Threats to the Deep sea

The following outlines some of the most important present threats to deep sea ecosystems  and threats that may follow in the future.

Oil, gas and mineral exploration

At present oil, minerals and gas are only being extracted from reserves on the continental shelves but larger resources have been found beneath the deep ocean floor. Currently we are not extracting these resources, as it is not currently possible, but there is future planning for extraction in these areas (Richard et al. 2007). If this were to happen, the disruption caused could have a huge impact on delicate slow growing communities, like those found around hydrothermal vents. Vent sites contain large sources of minerals, including sulphide, and exploration here is already on going which means extraction of these areas could start within the next decade. It is important that regulations are formulated now so that these delicate ecosystems can be protected.

Destructive fishing practices

Figure 12. Aftermath of a Deep-sea trawler on the Lophelia Reef in Norway (A Plan to Torpedo the Trawlers)

Bottom trawling is the fishing practice which has the biggest impact on the deep sea ecosystem. It destroys cold water corals (Figure 12) and in 2006 the UN report stated that bottom trawling had caused 95% of the damage to sea mounts (United Nations 2006). It is thought that the damage caused to cold water coral reef systems will take several hundred years to recover – if they ever recover at all (Roberts et al. 2006). The effect of this type of fishing gear is well known and yet its use still continues.


Many species in the deep sea, due to their slow metabolisms, are slow growing, long lived and some take many years to reach sexual maturity. This means the effects of overfishing on these species will have far more of an impact on their populations more quickly than that of other surface water species, and would take numerous years for populations to recover fully, if recovery is even possible. Currently around 40% of the worlds fisheries are in waters deeper than the continental shelves (Roberts 2002). Due to most deep sea fisheries being located in international waters, it is often very hard to set and enforce restrictions and regulations. This leaves these areas quite exposed to exploitation by deep sea fishermen, and some people think most deep sea fish species are currently being over exploited. An example is the orange roughy, Hoplostethus atlanticus. Fishing of this species started in the 1970s with landings of around 60t being recorded, however, now the population is at less than 20% of what it was before (Roberts 2002).


Whilst the disposal of low-level radioactive waste at subductive plate boundaries and other suitable geological formations is relatively safe, as they are generally areas containing little life, the dumping of this type of waste onto the sea floor, despite radically reducing the exposure levels to humans, may cause exposure to marine life (Haegan 1988) despite the claim that the sealed containers are leak-proof. The current guidelines outline what radioactive waste is inappropriate for disposing in the sea with only regard to human safety – not marine life (Haegan 1988). It is believed direct exposure can lead to increased mortality and lowered reproductive success (Haegan 1988) but these effects will decrease with distance from the source. This shows that new guidelines need to be made in order to take into the effect that it has on marine life.

Climate change

This is probably the biggest problem faced by all organisms in the ocean. The deep sea organisms are reliant on the marine snow that falls from the productive upper waters as it is their only primary food source. As the upper waters warm, the water becomes more stratified, preventing the mixing of the essential nutrients or photosynthesis (Robison 2009). This would cause phytoplankton biomass to decrease and could lead to a transfer of primary production from the lower to higher latitudes (Robison 2009). This would have huge consequences on the distribution of bathypelagic organisms and diversity, as well as their feeding and reproductive cycles. The organisms that have adapted to survive here are used to constant temperatures and may be very susceptible to the smallest of changes (Robison 2009). The low oxygen content at depth could be further reduced and at such a rate that organisms are not able to adapt. Steps need to be taken now before we lose species we still don’t even know exist.


In summary, the deep sea is a very delicate ecosystem which could be damaged by the slightest of changes. We must start collecting more knowledge about this environment so that we can better know how to protect it. Steps must be taken now in order to secure the future of the deep sea, and indeed the whole ocean, before irreversible damage is done.

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