Marine chemistry articles from across Nature Portfolio

River sediments play a critical role in sustaining coastal ecosystems. This study examines patterns of coastal suspended sediment concentration (SSC) for 349 deltas worldwide via satellite images and investigated the possible driving factors.

A proxy is developed for oxygen levels in seawater, based on U-Pb dating of dolomite. It shows a step-increase in O2 400 million years ago, suggesting that oceans were largely oxygen-limited at the ‘dawn’ of animal life.

After intense winter cooling 2012-2015, Labrador Sea convection continued to intensify to 2018, and subsequently weakened and shoaled due to polar vortex collapse and Arctic sea ice loss, as analyses of Argo-float and ship-based measurements show.

The coastal ocean is a dynamic environment, and CO₂ uptake is increasing faster than in the open ocean. Incorporating coastal processes into a global model shows that biological responses to climate-induced circulation changes and riverine nutrient inputs are key to the enhanced uptake.

A geochemical study of an ancient mass-extinction event shows that only moderate expansion of oxygen-deficient waters along continental margins is needed to decimate marine biodiversity. This finding provides a stark warning of the possible consequences of human-driven ocean deoxygenation on life in Earth’s shallow oceans.

Blue carbon will not solve climate change. The effect is too small; existing sediment carbon stock is a liability; and there is a timescale mismatch between ancient fossil fuel emissions and uptake by vegetation. Clearer communication would support informed decision-making.

Deep-sea acidity data combined with ice-core carbon dioxide records reveal that an interplay between the two polar regions modulates ocean ventilation through various modes. These modes explain past variations in deep-sea carbon storage and atmospheric carbon dioxide on millennial timescales.

The new ‘High Seas Treaty’ adopted by the United Nations on June 19, 2023, leaves a lot open to question but does establish several historic benchmarks for protecting the high seas, setting the stage for further scientific exploration and paving the way for more effective marine conservation. This Comment describes what we know and do not know about the Treaty at this point. We know that the Treaty is about resources, equity, conservation, and diversity. What we are lacking are more specifics about how the Treaty would be implemented in practice. Such specifics are passed on to future working groups and a Conference of Parties.

Yingchu Shen discusses the use of deep-sea stony coral geochemistry as a long-term record of ocean temperature, acidity, and nutrient levels.

Restoring coastal vegetated habitats can remove carbon from the atmosphere and store it as organic matter in sediments. A study now shows that these habitats also support seawater to store more carbon, and for longer, in its dissolved inorganic form.