The goal of Science and the Sea is to convey this understanding of the sea and its myriad life forms to everyone, so that they, too, can fully appreciate this amazing resource.
As a hurricane roars toward the American coastline, residents pay close attention to a single number: the hurricane’s category. Category 1 is dangerous but usually survivable, while category 5 is monstrous -- an Armageddon with effects that can last for months.
The categories come from the Saffir-Simpson hurricane wind scale. It was conceived in 1969 by Herbert Saffir. He was an engineer who was evaluating the impacts of tropical storms for the United Nations. He showed it to Robert Homer Simpson, Director of the National Hurricane Center, who’d survived a major hurricane in Corpus Christi, Texas, as a child.
Saffir based the scale on wind speeds. Simpson added storm surges and other effects, then began using the scale in 1973. Decades later, the other effects were dropped, so today the scale once again is based on wind speeds alone.
Category 1 begins with winds of 74 miles per hour. They can cause a lot of damage, but the extent and clean-up are fairly minor. Beginning with category 3, at 111 miles per hour, hurricanes are classified as “major.” And the strongest hurricanes, category 5, start at 157 miles per hour. They’re described as “catastrophic,” with near-total destruction.
Not many hurricanes hit the coast at category 5. And most of the ones that do quickly drop to lower levels -- still-deadly storms high on the Saffir-Simpson scale.
Parrotfish and surgeonfish are among the many colorful residents of Caribbean coral reefs. They mainly eat algae and a type of bacteria off the reef. But they also nibble on other things, including sponges and the living coral. And one item that may be an important part of their diet is decidedly unappetizing: the poo of other fish.
Researchers studied these fish in the waters around an island near Venezuela, in 2019. They followed nine species of parrotfish and three species of surgeonfish. And they paid careful attention to what the fish ate.
They found that one food source was the poo from a smaller fish. Known as Brown Chromis, the fish eats organisms known as plankton near the surface. It then poops out small pellets, which drift toward the bottom. The researchers followed the pellets and found that about 85 percent of them were gobbled up on the way down.
Parrotfish and surgeonfish consumed almost all of these pellets. There were differences between individual species, but most species ate at least some of the pellets.
The scientists grabbed some of the pellets as well. Their analysis showed that the poo was highly nutritious. It contained lots of proteins and carbohydrates, plus important nutrients such as iron and phosphorous. So the fish poo may act as a fish “multi-vitamin.”
Coral reefs offer limited nutrients, but this study suggests that fish eating the poo of other fish may be an important way to recycle nutrients on the reefs.
Rising from the Dead
A type of ray has come back from the dead -- or at least the mostly dead. The tentacled butterfly ray inhabited the waters along the northern Indian Ocean, from Arabia to India. But it hadn’t been seen since 1986, near Pakistan. So it was listed as critically endangered and possibly extinct.
The tentacled butterfly ray is one of about a dozen species of butterfly rays. The rays can be up to about 12 feet wide. They have long, thin “wings” that make them look like butterflies. They live near the ocean floor, mainly in open, sandy areas, where they eat fish, shellfish, and other bottom dwellers.
In late 2019, researchers found a tentacled butterfly ray in the nets of a trawler off the coast of Iran. The ray had died before it reached the surface. But over the following year, they found 367 more -- most of them still alive -- in the Gulf of Oman and the Persian Gulf, between Iran and the Arabian Peninsula. In fact, the ray accounted for about 15 percent of all the rays that were trapped in the nets.
That doesn’t mean the rays aren’t still in danger, though. The research showed that they’re easily caught by trawling, and many of them die. Fishing fleets might need to install devices that let the rays and other unintended creatures escape while keeping the target catch inside. That way, the tentacled butterfly ray might still be endangered, but at least it would avoid disappearing once again -- only this time, for keeps.
A “conveyor belt” in the Atlantic Ocean appears to be slowing down. And that could have a big impact on the climate, although it’s not clear just what that impact might be.
The conveyor belt is the Atlantic meridional overturning circulation -- AMOC for short. Water at the surface travels northward, parallel to the American coastline, then curls over to Europe. As it reaches higher latitudes, the water gets cooler and denser, so the current sinks. It swings around and moves southward, on the opposite side of the Atlantic. Eventually, it’s brought to the surface, where it warms up again.
Scientists have been tracking the AMOC only since 2004. But they can get a rough idea of what happened before then by sampling ocean sediments and making other measurements. And a recent study found that the current has weakened dramatically over the past thousand years -- especially since the mid 1900s. That’s probably a result of our warming climate.
Scientists expect the trend to continue. And the AMOC could even shut down entirely. Today, the current helps keep the climate in Europe fairly mild. As it weakens, though, the continent could see more severe winters and bigger storms.
One study says the United States could see more severe winters as well. On the other hand, another study says hurricanes on the Atlantic coast might get weaker. But scientists need to know more before they can tell us just what will happen as this giant conveyor belt slows down.
The North Atlantic Ocean is home to a rich diversity of life beneath the waves. But it’s also home to a rich diversity above the waves: seabirds. There are so many birds that scientists managed to have a patch of the ocean declared a marine protected area.
The birds inhabit a region that’s almost as big as Texas. It’s south of Greenland, from near the shore of Canada to the middle of the Atlantic.
The first hints that it was a popular spot for birds popped up in 2016. A team of researchers looked at several earlier studies that tracked bird migrations. The studies showed that many of the birds settled in the North Atlantic for periods of days to months. Later studies found even more birds putting down stakes there.
In all, the studies recorded 21 species of birds. And as many as five million birds could settle there every year. Some travel a long way to get there: Some shearwaters come thousands of miles -- all the way from the South Atlantic.
The birds may pick that spot because it’s where the warm water of the Gulf Stream intersects with colder waters. That region could provide good conditions for the fish and other organisms the birds eat.
Even though the region is far from land, the birds still face dangers -- from fishing fleets, pollution, climate change, and other sources. So scientists are trying to get some international protection. But that won’t be easy to do -- so the region could see fewer birds in the decades ahead.
During the Irish potato famines of the 19th century, many people survived by eating limpets -- small animals that cling to rocks at the ocean’s edge. And when German troops occupied the island of Jersey during World War II, its people survived on a stew of limpets and curry powder. So limpets became known as “famine food” -- something to eat when there wasn’t much else.
Yet a recent study notes that limpets have been an important food source for thousands of years. In fact, the earliest record of humans eating limpets is a 164,000-year-old cave painting in Africa.
Limpets are marine snails. They’re found on rocky coastlines around the world. They look like little cone-shaped mountains, two or three inches across.
When the tide comes in, the limpet crawls along the rock, using several rows of teeth -- made of the strongest material found in any living organism -- to scrape algae off the surface. When the tide rolls out, the limpet follows its own trail back to its original spot. There, it seals itself to the rock so it doesn’t dry out.
By looking at the trash piles of prehistoric coastal villages, archaeologists have found that some villages consumed more limpets than any other shellfish. And limpets also were popular with the ancient Greeks, Romans, and other cultures.
Today, the limpet is ignored in some places and craved in others. And in some, it’s so popular that it’s almost completely vanished -- feast or famine for this tough little rock hugger.