Bridget Hott

The deep sea ecosystem, while still wildly unknown, faces many pressing anthropogenic threats. Among some of the most endangered ecosystems on the planet are deep water corals and seamounts, due to increasing fishing pressures, mineral extraction and climate change. The more we find out about the habitats of the deep sea, the clearer it becomes that their presence is vital to life on Earth.

“We need to know what species do and why they are important so we don’t run the risk of losing them before we know we need them, whether that be for providing food, climate regulation, nutrient cycling, or other supporting services.” - Lisa Levin, Scripps Institution of Oceanography

Climate Change and the Deep Sea

Perhaps quite surprisingly, what happens on the surface of the ocean has a large impact on the seafloor thousands of meters below. Organic material falls from the upper levels of the ocean all the way to the bottom of the sea, bringing nutrients to life forms that have minimal access to them. The primary production that allows epipelagic species to supply one another with nutrients can alter the stability and demographics of the abyssal populations below. Evidence from a study at an abyssal plain in the NE Atlantic showed that a species that was once almost non-existent climbed its way to the top of the ecosystem because of its ability to quickly adapt and utilize the nutrients being provided by a seasonal detritus bloom. This study has very important indications when considering the already noticeable effects climate change is having on primary productivity in the open oceans. It suggests that the stable environments of the deep, that are responsible for regulating nutrient levels and consistent weather patterns, could see significant changes before scientists and researchers have the chance to fully understand their role in oceanic and global ecosystems. 

Deep Sea Fisheries

The fishing industry has pushed surface level fish stocks close to total depletion. With 90% of the world’s fisheries listed as fully exploited, depleted, or over exploited, as much as 40% of fisheries have moved into deeper waters looking for fish to catch. Of course, this movement brings heavy nets and trawlers to deep sea habitats, flattening reefs, disturbing fragile abyssal plains and completely ransacking seamount populations. 

As a direct result from deep sea fishing, corals and seamounts are among the most damaged ecosystems. Both of these environments have exceptional biodiversity and encourage high levels of nutrient cycling, making them ideal support systems for large, predatory fish, and therefore, targets of commercial fisheries. By dragging heavy trawling nets over fragile habitats, the fishing industry has played a direct role in the destruction of the habitats that supply the economic support required for maintaining their operations. Long term studies conducted over the last decade on cold water corals showed that after a 7 year period, no new growth was observed in areas damaged by bottom trawling. Additionally, a 2012 study proved bottom trawling permanently disrupted the chemical and geological composition of soft sediment habitats, completely changing the biological function of these areas for good. 

Deep Sea Drilling and Mining

The deep sea is also well known for its high quantities of gas and oil reserves, subjecting it to destructive drills, alarming amounts of noise, and oftentimes, disastrous spills and leaks. The toxins released from drilling and oil spills have long-term effects on marine organisms and have been repeatedly linked to decreasing reproductive success. Marine organisms living in the deep sea have notoriously slow growth rates, often reaching sexual maturity quite late in their life span. Species now face the potential of toxins damaging their reproductive ability on top of increasing fishing pressures that diminish population sizes before sexual maturity is met, reducing their chances of successfully passing their genes to the next generation. 

The deep sea is still unknown and far from being understood, with potential for scientific advancements around every turn. Unfortunately, this also means the full extent of the threats they face are also underestimated, as we can only assume the damage of what we currently know. Moving forward with the exploration and exploitation of the deep sea will require extensive research and careful treading as to not permanently alter the processes that regulate life on Earth. Fortunately, most deep sea habitats lie in international waters, placing them under the jurisdiction of the United Nations. They have instituted policies under the United Nations Convention on the Law of the Sea and founded institutions such as the International Seabed Authority, an organization responsible for ensuring exploitation of the deep sea is used for the betterment of all mankind and within sustainable limits. With the proper policies and enforcements in place, there is still great hope for preserving the invaluable deep sea ecosystem. 

Rising Tides is a series focussing on the current threats facing our ocean, how these are being tackled and what you can do to help

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