Corals 101

I don’t know a single person that does not like the looks of a coral reef. Personally, I love them. In university, I wrote my Bachelor thesis on coral reef ecology, even though I had never seen a coral with my own eyes...but last September that changed when I was on Zanzibar! I made 2 dives there, and finally got to see a lot of real life corals. It was awesome.

There is so much to say about corals that I am going to split it up in several posts. For today we’re gonna stick with the basics. What is a coral? What does it look like? What does it eat? What kind of corals are there? Where do you find them?

What a coral looks like on the inside

A coral is an animal (you have no idea how long I lived with the idea that they are plants!) that consists of a polyp (basically a sac-shaped animal) that is housed in a hard external shell to protect the polyp (Pinet, 2009). The polyp has an opening at the top, that functions as his mouth as well as his anus. I know. Gross. I’m glad we got rid of that system somewhere along the evolutionary line. 

Around this opening you find tentacles (like in anemones) with special cells that sting (nematocysts), and cells that produce a slimy substance to trap prey. Corals are fixed to the ground, so they cannot actively chase their prey. Instead, they have to wait for tiny bits of plankton to drift into their tentacles. Not the most efficient way of feeding you’d think, but apparently it works, because corals have been around for about 200 million years!

Plankton!

Plankton?

There are two kinds of corals: corals that have a pact with tiny plant cells, and live in tropical seas (hermatypes) and corals that do not have these tiny plant cells, and can live in deeper, cooler waters (ahermatypes).

The corals of the former class are the types that build the impressive reefs we like to see so much. If you put one of these corals under a microscope, you will find plants of just 1 cell big (zooxanthellae) that live in the outer layer of the coral’s flesh. What is this pact they made? For the plant cells, living inside the coral gives them a safe and stable environment, and they get their food from the waste that the coral produces. In return, the plant cell does its magical photosynthesis thing (making oxygen), providing the coral tissue with oxygen, and when it uses the waste products of the coral, it protects the coral from potential toxic products. And very generous of the little plant: if there is not enough food for the polyp, it can digest the plant cells that live inside it (Pinet, 2009). 

Because the zooxanthellae need sunlight for photosynthesis, these corals can only be found in shallow, warm waters. The optimal water temperature for a hermatypic coral is 20°C (Pinet, 2009). Another environmental aspect that controls how well corals grow, is the turbidity of the water. If the water is very muddy, all those little particles block the sunlight, and that means that the plant cells cannot produce enough oxygen for the coral.

Where to go to find corals

The corals of the second class do not have plant cells living in their tissue, so for their food they are completely dependent on whatever swims/floats into their tentacles. Lucky for them, they are not restricted to the nutrient poor, warm, shallow waters of the tropics. Cold water corals are not dependent on penetrating sunlight for their zooxanthellae, and they can grow in temperature ranges as low as 4° to 12°C (Murray Roberts et al., 2006). These temperatures are mainly found in the shallow waters of higher latitudes, and in the deep open ocean. In these colder waters, there is much more plankton available for the corals to feed on, so even without zooxanthellae to help them out, cold-water corals are still perfectly capable to feed themselves.

In general, coral reefs are very species rich environments (Snelgrove, 2010) compared to other parts of the ocean. This is because coral reefs can become very complex structures, with many holes and corners for animals to hide in. A very attractive feature for most animals, because living in the open sea isn't exactly what you call safe...So a lot of small and large fish and invertebrates find their shelter on a coral reef, creating an ecosystem that is so diverse it gets called 'rainforest of the ocean'. I like that. In my head I immediately create this image of huge trees under water, and all the fish swimming between the branches. 

Unfortunately, just like the real rainforests, the underwater versions are not doing so well...A lot of the reefs around the world are dying, and more than two thirds of coral reefs are in a bad condition. I really hope we can stop it from getting worse, because what would we do without them?!

Rainforest of the ocean

References:

Murray Roberts, J.; Wheeler, A.J. and Freiwald, A. (2006) Reefs of the deep: the biology and geology  of  cold-water coral ecosystems. Science, 312, 543-547.

Pinet, P.R. (2009) Invitation to Oceanography (5th ed.). Sudbury, MA: Jones and Bartlett Publishers.

