Category: Oceans

Understanding the Impact of Climate Change on Marine Mammals

/ activist360
Mother and baby sperm whale
A mother sperm whale and her calf off the coast of Mauritius. The calf has remoras attached to its body. Credit: Gabriel Barathieu, January 26, 2013.

Our oceans are suffering the impact of climate change. From inshore environments to the deep ocean, marine ecosystems are undergoing significant transformations due to rising temperatures, increased carbon dioxide levels, and shifting environmental conditions. This research article by National Oceanic and Atmospheric Administration (NOAA) researchers published in PLOS ONE delves into the intricate relationship between climate change and marine mammals. The study focused on the United States’ western North Atlantic (WNA), Gulf of Mexico (GOMx), and Caribbean waters.

Drivers Impacting Marine Life

Global climate change has ushered in a multitude of alterations that stem from a handful of key drivers. Rising levels of heat and carbon dioxide in the Earth’s atmosphere are at the forefront. Here’s a closer look at the other major factors:

1. Increasing Ocean Temperatures

As the Earth’s temperature rises, so too do the temperatures of our oceans. This phenomenon is particularly evident in the western North Atlantic (WNA), where sea surface temperatures have been increasing rapidly. These rising temperatures have direct and indirect consequences for marine mammals that call these waters home.

2. Rising Sea Levels

One of the most visible effects of climate change is the rise in sea levels. This phenomenon is especially pronounced in regions like the southeastern United States, Gulf of Mexico (GOMx), and the Caribbean Sea. The accelerating sea level rise poses a significant threat to coastal ecosystems and the marine life they support.

3. Decreasing Dissolved Oxygen

Climate change also contributes to declining levels of dissolved oxygen in our oceans. This is a particularly alarming trend for marine mammals, as many of them rely on oxygen-rich environments to thrive.

4. Declining Sea Ice Coverage

In polar regions, the decline in sea ice coverage is a stark indicator of climate change. This has profound implications for marine mammals like polar bears and seals, which depend on sea ice as a platform for hunting and resting.

5. Ocean Acidification

The increasing levels of carbon dioxide in the atmosphere are not only raising temperatures but also leading to ocean acidification. This can have devastating effects on marine life, particularly species with calcium carbonate shells or skeletons.

6. Shifting Precipitation Patterns

Climate change also drives changes in precipitation patterns, impacting the salinity of ocean waters. These shifts can have cascading effects on marine ecosystems and the species that inhabit them.

Impacts on Marine Mammals

The effects of climate change are not limited to the physical environment; they also dramatically affect marine communities, including marine mammals. Here are some of the key ways in which climate change impacts these majestic creatures:

1. Altered Distribution and Behavior

Marine mammal species with restricted geographical distributions and habitat tolerances are particularly vulnerable. The changing conditions of their environment leave them with limited opportunities to adapt.

2. Disrupted Prey Availability

Marine mammals rely on stable environments where prey availability is relatively predictable. Climate change can disrupt these ecosystems, leading to food scarcity and challenges in feeding.

3. Climate-Related Shifts in Distribution

Some marine mammal populations, such as ice-associated seals and subarctic cetaceans, have already shown shifts in distribution due to climate change. These changes have significant implications for their conservation and management.

4. Predictive Challenges

Predicting climate-driven changes in marine mammal distribution, phenology, and abundance is a complex task. However, advancements in modeling tools and approaches are improving our ability to make informed predictions.

Assessing Climate Vulnerability

Understanding the vulnerability of marine mammals to climate change is crucial for their conservation. Climate vulnerability assessments (CVAs) play a pivotal role in identifying species at risk. These assessments take into account factors such as exposure, sensitivity, and adaptive capacity.

Trait-Based CVAs

One approach to CVAs involves trait-based assessments, which consider the biological or ecological traits of species that are linked to climate responses. While this method provides less resolution than quantitative approaches, it offers a rapid and adaptable way to assess vulnerability.

