In the late 1800s, the height of  luxury was a ship like the PS Portland.

She had mahogany furniture, plush velvet,  and comfortable staterooms to provide an   unforgettable journey between Boston and Portland. The ship was a large, wooden paddle  steamer that could transport up to   700 passengers on this eight hour journey.

But on the night of November 26, 1898  a massive storm ripped across her path. Huge waves up to 9 meters high  washed across the boat’s deck,   tipping it to the side and straining the  drive mechanism to the point of breaking. That night, all 192 passengers  and crew lost their lives.

Bodies and ship wreckage washed up  on the shores of Cape Cod for months. It was a tragedy. But the PS Portland’s story doesn’t end there.

Scientists would study it for decades,   and it would reveal secrets about the strange  afterlife of a ship at the bottom of the ocean. [♪ INTRO] On that evening in 1898, the PS Portland became   one of over 200 shipwrecks now in The  Gloucester Basin of Massachusetts Bay. The Portland rests in what’s now  a marine protected area known as   the Stellwagen Bank National Marine Sanctuary. It was designated as a sanctuary partially because   the shipwrecks here kind of act as  time capsules for maritime history.

Plus, these shipwrecks have turned out to  be great resources for studying what happens   after a ship sinks, and the impacts that  wrecks have on the local marine ecosystem. Studies about the Portland, specifically,   started with a 2002 to 2005 baseline survey,  with follow-up surveys in 2019 and 2020. The studies were a collaboration between The Woods   Hole Oceanographic Institution  and Marine Imaging Technologies.

These surveys—together with studies  of other shipwrecks in the bay and   beyond—help us piece together  what happens after a ship sinks. And we’ll start with the sinking itself. The ship’s structure is rapidly changing  as wind and waves tear at the sinking ship.

Obviously some parts are damaged before  the ship even reaches the bottom,   due to collisions or artillery attacks. And researchers know from video  surveys of the Portland that much of   the structure above her deck is missing:  its chimneys, crew area and flagpoles. The next phase depends on where the ship sinks.

The Portland landed on muddy sediment,   likely stirring up a plume of  nutrients settled on the seafloor. That slow-mo mushroom cloud of sediment  can be an absolute feast for bacteria. But a cushy landing in sediment is anticlimactic  compared to, say, landing on rocks or coral.

In those cases, the wreck can disturb or  destroy pieces of an existing ecosystem. Either way, the initial crash  landing might break the ship up more,   or parts might get buried in the sediment. And how deep the shipwreck descends  influences what communities might get   disrupted when it lands, as well  as everything that happens next.

Deeper water, for example, means darker,  colder and different levels of oxygen. That’s important because once the ship has settled  in its final resting place, the decay can begin. Wooden ships, like the Portland, become infested   with marine borers like Limnoria and  shipworm—the real Kraken of the sea.

Shipworm are equipped with rows of sharp teeth and   shells on either side of their  head to scrape away at wood. That means if they have their preferred  environment, with oxygen and relatively warm,   salty water, these little guys can decimate  most of a wooden ship within a couple years! They’re not exactly picky  about their habitat or diet.

Which, by the way, makes them a huge problem not  just for shipwrecks we want to preserve and study   but any ocean-adjacent infrastructure, like  piers, docks or the dikes that protect cities. But borers aren’t the only life  to call shipwrecks home early on. Fungi and bacteria also move in, but  a bit more quietly than the borers.

These microbes start munching from the outside,   and are helped along by swirling sand  and ocean currents that erode the   wood’s texture and create new nooks and  crannies for the microbes to thrive in. The bacteria and fungi do more  than just degrade the wood,   they actually shape it into a new  habitat by creating a biofilm. Inside the biofilm are the  microorganisms themselves,   plus a protective goo they secrete, made  of long chains of sugar-based molecules.

The gooey layer is its own tiny community,   with chemical reactions, nutrient  sharing, and even gene swapping! Some of the non-wood-eating bacteria  that join these biofilm colonies can   even help protect the ship  from eroding away entirely. Now, you might think that metal ships  are immune to these microscopic critters.

But that’s not the case. Consider one of the most famous metal  shipwrecks of all time, the RMS Titanic. After more than 100 years, it’s  now covered in a biofilm of marine   fungi and bacteria that have been  slowly consuming the ship’s metal.

Additional bacteria have joined the party,   perhaps having drifted over  from nearby hydrothermal vents. Using the Titanic’s iron, they’ve formed meter  long rusticles and sprawling rust flowers. Those bacteria are so aggressive that the  rust spreads out from the ship around 4   inches each year and now reaches  6 inches down into the sediment.

This bacteria-built rust art  comes at the cost of around   130 to 200 kilograms of ship iron every day. Large swathes of the Titanic may  be totally dissolved by 2192. But to keep us afloat so that we  don’t go the way of these shipwrecks,   we need to show you a quick ad.

