New England’s Corals

When most of us think of coral, we picture a scene not unlike that found in Pixar’s Finding Nemo: a vast multicolored reef in the warm shallow waters of the tropics, inhabited by a multitude of equally colorful fish. But did you know that many intricate and colorful species of coral can be found right here in our own New England waters? Growing along the ridges of underwater canyons and seamounts off the Atlantic coast, the New England version of a tropical reef plays host to our own aquatic flora and fauna, more suited to the chilly waters of the northwest Atlantic.

Though they resemble undersea plants, corals are in fact colonies of tiny, soft-bodied invertebrates whose secreted exoskeletons form, over time, the large and intricate structures that we recognize as coral. In the warm waters of the tropics, groups of these exoskeletoned colonies form extensive reefs in the clear, shallow waters close to the shore.

Though snorkelers may appreciate the clear waters of the tropics, the water is so clear in these areas because it contains few nutrients or plankton. Very little mixing of the water column occurs in these uniformly warm waters, so nutrients remain trapped on the bottom of the sea, preventing the multiplication of plankton, and leaving the water empty of food. As a result, tropical corals get their nutrients through a symbiotic relationship with photosynthetic algae, which grows inside the coral and lends it energy from the sun.  Large animals like whales, however, are unable to sustain themselves by hosting algae. Instead, whales like humpbacks and right whales breed in tropical waters but return to New England to feed in the summer. The constantly mixing warm and cold waters of New England bring nutrients to the surface, encouraging plankton growth, and are thus a veritable soup of life. New England corals enjoy this soup just as much as the whales do, and most of them filter feed instead of relying on algae to do the work for them.

A striking purple coral, Clavularia sp., seen in Nygren Canyon. Image via NOAA/Okeanos Explorer
A striking purple coral, Clavularia sp., seen in Nygren Canyon. Image via NOAA/Okeanos Explorer

New England corals live not in the near-shore shallows but along underwater canyons and seamounts. Last summer, NOAA’s Okeanos mission documented some of the wide array of marine life in the Northeast’s canyons, including Oceanographer Canyon, a deep underwater channel that cuts into the southern edge of Georges Bank. You can see images and video from the mission here. The seamounts are part of the New England Seamount Chain and often rise to within 100 feet of the ocean surface, ensuring a rich habitat for undersea creatures due to the high concentration of particulates in the water and the nearness of sunlight.

Unfortunately, cold water corals grow slowly and are very susceptible to the effects of trawling, which is why Fishery Management Councils along the east coast have begun to take action to protect areas like canyons and seamounts with rich deep-sea coral populations.

New England’s corals are surrounded by towering kelp forests, fish and mammals of all kinds, and even sea turtles. So if you’ve ever wanted to dive the Great Barrier Reef, but balked at the idea of that plane ticket to Australia, consider exploring the underwater scenery right in our own backyard!

Feature Image via NOAA/Okeanos Explorer

Ocean Plants Part 3: Kelp and Climate

Many NEOO readers may have come across a description of the relationship between sea otters, sea urchins, and kelp in a biology textbook. A quick recap: sea otters prey on sea urchins, which live in kelp beds and which, in turn, prey on the kelp itself. Sea otter predation, then, protects kelp from predation and allows kelp forests to flourish. Fewer of us are likely to have heard of the Atlantic wolffish, but this snaggle-toothed New England native plays the same role here that the sea otter does in the Pacific: keeping the urchin population down and the kelp population up. Of course, this is good news for kelp, but is it good news for us as well?

The answer is a resounding yes. Kelp provides essential habitat for countless marine species, including commercially important fish. Furthermore, scientific evidence suggests that kelp forests, like their terrestrial equivalents, play an important role in carbon sequestration.

Plants take in and store CO2 as part of the process of photosynthesis. Some of the carbon stored in plants is soon released when the plant decomposes, but some is sequestered in carbon sinks. Forests, swamps, and especially the ocean are all important carbon sinks. Kelp, boasting both a high uptake of atmospheric CO2 and an ocean floor habitat, is a particularly important player in carbon sequestration, and this role is becoming even more important in the face of rising atmospheric carbon dioxide levels and anthropogenic climate change.

