字幕列表 影片播放 列印英文字幕 Born of fire, the Galapagos archipelago evokes visions of an ecological Eden. They are volcanic, isolated islands, so they are unique. This primordial world is home to some of the strangest creatures on earth -- from sea-going lizards to tortoises the size of rum barrels. This is a special place where so many strange animals are living together. Penguins, mantas, sea lions, sea iguanas. Altogether in one place. And this strange ecosystem has very interesting behaviors. The islands are engulfed in cold and warm ocean currents, resulting in this unique diversity of species. You get cold water organisms and warm water organisms all mixed. Corals are among the warm water species living in the islands- and what is happening to them may be a harbinger of things to come. We know now that the ocean chemistry is changing dramatically and that's because of the industrial age and all of the carbon dioxide that has been put into the atmosphere. Corals are forecast to be impacted severely by these changes in ocean chemistry. The isolation of these islands makes them a perfect laboratory for studying climate change. The Galapagos Islands acts as a natural laboratory because it's naturally exposed to high c02 conditions that provide essentially a window into the future of what we can expect throughout the rest of the world's oceans, with the doubling and tripling of atmospheric c02. The other added benefit is that it has experienced two very strong El Nino events in the last three decades. During El Niño warm seawater temperatures cause coral bleaching. And coral bleaching is one of the primary concerns of what coral reefs face with climate change. So by going into the Galapagos and studying how these reefs respond to warmer temperatures under these naturally low pH conditions, we can gain a window into the future. What is in store for coral reefs? Can corals survive in more acidic oceans and cope with increased water temperatures? Major funding for this program was provided by The Batchelor Foundation, encouraging people to preserve and protect America's underwater resources. And by Divers Direct Emocean Club, inspiring the pursuit of tropical adventures and scuba diving. Early Spanish explorers called them "Las Encantadas" --"the Enchanted Islands." The Galapagos are located in the eastern Pacific, about 600 miles off the coast of Ecuador. In 1835, Charles Darwin visited the archipelago, calling it a "little world within itself." The strange creatures he encountered would later shape his thoughts on the origins of life, and help him form his theory of evolution. The Galapagos Islands is a really fascinating location. Because even Charles Darwin when he visited noted how coral reefs were conspicuously absent from this location. Because the Galapagos sits right on the equator. It's within the tropical belt. What really differentiates it from the rest of the tropics is that you have this strong upwelling creating very different conditions than what you find normally in the tropics. Upwelling is a physical process whereby deep waters are brought to the surface. This deep water is rich in c02 and rich in nutrients. And when it comes to the surface, it creates these low pH locations in the ocean. This upwelling, as well as the confluence of several currents, results in the unique life forms living in the Galapagos. For half the year, The Humboldt, or Peru current, brings cold, nutrient rich waters up from Antarctica. From the west, the Cromwell current also brings cold water. Around January, the trade winds shift and the Humboldt current slackens. Now the Panama current dominates. The Panama Current flows south from the Panama and Colombia area, and the Panama current brings tropical organisms into the Galapagos. What Darwin couldn't see is that corals are among these tropical organisms. Now a team of around 20 scientists have arrived onboard the M/Y Golden Shadow to study the health of these reefs. Supported by the Khaled bin Sultan Living Oceans Foundation, they will spend a month in the Galapagos as part of the five-year Global Reef Expedition. One of the biggest barriers to oceanographers and ecologists to study remote areas of the oceans is just getting access to it. And the Golden Shadow and the Living Oceans Foundation is very unique in that regard that we provide scientists from around the world the access they need. The foundation was established by Prince Khaled bin Sultan of Saudi Arabia, to conserve coral reefs around the world. He knew that reefs are in trouble, and what he wanted was to set up a foundation that would go out and answer some of the pressing questions about why coral reefs are dying and what we can do to stop it. So he came up with this idea "Science without Borders"-it's basically because there are no political boundaries between the oceans. It's all connected. And what you do in one location, can affect another location. We go around the world to survey these reefs. We're applying a standard protocol that was developed through a consortium of scientists and we're applying that same survey protocol every place we go. We've developed this model of cooperation where we invite researchers from around the world to come on the ship and join us. And we're able to select researchers that have specific knowledge about each region that we go to. One of the people joining them on this trip is longtime Galapagos National Park naturalist and dive guide Mathias Espinosa. The Galapagos are relatively new volcanic islands, formed less than five million years ago. And their history is written into the rocks. Okay Philip, this is very interesting because this island is an uplifted island that means that lava flowed to a place underwater, and with the pressure of the plates that piece came out of the water. And you see some layers here, of white coral that shows you there was a lava flow underwater and a long time of nothing but white coral could grow on the lava flow. And then another lava flow over it. So it's very interesting to see that there were times of lava flows then nothing, then another lava flow. And so obviously these corals have existed in the Galapagos for thousands and thousands of years for that layering effect to have happened. Yeah, definitely. I mean we're not rich in corals, but it shows that we had the constant arrival of corals and growing up to a certain point. I guess for thousands of years. One of the comments you hear all the time is well, coral reefs have always undergone