Wednesday, 23 March 2011

Dipping Toes In A Spring Tide

Water may cover approximately 70% of the surface of the Earth, yet it only accounts for around 15% of all the different species of birds, plants and animals found on the planet. Even then, only 2% of these creatures exist in the open ocean. The sea around the Isle of Mull’s 305 miles of coastline is particularly biodiverse, yet only a fraction of its wildlife is ever seen by the thousands of eco-tourists that visit the island every year. A recent walk that we enjoyed in North Mull coincided with the advent of the ‘Super Moon’, with its extra-high perigean tides, and helped bring Mull’s marine environment sharply in to focus.

Even during the calmest of days, the sea around the Isle of Mull is constantly moving, as the gravitational pull of the sun and moon acts upon the tidal range of the island. At the time of the ‘Super Moon’, this pull was enhanced, as the sun and moon aligned with each other to produce exceptionally high ‘Spring’ tides. Unfortunately, with a cloud coverage measuring the full eight oktas, the overcast conditions meant that, here in Tobermory, we weren’t able to enjoy the 14% larger and 30% brighter ‘Super Moon’ this time around and may have to wait another 18 years to do so!

The sea around Mull may appear quiet and devoid of much in the way of marine life at present, yet in a few short weeks the same body of water will support returning populations of seabirds, Minke Whales and Basking Sharks. The Isle of Mull’s oceanic environment is heating up, as indicated by changes that are being noted in the status and distribution of the island’s apex sea predators. The warming of the sea off the island has resulted in cold water plankton being replaced by the arrival of less nutritious micro-organisms, which are having any adverse effect on the small fish that seabirds and Minke Whales (baleen plates pictured below) rely on. Increasing numbers of Basking Sharks appear to be the main benefactors, as they follow these warm water plankton blooms in Spring and it may well be that these cartilaginous fish are becoming the new Minke Whales for boat trip operators on Mull.

The higher than usual tides have provided an added bonus for wildlife watchers on the island, pushing shorebirds much closer to roads that fringe many of the island’s sea lochs. Views of several waders that have only recently returned to Mull at the onset of another breeding season have been quite exceptional. Displaying Lapwings have been particularly demonstrative as they tumbled through the air, forever accompanying their aerial contortions with the sound of their wheezy, plaintive voices. To many simply a black and white bird, the light refracted on the upperparts of this female shows the true (and beautiful) iridescent purple and green sheen of their plumage to wonderful effect.

The smell of seaweed cast up on the shores of Mull’s coast is something that is taken for granted today by those that live their everyday lives by the sea. In the past, seaweed played a vital role in the domestic economy of the island, providing food for humans, fodder for cattle and sheep and ‘green’ manure for crops. Some were eaten raw or cooked in stews, soups and puddings and the ash extracted from burnt seaweed formed the basis of the kelp industry on the island during the 19th Century. Many marvel at the colours, textures and shapes of the many varieties of seaweed that the tide throws on to Mull’s shores on a twice-daily basis, yet few could possibly imagine the hardship and suffering that the gathering of algae caused to the island’s earlier residents when the once prosperous kelp industry collapsed.

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