Another Life/Michael Viney: Killary Harbour is Ireland's approximation to a grand Norwegian fiord, its mountains mirrored in deep water rarely ruffled by more than work-boats visiting the blue-barrelled mussel lines, or the stately outings of the Leenane tourists' catamaran. It is intensely peaceful most of the time, while hinting at a vigorous undersea life in its 15km of Atlantic cul-de-sac.
Diving there on July 3rd, however, two marine scientists visiting from Wales found a scene of desolation on the muddy floor of the fiord. As Dr Rohan Holt described it, "all the brittlestars in what was an extensive bed, large molluscs including whelks and scallops, all starfish, all fish (blennies, gobies, butterfish, flatfish, etc) and many of the infaunal species (worms, priapulids, sea cucumbers) were either dead and rotting, or gaping and unresponsive. The only animals that seemed to be hanging on were the common hermit crabs and the organ-pipe worm . . ." It was a scene repeated in many bays and inlets from Galway to Donegal as a massive algal bloom destroyed seabed life, threatened salmon farms and killed commercial shellfish stocks. Losses of oysters, clams and scallops have run into millions of animals.
The bloom was dominated by a single phytoplankton species, Karenia mikomotoi, a microscopic, single-celled organism, named in Japan in 1935. It was first recorded in the north-east Atlantic, off Norway, in 1966, and off south-east Ireland 10 years later. Carried around the world in ballast water pumped in and out by ship it is now a common cause of "red tides" from New Zealand to Europe.
Minor blooms around Ireland's Atlantic coasts have been frequent, but Nasa satellite pictures of this June's exploding tide of cells showed an arc around the north-west that extended 100km out to sea. As lugworms began to die at western shores - a typical early sign of a Karenia bloom - its progress was updated daily by the Marine Institute's phytoplankton monitoring programme.* Not only the scale but the persistence of the bloom have been exceptional. Even late in July, when most of the cells had died and dissipated, Karenia counts were still high in Lough Swilly and Lough Foyle and reports were coming in from Kerry's Dingle Bay of dead mussels and conger eels.
Karenia is a naked dinoflagellate - that is, it lacks a tough wall to its cell. In high concentration - sometimes millions of organisms per litre of water - the cell walls rupture, and toxins harmless to humans sweep fatally through the gills of marine life. When the bloom dies its decay makes huge demands on the water's oxygen level, thus suffocating seabed life: within days of the devastation seen in Killary Harbour, the fiord's dissolved oxygen had plummeted.
Ireland's "red tides" are usually due to winds and currents that push the plankton into the island's bays. But research following a spectacular bloom of Karenia in the western English Channel in the summer of 2003 suggested that sea temperatures and ocean layering can also produce great extensions of a bloom. As the global ocean warms and plankton patterns change, the challenge is to predict the harmful blooms in time to let aquaculture take a healthy harvest.
The death of so much sea life is beginning to litter many western tidelines with the shells and carapaces of marine casualties: crabs and potato urchins have been among the first. With them have come unusual numbers of a creature that has mystified some holiday beachcombers. A Dublin reader, Nicholas Harvey, described finding dozens of them washed up along Keel Strand on Achill: "Each consisted of a soft, fleshy, cream-coloured 'body' about the size of a table-tennis ball. Attached were numerous short 'limbs' (varying in number from two to about seven depending on their size) with a greyish, almost transparent, mussel-like shell at the end which would open gently to reveal countless tiny feet or antennae slowly moving about." These were small colonies of the stalked "buoy" barnacle, otherwise Dosima fascicularis. This is a species of the more familiar goose barnacle that often encrusts drifting logs and crates. The buoy barnacle, while it has used tar pellets and plastics in a similar way, secretes its own float of gas-filled bubbles that looks like foam plastic. This lets it drift on the ocean surface with the shell suspended beneath the water, extending its feathery arms to capture plankton.
Dr Don Cotton, the Sligo naturalist, found hundreds of the barnacles on beaches around north Mayo and in Sligo. On my own strand, when I came to look, only a sprinkle of the animals' empty shells remained. Was Dosima, too, a victim of the Karenia bloom? And when an alien organism explodes its numbers in an ocean warmed up by human activity, do we still have to call it a "natural" event?
http://www.marine.ie/industry+services/aquaculture/advisory+service/phyto.htm