How corals stir up their world

Oh man, it's been way too long since I wrote something here...
And this is just a quick article I found, so no extended post. It's about the micro movements that corals make, and that it might give an idea of how coral reefs will react to changing oceans.

Soon! There will be an invasion of jelly fish here, I promise.

Plastic Soup: Progress!

In my first post about the plastic soup I posted a link to a TED talk by Boyan Slat. Well, it turns out his project is viable! How awesome is that!

Let's hope they get the money together sooner rather than later and continue this awesome project!





(personal note: great music in this video!)


Have a look at the projects website as well: http://www.theoceancleanup.com/the-concept.html

There's a link for a donation on there, in case you want to support!

People of the Coral Triangle

Interesting short documentary about fishing communities in the Coral Triangle. A bit more about cyanide and dynamite fishing, and lots of beautiful images!

True Facts: Cuttlefish

Honestly, have a look at any of this man's videos. I introduced him already in the post about the mantis shrimp, but it is worth checking out his other videos as well. Perfect for a 5 minute break from work ;)

SOS Corals

As I said before, there will be more about corals. So here we go. Today's topic is what threatens coral reefs. 

Coral reefs are interesting ecosystems for a lot of reasons. There are entire communities who rely on fish and other organisms found on coral reefs for a living, oceanographers and climate scientists use the health of coral reefs to get an idea of the health of the ocean as a whole, conservation biologists will always be interested in coral reefs because of the incredible range of organisms that live there, and for tourist companies the reefs are a very popular attraction for their customers.

Climate change: acidic, hot oceans

    Coral reefs do not appreciate changes  in the environment very much. Unfortunately for them, in the last decades the amount of carbon dioxide in the atmosphere has increased immensely, causing the oceans to become more acidic and warmer (Hoegh-Guldberg et al., 2007). Two changes corals find difficult to adapt to. A more acidic environment will weaken the calciferous skeleton that protects the coral which leaves the animal unprotected to predators, and more vulnerable to structural damage caused by storms and waves. You can compare the weakening of their skeleton to getting rid of lime scale by using vinegar to dissolve it...the same happens to the coral. Higher ocean temperatures will cause the zooxanthellae (remember, the little plant in the coral) to die, resulting in the ‘bleaching’ (losing their colours) of corals. Corals have a very limited tolerance to changes in temperature. If sea temperatures rise 1°C above long term averages in an area for a couple of weeks, mass bleaching will begin, leaving the coral reef scary devoid of colour and life (see the picture at the top). There have been many conventions to address climate change, and what should be done to avoid further deterioration of the current situation. The question is though if coral reefs can be saved at all, or if they have suffered too much already to recover from the damage done.

Dynamite fishing: destroyed corals
and dead fish

Not so safe fishing techniques: dynamite and cyanideClimate change is not the only threat to coral reefs. Some communities that depend on fishing for their livelihood, use methods that are devastating to the reefs. And over the past years, the demand for live fish for restaurants and aquarium hobbyists has been steadily increasing. The techniques some use to collect fish are not always in the best interest of the reef and fish, some methods aren't even legal...Can you imagine throwing dynamite on the reef to kill fish so they float to the surface? Quite clearly (I hope) this doesn’t only kill the fish, but also the structure of the reef and other organisms that happen to be in the neighbourhood. Or what about using cyanide to collect live fish for restaurants and aquaria? The cyanide blocks the transport of oxygen in the fish, causing an effect similar to carbon monoxide poisoning, temporarily stunning the fish, so they are easier to collect. Although sometimes the fishermen still have to use hammers to free the stunned fish from the reef. A nasty side effect of cyanide is that not only the fish get affected by the poison...the cyanides slow down the photosynthesis process in the zooxanthellae, causing the algal cells to die, which results in coral bleaching (Jones & Hoegh-Guldberg, 1999).  

Both these techniques are illegal pretty much every where, but it proofs difficult to put it to a complete stop. Local enforcement is not always very strict, and sometimes it is difficult for the local fishermen to think about the positive long term effects, if they can get money for those fish now.

