Sunday, February 19, 2017

Siren Songs

Last week we looked at one of the most productive ecosystems on earth, sea grass prairies. Sea grass prairies house many animals that fill very similar ecological roles to terrestrial counterparts. The most notable, and tragically least discussed in the previous post, is the manatee. Thankfully manatees and their cousins are such a rich topic that they've earned their own post.

 Try not to look so excited, geez.
Courtesy Tracy Colson via Flickr

Almost everyone has heard that manatees are likely the source of mermaid legends, or at least were mistaken for mermaids after the legend had been around for a while. In fact the name of the manatee's order, Sirenia (pronounced: sih-ree-nee-uh), actually comes from the sirens that tempted Odysseus while he sailed from home after the Trojan War. Many people find it a bit surprising that such large, grey, and cowish looking animals could be mistaken for half women, half fish; but beyond sailor's missing home there's actually a decent reason sirens could have been mistaken for their namesake. Female sirenians have breasts in the exact same position that human females do. Add the fact that they nurse their young while floating vertically with their heads above water, and you can see how people could have made the mistake that there were aquatic humans.

Though manatees are often called sea cows; it's believed that sometime around 50 million years ago a close relative of elephants slipped into lakes and streams to feed on the rich grasses growing underwater. Over time these four-limbed sirens became more and more adapted to the life aquatic and their descendants spread out across the globe. Then as the earth cooled to today's more familiar state many sirenians went extinct, leaving us with only four species.

Unfortunately there isn't anywhere in the world where you can see all 
four species at once. This manatee quartet (dibs on the band name) is made 
up entirely of one species.
Courtesy: David Hinkel via Flickr 

All sirenians scour the river, lake, or sea floor searching for underwater grasses to eat. Other marine mammals eat meat, and so have access to copious amounts of fat and protein to keep their weights up and their bodies warm. Sirenians are the only herbivorous marine mammals so they have to eat about 10% of their weight every day. Quite a lot when you consider they can weigh between 500 and 800 lbs. One study found that a single sirenian needed about an acre of constantly regenerating sea grass per year in order to get the food they need.

Sirenian mouths are well adapted to consuming large quantities of plants.  On every species the mouth is turned downwards to the seabed so the siren can look ahead as it grazes. Their teeth are specialized for grinding up veggies and are constantly replaced with new ones as they wear down, just like a shark's!

Modern sirenians are all found in the fresh and nearshore salt waters of the tropics and sub-tropics. They're extremely intolerant of cold and will move out of waters that fall below about 68 degrees Fahrenheit (20C). This need for environmental warmth may be a consequence of having evolved during a much warmer period in Earth's history. Only one sirenian, the Steller's Sea Cow (Hydrodamalis gigas), managed to adapt to frigid waters and survive to the modern era, but believe it or not, we ate them all. 

In case you ever thought your drawing skills aren't good enough for natural history; 
this is thought to be the most accurate drawing of a Steller's sea cow because 
it's the only one we know was drawn from a live specimen
Courtesy: Public Domain via Wikimedia Commons

Steller's sea cows were discovered by westerners looking to hunt sea otters along the Aleutian Islands where food could be scarce. The scientist who first described them tells us that they ate more algae than sea grass, and that their forelimbs were curved instead of paddle shaped to allow them to pull themselves along in the shallows while grazing. What's particularly fascinating about these animals was just how big they were, some individuals were as long as an adult orca! That's a lot of manatee. Steller's sea cows were so slow, easily reached, and edible that they were gone about 17 years after their discovery. Sadly we'll never know if we did major detriment to this species while it was thriving in an isolated population, or if they were already nearing extinction naturally when we dealt the final blow. Fortunately there may still be time to save the sea cow's closest relative, the dugong (Dugong dugon).

