As ocean surfaces acidify, a deep-sea acidic zone is expanding: Marine habitats are being squeezed

Sub: Env

Sec: Climate change

Carbon compensation depth (CCD):

In the deepest parts of the ocean, below 4,000 metres, the combination of high pressure and low temperature creates conditions that dissolve calcium carbonate, the material marine animals use to make their shells.
This zone is known as the carbonate compensation depth (CCD) – and it is expanding causing more areas where calcium carbonate dissolves.
Rising carbon dioxide levels lower ocean pH, increasing ocean acidity and raising the lysocline, where calcium carbonate becomes unstable.

Impact on Ocean Floor:

The lysocline has risen nearly 100 meters since pre-industrial times and is expected to rise several hundred meters more this century.
Millions of square kilometres of ocean floor will transition to chemically unstable, leading to sediment dissolution.

Distinct Habitats and Rising Boundaries:

The calcite saturation depth (upper limit) and calcite compensation depth (lower limit) define zones with and without calcium carbonate.
Currently, 41% of the ocean floor is below the calcite compensation depth, a figure that could increase to 51% with a 300-meter rise.
Different species dominate habitats above and below the calcite compensation depth, with more calcified organisms above and non-calcified ones below.

Additional Climate Change Effects:

Marine habitats are shrinking due to rising calcite compensation depth and warming waters at low latitudes.
Decreased oxygen levels and rising temperatures further threaten marine species.

Island Nations Most Affected:

Island nations’ exclusive economic zones (EEZs) will be significantly impacted by rising calcite compensation depth.
Bermuda’s EEZ could see 68% of its seabed affected, compared to 6% of the US EEZ and 39% of the Russian EEZ.

Global Implications:

Currently, 41% of the deep sea is effectively acidic, a figure that may reach 50% by the century’s end.
The first study on the effects of this acidity on marine life was published only recently.

Source: DTE