Many studies have shown links between increasing mean temperature and ecosystem change. As a consequence, predictions of biodiversity response to climate change have typically been developed using projected changes in mean temperature. However, ecological change is often driven by discrete, extreme climatic events rather than slow changes in mean conditions. While well studied in terrestrial ecosystems, the mechanism and influence of these extreme events, such as marine heatwaves, are poorly understood in marine systems. With ever increasing changes in climate, it is extremely timely and important to improve our understanding of the relationship between marine organisms and their rapidly changing environment.
In the austral summer of 2011, an unprecedented marine heatwave occurred across the west coast of Australia leading to widespread devastation of habitat forming seaweeds, widespread coral bleaching and massive fish and invertebrate kills. In particular, the Shark Bay World Heritage Site was subject to extremely high sea water temperatures. In my PhD, I am using our long-term behavioural and demographic data set to investigate to what degree this rapid environmental change led to behavioural modifications and changes in life history parameters in Shark Bay’s bottlenose dolphin population as well as modeling the long-term viability of the population in the face of ever accelerating environmental changes.
Demographic parameter information of dolphin populations are vital for species and habitat conservation. These data not only illuminate the immediate impact of extreme climatic events but also can be applied to long-term population viability analyses. In my first chapter, I am using multi-state mark recapture models to investigate how adult, juvenile and calf survival was impacted by the 2011 marine heatwave. In this chapter, I also examine the impact of this extreme climate event on the reproductive rate of these dolphins.
Following rapid environmental change, survival is dependent on adapting to novel conditions. Animals may adapt via strong selective regimes that lead to genomic changes or shift their range and distribution along the climate gradient. However, bottlenose dolphins in Shark Bay are highly philopatric and long lived with long generation times. Such adaptations are thus unlikely to keep up with rapid warming events but behavioural flexibility may provide adaptive potential. In my second chapter, I will investigate how activity budgets changed following the marine heatwave to determine the behavioural response to physiological and ecological variables and shed light on dolphins’ flexibility in response to rapid environmental change.
Given predicted increases in the severity and duration of marine heatwaves on both regional and global scales it is crucial to model the future viability of the Shark Bay dolphin population. Based on updated demographic and behavioural data as well as life history traits revealed throughout our long-term study in Shark Bay, my third chapter will focus on population viability analyses to assess the impact of climate change and the increasing frequency of marine heatwaves on the population dynamics of Shark Bay’s dolphin population.