Om Nom Nom Nom
Courtesy: Corrie Barklimore via Flickr

Dugongs (no, not the pokemon) are the most marine of the sirenia; meaning they spend all their time in salt or brackish (mixed salt and fresh) water. Their most noticeable distinction from manatees is their forked dolphin-like tail. Manatees have big, round, paddle-like tails that are useful for holding position in still water. While dugongs are wide spread across the tropical Indian and Western Pacific Ocean their populations are spotty, probably due to human alterations in their habitat. The largest herds live along the coast of Northern Australia and in the Arabian Gulf where sea grass beds are still large and healthy. The challenge for these sirens has been human development of beaches where sea grasses grow off shore. Unfortunately sea grasses grow off of exactly the kind of sandy, relaxing beaches humans like to put hotels and beach communities on. When land plants are taken away by construction; dirt and sand run into the nearshore smothering the prairies. Fertilizer runoff from agriculture and golf courses also causes quick-growing algae to out compete sea grass. So when you choose a place to stay during your tropical vacation, keep in mind the resort's potential impact on dugongs before you book a room.

Dugongs role as grazers is extremely important for sea grass prairies because they remove old grasses and fertilize new ones. As they browse, dugongs pull sea grass up by the roots creating noticeable  tracks of bare sand like someone set the lawnmower way too low. Like any herbivore dugongs make a lot of waste and as their poop falls into the furrows they've created in the grass it provides critical nutrients for the regeneration of the prairie.

Who else wishes it was possible to hire manatees to mow
your lawn instead of goats?
Courtesy: Ruth Hartnup via Flickr

The sirenian that is the next most comfortable in ocean is the West Indian Manatee (Trichechus manatus). West Indian Manatees are the most familiar and well-studied of all sirenians because they live in highly populated regions of North, Central, and South America. You may have heard of Florida and Antillean manatees in your travels, and those are legitimate, but they are names for distinct populations of West Indian Manatees. Antillean manatees are usually found in the Southern Caribbean, and Central and South America. You can probably guess where Florida manatees are most often found. For a deeper look at what makes a species, and how populations of one species can be distinct from one another without being totally different, check out the D&T posts "Celebrating Sculpin Speciation" and "Ghost Faced Killer (Whales)".

Most West Indian manatees split their time between fresh and salt water depending on the season. In Florida these manatees spend their winters huddled nears springs of warm water, and since the advent of modern electricity generation, the heated water outflows from power plants. As ocean temps warm up in the summer Florida manatees  spread out in search of lush prairies and can be found travelling as far north as Virginia! Interestingly, although as many as 500 manatees have been seen in one spot during the winter, they aren't particularly social. The mother-offspring bond is the strongest social connection in manatees. Young manatees will stay with their mothers for two years after they're born, learning where warm refuges and feeding grounds are located.

The green on his back is algae, kind of like the stuff that grows in sloth fur.
Courtesy: Keith Ramos via Flickr

The final two sirenians are the most river-adapted species, the Amazonian manatee (Trichechus inunguis) and the West African manatee (Trichchus senegalensis). Both can be found deep into large rivers in their respective continents. Amazonian manatees have stable populations as far up the Amazon water shed as Peru and Columbia, and West African manatees can be found living in lakes 200 miles inland from the sea. These manatees deal with particularly murky water compared to dugongs and West Indian manatees, so the sensitive bristles that cover all sirenians' bodies are especially important for finding food. It's kind of like if a cat had whiskers all over their body instead of just their face.

Yep, that's a baby Amazonian manatee. Commence squealing with delight
Courtesy: Harvey Barrison via Flickr

We know the least about African manatees because the humans of their homeland have struggled with colonialism and the unrest it often instills in the colonized. However, this chaos may actually benefit the manatees; as development in some countries where they're found has been slow. Without speed boats, big riverside properties, and erosion problems African manatees have fewer risks to their survival than sirens in more altered regions of the world.

Dugongs and manatees are one of the weirdest and most fascinating marine mammals on the planet. For every human that's encountered them it's as hard to resist the song of these sirens calling us to discover more about them. But unlike the sirens of Greek Myth, the lure of dugongs and manatees will bring every species to a healthier life and a richer planet.


