The Global Biological Context of Maritime History

by Dr. Jim Carlton

About This Lecture

Dr. Jim Carlton's lecture "The Global Biological Context of Maritime History" was recorded in July of 2012 at the Frank C. Munson Institute of American Maritime Studies at Mystic Seaport.  The recording and web presentation of the lecture were made possible by the National Endowment for the Humanities.

1. Introduction to Lecture and Background

Good morning everybody – good morning.  What we’ll be talking about this morning for the next hour or so is one aspect of how the world’s oceans have changed.  But I’m going to start with some larger picture pieces that set the context of how marine biology and maritime history are related.  Various federal commissions in the 1990s and early 2000s uh framed how we have impacted the world’s oceans uh in the following, in the following ways: we have over the past 500 years modified the oceans in a number of ways and this is the list of five major drivers of ocean change.  How long these have operated and where they have operated varies around the world, but this is the big picture.  Fisheries operations, as you know, have a huge impact on the oceans.  Here we talk about not just removing fish, but also how we, how we extract the fish.  The dredging operations, trawling, can really impact the sea floor as dramatically as tropical deforestation.  In this case, however, it’s out of sight, and we don’t see it as clearly as we do when there’s major deforestation.  So fisheries operations are both the extraction of fish and the mechanisms by which we fish that impacts the sea bed.  Water quality, always an issue, generally in the form of either chemical pollution or enhancing nutrients in the water called eutrophicationEutrophication involving the input of nitrogen and phosphorus into coastal waters, from agricultural systems, from the persistent cultural need for what ecologists call “urban grasslands,” what we call lawns, to fertilize coastal areas in various ways either for large expanses of flat green area or for farming purposes.  “Pollution”is such a generic word that it’s almost in quotation marks because we don’t actually say “Is the water polluted?”  We ask what the nature of the pollution is.  There are literally hundreds and thousands of chemical compounds that can be in the water, so it’s much too broad to say “Is it polluted?”  We ask about the specific nature of the pollutant.  Removing and altering the ocean, always an effective way of modifying the coast, in this case, a huge amount of shoreline around the world has been converted to roads, parking lots, roads and harbors.  In general when there’s any flat land adjacent to the ocean we have what used to be mud flats and marshes present in the area.  Areas like Long Island Sound or San Francisco Bay are shadows of their former size because a huge amount of coastal land has been filled for urbanization and agriculture purposes.  So a lot of the coastal ocean is in fact just gone.  Invasions of exotic species, we’ll be talking about that today.  And finally, global climate change.  All of these are, are, interlinked; they’re not independent drivers of ocean change, although by default we’ve often studied them as individual drivers of change because, in a practical manner, it takes a lifetime to become expert in any one of these fields, let alone understanding the relationships between all of these fields.

Global climate change and fisheries are probably the topics that are most hotly debated, that engender the most passion.  Fisheries operations because of the angst between those who go out and fish and the bureaucracy that seeks to regulate those who fish.  So that those who are out there fishing have a different sense of the size and availability of the fish stocks versus what are called the suits, in state capitols and Washington D.C. that set size limits, season limits and so on.  Global climate change is the other topic that has a lot of passion associated with it.  Here we have a lot of misunderstanding amongst what we call “the three Ps.”  The Three Ps are the press, the public and the politicians.  There’s confusion here between whether or not the world is, for example, warming up, and why the world is warming up.  If you, if you reject the idea that humans are responsible, curiously enough, also often rejected is the fact that the climate is changing.  There is no question that the climate is changing and I’ll show you in a slide about that in a little while.  The world IS warming up, there’s plenty of evidence for that, we have clear evidence of the retreat of the glaciers, snow melt, and, of course, the data itself show that the world is warming.  Are humans responsible for changing the atmosphere?  That’s part of the political debate as well; the answer is yes, we are.  We can set that aside, there is not a debate about that.  In fact, among the scientific community, think of it this way: billions of people can change the water quality, nobody argues about that.  Billions of people can change the land, there’s no argument about that.  But, for some reason, people have a hard time thinking that billions of people can change the air around us.  In fact we can, we have, and we can de-couple modern warming from historical warming.  Has the earth warmed and cooled over time?  Absolutely.  Do we know whether the modern cycle of warming is due to atmospheric chemistry changes as opposed to ancient cycles?  We do, and there’s lots of evidence for that.  So, the world is changing and of course that will impact a lot of things, but we’ll get back to that later, in fact the last slide will try to get back to how these are interrelated. 

Further, by way of introduction, there are three basic ways by which we can change the world’s biodiversity.  We can alter the contents of a community, usually by depressing the abundance of species but sometimes we enhance the number of individuals, whether that was the intention or not.  The genetic structure of populations, often, modified.  An example of that would be the ocean whales where we know that the diversity of whales, the genetic diversity of whales, has changed rather dramatically in the past few hundred years.  We can remove species – and those are called extinctions – this is a scale phenomenon.  By that we mean, for example, a species may have occurred at one time in both grassland and forest, now it only occurs in the forest.  A local extinction would be, along the lines of, it used to be all along Long Island Sound and Chesapeake Bay, and now it’s in one small part of Chesapeake Bay or Long Island Sound.  Regional extinction would be a species used to be found all along the Atlantic coast and now it’s only found in one place, such as a bay or an estuary.  Global extinction is the “Wicked Witch” model: that means that, uh, the species is gone from the earth.  And functional extinction refers to the fact that a species still exists, but in fact it no longer plays an important role as a predator or competitor.  Again whales are a good model of this.  There are no extinct whales, no whale species has gone extinct but, where there used to be millions of whales, there might only be a few hundred thousand or a few tens of thousands or a few thousand or even fewer and they no longer really regulate the community in terms of being a dominant predator or a dominant competitor.  Marine extinctions are not well known.  But of course on land, well, it’s a phenomenon that has been spoken about and studied for a great length of time.  Most people do not remember when they first heard about dodos, it’s the larval imprinting about dodos in kindergarten or first grade.  But it’s hard to think of a marine extinction, so there’s a big difference between land and ocean, not in the numbers of extinctions or their importance, but in terms of whether we have studied extinctions at sea versus extinctions on land.  That’s the main difference.  And finally, adding species to a community, that’s called invasions.  For all of these, whether we alter the contents, removing species, extinctions or adding species, invasions, we often divide them up into whether humans are involved or not.  Why do we do that?  Why would we consider – if the outcome is the same, if a species goes extinct, why does it matter?  Why, because if it’s gone, it’s gone.  And while we get into a lot of philosophical arguments about the role of humans in the natural world, there’s often the phrase “Did it happen naturally, or did humans do it?”  That sets up an interesting question, that humans are not natural, which they are.  So that’s the, there’s a lot of philosophical thoughts about how humans play roles in the system and whether it’s part of the natural system.  We’re gonna set that aside. 

