Kelp's Hot Flash: How Heat Waves Affect Our Ocean's Gardeners

The ocean is heating up, and that's bad news for many sea creatures. Two types of kelp, Saccharina latissima and Laminaria digitata, live in the Northeast Atlantic. Scientists wanted to see how these kelps handle short bursts of high temperatures. They tested how the kelps grew, made food, and stayed healthy when exposed to a sudden 20°C heat wave, compared to their normal 10°C habitat. First, let's talk about growth. Saccharina latissima loved the heat! It grew about 56% faster when temperatures spiked. But Laminaria digitata? It didn't care one way or the other. Its growth stayed the same, no matter the temperature. Now, let's dive into how these kelps make their food. Photosynthesis is the process where plants make food from sunlight. Saccharina latissima's food production initially shot up with the heat. But after 48 hours, it dropped back down. Laminaria digitata, however, kept a steady food production rate, regardless of the heat. Next, let's look at how efficiently these kelps use sunlight. Saccharina latissima's efficiency changed depending on how long the heat lasted. Laminaria digitata, on the other hand, became more efficient the longer the heat lasted. The amount of light needed to saturate these kelps varied too. Saccharina latissima needed the same amount of light, heat or not. But Laminaria digitata needed different amounts of light depending on the heat duration. Interestingly, neither kelp changed its defense mechanisms, even after 72 hours of heat. They kept the same levels of protective chemicals, called phenolics, regardless of the temperature. So, what does this all mean? Both kelp species can handle short-term heat stress. But they handle it in different ways. This is important because our oceans are warming up. These findings suggest that these kelp species might be able to tough it out during extreme heat events, like marine heat waves. But remember, this is just a snapshot. Long-term effects could be very different.