Mayaba, Theodore B., Kamla, Aristide T. & Self-Sullivan, Carlyn, "Using Pooled Local Expert Opinions (PLEO) to Discern Patterns in Sightings of Live and Dead Manatees (Trichechus senegalensis, Link 1785) in Lower Sanaga Basin, Cameroon", PLOS ONE, July 21st, 2015.   

Satizabal et Al., "Phylogeography and Sex-Biased Dispersal Across Riverine Manatee Populations (Trichechus inguinus and Trichechus manatus) in South America", PLOS ONE, December 20th, 2012.

Sulzner et Al., "Health Assessment and Seroepidemiologic Survey of Potential Pathogens in Wild Antillean Manatees (Trichechus manatus manatus)", PLOS ONE, September 12th, 2012.

Macdonald, Nicole, "Dugong dugon- Dugong" Animal Diversity Web. Accessed via:

Weinstein, Brett & Patton, James, "Hydrodamalis gigas- Steller's Sea Cow", Animal Diversity Web, Accessed via:

Sunday, February 12, 2017

Home, Home 'Neath the Waves

Oh give me a home, where the buffalo roam,
and the deer and the antelope play,
and seldom is heard, a discouraging word,
and the skies are not cloudy all day

The classic American folk song Home on the Range has been conjuring the American prairies in our imaginations for generations. For many, the John Denver version is the seminal cover of the song. As he sings you can see feel the warm breeze rippling the tall grass and flowers. Giant bison wade peacefully through the vegetation while waterfowl float on clear ponds nearby.

The only pie more American than apple may be the ones these guys 
leave behind after eating all that grass.
Courtesy: Ard van der Leeuw via Flickr

"But wait a minute! This is a marine science blog! Why are we talking about grass-lands?" Well imaginary snarky reader, the ocean is teeming with its own prairies. Even though they haven't gotten the same kind of press as coral reefs or kelp forests they're absolutely essential habitats. And underwater prairies are every bit as idyllic and wild as their terrestrial compatriots.

Oh give me a home, where the manatees roam,
and the snails and the isopods play,
and often is heard, the cries of seabirds,
and the waters are calm in the bay.

"Stay away from Washington State. It's terrible. There's nothing beautiful
 or interesting to give you any reason to move here ever." -Washington State Motto
Courtesy: EcologyWA via Flickr

The dominant organism in any prairie, above or below water, is grass. Though we tend to lump every under water photosynthesizer together as "seaweed"; sea grass is remarkably unique. Other "seaweeds" are algae, which is a group of plant-like organisms that doesn't have roots, lacks veins for transporting nutrients, and makes spores instead of seeds. Sea grass is a true flowering plant, just like the grass on your lawn, except this is the only flowering plant able to survive under salt water!

Algae typically grows on hard surfaces because its holdfast needs something stable to cling to. Sea grasses need soft substrate, usually sand, where their roots dig in and actually stabilize the soil. They have what are called rhizomaceous (pronounced: ry-zo-may-shus) roots which means they spread out horizontally in a net and put out new shoots where there's enough light. Anyone who's pulled ivy by hand has experience with these kinds of roots. The rhizomes of sea grass cover so much ground and hold so much soil that they're a major protector of coastal shorelines from erosion. In the Caribbean, Western Atlantic, and Gulf of Mexico where they're called turtle (Thalassia testudinium) or manatee grass (Syringodium filiforme); sea grasses keep hurricanes from washing beaches used by sea turtles and tourists alike out to sea. Grasses on the American plains once did the same thing for the land by protecting the earth from the harsh prairie winds. Losing all that grass to agriculture caused the Dust Bowl of the 1930's.

 But tell me again how humans can't affect major changes 
on the environment.
Courtesy: US Department of Agriculture via Flickr

Only 200 years ago the tall and short grass prairies of the American West were rich with a diversity of animals that thrived on the variable habitat provided by the grasses. Insects of all kinds, burrowing rodents, birds and even terrestrial crayfish skittered and survived among the blades. Sadly most of these habitats have been lost to agriculture and suburbanization, but sea grass plains have avoided these disturbances and still host an incredible diversity of organisms.

