Mark Lenz1
1GEOMAR Helmholtz Centre for Ocean Research Kiel, Germany
About 20% of the world’s coastlines are affected by artificial light at night, while anthropogenic light emissions are expected to increase at a rate of 6 – 10% per year. Despite its abundance, a comprehensive understanding of the effects of light pollution on shallow water benthic ecosystems is still lacking. In the framework of the international research and student training programme GAME (Global Approach by Modular Experiments), the influence of artificial light at night on the diversity, structure and composition of early successional hard-bottom communities was investigated in standardized field experiments that were implemented simultaneously at nine study sites along a latitudinal gradient from 5° to 66° N between June and September 2023. In these experiments, the colonization of and the early succession on illuminated and non-illuminated artificial surfaces were surveyed over the course of 3 months. The applied night-time light intensities (30 lux) equalled those that can be encountered along artificially lit shorelines, while white and yellow LEDs were used as light sources. The applied light at night had a strong effect on community composition at many of the study sites, but these effects became weaker with increasing latitude, i.e. decreasing length of night-time light application. Furthermore, numerous effects on the diversity and the biomass of the assemblages were observed, while the size as well as the direction of these effects varied with the study system. The results indicate that artificial light at night can strongly influence the formation of hard-bottom communities and show that assemblages that establish under the influence of nocturnal light can be distinctly different from such that develop in non-illuminated environments. Hence, artificial light at night can be an important driver of change in marine benthic systems and it therefore should be considered in coastal management plans and conservation efforts.
Biography
Mark Lenz is a benthic ecologist and senior scientist at GEOMAR in Kiel, Germany. Since 2004, he is the scientific coordinator of the international research and student training programme GAME (Global Approach by Modular Experiments). The scientific focus of GAME is on the influence of anthropogenic pressures on benthic coastal ecosystems, while its methodological approach is the simultaneous implementation of standardized experiments at different study sites.