2. Drivers of Change, Expansions, Introductions and Shifting Baselines

The reason we distinguish between human versus non-human mediated drivers of change is a much more practical and mechanical and empirical reason, which is that if we seek to alter human behavior, I have to be able to show you what humans are doing vs. what humans are not doing.  I have to make an argument that it is in fact something that humans did.  That’s the global climate change model.  The global climate change model is, I have to show you that humans are involved, otherwise it’s just a natural cycle.  For invasions, we make that distinction because obviously species moved around the earth long before there were humans.  So why, why are we concerned about invasions?  Are we simply speeding up what happens anyway?  Is it simply a rate function?  We divide invasions into range expansions, a phrase meaning that species move around on their own, and introductions, meaning humans move them somewhere.  Invasions are also called alien, invasive, non-indigenous, exotic species and so on.  What I’m gonna argue here is that these are very different phenomenon, it simply isn’t a matter of speeding up what would happen anyway.  Range expansions refer to movement along what are called corridors. These are species moving along coastal margins, along island chains, within an ocean basin, within a continent.  Introductions mean movement across barriers: this is the business of moving any species anywhere in the world within 24 hours, which has no precedent in earth history.  I can move something from Australia to England, from Japan to Brazil, and no species move like that naturally, nor if we waited long enough would they move naturally.  So we’re not speeding things up, we’re moving species across barriers (and barriers are both oceans and continents) that would never, ever get to a new place, given millions of years.  It just doesn’t happen because you can’t get from one ocean, you can’t cross oceans and you can’t cross continents very easily. 

If you think of it in these terms, we don’t wake up every morning in Connecticut and say, “Wow, cool bird from Africa just landed.”  Even though, if you look at the air currents, air currents seem to be swirling around the world.  The reason we don’t have birds landing from Africa is because the ocean is in between and they can’t get here.  So, we can move anything anywhere, again, very easily, 24 hours and that’s the really heart of it.  We have now bridged all barriers and that’s the issue.  Okay. 

Ah, when we talk about the history of life in the ocean, and this gets to something that really underlies the perception of a lot of what we talk about, we ask questions about how we understand the history of life in the ocean, it goes like this.  Basically, it’s before marine biologists evolved, and after marine biologists evolved as a sub-species.  And this is in reference to our view of time, and what time means in terms of changing the earth and the ocean.  Before marine biologists appear – and this is an ocean model of course, we could do this from land – the ocean is seen as what’s called naturally assembled, the so-called “hand of man” has not yet, has not yet commenced.  After marine biologists begin surveying the world that becomes the baseline from which we measure change.  Marine biologists don’t really appear on the scene until the mid-to-late 1800s, humans have been moving around the world by ships for many hundreds of years before that, so we know from human history that the ocean was altered long before marine biologists appeared, and this refers to a fundamental piece of environmental philosophy.  And that is something that you may have heard about, which is called the shifting baseline syndrome.  And this says that we reset to zero with every one or two human generations what we believe is natural.  In our society it’s often the phrase, “You should have seen it when I was a kid.”  That implies, to the person you’re speaking to, that you believe a more natural world was when you were young.  One might say, “My father – or my grandfather – said, ‘The fish were THIS BIG!’ when he was a kid,” which is also a sense that the world was natural back then, and it has changed since that time.  But of course, how do you pick a time against which to measure change? In the United States and Canada and other first-world nations, there are a lot of societies that are called “Restore Chesapeake Bay,” “Restore Long Island Sound,” “Save San Francisco Bay,” “Restore Puget Sound.”  If you get on the websites of all of those non-governmental organizations, those environmental organizations, there’s no date, there’s no target date: restore Chesapeake Bay to when?  To what?  1912, 1812, 1612?  How would you choose a date?  And could you actually achieve restoration back to some time?  Why don’t any of those organizations, when they talk about restoring Chesapeake Bay or restore the Great Lakes, talk about a time?   It’s because in general, the people who have formed those organizations, which are very good, and lead those organizations, want to return it to what they simply believe to be an earlier state.  Not necessarily what the world used to look like before humans were involved.  Shifting baseline syndrome impacts our perceptions of pretty much everything that I’ll be talking about, and all those other drivers of ocean change.  Okay.

3. Shores of North America: Japanese Crabs, Sea Squirts, Snails/Whelks

With that introduction, what I want to do is give a very brief tour of the shores of North America.  We’re gonna start in New England, move around down to Florida, come up to the West Coast, and just ask the question, “If we go down to the shore, what might we see in the way of non-native species?”  For those of you who grew up along the New England coast, the most common snail that you might see is the periwinkle, Littorina littorea, shown here, which is a dominant snail from Canada all the way down to the mid-Atlantic.  It in fact is an introduced species that arrived from Europe in the 1830s, spread dramatically down the coast, in a record that was kept in meticulous detail (if not every week certainly every month) so we have one of the best records of how this snail moved south and west, down the coast, starting from Canada.  Who kept that record?  That record was kept not by scientists, not by fishermen, but by shell collectors.  And so in the 1800s, the public was outdoors vastly more than they are today.  We have butterfly collectors, wildflower collectors, seaweed collectors, shell collectors, rock collectors; a huge amount of natural history was documented by the public in the 1800s in what 200 years later we now call “citizen science.”  Back then, when there was an interest in going outdoors, for entertainment, no radio, no TV, no movies, entertainment was to go out and study the natural world which in fact, of course, was extremely entertaining. 

