C+S 2020 students are blogging about topics that interest them for Applications in Climate and Society, a core spring class.
Roughly 4,000 meters below the sea lies a world of alien lifeforms right here on Earth.
The deep sea is populated with whimsical and highly specialized creatures only recently becoming known to us. While seemingly untouchable at their depths, climate change impacts are increasingly encroaching on these cryptic ocean communities.
Deep sea ecosystems are part of a vast oceanic-planetary regulatory system. Through deep ocean mixing (mixing of waters of different temperatures and densities), the deep sea helps drive ocean currents. The deep sea also absorbs heat and atmospheric CO2. In this way, the deep sea acts as a buffer from the effects of climate change. However, the ocean can only hold so much heat and only so much CO2. Once its capacity to absorb is overshot, the deep sea can no longer provide these services. If these systems are harmed, they could exacerbate climate change by further contributing to methane gas concentrations and inhibiting its ability to serve as a carbon and heat sink.
Specific threats include ocean acidification, deep sea warming, and a decreased availability of food, all caused by anthropogenic climate change. The health of the deep sea is closely connected with the health of surface water ecosystems.
Life in the oceans and in the deep sea particularly are necessary for capturing and storing carbon, and as these species die off, these ecosystems are less able to serve that function.
To better understand the links between the atmosphere and the deep sea, let’s look at the methane vent communities. Ocean floor methane vents, seemingly inhospitable places, are actually home to unique species of bacteria and worms, that are specially adapted to feed on this greenhouse gas, preventing it from reaching the surface. More specifically, the bacteria feed on the methane and live on the worm and then the worm eats the bacteria. This form of methane oxidation is responsible for the capture of roughly 382 teragrams of methane per year, preventing it from reaching the atmosphere.
Ocean warming could cause “a climate-induced shift in warm currents such as the Gulf Stream...” which “...may be sufficient to release many gigatons of frozen methane from the seafloor, surpassing the buffering capacity of the seep microbial and animal biota that routinely oxidize methane.”
Warming of deep ocean waters caused by climate change also impacts “the transport of heat, oxygen, CO2, and particulate organic carbon from the ocean surface through ocean circulation and mixing.”
From what scientists understand thus far, the deep sea is a valuable carbon and heat sink. The health and functioning of this ecosystem are dependent on the health of surface water ecosystems, which could be greatly impacted by climate change.
Despite the importance of the deep sea, there is a lack of policy and scientific information about this ecosystem that makes up 90% of Earth’s livable area. Scientific understanding of the deep sea is still an emerging field and more research needs to be done.
Steps towards the protection of this ecosystem include conservation, creation of marine protected areas, increased research, management, policy, and decreased atmospheric carbon emissions. These measures are necessary to maintain the health of the deep sea and preserve its ability to store carbon and heat, manage methane, and regulate global climate.
As foreign as they may seem to us on land, deep sea ecosystems and their array of flora and fauna are necessary to life on Earth; we need them, and as climate change approaches, they need us.
