Julian Evans
Ecosystems depend on biodiversity to function, and consequently,so does human wellbeing. This is one reason why calls for conserving biological diversity have gained international momentum in recent decades, so much so thatthe United Nations declared 2010 to be the International Year of Biodiversity - a celebration of life on earth and of the value of biodiversity for our lives.
Marine ecosystems are a major storehouseof biodiversity, and it is therefore of concern thatmany marine habitats are being placed under increasing pressure due to various human activities.It is becoming more and more urgent formanagement systems to be set in place to ensure sustainable use of the marine environment, especially the coastal zone, where most human activity in the marine environment takes place. Naturally, knowledge on the distribution of biological diversity must form the basis of management plans if these are to be effective at protecting biodiversity!
In the Mediterranean, a lot of research effort has gone towards the study of particular habitats deemed to support a high species richness, but this has occurred at the expense of other habitats. Pebble beds, for instance, tend to have a small coverage and lack any large erect algae, thus appearing denuded compared to seagrass meadows or rocky platforms with algal canopies. Consequently, pebble beds are generally considered to be impoverished and have been little studied. Recent research undertaken by Dr Julian Evans as part of his doctoral studies in association with the Department of Biology of the University of Malta challengesthis view. Interest in this habitat was sparked by the rediscovery in pebble beds of the Maltese Topshell, a marine snail that is endemic to the Maltese Islands, suggesting there is more to this habitat than first meets the eye.
To assess the diversity of pebble beds, systematic sampling of this habitat was undertaken at 15 sites around the Maltese Islands. The samples were painstakingly processed, leaving no stone unturned (literally!) to collect any animals present, which were then meticulously identified to species level. The results of this work were astounding: over 60,000 individuals belonging to no less than 360 different species were recorded from a combined sampled area of 16m2, clearly indicating that pebble beds are much more diverse than previously thought. Around half of the individuals were spirorbid polychaetes - very small worms that live in a coiled tube cemented to the surface of the pebbles. In terms of species, molluscs (snails and bivalves) and crustaceans (animals with an exoskeleton and jointed legs) that live in the interstitial spaces between pebbles were the most common. Three new populations of the endemic Maltese Topshell were discovered, confirming the importance of pebble beds as a habitat for this species. In addition, three species of gobies (small bottom-dwelling fish), which had never been previously recordedin the central Mediterranean area, were also found within the studied pebble beds.
Contrary to the prevailing view thatpebble beds are impoverished, these findings indicate that they are rich and diverse habitats having a higher conservation value than generally thought. This, together with the overall rarity of such habitats (in terms ofcoverage), suggests that the occurrence of pebble-bed habitats should be taken intoconsideration when formulating management plans for safeguarding biological diversity in the coastal zone.
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Dr Julian Evans is currently a visiting member of staff at the Department of Biology of the University of Malta, and can be contacted via email on [email protected]. He was awarded the degree of Doctor of Philosophy by the University of Plymouth in recognition of his work on the ecology of pebble beds. This research was supported by a Strategic Educational Pathways Scholarship (STEPS), part-financed by theEU's European Social Fund under Operational Programme II - Cohesion Policy 2007-2013: 'Empowering people for more jobs and a better quality of life.'