This snail is a dominant species.  It lives on what looks to be bare rock – they keep the rocks completely clean.  We believe the snail seriously reorganized the structure of intertidal communities along much of the coast before this dominant herbivore showed up.  Two hundred years later or so, a Japanese crab appeared on the coast.  This is now the most common crab of all of New England.  It arrived in the 1990s in Long Island Sound.  Back in the early 1990s we used to offer a hot fudge sundae to Williams-Mystic students to find one of these when it first showed up.  Ten years later we were offering a hot fudge sundae to the student who could find any crab except for Hemigrapsus sanguineus, the Japanese shore crab.  And now of course from Acadia National Park down to New Jersey, it arrived by ballast water that we’ll be talking about in a few minutes, in New Jersey or the Chesapeake area back in the 1980s.  This is an amazing example of an invasion.  It has fundamentally restructured the shoreline and is one of the world’s most efficient omnivores: you don’t want to meet this crab in a dark alley at night.  I’ve testified nine times before Congress and I have never once mentioned this crab.  We can talk about that later as to why that’s the case. 

This crab also offers us a good example of why invasions are a problem, among many other reasons, because this crab changed its habitat after it arrived.  In Japan, it only is found in the rocky intertidal zone.  But you can see from this graph that it’s also here, in New England, very common in salt marshes.  RSZ refers to rocky subtidal zone, SAV to submerged aquatic vegetation.  It is not found in salt marshes in Japan, which are well-surveyed, and one of our challenges when a species moves from one place to another is trying to predict how it will change its habitat, its biology, its ecology in the absence of whatever regulatory mechanisms were controlling it back in its homeland. 

Another important species that invaded New England in the 1990s was the sea squirt.  Sea squirts are chordates, related to you, they are often abundant, they are fouling organisms that attach onto artificial substrates.  And this is a Japanese species called Didemnum that somewhat surprisingly was discovered out on the fishing banks – largely former fishing banks – of Georges Bank when the U.S. Geological Survey did some work out there in the late 1990s/early 00s.  This is a species that can form these huge meter-long tendrils, big gelatinous masses that cover huge areas of sea floor.  They impact what is on the bottom in the sense that they can cover scallop shells and other hard substrate.  Small scallops, baby scallops, require sediment, rocks, shells to land on; they can’t settle on sea squirts, and so there’s a potential impact here on the scallop fishery. 

Discovering invasions in the offshore waters is unusual, but in this case can be related back to the fact that invasions often occur in highly disturbed habitats.  Georges Bank, back to our earlier thought about fisheries, is such a highly disturbed habitat, having been extensively trawled, it becomes more like a weedy lot susceptible to invasions by exotic species.  Here’s another sea squirt – you sort of have to like sea squirts to be into these guys.  This is about 6 inches, 15 centimeters long.  It’s another Japanese species called Styela.  It arrived here in the early-mid 1970s again spreading along the coast, became extremely abundant.  Here’s a line from a buoy down to the bottom of Mystic River estuary showing dominance by this sea squirt and by the seaweed Codium (another Asian species that showed up in the 1950s).  And here you can see that the only things you can see are Japanese algae and Japanese sea squirts on a line associated with marine structures here in Long Island Sound.  What was here before Codium and Styela is surprisingly not so clear, an example of the shifting baseline syndrome where it’s hard to get a picture of what used to be before we started paying attention to certain species.  Here is Styela again.  This is the bottom of a float turned over in Narragansett Bay, a hundred percent cover of Asian sea squirts where it used to be a hundred percent cover of native mussels.  And finally here is Styela yet again in mussel farms up in Prince Edward Island Sound.  And here you can see Styela completely covering the marine facilities here.  Where are the mussels?  In the mussel farm, somewhere under the Styela.  This is the kind of economic impact that can be very important relative to invasive species. 

Now we’re moving down to Chesapeake Bay.  This is where there are somewhat more than a hundred known invasions and probably a lot more in the bay.  This is a 6 inch tall snail called the rapa whelk, the Asian whelk Rapana, which eats oysters and clams and shellfish in general.  This is not a species we want in Chesapeake Bay, which has shellfish problems already.  In this case, this large snail, which happens to be edible, has not spread (as far as we know) very far from Chesapeake Bay, in part because, at the Virginia Institute of Marine Sciences, since 1998 they’ve had a bounty on this snail.  They’ll pay $5 for a live one, $2 for an empty one.  There’s a large room at VIMS filled with nearly 20,000 shells, which is an incredible database to look at the population of this snail, but it may be that this kind of harvesting has depressed its spread along the coast.

4. Caribbean Creep and Warming Waters: Lionfish, Pill Bugs, Mussels, Jellyfish, Snails and Shrimp

Let’s move down the coast a little bit down to the Carolinas and Georgia.  And down along the south Atlantic coast we have a phenomenon now called “Caribbean creep.”  And this is related to climate change.  These are species that are Caribbean in nature which are now living and abundant on the coast of South Carolina, Georgia, and so on.  We think of South Carolina and Georgia as warm, but of course it’s too cool for deep tropical Caribbean species.  Where it used to be, this crab up here, Petrolisthes, is now the most common crab along the South Carolina coast.  These aren’t one-off invasions, these aren’t occasional specimens that show up.  The Caribbean crab Petrolisthes armatus is now the dominant crab along the south Atlantic coast because the south Atlantic coast is warm.  This is a large barnacle called Megabalanus, again a warmer-water southern species that’s been moving up the coast.  And in general what we are seeing, on all monitored coasts in the northern hemisphere, are that species are moving north.  The mirror image is true in the southern hemisphere of course, where species are moving south.  Think of the entire world as expanding biologically because of warming.  This is well-known on land, and now, getting better known in the world’s oceans as well.  One of our clearest signals of climate change in the ocean are lots of southern species that are now heading pole-ward, due to ameliorated conditions. 

