“Even if you never have the chance to see or touch the ocean, the ocean touches you with every breath you take, every drop of water you drink, every bite you consume. Everyone, everywhere is inextricably connected to and utterly dependent upon the existence of the sea.” -Sylvia A. Earle, The World Is Blue: How Our Fate and the Ocean's Are One
Our planet is undergoing one of the most significant changes in climate since the dinosaurs went extinct, ten times faster than any shift in the past 65 million years (1). Scientists use complex terms like ocean acidification, eutrophication, and deoxygenation to illustrate the complicated effects of climate change on the ocean, unintentionally creating a frustrating knowledge gap for citizens and policymakers alike. Science communication has played a crucial role in filling this gap, but more work is needed to educate the global community about our connection to nature - specifically to the ocean, and how its future affects ours.
"If all the warmth that went into the top 1.25 miles of the ocean between 1955-2010 had instead gone into the air, the earth would have already warmed 36 degrees Celsius, equivalent to 96.8 degrees Fahrenheit."
To keep it simple: the ocean is a powerful tool in the fight against climate change. Among many other things, it has slowed greenhouse warming by absorbing excess heat-trapping carbon dioxide from the atmosphere. As a result, our superhero ocean has become more acidic and a less hospitable environment for a variety of marine creatures. However, the ocean continues to absorb about 25 percent of all CO2 emissions, captures 90 percent of the heat created by these emissions, and produces over half of the Earth’s oxygen (2). If all the warmth that went into the top 1.25 miles of the ocean between 1955-2010 had instead gone into the air, the earth would have already warmed 36 degrees Celsius, equivalent to 96.8 degrees Fahrenheit (3). While we know that the ocean has been saving us from experiencing the worst-case effects of climate change with its mighty carbon sink and powerful ability to absorb excess heat, scientists are questioning how much longer it can save our species. Interestingly, the answer may lie in the oceans themselves and offer clues to what the future may hold. We’ll explore a few well-documented examples below, starting with Kemp's Ridley Sea Turtles.
Increasing Pressures on Kemp’s Ridley Sea Turtles
For the past 80 years, scientists have documented the effects of climate change on the Kemp’s Ridley Sea turtles. Kemp’s Ridley Sea turtles are the smallest sea turtles in the world – they average only two feet long and weigh under 100 lbs. as an adult. They also happen to be the most endangered species of sea turtles worldwide. During nesting season, Kemp’s Ridley Sea turtles once filled the beaches of Rancho Nuevo, Mexico, by the tens of thousands. Although Kemp’s Ridley females nest more often than any other sea turtle species, the annual nesting population began to decline in the mid-1940s, which steadily continued over the next couple of decades and plunged to a record low of 702 in 1985 (4). There are numerous reasons for the sharp decline in Kemp’s Ridleys Sea Turtle populations. Their small size and daylight nesting habits render them more susceptible to predators. They have historically been victims of bycatch in commercial and recreational fishing gear. Although recent modifications to fishing gear reduced accidental captures, climate change is the biggest threat to this species’ population (5).
For centuries, Kemp’s Ridley Sea turtles have followed a predictable, low-to-high latitude annual migratory pattern. Their migration brings them into dangerous conditions, depending on oceanic currents and unusual weather patterns. The Kemp's Ridley Sea turtle is a cold-blooded marine reptile, and like most reptiles, their body changes temperature with the surrounding environment. As climate change accelerates, Kemp’s Ridley Sea turtles are increasingly caught in northerly warm water surface currents that unexpectedly and rapidly shift to cold water in the North Atlantic. Prolonged exposure to the cold causes debilitating lethargy, which leads to “cold-stunned turtles” – a type of deadly reptilian hypothermia. Within the past 40 years, over 4,700 Kemp’s Ridley Sea Turtles have stranded on Cape Cod; these cold-stunning events have intensified annually, requiring more significant investment in recovery efforts (6).
Drs. Sean Perry and Alexa Delaune, two veterinarians at the Mississippi Aquarium in Gulfport, specialize in sea turtle medicine and rehabilitation. Delaune and Perry are an essential part of Kemp’s Ridley recovery effort, but in our interview, Delaune says they see themselves as just “one piece of the puzzle.” She emphasizes that it takes immense coordination and planning on behalf of the National Oceanographic and Atmospheric Association (NOAA) and the New England Aquarium (NEAq) to create the sea turtle recovery and rehabilitation network that exists. After paralyzed, cold-stunned Kemp’s Ridleys are recovered on the beaches of Cape Cod; the rehabilitation process begins at the New England Aquarium, where the turtles are treated, stabilized, and, as the NEAq’s facilities reach capacity, are prepped for travel to one of the many sea turtle treatment centers across the nation.
However, climate change creates complex and unpredictable negative externalities. The Kemp’s Ridley Sea turtles’ ultimate survival is determined by the amount of CO2 emitted into the atmosphere, a critical factor in the warming sea surface temperatures. Many reptilian species, including Kemp's Ridley Sea Turtles, display temperature-dependent sex determination (TSD) rather than genetic sex determination. Dr. Perry emphasized that at the time of birth, half-a-degree to one-degree Fahrenheit change in water temperature greatly affects which gene is activated to determine the sex of the Kemp's Ridley Sea Turtles. Essentially, as the water continues to warm, some scientists predict (and are observing) that the Kemp’s Ridley Sea Turtle population eventually could contain only females, severely limiting their species’ chance for long-term survival (7).
Manatees Under Stress
Affectionately referred to as “sea cows,” manatees have historically taken refuge in Florida’s lagoons during the winter seeking warmer waters. These marine mammals are warm-blooded but prefer to stay in 68 degrees or warmer water temperatures. In cold water environments, manatees experience dangerous stress, whose symptoms include white body lesions and, in some cases, death. So at first glance, climate change may seem beneficial for the manatees. But the manatees’ food source (seagrass) disappears from their winter lagoon homes due to a stark increase in algal blooms (8).