Snelgrove, P.V.R. (2009) Discoveries of the Census of Marine life. Cambridge: Cambridge University Press.

Pictures:

Top: http://www.wired.com/images_blogs/wiredscience/2012/12/coral_reef.jpg

Polyp: https://www.e-education.psu.edu/earth103/files/earth103/module07/polyp_with_zooxanthellae.jpg

Polyp 2: https://genefish.wikispaces.com/file/view/coral_polyp.jpg/107854669/coral_polyp.jpg

Plankton: http://australianmuseum.net.au/Uploads/Images/7566/e004_big.jpg

Map: http://www.grida.no/images/series/rr-in-dead-water/Figure07.jpg

Coral reef: http://www.annefontainefoundation.org/sites/annefontaine-pny.cmsloungesvn.com/files/Great-Barrier-Reef-Holiday-Reef-Fish12.jpeg

The Pacific Garbage Patch

You may have heard about it…the giant patch of plastic in the Pacific Ocean. 

I first got to know about this through a guest-lecture at my university in Wageningen (in the Netherlands). To be honest I don’t remember much of what he talked about, it was 6 or 7 years ago, but it did make an impression. He showed pictures of birds (dead) with their stomachs full of plastic bits, giant patches of plastic bottles floating about in the ocean, pretty shocking stuff for a biologist (or anyone else I guess). 

So, what’s up with this plastic garbage patch? 

The garbage patch I am talking about here, is located in the Pacific Ocean. Or actually, there are two garbage patches. One is located east of Japan (the Eastern Garbage Patch), and the other one is located just north of Hawaii (the Western Garbage Patch).  Each patch is double the size of the state Texas, and is about 10 metres deep. The Pacific Ocean might be big, but this is more plastic than it can handle! 

How does all this plastic end up in these specific places, you’re thinking? 

A bit of basic oceanography. In all the oceans you will find currents. There are big currents that connect all the oceans together, and from these big currents spring smaller currents within each ocean. These currents are called gyres, and they are caused by differences in pressure, temperature and salinity of the water, and the wind. When the wind makes contact with the ocean surface, the water is set in motion. If the wind persists for long enough, this motion descends through the water column, causing a spiralling current (called the Ekman spiral) (Pinet, P.R., 2009). And it is these Ekman spirals and gyres that cause the plastic to collect in these garbage patches. See the yellow dots in the map? That’s plastic. Now the plastic starts moving, following the white arrows on the right and the blue ones on the left, and the Ekman currents and winds keep it all in place (click the map to go to the website for an animated version). 

Gyres in the Pacific Ocean

Plastic is an anthropogenic (man-made) kind of garbage. It is estimated that 80% of plastic in the oceans comes from sources on land, and the other 20% come from activities on sea, such as fisheries, cruises, and shipping (Lebreton et al, 2012). The debris consists of pretty much anything plastic you can think of. Bottlecaps, toothbrushes, floating fishnets, bottles, and tiny bits of plastic (Hoshaw, L. 2009). Just try to think of how much plastic you deal with every day…your food is wrapped in it (lots of it for some reason), your computer has plastic in it, your phone, cars. And plastics are not easily biodegradable, which is why all that plastic is floating there in the Pacific Ocean, and why the patches keep growing. 

When we have a closer look at what plastics the patch consists of, there are the macro-plastics (the bottles, toothbrushes, bottlecaps etc) and the micro-plastics (tiny particles of plastic). What we see in all the pictures are mainly the macro-plastics. The birds with their stomachs full of plastic bits, a turtle with a plastic ring around its shell, littered beaches full of plastic. 

Photo by Chris Jordan

But it's the micro-plastics that are the major constituent of the garbage soup. And despite them being so small, they are dangerous! Because of their size the particles are mistaken for food by marine organisms, and they get ingested by the animals. The composition of the particles makes it easy for pollutants in the water to attach onto these mini-plastics (Cole et al, 2011). This is chemics, and I am not good at that, so I am going to take the scientists word for it here...A lot of the pollutants are toxic for animals (and humans), so by ingesting the plastic bits, fish, dolphins, and us humans, accumulate the toxins in their bodies, which is obviously not a very healthy business to be doing. 

