Wales in ‘Bloom’ – Springtime Under the Sea
Early spring is an exciting time of year; buds
break on trees, birds start singing and lambs playfully jump about
in the fields, but readers may not be aware that springtime also
brings great changes to our coastal waters. Just like on land,
there is the steady revealing of tones and textures that herald the
beginning of a new year in nature.
The first signs of the marine spring will come with a change in
the look of the sea. Winter storms churn the sea into a murky mass
of sand and silt, which is rich in nutrients. With the increasing
sunshine, these nutrients will provide sea creatures with a
plentiful supply of food. Most of these creatures are tiny
microscopic plants and animals known, respectively, as phyto- and
zoo-plankton, and there can be many thousands in one bucketful of
seawater.
The zooplankton rises to the surface at night to feed, and when
disturbed some give off a display of sparkling light, which it is
thought they do to confuse predators. One of them, found in the
Menai Straits, is called seasparkle (Noctiluca scintillans), and,
when shaken in a bottle, will glow so brightly it can light up a
dark room! This ‘Bioluminescence’ provided superstitious sailors
with tales of magic; and, as Samuel Taylor Coleridge (1772 – 1834)
found, when the seasparkle was seen whilst crossing the Menai from
Caernarfon, it also provided a rich source of poetic
inspiration:
About, about, in reel and
rout
The death-fires danced at night;
The water, like a witch’s oils,
Burnt green, and blue and white.
This springtime phenomena is called the ‘spring bloom’ when the
numbers of plankton feeding on the suspended nutrients rise
dramatically and give the seas around us a green, turbid, look. Dr.
Rohan Holt, a marine biologist working for CCW, says, “Diving is
virtually impossible during the bloom because the visibility is so
poor – it’s like working in a blizzard. We normally wait until May,
when the bloom has died down and visibility is much better – and
the sea is warmer!”
Says Dr. Holt, ‘This planktonic ‘‘soup’’ is the food for so many
things in the sea, and especially the masses of simple creatures
and plants that live on the seabed. The soft corals, anemones and
sea firs all unfurl or renew their catching tentacles in the spring
to make the most of this feast of plankton’. The plankton is also
an essential food for our many fish species, such as mackerel and
herring, which will shortly be migrating in big shoals from their
winter feeding grounds to the shallow coastal waters.
Siôn Williams, a fisherman, who operates a fishing boat off the
Llyn peninsular, says, ‘Spring is a good time for me. In winter, I
rely on catches of lobster and crab (W. cimwch + cranc) but I
always look forward to the springtime, when I catch fish again. I
will also see dolphins in the spring and summer. When this happens
I stop the engine and watch them as they feed on the herring (W.
penwaig). It’s a fine sight’. But Siôn is less happy to see the
blooms of plankton, which cover his pots in a ‘green slime’.
This feature is one in a series published by CCW in support of
“Sea Britain 2005” – a year long festival that explores every
aspect of our rich maritime heritage, and seeks to encourage us all
to ‘take a fresh look at the sea.’ Find out more on the website:
www.SeaBritain2005.com
If you would like to know more about the Countryside Council for
Wales and the work it does in the countryside and inshore waters
contact the Enquiry Unit on 0845 1306 229, or visit the web site
(www.ccw.gov.uk)