Plastic Pollution

Plastic Pollution in the Marine Environment” is a review article that describes the describes the role of plastic pollution in marine environments. Authors G.G.N. Thushari and J.D.M. Senevirathna believe that “the ecological and socio-economic impacts of plastic pollution are interconnected”. Marine organisms can ingest, become entangled in, or otherwise be impaired by plastic pollutants. This can negatively impact tourism, fisheries, human health, and services gained by people.

Some suspension feeders and benthic organisms likely mistake microplastic particles for food because the plastic particles are roughly the same size as feeding matter, such as plankton. Ingestion of plastic debris can be lethal or sub-lethal for marine species. Sub-lethal effects can be impaired reproduction ability, loss of sensitivity, the inability to escape from predators, loss of mobility, decreased growth, and body conditions, according to the review article.

Toxic chemicals like flame retardants, metal ions, and antibiotics are incorporated in some plastics and can also be ingested by wildlife. Fish that have been exposed to these chemicals are unsafe for human consumption. Contaminated seafood sources can create adverse health effects on people.

Some plastics float near the water’s surface while more dense plastics sink down into the deep oceans. If a piece of plastic’s density is greater than that of seawater, the plastic will sink. Plastic in seawater less dense than itself will float. Plastics take on countless shapes and sizes, ranging from large objects, to centimeter-sized scraps, to microscopic bits. Both large and microscopic plastics, therefore, have the potential to interact with marine organisms at all levels of the water column.

The Fundamental Links Between Climate Change and Marine Plastic Pollution

As stated in the review article, extreme climatic conditions such as storms, floods, and monsoons can increase the concentration of plastic in an area. Plastic is spread by wind and water currents. Weather patterns are essentially circulation systems that move plastics through environments. The physical effects of climate change then, are likely influencing the mobilization of plastics between land, sea, and freshwater systems.

Climate change and plastic pollution are linked. While climate change contributes to the movement of plastics, plastics contribute to climate change by being a greenhouse source at all stages of their lifetimes, which fuels global warming.

The Arctic Has Warmed Nearly Four Times Faster Than the Globe Since 1979

Artic land ice and snow

On August 11, 2022, a study was published in Nature Communications Earth & Environment on Arctic amplification (AA), the relatively higher rate of warming in the Arctic compared to all other parts of the globe. AA, also known as polar amplification, is thought to be due to feedback from reduced cold-season ice and snow cover.

In other words, ice loss in the Arctic causes the region to have greater temperature change averages than the rest of the planet. Though this fact has been well established in previous literature, authors of “The Arctic Has Warmed Nearly Four Times Faster Than the Globe Since 1979” declare that AA is presently happening at higher ratios than what’s been reported in the past.

According to authors Mika Rantanen, Alexey Karpechko, Antti Lipponen, Kalle Nordling, Otto Hyvärinen, Kimmo Ruosteenoja, Timo Vihma, and Ari Laaksonen, warming ratios from previous studies are based on possibly outdated estimates that do not include the most recent observations. If true, previous studies will have likely underestimated present-day Arctic heating rates.

Mika Rantanen and colleagues used several observational datasets for the Arctic region to more accurately quantify the current magnitude of AA. They included four climate models in their calculations: NASA’s Goddard Institute for Space Studies Surface Temperature version 4 (GISTEMP), the Berkeley Earth temperature dataset (BEST), the Met Office Hadley Centre/Climatic Research Unit version (HadCRUT5) and ERA5 reanalysis.

Arctic Circle

Rantanen’s team claims that “the period of interest and the area of the Arctic can be defined in multiple ways”. To put it another way, AA estimates will vary according to the timeframe studied and the definition of what qualifies as the geographic area of the Arctic. Rantanen’s team primarily defined the Arctic using the Arctic Circle as the southern boundary (66.5–90N, the area located above 66.5 degrees latitude) and focus on warming trends for the last 43 years.

