Thank you for watching! Although climate change and a warmer ocean are complicated problems requiring complex solutions, Graham said that this study showed that a simple measure like getting rid of rats on the islands was something that conservatives could do right now. This is a huge incentive to destroy the oceanic coral reef islands, "he said. "It's a fruit at hand."
Graham and his colleagues set out to see if they could find evidence of links between what was happening in the island and health coral reefs nearby. Suspecting that the nutrients that birds deposited in their guano could also infiltrate into the ocean, the team chose a group of 12 islands in the Chagos Archipelago of the United States. Indian Ocean, six of which have rats and six which do not.
between the islands with rats and those who were without, it was like "chalk and cheese," Graham said. On average, they found that the rat-free islands had 760 times more seabirds than the rat-infested islands.
Soil samples and hardwoods from the islands showed that nitrogen levels were 251 times higher. Islands free from rats. The team also probed their samples for a specific form, or isotope, nitrogen. Seabirds such as boobies, noddies, and shearwaters connect the islands to the open ocean, in some cases traveling hundreds of miles to feed on fish there, Graham said.
On these trips, birds take a characteristic isotope of nitrogen with the fish they eat. The researchers traced the trajectory of nitrogen to the islands, finding the isotope in soils and plants, as well as in algae, sponges and fish living on the reef.
"Seabirds link three different ecosystems".
The researchers then compared the size and rate of growth of damsels living off the coast by examining the ear bones, or otoliths, of these fish. Otoliths develop in concentric rings, similar to the rings of a tree. This model allows scientists to determine the age and speed of fish growth.
Graham and his colleagues found that damsels grew faster and were older for their age when they lived on reefs adjacent to ratless islands and many seabirds. In fact, the biomass of the entire fish community was almost 50% larger around rat-free islands.
"It's the first time this nutrient subsidy" – in the form of nitrogen from seabird droppings – ""
Herbivorous fish, in particular, is are well behaved in the productive environment found off the densely populated islands.They serve the reef by grazing to keep algae under control and breaking pieces of dead coral in a process known as name of bioerosion, which allows the reef to develop.The rates of these "critical ecosystem functions" were more than three times higher on the reefs near the large colonies of seabirds. 19659005] This study tells a "really complete story," says Anne Lorrain, marine ecologist at the Institute for Research Development in Marseille, France, who was not involved in the research. goes further [than] other studies available available with a large number of organisms studied and [in] evaluating functional aspects ", such as fish biomass and bioerosion.
In 2017, Lorrain published a study on coral reefs in the Pacific Ocean in the journal Scientific Reports . She and her colleagues discovered that the guano nitrogen of birds was found in nearby corals, also using a specific isotope. "I think we need more research on the effect of seabird guano on the physiology of marine organisms and on different ecosystems," she said
. Current study, the intake of nutrients from guano of seabirds makes for a healthier and more robust ecosystem. But this is not always the case. Floods of human sewage and fertilizer runoff can overwhelm a reef with the growth of algae that wastewater encourages. Graham said that nitrogen from seabirds on the rat-free islands in the study was balanced by the phosphorus that it contained. In addition, the presence of this element could even give reefs a chance to fight climate change.
Ecologist Don Croll of the University of California-Santa Cruz emphasized the importance of algae-eating fish in the ecosystem. If they had been overexploited, for example, more algae could decrease coral growth, said Croll, who was not part of this study.
"On the other hand, if you have an intact fish community, you put more biomass. Mr. Graham said that the study islands were" completely untapped. "
1994, Croll co-founded an organization called .The conservation of the islands that now makes the restoration of insular habitat around the world.He said that this study demonstrated that getting rid of rats introduced by l 39; man was "an exciting conservation opportunity."
"The good news of eradicating rats is that, unlike climate change and fishing, it's a simple problem. he said. "We have the tools, we can do it."
But even with this "simple" problem, it would take "decades, not years" to see the results, Croll says.
He cited the example of Clipperton Island, a French territory in the Pacific. During a visit to the island in 1958, an ornithologist named Ken Stager discovered that he had been caught by wild pigs who, like rats, had attacked bird eggs. and reduces the Clipperton seabird population to approximately 1,000 individuals. good biologist in the 50s, he had a gun with him, "said Croll, so he killed all 58 pigs on the island.
The transformation was striking, if not immediate. In a decade, the number of seabirds was several thousand.And in 2003, scientists reported the presence of 25,000 brown boobies and 112,000 masked boobies living on the island. [19659005Theresultsoftheirinvestigationdemonstratethatgiventheweatherthebirdcolonies-andthenutrient-richguanotheybring"InthecaseofClippertonIsland"hesaystook50years"saysCroll"butit'snowthesecondlargestbrowncolonyintheworldandthelargestcolonyofmaskedmosquitoesintheworld"[19659007] This story appeared at Origin on the website of the World Conservation News Service Mongabay.com. Get updates on their stories delivered to your inbox, or follow @Mongabay on Facebook, Instagram, or Twitter.
