Coral reefs are one of the most unique and diverse landscapes on the planet! Although covering only ~0.3% of the world’s oceans, these biological habitats house over 25% of the species of marine fishes on the planet. Annually, reefs provide protein that supports roughly 10% of the world’s population and generate goods and services valued at as much as $375 billion per year. Despite their importance, coral reefs are in peril. Human impacts such as overfishing, nutrient pollution and climate change have caused the loss of over 25% of the planet’s reefs in the last two decades. In the Florida Keys where Aquarius is based, over 90% of coral cover has been lost! With such alarming declines, scientists fear that these fragile habitats may be the first ecosystem in recorded history driven to extinction by human activities.
Overfishing is frequently regarded as one of the greatest threats to the health of coral reefs. Healthy stocks of algae eating fishes crop algae on reefs and recycle nutrients to keep reefs in coral dominated states. You can think of these algae eating fishes as farmers tending their coral garden! While it is becoming increasingly well known that overfishing of herbivorous fishes can instigate shifts from coral- to algae-dominated reefs, we currently still do not understand the role large predatory fishes play in maintaining healthy coral reefs.
Worldwide, large predators such as grouper are often heavily targeted by fisherman for both food and sport (I'm looking at you bass and muskie fisherman, though these particular fish are sustainable fisheries of course!). In many environments, the loss of such large predators can trigger drastic changes in the environment. Predators not only impact the environment through the consumption of prey species, but can have indirect effects that far exceed the body count of the prey consumed. For example, the reintroduction of wolves into Yellowstone National Park has initiated an environmental recovery that goes far beyond the wolves and elk that they eat. Rather than direct mortality, the fear of being eaten has driven elk to change the areas where they forage, allowing for the recovery of the parks previously declining aspen trees. It's the equivalent of someone dropping a ravenous lion into your cafeteria... how do you think you would react? From grazing herds and lions in the savannahs of Africa to snails and crabs along the shores of the Northern Atlantic these “landscapes of fear” that predators can create have been shown to regulate the feeding grounds of a myriad of animals across the planet. However, the effects of large predators on coral reefs are as of yet unknown.
To investigate how predators shape the behavior of reef fishes, the first portion of our research will utilize model predators and cutting edge hydro-acoustic technology (Pic above: Here we see our imaging sonars aimed at a grouper in the distance. Poor water clarity illustrates why using sound can be so much more effective). We will be placing highly desirable food sources across the reef in the presence and absence of model Black Grouper, an important but depleted game fish. To monitor changes in the behavior and feeding patterns of resident herbivores, high resolution imaging sonars will continuously record fish behavior in the area. This data, coupled with detailed observations about food consumption, will allow us to understand how herbivorous fishes balance foraging decisions with the risk of predation and better understand the role of predators on reefs.
Additional efforts will investigate these nutrient-induced changes in important reef forming corals. From the Medina Aquarius Base, we will simulate nitrogen enrichment on a select group of study corals, which were just delivered yesterday. These corals will be monitored with finely-tuned fluorescence meters and microsensor arrays to conduct round the clock assessments of the impact of nitrogen pollution on the health, physiology, and photobiology of these critically endangered coral species.
The best part about all of this is that the equivalent amount of data could take between 8 months to a year to collect from the surface. We're doing it in just a little over two weeks from the Aquarius!! Anyway, I hope this helps you understand what we're trying to do here, and if you have any questions, please do ask, it's what we're here for!
- Bree and Andy