When I signed up to a trip to Cyprus in late March I was anticipating feeling some warm Mediterranean sun on my skin after the ravages of the British winter. I did not expect snow and sleet. However, as one of our destinations was the Troodos mountains, the location of Cyprus’ only ski resort, maybe it was a case of unrealistic expectations. Fortunately, we realised our mistake just in time to pack some warm clothes, and the unseasonable weather did, at least, mean that the spring flowers at lower altitudes were, even by Cypriot standards, particularly impressive.
I was in Cyprus primarily as a camp follower on a reconnaissance trip for a geology and botany excursion next year. Cyprus is, to put it in layman’s terms, the outcome of a collision between the African and European continental plates. The Troodos mountains are a geologist’s paradise, having a wide range of features arising from this and from associated volcanic activity. As the molten rocks cooled, minerals precipitate out and the resulting geological strata reflect differences in the melting points of these minerals. Some of these minerals, such as chromite, are commercially valuable and have been mined for centuries. Indeed, the name Cyprus itself is derived from cuprous, the Greek word for copper, which was mined here since 4000 BC.
The Hadjipavlou mine is set amidst pine forests close to the highest point of the Troodos. It was an active chromite mine from 1950 to 1954 and from 1979 to 1982 but was abandoned when cheaper sources of chromite became available in South Africa. Over a million tonnes of ore were extracted in the period when the chromite mines in the area were active, but now there are few obvious signs apart from this adit driven into the hillside. A small stream bearing water that has percolated through the rocks and collected in the mine’s galleries emerges from the mine entrance and tumbles down the hillside to join the stream below. This, on closer inspection, has some quite interesting microbial growths.
First of all, having been told that this is a chromite mine, you might expect the water to carry toxic concentrations of heavy metals. So you might also be surprised to see abundant growths of bright green algae thriving in the stream immediately downstream of the mine entrance. This is, in fact, a common phenomenon in mine waters and happens, we think, because the fast-growing algae evolve metal tolerance whilst the animals that feed on them are slower to adapt. This is, literally, survival of the fittest and, with nothing to eat them, the algae grow prolifically.
These filaments belong to the genus Tribonemawhich, despite being bright green in colour, actually belongs to the yellow-green algae, the Xanthophyta, rather than to the green algae. This group is actually more closely related to the diatoms than to the green algae, though it can be hard to understand why simply by peering through a microscope. One useful test is to add a little iodine solutionto the slide: this binds to the starch inside green algae cells, staining them a dark brown colour. The Xanthophyta, by contrast, do not have starch as their storage product so the cells are not stained by iodine. The only other member of this group that I have discussed in this blog is Vaucheria, a very different alga (see “Who do you think you are?”).
Tribonema cf affinein the channel draining the Hadjipavlou chromite mine in the Troodos mountains, Cyprus, March 2019. a. close-up of the alga in situ; b. microscopic view of filaments; c. fragments of disintegrated filaments showing the H-shaped cell endings. Scale bar: 10 micrometres (= 100thof a millimetre).
Tribonemahas simple, unbranched filaments with two or more plate-like chloroplasts arranged around the cell periphery. One other feature is the arrangement of the cell wall, which tends to consist of two overlapping halves. When filaments disintegrate (as they often do) the fragments have an H-shape, with each end forming half the cell wall of a different cell. The cells are, in fact, cylindrical but this is not apparent with the flattened perspective of a high magnification objective. This feature is not universal in the Xanthophyta, nor is it unique to this group (a few green filamentous algae show the same characteristic) but it is a useful hint that you may be looking at Tribonema.
Whilst lush growths of algae is a common feature of streams draining mines, the species that form these growths can vary. In the northern Pennines, I am used to seeing green algae in these habitats, but there are at least three different genera that I find. Typically there is just one filamentous alga in this location, and they tend to be constant over time: they are reliable sources for material for undergraduate practical classes as a result. There is more to this story but I will have to come back to it at some point in the future. .
There is also more to the algal flora of the Hadjipavlou chromite mine but, again, that will have to wait for another post. I should also confess that, although I visited the mine briefly last year, these samples were collected by Heather, whilst I was sitting snugly below the snow line.