New England is home to abundant and diverse kelp forests, notably at Cashes Ledge, where forests of towering laminarian and perforated shotgun kelp grow thickly on the undersea mountain slopes, sheltering abundant fauna including whales, seals, sharks, and commercially important fish such as the Atlantic cod. Detritus from this kelp forest tumbles off the ledge into the neighboring basin, where these nutrients are recycled back into the ecosystem and fuel incredible productivity. Kelp forests like the one at Cashes Ledge may be a critical component of our oceans’ ability to mitigate and adapt to climate change and ocean acidification caused by rising atmospheric carbon dioxide.

Urchins have taken over this kelp bed off Tasmania. Image via NASA.
Urchins have taken over this kelp bed off Tasmania. Image via NASA.

The loss of an apex predator such as the Atlantic wolffish, and a subsequent increase in herbivores (urchins, in this case), leading to a decrease in carbon sequestering plants such as kelp is a well-known effect called a trophic cascade. We can speed such trophic cascades along, in this case either by reducing Atlantic wolfish populations through bycatch and habitat destruction, or by skipping this step altogether and decimating kelp forests through destructive fishing practices such as bottom trawling. Unfortunately, we’ve done just that—Atlantic wolffish are severely depleted, and the kelp forest at Cashes Ledge is threatened by a New England Fishery Management Council proposal that would reopen 75 percent of the area surrounding the kelp forest to commercial fishing (this area has been protected since 2002).

The news that apex predators such as the Atlantic wolfish can help preserve healthy populations of kelp, and that kelp in particular is a highly efficient carbon sequestering plant, tells us two things. First, while the Atlantic wolffish alone may not have much impact on overall climate change mitigation, protecting important predators like the wolffish will build resilience for our ecosystems in more ways than we can count. Second, we New Englanders should support habitat protection and responsible fishing practices that allow our kelp forests to continue flourishing. In doing so, we will promote carbon sequestration and provide habitat for countless fish—including the Atlantic wolffish, that friend of the kelp. After all, in the end, all ecosystems are cyclical.

Ocean Plants Part 2: Eelgrass

Marine plants are the unsung heroes of ocean habitats, providing food, shelter, and substrate to the varied and wonderful animals we love to watch, photograph, or hook on the end of a line. One such plant, eelgrass, or Zostera marina, grows on sandy substrates or in estuaries along the coast and in the sounds of New England. Growing together in long green ribbons, a bed of eelgrass resembles an underwater meadow, swaying in the current.

Eelgrass serves a greater purpose than its beauty, however. Eelgrass beds aid sediment deposition and stabilize the substrate, preventing erosion. They also serve as a home and nursery for both micro-invertebrates and economically important fish and shellfish; a recent NOAA report on the importance of shallow water bottom habitat identified eelgrass as important habitat for juvenile cod, pollock, flounder, and hake, among other species. Eelgrass is also a major food source for several species of marine birds and waterfowl, including brants, redheads, widgeons, black ducks, and Canada geese, and for the endangered green sea turtle.

 

Eelgrass provides essential habitat for numerous fish species. Image via NOAA.
Eelgrass provides essential habitat for numerous fish species. Image via NOAA.

 

Although eelgrass is found throughout the Northern Hemisphere, this essential marine plant is in danger of disappearing from much of its habitat. Several factors are contributing to the decline of eelgrass. Pollution from sewage and fertilizers is a major culprit—it creates an excess of nitrogen in the water, causing algal blooms that block sunlight from reaching the eelgrass and preventing its photosynthesis. Invasive green crabs also harm eelgrass beds by dislodging and shredding stalks of grass as they dig for softshell clams, and green crab populations are growing rapidly in New England. Shellfish rakes, dredges, and boat anchors also destroy eelgrass. In the future, eelgrass faces increased stress from rising ocean temperatures and water levels.

As a result, eelgrass is disappearing rapidly from many of the places it used to thrive, in turn endangering the myriad species that rely on eelgrass for food and shelter, and leading to sediment pollution due to the loss of this important anchor for the marine substrate. Narragansett Bay is one example—once filled with eelgrass, today it has lost 90% of its eelgrass beds.

