Ostracoda from Hvalfjörður (W Iceland): Diversity, distribution and biomonitoring experiment

Ostracods (micro-crustaceans) are widely distributed, abundant, and sensitive to environmental conditions that make them valuable indicators for human impacts and the reconstruction of palaeoenvironments and palaeoclimate. However, ostracods in Iceland are very poorly studied. To improve knowledge on the diversity and distribution of ostracods in coastal waters of Iceland, 11 sediment samples were collected from 5 to 86 m depth in the fjord Hvalfjörður. In addition, 16 samples were analysed as part of a biomonitoring experiment to investigate whether the deployment of 500 kg of lime-coated wood chips affects the ostracod assemblage over a period of ten months. As a result of the analysis, a total of 19 taxa were identified, with Elofsonella concinna , Sarsicytheridea bradii , Actinocythereis dunelmensis and Robertsonites tuberculatus representing the most abundant species. Propontocypris trigonella , Jonesia acuminata , Cytherura atra and Kyphocythere limicola are here reported for Icelandic waters for the first time. Baffinicythere emarginata and J. acuminata occur in Hvalfjörður probably close to their upper water-temperature-tolerance limits, representing most vulnerable taxa if waters warm due to global change. The deployment of wood chips did not cause significant changes of the ostracod assemblage during the observational period. These results provide important reference data for assessing future changes in ostracod diversity. • Poorly studied ostracods (micro-crustaceans) were investigated in a fjord in western Iceland • A total of 19 taxa was detected including four reported for Iceland for the first time • Baffinicythere emarginata and Jonesia acuminata occur close to their upper water-temperature-tolerance limits, most vulnerable to climate warming • Deployed lime-coated wood chips did not affect the ostracod assemblage over a period of ten months