NOAA’s Role in Marine Mammal Protection

In the United States, the NOAA has a mandate to protect and recover marine mammal species under the Endangered Species Act (ESA) and Marine Mammal Protection Act (MMPA). To address climate-related threats to marine mammals, NOAA conducts trait-based CVAs for stocks in the WNA, GOMx, and Caribbean waters.

Conclusion

Climate change presents a profound challenge to marine mammals in the United States’ WNA, GOMx, and Caribbean waters. It is a complex issue that requires a multifaceted approach to address. As the world grapples with the consequences of a changing climate, it is imperative that we prioritize the conservation and protection of these incredible creatures. NOAA’s efforts, including trait-based CVAs and vulnerability rankings, provide valuable tools for understanding and mitigating the effects of climate change on marine mammals.

By comprehensively assessing vulnerability and taking proactive measures, we can work towards safeguarding the future of our marine mammal populations.

Source: Lettrich, M.D. et al. (2023). Vulnerability to climate change of U.S. marine mammal stocks in western North Atlantic, Gulf of Mexico, and Caribbean. PLoS ONE, 18(9), e0290643.

Despite shrinking ‘Dead Zone’, Gulf Coast grapples with massive fish die-off

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A shrimp boat trawls for shrimp in the Gulf of Mexico. (Image credit: NOAA Fisheries)
A shrimp boat trawls for shrimp in the Gulf of Mexico. (Image credit: NOAA Fisheries)

NOAA anticipated a remarkably smaller ‘Dead Zone’ in Gulf of Mexico this summer

The National Oceanic and Atmospheric Administration (NOAA) predicted a “dead zone” in the Gulf of Mexico this summer, an oxygen-deprived area spanning about 4,155 square miles that can prove lethal to marine life. This estimate, while significant, is lower than the 36-year average of 5,364 square miles. The dead zone occurs annually due to excessive nutrient pollution from human activities within the Mississippi River watershed.

The US Geological Survey (USGS) tracks key factors such as river discharge and nutrient loading, which contribute to the dead zone. In May 2023, there was a 33% decrease in river discharge, a 42% decrease in nitrate, and a 5% decrease in phosphorus levels compared to the long-term averages from 1980 to 2022. These nutrients instigate an algal bloom that, upon death and decay, depletes water oxygen levels, endangering marine life, especially bottom-dwelling species.

NOAA’s hypoxia forecasts are designed to help coastal managers and stakeholders proactively mitigate the impacts of hypoxia. The data also inform nutrient reduction targets aimed at curbing future dead zones. The Interagency Mississippi River and Gulf of Mexico Hypoxia Task Force aims to reduce the dead zone to 1,900 square miles by 2035.

Despite smaller ‘Dead Zone’, thousands of fish perish on Texas Gulf Coast

The New York Times along with several other media outlets reported that on Friday, tens of thousands of fish started washing ashore along the Texas Gulf Coast due to a combination of environmental conditions that depleted oxygen levels in the warm waters. The incident was described as a “perfect storm” of poor conditions by Bryan Frazier, the director of Brazoria County Parks Department. Warm water holds less oxygen than cold water, and the calm, cloudy weather obstructed the usual ways oxygen is infused into ocean water. The fish are thought to have been trapped in shallow, warm water where the oxygen supply diminished.

Experts suggest that climate change could be contributing to such incidents as warmer waters become more common. Katie St. Clair, the sea life facility manager at Texas A&M University at Galveston, said that rising water temperatures could lead to more such events, especially in shallow, near-shore environments.

Frazier noted that these fish kills are not uncommon during warmer periods and predicted local water conditions would improve as ocean waves reintroduce oxygen and fish leave low-oxygen areas. However, the United Nations reported in 2019 that warmer ocean waters have increased incidences of hypoxia (low oxygen levels), posing threats to fish populations.

The fish kill could significantly impact the environment as the dead fish, primarily Gulf menhaden, play a crucial role in the local ecosystem. Clean-up operations are ongoing to prevent the dead fish from rotting in the midday heat.

