Early Career Scientist: Tom Shlesinger

What is your primary research interest, and how does it link with the mesophotic zone?

My primary research interest lies in coral reproduction and dispersal. Additionally, I am interested in how these processes change along environmental gradients and eventually shape the coral-reef dynamics, biodiversity, and resilience. Quite a lot of coral species have a distribution that encompasses a relatively large depth gradient, starting from the shallowest point of the reef and extending well into the mesophotic depths. For many of those species, the upper mesophotic reefs constitute the very edge of their depth range. Along this depth gradient the environmental conditions vary tremendously and impose energetic limitations, physiological adaptations, and more. I believe that this natural system provides a fascinating opportunity to study the forces behind the processes in which I am interested, and to understand their broader ecological and evolutionary implications. Moreover, the 'Deep Reef Refuge Hypothesis' has become quite topical in recent years. However, very few studies to date have explicitly assessed the assumptions involving mesophotic corals’ reproductive performance and their actual ability to provide larvae to replenish shallow reefs. Much of my research involves studies of the reproductive performance and parental effects in corals that may influence the larval settlement preferences and success in different habitats.

Describe the location of your main (or most interesting) study site and how it fits in with your research questions.

My main study site is the Gulf of Eilat and Aqaba (GOE/A) in the northern Red Sea, shared between Israel, Egypt, Jordan, and Saudi Arabia. This works both ways. The Gulf presents a location that is particularly suitable for my research questions; while my research questions are a direct result of the characteristics (and research opportunities) of this area, and the unique nature of this sea. The GOE/A is one of those places where you can already enter the water straight from the beach and can quite fast and easily descend to 60-70 m depth. The Red Sea as a whole, and more specifically its northern part, is a highly interesting ecosystem with many biological, ecological, and oceanographic phenomena unique in the world.

The mesophotic depths may harbor flourishing reefs. This photo of a diverse coral reef was taken at 45 m depth in the Gulf of Eilat and Aqaba. (C) Tom Shlesinger

The mesophotic reef at 54 m depth in the Gulf of Eilat and Aqaba. Many mesophotic reefs host what seem to be thriving communities of corals, fish, and other animals. (C) Tom Shlesinger

What is your primary means of accessing mesophotic depths to conduct your research (e.g. ROV, SCUBA, rebreather, submersible) and what were the main challenges to overcome?

Currently, my research focuses on the upper mesophotic depths (down to ca. 60 m depth) so I am able to dive relatively easily for all the purposes of my research. I use both open-circuit SCUBA and closed-circuit rebreather with different gas mixtures. The main challenge to overcome was the fact that with mixed-gases I hardly feel nitrogen narcosis anymore…

What do you remember from your very first exposure to coral reef or mesophotic fieldwork?

I grew up along the shores of the Red Sea, so it feels like the coral reefs were always "around". From an early age I was fascinated by the remarkable diversity, shapes, colors, and patterns that this ecosystem possessed. My first dive to the mesophotic depths, to carry out a quick job, was in 2006, and I mostly remember admiring the reefs I'd seen down there. I noticed certain coral species there that are rarely encountered at shallower depths or are even completely absent. Many of the corals that I did recognize were slightly different in their morphology and coloration patterns to those at the shallower depths, and this fascinated me. I have to admit, though, that my admiration was probably also fueled by the fact that we did not use NITROX or TRIMIX back then and I especially enjoyed the nitrogen toxicity that occurs at greater depths… (Of course today I would definitely choose not to work that way)

The branching coral, Acropora squarrosa, spawns pinkish bundles of eggs and sperm. This is an endemic species to the Red Sea. (C) Tom Shlesinger

Studying reproductive traits in the lab using histological sections of coral tissues. (C) Tom Shlesinger

What new skill(s) have you learned during your research and what is one thing (skill, program, advice, etc.) that you wish you learned earlier in your science journey?

In one’s early steps that in the academic world (either MSc or PhD) there are many new things to learn: the relevant literature regarding your research topics, new lab procedures and techniques, building a proper experimental design, analyzing and exploring your data, writing scientific papers, and much more. Looking back, I would have strengthened myself as early as possible in data exploration and analysis. There is a rapid growth in the number of tools we can use, both in terms of the software to work with (e.g. R, MATLAB, Python), and in different types of analyses we can perform beyond the very basic statistics. As soon as you become aware of the many options for your field of work and how to implement them, you'll have a much better understanding of how to design your research, how to collect your data, and most importantly how to interpret your results. Moreover, learning new analytical tools and approaches may even open your mind to new interesting questions you can ask using basically the same dataset (and hopefully can answer as well).

How do you keep current with an endless stream of research coming out (or any favorite science website or blogs that you follow)?

That is a real challenge. I try to keep current by reading articles almost daily; sometimes the older classical papers and sometimes the newest ones. Conferences offer great opportunities to obtain the most recent science in a very condensed way. I also follow specific researchers and papers on ResearchGate and Google Scholar. Occasionally, I browse some of my preferred journals’ websites in order to become acquainted with research from other disciplines that may bear some relation to my own work or simply because it is interesting and inspiring.

Carrying out different kinds of ecological surveys from the reef flat and down to 60 m depth. (C) Tom Shlesinger

As the sun begins to set and the desert mountains surrounding the Gulf of Eilat and Aqaba glow in purple-red I start to prepare for my 'night shift': While snorkeling and free-diving, I document the timing and behavior of reproduction in corals and other inhabitants of the coral reef. (C) Derya Akkaynak