Historical and present distribution of Zostera marina in the high north (Troms County, northern Norway) – a decline over the last century

• Published in: Botanica Marina
• Main Authors: Jørgensen, Nina M., Bekkby, Trine
• Format: Article in Journal/Newspaper
• Language: English
• Published: Walter de Gruyter GmbH 2013
• Subjects: Plant Science; Aquatic Science; Ecology, Evolution, Behavior and Systematics; Balsfjorden; Norway; Northeast Atlantic; Northern Norway; Troms
• Online Access: http://dx.doi.org/10.1515/bot-2013-0040; https://www.degruyter.com/document/doi/10.1515/bot-2013-0040/xml; https://www.degruyter.com/document/doi/10.1515/bot-2013-0040/pdf

Abstract Eelgrass meadows ( Zostera marina ) have been mapped in Troms (Norway), in the temperate northeast Atlantic, north of the polar circle, from 2008 to 2011. In this region, there is little knowledge of the distribution of the eelgrass meadows. Northern Norway has an extensive coastline with many pressures and stakeholders. Old records (back to 1900) have been revisited and new locations surveyed based on a combination of spatial modeling, using digital information on depth, slope, and wave exposure and stakeholder recommendations. The results showed that 42% of the previously mapped locations had disappeared. However, we found Z. marina meadows at seven locations where they had not previously been recorded. Most meadows (66%) were smaller than 10,000 m 2 . The largest meadow covered an area of 325,000 m 2 , and was located in Balsfjorden. The results clearly show that Z. marina is able to form actively growing stands even at ∼70°N. Three of the meadows were first registered over 100 years ago, indicating long-lived stands in stable conditions. This study cannot explain the causes for the observed decline, and only discusses possible relations. The eelgrass meadows are genetically isolated but yet diverse. Management at fjord range level is required to maintain healthy and stable stands of eelgrass meadows in this region.