A copepod (pictured) is a type of zooplankton, a planktonic crustacean distantly related to shrimp and crabs. Copepods are one of the most common and easily recognised types of zooplankton, found in almost every ocean, sea, and freshwater habitat, even in underground caverns. (Photo by NASA/NOAA)
Tiny yet mighty. That’s how the landmark Plankton Manifesto describes these microscopic organisms and the crucial role they play in tackling the interlinked global crises of climate change, biodiversity loss and pollution.
Plankton, a diverse collection of minute organisms incapable of moving against water currents, has been foundational to life on Earth for more than 3.5 billion years. The organisms generate a significant portion of oxygen, absorb vast amounts of carbon, purify water and recycle nutrients that are vital for marine life.
As the base of the marine food web, plankton indirectly support the livelihoods of more than 12% of the world’s population through fisheries and aquaculture, while plankton growths in fresh water affect drinking water availability for millions of people.
The manifesto is the result of a collaborative effort, led by the United Nations Global Compact, which involved 30 international experts from leading institutions and industries worldwide, including South Africa.
It noted how, despite their exceptional biodiversity and the critical roles they play in the global ecosystem, plankton remain “almost entirely absent” from ongoing international discussions related to the blue economy, blue food, blue carbon, national biodiversity strategies and climate change conferences.
“Few plankton-related global programmes are led by leading public agencies, research programmes and international NGOs, as the focus in aquatic sciences is typically placed on visible and more traditionally deemed ‘charismatic’ organisms such as mammals, fish, corals and, more recently seaweed, or to health concerns related to waterborne pathogens,” the manifesto said.
It attributed this lack of consideration of plankton partly to significant knowledge gaps, limited market applications and the complexity of planktonic ecosystems.
A more comprehensive understanding of these organisms would contribute to developing strategies to tackle the triple planetary crises of climate change, pollution and biodiversity loss and to achieve multiple UN sustainable development goals, it said.
Since the onset of life on Earth, the biological activity of plankton has transformed the atmosphere, oceans and lithosphere of the planet, and plankton remain key actors in major planetary biogeochemical cycles.
“They contribute to the water cycle and fix as much nitrogen in the ocean as leguminous plants on land. Sedimented plankton have created the Alps and the building material for the Giza Pyramids and the Hagia Sophia … as well as the chalk we use at school,” the manifesto said.
Plankton are “far and away” the primary producers in the oceans, converting dissolved carbon dioxide in seawater into biomass that supports virtually all marine life and “fix” between 30 and 50 billion tonnes of carbon annually.
“Part of this biomass sinks and is buried in seafloor sediments, sequestering carbon over long time scales and thereby contributing to climate regulation. Over long time intervals, this process generates oil reserves, currently being burned by humans a million times faster than new oil can form.”
There can be thousands of individuals in a drop of water, while many plankton groups have no simple parallels in terrestrial ecology.
“The largest biome on Earth ranges from microscopic entities … to the longest animals on the planet, over 60m for some siphonophores. If the smallest plankton was the size of an ant, the longest one would be the length of Great Britain.”
Massive proliferations, or blooms, of plankton can span several thousand square kilometers across the ocean surface and can be seen from space. As “guardians of biodiversity”, plankton communities sustain marine food webs, meaning disruptions to plankton affect fisheries, aquaculture and tourism.
Increases in harmful algal blooms have an estimated impact of up to $7 billion a year in the US.
The vast majority of the planktonic realm remains unexplored — science has mainly focused on a limited number of relatively conspicuous and easily accessible planktonic organisms, the manifesto said. “We do not yet have a consistent and informed vision of the composition, distribution and dynamics of global plankton communities.”
Human activities have severe impacts on plankton communities by modifying the ocean’s physics and chemistry, for example, through acidification, eutrophication — an increase in the concentration of plant nutrients — and chemical pollution.
“Collectively, these human-induced changes not only jeopardise plankton biodiversity, but also the vast array of marine life that depends on plankton. This highlights the urgent need for concerted global efforts to mitigate these impacts and preserve marine biodiversity.”
Among the key recommendations of the manifesto are measures to improve knowledge to better monitor plankton biodiversity on a global scale.
This includes a call for a global consolidated plankton atlas; developing plankton-based health indices to monitor marine and freshwater ecosystems; creating awareness by means of a global “plankton literacy” project and integrating plankton in international discussions on climate and biodiversity.