The ramifications of ocean acidification for coralline algae

Scientists have long suspected that coralline algae are particularly sensitive to changes in ocean chemistry. Now, researchers have found that most species of coralline algae studied are negatively affected by ocean acidification.

In a new study published in Global Change Biology, an international team, including researchers from the University of Tsukuba, revealed that lower seawater pH is associated with decreases in the abundance, calcification rates, and recruitment of coralline algae. As levels of carbon dioxide increase in the atmosphere, larger amounts are absorbed by the oceans. The resulting changes in ocean chemistry spell trouble for calcifying species like corals and coralline algae.

Coralline algae are critical species in shallow marine ecosystems globally. By creating calcium carbonate skeletons, these algae act as “cement” for reef systems and provide new substrate for corals and other organisms to settle on. With ocean acidification, less carbonate is available to build these skeletons.

The effects of ocean acidification on different species of coralline algae have been studied for a number of years but the overall outlook for these species is unclear. The team reviewed all available studies on coralline algae and ocean acidification and used a variety of methods to tease out overall patterns.

— source University of Tsukuba | Nov 4, 2021

Nullius in verba


Notes on Carbon Dioxide in Global Warming, Acidified Oceans, and Weathered Rocks

Like CO2 (carbon dioxide), H2O (water vapor) is a strongly heteropolar molecule — having one end with a positive electrical charge, and another end with a negative electrical charge — and absorbs outgoing Infrared Radiation (IR) from Earth’s surface, thus capturing heat in the atmosphere. Homopolar molecules like N2 (nitrogen) and O2 (oxygen) are transparent to IR. Inelastic molecular collisions redistribute that heat (as kinetic energy) to other atmospheric molecules (N2, O2, mainly) and atoms (Ar, He, trace components).

Most of Earth’s surface heat eventually diffuses into the oceans. Heat flows along the heat gradient in the negative direction from warmer air to colder water. The heat capacity (storage ability) of the oceans is IMMENSE (this is where ‘global warming’ ends up), and their heat content takes centuries to diffuse into a stable stratified distribution, rearranged by thermo-haline currents (a solar forcing effect) and by geometry (oceans as a spherical shell with warm equator and cold poles, so ocean heat diffuses poleward).

The fundamental problem of global warming is the ‘excess’ capture of outgoing IR (infrared radiation), reducing the rejection of Earth heat (originally delivered by incoming

— source counterpunch.org | Manuel Garcia Jr | Sep 13, 2021

Nullius in verba


Arctic Ocean acidification worse than previously expected

The ocean takes up large amounts of human-made CO2 from the atmosphere. This additional CO2 causes ocean acidification, a process that can already be observed today. Ocean acidification particularly impacts organisms that form calcium carbonate skeletons and shells, such as molluscs, sea urchins, starfish and corals. The Arctic Ocean is where acidification is expected to be greatest. ocean acidification in the Arctic Ocean is likely to be even worse than previously thought. The results show that the smallest of the seven seas will take up 20% more CO2 over the 21st century than previously expected, under the assumption that the atmospheric CO2 concentrations continue to increase. Ocean acidification negatively impacts organisms that build calcium carbonate skeletons and shells. In sufficiently acidic waters, these shells become unstable and begin to dissolve. A loss of these organisms is likely to impact the entire Arctic food chain up to fish and marine mammals

— source University of Bern | Jun 17, 2020

Nullius in verba