The American quantum physicist John Archibald Wheeler once said: “We live on an island of knowledge surrounded by a sea of ignorance. As our island of knowledge grows, so does the shore of our ignorance”. He was talking metaphorically but, last week, I stood on the shore of a sea loch in Argyll with a very literal interpretation of Wheeler’s words churning through my mind. Most of us gaze at the surface of the sea with very little sense of what lies beneath. What we do know comes mostly from natural history documentaries which, in turn, tend to focus on the extremes of the biological world, whether in terms of bizarreness, anthropomorphism, violence or beauty. We may paddle in rock pools and get a sense from what is exposed at low tide of a fecund underwater world, but rarely get – or take – the opportunity to enter into that world ourselves.
In many ways, that encapsulates my creed for this blog: finding the extraordinary that lurks right under our noses without us noticing. But most of my posts are about the freshwater world and, when it comes to marine life, my island of knowledge is small, and the surrounding sea of ignorance is vast. However, last week I had an opportunity to rectify that and, after squeezing into a wet suit and donning a mask, snorkel and flippers, I slipped into Loch Caolisport, on the west coast of the Kintyre peninsula in Argyll. “Slipped” is, perhaps, disingenuous: it was more of an undignified crawl, due to the awkwardness that flippers confer on the hitherto straightforward act of walking. As soon as I was a few metres from land and able to push off and float in the water, however, I became part of this new world.
The first impression is of the extraordinary quantity and variety of the seaweeds on the seabed. We are used to seeing a narrow fringe of exposed seaweeds, floppy and flattened on rocky shores when the tide is out; we are less used to seeing them buoyant and supported by the water. But seaweeds, like many amphibious organisms, are as elegant in one medium as they are awkward in another. Think how ungainly a seal is when it hauls itself on land, yet how sleek they are when seen swimming underwater. The kelps were in their natural habitat whilst I was the ungainly intruder.
Brown seaweeds clearly dominated the assemblages but many of the growths of sea oak (Halidrys siliquosa) were covered with tufts of a red alga Ceramium. I saw crusts of the red alga Hildenbrandia (a relative is common in rivers: see “More about red algae”) and there were a few tufts of green algae too. The wracks, the seaweeds I most associate with rocky shores, were, by contrast, noticeable by their absence. They are mostly species of the intertidal zone and the areas that I was swimming through were permanently submerged. Further away – too far for a timid first-time snorkeller to contemplate – there were beds of sea grass that others in our party explored.
Rising above the other algae were graceful fronds of another brown alga, Sargassum muticum. Some of these were almost two metres tall, with a central stem and many laterals, each divided several times to give a fern-like appearance. Closer inspection revealed the presence of many small air bladders (“aerocysts”) which make the whole plant buoyant. These bladders are, in a way, equivalent to tree trunk as both share a primary purpose of raising the plant above the other vegetation to capture as much light as possible.
The curiosity of Sargassum muticum, however, is that it shouldn’t be here at all. It is an invasive species, originally from Japan, that has spread around the world, possibly as the Pacific Oyster was introduced for cultivation. The first record of S. muticum in the UK was in 1973, but it is now widespread. However, the first time snorkeller may be forgiven for not knowing this: for them it is one more constituent of these magical underwater gardens. You don’t know that it should not be there, unless someone tells you this. You cannot depend entirely on sensations to make judgements about the environment; you need information too. More particularly, in this case, you need evidence that it was once absent. I recall a similar circumstance, walking with a friend on a riverbank near our home in Durham. She had grown up seeing riverbanks bordered by dense stands of Himalayan Balsam (Impatians glandulifera) and had no idea that these, too, were recent arrivals, only becoming widespread in the last 30 years or so. I had experienced the change; she was dependent on other people’s testimony. Some older marine biologists must remember these waters before Sargassum muticum intruded but, for most, it has become just one more fixture in the underwater panoramas that greet the intrepid explorer of Argyll’s fecund fringe.
Note
The picture at the top of this post shows Claggain Bay on the west coast of Islay, not Loch Caolisport. It is hard to take good photographs of water bodies from a low standpoint and there was a rocky promontory at Claggain Bay that afforded a fine view across, whereas the immediate surroundings of our location beside Loch Caolisport had relatively low relief.
Thanks, too, to Paul Brazier for gently correcting some of my original identifications.
Some other highlights from this week:
Wrote this whilst listening to: Amy Winehouse. The 10th anniversary of her death.
Cultural highlights: Rewatched Quentin Tarantino’s Once Upon a Time in Hollywood (see below)
Currently reading: Quentin Tarantino’s novelisation of Once Upon A Time in Hollywood. Cleverly written in a faux-pulp fiction style, it actually serves as a “Director’s Cut” for the film, adding in some extra background details about the characters.
Culinary highlight: Islay single malt whisky (see above).
microscopesandmonsters 