I have a document on my computer called ‘Big science words to bandy about’, although it could equally be called something like ‘Words that make me sound like I know what I’m doing’. This isn’t entirely a joke.
When I did my first degree, in journalism, PR and multimedia, I was in my 40s. I remember thinking at the time about my poor brain, and how going back to study felt a bit like taking an old piece of machinery that had been sitting unused for years. All the cogs and wheels in my brain seemed rusted up. But gradually I cranked those cogs and wheels into life. Creaking and groaning, they slowly began moving again. Then turning. Then actually spinning. By the end, I rather fancied they were quite shiny little cogs doing some possibly useful work.
Anyone who has been a mature-age student will recognise themselves when I say I diligently attended every lecture – unlike quite a few of the kids. I began to notice that lecturers and tutors tended to have favourite buzz words. As they lectured, I would write them down in my diary and when I did my assignments I’d make sure a few were sprinkled throughout. That way, I reasoned, we would be speaking the same language.
Later – in my 50s – came a postgraduate diploma in writing, editing and publishing. Now – in my 60s – I find myself doing a PhD in marine science, a long way from any previous experience and even further in time since I did my A levels. But that habit of jotting down useful words, or that I haven’t come across before, has stayed with me. There are quite a few, let me tell you! The process of recording them helps me to learn and understand rather than just making an assumption about what they mean.
Hence the document.
All of which is a long story about one word that found its way onto my list: ‘rugosity’. Rugosity comes from the Latin noun rugositas, meaning ‘wrinkledness’ or ‘roughness’ and, according to the Oxford English Dictionary, it was first used in English in around 1599.
I’d never come across it before I started my PhD, but reef researchers use it a lot. Once you know what it means, it is actually a very useful word.
Rugosity is one way of describing how rough, uneven and three-dimensional a reef surface is – all those lumps, bumps, holes, crevices, ledges and coral branches that make one patch of reef very different from another. A bit like the alleys, lanes and streets of a country town, where all the houses, cottages, bungalows, villas and apartments look a little different.
No heterogeneity here!
Habitat, hidey holes and fish
East-Australian Stripey - Microcanthus joyceae
Painted morwong - Morwong ephippium
Wrasse, various
Blackspot sergeant - Abudefduf sordidus with a moon wrasse - Thalassoma lunare
Chestnut eyelash-blenny - Cirripectes castaneus
Piano fangblenny - Plagiotremus tapeinosoma
Butterflyfish, various
Butterflyfish, various
Which brings me to another phrase researchers use a lot: ‘structural complexity’. It sounds scientific, but really it is just means how much three-dimensional stuff is going on. A flat, fairly featureless bit of reef has low structural complexity. Add coral heads, branching corals, ledges, holes, crevices, overhangs and all the other lumps and bumps of a reef and things become much more structurally complex.
And all those different nooks and crannies create habitat. A des res, if you will. With fish appeal!
A tiny fish might make use of the spaces between the branches of a coral. Another might disappear into a hole. Some shelter under ledges. Others stay close to a coral head so they can duck for cover when necessary. What counts as useful structure to a fish also depends on its size – a hole that is excellent real estate for a blenny isn’t much use to a larger fish.
Researchers can actually measure this structural complexity, and rugosity is one of the measures they use.
The traditional method is seriously low-tech. A fine-link chain is laid over the reef so that it follows all the lumps and bumps, and the length of chain is compared with the straight-line distance it covers. On a flat surface the two measurements are much the same. On a more convoluted reef, the chain has to travel much farther to cover the same straight-line distance.
Chain-tape rugosity illustration. Image adapted from doi:10.371/journal.pone.0050440.g002 (Friedman et al., 2012) – the low-tech way to measure rugosity
These days researchers can go considerably further. By taking lots of overlapping photographs from different positions and angles, they can use photogrammetry to build detailed three-dimensional models of the reef. From those virtual reefs they can measure things such as surface area, height, slopes and complexity at different scales.
So they really are pulling the rugosity from out of the reef.
I see the difference myself when I put out my research cameras. Some patches of reef are busy with fish while others can be surprisingly quiet. Often you can look at the habitat around a camera and have a fair idea which places are likely to be the busy ‘town squares’ and which will be quieter backwaters.
And that brings us to channeling your inner fish.
This knowledge has changed the way I look for fish when I am out swimming. Don’t laugh, but I really do channel my inner fish.
If I were a little damselfish, where would I stay close to shelter? If I were a blenny, which little hole would I claim? If I were a wrasse, where might I duck out of sight?
So next time you are snorkelling, don’t just look for fish. Look at the reef itself.
Then channel your inner fish.
Stout moray - Gymnothorax eurostus
A structurally complex section of Norfolk Island’s reef
References
Friedman A, Pizarro O, Williams SB, Johnson-Roberson M (2012) Multi-Scale Measures of Rugosity, Slope and Aspect from Benthic Stereo Image Reconstructions. PLoS ONE 7(12): e50440. doi:10.1371/journal.pone.0050440