Moving down to Florida – and this is just a slide that says that these are permanently established species – we have a foot- long fish called the Pacific lionfish that invaded from the Pacific Ocean.  Exactly how it got to Florida in the 1990s is not clear; possibly through the aquarium trade.  It’s now common off the Carolinas, it’s found in summers north to Cape Cod, it’s very abundant around the Bahamas, all the way down to northern South America.  This is a large, poisonous, aggressive, carnivorous fish that eats small fish like popcorn.  It’s also edible, and it’s been entering the restaurant trade, as long as you don’t get stuck by those spines, so there is a campaign out there to try and eat this fish, as some kind of a mechanism for control.  But this is a major invasion of warm reefs along our southern waters, and we’re watching with interest how it will respond to climate change and perhaps become abundant further north. 

Also in Florida, we have mangrove forests.  Mangroves replace marshes in warmer waters; marshes become mangrove forests, and here you see the prop roots of the red mangroves along the east coast of Florida, here north of Miami in the Fort Pierce area of Indian River Lagoon.  These prop roots are chewed up.  You can see they’re highly damaged, and if we did around inside those prop roots it turns out that there is a little crustacean, a pill bug called Sphaeroma, related to the little roly-polys and pill bugs of your backyard.  In this case it’s a marine species that chews up the seaward roots of the mangrove trees.  Back in the 1970s it was the subject of a lot of interest as to the relationship between this little isopod crustacean and the mangroves and how they were related.  But what was not known back then is that in fact this is a species that was introduced from the Indian Ocean in the 1800s, the late 1800s, and is not native to the western Atlantic.  Why do we concern ourselves with a little crustacean hardly one-eighth inch long?  The interest of this kind of story is twofold.  One is, it’s the shifting baseline syndrome, which is that this species was long assumed to be native because when the first marine biologists showed up it was already there, and therefore this was thought to be a natural association.  And now that we realize that it was introduced by ships, from another part of the world, into the warm waters of the western Atlantic, we realize that one species, one small marine invertebrate, has reset the history of mangrove forests from Florida to South America.  It’s not about the size of species.  It’s not about how well-known they are.  It’s about their ecological role.  So here’s a poorly-known animal, which in fact has impacted one of the dominant species of the warm waters of the western Atlantic.  And it was introduced in the 1800s but we didn’t realize that until the late 1900s. 

Here we are in the Gulf of Mexico, where the number of invasions is not known, poorly studied.  These reefs of dark mussels over here represent a species of southern mussel called Perna perna that was introduced in the 1990s and now dominates shores from Texas to Florida.  And these white dots here in this photo are the jellyfish Phyllorhiza from the Pacific Ocean.  This is shown next to a pleasure craft here in the Gulf of Mexico.  Every few years since the summer of 2000 they have these huge blooms.  At the densities here it’s hard to get out, for example, and do fishing.  Shrimp fishermen can’t operate in waters like that.  Each one of those jellyfish is two feet tall and weighs twenty-five pounds.  It’s an introduced species that got in by some mechanism from the southern Pacific Ocean into the Gulf of Mexico. 

Moving over to the California coast, we have a picture here from San Francisco Bay, in central California.  This could be a picture from any biology book or any marine ecology book.  This is called zonation: the barnacles are on top, the things here in the middle turn out to be tube worms, and on the bottom we have mussels.  Classic picture of how species are zoned by tides and by competition along the seashore.  In this case, however, it’s a mixture of introduced species.  The species on top is from the North Atlantic Ocean, the animal in the middle is an Australian tube worm, and down here we have the common New England mussel, Geukensia.  These are species that have been reassembled in San Francisco Bay and are forming a new community in ecological time, not evolved over evolutionary time.  The number of invasions in San Francisco Bay is well over three hundred.  There are interesting stories about why the bay is so invaded but I’ll just say that that number exceeds all the known invasions along the entire Atlantic coast of North America from Canada to Florida.  In San Francisco Bay alone we have hundreds of species, far more than on the entire East Coast. 

In San Francisco Bay we have another one of our little pill bugs, a related species of isopod, this time a species from New Zealand, not the Indian Ocean, that invaded California in the 1890s.  They chew up the shoreline like Swiss cheese; the erosion in parts of San Francisco Bay has been measured in meters per year, and so this is a species that really shapes the topography of the shoreline.  This is a warm-water species, and it’s been sitting in California for well over a hundred years.  It can’t move north into the Pacific Northwest because the Pacific Northwest is simply too cold.  So you know what the next slide is.  The next slide is that in fact it invaded Oregon in the 1990s.  It showed up in Coos Bay, well-monitored bay, where we could detect its first arrival.  Here’s a piece of Styrofoam, about a foot and a half by two feet, in which there are thousands of isopods, they burrowed into the Styrofoam.  It destroyed marinas in the back of Coos Bay that were held up by Styrofoam, floats and docks which were abandoned.  And students from the Williams-Mystic program who accompanied me out to a marine lab in Oregon several years ago determined that a population of 100,000 isopods could produce more than 20,000,000 particles of Styrene per day into the ocean.  However, that’s not the biggest impact.  The biggest impact is, that just as in San Francisco Bay, this little isopod is now eroding Coos Bay, the largest bay in Oregon, where large pieces of the Bay are in fact falling off.  There’s no technology we have that would stop this isopod from moving north with climate change, so we’re expecting the history of the Oregon bays to begin to change in a different way due to the erosion by this little isopod originally native to the South Pacific Ocean. 

One last example before we get into how all this happened.  One of our latest invasions is a little snail from Japan that showed up also in Coos Bay.  It turns out to be the host of a mammalian lung fluke, as well, which turns out to be a threatened species in Japan and now occurs by the millions, if not billions, in the salt marshes along the Oregon coast, where we’ve measured numbers and densities well into the thousands and tens of thousands per square meter.  It may be impacting a native species of marsh snail, called Assiminea californicum, because in areas where we used to find this native snail, we can’t find any of them at all, dominated by this new invasion by this Japanese snail.  Here’s an interesting example where a species, which was rare, threatened in its homeland, has become extraordinarily abundant where it was introduced.  And we’ve thought about maybe selling these back to Japan at a quarter apiece to fund some research. 

A recent local invasion, just to bring it back here to the Mystic River, is the Japanese or Oriental shrimp Palaemon macrodactylus.  This was discovered here in June of 2010.  We know from earlier observations that in fact it was first seen in 2003, and this is a species that is now dominant in parts of the Mystic River.  Invasions continue in New England on a regular basis.

