Coral Islands Rise With Sea Level
Worries about sea-level rise inundating coral atolls and islands are unfounded, thanks to coral’s rapid response to change.
A team of 5 geologists from Australia and New Zealand has good news: islands and coral atolls in the South Pacific are not at risk from sea level rise as much as earlier thought. Their paper in Geology, “Coral islands defy sea-level rise over the past century: Records from a central Pacific atoll,” shows from observations over a century that corals are able to respond rapidly to sea level fluctuations—on the order of decades or centuries, not millions of years.
The geological stability and existence of low-lying atoll nations is threatened by sea-level rise and climate change. Funafuti Atoll, in the tropical Pacific Ocean, has experienced some of the highest rates of sea-level rise (∼5.1 ± 0.7 mm/yr), totaling ∼0.30 ± 0.04 m over the past 60 yr. We analyzed six time slices of shoreline position over the past 118 yr at 29 islands of Funafuti Atoll to determine their physical response to recent sea-level rise. Despite the magnitude of this rise, no islands have been lost, the majority have enlarged, and there has been a 7.3% increase in net island area over the past century (A.D. 1897–2013). There is no evidence of heightened erosion over the past half-century as sea-level rise accelerated. Reef islands in Funafuti continually adjust their size, shape, and position in response to variations in boundary conditions, including storms, sediment supply, as well as sea level.
While this is good news for the islanders, it is bad news for alarmists:
Results suggest a more optimistic prognosis for the habitability of atoll nations and demonstrate the importance of resolving recent rates and styles of island change to inform adaptation strategies.
In other words, alarmists were misinformed.
Phosphorus for Us
All life, including coral, requires phosphorus, but the “Phosphorus Cycle” has been poorly understood. How does this essential element cycle through land and sea? The ocean’s “hidden fertilizer” was investigated by Woods Hole Oceanographic Institute. Science Daily reports,
Phosphorus is one of the most common substances on Earth. An essential nutrient for every living organism — humans require approximately 700 milligrams per day — we are rarely concerned about consuming enough of it because it is present in most of the foods we eat. Despite its ubiquity and living organisms’ utter dependence on it, we know surprisingly little about how it moves, or cycles, through the ocean environment.
Taking samples of plankton from a boat in the Bermuda area, they found three new things. First, the phosphorus cycle is “much more complex than previously thought.” Second, they uncovered a “previously hidden role that some microbial communities play in using and breaking down forms of this essential element.” And third, “these results show for the first time that microbes are producing phosphonates in the ocean, and that it is happening very quickly.” The element must be made available in a form life can utilize. Microbes metabolize phosphorus into phosphonate, forming the basis of the marine food web.
“Such work will help us further resolve the complexities of how this critical element is cycled in the ocean,” Dyhrman adds.
“A reason to be excited about the findings of this elegant study is in the paper’s last sentence: ‘the environmental, ecological, and evolutionary controls . . . remain completely unknown.’ There’s still a lot we don’t know about the sea,” says Don Rice, program director in the National Science Foundation’s Division of Ocean Sciences, which funded the research.
The phosphorus cycle joins the carbon cycle, water cycle, nitrogen cycle, ozone layer, and other global systems that keep our planet habitable. Environmental and ecological systems seem apparent, but whatever an “evolutionary control” might be is unclear.
In Science Magazine, Claudia Benitez-Nelson describes the chemistry of the phosphorus cycle in more detail, noting that phosphonate, a reduced form of phosphorus, is energetically expensive. “Why organisms produce energetically expensive, reduced phosphorus compounds remains a mystery, particularly given that these compounds are subsequently released to surrounding waters,” she says. “…. the environmental factors that contribute to the production and release of reduced phosphorus compounds in surface waters remain unknown. Perhaps this redox cycling is related to the evolution of cyanobacteria and archaea more than 3 billion years ago.” That would be because “At that time, phosphorus concentrations in the oceans were very low because high concentrations of ferrous oxides scavenged and removed phosphorus preferentially from the surface ocean.” She says the new study might provide a “missing link in ocean phosphorus cycling” indicating that everything is in balance today. In short, the researchers found “a large, rapidly recycled pool of reduced phosphorus compounds that play a key role in ocean phosphorus biogeochemistry.” The original paper by Van Mooy et al. is in the same issue of Science Magazine, which states, “Overall, our study suggests that the production of phosphonates and/or phosphite contributes to a globally vast phosphorus redox cycle that exceeds the magnitude of phosphate inputs to the ocean.”
There’s another piece of the puzzle: one of dozens of factors required for our privileged planet. It’s amazing that the phosphorus cycle involves chemistry, geology and biology working in concert to keep an essential nutrient in balance.
As for sea level rise, we’re not saying that the “optimistic prognosis” for atoll nations applies to all shorelines, nor using this information as justification to ignore the impacts of a changing climate. That’s not the point of quoting this paper. There are two lessons here. (1) Modelers who simplistically thought that atolls would be inundated by rising sea levels underestimated the response of coral to “variations in boundary conditions” of all kinds. The islands actually grew and prospered in spite of predicted catastrophes. (2) Without access to the full paper, we’re not sure if they referred to Darwin’s theory about coral atolls. However, the rapid response of the islands to changes in just one century calls into question the assumption that long ages are required for coral island formation. Creation geologists may wish to investigate this paper in detail.
Let’s also use this occasion on Memorial Day to honor the brave Americans who gave their lives in the South Pacific fighting nations that did not believe that we are endowed by our Creator with certain unalienable rights. We can never thank them enough for their service.