Yet all hope may not be lost. Since 2001, volunteers and divers working through Save the Bay have participated in eelgrass transplanting efforts. Eelgrass is harvested from healthy beds in the southern end of Narragansett Bay, sorted, and then hand planted by divers, who attach shoots of eelgrass to bamboo skewers and secure the sewers in the substrate. While some of the transplanted beds have failed, others have flourished and spread.

Similar restoration projects are underway in other locations, including Boston Harbor. Efforts to map the current and historical distribution of eelgrass beds are also ongoing in several states and will provide a valuable baseline for future restoration and conservation.

If efforts to mitigate the stresses on eelgrass and restore its original range continue, there is hope for this marine hero—and the abundance of life it supports—to thrive once more.

Feature image via NOAA

The Sharks of Cashes Ledge

When most of us imagine a shark, we picture something along the lines of Jaws’ famous antihero: a massive, blunt-nosed, white bellied monster: a great white shark. But great whites constitute only a tiny percentage of the world’s sharks, and New England has some incredible habitat for many of the other species that swim our seas. For example, out on Cashes Ledge—an underwater mountain range 80 miles off the New England coast that harbors some of the most incredible habitat in the Gulf of Maine—you might come across multiple fascinating species, among them the blue shark and the porbeagle shark.

The blue shark, a slender, blue-hued fish measuring up to 12.5 feet in length, often swims in schools organized by sex and size. This habit, along with the sharks’ tendency to use their schools as “packs” to heard prey into a concentrated group for easy feeding, has earned blue sharks the nickname “wolves of the sea”.

Blue sharks migrate up and down the Americas’ Atlantic coast, and may travel all the way from New England to South America in a migration year. They prefer cooler waters, however, and so are more likely to be spotted by divers in the colder north, because in these temperate waters blue sharks are more willing to approach shore. Blue sharks prefer water between 45 and 61 degrees Fahrenheit, and as New Englanders will ruefully agree, that makes them right at home here.

Squid constitutes a large part of the blue shark diet, but the sharks are not choosy, and hunt octopus, cuttlefish, bony fish, lobster, and even sea birds. Some blue sharks have been observed snatching cod from trawl nets. The sharks themselves are sometimes hunted by orca whales—coincidentally also nicknamed “wolves of the sea”—but their primary predators are humans. An estimated 20 million blue sharks are caught each year, both as bycatch in commercial fisheries and as a directly targeted species by commercial fishermen and sport fishermen. The blue shark is currently listed as “Near Threatened”  by the IUCN Red List of Threatened Species.

A porbeagle shark. Image via Wikimedia Commons.
A porbeagle shark. Image via Wikimedia Commons.

Porbeagle sharks boast both a memorable name and impressive lifespan: around 65 years, which is more than triple the estimated lifespan of the blue shark. Shorter and bulkier than blue sharks, porbeagles have dark grey bodies, white underbellies, and rounded heads. They grow to around 11.5 feet and weigh about 300 pounds at maturity. Porbeagles are also migratory sharks adapted to cool waters, but they stay farther north and closer inshore than blue sharks do, feeding off the Canadian coast and migrating south to the Sargasso Sea to breed. They rarely swim more than 200 meters deep, yet, sadly, divers are unlikely to come across them—the IUCN Red List classifies porbeagles as endangered in the northwest Atlantic.

Due to its unique and productive landscape, a decade of protection from underwater trawling, and its location along the sharks’ migratory route, Cashes Ledge provides a perfect refuge for these incredible but threatened sharks. Divers admiring the kelp forests, anemone beds and schools of rare and threatened fish might be lucky enough to spot a pack of sleek blue wolves of the sea or a dark gray porbeagle as the sharks pause in their coastal migration at this sanctuary in the sea.

Striped Bass and Forage Fish

As the summer heats up along Atlantic coast, coastal residents and visitors alike head out in boats, stake out spots on docks and bridges, or don rubber waders and forge into the waves along a beach’s breakwater. Each is armed with a long pole and a zeal for the chase. Their quarry is the striped bass, a silvery fish with trademark dark stripes running the length of its body from head to tail. The striped bass, or striper, is an anadromous fish native to the Atlantic coast of North America, and usually grows to around three and half feet. The historic abundance of the striped bass, as well as its ideal size for recreational fishing, makes it a highly valued sport fishing species. In 2004, recreational fishermen landed more than 2.5 million stripers.

