Some like it hot and lit: the compound effect of light pollution and warming on key costal species

Abstract:

It is now manifest that multiple stressors of human origin are affecting most marine environments. The global oceans account for ~90% of the total warming of the Earth system that has occurred since 1955 and this constant warming had severe impacts on marine life, from single marine organisms to complex ecosystems. The Mediterranean Sea is no exception and is warming at a faster pace with respect to adjacent oceans. Emerging evidence shows, however, that other anthropogenic factors are at play in such processes. Artificial light pollution (ALAN, artificial light at night) is one of the most recently recognized global sources of impacts for a variety of biomes, but it has been rarely considered in studies on the effect of multiple stressors in coastal marine habitats. Building upon these data, the aim of the present proposal is to understand the compound biological effects of the ongoing warming of sea temperatures and of artificial light pollution on key Mediterranean marine organisms, to ultimately determine the composite impacts of such anthropogenic factors on Mediterranean Sea communities. We will select three phylogenetically distinct species, that differ in their phenotypic plasticity and daily behavioural patterns: the marbled rock crab, Pachygrapsus marmoratus, the common sea urchin, Paracentrotus lividus , and the shallow subtidal Mediterranean killifish Aphanius fasciatus, . We hypothesise that the effect of ALAN will be greatest under increasing temperature, which already represents a strong stressor for natural populations, and that this interaction will be stronger in species less tolerant to variations in temperature. To reach our ambitious goals, we streamlined the project’s activities into three research work packages (WPs) focusing on the combined impact of ALAN and increasing temperatures on the target species in terms of: spatial distribution (Ecology), basal and swimming metabolism and the microbiota associated with their digestive system (Physiology), light and feeding entrainment of daily activity, social and defence behaviour (Behaviour). We will take advantage of state-of-the-art techniques and instruments, from high through-put respirometry and transcriptomics, to automatic tracking systems and an innovative multispectral and multidirectional device for in situ measures of artificial light pollution. The responses of animals from two Mediterranean basins differing in terms of current ranges in water temperature and future warming (the Ligurian and Northern Tyrrhenian and the Northern Adriatic Sea) will be compared. The results of our ecological, physiological and behavioural tests will be of critical importance to forecast the abundance and fitness of marine organisms thriving in this diverse but endangered sea, and, ultimately, to predict the functioning of coastal Mediterranean ecosystems.