During the last 43 years, more accurate satellite remote sensing data and observations on atmospheric variables and sea ice concentration have become available. This period is crucial for AA calculations, as 1979–2021 is thought to be a period of relatively strong Arctic warming.

Their results are evidence that major portions of the Arctic Ocean warmed nearly four times faster than the globe from the years 1979–2021, whereas previous studies report the Arctic warming at nearly twice, or about twice as quickly as the global average. AA was most severe in Novaya Zemlya sea areas, which warmed up to seven times as fast as the global average.

Ice Melt

There are multiple reasons for accelerated Arctic heating. Human-caused global warming is likely an integral cause of recent heating trends. On top of that, ice loss within the Arctic Circle plays a role. Ice that was once frozen for all or most of the year, is increasingly shrinking. Sea ice loss reinforces global warming because melting ice gives way to a darker ocean. Brightly colored snow and ice surfaces reflect sunlight back into space at a higher rate than the surfaces of darkly colored seawater, which are more efficient at absorbing sunlight and heat energy.


Climate Change Is Costly

Climate change is already underway and is predicted to worsen. Human industrial activities, most notably those that involve the use of fossil fuels, are partly responsible for the accumulation of excess greenhouse gases in Earth’s atmosphere. The resultant increased rate of warming promotes droughts, wildfires, sea level rise, and other hazardous outcomes for people, crops, wildlife, and infrastructure.

The impacts of climate change could cost $1.9 trillion per year (in today’s dollars) by 2100 according to Frank Ackerman and Elizabeth A. Stanton of the Global Development and Environment Institute and Stockholm Environment Institute-US Center. Their analysis is based on just four symptoms of global warming: hurricane damages, real estate losses, energy costs, and water costs. They go on to state that immediate greenhouse emissions reductions are necessary to prevent most of global warming’s damages.

Other problems associated with climate change like declining biodiversity and decreased agriculture production will likely lower economic output in countries that rely on agriculture for total productivity. Jobs in agriculture, fishing, logging, and aquaculture require specific climate conditions and predictable weather patterns so that food, medicine, and material demands for human populations can be met.

Plastic Pollution in the Arctic

ice in the Arctic ocean
Ice in the Arctic ocean

A study, “Plastic Pollution in the Arctic” reports that Arctic wildlife regularly ingest, become entangled in, or be smothered by plastic debris. Arctic species such as sculpin (Triglops nybelini), the northern fulmar (Fulmarus glacialis), and belugas (Delphinapterus leucas) have been found with plastic inside them. Plastic ingestion may even affect marine invertebrates like zooplankton in the eastern Canadian Arctic and the Fram Strait (a sea channel between Greenland and Svalbard).

Plastics from agriculture, landfills, dumping, industry, household products, fisheries, offshore industry, and other such sources are routinely carried to and within the Arctic by atmospheric and aquatic circulation systems. Transported plastics from local and distant sources are therefore highly distributed. The United Nations estimates that approximately 150 million tons of plastic debris may be scattered across the Arctic. Plastics are found on Arctic shores, in varying levels of the water column, in sea ice, and inside the bodies of marine biota.

Plastic Pollution

Circulation systems, including wind, ocean currents, and freshwater river flows, move plastic pollution through Arctic ecosystems, especially as they break down and fragment into smaller constituent pieces. The physical effects of global warming, then, influence the distribution of plastics and microplastics in the Arctic by increasing the frequency and or intensity of extreme weather events, like flooding and windstorms. Sea level rise or higher poleward wind speeds from global warming have the potential to transport greater levels of plastic debris to Arctic ecosystems.

Climate Change and Plastic

plastic bottle in water

An article titled, “The Fundamental Links Between Climate Change and Marine Plastic Pollution”, describes the interactive relationship between climate change and marine plastic pollution. The article’s authors claim that climate change and marine plastic pollution are linked in three ways: a) the production of plastic relies on fossil fuel extraction and is thus a greenhouse gas contributor b) climate and weather influence the distribution and spread of plastic pollution across environments c) marine ecosystems and species are vulnerable to plastic pollution and climate change.