Most deaths have occurred in Indian River Lagoon, an estuary stretching more than 150 miles down the middle of Florida’s east coast. Here, decades of pollution from farm fertilizers and residential developments have killed off vast swaths of seagrass that are manatees’ main food source (9). Harmful algal blooms can result from runoff from agricultural fertilizers and pesticides that contain high amounts of nitrogen and phosphorus. While a certain amount of nitrogen and phosphorous supports the growth of ecologically important aquatic plants, the overabundance of nutrients leads to an overgrowth of phytoplankton, better known as algae, which pollutes the water by reducing water clarity and quality: the excess nitrogen and phosphorous cause harmful algal blooms that block sunlight and muddy the ocean’s waters, creating an inhospitable environment for seagrass growth.
Without an adequate food source, manatees leave the lagoon’s warmer waters and suffer in colder waters as they search for additional sustenance. They are left with an unpleasant choice: starvation or death by cold water. Furthermore, certain algal blooms that contain specific phytoplankton species, some of which found in Florida's lagoon, generate a “red tide” when conditions like temperature, nutrient levels, and wind align. These microscopic algae forms produce toxins that are often fatal for marine animals and sicken humans (10).
The Plight of the California Sea Lion
California's sea lion pups are yet another victim of climate change’s negative, concomitant impacts. From 2013 to 2016, the pups washed up on the state’s beaches in alarmingly high numbers (11). Their mothers rely on sardines as their primary food source while pregnant. However, the abnormally warm waters have prevented the usual upwelling of cool, nutrient-rich waters that attract swaths of sardines. Sea lion mothers must travel farther up the coast for food and leave their pups behind. As a result, the sea lion pups are not receiving adequate nutrition and either die in the warming waters or wind up on beaches malnourished and need rescue.
Marine scientists and biologists attribute the rise in sea lion deaths to a warm marine heatwave that has altered the coast’s ecological landscape composition throughout the years (12). The unusual oceanographic conditions, which scientists nicknamed “the Blob,” increased the sea surface four to ten-degrees along the Pacific coast, and initially was thought to be a product of El Niño; however, El Niño’s signature migratory pattern, initiating in the equatorial Pacific and continuing northward, did not match up with the Blob’s migratory pattern. According to NASA researcher Chelle Gentemann, the Blob had formed in the Gulf of Alaska and spread south. El Niño was relatively mild that year (13).
California sea lion pups were not the Blob’s only victims. Upwelling regions are characterized as highly productive areas which circulate the colder, more nutrient-rich waters to the surface of the ocean while the warmer waters circulate to the ocean’s lower levels. Warmer waters contain less oxygen and nutrients and provide an amenable environment for toxic algae blooms. In contrast, colder water benefits the regional ecosystem with welcoming habitats for marine organisms, like plankton and small forage fish. There are only five upwelling regions globally, and one of them is located on the California coast. In 2013, the temperature change and lack of wind disrupted the California Current’s upwelling region. As a result, the marine biome failed to produce the necessary nutrients to support the typical organisms and marine creatures found in the area for the next three years.
The ocean has robust capabilities in sequestering carbon dioxide from the atmosphere. Yet, unresolved scientific questions remain about the ocean’s rate of CO2 uptake and how much gets respired back through the ocean’s biological processes. We know that a historical sea devoid of life would have resulted in a much higher concentration of CO2 in the atmosphere – and associated climate change. Yet, while speaking with George Leonard, the Chief Scientist of the Ocean Conservancy, he pointed out that we don’t know how much marine life - and the role of biodiversity in particular – is needed to maintain the carbon drawdown role that the ocean currently plays to cross the threshold of the ocean’s capacity to function as a carbon sink. Perhaps, instead of promoting blue carbon projects that tout end-all solutions by planting new mangroves and seagrasses, we recognize the greater value in projects that protect our earth’s marine biodiversity or revive coastal environments before they disappear due to climate change altogether.
In conclusion, it is imperative to realize climate change’s most significant externality; contrary to popular belief, it is not the earth’s future - it’s ours. Earth has experienced its fair share of climate change events over its 4.5-billion-year history. However, humans never caused the phenomenon. A healthy marine ecosystem can maintain the physical and biological structure within normal bounds and continuously provide ecosystem services.In contrast, an unhealthy marine ecosystem experiences pressures that change its physical structure, chemistry, or living community.
"it is imperative to realize climate change’s most significant externality; contrary to popular belief, it is not the earth’s future - it’s ours"
The stark increase in marine biodiversity loss events over the past few decades could be sending an ominous message to humans about our chances for survival. We must prevent more biodiversity loss and focus on biodiversity restoration to improve our outcomes. Recent weather disasters have already demonstrated the present and future risk of continual biodiversity loss for residents in climate-affected areas. The local community’s role and involvement, including communities with Indigenous populations, are essential in biodiversity conservation and restoration efforts, and we should try learn as much as possible from their rich history of biodiversity stewardship. The world has proven its incredible ability to adapt and survive throughout its 4.5-billion-year history. Our actions, starting now, will dictate how many of us do, too.
About The Author: Alyssa is a Climate Change and Sustainability Policy graduate student at Northeastern University, and currently works at Anthropogenic as an Associate Director of Impact and Monitoring. Her research focuses on topics such as transformational adaptation and mitigation projects in climate finance, carbon & nutrient trading markets, and the blue economy. She holds a BA in Comparative Government from Bowdoin College and a MA in Spanish Linguistics from Middlebury College.