Australasian Science: Australia's authority on science since 1938

The Ghosts of Climate Past – and of Climate Future

Different phytoplankton species, including diatoms and algae. Image courtesy of

Different phytoplankton species, including diatoms and algae. Image courtesy of Richard Kirby, Plymouth University

By Kuldeep More & Marco Coolen

Ancient plankton DNA is revealing how marine ecosystems have responded to long-lasting changes in past climate – and enabling us to predict the future.

The full text of this article can be purchased from Informit.

Oceans cover 71% of the planet’s surface and contain an estimated 80% of all life on Earth. Free-floating microscopic plankton represent the majority of ocean biodiversity and are a crucial food source for organisms higher in the food chain, like fish, whales and even humans. For example, the green algae Chlorella and Spirulina are popular green superfoods.

Phytoplankton are green algae that perform photosynthesis. They live in the upper layers of the ocean where they can harvest light. We owe half of the oxygen in the atmosphere that we breath to these tiny creatures.

One of the most abundant group of phytoplankton are diatoms. These have external body armour made from silica, and incorporate 6.7 billion metric tonnes of silicon every year.

Other plankton members feed on bacteria and small phytoplankton. For example, radiolarians consume bacteria or small phytoplankton by filtering sea water.

Then there are plankton that can do both. Mixotrophic plankton such as dinoflagellates feed on other plankton but are also capable of photosynthesis. Being able to live both lifestyles, they have a wide distribution in the ocean.

Plankton sit at the bottom of the marine food pyramid, so any devastating impact on their population could result in the collapse of the entire marine ecosystem. This would affect fisheries, food production and...

The full text of this article can be purchased from Informit.