Filtsy humanses

Cyanide fishing: stops photosynthesis in zooxanthellae

And of course, let's not forget another destroyer of coral reefs: the Tourist. Us humans like to see pretty things, and what is more beautiful than the impressive under water view of a coral reef? Or even better: take a piece of the coral home, so you have a memory of that beautiful place for ever. Or buy that nice coral you saw at the souvenir shop down the road. You can guess what is wrong here...if everyone starts taking pieces of coral home, or selling coral in their shop there won't be much left on the reefs. And what will be left is often destroyed beyond recovery. Another problem with diving tourism is that inexperienced divers are not always capable to keep themselves floating above the sea floor/coral reef, so they crash into it, damaging the corals and plants growing there. 

It doesn't have to be all bad news though...well managed, sustainable coral-based tourism can provide an alternative income to the poorer coastal communities, and at the same time will keep the reef protected and healthy. Besides better management of tourism, more marine protected areas are being implemented. Some of these protected areas will not allow any form of tourism, others will allow it only during a certain time of the year, or under very strict rules. 

I think coral tourism is something that we should try to develop into a sustainable business. People will always want to visit coral reefs and the beaches protected by the reefs, so if we find a way to develop sustainable tourism it should be possible to keep the reefs healthy, and at the same time provide the local community with an alternative income to illegal fishing. There you go: a solution for another threat as well!

There are obviously a lot of obstacles to overcome: what boundaries should be set to tourism? On what reefs can we allow tourism without causing too much disturbance? How do we reach the local community, making sure the money reaches them instead of major corporations? What about enforcement of the rules?

Think about those questions. Do you think we can make it a sustainable business? I sure hope so, because other wise we better start getting used to a world without corals...

References

Hoegh-Guldberg, O.; Mumby, P.J.; Hooten, A.J.; Steneck, R.S.; Greenfield, P.; Gomez, E.; Harvell, C.D.; Sale, P.F.; Edwards, A.J.; Caldeira, K.; Knowlton, N.; Eakin, C.M.; Iglesias-Prieto, R.; Muthiga, N.; Bradbury, R.H.; Dubi, A. and Hatziolos, M.E. (2007) Coral reefs under rapid climate change and ocean acidification. Science, 318, 1737-1742.

Jones, R.J. and Hoegh-Guldberg, O. (1999) Effects of cyanide on coral photosynthesis: implications for identifying the cause of coral bleaching and for assessing the environmental effects of cyanide fishing. Marine Ecology Progress Series, 177, 82-91.

Kennedy, D. (2007) Year of the Reef. Science, 318, 1695.

Pictures

http://sites.duke.edu/biology217_01_s2011_pv24/files/2011/04/coral-bleaching_pic.jpg (bleached reef)

http://celebrating200years.noaa.gov/visions/coral/image4_650.jpg (dynamite fishing)

http://www.practicalfishkeeping.co.uk/custom/images/medium/51d14cc83c6f7.jpg (cyanide fishing)

Close Up: Peacock mantis Shrimp

It looks like a shrimp. Why would I want to write about a shrimp? Well, this is kind of a bad-ass that goes by the name of peacock mantis shrimp. And who doesn't like bad-ass animals?

To set things straight from the start: not a peacock, not a mantis, and also: not a shrimp (closely related though). Guess they should have named it something else maybe.

Some quick facts:

Name: Peacock mantis shrimp (Odontodactylus scyllarus)

Size: 3-18 cm

Distribution: most species live in the Indian and Pacific Ocean between Africa and Hawaii, but the occasional mantis shrimp can be found in colder seas

Habitat: under rocks, burrowed in a hole waiting for their prey to come close

Food: clams, small fish, small invertebrates

What makes this creature more bad ass than, let's say, your average brown shrimp? Obviously the colours are more appealing (peacock part of the name explained). But that's not it.