Does Plastic Cause Climate Change?

The rise in plastic demand is likely due to its reputation as an inexpensive and lightweight material that has a wide range of uses. Plastic is used for packaging, electronics, toys, utensils, safety gear, and infrastructure. Even so, plastic drives greenhouse gas emissions throughout multiple stages of its so-called “lifecycle”, from extraction and refining to transportation, incineration, and recycling.

From production to end-of-life, plastic materials release potent greenhouse gases, like carbon dioxide, methane, and ethylene. Greenhouse gases from plastic materials must therefore contribute to ocean heating and climate change. As common plastics degrade, they fragment into microplastics and smaller constituents parts that can be toxic to humans and marine organisms and also intensify ocean warming. Bio-based plastics, plastics made from biomass, are no exception. While bio-based plastics do produce fewer greenhouse gases than conventional plastics, they still release heat-trapping molecules during their lifecycles.

How Does Plastic Move Around the World?

The movement of plastics between environments is influenced by climate conditions. Plastics are circulated by the flow of water and wind. Extreme weather, like floods and windy storms, can move plastics from one system to another. For example, flooding riverine systems can transport plastics into the ocean, while tropical storms from oceans can push plastics onto terrestrial surfaces. Releasing plastic into the ocean or onto landfills is not the end of that plastic’s life cycle. Plastic and microplastics continue to impact the ecosystems long after they have been disposed of by humans.

How Does Plastic Affect Marine Ecosystems?

Ingesting plastic can lower the survival odds of certain marine organisms. In some cases, marine animals become entangled by plastic products or have their feeding and breathing pathways obstructed. On top of that, plastic potentially facilitates species migrations because plastic debris attracts encrusting organisms and microbial communities. Therefore both climate change and plastic pollution can contribute to species movement between ocean regions. Increased species mobility can bring about invasive species risks.

Climate change is altering the distribution of many species by subjecting them to novel thermal conditions. When marine habitats heat up, the species within those habitats are usually forced to move to new regions to find more suitable temperatures. Heating oceans also contribute to hypoxic zone and coral bleaching.

The Fundamental Links Between Climate Change and Marine Plastic Pollution

Authors of the review, “The Fundamental Links Between Climate Change and Marine Plastic Pollution”, reason that climate change and plastic pollution are interactive. Plastic production is heavily dependent on fossil fuel use and plastics continue to release greenhouse gases as they degrade in oceans, both of which drive ocean heating and climate change. Inversely, plastic dispersal across environments is influenced by climate factors, including wind, ocean currents, freshwater river flows, and storms.

Climate Change Impacts on Seabirds and Marine Mammals

Seabird species: Australian Pelican (Pelecanus conspicillatus)

A new review published in Ecology Letters, a peer-reviewed scientific journal, assessed seabird and marine mammals’ responses to climate change and climate variability. Researchers based their analysis on data from more than 480 preexisting studies and found that “the likelihood of concluding that climate change had an impact [on either marine mammals sea birds] increased with study duration”. In other words, studies that include data from longer lengths of time are going to be most useful for measuring climate change’s effects on the observed species.

From the 484 peer-reviewed studies that matched the researcher’s inclusion criterion, 2,215 observations were compiled into a database and mapped. This includes 1,685 observations for seabirds and 530 observations for marine mammals. 54% of observations for seabirds were distributed towards the northern hemisphere (39% of observations from temperate and polar regions). For marine mammals, 83% of observations were distributed toward the northern hemisphere (53% of observations from temperate and polar regions). For both seabirds and marine mammals, tropical and subtropical regions represented a mere 8% of total observations.

What Marine Life Is Most Affected by Climate Change?

