Climate change and seaweed sex: Facebook was right, it’s complicated

One of the greatest challenges of writing a science blog is that I generally have 800 words to describe something extremely complex. Take my blog on Lyme Disease. Lyme disease has many hosts, from ticks to mice to humans, even lizards. The animals are affected by tons of variables, climate being only one of them, and they’re constantly interacting with one another – coyotes are pushing out foxes, which affect the number of mice, which affect the ticks and so on. Trust me, ecology is more complex than your Facebook relationship status.

So when I decided to write about the effect climate change had on seaweed sexual reproduction, I should have known that I was entering a land of crazy. To be honest, I completely regret it.

On the surface, seaweed seems like the most boring organism on the planet, and the least sexy. It’s the itchy stuff that gets into your bikini at the beach, or between your teeth when you’re trying to impress your date at the sushi bar.

How could seaweed be complex? Well, just like your 22-year-old nephew, seaweed has a kind of wacky multi-faced life cycle where the environment could impact its success at many different stages–will he join a black metal band and tour Ohio? Explore his sexuality at Sarah Lawrence? Get that Heritage Foundation internship? Environment matters.

Take Giant Kelp, which grows in thick “forests” along the California coast. It has a funky life cycle that is tricky to explain in layman’s terms — I recommend checking out this animation.

Lady gametophytes and dude gametophytes develop from the spores that pop off of the kelp, find each other in the water, and form a new kelp strand there – because yeah, weird. It would be like if your dandruff popped off your head, turned into a penis and then shot sperm at your wife’s dandruff-turned-ovary across the room. Ok, bad analogy, because kelp have haploid spores which are totally different from dandruff –there is just nothing even remotely equivalent in our everyday lives.

So within this funky life cycle there are several moments when kelp could be either positively or negatively impacted by increases in temperature from atmospheric CO2, or ocean acidification from dissolved CO2. The truth is, surprisingly little is known. It turns out that though low pH (which would be caused by ocean acidification) negatively impacts gametophytes (the lady and male parts), increases in carbon dioxide has the opposite effect (1), while increases in temperature have questionable effects. So like, maybe bigger gametophytes, maybe not?

Ok, what about ecological interactions? Well that gets even more complex: Much like land-forests, animals love kelp forests. They’re great to hide in, munch on, and stay safe from crazy bad weather that can hit the ocean.

They’re swarming with organisms, and it gets vicious down there. The kelp have to deal with predator sea urchins (evil little critters), and are in competition with other algae. Sea urchin shells could be weakened by ocean acidification – so yay for the kelp!–and some algae also have calcium carbonate in them which again would be negatively affected by acidification–so double yay for the kelp (2)! But ocean acidification is just not all that is going on down there.

Ocean temperature will change as well, which will play back into kelp survival, and then of course the kelp sex and then my head is exploding, because what crazy person studies this anyway?!?

So it turns out that the most boring organism on the planet is also one of the most complicated, and very little is known about how it will respond to climate change. Instead of throwing up (our hands) in frustration, maybe researchers can take a tip from social media: we can stop classifying organisms in terms of plant / animal, predator / prey, endangered / not, but rather as a Facebook status: solo, attached or it’s complicated.

(1) Ocean acidification and seaweed reproduction: increased CO2 ameliorates the negative effect of lowered pH on meiospore germination in the giant kelp Macrocystis pyrifera (Laminariales, Phaeophyceae)
(2) Effects of climate change on global seaweed communities

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