Ms Amelia Caley1, Ms Maria Byrne2, Mr Ezequiel Marzinelli2, Ms Mariana Mayer-Pinto1
1University of New South Wales, Sydney, Australia, 2University of Sydney, Sydney, Australia
Artificial light at night (ALAN) is a growing threat to coastal habitats worldwide, such as kelp forests, likely compounding the existing threats of climate change and herbivory. However, few studies have investigated the interactive effects of light pollution and other threats, such as warming. Sea-urchins play a key role in controlling the abundance of kelp. In high abundances, overgrazing by sea urchins can create urchin barrens, which are large areas devoid of kelp. Changes to their feeding activity and behaviour can therefore have major impacts on kelp forests – a dominant habitat along temperate rocky reefs. Stressors can affect the kelps themselves, e.g. through changes in the kelp-associate microbiota, which can, in turn, influence the chemical defences of algae and their nutritional value, impacting interactions with sea-urchins. Using a manipulative experiment in flowthrough aquaria, we tested the independent and interactive effects of ALAN and ocean warming on consumption rates and behaviour of the urchin Centrostephanus rodgersii over time. We also measured effects on the kelps (Ecklonia radiata) themselves, including changes in microbial communities and photosynthetic yield. Individual urchins were placed in tanks haphazardly assigned to each of 4 treatments: +/- ALAN and +/- Warming (+2°C) (n=14). Measurements of consumption, behaviour and kelp quality were taken in weeks 1, 2, 5 and 7. Preliminary results show herbivory was higher in warm treatments compared to ambient treatments, and after 5 weeks, herbivory in warm ALAN treatments was higher than other treatments. These findings are critical to ensure effective management of temperate reefs as ocean warming and ALAN are predicted to continue to increase on our coastline.
Presentation Slides – Amelia Caley