Authors of the preexisting studies found 38% of total observations to be related to climate change, 49% were attributed to climate variability, and 13% were attributed to both. Climate change refers to the long-term changes in weather patterns, typically over decades or longer, while climate variability is usually thought of as day-to-day shifts in weather.

According to the new review, “a significant majority of observations concluded that climate change had an effect on both the seabird and marine mammal groups across all the response classes”. Response classes include demography, distribution, condition, phenology, behavior, and diet. The analysis also states that species that had more limited temperature tolerance ranges and relatively long generation times were reported to be most affected by changes in climate. Generation times are temporal intervals between the birth of an individual organism and the birth of its offspring.

How Does Climate Change Affect Marine Biodiversity?

The longer the duration of the original studies, the more likely authors were to infer that the observed changes in taxonomic groups were due to climate change rather than climate variability. 189 of the preexisting studies (669 observations) that demonstrated climate change effects had a time span above the estimated average threshold of 19 years. Generally, studies on marine mammals were able to demonstrate climate change responses based on shorter time scales (17± 5 years) versus seabirds (22 ± 3 years).

Another Record: Ocean Warming Continues Through 2021 Despite La Niña Conditions

If you want to measure the rate at which global temperatures are rising, then the world’s oceans are perhaps the best places to observe. This is not only due to the fact that Earth’s surface is more than 70% water-covered, but also because ocean water absorbs 90% or more of Earth’s excess heat. Heat energy captured by ocean water is known as “ocean heat content”, which stores that heat for indefinite periods of time.

Ocean Heat Content

Because ocean water soaks up high proportions of atmospheric heat, they are essential for regulating Earth’s climate. Most of the ocean heating is stored at depths between 0 – 700 meters. Air would warm more rapidly without the ocean’s immense heat trapping capacity. Consequently, heat content builds near oceanic surfaces as they take on increasing amounts of heat.

Average Global Temperature by Year

A new analysis authored by 23 researchers that was published in the journal Advances in Atmospheric Sciences uses data across seven ocean basins to assess world ocean warming trends. The study titled, “Another Record: Ocean Warming Continues through 2021 despite La Niña Conditions”, finds that ocean waters have been monotonously increasing in temperature since the year 1958, and that the rate of change sharply quickened toward the end of the 1980s, with 2021 containing more heat energy than any other year on record since recordings began sixty years ago.

Was 2021 the Warmest Year On Record?

With this, 2021 beat the previous record set by 2020 as the year with the most heat energy in world oceans. The team used preexisting sets of data from various measurement devices in conjunction with climate model simulations to prove the accelerated rate of ocean warming in recent decades. It is then inferred that the relatively recent temperature spikes are mainly attributable to increased greenhouse gas concentrations brought on by human activity. The analysis asserts that “the increased concentrations of greenhouse gases in the atmosphere from human activities trap heat within the climate system and result in massive changes in the climate system”.

Table 1 from study: Another Record: Ocean Warming Continues through 2021 despite La Niña Conditions

Is the Climate Rising?

The study lists 2018, 2017, 2019, 2020, and 2021 (in order from least hot to most hot) as the hottest five years of the global ocean since the year 1955. These 5 years, which are quite recent and in close proximity to one another. This suggests that mean temperatures are approaching new highs.

Cowspiracy Ocean Facts Summary

fish near water surface
Fish near water surface

While fisheries do generate food and profit, they could be doing much more harm than good for underwater ecosystems. The film Cowspiracy makes a convincing case for the deleterious affect that large-scale fishing operations have on ocean environments, species variety and species abundance. Cowspiracy depicts modern fishing as a largely unsustainable industry that could lead to fishless oceans by 2048.

Fishing As Depicted By Cowspiracy

Fish and other marine life are mostly hunted as food. However, some species are used for other commodities. Sharks, for example, are sometimes hunted for their skin which can be used in the making of leather. Other species like whales and manatees are regularly harmed or killed unintentionally by getting caught in fishing nets. The Cowspiracy Facts page sites a Food and Agriculture Organization (FAO) document which states that in the year 2017, between 51 – 167 billion farmed fishes had been killed for food.

