Sharing the shore - The sharks on Cape Cod

A great white shark. Photo Credit Terry Goss on Wikipedia.

For the first time in over 80 years, someone has died from a shark attack on Cape Cod. It's a terrible tragedy, and one that will have people nervous to dip their toes in the water. As we have heard about great white sharks returning to the Cape in greater numbers than before, the area has had to decide what it means for tourism, for humans, for the environment, and for the future. With the return of sharks, we have seen a rejuvenating ecosystem, a snippet of the ocean returning to a healthy balance it is designed to have. People can bemoan the return of the sharks, but we know exactly why they have returned to the Cape: seals.

Right now grey and harbor seals are thriving on Cape Cod, but there was a time when the species' future was threatened in New England. The seals used to be routinely hunted, with a bounty even offered in Massachusetts of $5 per seal. They were seen as a nuisance, stealing fishermen's catch and taking up beach space. This, however, all ended with the Marine Mammal Protection Act in 1972. While it has been difficult to estimate exactly how many seals are now in New England, the numbers have clearly increased, and the grey seal population in Nova Scotia, which can spill into New England, is reported to have grown "exponentially." In New England, the seal population may have tripled. This is great news! It is a tale of protection enabling recovery of a species at a time when so many animals are struggling. It also means a boost in the economy for those in the tourist industry. Seals are a crowd pleaser, and boats that offer seal watching have been selling out. Since animal populations are often linked to others, however, the recovering seal population has helped other animals recover. Enter the great white shark.

A grey seal pup. Photo credit Alastair Ray on Wikimedia Commons.

A seal is a perfect meal for a great white. It's thick layer of blubber, meant to keep it warm, is a fat delicious meal for a shark. With increasing numbers of seals, more sharks can eat and survive, and that is what we are seeing happening on the Cape. Regardless of the seal's protected status, it's one of the reasons tourists are encouraged to stay away from seals and not swim with them. Swimming with a seal puts you in a shark's version of a buffet. It won't be looking for you, but it could find you anyway.

According to the Cape Cod Commission, about 5.23 million tourists visit the Cape annually, with 65% showing up in the summer months. That's about 3.4 million people coming to the Cape every summer. Presumably, a large number of them visit the beach at least once. This is the first fatal attack in 82 years, meaning the odds of dying from a shark on the Cape are insanely low. Chances are, however, these kinds of numbers won't alleviate the fear people feel when they hear about a shark attack. We hear that traveling by plane is one of the safest methods of travel, and yet many of us still get queasy when we are up in the air.

Seal sunbathing on South Monomoy Island. Photo credit Keith Shannon from
the US Fish and Wildlife Service on Wikimedia Commons.

Right now, we are seeing the results of our actions. Years ago, we decided to make an investment in protecting the ocean by protecting seals. This action has been incredibly successful. The fact that not only the seals have increased but that sharks have increased is a sign that the ecosystem is returning to a healthy balance. With the exception of us humans, great white sharks are at the top of the food web. The fact that the ecosystem can support sharks shows a kind of robustness that is good news for the smaller species involved as well, the kind that we may be fishing and eating. But what it does mean is that we have to be conscious about sharing the ocean. We can decide where to swim and how to do it, but sharks have no choice but to be in the sea.

The good news is that there are people actively having this discussion every day and working with local people and businesses to find the best way to share the shore. The Atlantic White Shark Conservancy focus on sharks specifically in New England, while OCEARCH tags sharks and tracks them around the world. They even create Twitter accounts for some of their sharks like Hilton, keeping people up to date on the interesting places the sharks swim to. It's an important reminder that while we only hear about sharks when there is an attack, most of a shark's life has no direct human interaction.

If you are still concerned, here are some things to keep in mind the next time you visit the seashore:

1. Never swim where you see seals.
2. Stay closer to shore, wading only up to your waste. 
3. Swim in groups.
4. Do not swim at dusk or dawn.
5. In the unlikely event that you see a shark coming toward you, punch it in the nose. Seriously. Their noses are very sensitive and the sharks aren't looking for a fight.
6. Look for signs. At beaches on the Cape where sharks have been spotted, the Atlantic White Shark conservancy posts notices and advice about keeping yourself safe. Follow it.

Did you say shark? Photo Credit Andrew Reding at Flickr.

Most of all though, remember that you are not on a shark's menu. A great white wants a fat, juicy, blubbery seal. Finding you would be a bony and ultimately unsatisfying mistake for the shark. Most shark bites are simply that: a mistake. Ultimately, a shark wants nothing to do with you. With that in mind, try to enjoy the beach.

Wasting away - The mysterious disease killing your favorite sea creatures

The humble sea star, beloved by many, symbol of tide pools, and... victim of a horrific melting disease? Yes. In fact, when it comes to sea stars, truth is stranger than fiction.

