Abigail Shaughnessy was awarded the 2023 Gough Family Doctoral Fellowship. Here she shares some preliminary results from her field research conducted at LIRS, where she has been investigating how molecular plasticity of the visual systems function in coral reef fish. Outcomes of this project will expand our understanding of the visual capabilities of coral reef fish and the specific strategies they have evolved to survive. Investigating short-term plasticity in reef fishes will provide insight into their adaptive scope and whether they may be able to mitigate the impacts of increasing environmental change. This knowledge can then inform management strategies, for example, reef restoration efforts may profit from taking the sensory ecology of its inhabitants into consideration.

Fish living on coral reefs experience frequent changes to their light environment as the conditions can change naturally over different seasons, depth, or due to human influences such as sediment run-off. The amount of sediment or phytoplankton in the water column can affect the amount and the wavelengths of light available; simply put, how bright it is and what colours can be seen.

Consequently, as the light environment shifts, the visual capabilities of the coral reef fish may adjust to maintain performance. In a habitat where vision serves as a primary source of information, the capacity for a species to rapidly alter its visual system, termed phenotypic plasticity, could be an important factor in making reef fish more resilient. However, the scope of plasticity and how widespread plastic visual systems amongst reef fishes are remains unclear. With the support of the Gough Family Doctoral Fellowship, my project investigated the visual plasticity of coral reef fishes when exposed to natural and human-induced changes in their light environment.

The eye of a Blue-Green Damselfish (Chromis viridis) during an electrophysiology experiment to understand how the colour vision of coral reef fish adapts to seasonal changes in the light environment. Photo: Abigail Shaughnessy.

The first part of my project was to understand how visual plasticity may assist reef fish communities in adapting to natural, seasonal changes in their visual environment. The light environment on the Lizard Island reefs shifts from a broad-spectrum clear body of water during winter to a more green, algal-dominated habitat in summer. At the same time, the water temperature changes drastically between seasons, which might also influence vision in fish as it can modify how quickly visual responses work. We previously found the expression of visual genes, so-called opsins, in the eyes of some damselfish species (Pomacentridae), but not all seem to track these changes. To build upon these findings, I further investigated the plasticity of reef fish on the molecular and physiological levels. I elucidated the seasonal drivers (i.e., light environment and temperature) behind the presumable changes in opsin gene expression.

Understanding the limitations of colour vision plasticity is important in the context of anthropogenic influences on the marine environment. The increasing frequency and severity of elevated turbidity and algal blooms are recognized as a major threat to the Great Barrier Reef Marine Park. Algal blooms shift the light spectrum towards medium (green/yellow) wavelengths, and shorter wavelengths, particularly ultraviolet light (UV), are preferentially reduced. However, UV sensitivity is important for many coral reef fishes to locate and feed on zooplankton.

Preliminary results show that a damselfish, the False Percula Clownfish Amphiprion ocellaris, reduces the expression of their opsins responsible for UV sensitivity when placed under artificial light environments mimicking algal blooms. Therefore, the second part of the project was to examine how changes in gene expression levels affect foraging success in response to different anthropogenically impacted environments.

Thus far, preliminary analysis has shown opsin gene expression has a functional role in adapting colour vision under different light environments. Visual plasticity could allow damselfish to match their visual sensitivity to seasonal changes and maintain their foraging success under short-term disturbances. This indicates that colour vision plasticity is an important mechanism for coral reef fish to adjust their visual capability to meet the changing sensory requirements.

Blue Scribbled Damselfish (Pomacentrus nagasakiensis) found on the reefs of Lizard Island. This species relies on its ultraviolet sensitivity to locate and feed on zooplankton. The foraging success under different light environments was tested with this species. Photo: Abigail Shaughnessy.

The Lizard Island Research Station has been a fundamental part of the fieldwork component of my PhD. I am grateful for the opportunity of the Gough Family Doctoral Fellowship, as it has supported the development of skills to independently lead my projects, co-supervise students, and answer exciting questions in my field of research. The research station’s strong collaborative environment allowed me to strengthen my research network and foster new relationships that will continue to be valuable to my future career in coral reef research.

By Abigail Shaugnessy, PhD student, University of Queensland; 2023 Gough Family Doctoral Fellow