That same year an estimated 250 – 600 billion crustaceans were also farmed and killed for food. Even animals that are not eaten by humans are caught and killed inadvertently because of drift netting or trawling. Susan Hartland of Conservation Society says that animal populations are being extracted from oceans more quickly than they can recover. Marine species are therefore collapsing under the immense pressures of modern hunting. The unintended catches, sharks, sea turtles and dolphins, are referred to as bykill.

Keystone Species and Trophic Cascades

Apex predators often act as keystone species, meaning that they have disproportionately large effects in their natural environments. This makes the removal of sharks particularly concerning. As top predators, many sharks species exert top down influence in their respective food webs. The removal of sharks, and other keystone species increases trophic cascade risks. Trophic cascades are the ecological chain of events triggered by the removal or addition of top predators.

Agriculture, Fishing and Algae Blooms

“Livestock operations on land have created more than 500 nitrogen flooded dead zones around the world in our oceans…” According to Dr. Richard Oppenlander, an environmental researcher featured in the Cowspiracy film. Water pollution comes in the form of pesticides, herbicides, heavy metals, plastics and other waste material. However, animal agriculture is the leading cause of ocean pollution – a fact which is stated explicitly in the Cowspiracy film.

Animal agriculture run-off upsets nutrient balances in aquatic ecosystems by introducing phosphorus, nitrogen, manure and potassium from chemical fertilizers. These excess nutrients can cause alae blooms, leading to uninhabitable zones for marine species. Blooms of algae drain sunlight and deplete oxygen levels – making the environment unsuitable for most other lifeforms in the ecosystem.

Bottom trawling contributes to inhabitable zones similarly. Bottom trawling, also referred to as “dragging” involves casting a fishing net to the sea floor. Trawling disturbs sediments along the sea floor which causes carbon to be released. Once carbon dioxide is released from sediments, it is then absorbed by ocean seawater. Elevated carbon levels allow water to trap in more heat and further facilitate algae and plant overgrowth.

Modeling Characterization of the Vertical and Temporal Variability of Environmental DNA In the Mesopelagic Ocean

DNA double helix molecule strands
DNA double helix

A new study by researchers, Elizabeth Andruszkiewicz Allan, Michelle H. DiBenedetto, Andone C. Lavery, Annette F. Govindarajan and Weifeng G. Zhang simulates the physical conditions that cause environmental DNA samples to move through the twilight zones.

Their conclusion: environmental conditions like currents, wind, and mixing do not significantly impact the vertical distribution of DNA samples. To be precise, their computer generated model demonstrates that eDNA samples didn’t move beyond a 20 meter range of where it was released into the environment. If this model reflects the actual conditions of marine ecosystems in twilight zones, perhaps changes eDNA concentrations can be used to determine which fish species are present at a sea depth or how long species spend at varying depths. This has groundbreaking implications for tracking marine species travel patterns and migration more generally in aquatic ecosystems.

While some species spend their lives in undisturbed depth range known as the twilight zone, many animals move in and out of it. Species of fish, squid and plankton likely swim in darkness to find food or to keep away from predators. These traveling organisms can potentially carry environmental DNA signatures with them.

Vast populations of unexploited fish and unexplored habitats can be found in twilight zones, also known as disphotic zones or mesopelagic zones, which make these aquatic regions extraordinarily interesting to marine researchers. Environmental DNA may prove useful for learning about organisms that live down in ocean twilight zones and how these species travel. Also, using environmental DNA for sampling can protect the ecological processes and species that inhabit these middle ocean zones.

What Is The Twilight Zone?

