We live in a time of ever-increasing human pressure on the marine environment. In the coming century, life in the ocean will be confronted with an unprecedented rate of species extinction and many organisms and communities may change or disappear even before being described and understood by science. This is the main driver of my primary research interests, which are directed toward understanding the functioning of marine organisms and communities and their underlying ecological interactions. My interest in this topic dates back to my undergraduate years and drove my decision to enroll at the University course in Management and Conservation of the Marine Environment in Genova.
During my Bachelor and my Master, I investigated different facets of the effects of human activities on marine organisms.
In my Bachelor studies, I explored the recruitment patterns of hard coral communities recovering from a temperature-induced bleaching event in the Maldives. In this study, which was afterward published in the Journal of the Marine Biological Association UK (Cardini et al. 2012), I found oceanic reefs to be a more suitable environment for the settlement of small corals than lagoonal reefs. Conversely, corals in larger size classes were scarce on oceanic reefs, where predation and wave disturbance can be responsible for high juvenile mortality and/or limited growth.
In my Master, I looked into the detrimental effects of ocean acidification on calcification and growth of the Mediterranean habitat-forming red coral (Corallium rubrum). This work was subsequently published in Scientific Reports (Cerrano et al. 2013). In this physiological study we provided evidence of significant reductions in calcification and polyps’ activity of this species exposed to increases in pCO2 as predicted for the end of the century.
These experiences, among others, reinforced my interest in marine biology and ecology, to which I intend to contribute as a researcher.
During my PhD, I focused on microbial dinitrogen (N2) fixation (diazotrophy) in a coral reef exposed to high seasonality in the northern Red Sea.
Key results of my PhD work (Cardini 2015, PhD thesis) indicate that: (a) benthic community changes and/or structural habitat loss will result in changes of inputs of fixed nitrogen to the reef ecosystem, (b) global stressors such as ocean warming and acidification have a high potential to influence symbiotic N2 fixation in scleractinian corals, and (c) high coral-cover areas of the reef are not only important for their primary productivity but also for their associated N2 fixation, with areal rates competing with those of flat sandy areas. In the face of climate change, these results are important as they show that modifications in biogeochemical nitrogen cycling on reefs may derive both from direct changes in diazotrophic communities’ structure and function, and from altered availability of benthic substrates favorable to these microorganisms.
Despite these intriguing results, many challenges remain in the field of exploring diazotrophy in benthic habitats. A multidisciplinary approach combining different methods from biogeochemistry, microbiology, molecular ecology, and physiology is needed to understand the functioning of such interesting microbial communities. In particular, I believe that the use of molecular methods will be the key to disentangle the different factors that affect their distribution and activity.
Moving from my bachelor to my PhD studies, I have become fascinated by the topic of microbial symbioses. This is a very dynamic field of research benefiting from a recent flourishing of molecular techniques that are essential to study microbial communities. Thanks to these methods, we have come to appreciate the astonishing diversity of animal-microbial interactions, and this growing knowledge is currently revolutionizing the basic principles of animal biology. As many (if not all) animals appear to largely depend on beneficial microbial partners that promote their health, it is paramount to understand the functioning of such biological systems if we are to conserve fundamental ecological and biological functions of marine organisms and ecosystems. During my PhD, I focused on an example of animal-microbial interaction between tropical corals and diazotrophic bacteria. Unique to the coral system is that photosynthetic eukaryotic algae (zooxanthellae), bacteria (N2 fixers) and the animal host (coral) cooperate, facilitating the nutritional success of the entire group of partners (Cardini et al. 2015).
The interest in microbial symbioses drove me to Vienna, where I am now part of a project investigating the diversity and function of chemosynthetic bacteria in marine clams. Our research relies on state-of-the-art techniques to understand the role of fine-scale diversity in the functioning and evolutionary stability of host-microbe associations.