5. Modern Awareness of Invasions: Zebra Mussels, Global Bio-Flow, and Ballast

That’s a picture of the marine shores of North America.  I want to visit for one moment  an event that precipitated a lot of the modern interest in invasions and that was the discovery, in the Great Lakes, in the 1980s, specifically in Lake St. Clair (between Lakes Huron and Erie) of something that many of you have heard about which is called the zebra mussel.  It’s a small bivalve mollusk – it’s not about its size, it’s about its abundance and what they do – it’s native to the Black Sea area.  It attaches to substrates with byssal threads.  If you put your hand in the Great Lakes for long enough this thing can attach to you.  It can be upside down, right-side up.  It’s a filter feeder.  In this view here this long piece over here is a mussel; these are small mussels over here.  And what they did early in the invasion of the Great Lakes is that they created a huge amount of water clarity.  They cleared the water but they didn’t clean the water.  But people living along the shores of the Great Lakes, remembering it as children, saw that what used to be visibility down to two or three feet was suddenly visibility down to twenty feet.  So there was a confusion between clear and clean water; the zebra mussels don’t necessary remove all of the things that are in the water.  PCBs and heavy metals and pesticides – the water would still look transparent, with all of those compounds in it.  This species became a major fouling organism.  This was a small pipe that was closed, you can see the human hands here, the zebra mussels began to fill up pipes (and there were hundreds of thousands of pipes in the Great Lakes), pipes that were three feet in diameter, or closed down to a six-inch bore.  And many of these pipes ran underground for miles with no access, because there never was a species in North America like this that could fill up pipes.  Here’s a buoy.  Many buoys around the Great Lakes simply sank out of sight, covered with zebra mussels.  Park too close, here along the shore, this is a native mussel, mussels disappeared, the large thing here is a native mussel (we call it a clam in marine waters and mussel in fresh waters), and mussels, native mussels simply disappeared.  In Lake St. Clair they were smothered out by zebra mussels.  A crayfish.  A water treatment plant.  A year later, where the water stopped running in people’s homes in Monroe, Michigan.  And a beach scene, where people used to walk and not cut their feet, but now these sharp shells meant they couldn’t walk on the beaches anymore in bare feet, which many people did since they were children.  This one species precipitated modern-day interest in many areas of what are now called aquatic invasive species and marine invasions. 

Let’s talk a little bit about how all this happened.  How did all these species get moved around the world?  We talk about this as global bio-flow.  And this refers to two types of phenomena.  There are things we move around because we didn’t mean to: on the bottoms of ships, with oil platforms, on our boots.  And then lots of species we move around because we wanted to, because we put them out there in the world to start a population for harvesting, to be eaten.  Because we thought they were ornamental, like the mute swan.  Because they were released from bait activity.  So these two categories have led to the movement of a lot of species either inadvertently or advertently around the world, for a long time, as long as humans have moved around the world.  This is the story that brings us to maritime history because overwhelmingly, the story for the oceans has been the story of ships.  How ships have moved species around the world is a fundamental way in which we now look at marine biology.  How long have people been going to sea?  What’s the history of ancient voyages and the oceans?  We don’t know.  The first ships were all biodegradable.  They’re gone.  People were on the Pacific Islands forty thousand years ago, and they didn’t swim there.  Recent work in the past couple of years have detected that there were people on Mediterranean islands one hundred thousand years ago, and they didn’t swim there.  People have been going to sea for a long, long time but the evidence is cryptic and buried in antiquity.  What we do know is that for the past five hundred years, in the great era of global expansion, shipping became very busy, since the 1400s.  By the 1500s the Spanish empire was all through the Pacific Ocean.  That means that ships were leaving the European theater, sailing around the Pacific and coming back to Europe.  And finally, what are called pulses have played an important role in distributing species by ships: wars and gold rushes.  Why are these interesting?  Because they fall away from classical routes of exploration and colonization; they create new pathways for ships that come and go.  Wars happen, lots of ships go to one place, the war stops, and that route stops.  Gold rushes have the same effect.  The whole picture paints a very busy world, and as we’ll see very soon, one that has gotten much busier. 

What are we talking about in terms of how ships move marine organisms around the world?  We’re talking about things that attach to the bottom of ships: hulls, keels, rudders.  Literally thousands of species are now to have been, and still occur, on boat bottoms.  Whether it’s sponges or mussels or seaweeds or sea anemones, this can be a very diverse community and historically, apparently, was much more diverse before the development of anti-fouling paints and other things that have changed what lives on the outside of ships.  When there were wooden ships we had what were called boring communities.  And shipworms, which are clams, and gribbles, which are our little friends the pill bugs again, used to bore into wooden ships, creating galleries into which you could put your entire arm up to your shoulder.  And these galleries created spaces in the hulls of ships which could hold crabs and fish, which would otherwise be washed away from the hull of the ship but here had places to hide literally inside the ship.  Wooden boats are essentially extinct now in terms of global vessels that move around the world, but this was a huge part, of course, for hundreds of years, wooden ships moved around the world and distributed many species with them as opposed to what was on the hull of an iron ship or a steel ship. 

The story of dry ballast, solid ballast, moving rocks and sand around the world is the story of moving creatures from seashores all over the world.  Plants and insects and snails and spiders, a story well-known to terrestrial biologists, not so well-known to marine biologists, but we have a lot of evidence that this impacted the shores of the world.  Long before water ballast was used to stabilize ships, ships put anything heavy that they could find in the ship, when they were not in what’s called a cargo configuration.  So if your ship was empty, you needed a lot of weight to keep the ship stable, you gathered up rocks, sand, debris – whatever you could find – that was free or cheap and put it in your ship and dumped it someplace else around the world.  Of course very often that had living animals and plants in it.  The last major episode of moving dry ballast, which involved more terrestrial, land-based organisms than marine organisms, was at the end of World War II, when ships returning from the European theater loaded themselves up with the rubble from the bombed-out British cities.  And as you know during World War II a lot of British cities were heavily bombed by German planes and German rockets, and much of that rubble that was brought back to the Atlantic coast was laid out along the shore of New York City.  It eventually was to build FDR Drive, along New York, and there’s a small bronze plaque, in New York, along FDR Drive, that says, simply, “Here lies Bristol, England.”  But we know that in fact this was a major mechanism for hundreds of years, replaced by the 1880s with water ballast.  The whole picture – and we’ll talk about water ballast in detail in just a moment – is the ship’s a floating biological island.  Very busy community, certainly well-known that it had rats and cockroaches, but in fact vastly more than that.  These were floating islands of animals and plants moving around the world dispersing thousands and thousands of species long before biologists showed up.