Sea grass creates vertical habitat just like trees do in forests; so many species can grow on, in, and around the grass. One study in Denmark found more than 200,000 organisms of 86 types on a little more than 1,000 blades of grass. The folks doing the research even found entire tiny ecosystems on the blades. Diatoms, a kind of single-celled algae, grew in mats on the leaves. Isopods, a relative of crabs and shrimp, would walk along and graze on the algal mats. The tiny crustaceans were eaten in their turn by small anemones that also attached themselves to the grass.

We've recently discovered that these minuscule animals may actually benefit the sea grass as well. Sea grasses have male and female flowers just like terrestrial plants, and just like terrestrial grasses males release pollen that has to get into the female flower some way or another. On land, pollen is transported by the wind and by animals that travel between plant flowers. Until recently we assumed sea grass pollen was only transported by waves and currents. But we've found evidence that planktonic baby crabs, and nearly microscopic, bristly, worms are actually acting as pollinators for sea grass. These plankton visit male flowers where pollen grains get stuck on the appendages that normally help prevent the animal from sinking. Then they swim along to the next flower in search of food and inadvertently pollinate the female. I don't have the right permissions to post a picture of the pollen grains on the plankton, but you can see the incredibly cute pictures in the article at this link.

This species, called tape grass (Enhalus acoroides), is found in Asia.
The male flowers (white nubs) float way from their parent, and get 
caught in the female flower (yellow petals).  
Courtesy: Ria Tan at Wild Singapore via Flickr

The abundance of grass and wealth of small animals inevitably attracts larger animals to these rich feeding grounds. Like lions on the Serengeti or wolves in Yellowstone; seals, sharks, and other big predatory fish move through sea grasslands to consume the smaller predators drawn by the smorgasbord. Of course it wouldn't be a grassland without big grazers. North America and historically Europe have bison, Asia and Africa have rhinos and buffalo, Australia has kangaroos, and South America: llamas. The plains of the ocean: manatees, dugongs and sea turtles.  Sea grasses also bring in the massive assemblages of birds that are often seen on prairies. The coolest of these is probably the brant (Branta bernicla).

Courtesy: JimGain via Flickr

In Europe, brant are called Brent Geese, presumably because the name Brent is used exclusively to identify obnoxious frat bros in the US. They're an incredible relative of the more familiar Canada goose (Branta canadensis), and they cannot survive without sea grass. The Pacfic's subspecies, the black brant (B.b. nigricans) summers on the north slope of Alaska and the islands to the north where their chicks can develop relatively free from predators. As the year wanes the brant are chased south by the frigid nights of winter. But brant aren't like the many marathon flyers that breed in the arctic. Brant have such a big body relative to how small their wings are that they can't make a trip from Alaska to to the southern hemisphere in one go like a bar-tailed godwit. Brant have to take pit stops the whole way from Prudhoe Bay to Baja to rest and refuel, and what do they look for en route? Sea grass.

The sheer abundance of eel grass (Zostera marina), as we call it on the west coast, makes it the perfect resource to gas up on. Eel grass is found all along the migration route, and because the blades are coated in organisms, the herbivorous goose probably gets much needed proteins and fats for energy. 

"Waiter, there's a bunch of bugs on my salad. <Chomp, chomp, chomp> 
Actually never mind, don't worry about it."
Courtesy: Jon. D. Anderson via Flickr

Brant are the ideal illustrator of how important and powerful something as commonplace as grass can be. A good sea grass prairie produces so much food that it can attract an entire population of animals. We believe that every single black brant stops at Izembek bay in Western Alaska, which has the largest eel grass bed in the world, on their way north and south each year. And just like their Canadian cousins that settle over the prairies of the US interior during the winter brant show us the soothing wildness of grasslands. It's just too bad John Denver didn't SCUBA dive.

Oh give me a home, where the manatees roam,
and snails and the isopods play,
and often is heard, the cries of seabirds,
and the waters are calm in the bay.


