A Sea Lion Story

By now it's probably come across your computer screen at least once. The story may have even shown up in your physical paper. More than 1,800 California sea lion (Zalophus californianus) pups have shown up emaciated on the beaches of California since January. Unusual mortality events like this are most troubling to us because it's adorable baby animals that are suffering, so it's a good opportunity to draw awareness to ecosystem scale issues.

D'aww who's a good vector for a better understanding

 of ecology!? You are, yes you are!

Courtesy: Jaina via Flickr

So what do baby sea lions have to do with the ecosystem as a whole? Well ecosystems are all the living and non-living things in an area that interact with one another. This means that every piece in an ecosystem is significant to the others in some way. For example small fish are important to large predators, currents are important to plankton, and temperature is important to everyone. Each piece has direct effects on the others and those effects themselves interact.

On the surface (pun intended) starving sea lion pups seems to have a pretty straightforward cause. You would assume it's because there isn't enough of whatever it is sea lions eat. That's part of the story, but there's more to it. When baby seals and sea lions are first born they lack the thick blubber of their parents. Pups have to drink extremely rich milk to bulk up enough to survive on their own. California sea lion milk averages about 35% fat, that's about the same fat content as whipping cream, and about ten times the fat content of whole milk. Not only does the thick layer of blubber the pups develop help keep them warm it's important as an energy reserve when they first strike out on their own.

Despite what this sea lion seems to be telling you, Cronuts are not 

a viable source of energy reserves.

Courtesy: Makitani via Flickr

The most important prey for lactating mothers are anchovy, sardine, and hake. These fish live in large schools, so they're usually plentiful and they have extremely oily flesh; perfect producing rich milk. In the past there were very large fisheries for these species off of California. Think Cannery Row on Monterey Bay. However, we aren't taking too much of the sea lions' food away anymore because canned, oily fish have declined in popularity.

I can't imagine why...
Courtesy: dr.coop via Flickr

 What's happened is that for the last few years the waters around the Channel Islands, where the sea lions give birth, have been abnormally warm. Each of the fish the sea lions rely on are cold water species, in fact North Pacific anchovy won't go into water warmer than 62 degrees F. Since California's seas have been so warm the food fish have shifted themselves to colder waters. Sardines have been spawning farther offshore and other fish schools have moved north. These migrations have forced mother sea lions to hunt farther afield, and when their moms don't come back for extended periods of time, the pups set out on their own too early.

So where are the dad's in all this? Why don't we see adult males stranding in California? Well they're not there. Male and female sea lions both take on long migrations from British Columbia to California and back every year, but they have different schedules. Females head down to the breeding grounds first to give birth. Then males head down to meet up with the females once they're ready to mate again; about three weeks later. Being further north for longer has actually lead to boom times for male sea lions. At the mouth of the Columbia river between Washington State and Oregon more than ten times the usual number of males have been hanging out. They came in for this year's copious smelt run and are fattening up to make the trip south to the rookeries. Males need a lot of mass and energy reserves to defend territories on beaches which they won't leave and thus don't eat for several weeks.

   "I'll calm when I haven't gone twelve days without food!"
Courtesy: Bridget Samuels via Flickr

So that's the story. Warm water pooling at the surface has pushed forage fish away from the Channel Islands. This means that female California sea lions have to travel farther to find food that makes rich enough milk for their babies. These longer trips mean that many young are leaving the rookeries too early, and are washing up along the shore. All the while, farther north, males are enjoying a greater supply of food than ever. The biological needs of its inhabitants, and the physical characteristics of the ocean come together to tell the complex story of an ecosystem as long as a continent. We're able to discover the changes happening in the environment thanks to this single species.

Scientists aren't sure if the warming is caused by the changes happening to the global climate system, or if this is part of natural variations of the Pacific. Either way marine mammal stranding networks will need support in the near future. If you want to help one of the best things you can do is to remain informed about who's best prepared to help hungry or sick sea lion pups. There's a good list of organizations to contact and a lot of information here.

References:

"California Sea Lion (Zalophus Californianus)", NOAA Fisheries: Office of Protected Resources. Accessed via: http://www.nmfs.noaa.gov/pr/species/mammals/pinnipeds/californiasealion.htm

Bernton, Hal, "Boom Times on the Columbia for California Sea Lions", The Seattle Times, March 27th, 2015, Accessed via: http://www.seattletimes.com/seattle-news/boom-times-on-the-columbia-for-california-sea-lions/

"2013-2015 California Sea Lion Unusual Mortality Event in California", National Marine Fisheries Service Health and Stranding Reports,
Accessed via: http://www.nmfs.noaa.gov/pr/health/mmume/californiasealions2013.htm

Redman, Marianne, "The Pinnipeds: Seals, Sea Lions, and Walruses", pg 282, University of California Press, 1990.

Orr et al., 2011, "Intraspecific Comparison of Diet of California Sea Lions (Zalophus californianus) Assessed Using Fecal and Stable Isotope Analyses", Canadian Journal of Zoology, 89:109-122. 

The Great Pacific Garbage Chowder

The Great Pacific Garbage Patch: it's flashy, disturbing, simple, a great band name, and... is completely misleading. That name was given to an area in the Pacific ocean by Curtis Ebbesmeyer when a colleague reported on the amount of floating plastic in the area. Because the name is so catchy it stuck, and has been used extensively in popular media reports ever since. So what's it look like? Well prepare yourself, below you're going to see a picture from the very heart of this trash zone that's been described as having a surface area twice the size of Texas.

