Another Life: The colour of the sea changes as the sun lifts over the ridge: pale aquamarine at first, like a mirror of metal or silk, then a rich deepening and darkening to ultramarine, writes Michael Viney
When an east wind flattens the shallows, the early sunlight bounces off the sandy bottom, scattering a turquoise glow through the water. Reflections of sky, absorption of light: all the blues of the sea, both above and below, are part of the game the light plays with the ocean.
From a satellite, things can look different again. Since late March a greener tint has been mixing into the indigo of the deep Atlantic, a colour-change actually mappable as the spring bloom of phytoplankton sweeps north from Spain to Irish waters. The changing light and warmth that stirs the growth of grass ashore also wakes the drifting, single-celled plant life of the temperate ocean. This vast event should be part of our awareness of how the world works, but being out of sight, stays out of mind.
The green is chlorophyll: a spark of new life in each of the billions of cells that float within the top 50 metres of the sea, a gleaming emerald in the crystal lattice of each microscopic diatom. There can actually be more living matter photosynthesised in the ocean's "meadows" than is made by the plants of the land - perhaps 30 tonnes per hectare. And just as leaves feed the insects, birds and animals ashore, phytoplankton nourishes the whole food chain of the ocean, from the smallest fish larvae of the zooplankton up to the largest whale.
The spring bloom draws not only on sunlight and carbon from the air, but on minerals stirred up from the sea-bed by winter storms and upwelling currents. Thus energised and fertilised, the diatoms divide in an exponential explosion, doubling their numbers in a day or two and multiplying perhaps 10,000-fold in a fortnight. As the water calms and warms into summer, they are joined by billions of dinoflagellate cells, each with a tiny whip, or flagellum, to drive it through the water. Their summer blooms can bring murky brown and yellow pigments into the chlorophyll greens of the sea, and the toxins in some species can destroy aquaculture industry stocks or make them unfit to eat.
Anything that changes the grander patterns of phytoplankton, affecting its abundance, its swirling aggregations, the seasonal succession of species, can have huge implications for the life of the sea. Over the past few decades in the north-east Atlantic, cold-water species of plankton - both phytoplankton and zooplankton - have retreated northwards and warm-water species have moved after them, sometimes by as much as 10 degrees of latitude, or from Cork to the Shetlands. The changes have been so big in the past 20 years that marine scientists call them "a regime shift" - and one clearly forced by global warming.
The monitoring of toxic species arriving in our bays has been a routine job for the scientists of the Marine Institute, but the new trends and uncertainties demand something wider and even more detailed. The importance of plankton - both the plant cells and the minute zooplankton that feed on them - to the food web and the fishing industry has long been obvious to science.
But the intensity of checks needed now would be difficult and costly by ship. The EU Biocolor project, involving the Martin Ryan Institute at UCG, the Marine Institute and several European partners, is working on new ways to monitor the development and movement of phytoplankton populations. It aims to detect the types and quantity of phytoplankton by monitoring how they affect the different wavelengths of light in the surface of the sea.
This will be measured by instruments on satellites, ships and optical buoys. So that's pretty smart. But I am touched by some other research about phytoplankton. In the discovery of holes in the ozone layer, caused by human industrial activity, there was worry that the increased ultra-violet radiation would damage phytoplankton, perhaps disastrously from the human point of view. But it seems that the plant cells may have a feedback mechanism that shields them from harm. In periods when the sun's harmful ultra-violet rays are especially strong, phytoplankton near the sea's surface releases higher quantities of a sulphur compound called dimethylsulfoniopropionate, or DMSP. Broken down by bacteria and carried into the air by evaporating water, this creates dust particles that promote the condensation of clouds - shutting out the U/V rays; thus returning to the land, in rain, the sulphur essential to the health and growth of plants.
Here, phytoplankton takes its place in the paradigm of earth as Gaia, an infinitely intricate, self-regulating organism.