Meteorologist John Lindsey on how declining sea star population could affect Central Coast
In a recent article for the SLO Tribune, meteorologist John Lindsey reported that a severe decline in the sea star population has led to a massive die-off of the kelp forests along the Northern California coastline. KCBX’s Sophie Lincoln spoke with Lindsey about the phenomenon and how it might affect the Central Coast.
Lincoln: Hi John, thanks for joining me on KCBX. So, can you tell me about how this decline in sea stars has affected the food chain and what we are seeing now with kelp forests being kind of devoured by sea urchins?
Lindsey: So, it’s not that big of an issue here on the Central Coast, but certainly off the coast of Northern California… And so, what's transpired is there's wasting diseases that's really impacted the sea star population, and in turn, without anything to keep the purple sea urchins in check and they're essentially eating all the kelp forest. So, the purple sea urchins basically will consume everything in sight. I mean not only macrocystis and nereocystis, but all sorts of red, brown and green algae. And, what's referred to, they'll actually create an urchin barren where the only thing that exists are purple sea urchins essentially, and they lose a lot of the nutritional value because there's nothing left to eat. And so, they'll actually turn to become cannibals, they'll actually eat each other, believe it or not because the absolutely total lack of food, which a lot of marine biologists didn't even realize was occurring. So what caused the wasting disease of these sea stars? A lot of people think that it's the warm water Blob. Of course, we've seen record-breaking ocean temperatures, especially along our coastline. In October of 2015, the average sea water temperatures got up to 67 degrees, which I never thought was really possible. Then, a few years later in Southern California, the Scripps near Shore Buoy got up to 81.6 degrees, which is another remarkable reading I never thought we would see. And perhaps, these warmer than normal sea water temperatures combined with lower pH, which means that the water's becoming more acid due to the absorption of excessive amounts of CO2, that may have been the contributing factor to wasting disease of the sea stars. And in turn, of course, nothing to keep the purple sea urchins in check, which allowed them to basically eat all the kelp forest off the Northern California coastline. It has been widely reported that this month, that an analysis of satellite data by researchers from the University of California, Santa Cruz, found a decline in the kelp forest by an average of 95% since 2013 along the Northern California Coastline.
Lincoln: NPR did a similar story and it mentions that warmer ocean temperatures also make sea stars more susceptible to diseases. Do you know anything about this?
Lindsey: Sure. I mean, that's what we think, Sophie. but that's a hypothesis that warmer sea temperatures and ocean acidification and another thing is maybe higher swell-energy levels. It seems like every couple of years, we break the record for lowest atmospheric pressure in the middle of these storms. And consequently, the winds are becoming stronger and the winds are what basically generates the waves as they blow across the ocean -- it's called "the fetch" -- and the stronger the winds, the higher the waves and the longer periods they have. And the longer-period waves have more energy, and that higher amount of energy may be basically ripping up these kelp beds to a greater extent. But, as far as wasting disease of the sea stars, it's probably related to warmer ocean temperatures and lower pHs due to the absorption of CO2 in the atmosphere.
Lincoln: So obviously this phenomenon is most present in Northern California, but you did mention that it is occurring to an extent in the Monterey Bay Area. Do you think it is possible that the phenomenon could happen further down the Central Coast at some point?
Lindsey: Now what's going on along our reefs though, because of the southern sea otter, is that the sea urchins that are on the periphery of a health kelp bed have a lot of nutritional value. And, it's so interesting. These sea otters have to eat about 24% of their body weight each day to stay alive. And some sea otters specialize in crabs, some sea otters specialize in abalone mollusks and other sea otters specialize in urchins. And they won't waste their time on the urchins in the barren because you know, they'll harvest those and there's no nutritional value to them. So, what they do is they concentrate on the urchins near a healthy kelp bed and in turn, that keeps that kelp bed from being devoured. And, so that's what we're finding along our coastline. The southern sea otters have really helped to keep in check the purple sea urchins. And despite having wasting disease over sea stars. I think, in my humble opinion, that I think a healthy sea otter population will really help to prevent the same 95% kelp forest reduction off the Northern California Coast and it will prevent the same thing from happening along our coast. I really believe the healthy sea otter population will go a long ways in controlling the sea urchins.
Lincoln: In your article, you cited a study by the University of Santa Cruz that found that the kelp population has declined by an average of 95% since 2013 in Northern California. What potential damaging effects might this decline in kelp forests have on other marine life or even the economy?
Lindsey: Yeah. I do know that the kelp forest provides a refuge, or an ecosystem. The kelp forest ecosystem is amazing with all the different invertebrates and snails … On a clear day, if you're lucky enough to go diving on a clear day, you're swimming through the macrocystis or the nereocystis, it's literally like swimming through a rainforest and there's so many varieties of so many different creatures that I would think as the kelp forest in Northern California was reduced by 95%, just logically think probably really reduced the diversity of different creatures along the Northern California coastline. So, it's been a real devastating loss. I wish there was some way to sugarcoat it, but it's been devastating not only for abalone, but for a lot of other different species of creatures that make their home in the kelp forest.
Lincoln: How might other stressors like warmer ocean temperatures, ocean acidification and higher-swell energy levels have also affected this?
Lindsey: Bull Kelp, which they say is their primary food source, is basically more sensitive to sea water temperatures, and that's one of the points that Scott Camarra had made. As such, bull kelp could be the first notable species of kelp in our area that could be impacted by sea water temperature warming associated with climate change. So, none of this is comforting for me considering the enormous amount of greenhouse gases we keep pumping into our atmosphere.
Lincoln: Do you know of any potential solutions that can be implemented to save the kelp forests?
Lindsey: Sure, so what they're doing up in Northern California is volunteer divers are going out and they're actually removing sea urchins and basically, the idea is to go out there and remove a bunch of sea urchins. The results of that may vary, so what they're doing is they're finding existing kelp forests and they're removing the sea urchins near existing kelp forests in hopes that they'll repopulate the rocky intertitle and the rocky reefs. That's the key. If you just go out there and you remove a bunch of sea urchins that happen not to be near a kelp forest or a kelp bed, that really won't help. But they found that removing sea urchins near existing kelp beds have made a big difference, so that's what a lot of volunteers are doing at this point. As the oceans warm, it is a great concern. So, you're right. Changes to the ecosystem, long-term monitoring of the kelp -- I think that's another thing that, one of the foremost experts along the Central Coast as far as kelp goes is Scott Camarra, and he's a long-time marine biologist. And, he told me that something that we should really do in the future is to have long term monitoring of the kelp beds is crucial so that they can make educated decisions on what to do next, such as removing sea urchins near existing kelp beds. And I couldn't agree more.
Lincoln: Thanks for joining us, John. For KCBX, I’m Sophie Lincoln.