Ballast water came into play in the late 1800s and became very, very common after World War II.  Ballast water is shown here in yellow and what we see here are called fore peak tanks at the bow, aft peak tanks at the stern, and way up here in the bulk carrier you can see what look like tanks at the top of the ship, which is kinda weird.  Those are called top side or upper wing tanks up here, which gives more lateral balance.  And I’ll show you one of those in just a moment.  This is from a trade magazine showing container ship routes around the Americas.  Container ships have a lot of ballast tanks filled with seawater, and if a species were to get introduced to San Francisco, or to Chile or to somewhere else in the Americas, these can be easily spread around by these container ship routes.  Container ship routes are very much the trucks of the sea in the sense of having fixed times of arrival and departure; highly scheduled, highly regulated, as opposed to other ships which are still more tramp vessels (and I’ll show you one of those also in a moment).  Ballast water by review, again, ships can carry up to tens of millions of gallons of water, that water can be anywhere between hours and months old.  Ballast water is not bilge water.  Bilge water is this water that gets into the ship unintentionally, for example, under the plates in the engine room.  This is what we call a tramp vessel or a spot cargo vessel.  I have a vessel here that is – this is an actual route, that can carry 35,000 metric tons of ballast water.  It’s leaving North Africa to go to Argentina to pick up cargo.  That means it’s empty leaving Morocco, and is about to treat Argentina, although Argentina doesn’t know this, to a ship-load of Moroccan marine life.  It does so, it discharges all the ballast water it picked up in Morocco, to load black beans from Mexico, and on the way it gets orders to proceed to New York to pick up another cargo.  It now takes water from the Veracruz River in Mexico up to Long Island Sound, to pick up New York City’s largest export product, old cars and refrigerators, which are now going to be taken to Madras, India and so on around the world.  A great many ships spending half their lives in a ballast configuration.  This morning as we talk there are some 40,000 ships at sea. 

This is the Pennsylvania Getty, it’s just arrived from Germany after a voyage across the North Atlantic Ocean.  Before that it was Thailand, carrying tapioca to Germany in cargo.  It now arrives empty to pick up coal for Japan.  It’s not empty.  This vessel, the Pennsylvania Getty, registered in Monrovia where it never will be, if this vessel was empty and tried to cross the ocean, it would turn upside down and everybody would be embarrassed.  It’s got about eighty percent of its weight here in water.  We’re gonna get on that boat, we’re gonna take off the hatch to what I just showed you, you remember, those top side upper wing tanks, here’s the crew unbolting that hatch, here is a biologist in the red t-shirt, here’s the crewman over here, been on the boat for ten years, has taken away our plankton net because he can’t believe there are fish in the vessel, there are fish in the ship.  He’s trying to capture those fish that have been captured in the Weser River in Germany, and have been brought over to Delaware Bay for unintentional release.  This is not a great way to sample ballast tanks because when we take that hatch off, the sun reappears in the tank (the fish don’t know why the sun disappeared eleven days ago but it did) and as you sample the concentration of life gets more and more because they’re being attracted to the light. 

Instead we can get on other kinds of ships such as the Papyrus, which is a huge ship, designed only to carry chipped wood, from around the Pacific Rim back to Japan, for its entire thirty-year life.  This ship will visit Tasmania, Tahiti, California, British Columbia.  Fills up with 25-30,000 metric tons of chipped wood being brought back to Japan, processed into newsprint, pressed boards like you buy in Wal-Mart for college dorm rooms, and that material is then shipped back to America and other places.  The Papyrus is filled with seawater in the middle and what’s called a ballastableor a floodable hold.  It’s reinforced, it’s a lake of water – it’s big enough to put a boat in with an outboard motor and take plankton tows – it has other water in the fore peak and bottom tanks as well.  Or you can get alongside the tank, lower a plankton net as Tora (?) is doing here, into a fifty to seventy-foot water column and take vertical hauls and find how much life there is in the water and what has survived the trip from Japan, in this case, to Oregon.  What we find is that there’s a huge diversity of life in ballast water.  Whether it’s copepods or worms, barnacles or clams, snails or crabs, studies all over the world in the past 20 or so years have found that there are just a tremendous number of species moving around in ballast water.  Linda here is holding a fish: she’s gone down to the bottom of a ballast tank where she found 50 of these foot-long fish that had arrived from the eastern Mediterranean into Baltimore where they were then subsequently released into Chesapeake Bay.  Okay. 

6. The Big Picture: Canals, Globalization, Port Residencies, and Concluding Thoughts

The big picture is this.  These are the main ocean sailing routes – very stable – from the 1500s to the mid-1800s.  These were relied upon as predictable, known and safe routes for nearly 300 years.  This is the change on the picture from the 1850s to the 1950s.  Gonna go back and forth; see if we can see the difference here.  Here’s 1850s to 1950s, there’s the two hundred to three hundred years before it, one more time, this is how the world changed in only one hundred years and one more time.  And what changed?  What changed were the canals.  Panama Canal in 1914 broke through the Americas, Suez Canal in 1869 broke through Eurasia and now the world changed.  If you were a sailor in the 1860s and lived into the early 1900s you saw all of this happen.  You saw ships’ routes, and the length of time it took to sea, change by weeks.  This was a fundamental revolution in the history of commercial trade and in the movement of people.  No longer did you have to sail around Cape Horn or the Cape of Good Hope and experience the dangers.  You could travel through these canals and get to where you wanted to go much, much faster.  What’s that got to do with invasive species?  The trip was much shorter.  And so, your probability of living on and in these ships increased dramatically, because the trip was shorter and we saw a surge of invasions after these canals were built, because now the trips were more benign by being shorter.  That’s until the 1950s. 