First of all, they have incredible eyes that can move separately from each other. Each eye has 3 focal points, which means it can see depth with 1 eye where we need both our eyes to do that. And that's not all...they have 16 photo-receptors (light receptors). We have 3: blue, red and green. It is impossible to imagine what a mantis shrimp can see! They perceive UV and infra-red light, they can see polarised light (we can't), and they can see colours we don't even know exist. Pretty cool if you ask me.

Second of all. These creatures can throw a serious punch.

Under its body it has a club-like appendage that it uses to strike at prey (or enemies). It kind of looks like the legs from a praying mantis (explains mantis part of the name). And it's fast! About 50 times faster than the blink of a human eye. Can you imagine that? It strikes with such a force that it can break shells, and even thick glass. Yeah, don't put your finger near one, it hurts! 

And because it's informative and funny: True facts about the mantis shrimp:

Check out the other videos on YouTube by this guy. He's funny!

links used:

http://www.aqua.org/explore/animals/mantis-shrimp

https://img2.blogblog.com/img/video_object.png

http://www.funnyjunk.com/funny_pictures/4135381/Peacock+Mantis+Shrimp
https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjBM_ZpVW3LtmeIEP_ABHRW5fCEZGMWXmt1DVnX55TUKLPeMSNPdh99acaeqmjoEnJtkCO2ABR1omQotshI697O6m0dKC4I21UDK4GGcyT6vQz8pzx_erkDXG9xZPAiNnCZNP9Kai0PtS19/s400/Mantis-shrimp.jpg
http://www.ucmp.berkeley.edu/arthropoda/crustacea/malacostraca/eumalacostraca/royslist/species.php?name=o_scyllarus
http://phenomena.nationalgeographic.com/2014/01/23/the-mantis-shrimp-sees-like-a-satellite/

Desert in the ocean?

I've talked about coral reefs being the rainforest of the ocean, an oasis so to speak. That raised a question: Is there such a thing as a desert in the ocean? A place where you won't find a great abundance of life?

And the answer is: yes, such places exist. They are known as dead zones. Sounds dangerous. A dead zone is an area in the ocean that is oxygen-starved (Editors of e, 2008) and they are therefore also called hypoxic zones (hypo = under, oxic = with oxygen). If oxygen levels in an area drop below 2 mg/l, it qualifies as a hypoxic zone (Rabalais et al., 2002). 

Dead zones occur naturally in deeper parts of the eastern Pacific Ocean, in the Arabian Sea, and off West Africa (Levin et al., 2001), and some of these parts are permanently hypoxic or anoxic (no oxygen at all). In deep water dead zones there is not as much diversity of species compared to deep oxygenated waters. You need a very specific set of traits to be able to survive in oxygen depleted zones. But then again...the animals that are able to live there tend to show up in massive amounts, so there are still a lot of creatures to be seen down there (mainly worms, crabs, star fish, some shellfish) (Levin et al., 2001).

And then there are the dead zones that occur in shallow, coastal waters. The biggest ones are found in the Gulf of Mexico, the Black Sea and the East China Sea. The dead zone in the Gulf of Mexico is being studied the most, and a lot of the numbers I've used here come from research in that area.
The number of coastal areas where hypoxia occurs is increasing and seems to be driven by human activities (Rabalais et al., 2002). Hypoxia in shallow waters is caused by an overload of nutrients in the water, mainly nutrients such as nitrogen and phosphorus. These nutrients come from fertilizers used for agriculture, effluents of sewage systems, emissions of factories and cars, and they get flushed into river systems, eventually ending up in the ocean.

