Thanks for this key question. The poster shows results from a three year time series. It is important to note that this “pristine” reef did not experience a statistically significant recovery rate in comparison to mortality rates.
While the decline in our coral, Porites superfusa, was significant from 2009 to 2010 (1-way ANOVA, F = 3.67, p = 0.041), the recovery is not significant (1-way ANOVA, F = 1.03, p = 0.411). However, this is part of why this research is important. It’s easy to significantly decrease coral cover. Recovery occurs at much longer time scales, which may be part of why it is understudied. We hope to see significant recovery soon. Our 2012 data set suggests additional recovery is occurring.

One of the reasons we conduct research in Palmyra is due to its remote location. It experiences minimal human impact. In this way we are hoping to somewhat isolate the effects of climate change. However, there is key parallel work being done on recruitment by other collaborators researching at Palmyra. They are specifically addressing your question by using an array of tools (including tiles) to get recruitment cycle information. I’m hoping their results will inform some of my research. Until then, I focus more on re-growth mechanisms. To minimize variability I have started with one species of coral, Porites superfusa, and am now beginning to look at an additional species, Acropora cytherea (this data is still being collected). Using our photographic “tagging” we are able to follow each colony’s mortality/ growth/ re-growth at a colony, species, and community scale. We hope to tease apart important environmental and biological factors. Great question! Thanks!

I’d like to second Kate’s points, and add a couple additional thoughts. Kate and I are both fully aware of the implications of disturbance in terms of intermediate diversity maxima, pulse-reset cycles, boom and bust population dynamics, etc. Stochastic or pulse events (e.g. recruitment, storms, etc.), however often occur rarely, unpredictably, and are relevant over longer time scales than a dissertation often can adequately address. That said, both of us are conducting experiments over longer time scales than many others (>2) years, with the intent of including some degree of naturally variability in our studies. To truly address appropriate scales and magnitudes of stochastic events, however, we would need decades-long studies such as those in Tahiti, the Great Barrier Reef, and the Caribbean.

Our work, therefore, focuses specifically on the biological processes related to recovery of coral reef communities after pulse disturbance events. For example, Kate is exploring recovery mechanisms of damaged corals specifically, and I am exploring community development and succession as a function of the environment.

With respect to anthropogenic versus natural influences, my work will not be able to identify a smoking gun; however, it will be able to provide information on the factors most strongly related to successional trajectories around Maui. Based on previous research, we know which factors are most likely being altered by human influence, and if these appear to be major drivers of reef development, my work may point us in the right direction with respect to the most important actions managers can take to minimize human impacts and maximize reef recovery potential (i.e., resilience).

Many thanks for you thoughtful questions and comments!

Very interesting question. Levi and I discussed this together, and I’m going to post our joint response. We would choose Maui. Palmyra is already remote and protected. We have to apply limited resources in a meaningful way; somewhat like emergency triage. My research on recovery will inform us regarding the relative importance of single site protection versus strategic networks. Reefs that rely on re-growth of surviving colonies need home reef management, whereas reefs that rely on recruitment may need a network of protected neighboring reefs. Levi’s research will inform us regarding areas that would benefit most from different forms of protection (e.g. no take, watershed, etc.). Thanks!

Fair enough. Thanks Kathryn.

Thanks, Dr. Anderson. Interesting mechanical strategies to stimulate coral regrowth might include reducing human-induced chronic disturbances like sedimentation (from coastal construction) or nutrient input (from sewage outfall). My research has sparked questions about how incidence of partial mortality and re-growth might be declining due to an increase of chronic disturbance. For example, sewage outfall stresses corals in ways that results in complete mortality. But an acute disturbance such as a hurricane, which corals have had centuries to adapt to, often result in partial mortality.

In my research on Porites superfusa, I found that being an encrusting coral is a critical ecological strategy for surviving a bleaching event. Bleaching occurs often as a result of temperature and UV. The encrusting corals that have polyps in crevices or underneath branching or massive corals may sometimes survive, despite the exposed parts of the colony suffering mortality.

This is based on my small case study and a literature review, but I hope to understand more about these mechanisms as my doctorate continues.

I’d like to support Kate’s comments fully and add a bit more about my own work.

Maui is highly impacted by both local and tourist populations. Nutrient pollution (sewage and fertilizers), sedimentation (development), and overfishing of herbivore populations have all been implicated as drivers of observed rapid declines in live coral cover around the island.

By using a comparative experimental design, combined with extensive environmental monitoring, our goal is to describe variation in community development and reef growth around the island and explore which environmental characteristics most strongly correspond with highest and lowest rates of reef growth. We hope that the results of this work will elucidate some of the key drivers of reef dynamics in Maui and, therefore, allow us to focus on the ecological strategies (e.g., marine protected areas, improved land use, waste water diversion, etc.) that will minimize negative human impacts and maximize the recovery potential of Maui’s coral reefs. We currently do not have the answers, but are expecting to gather the relevant information to address this question after the 2-yr experiment ends this fall.

Many thanks for your comments and questions!

Thank you both for responding to this question. The video sea scenes were so engaging and it is nice to see scientists share ways they value creativity!

I would like to echo Kate’s comments. I think the simple answer is yes, that these results can be extrapolated to large disturbances. For example, researchers on the Great Barrier Reef have documented one of the most rapid recoveries of live coral cover from a major disturbance ever documented, and this recovery was based almost entirely on regrowth of damaged, but surviving, coral fragments. Other systems (e.g, Moorea) have also recovered from major disturbances, but via coral recruitment, and at a much slower rate.

The ability of these reefs to recover were dependent on two different mechanisms (recruitment vs. regrowth), but were entirely dependent on one ecological principle: the ability of corals to outcompete and overgrow other benthic organisms and substrates. Our work specifically examines this ecological principle—the abilities of damaged coral fragments and new recruits to grow and compete for space. For example, it is quite possible that we will see strong competitive dominance and regrowth of coral fragments in a pristine environment such as Palmyra. In contrast, corals appear to be competitively inferior to other sessile organisms in Maui, possibly as a result of numerous anthropogenic stressors.
Admittedly, our work does not specifically address the relative importance of regrowth and coral recruitment to net reef growth over geographically or geologically relevant scales of space or time. However it does address the factors that might ultimately determine which recovery mechanisms are most important to the resilience of a given reef community; and therefore, may inform us regarding how different coral reef ecosystems might be most effectively managed.

Haha, thanks Stephanie! Your video was great. Loved the intro!

Why thank you ^.

Thanks!

Thanks! I’ll have to look him up.

Just search ‘Tyrone Hayes atrazine’ on youtube and you should find it. It’s great, but I’m equally impressed with Levi’s performance, which is why it immediately reminded me of it. Good luck

Thanks Ellen! Our science art is directed at a general audience. That said, our form of art is quite modern and pop-related, which we hope will bring some esoteric and seemingly inconsequential information to the forefront of the minds of younger generations. Our art is posted on Youtube, Facebook, our own personal blogs, other syndicated websites and our own Coral Reef Ecology website. (re-posted from Levi)

Hi Dr Drayton, thanks for your question. To clarify, I conducted a case study on Porites superfusa from a time series before and after a bleaching event. I documented the relative rate of decline after the bleaching event in 2009 and am currently documenting its recovery from 2010 to now. We are expanding this research to include several other species of coral on the atoll, and are working to incorporate population genetics as tool to investigate the question from additional angles.

Thanks!

Thanks! Go Tritons :) Liked your video as well – I think we met at a meeting about an Outside Magazine project, is that right?