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Even as the flesh of the ship is ripped away,   and its skeleton begins to dissolve, the  shipwreck still has plenty left to give. Because next it becomes a home for bigger  creatures in the form of an artificial reef. The shipwreck provides a scaffold for  all sorts of life, by adding structure   and height to areas that otherwise  would just be muddy, sandy, and flat.

The Portland became something like a  neighbourhood, with different species   moving into different areas of the  ship and establishing new homes. Suspension feeders, like a zooplankton-eating  anemone, occupied the top part of the ship,   taking advantage of currents that  keep the water and food flowing. Larvae, on the other hand,  mostly nestled under the ship,   where they’re protected from being  buried alive in the sandy seafloor,   but also sheltered from currents  that would sweep them away.

The crevices of the midship provided  a perfect home for fish to hide in,   while other fish feed on the furry layer  of algae that coats the wreck’s frame. Species like Atlantic Cod, Acadian redfish, Cusk,   Winter Flounder and Spiny Dogfish, and many more  have all been spotted hanging about the Portland. But as the ship settled and moved over  time, those communities changed, too.

For example, between the 2002-2005 baseline  survey and 2019/2020, researchers saw that   timber and railings had ripped off and fallen to  the seafloor, plus new fishing nets had appeared. Researchers don’t know exactly where those nets  came from, but their appearance might be partly   because of changes in fishing regulations in 2010  and increased scallop fishing starting in 2017. The policies changed, and around the same  time, the biological community changed, too.

On their way down, those new fishing nets probably   scraped off some of the taller  organisms clinging to the ship. It might have missed species  like the breadcrumb sponge   that tucks in flatter to its growing surface. And nets generally mean fewer invertebrates  can find a foothold on the wreck,   since it’s tricky to cling onto  such a flimsy and flailing surface.

Plus researchers noticed fewer suspension  feeders clinging to the top of the ship,   since much of the upper structure  had tumbled to the sea floor. And surfaces that were once horizontal  had shifted to a more vertical position,   which meant deep sea sponges that prefer an  upright surface had been able to move in. The kinds of fish hanging around the Portland  were also different from the ones in 2002,   but researchers couldn’t pin that to any  specific change in the ship’s structure.

It’s more likely the fish were reacting to climate  change, overfishing, or competition in the region. The funny thing about shipwrecks is that  they were never supposed to be there. But by introducing these new  structures to the environment,   they end up functioning like  biological stepping stones.

Basically, a way for species to move  long distances by jumping—or in this   case swimming—between these stepping stone oases. See, once all those algae, fungi,  and fish move into a shipwreck,   the benefits soon start spilling out, like  bounty overflowing from a sunken treasure chest. The effect is a kind of “halo of  life”, as one marine biologist put it,   extending out past the shipwreck itself.

That’s because these habitats don’t  just abruptly end where the shipwreck   does—although it’s obviously more  concentrated on the wreck itself. The habitat gradually fades, creating a transition  zone between the wreck and the empty seafloor. Like suburbs between a city and the country!

If the distance between those  “halos” is small enough,   then organisms can move from one habitat’s  transition zone to another one nearby. No one’s studied whether this stepping  stone effect has happened with The Portland   specifically, but we have observed  the effect around other wrecks. For all their benefits, it’s tricky to say if  shipwrecks are a good or bad thing ecologically.

Corroding metal or toxic fuel leaks can  cause a whole bunch of environmental damage. But there might be quieter downsides, too. Ships might unknowingly transport invasive species  to a new area, like how shipwrecks in the Atlantic   ocean have helped spread invasive sun corals up  to 200 kilometers from their original habitat.

Everywhere these corals set up camp, they  outcompete and then shove out other species. Another potential downside of all this moving  around is that the exciting new habitat of a   shipwreck could attract fish from nearby, leaving  an ecological gap in their former neighborhood. But on the plus side, these shipwrecks provide   a great opportunity for species that  wouldn’t otherwise be able to thrive.

In some cases, they even  become biodiversity hotspots. The Portland’s afterlife is just one example of  how life can emerge from these watery graves—its   habitat halo is different even from other  shipwrecks in the same marine sanctuary! Every ship has a second life as  varied and unique as its first.

Even though the Portland has been below  the waves for more than 125 years,   its afterlife is far from over. It might look entirely  different again in ten years! As the top slowly sags and is eaten away,   it’s turning what was once a mountain  terrain into a flatter, eroded hill.

The species that live there  will have to adapt, too. Eventually, the Portland will  crumble into a pile of dust,   just as metal shipwrecks  will completely rust away. All ships will dissolve into the  ocean, having donated their nutrients   and minerals to the marine creatures that  kept them company during their afterlife.

In the end, very little will remain. The oldest known shipwreck, which  sits off the coast of Dokos Island,   Greece, is now just a smattering of clay  pots arranged in the shape of a ship. Spooky.

Although a shipwreck’s life after  death is, geologically speaking,   very brief, its ecological impact can last  for many generations of marine creatures. And for all those critters, these  ships that sadly never reached home   ultimately became a treasured safe harbor. [♪ OUTRO]