What happens next? There are 2 things required for hypoxia to occur (Rabalais et al., 2002). First of all, the water column must have different layers of water (stratified), so that the bottom layer is separate from the top layer. These layers are formed by differences in water temperature and salinity; cooler, saltier water = heavier, and forms bottom layer. If these layers have formed there is no (or little) transport of oxygen from one layer to the other. The second factor is the breakdown of organic material. The high amount of nutrients in the water causes a massive increase in phytoplankton (tiny microscopic plant like organisms), which results in more organic matter reaching the bottom sediments. There, the organic matter will be broken down by bacteria using oxygen (aerobic bacteria), leaving the water above the sediment depleted of oxygen. Decomposition of the organic matter also leads to a growth in microbial organisms, increasing the amount of oxygen needed to support the organisms (Diaz & Rosenberg, 2008). And this happens in an environment where oxygen is already scarce...

These steps are the first phase of hypoxia. In the second phase, the oxygen levels keep dropping, causing the mass mortality of benthic (on/in the bottom living) animals. These are mainly fish, crabs and oysters that need about 3 mg/l oxygen. Worms and clams in the sand only need oxygen concentrations of 1 mg/l, so they are still okay with living in most dead zones. Sometimes, even animals that can swim away won't make it. And then you might see horrible death scenes of thousands of dead bodies washed upon the beach, or floating at the surface. It's not a pretty sight, and I can only imagine the smell that must come with so many dead fish...
The third phase is characterized by hypoxia becoming a seasonal event. Very often hypoxia occurs in summer, when the temperatures are higher and there is explosive growth of phytoplankton (increasing the amount of organic matter, which leads to more decomposition...etc. phase 1 all over again). If the hypoxia sustains for years, the fourth phase can be entered where the dead zone can expand and the amount of oxygen will decrease even more, leading to an anoxic (without any oxygen) area (Diaz & Rosenberg, 2008). 

All these changes, deaths, and animals leaving the scene to find a better place to live, will eventually cause a change in the ecosystem structure and functioning. And that in turn will affect the way we can use these ecosystems. A lot of the dead zones we know are important economical fishing grounds. So if the animals disappear from there, or are in a bad condition because of the water quality, that for sure will affect fisheries, resulting in less fish (or bad fish) on your plate.

I always like to finish on a note of 'think about what you're doing'. This is a big problem. We can't solve it over night, but maybe just stop and think about it for a second when you fertilize you garden, or step in your car (for a 5 minutre drive to the supermarket?), or flush something chemical down the drain. Think about where it ends up, and what it does to the oceans.

I know this was kind of a tough post, oxygen levels aren't the most exciting thing to write about...but I definitely learned new stuff writing this, and I can only hope I got the information across without boring you to death!

References:

Chesapeake Bay Program (2012) Dissolved oxygen. Retrieved from: http://www.chesapeakebay.net/discover/bayecosystem/dissolvedoxygen

Diaz, R.J. and Rosenberg, R. (2008) Spreading dead zones and consequences for marine ecosystems. Science, 321, 926-929

Editors of e - The Environmental Magazine (2008) Deserts in the ocean. Retrieved from: http://www.popsci.com/editors-e-environmental-magazine/article/2008-10/deserts-ocean.

Levin, L.A., Etter, R.J., Rex, M.A., Gooday, A.J., Smith, C.R., Pineda, J., Stuart, C.T., Hessler, R.R. and Pawson, D. (2001) Environmental influences on regional deep-sea species diversity. Annual review of Ecology, Evolution, and Systematics, 32, 51-93.

Rabalais, N.N., Turner, R.E. and Wiseman Jr, W.J. (2002) Gulf of Mexico hypoxia, a.k.a."The Dead Zone". Annual review of Ecology, Evolution, and Systematics, 33, 235-263.

Links:

Top picture: http://www.my-walls.net/wp-content/uploads/2012/10/fish-underwater-desert-balloon-desert-fish-lifebuoy.jpg

Map: https://nofishleft.files.wordpress.com/2010/11/coastal-dead-zones.jpg

Third picture: http://ian.umces.edu/ecocheck/forecast/chesapeake-bay/2010/methods/#_DO_-_anoxia

Dead starfish: http://www.csgc.ucsd.edu/NEWSROOM/NEWSRELEASES/2012/documents/Sonomaalgalbloom.htm