disturbance and change. And that's absolutely true. The thing we're really concerned about is the frequency, the severity and the duration of the changes all seem to be ramping up at scales that coral reefs have never experienced. Now, scientists want to understand what the thresholds may be for corals to survive into the future. Maybe you can try to anchor with a cut around here. The strong currents near the islands can be dangerous to divers, so they consult with local expert Mathias before their research dives. Whatever the current is, don't let your people get into deeper water. One way the experts study the corals is by measuring the currents that occur nearby. So this right here is our current meter. And what we are going to do, we set it up and then we are going to deploy it. The scientists want to correlate the strength of the currents to the types of coral communities they find in an area, to better understand why certain corals live where they do. Coral reefs that exist in the Galapagos really pale in comparison to what you find in other parts of the world that have very high pH. There's a limited subset of species that occur there, and they're very sparse in terms of spatial distribution. There's very few coral reefs in the Galapagos islands. These corals weren't discovered until the early 1970s. Dr. Peter Glynn was among the first to explore and study the reefs of the islands. They were totally healthy. Very vibrant coral communities. All of the corals looked in excellent condition. And so we thought that there would never be a problem there - that coral reef development would continue into the future. But every so often the natural balance between cold and warm ocean currents in this region goes awry. During El Nino years, trade winds reverse direction, the cold life-giving waters of the Humboldt and Cromwell currents dwindle, and warm waters devoid of nutrients flow in from the western Pacific and surround the islands. And what happens is the surface waters warm considerably. And corals live very near their upper thermal limits. And they're so sensitive that a deviation in sea surface temperature of only one degree Celsius above the normal conditions for a month or more, will elicit coral bleaching. A coral lives in a symbiotic relationship with algae that live inside its tissues. And the algae photosynthesize and provide fixed carbon to the coral host. And in turn the coral provides nutrients, a home that is free from predation. However the symbiosis is very restricted into a very narrow thermal range. When temperatures warm the corals will expel their symbiotic algae that live within their tissues. And this is called coral bleaching. So the coral can live for a period without its symbiotic algae, but it can't live for too long. So if the stress remains for a couple months or more, corals will start dying. I think the El Nino phenomenon has occurred for several thousands of years, and there was just no one around to observe the early events. But in 1982-83, we had a very severe El Nino event. In the Galapagos, the coral mortality at our study sites ranged anywhere from 95-97%. Very high. In 1997-98, there was another very strong El Nino event. And some of the corals that weren't affected in 82-83, suffered mortality. So we had two very strong events occurring just in one century. So this was very unusual, and it had a tremendous impact on corals in the eastern pacific. On this research expedition, scientists are going back to past study sites to see if the corals have recovered. In the North, one species survived the second bleaching event better than the first. It seemed to have adapted to the warmer temperature, which is a hopeful discovery for the team. We found very substantial recovery in Darwin and Wenman. But very minimal recovery in the central and southern Galapagos Islands. There's been coral bleaching events elsewhere that have killed off all the corals. But what makes the Galapagos unique is that the entire reef framework itself was actually completely bio-eroded in about 10 years. Other places usually the non-living coral reef framework will persist over time much longer. The lack of recovery and bio-erosion of the underlying reef framework likely are caused in part by the fact that pH is much lower in the southern and central Galapagos. Derek measures the carbon dioxide, or Co2 levels, in the water around the islands. Research has shown that increased levels of cO2 in the oceans will have devastating impacts on corals. The oceans act as a carbon sink for atmospheric C02. So the oceans naturally equilibrate with the atmosphere over time. About 30 percent of all the fossil fuel carbon dioxide, that's what we put in the atmosphere since the industrial revolution, has been absorbed by the oceans, which actually raises the ocean's acidity and lowers the ocean's pH. So this process is termed ocean acidification. The more acidic it becomes the harder it is for coral to deposit its skeleton. The rate of change in ocean pH that's occurring right now hasn't occurred in the oceans for at least the past 300 million years. So what that means is that organisms and animals that live in the ocean are experiencing a change in the environmental conditions at a rate that's greater than anything they've seen, since prehistoric times. The Galapagos serve as the perfect natural laboratory to study how corals will be affected by more acidic oceans. So the unique nature of the Galapagos is such that the different islands have different pH conditions. Some areas of the archipelago already experience double the amount of dissolved carbon dioxide in the water compared to most regions where corals exist now. These c02 conditions in the Galapagos basically approximate what we expect for the rest of the oceans with ocean acidification at the middle or end of this century. To study the coral calcification rates, Derek extracts cores from a species of coral that is common in the Pacific. We used a pneumatic hand drill fit with a diamond coring bit at the end, so we can attach this directly to a scuba tank. And what this allows us to do is to take a sample down the main growth axis of the coral. And corals lay down density bands, much in the same way that trees put down tree rings. So every year, corals go through a natural oscillation in their skeletal density. This process may look destructive, but its impact on the coral is similar to that of a biopsy in a human. We take a cement plug or use some coral rubble, that