August 6th, 2019
At the foundation of the ocean food web, plankton are critical to all life in the ocean. Policy & Communications Intern Bec tells us the power these microscopic creatures have in our oceans and beyond the shoreline.
SMALL BUT MIGHTY
Like all parts of the microscopic world, I find plankton intriguingly beautiful. Perhaps it is the poetry of discovering their delicate detail only through a microscope, while knowing their mighty impact on the oceans, earth and our atmosphere.
Plankton are the microscopic organisms all other marine life depends on. Named after the Greek word ‘Planktos’ meaning ‘to wander’, these tiny organisms cannot actively move and so float around our seas, traveling where currents and tides carry them.
Phytoplankton are the primary producers of our oceans, meaning that they photosynthesise to make their own food and release oxygen as they do. While they account for less than 1% of the world’s photosynthetic biomass, phytoplankton are so prolific as primary producers that up to 80% of the oxygen currently in our atmosphere has been produced by their photosynthesis.
They also, crucially, help to trap carbon into the sedimentary layers on the seabed when their calcium carbonate shells drift to the ocean floor after they die.
But not just big on impact, plankton are visually impressive. Emiliania huxleyi – a single celled, photosynthetic coccolithophore can be seen from space. In the correct oceanic conditions E. huxleyi ‘bloom’ in their billions, to cover sea surface areas larger than 10,000km². Their calcite shells reflect the light and can be seen as beautiful bright blues in satellite images.
My passion for plankton isn’t new. During my thesis I stared down a microscope for days on end, counting thousands of foraminifera fossils in sediments collected from the Southern Ocean seabed. My supervisor lent me his *knitted* scale model of a Globigerina bulloides (a particularly prolific planktonic foraminifera) to sit on my microscope as I worked.
The tiny plankton I counted helped my research group determine how sea surface temperature in the Southern Ocean had changed since the industrial revolution. They also contributed to our thinking about how climate change will impact even the ocean’s smallest residents, as many plankton species can only exist within very limited environmental conditions where ocean nutrients, sunlight, pH and temperature are just right.
Now I’m here in Bristol, having wandered 10,000 miles from Australia to pursue different passions, and the plankton pop up here, too.
PLANKTON POWERED FISHERIES?
So how are plankton relevant to fisheries management? It all comes down to ‘who’s eating who’ or: how energy transfers through the oceanic food web.
In areas of ocean upwelling, ocean currents force nutrient-rich deep water up into the sunlit surface waters where phytoplankton live. Phytoplankton photosynthesise to turn these abundant nutrients (and dissolved carbon-dioxide) into their food, and consequently they can reproduce on epic scales – known as plankton ‘blooms’.
Zooplankton will eat the prolific phytoplankton and fish larvae eat them too, and so energy transfers up the oceanic food web to ultimately produce more, well-fed adult fish. Coastal waters where nutrients run off the land can induce similar blooms that increase the stock of commercially important coastal or estuarine species.
So could we use innovative technology (like colour-sensing satellites that can monitor phytoplankton blooms) to capitalise on the energy created from a plankton bloom to direct fisheries effort towards rich, healthy fish stocks?
Yes, in theory. If a bloom was spotted by satellite, and sufficient time was allowed so plankton-eating fish grew into legally sized stock, fisheries managers could direct increased fishing effort towards these blooming areas.
In practice, however, researchers are still investigating the cause and effect of algal blooms, and fish will keep on swimming. Even the most responsive or well-funded fisheries managers may find fishermen unwilling (or unable) to relocate their fishing efforts on a monthly, yearly or irregular basis just to follow those wandering, blooming plankton.
Perhaps a more effective way for policy makers to ensure prolific algal blooms are converted into sustainable seafood catch, would be to include areas prone to algal blooms when designating marine conservation areas. The flow on effects of this could have massive benefits for environmental and economic sustainability of marine environments and fisheries.
A BIG THANK YOU TO TINY PALS
Only 200 miles east of my new home here in Bristol are the Cliffs of Dover. Their white chalk is old. It formed in the Cretaceous period when billions of blooming coccolithophores died and their shells sunk to the seafloor. In the 66 million years that passed, metamorphosis and tectonic movements transformed the shell sediments into those famous chalk cliffs.
Today, the trapped carbon in the white chalk of the cliffs is literally crumbling away as the cliff face erodes at a rate of 22-32cm each year – faster in these past 150 years than in the thousands of years before. Climate change, fiercer storms and poor human management are likely to blame.
In this changing climate we need to care about plankton. And for supporting the entire ocean food web, producing the oxygen we breathe, and trapping carbon on the seabed and in the chalk of cliffs, I think the least they deserve is a little credit.