Where's all the garbage?
Courtesy:  ---=XEON=--- via Panoramio

The problem with the term patch is that it suggests a covering, like in a patch of grass; or a lot of big pieces, like in a cabbage patch. Neither of these is what you see in these areas. Really what's happening is that giant ocean currents, called gyres, are concentrating tiny bits of plastic (called microplastic) in their middles. The gyres are more like plastic chowder than a plastic patch. And just like in a chowder the chunks aren't evenly distributed. Different types of plastic have different densities, so they float at different heights in the water column or even sink to the bottom.

This is the North Pacific Gyre. There are two major gyres in the Atlantic and Pacfic,
 and one in the Indian Ocean
Courtesy: NOAA Ocean Service's Making Waves podcast

So why isn't the plastic more evenly distributed, or at the very least why isn't it close to land? Well it has to do with the fact that the gyres are circular currents. When particles sit in water they are partly held up by how fast the water is moving. In swirling water, like the gyres or a cup of tea being stirred, the water at the center is moving slower than the water at the edge. Particles catch on the slow water and are pulled into the center where they stay more or less still.

 Red sprinkles in water before, during, and after stirring: Some sprinkles float, others sink; all concentrate into the center; just like pieces of plastic caught in the ocean gyres.

There are a number of issues associated with plastic in the ocean, and all originate with the fact that plastic doesn't biodegrade. Plastics are designed to last forever; they're stable, cheap, and sturdy. When we throw out plastic it never turns back into the minerals that it came from. Plastics just continually degrade into smaller and smaller pieces, but they stay plastic for functionally forever.
The first problem is that plastic takes up space. Several studies over many years have led to calculations of about 35,000 tons of microplastic and 250,000 tons of larger plastics in the oceans. All of those bits can easily lead to entangled marine animals.

The other big issue is that act of breaking down. As plastics break into smaller and smaller shards they're inadvertently gobbled up by smaller and smaller organisms, entering the food chain at more levels. While they're breaking apart and mixing around in the ocean, the chemically raggedy edges of the plastic grab onto many of the toxins commonly found in sea water. This takes those chemicals from their spread out, and therefore less dangerous, state to concentrated on one of these bits. Some of these toxins are hormone disruptors and there's a growing body of evidence that they can and will affect fish by changing their reproductive organs to those of the opposite sex.

Lastly, when plastic breaks down it becomes much harder to clean up. Imagine trying to separate all the parts out of real chowder, including the spices. Some of it can be picked out pretty easily, but others not so much. The microplastics are so small that we can't go out and grab it all because we'd have to screen the water with nets with really tiny holes. Nets with tiny holes are also how you catch plankton, so to catch the estimated 5 trillion bits of plastic out there we would probably decimate plankton populations.

"A few billion more of these and we can save and destroy the ocean at the same time"
Courtesy: NOAA Photo Library via Flickr

There's also the problem of some plastic sinking. For years surveys of ocean plastics weren't finding as much as researchers expected, but we knew that our waste was making into the ocean, so where was it all going? Well it turns out, straight to the bottom. A three ocean study of deep sea sediments has found significant amounts of microplastic fibers in the depths. A lot of these fibers were rayon and acrylic, materials found in synthetic clothing that probably got into the water from particles coming off as the clothes were washed.

Alright if we can't clean up everything then what do we do? Well the beautiful thing about this issue is that it's entirely in our hands. There isn't a single company or government that has caused all this pollution, so there's no one to fight with to make it stop. We are so powerful in this situation it's unprecedented. The most important thing is to stop using plastic like it has a short life. That tupperware you or your parents bought in the 70's and is still in your kitchen; that's how plastic should be used. Keep that sucker around forever and hand it down to your kids too. Those Legos that have been dropped, washed, stepped on, pummeled, and still haven't broken. Hell yeah that's my kind of plastic. Where you can, eliminate single-use products, and when you're out walking pick up a piece of litter each time. If we do these things we can make a dent in the 30% of all plastic that gets thrown away within a year.

I have to give credit to Edward Humes, author of Garbology for the term "plastic chowder" it really is a perfect metaphor.

References:

Cozar et al., "Plastic Debris in the Open Ocean", Proceedings of the National Academy of Sciences, Vol. 11 No. 28, 2013, DOI 10.1073/pnas1314705111

Accessed via: http://www.pnas.org/content/111/28/10239.full

Ericksen et al. "Plastic Pollution in the World's Oceans: 5 Trillion Plastic Pieces Weighing over 250,000 Tons Afloat at Sea", PLOS ONE, 2014, DOI 10.1371/journal.pone.0111913

Accessed via: http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0111913

Woodall et al, 2014, "The Deep Sea is a Major Sink for Microplastic Debris", Royal Society Open Science, 1:140317, http://dx.doi.org/10.1098/rsos.140317

Rochman, Chelsea, "A Story About Fish, Plastic Debris, and Sex", Deep Sea News, 2014,

Accesses via: http://deepseanews.com/2014/10/a-story-about-fish-plastic-debris-and-sex/

Humes, Edward, "Garbology", Ch. 5-6, Penguin Books, 2013