doesn't have anything living or growing on it. We plug up the hole and then fix it with an underwater epoxy. And then the coral is able to grow tissue right back over that that lesion within a few years. The overwhelming majority of the time the coral isn't harmed from the sampling. Once back in the lab in Miami, Derek analyzes the cores. So this is an example of a coral core we take out of a massive coral skeleton. We cut it down and put it into our CT scanner. And then with that CT scanner we can look at that coral core in three dimensions of the x ray images which provides us a metric of the density of the core as you go down over time and as you look at coral growth. So what we see here is an example of about 10 years of growth from a coral core, and you see these high density peaks that occur on regular intervals. So that's associated with the annual high-density peak formation that occurs in coral growths. So we use the distance between these peaks to get an estimate of the annual growth rate of coral skeletons. And then once we have that data of coral growth with time, we can understand how various disturbances or environmental conditions like sea temperature may have impacted rates of coral growth. What we see is that the calcification rates at the different regions vary considerably. And as you increase in pH the calcification rates also increase. Experts forecast that climate change will not only lead to ocean acidification, but rising water temperatures will also lead to more frequent bleaching events. The most recent research that's been done, has shown that globally all coral reefs are going to begin experiencing annual bleaching events, somewhere around the year 2050. And what we've learned in the Galapagos is that it only takes one coral bleaching event to kill an entire reef and have that reef framework be completely eroded and you know almost non-existent after 10 years. The combination of increased temperatures and low pH are something we're just now beginning to understand the effects of on coral reef ecosystems. There could potentially be a c02 tipping point in the Galapagos, at which coral reefs are no longer able to recover from strong coral bleaching events. The only coral reef in the entire Galapagos archipelago that has persisted and survived the repeated coral reef bleaching events, has been in a place where pH is naturally highest. As pH declines from that location, the coral reefs there have not fared well at all, and have shown little resilience or recovery from the warm water bleaching events. So this suggests that there could be a threshold to coral reef resilience from thermal stress at some kind of c02 level. In other words, as the pH of the oceans declines, coral reefs will likely lose their ability to rebound from warm water events and coral bleaching over time. So this is a very sobering future for coral reefs based on how we expect the climate system to change. The collection of scientific data underwater is serious business, but sometimes it is difficult for the scientists to ignore the spectacular and unique wildlife that is all around them. You definitely do see sea lions and they can impact your work because they are like underwater puppies, and extremely playful. So they often times will swim away with your gear when you're not looking. So you know it's not uncommon to see someone swimming after a sea lion shaking their fist while doing work in the Galapagos. Occasionally in the early days in the 70's when we were down there a penguin swam over the corals, and so this was certainly something that you wouldn't see very often. So that was pretty exciting. Another researcher along on the expedition is Dr. Iliana Baums from Pennsylvania State University. Together with one of her students, she has discovered a species of coral in the Galapagos that was previously thought to occur only in Hawaii. It's very hard to distinguish visually from the most common of the reef building species out here. The two species look so much alike, the only way to tell them apart is by looking at their DNA in a lab. To do so, and to understand how common the newly identified species is, the experts collect coral samples in the field. The reason why we want to know how much we have of one or the other species is because they interact with their environment very differently. One of the species deals with climate change differently, so when waters get warm one of the species bleaches more frequently than the other. If water temperatures keep rising with climate change you might get one species to survive better than the other, so there might be a shift in the ecosystem in terms of what species it is composed of. Understanding this species diversity is crucial for managers as they try to predict how reefs will respond to climate change in the future. The four week expedition in the Galapagos led to the collection of a large amount of data and new insights. Scientific research is vital for the long-term survival of Galapagos. Ecuador has some resources. But we need to have scientists from different parts of the world to find out what is going on in this special ecosystem like Galapagos. And as more scientific work is done it's a great help for Galapagos. I think the corals in the southern and central islands are not showing any signs of recovery. So that is not encouraging. But it's a reality. And we found that the reefs continue to recover in the northern islands. So this is encouraging. We're certainly hopeful this trend will continue. We know coral reefs are in trouble. But what we've seen in a lot of these areas is they are amazingly resilient and they can rebound. And we know that climate change is predicted to just get worse. But what our hope is, is that corals can adapt to climate change. The Galapagos and its unique creatures are a symbol of adaptation, having provided important clues about the way life evolves on planet Earth. Now they may also serve as a window into the future -- providing a glimpse of how corals may adjust to the drastic changes forecast to occur in the world's oceans. Major funding for this program was provided by The Batchelor Foundation, encouraging people to preserve and protect America's underwater resources. And by Divers Direct Emocean Club, inspiring the pursuit of tropical adventures and scuba diving. And by the Do Unto Others Trust.
B2 中高級 "加拉帕戈斯:未來之窗 "全集介紹 ("Galápagos: Windows into the Future" Full episode) 153 9 kevin 發佈於 2021 年 01 月 14 日 更多分享 分享 收藏 回報 影片單字