Ocean warming study so distressing, some scientists didn’t even want to talk about it

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Ship in the ocean, Hamburg, Germany. Photo by Martin Damboldt from Pexels.
Ship in the ocean, Hamburg, Germany. Photo by Martin Damboldt from Pexels.

“This is one of those ‘sit up and read very carefully’ moments,” said one science journalist.

By Julia Conley, Common Dreams

Scientists are so alarmed by a new study on ocean warming that some declined to speak about it on the record, the BBC reported Tuesday.

“One spoke of being ‘extremely worried and completely stressed,'” the outlet reported regarding a scientist who was approached about research published in the journal Earth System Science Data on April 17, as the study warned that the ocean is heating up more rapidly than experts previously realized—posing a greater risk for sea-level rise, extreme weather, and the loss of marine ecosystems.

Scientists from institutions including Mercator Ocean International in France, Scripps Institution of Oceanography in the United States, and Royal Netherlands Institute for Sea Research collaborated to discover that as the planet has accumulated as much heat in the past 15 years as it did in the previous 45 years, the majority of the excess heat has been absorbed by the oceans.

In March, researchers examining the ocean off the east coast of North America found that the water’s surface was 13.8°C, or 24.8°F, hotter than the average temperature between 1981 and 2011.

The study notes that a rapid drop in shipping-related pollution could be behind some of the most recent warming, since fuel regulations introduced in 2020 by the International Maritime Organization reduced the heat-reflecting aerosol particles in the atmosphere and caused the ocean to absorb more energy.

But that doesn’t account for the average global ocean surface temperature rising by 0.9°C from preindustrial levels, with 0.6°C taking place in the last four decades.

The study represents “one of those ‘sit up and read very carefully’ moments,” said former BBC science editor David Shukman.

Lead study author Karina Von Schuckmann of Mercator Ocean International told the BBC that “it’s not yet well established, why such a rapid change, and such a huge change is happening.”

“We have doubled the heat in the climate system the last 15 years, I don’t want to say this is climate change, or natural variability or a mixture of both, we don’t know yet,” she said. “But we do see this change.”

Scientists have consistently warned that the continued burning of fossil fuels by humans is heating the planet, including the oceans. Hotter oceans could lead to further glacial melting—in turn weakening ocean currents that carry warm water across the globe and support the global food chain—as well as intensified hurricanes and tropical storms, ocean acidification, and rising sea levels due to thermal expansion.

A study published earlier this year also found that rising ocean temperatures combined with high levels of salinity lead to the “stratification” of the oceans, and in turn, a loss of oxygen in the water.

“Deoxygenation itself is a nightmare for not only marine life and ecosystems but also for humans and our terrestrial ecosystems,” researchers from the Chinese Academy of Sciences, the National Center for Atmospheric Research, and the National Oceanic and Atmospheric Administration said in January. “Reducing oceanic diversity and displacing important species can wreak havoc on fishing-dependent communities and their economies, and this can have a ripple effect on the way most people are able to interact with their environment.”

The unusual warming trend over recent years has been detected as a strong El Niño Southern Oscillation (ENSO) is expected to form in the coming months—a naturally occurring phenomenon that warms oceans and will reverse the cooling impact of La Niña, which has been in effect for the past three years.

“If a new El Niño comes on top of it, we will probably have additional global warming of 0.2-0.25°C,” Dr. Josef Ludescher of the Potsdam Institute for Climate Research told the BBC.

The world’s oceans are a crucial tool in moderating the climate, as they absorb heat trapped in the atmosphere by greenhouse gases.

Too much warming has led to concerns among scientists that “as more heat goes into the ocean, the waters may be less able to store excess energy,” the BBC reported.

The anxiety of climate experts regarding the new findings, said the global climate action movement Extinction Rebellion, drives home the point that “scientists are just people with lives and families who’ve learnt to understand the implications of data better.”