarily rely on organic material which sinks from surface waters as small particles, called marine snow.

seamounts, vents (ecology not well known, need to manage)

Sea-floor sediment ecosystems
The vast majority of the deep sea-floor is characterized by soft sediment ecosystems. Organisms inhabiting seafloor sediments, or benthos, are dominated by echinoderms (including sea urchins, sea cucumbers, and starfish). Echinoderms play important roles in organic carbon processing and bioturbation: a process of physically reworking sediments, exposing nutrients and engineering ecosystems. Populations of echinoderms are dependent on particulate organic carbon as a food source, so are likely to decline due to the lowered POC flux influenced by climate change, Large regions of sea-floor sediments are covered by manganese nodules. These hard substrates serve as habitat for a diverse fauna, including plankton, polychaetes (bristle worms), tanaids (shrimp-like crustaceans), bivalves, sea cucumbers, and brittle stars. Proposed manganese nodules mining would plow the seafloor environment and dramatically affect these ecosystems.

Deep-water corals
The deep sea hosts cold water corals, which relies on sinking food particles as an energy source, rather than the unlike tropical corals which rely on symbiotic algae. Deep-sea corals grow into extensive complexes, up to tens of kilometers in area and thousands of years old. These solid structures accumulate food resources and offer shelter for nurseries and from predators. A variety of organisms inhabit deep reefs, including plankton, fish, crustaceans, sea urchins, brittle stars, starfish, worms, sponges, jellyfish, and anemones.

Trawling and oil extraction in the deep sea destroys coral structures and discharges sediment over organisms. The declining levels of O2 associated with climate change have shown to decrease abundance of seafloor octocoral species. Ocean warming and acidification would also cause detriment to deep-sea corals and require decades to centuries for recovery since deep-sea corals lack the nutrient levels and symbionts available to shallow corals and grow more slowly.

sketch of creatures


 * figure of map of abyssal seafloor (sea screen shot, abyssal food limitation paper)

figure 4: predicted change on deep-sea benthic ecosystems (Major impacts of climate change)

Deep sea mining
Main article: Deep sea mining

Due to ever-growing demand for diverse metal resources, mining industries are increasingly interested in exploiting ore deposits from the deep ocean floor. Deep-sea mining is also viewed as an alternative to land-mining, which has large environmental impacts and imposes health risks to nearby communities. However, deep-sea mining activities are also likely to have long-lasting ecological footprints which have not been critically assessed.

Targeted resources
The deep oceans contain polymetallic nodules, cobalt-rich ferromanganese crusts, and polymetallic sulphides, which can be mined for manganese, nickel, copper, arsenic, lithium, platinum, tellurium, zinc and many rare earth elements. Under current metal prices, the area of the seafloor is estimated to be worth $20 - 30 trillion in resources. Methane hydrates are frozen at depths between 500 - 1200 m in the deep sea and estimated to store more than twice the total combustible carbon known from other fossil fuels combined.

Nodule-mining technology has been heavily funded and developed, making the production now feasible. Currently, exploration of metal deposits is underway, with exploitation likely to begin before 2027. The International Seabed Authority (ISA) has approved 26 contracts for exploration of deep-sea minerals.



Environmental effects
Researchers have argued that mining with no net loss of biodiversity is unattainable. Mining processes and machinery would directly destroy habitats and degrade water quality with the large plumes of sediment produced. In order to be profitable, a single deep-sea mining operation would require several hundred square kilometers to be mined each year. Further, areas with metallic resources are habitats for diverse ecosystems which hold beneficial biochemical potential, including design of antibiotics and cancer treatment. Deep-sea species require decades to centuries to recolonize disturbed habitats, and the metallic resources themselves take millions of years to grow. Deep-sea mining is thought represents the most significant conservation threat to the deep-sea due to its vast spatial scale and long recovery time.

define tailings discharge, shear forces, etc., describe the predicted outcome from environmental impacts

Deep sea fishing
Since overfishing has depleted many shallow-water fish stocks, demand has driven commercial fishing into deeper water. However, fishing of deep-sea species puts them at serious risk of depletion — it has been argued that there is no such thing as an economically sustainable deep-sea fishery.

Deep-sea fishing primarily targets the orange roughy, oreo, roundnose and roughhead grenadier, blue ling, black scabbardfish, redfish, Greenland halibut, sable fish, and spiny dogfish. Bottom trawling, or towing a fishing net along the sea-floor is the primary mechanism for deep-sea fishing. This practice covers an extensive area, significantly destroying the sediment ecosystems, including framework-forming corals. Deep sea fish themselves are susceptible to damage by trawls, due to their weak skin and watery tissues. Animals caught unintentionally by trawling, known as bycatch, have a 100% mortality rate. Lost and discarded nets which rest on the seafloor can passively affect fauna through ghost fishing.

Deep-water species are more vulnerable to overfishing due to their slow growth, late sexual maturity, low birth rate, and longer lifetime than shallow water species. Fish longevity increases exponentially with depth, with some deep-water species living 200 years. Seafloor communities harmed by bottom-trawling can take decades to centuries to recover. Several deep-sea species have already been fished to commercial extinction.

Oil and gas extraction in the deep sea
As oil reserves on land and shallow waters face depletion, pressure has been placed on offshore oil industries to explore production in waters below 1000 m. Large reserves have been discovered in deep waters of Mexico and West Africa.

Oil and gas extraction causes localized impacts from the accumulation of contaminated drill cuttings on seafloor habitats. The release of drilling muds, used to lubricate the drill bit and control pressure, serve as a contaminant to surrounding waters, along with dumped materials which smother ecosystem. Deep-water rigs also have the potential to leak, spill, and explode, causing widespread ecological devastation.


 * link to monterey bay aquarium seafood watch

Management and governance
Conservation of deep-sea biodiversity is crucial for oceans to sustain their functions, but major improvements are needed in data collection, availability, awareness of human impact.

Initial expeditions of the deep sea lacked sophisticated sampling methods, and erroneously characterized the region as having low biodiversity, no seasonality, and an invariant cold, tranquil environment. This misinterpretation led the United Nations Convention on the Law of the Sea to deem the deep-sea floor of the high seas exploitable for minerals and biological resources. Still today, the deep sea considered a resource of biological and mineral wealth not governed by national jurisdiction, ideal for exploitation.

By the 1980s, improved sampling and quantitative analyses demonstrated features of high diversity and heterogeneity in the deep sea environment, such as hydrothermal vents, cold seeps, benthic storms, seasonal patterns, and whale falls. The United Nations and Regional Seas conventions are developing policies to monitor, report, and regulate deep-sea activities. In 2016, the EU banned seabed trawling. The dumping of structures, radioactive waste, and munitions is now internationally prohibited. The varied human impacts described above demonstrate that there is growing need for multi-sector ocean governance in the deep sea.

put reference for benthic storm

methane hydrates: permafrost areas