Here’s the world today.  Much busier.  Globalization has increased the number of trade routes vastly.  The number of ships at sea have increased dramatically.  The size of ships and the speed of ships have changed.  Here’s an interesting website.  Here are the number of ships out there, reporting just weather at sea, today, on June 25th (2012).  It’s a very itchy world in terms of shipping.  And what we think, is that at any one time, there are many thousands of species in ships’ ballast water, moving around the world.  It’s hard to imagine what would be a comparable mechanism on land.  How many planes land in America every day?  How many pieces of luggage arrive every day from around the world?  What’s in the luggage? Where were the flowers in the local florist shops 48 hours ago?  They weren’t in America.  They were in Venezuela, northern Italy, the Netherlands.  But when you walk into a florist shop, you’re not hit with a cloud of insects, which speaks to the chemical nature of that industry.  But at least in the ocean, we know that the global bio-flow related to ships largely remains today, although there’s been a good deal of concern and attention related to ballast water-flow management. 

Here are a few examples of the scale of change.  This is the European shore crab which appeared in New England in the early 1800s, had a long quiet period before it appeared in the 1870s in Australia, and then nothing for nearly a hundred years and then – bang.  Began to appear all over the world: in Japan, California, Argentina and South Africa.  Here’s another similar pattern.  The Asian mitten crab is moved by ballast water from Japan to Germany, where it appears in 1912, all is quiet until it appears in the 1990s and 2000s in North America.  Another example: the Asian kelp, a big seaweed called Undaria, which appears in 1971 in Europe, quiet for thirty years, and begins expanding around the world in the 1980s and 1990s.  And one more example, a very common Pacific coast barnacle, Balanus glandula, which went nowhere for hundreds of years until it appeared in Argentina in the 1970s, South Africa in the 1990s and Japan in the 2000s.  We relate all of these to globalization – the increase of world trade and the increased spread of species.  And one more, actually, here’s that sea squirt that I showed you on Georges Bank, which is a modern-day invader.  1970s in New England, 1990s in Europe and the Pacific coast of America, 2001 down in New Zealand.  Many, many patterns like this.

To summarize, what are we looking at?  We’re looking at a difference in shipping where, hundreds of years ago, ships at sea were moving less than ten knots, had what we call long port residencies and very ineffective ways to keep species off their hulls.  Contrast that to the modern ships, which go at more than twenty knots, have very short port residency and have very effective anti-fouling paints.  Copper, used to be a lot of tin, heavy metals, on their hulls.  What changed was of course that, when ships get much faster at sea, much less can stay on because of the water flow across the hull, I’ve got poisonous paints on the hull and, very critically, very short port residency.  Hundreds of years ago, a vessel would come into a port and stay for weeks, if not months.  You’d have to find crew.  You’d have to get cargo.  You’d have to load up with food and fresh water.  A modern ship will arrive in Boston harbor out of Europe at nine in the morning and be gone by noon.  Three hours.  Surgical strike.  No ship is gonna hang around the dock and let the crew go to shore at $15,000 an hour.  The modern sailor rarely gets off the boat, going around the world.  So, striking change, but what we also did was move the species from the outside of the vessel, on the hull, to the inside of the vessel, in ballast water. 

Last couple of slides.  What we’re faced with is that due to human endeavor and ingenuity, the number of ways in which we move species around the world has doubled every hundred years.  For our green crab out of Europe, to see the world in 1800, you could either be loaded with rocks into the hold or hang on into hull fouling.  Only 100 years later, ballast water had been introduced, and we were moving large numbers of oysters around the world.  Only 100 years later, in the year 2000, here’s the list.  We still have water ballast, we have hull fouling, oyster movements, and now seaweed is moved with bait worms around the world.  Oil platforms are moving.  Shellfisheries and aquaculture have increased.  Live bait.  The aquarium and pet trade moves crabs and there are biological supply houses.  That line continues to go up and one of our challenges for science and management is that this itchy world seems to increase.  Back to that very first concept of the drivers of ocean change and what does that relate to invasions of exotic species and maritime history? 

We already emphasized that there were ways in which the oceans continue to change on a regular basis.  Habitat alteration, water quality, fisheries, introduced species and global climate change.  Again, not mutually independent.  Obviously if I change the climate I’m going to change fisheries.  If I change the climate I’m going to make an environment more susceptible to invasions.  If I change fisheries, I’m going to change habitat.  If I change, if I introduce species, I’m going to introduce species that possibly are going to erode the shore.  These are all clearly interrelated.  That means that the coastal environment is constantly in motion.  2012 and 1912 look very, very different.  On the other side of this equation, is that world trade is increasing, as we’ve just seen.  Petroleum exploration is increasing, not decreasing, despite huge oil spills.  The live seafood industry is expanding and moving species around the world on a daily basis.  The number of recreational pleasure craft moving around the world increases.  As a result, there’s a constant change in vectors, which are meeting a constantly changing kaleidoscopic environment and the predictable thing in the middle is that bio-invasions come out of it.

I’m gonna end with a piece of good news, on a positive view of this, which is, despite all of these drivers of change, and an increasingly busier world, we live in an era where there is more attention to these drivers of ocean change than ever before in our history.  Conservation biology, marine conservation science, is now a full-time career.  A great many students want to go into conservation biology, restoration science, and preservation science, moreso than ever before.  We have more environmental organizations dedicated to monitoring and understanding the oceans, from a citizen science point of view, than ever before in history.  So I’m rather optimistic that despite the diversity of drivers of change, despite the diversity of vectors that move species around, we are likely to see fewer future invasions because of much greater subscription by more and more people as to how to interface with and alter how we’re changing the oceans.  Okay.  Thank you very much.  All right.  Questions from the audience?

7. Questions from the Audience

Female audience member: “What are they doing about the ballast water?  I mean that seems to be huge?”