Why does this garbage patch get so little attention? First of all, until not too long ago we were simply not aware of its existence. The Pacific Ocean is immense. Until captain Charles Moore came across it with his crew in 1997. 'It seemed unbelievable, but I never found a clear spot. In the week it took to cross the subtropical high, no matter what time of day I looked, plastic debris was floating everywhere.' (Moore, 2003). Secondly, because it's so far away. If a problem is not directly on your doorstep, it is quite easy to think: this is not my concern. But it is! Since the discovery, efforts to raise awareness have increased. But still, you don't hear much about it, until you start looking for information. The problem certainly has not become any less since captain Moore discovered it...we keep producing more plastic every day, and it won't break down or disappear by itself. 

So is there anything we can do? Fishing out all the macro-plastics seems like an idea...but men, that would take ages! What would you do with all the plastic? And who would pay for it? Even if all this works, there is still the issue of the micro-plastics. Much more difficult to target...then I remembered a Tedx Talks video that appeared on my facebook feed a while back. I am impressed! This guy (he is quite young) has some really interesting ideas. It's still a project of massive proportions, but he makes it sound like there might be a solution. We're not there yet. His concept is promising, but they are still studying the feasibility of it. I hope it works, and that there will be enough investors to make it happen once he gets to that point. 

In the mean time: put your garbage in the bin. Just like that, we already help.

References:

Hoshaw, L. (2009, November 10). Afloat in the ocean, expanding islands of trash. New York Times

Lebreton, L.C.-M., Greer, S.D., and Borrero, J.C. (2012) Numerical modelling of floating debris in the world’s oceans. Marine Pollution Bulletin, 64, 653-661.

Moore, C. (2003) http://www.fvrd.bc.ca/InsidetheFVRD/MeetingsAgendasMinutes/AirQualityandEnvironmentManagement/Archived%20Agendas/2010%2003%2002%20Environment%20Committee/item%206.2%20-3%20Email%20re%20Recycling.pdf

Pinet, P.R. (2009) Invitation to Oceanography (5th ed.). Sudbury, MA: Jones and Bartlett Publishers.

Other websites:

http://www.greenpeace.org/international/en/campaigns/oceans/pollution/trash-vortex/ 

http://response.restoration.noaa.gov/about/media/where-are-pacific-garbage-patches.html

Let me introduce to you all...me!

I am new to this. I am going to be honest about that. 

Start at the beginning? 

I have a Master degree in Applied Aquatic Biology from the University of Portsmouth (UK). 

My passion for the sea and everything that lives in it, is old. As a child, I was all about dolphins. My first school project talk was about dolphins, my walls were covered with dolphins, I had a dolphin watch. I remember my dream job was to be a dolphin trainer. So not to the surprise of many, I chose to study biology and focus on everything marine. But to the surprise of many, I did not study dolphins, or any marine mammal for that matter. It's the fish that got my full attention. Small, big, dangerous, poisonous, weird looking, colourful, name it and I can pretty much guarantee you I like it!

For my final research project, I studied the behaviour of the blue cod (Parapercis colias) amongst each other. So, what happens when there is food present? Will they fight? Are the big ones in charge? Is size important at all? I spent hours (probably more close to days or weeks) watching under water videos of blue cod around a food source, looking for patterns in their behaviour. The crazy thing? I didn't even get bored...I think I surprised myself and my supervisor with that. Right now, we're still writing everything up to be published (still can't believe there will be a paper with my name on it! Big thing for scientists-to-be).

Why this blog? Because I think knowledge should be spread. And most scientific studies aren't that easy to understand. So with this blog, I want to try and make science a bit more fun for everyone. Sometimes I'll discuss interesting papers, explaining them in 'normal people' language, other times I'll just write a post about a species that caught my interest, or something marine related that was in the news, or whatever I can come up with.
I am not the best writer in the world, I know this. I've been told I write the same way as I tell a story, so if you like story-telling, you might enjoy my writing style! My goal isn't to become a writer, I write because I want people to get excited about fish, dolphins, whales, and everything else in the oceans. I want people to know more about these things.

I hope you will enjoy my blog!

The fish of my project: blue cod (photo is taken by my supervisor)