A preliminary investigation into the impacts of artificial lighting on selected fish and benthic species in Maltese waters

Abstract

The increasing recognition of Artificial Light at Night (ALAN) as a potential concern for biodiversity is grounded in a growing body of research highlighting its impact on animal behaviour, migration, reproduction, and biological interactions. In the Maltese Islands, there has been a noticeable rise in the prevalence of ALAN over the years. Despite this trend, the quantification and exploration of the consequences of artificial light on marine biota in the Maltese Islands remain understudied. This research aims to address this gap by investigating the effects of ALAN on multitrophic marine communities. Utilising a Baited Remote Underwater Video (BRUV) equipped with artificial lighting, the study focuses on two distinct local sites within the Ċirkewwa harbour that are characterised by comparable communities and depth, but different lighting conditions. The experimental design involved the replication of the study in both space and time, capturing the response of the communities to a pulse disturbance, represented by introduced light from the BRUV. This response was examined both with and without the additional stress induced by an ongoing press disturbance, represented by the already-present ambient light. The study establishes a direct link between artificial light and the local abundance of both predatory and prey fish in areas influenced by varying light conditions. The main findings from the study were that the plausible occurrence of habituation, especially in response to the press light disturbance. Predatory species, as exemplified by Trachurus trachurus, demonstrated a strategic utilisation of light conditions, particularly in high-light intensity situations. These predatory fish exhibited 'station holding' behaviour, actively maintaining their position within the illuminated area—an energy-intensive choice that is favoured in environments where a clear net energy gain is apparent. In contrast, species at a lower trophic level, such as Apogon imberbis, experienced a decline as light intensity increased. Additionally, species like Sepia officinalis and Hermodice carunculata exhibited a distinct preference for darker environments. These findings collectively underscore the complex responses of marine communities to varying light conditions.