  1. Ballast water management has been under discussion since about 1989, 1990.  So we’re about a quarter century into a discussion and regulatory frameworks for how to manage ballast water.  For many years the focus was on exchanging one’s water on the open ocean.  The Pennsylvania Getty, coming out of Germany and coming to Delaware Bay, today would dump all of its water from the Weser River estuary in the middle of the Atlantic Ocean and arrive in Delaware Bay not with estuary species and bay species from Europe, but with open ocean species that could not survive in Delaware Bay.  Many ships can’t do that because of safety issues.  If the seas are running 5 meters or 15 feet, you’re not going to let go if the only thing that keeps you stable is ballast water.  I’m not going to let go of the ballast water and destabilize my ship in rough water.  So open ocean or high seas or mid-ocean ballast water exchange has been a stop-gap measure for nearly 20, 25 years, but now we’re moving toward ballast water treatment.  And ballast water treatment means that ships are gonna have to treat their water in some way.  Filtration, chemical treatment, heating, ultraviolet, some way in which they’re going to remove nearly everything but viruses and bacteria, before you can dump your water out in a new location.  We’re moving in that direction.  In the next 10, 20 years, most of the world’s fleet is likely to be equipped with ballast water treatment technology focusing on new ship design and new ship building.  The overall picture will be that it will take between 40 and 50 years between the idea that ballast water needed to be regulated and converting the world’s fleet to ballast water management.  For a lot of folks, that’s a very long period of time, but it’s often typical in environmental regulation.”


Male audience member: “Do you find that there’s a difference in intensity and threat for land-based marine invasions as opposed to oceanic marine invasions like say invasions from between the Great Lakes or other landlocked…”

  1. The Great Lakes are really unique in the sense that there aren’t very many huge inland lakes in the world.  The Great Lakes are the largest freshwater lakes in the world, got no real counterparts.  I’ve got other inland seas, like the Black Sea and the Caspian Sea which are salty, and there are large inland rivers.  So there are a lot of river invasions and pond invasions and stream invasions, but there’s not much of a global model for the Great Lakes.  The Great Lakes have been highly invaded.  We’ve got nearly 200 species that are in there now from around the world, especially since the St. Lawrence Seaway opened up in 1957 and created a very strong corridor of global shipping into the Great Lakes, although we had invasions in there because of the canal systems that preceded the building of railroads.  Remember that by the late 1700s, and early 1800s, long before railroads, much of the East was highly dissected with canals and those canals were built to move small river boats across the East and into mid-America and that actually spread a lot of species even before we had railroads.  Many of those canals are now gone but a good forensic urban person could walk along many city streets in eastern America and show you where the canals used to be.  Kinda cool: there’s a canal historical society that goes looking for old canals.  So it’s well invaded, fortunately/unfortunately we don’t have many other systems quite like that.  There are patterns of invasions, and we mentioned one of those, which is there are more species in San Francisco Bay than on the entire Atlantic coast, and that’s thought to do with the geological and ecological and evolutionary history of different areas, some of which are more susceptible to invasions and others are apparently more resistant to invasions.  Theoretical stuff.”


Female audience member: “So were there ever times when people tried to use the introduction of another species to control invasive species?”

  1. The mongoose was introduced on a number of islands around the world to control rats.  Turns out the mongoose comes out during the daytime and the rats come out at night.  The mongoose then began to eat lots of things and now we have a number of globally extinct birds, which were ground-nesting birds that evolved on islands without any predator, which were completely taken out by mongoose.  This is called biocontrol.  Modern-day biocontrol scientists say, ‘Well, we didn’t release the mongoose, the mongoose were released by farmers and by citizens.’  Today, the idea is you would never release a species to chase another species unless you absolutely knew that the only thing it would eat is the species that you’ve targeted.  A lot of biocontrol releases that went terribly wrong were because we released generalized predators that not only would eat the exotic species that was of concern but ate everything else as well.  So that’s bad.  So on land, biocontrol is actually a very common thing.  We chase a lot of agricultural pests with highly specific parasites and parasitoids.  Australia is said to release a new biocontrol insect about once a week, each one preceded by about 10 years of research.  It’s a big plan.  In the ocean, not much because we haven’t really been able to really show that we have species-specific predators that would really control the Asian shore crab, for example, now in New England.  Right.”


Female audience member: “And what about those little critters in Coos Bay?  I mean, that looks pretty devastating.”

Dr. Carlton: “Yeah, the little pill bugs, it’s attacking the shoreline and you know, that’s an interesting example of where our technology is limited.  I can put something the size of a desk on Mars to take pictures of rocks – which costs billions of dollars – but I can’t stop this little crustacean from moving north.  So it’s something that eludes us, it’s hard to control a species in the ocean, and it’s a good example of how climate change is going to have to be looked at in terms of the management of what species are gonna be coming towards us.  In New England, two things are happening.  We have a lot of species moving north, and what I didn’t mention in the talk was that New England is of course getting warmer in general and as a result, species that have been coming in from all over the world since the 1600s, which historically found New England too cold, are now going to become established.  So we’re getting two kinds of new invaders: stuff that is moving up from the South inexorably, and global species that have been coming in (and that have always been coming in) but which could never historically survive in New England.  And of course the warming of New England is very dramatic for anybody who grew up here.  The Mystic River is a great example.  The Mystic River in the 1800s could be crossed by, on a winter day, you could actually walk across it, it was frozen solid.  You could take a horse and buggy across. By the 1950s, navigation was impossible above the Route 1 bridge, in the Mystic River, because the Mystic River was closed up by ice.  By the 1980s, that had disappeared, but even in the early 1980s, when we went down to sample plankton in January or February, we had to take large steel poles to break through 6 inches of shore ice to get our nets in the water.  And that all stopped 20 years ago.  And in the winter now, I don’t need to break through any ice, and I never will again.  I can just go down there and drop my net in the water.  So a picture of that, which requires sometimes looking at across more than one or two human generations, is very clear in terms of how New England is warming.  Confusing is that we get just as much snow or more snow, so people wonder, ‘How can the winters be getting milder if we get a lot of snow?’  That’s because of course the greenhouse effect – the greenhouse gases are trapping a lot of water in the atmosphere as well as other gases.  More water is trapped in the atmosphere as well as other typical greenhouse gases, and that means when there’s precipitation, and it’s cold, it’s gonna snow.  So in fact there’s more water to create more snow but overall, the winters are going to get shorter and milder and species that are here will survive better than they did historically.  Okay.  Thank you very much for your questions.