Sparkle of the Sea

Phytoplankton bloom in Arabian Sea.
Image credit: NASA Aqua satellite

This just in from NASA’s Aqua satellite: a giant phytoplankton bloom in the Arabian Sea off the coast of Pakistan.

The green swirls are, of course, the phytoplankton, which are individually microscopic but combine in huge numbers to form algae blooms like this one. Blooms are common during monsoon season, when strong winds blow across the ocean towards land causing the upwelling of cold seabed water that’s chalk full of nutrients. The phytoplankton go to town, reproducing like crazy.

There’s some speculation now that algae blooms are happening more frequently here and in other places because of climate change. Warmer weather drives more monsoons, while warmer sea water adds to the happy situation for phytoplankton. They are at least somewhat responsible for creating the oxygen-deprived conditions that kill fish and other marine life.

Another interesting change is the type of phytoplankton that’s making an appearance. It used to be that Noctiluca miliaris (otherwise known as Noctiluca scintillans) would only turn up once and a while, but now it’s making more frequent showings, according to a 2008 study published in Deep Sea Research I, Blooms of Noctiluca miliaris in the Arabian Sea.

Miliaris, otherwise known as “seasparkle,” is hard to bad mouth. It’s one of the non-toxic kinds of dinoflagellates, the bad ones of which cause red tide and nasty diseases like paralytic shellfish poisoning and ciguatara. Miliaris has a beautiful glow-in-the-dark bio-luminescence, which you can catch glimpses of when you stare out at the ocean at night.

More sparkle to the Arabia Sea sounds pretty cool. Still, is it another sign of a warming world?

Toxic Waters

Remember the old idea that we could escape climate change by dumping a bunch of iron into the ocean? Iron “seeding” or “fertilization” rests on the notion that iron could be added to the nutrient-deprived deep sea to cause massive phytoplankton blooms, which would capture carbon and, as they died, sink it to the ocean floor.

Red algal bloom off the coast of New Zealand. Image Credit: Miriam Godfrey

Sounds good, except many people have gotten cold feet over human-induced iron seeding – after all, it seems like too much tampering with ocean ecosystems. And one recent study lowered estimates of how much carbon could realistically be stored using this method.

Adding new caution to the heap is a study published yesterday in the Proceedings of the National Academy of Sciences, which found that iron seeding could promote the growth of a toxic type of phytoplankton called Pseudonitzschia. The name sounds like a serious psychological disorder. And it can mess you up. Pseudonitzschia produces neurotoxic domoic acid, like what’s seen during red tides, and can bioaccumulate in shellfish, anchovies, and sardines causing lethal results in mammals, including humans. Not the kind of stuff you want floating around the ocean.

It was previously thought that the toxic form of Psuedonitzschia is limited to coastal waters, but this study found “unequivocally” that the mid-ocean variety did, indeed, produce the toxin. The study’s authors, led by Charles Trick of the University of Western Ontario wrote:

“Although the total toxin concentrations generated in some of these preliminary experiments may not be enough to generate acute toxicity at higher trophic levels, it is unclear whether higher concentrations may result under conditions of large-scale and persistent iron enrichments designed to obtain carbon credits.”

In other words, dumping iron into the sea on the scale of a carbon credit program could potentially make ocean waters highly toxic. It appears that the toxin itself allows Pseudonitzschia to outcompete other species of phytoplankton, ensuring its perpetuation. Pretty nasty stuff.