Telomeres are relevant molecular tools acting as relevant proxies of individual quality, lifestyle and lifespan of living organisms. Telomeres are non-coding DNA-protein complexes located at the end of linear chromosomes playing critical roles in maintaining and ensuring genomic integrity and stability. They progressively shorten along life, but their attrition is accelerated by a wide range of environmental stressors. When telomere length reaches a critical lower threshold, cell division can damage coding DNA leading to apoptosis or cellular senescence. Chronic stress, including changes in environmental conditions and demanding biological processes, has been shown to speed up telomere shortening thus reflecting the physiological stress. In that context, their use as stress proxy in ecology and environmental science has exponentially increased over the past years with numerous successful applications on vertebrates. They have been shown to be a strong indicator of individual fitness and even promising proxy for early warnings of population extinction risks. Applications in marine invertebrates are sparse and MARBEFES aims to bring this potent tool into the realms of the marine environment, especially on sensitive species such as corals located in vulnerable marine ecosystems. Sub-lethal stress indicators capable of distinguishing intermediate stress status are essential for early intervention and thus preservation and sustainable management of vulnerable marine ecosystems forming species. 

Samples of deep-water corals were collected in northern and mid Norway. The collection has been carried out along a disturbance gradient, in the vicinity of aquaculture production facilities. Based on existing methods, we established a protocol to measure telomere length in Paragorgia arborea using the terminal restriction fragment (TRF) assay which is considered as the gold standard technique for telomere DNA length measurement. In a second step, we explored their application as relevant molecular tools to investigate sub-lethal stress in corals exposed to changes in environmental conditions.