Healthy sea star

Here are some of my favorite things about sea stars:

1. They have an eye at the end of each arm. You can actually see it if you look closely enough; it's a tiny little black dot. They don't see like you or I do, but they can sense light. If you close your eyes, turn towards the sun, and then wave your hand in front of your face, you can see the shadow of your hand passing over your eyes. This is a bit like how a sea star sees.
2. Sea stars have to cling to rocks tightly so that they don't get tossed by the waves. In order to do this, they actually create a glue that sticks to the ends of their thousands of tiny feet. They also make a chemical that will dissolve the glue when they want to pick up their feet again. They can make and undo a glue that works underwater at will!
3. Sea stars are voracious when it comes to eating mussels. In fact, they eat so many mussels that if they are removed from an area, mussels take over the rocks so that nothing else can live there. Without sea stars, tide pools fail to exist as we know them.
4. The way that sea stars eat is like something out of a horror movie. When they find a mussel, they wrap their arms around it and pull from all directions until the mussel is too tired to stay closed and opens up. When this happens, the sea star spits its entire stomach outside of its body and digests the mussel inside of its own shell.
5. Because sea stars eat so many mussels, they became early enemies of fishers. To try to get rid of them, fishers would drag them on the boat, cut them in half, and throw them back into the ocean. What they didn't know was that sea stars can regenerate, so by throwing the sea stars back into the water, they had actually managed to make twice as many sea stars!

So what's up with this wasting disease?
If you are a bit queasy, you may want to skip the upcoming pictures. What comes next is disintegration, decay, and ultimately death, but it is the last step to befall the ill-fated sea star that picks up this mysterious condition. On both coasts, sea stars are literally wasting away. One day they are perfectly normal, bumpy, slow moving animals eating mussels to their hearts' content. The next day, there might be a small lesion on the outside of the animal. The following day, it may have lost some of its legs. The following day, all of its legs may be walking around on their own, completely disconnected from the sea star and spilling their insides behind them. Next comes death. The entire sea star can literally fall apart within days, and yet we still don't know why. That's why this phenomenon is called Sea Star Wasting Syndrome (SSWS). A syndrome is a mysterious medical ailment for which we don't have a clear explanation or treatment. This syndrome is no joke either. Researchers examining one species of sea stars in southern California, Pisaster ochraceus, found that, in some of their study sites, 99% of the sea stars died. That is truly astronomical; it's a tiny, local extinction. While the west coast, stretching from Baja California, Mexico to Alaska, has been impacted most by SSWS, sea stars on the east coast of the US can get it as well. 

P. ochraceus with Sea Star Wasting Syndrome. Taken by Alisonleighlilly.

This is not the first time that sea stars have wasted away. There were mass die-offs of sea stars in the 70's, 80's, and 90's, but nothing on this scale had been seen before. The current blight was first discovered in a survey of the sea stars P. ochraceus in Washington state in 2013, although the disease affects many different species of sea stars. For a while, the cause of the disease was completely unknown, but in 2014 a team of scientists proposed that the disease was caused by a densovirus. The interesting thing about the virus is that it could be found in samples of sea stars collected in 1942, suggesting the disease may have been around for decades before this disaster. 

So what changed? One of the leading theories is that temperatures in the ocean got really warm. Warmer temperatures can physically stress animals out, making them more likely to get sick, and ocean temperatures were unusually high in many areas where the outbreak of SSWS was most severe in 2014. Scientists in the lab also saw that adult sea stars in warmer water died faster than sea stars in colder water. In addition, young sea stars were more likely to get sick in warmer water. 

The disease can first appear as lesions, followed by legs that fall off of the main body, leaving gaping wounds. The legs seem to have a mind of their own after, crawling around trailing innards behind them. The central circle of the body may be left, with the legs spreading to the far corners. When the pieces dissolve, all that is left are small, white spines, but not before the decaying arms of the sea stars have left a bitter, rotten smell behind.

However, this doesn't explain everything. One study found that decreasing water temperatures could help sea stars live longer, but it didn't necessarily stop them from getting sick. Another study looking at the original outbreak in 2013 found that water temperatures were not particularly warm when the disease first emerged. Another theory was that if there were a lot of sea stars densely packed together, they would be more likely to get sick, but a lot of the places hit hard by SSWS did not necessarily have a lot of sea stars to begin with. Finally, although SSWS may be caused by the densovirus, there still isn't conclusive evidence that that is the cause. This leaves scientists with a pile of questions and very few certainties on which to build a plan for protecting sea stars.

The arms can dissolve at different rates. This arm was still moving, but you can get a good view of the circulatory system. 

The picture I just painted looks very grim, but there is actually a lot of reason for excitement and optimism. In a recent study, scientists found that the number of new sea stars that survived each year increased 74-fold between 2012 and 2015.  In addition, there seems to be a genetic shift in the population to sea stars that are more resilient and don't get the disease as easily. Basically, the disease killed off sea stars without this genetic resilience, but the sea stars that survived produced new, hardier sea stars. It's a wonderful example of nature adapting. In a time of rapid global change, it is heartening to see some things becoming more resilient as opposed to wasting away.