Global Climate Change & Coral Recruitment: The Interactive Effects of Temperature And Ontogeny on the Biology of Porites Astreoides Larvae.
Principal Investigator: Peter Edmunds, California State University - Northridge

Over the next century it is predicted that the effects of global climate change will intensify, and the destructive effects on Earth's ecology will become more severe. Coral reefs provide one example of an ecosystem that is severely threatened by global climate change and rising seawater temperatures that will result. Importantly, corals live close to their upper thermal limit and many coral reefs have already suffered substantially from the effects of human-caused destruction. In the next ten years, degraded reefs such as many in the Florida Keys, may suffer catastrophic losses from the combined effects of global warming and other stresses, from which they will be unable to recover. Despite research efforts and substantial public recognition that coral reefs are in crisis, surprisingly little attention has been paid to coral reproduction and the resulting coral larvae that are critical to reef maintenance and ultimately recovery. The goal of this project is conduct a multidisciplinary analysis of the biology, physiology, and genetics of coral larvae to understand how global warming will affect the coral population structure of reefs in the Florida Keys.

The first year of the project will use Aquarius to collect larvae from Porites astreoides (commonly and locally referred to as mustard hill coral due to its shape and color) and to carry out experiments to examine three questions:

1. Do adult and larval corals display physiological differences that might make the larvae more (or less) sensitive to changing temperatures? This is an important question as adult corals are stuck on the sea floor, and it is onlt their babies -- the larvae -- that can drift through the water and find new (possibly better) places to live. Thus, it is important to know whether the larvae have a similar, or better, resistance to high temperatures than their parents, as the larvae likely will have to survive a wider range of conditions.

2. Does larval age and history affect their response to environmental challenges? Our earlier work in 1999 made the surprising discovery that the larvae grow fast. More specifically, it seems that their physiology and behavior changes over periods of days, which might affect how they respond to different kinds of stress. For example, a hot day immediately after they are released may be more damaging than a hot day several days later. This portion of our research will help to understand how weather conditions during a period of coral reproduction might affect how many corals settle and grow on the reef.

3. Do the larvae and adults contain the same types of symbiotic algae? This is a very exciting question, and one that has become important since it was discovered that corals contain many different "types" or "strains" of symbiotic algae. Even scientists are not clear what "types" or "strains" refers to, but we are sure that the different types are at least as different as species are in other systems. Because the algae are different, there is the possibility that the larvae may contain algae that are different than those found in the parent. This could have a strong effect on how well the larvae survive after they are released from their parents and enter the water column. To answer this question, we will be collecting samples for the analysis of algal DNA that will help us to identify the different types found in adults and the larvae they release.

Aquairus is important becuase saturation diving techniques will be used to collect larvae from numerous colonies during both the day and night. This will help ensure that we know the exact age (since release) of the larvae. Substantial amounts of bottom time and careful sampling are needed to conduct these studies. Questions 1 and 2 above will be addressed underwater using innovative physiological techniques (PAM fluorometry) and manipulative experiments. Our surface support team will concurrently harvest larvae for shore-based experiments using techniques that can't be conducted inside Aquarius that require chemical reagents and precisely controlled environmental conditions.