Microplastics are raining down on national parks and other protected areas in the western United States at the rate of about 132 pieces of microplastic per square meter every day, according to a report in the journal Science (June 2020). Microplastics are plastic particles measuring less than five millimeters (approximately 0.2 inches) in length. The reported precipitation rate is similar to dumping about 300 million pulverized plastic water bottles (about 1000 tons) over the studied areas each year. Where do these particles come from? Sources mostly include fragments from virgin plastic pellets, polymer textile fibers, microbeads from personal care products and spray paints, as well as environmental degradation of waste plastic into smaller and smaller pieces over time. See also: Manufactured fiber; Paint and coatings; Plastic waste pollution; Polymer; Textile

The world’s oceans and coasts provide a natural sink for excess carbon in the atmosphere. Scientists refer to carbon that is captured and stored this way as blue carbon. Well-known blue-carbon examples include mangroves and salt marshes—wetland ecosystems in which the soils may store carbon for thousands of years. An often-overlooked source of blue carbon, however, is large fish living in the open ocean, according to marine scientists reporting in the journal Science Advances (October 2020). Large fish are classified as being longer than 30 centimeters (12 inches) in length, and include such species as tunas, mackerels, sharks, and billfishes. See also: Carbon; Chondrichthyes; Mackerel; Mangrove; Salt marsh; Soil; Perciformes; Pisces (zoology); Tuna; Wetland

Crown-of-thorns starfish or sea stars (Acanthaster planci; order Valvatida) are predatory marine invertebrates that feed on phytoplankton found on coral. They are native inhabitants of coral reefs in both the Indian Ocean and Pacific Ocean and are particularly common on the Great Barrier Reef, which is the largest living structure in the world, covering an area of more than 340,000 km² (131,000 mi²) off the northeast coast of Australia. Lately, crown-of-thorns sea stars are exploding in numbers, offsetting the ecosystem balance found in the waters of the Great Barrier Reef and causing marine investigators to fear severe degradation of the coral reefs, which are already under pressure from coral bleaching (the response of corals to environmental stress in which they eject the algae that live within the transparent coral tissue, making the white coral skeleton visible) and other effects of rising sea temperatures. See also: Asteroidea; Australia; Coral bleaching; Coral reef complexity; Ecological communities; Ecosystem; Marine ecology; Ocean warming; Reef; Severe coral bleaching endangers Great Barrier Reef; Valvatida

For nearly 50 years, marine chemists have generally accepted that when microscopic organic compounds in seawater, known as dissolved organic carbon (DOC), sank into the deep ocean below 1000 m in depth, they became resistant to microbial degradation (recalcitrant). Once in the deep ocean, DOC can remain there for hundreds or even thousands of years. As a result, while most organic carbon cycles rapidly through nature, DOC in the deep ocean accumulates and only slowly is recycled to living things, the soil, and the air. Why this deep-ocean DOC is so stable has been uncertain, but it seemed possible that marine microorganisms could not metabolize the chemical structures of the DOC. The observation led some scientists to propose methods for mitigating global warming by sequestering carbon as DOC in the deep ocean. However, recent research indicates that such efforts might not be very helpful. See also: Biogeochemistry; Ecosystem; Global warming; Marine ecology; Marine microbiology; Marine sediments; Ocean; Seawater

Sunscreens are polluting the ocean, and increasing evidence points toward some ultraviolet-light–absorbing chemicals found in sunscreens as being harmful to marine life—particularly corals at popular tourist destinations. While working toward finding environmentally friendlier sunscreens, researchers have found that certain marine organisms produce protective UV-absorbing chemicals, called mycosporine-like amino acids (MAAs). MAAs are colorless, water-soluble compounds with relatively low molecular weight and are found in cyanobacteria, marine algae, and corals. They absorb UV light strongly from 310 to 365 nanometers (nm). One such source of MAAs is the red algae, Porphyra umbilicalis, commonly known as nori, the edible sushi wrap. See also: Algae; Amino acid; Cyanobacteria; Reef; Water pollution

The Antarctic ice sheet is the largest remnant of previous ice-age glaciations. Glaciers flow out from this ice sheet and feed into floating ice shelves along one-third of the Antarctic coastline. One of the largest ice shelves is the Filchner-Ronne Ice Shelf, located on the southeastern edge of Antarctica's Weddell Sea and covering more than 415,000 square kilometers (160,000 square miles). During an exploratory borehole survey undertaken in 2017 to collect seafloor sediment samples, geologists made an unusual discovery. After drilling through the 900-meter-thick (2950-foot-thick) ice shelf, the scientists lowered a sediment coring device with an attached video camera through the borehole and then down another 490 meters (1600 feet) of seawater, hoping to reach the seabed mud below the ice shelf. However, instead of hitting the seafloor, the coring device struck a large boulder. Subsequent video footage revealed that the boulder was covered by numerous sessile (stationary) marine species, including sponges (both stalked and nonstalked types) and other likely filter-feeding invertebrates. See also: Antarctic Ocean; Antarctica; Deep-sea fauna; Glaciology; Marine sediments; Porifera; Sea ice

Perhaps the most mysterious and sought-after of all ocean creatures, the giant squid Architeuthis dux was finally captured on video in its natural habitat in July 2012 during an expedition off the coast of the Ogasawara archipelago of Japan. The expedition was sponsored by the Japan Broadcasting Commission (NHK) and by the U.S. Discovery Channel.

A regional or local tsunami warning system that uses both seismic and GPS stations could broadcast more prompt and accurate tsunami warnings and could potentially reduce casualties in the event of a major earthquake, according to a report in Geophysical Research Letters (February 2016). The warning system would not require any new instrumentation, as it would use instruments already deployed. See also: Earthquake; Satellite navigation systems; Seismic risk; Tsunami

In a rare winter occurrence, a North Atlantic hurricane, named Alex, attained Category 1 strength on the Saffir-Simpson hurricane wind scale in January 2016. Alex is only the second Atlantic hurricane known to have formed in the month of January. The first was an unnamed storm in 1938. Most Atlantic hurricanes occur during their official season from June 1 to November 30. See also: Atlantic Ocean; Cyclone; Hurricane; Tropical meteorology; Wind

Hurricane Harvey made landfall near the middle of the Texas Gulf Coast on August 25, 2017 as a Category 4 storm on the Saffir-Simpson Hurricane Wind Scale and essentially hovered over the region for seven days, unleashing heavy rain and causing catastrophic flooding. To call Harvey an extreme weather event would be an understatement. It was a monster storm stuck between two high-pressure systems and moving slower than 3.2 kilometers per hour (2 miles per hour). On August 31, Harvey started advancing northeastward and was downgraded to a tropical depression. See also: Air pressure; Cyclone; Extreme weather events; Gulf of Mexico; Hurricane; Tropical meteorology