In the Adriatic Sea there are 20 recorded species of sea urchins, the most abundant of which is the purple sea urchin Paracentrotus lividus (Lamarck, 1816) and the black sea urchin Arbacia lixula (Linnaeus, 1758). Their habitat is a shallow rocky bottom overgrown by algae, which is the primary food source for the urchins. Sea urchins are among the most important herbivores, and thus have a major role in shaping benthic algae communities. The ecology of these communities can be disrupted if sea urchin feeding rates surpass the new colonization and growth of the algae. This scenario can lead to a complete replacement of habitats, from photophilic communities rich in algae, to habitats with dense populations of sea urchins called urchin barrens, a habitat widely spread across the Adriatic. Urchin populations have become unstable due to a release from predation pressure thanks to a decline in their predators, and this can drive this regime shift and dominance in urchin barrens. This project aims to map patterns in urchin density, size structure and diversity around Silba island, to identify sites covering a gradient of overall urchin pressure. These sites will be used to assess benthic community structure, with a particular focus on macroalgal cover, to quantify the impacts of urchin densities on benthic communities. Students could also survey predator species to determine whether there is evidence for a cascade effect, where predator declines have stimulated booms in urchin numbers and subsequent loss of macroalgal coverage.
If you would like to do a dissertation or thesis with us but your university hasn’t started dissertation planning or the project selection process, that’s no problem. You can cancel your expedition with zero cancellation charges up until the 15th of April of if you provide documentation from your university saying that they won’t support completing a dissertation project with us.
The Krka Valley runs from the Dinaric mountains bordering Bosnia to the Adriatic and is only 77km in length. However, since the river runs through limestone there are some spectacular gorges and this is one of the most scenic river valleys in Europe. It is also important from a biodiversity viewpoint containing nine Croatian and three Krka endemic fish species and spectacular cave systems containing a number of potentially new species to science. Opwall together with Biota (a Croatian biodiversity research organisation) has built a research centre in the central part of the Krka valley with easy access to the whole park. The centre is based in a restored house and grounds within 100m of the park boundary and has access to all the habitats throughout the park and surrounding countryside. The National Park Authority have requested we perform baseline surveys to increase the known inventory for the Park, as well as collect long-term monitoring data to answer a series of their management questions.
Tourist visits to Krka National Park are heavily concentrated towards the lower stretches of the river and very few people visit the central and northern parts of the valley. The Biota/Opwall research centre is based within a rural community that has suffered from significant depopulation and land abandonment in recent years. The centre is designed to give benefits to the local community from the visits (e.g. provision of employment etc). Whilst the main research effort each year from this centre comes through the Opwall programme, the centre will remain open year round in an attempt to attract some of the many visitors to the Croatian coast further inland, increasing revenue for the Park and local communities.
Silba Island is in the northern Dalmatian archipelago and is a car and hotel free island. The island markets itself as a haven of tranquillity and much of the island is still covered by Mediterranean black oak and maquis. The objective for our partners on this island is to develop the first marine research centre for northern Dalmatia and they have a series of research projects on seagrass, sea urchins, protected species and fisheries, as well as marine plastics.
Most of our volunteers fundraise for their expedition costs. Find out more.
Croatia is hot during this time of the year! In both Krka and Silba the daytime temperature rarely drops below 30 degrees and can reach 40 degrees.
Fitness level required
Moderate. Whilst there are not many steep hikes in the forest, the hikes are still quite long and the temperature can make them tiring.
At Krka you will either be staying in dormitories or in shaded tents with shared western style bathrooms and toilets. There is also some limited phone signal in Krka (but not reliable for a data connection).