Unfortunately, recent evidence indicates that this time-honored recreational fishery may be in danger of collapse. Recreational fishermen in Massachusetts reported a staggering 85% drop in striper numbers between 2006 and 2011, and Massachusetts is not alone: states up and down the coast are seeing fewer stripers, and the schools of bass that migrate up the coast from the Chesapeake Bay to Maine are thinning out. More and more fishermen are heading home empty-handed at the end of the day, and more importantly, the disappearance of the striped bass leaves a lack of an important member of the marine ecosystem and food web.

Image credit: Timothy Knepp/Wikimedia Commons
Image credit: Timothy Knepp/Wikimedia Commons

Many factors are responsible for the decline of the striper, but one is often overlooked: food. Small forage fish, including Atlantic herring and river herring, compose around 90% of the striped bass diet, and these forage fish face the pressure of a significant fishery of their own. While ignored by recreational fishermen, Atlantic herring are heavily fished by commercial fishermen, largely for use as bait in the lobster industry. In 2011, for instance, U.S. commercial fishermen harvested over 174.3 million pounds of Atlantic herring.

Recent assessments indicate that Atlantic herring are not overfished, but surveys of population levels and safe catch limits rarely take proper account of the amount of a forage fish required to feed its predator species. As a result, after the herring fishery has hauled in its 170 million pounds of fish, there may not be enough herring left to both maintain a steady herring population and provide the striped bass with sufficient prey.

River herring, meanwhile, have been depleted by years of overfishing and habitat loss due to dams. Total landings of commercially fished river herring have decreased steeply over the years: in the 1950s, over 60 million pounds of river herring were harvested by commercial fisheries throughout the US, but this number had decreased to around 2 million pounds by 2012. In response to this decline, many states have implemented moratoriums on intentional catch of river herring and have made strong efforts to remove dams and restore upstream habitat; river herring runs in many New England rivers seem to be on the rebound. But river herring are still at risk at sea, where they are caught as bycatch by the Atlantic herring and mackerel fisheries.

This scarcity of prey spells danger for the striped bass. Without sufficient forage fish, there will be fewer striped bass in the sea, and more fishermen with empty hooks.

New England’s Unexpected Summer Visitors

Pure-white, Arctic-dwelling beluga whales and their black and white cousins the orcas are rarely seen in the Atlantic outside of icy polar waters.  While orcas migrate around the globe and inhabit both Arctic and Antarctic waters, belugas are usually at home only in the frozen north. Massachusetts residents, then, are unlikely to ever see these whales, but this month prospective whale watchers might get lucky. Just a few days ago, both whales were spotted in Massachusetts—quite a distance south from the whales’ usual frigid habitat.

On June 15th, a lone beluga was seen in the mouth of the Taunton River in Fall River, Massachusetts. The sighting was rare for two reasons: first for its distance from the arctic and second because belugas usually travel in pods and are rarely seen alone. This beluga, however, which appeared to be a healthy adult male, cruised around solo in the river for several days, delighting the citizens of Fall River but worrying advocates concerned for the whale’s safety. Meanwhile, on June 25th, the U.S. Coast Guard came across a pod of orcas about 150 miles off the coast of Nantucket. The picture below shows the orcas surfacing beside the CGC Campbell.

A pod of orcas seen from the CGC Campbell. Image: USCG
A pod of orcas seen from the CGC Campbell. Image: USCG

Scientists have been both pleased and puzzled by the unexpected appearances. While the sighting of such rare visitors to New England is certainly exciting, there may be an unfortunate reason for these whales’ presence here. Researchers from Mystic Aquarium suspect that both the beluga’s and the orcas’ movements may be an indication of melting Arctic ice and of the impact this environmental change has on the Arctic’s inhabitants—the whales may have been driven south in search of more abundant food. These aren’t the first polar visitors to New England this year, either—a bowhead whale was spotted in April off the coast of Cape Cod.

The verdict is still out, however, on what the connection is between melting ice and wandering whales. In the meantime, we can enjoy the rare sight of these beautiful creatures.

Feature image via USCG