Ganter, Barbara, "Sea Grass (Zostera spp.) as Food for Brant Geese (Branta bernicla): An Overview", Helgoland Marine Research, vol. 54, pg. 63-70, 2000.

DeAmicis, Stacey & Foggo, Andrew, "Long Term Field Study Reveals Subtle Effects of the Invasive Alga Sargassum muticum Upon the Epibiota of Zostera marina", PLoS ONE, September 14, 2015.

Thormar et Al., "Eelgrass (Zostera marina) Food Web Structure in Different Environmental Settings", PLoS ONE, January 11, 2016. 

Tussenbroek et Al. "Experimental Evidence of Pollination in Marine Flowers by Invertebrate Fauna", Nature, vol 7, 2016.
Accessed via:

Sunday, February 5, 2017

I Love It When You Call Me Big Papa

Whether you love him, hate him, or don't care either way; Barack Obama's presidency ended on January 20th. While the 44th president has had a rough time forming a lasting legacy on many fronts; he's proven himself to be the public lands president. Since taking office in 2009 Obama has set aside more land, and even more relevant to Depth and Taxa, ocean than any president in history.

Obama is basically that kid in school who trashed
the curve for everyone else.
Graph based on National Park Service Data

There's a number of ways that land and sea can protected from exploitation in the US. Areas can be set aside as National Parks; which basically prevents them from use other than research and outdoor recreation. Lands can be established as National Forest; which has a conservation aspect but also allows for some extraction of resources. However both of these designations require action by Congress. Action is not something the 114th Congress was famous for. So if a president believes the people that elected him want lands protected, but can't get congress to do anything, how does he go about it? Enter the Antiquities Act.

In the final years of the 19th century Americans were concerned about the rampant destruction of archaeological sites and ecosystems across the country. In response, Congress created the Antiquities Act to allow important cultural, historical, and scientific places to be protected as National Monuments; without the delay that comes from congressional deliberation. Unsurprisingly, Teddy Roosevelt used the act to set aside more acreage than any president until his fifth-cousin took the job in 1933.

"Hahahaha, just try and outdo me little Frankie. I'm the only 
president  this century that everyone liked." -Teddy Roosevelt

You might expect that Democratic presidents are more likely to use the antiquities act, but the exact same number of Democrats and Republicans have established or enlarged National Monuments. In fact, one of the largest ever national monuments was established by the number two acreage protector, none other than George W. Bush! The Papahānaumokuākea (pronounced: papa-ha-now-mo-ku-ah-kay-ah) National Monument was established in 2006 by president Bush and expanded by over 400,000 square miles in 2016 by president Obama.

Papahānaumokuākea (Or for Notorious B.I.G. fans: Big Papa) hits every mark for the intent of the Antiquities Act. It has important historical sites; like Midway Atoll where the Allies scored a major naval victory in World War II. Culturally important places to indigenous Hawaiians. The northwest islands in the monument are believed to be where spirits are born and return to after death. And major ecologically and scientifically important ecosystems. Shallow and deep water stony coral reefs, breeding grounds for endangered species, islands full of endemic plants and animals, and a sea mount as high as Mount Rainier are all found inside the monument.

If we place Papahānaumokuākea on top of the US it's as long as Idaho to Indiana
and as wide as Montana to central Utah.
Image Courtesy; NOAA

Not only does Papahānaumokuākea represent the ideal of what a national monument should be; the restriction it puts on commercial fishing, but not recreational fishing, comes at an essential time in the health of the ocean. There's a growing consensus that about 30% of the world's seas needs to protected from large-scale fishing if we want to continue to feed humanity with good, healthy protein.

 Currently less than 2% of the ocean is covered by marine protected areas, so there's lots of work to be done. Fortunately we already have some guidelines on what makes for an effective marine protected area. One standard uses what are called NEOLI features to plan and assess successful marine protected areas. NEOLI stands for: "No-Take, Enforcement, Old, Large, and Isolated". If a protected marine site can meet four of those five features it's likely to be successful in promoting biodiversity, and in allowing fisher people to collect better catches with less effort at the edge of the protected zone.

