By Jamison Gove |
| Grey Reef Sharks often congregate in the tens to hundreds at Jarvis Island |
There is an intimate and inseparable link that exists between oceanography and coral reef ecosystems. Ocean waves, currents, temperature, salinity, and nutrient availability are each important and play a significant role in determining not only the diversity and abundance of organisms an a coral reef, but can also dictate the morphology (shape) of coral and algae species and the substrate they inhabit. For example, corals which are consistently battered by ocean waves tend to be low-lying and mound-shaped, lacking the large, delicate and branching structures that are often found in more benign, wave-free environments.
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A few Raccoon Butterfly fish
make their way down the reef |
In some places around the world, this connection between coral reef ecosystem dynamics and the surrounding environment can be subtle; however, at Jarvis Island this elemental relationship is so abundantly clear you would have to be sound asleep to miss it. In other words, you can actually see oceanography in action.
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Schools of small fish are common
at Jarvis Island |
Due to its location in the central equatorial Pacific, Jarvis is impacted by a strong, cold, nutrient-rich ocean current flowing below the surface, centered at approximately 150 meters depth. This current, known as the Equatorial Undercurrent, is spawned in the far western Pacific and flows eastward along the equator and across the entire Pacific Ocean. When this fast-moving current interacts with Jarvis Island, it forces deep water to the near-surface, providing copious amounts of nutrients to the surrounding coral, algal, and fish communities. These nutrients are quickly assimilated by the reef community, fueling an astonishingly productive and ecologically vibrant coral reef system. Few places on the planet have the oceanographic and coral reef environment that is found at Jarvis, making it a unique and special place not only for scientific research, but also for protection for many generations to come.
You mention that "few places on the planet have the oceanographic and coral reef environment that is found at Jarvis"-- could you tell me what other places in the Pacific have both the oceanographic features and the high-productivity coral reef that Jarvis does? I guess what I'm wondering is how Jarvis compares to other sites where the same naturally occurring "experiment" takes place. I guess something similar happens around the Galapagos and that is a result of the Cromwell Current, as well, but how does the situation there compare to the oceanographic conditions at Jarvis? (Which is kind of a giant question, sorry-- a general answer would be awesome, or maybe just take that one as a hypothetical.) But specific to Jarvis, I wonder: does the size of the island result in differences between one side and the other; does the upwelling affect all sides equally? Also, could you briefly describe what kind of seasonal variation you see, or variation in El Nino years, and whether you've yet observed organism behavioral adaptations in relation to any variation? Thanks to everyone for all the great posts, and for answering my questions, if you have time. No rush at all, promise.
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