The twilight zone is a layer of water depth that is penetrated by significantly less light than what can be found closer to the water’s surface. For this reason, the twilight zone is cold and quite dark, making it unsuitable for most photosynthetic plant species. Twilight zones can be found around the world and are not unique to any specific body of water. According to National Oceanic and Atmospheric Administration, the twilight zone can be found at a depth of about 200 meters to 1000 meters (650 to 3,300 feet) beneath the water’s surface. This layer range is below the water’s photic layer- the sunlit area, and just above the midnight range.


There is still much to learn about the carbon sequestration potential, ecological processes and biological diversity profiles of middle ocean twilight zones. Ecosystems must be protected during sampling missions and disturbed as little as possible. Sampling techniques like trawling, bait camera trapping and other forms capture carry ethical concerns which could hamper further research efforts.

Twilight zones likely provide ecological services to the network of species that migrate in and out of them, and more permanent inhabitants. In order to preserve full ecological function and avoid disturbing species, researchers will have to prioritize more minimally invasive sampling techniques. Sampling approaches that are minimally invasive to species and ecosystems are more likely to win over public approval.

Whales As Ecosystem Engineers

whale tail protruding from ocean's surface

A new study published in Nature sheds light on the roles whales play in marine ecosystems. Researchers used metabolic models to estimate whale feeding volumes. Whale tagging and acoustic acoustic measurements were used to calculate whale prey densities in the Atlantic, Pacific, and Southern Oceans. Their results suggest that previous assessments greatly underestimated baleen whale prey consumption. Further, researchers reason that larger whale populations would add to the “productivity” of marine ecosystems by perpetuating iron recycling.

Prey Consumption and Nutrient Cycling

Baleen whales are the largest carnivorous marine mammals, so naturally, they feed on tremendous amounts of krill, zooplankton and other prey. Krill is turned over in stomachs of whales (Mysticeti). Once krill has been digested, their iron contents are released back out into the aquatic ecosystem where it floats towards the water’s surface due to water pressure. Iron rich excrement yields nutrients for phytoplankton, which are microscopic plants that use photosynthesis to make energy.

Phytoplankton are then consumed by other creatures in the environment, including krill! Krill feed on the phytoplankton that grow using the nutrients from recycled metabolized – recycled – krill. In other words, baleen whales populations perpetuate nutrient cycling. At one level, krill are consumed by whales. Subsequently, whale waste supplements phytoplankton growth, which helps sustains krill populations.

By comparing the prey consumption more than 300 tracked whales in this new study to per-capita consumption estimates from the early 20th century, researchers were able to reason that southern krill populations has to be considerably higher than they are today. Whales were found to eat up to three times more krill and other prey than previous assessments have supposed.

Researchers were able to determine how much whales eat by tagging individual whales by attaching electronic devices on their backs. These electronic devices carry cameras, microphones and of course, GPS locators. These electronic tags, in conjunction with acoustic measurements of prey biomass, informed researchers on whale eating cycles and intake volume. Of course, prey intake varies between different species of whale.

The Krill Paradox

The almost infamous krill paradox refers to the mystery in marine ecosystems regarding the removal of large predators, like whales. When whales are hunted, and their populations consequently decrease, so do the population sizes of krill. This perplexes researchers because they intuitively expect krill populations to grow wildly in the absence of whales which eats thousands of tons of krill daily. Instead, the opposite is true: as whales are removed from the ecological system, krill populations shrink. The new study illuminates exactly why this phenomenon occurs. Krill depend on whales to produce nutrients for the microscopic plants that they eat. Declines in whale species members leads to fewer iron being sent toward the water’s surface in the form of whale excrement. Which ultimately contributes to less plentiful meals available for krill populations.

Implications For Restoration

The conclusions of this study may have potential for marine ecosystem restoration efforts. Conserving or enhancing marine ecosystems will not only demand limits on whale hunting, but also for the deliberate effort of whales, and likely other influential species. Species like whales are evidently essential for the continued functionality of the ecosystem that they are enveloped in.