"What's that about catching more fish with less effort!?" -This Hawaiian Monk Seal
Courtesy: Dr. James P. McVey, NOAA Sea Grant Program. (NOAA Photo Library: anim0290) 

Obviously Papahānaumokuākea meets the "large" standard, but how's it do in those other areas? Papahānaumokuākea isn't a no-take zone because recreational and sport fisheries are still able to get permits to use the area. However, the scale of recreational fishing is so small relative to commercial fishing that this represents a potentially huge cutback in the amount of harvest within the monument. And before you get frustrated that small scale commercial fishers will be going out of business there's great news. Research has shown that when areas are protected from fishing, species tend to repopulate the protected area and spill over into fishing sites. The edges of the protected area usually have more numerous, larger, and healthier fish than areas far from any protected zone.

Of course no-take doesn't matter if you don't have strong enforcement. This is where Papahānaumokuākea will probably struggle most to meet the standards for protection. The monument is managed by a partnership between the federal and Hawaiian state governments. Hopefully a strong realtionship between these parties will be able to monitor such a vast area. Thankfully some very cool systems are coming online in the near future to help countries protect their natural resources. The Pew Charitable Trusts have developed an incredibly cool program called: Project Eyes on the Seas that uses satellite images, vessel GPS transponders, and home port data to police marine protected areas for relatively cheap.

       Bad Boys, Bad Boys, What'cha Gonna Do? What'cha Gonna Do,
When They Come Fo' You!?
Courtesy: Tony Hisgett via Wikimedia Commons

Now obviously any newly expanded or created national monument isn't going to be considered "old". However, Papahānaumokuākea meets the last NEOLI standard by being isolated from cities and continents, and so thankfully hasn't historically been heavily impacted by human activities. Because exploitation has been limited, Papahānaumokuākea has many of the features we normally associate with old marine protected areas. In fact, in the deep channels between the islands, atolls, and sea mounts of the Hawaiian chain live black corals that have been growing in the same spot for 4,000 years.

Using the NEOLI standards, it looks like Papahānaumokuākea has the potential to help the ocean recover from our historical transgressions, and to provide for humanity in the future. Good environmental policy is about finding balance; meeting the needs of many while protecting the most vulnerable. The ecosystems that produce the natural resources we need have to be kept intact if they're to continue to provide raw materials, jobs, food, inspiration, and a connection to something larger than ourselves. National Monuments like Papahānaumokuākea are an important part of the land-use mosaic that allows the United States to provide the best life for its citizens.

The incoming administration has expressed a focus on the harvest and materials side of the benefits of the environment. An extractive management style may put places like Papahānaumokuākea at risk of having their protections revoked. Both goat farming hippies and doomsday preppers can agree that people have the right to survive off the land. If we can work to remind everyone that all the materials of our modern lives originated from, and are replenished in, pristine ecosystems; then places like Papahānaumokuākea will have a better chance of remaining unaltered. Let's work together to build a broad coalition of people who know the value of functioning ecosystems.


Roberts, Callum M., Hawkins, Julie P., & Gell Fiona R., "The Role of Marine Reserves in Achieving Sustainable Fisheries", Philosophical Transactions of the Royal Society B, Vol. 360 pg. 123-132, 2008.

Bruckner, Andrew, De Angelis, Patricia, & Montgomery, Tony, "Case Study for Black Coral From Hawaii", Non-Detriment Findings Case Studies, WG 9- Aquatic Invertebrates, Case Study 1, Meeting of the IUCN 2008. 
Accessed via:

Edgar et Al. "Global Conservation Outcomes Depend on Marine Protected Areas with Five Key Features", Nature, Vol. 506, Pg. 216-229, Feb. 13th 2014.
Accessed via:

Long, Tony, "How Satellite Monitoring is Helping Catch Bad Actors", Pew Charitable Trusts Research & Analysis Online, March 7th 2016.
Accessed via:

US Congress, "American Antiquities Act of 1906"
Accessed via: