Listen: Jim Klaren, San Francisco Bay, Asker Justin discussed on Bay Curious
"Now reporter Amanda Font heads out in search of answers about the colors of the bay. I live in Alameda but I work in San Francisco so I get to take the ferry. Every day it's beautiful it's a great commute and also means I get a good look at the water her have to say from short ashore. It looks pretty green to me incremental. Change is hard to see when you're looking at something every day day like how your hair looks just as long today as it did yesterday even though it has grown a little you could look at an old photo of yourself to see a difference but that won't work if we're looking for subtle color changes in the bay. The only way to know for sure is through data and lots of it many parts of the very different today than they were forty three years ago. Luckily someone has been collecting. That data name. Is Jim Klaren. I'm trained as a lake biologists. But I've spent my entire career working in San Francisco Bay. Jim recently retired from the US Geological Survey but he spent more than four decades studying. How the bay is influenced by human activities? And he's seen a lot of change. I asked Jim if he could answer Justin's question just straight up is he's the bay really greener okay The color of water is pretty complicated. Subject alright all right kids buckle up for some science when I think about the color of water in California the first thing I think about US Lake Tahoe. You've probably seen those bumper for stickers that say keep Tahoe blue well what does that mean. Lake Tahoe is pretty much. Snow Melt is pretty close to pure water at doesn't have much in in it and if you held up a drop and looked at it it would pretty much be clear. It's light that influences. How we see the color of water? So water absorbs herbs red and green and orange and yellow and violet but it doesn't absorb blue. Blue Light has a much shorter wavelength so unlike the colors of light with longer wavelengths same red or orange. It doesn't snake through the water they were. They hit the molecules. The blue nightly scatter on your eye perceives more blue light and so when sunlight penetrates into lake AAC likely Tahoe. All of these other colors are absorbed by the water but was slip behind his the blue. This light scattering is also the reason. The Sky looks blue. Oh so if when you were a kid your mom or dad told you. The Sky is blue because it reflects the ocean and the ocean is blue because it reflects the sky. Yeah they probably just didn't know the answer or you were asking too many questions so in the bay when you see any other color besides blue you really seeing particles particles. Ed had other colors. There are living particles in our nonliving particles to nonliving particles are mostly play particles. Also come from soils this sediment gets into the water through erosion runoff after it rains and via the multiple rivers that flow into the bay currence. Turin up the sediment which can make the water look Brown. The living particles are microscopic algae phytoplankton the phytoplankton have the same chlorophyll that land plants. Have that make them green. It's these phytoplankton that give the water a greenish hue now. The question of has there been a long term trend of greenness in the bay. It's it sounds like a simple question but it's not as simple simple and straightforward as you would think because we have all these sources of variability. That isn't a static thing it changes seasonally day to day. A our to our and so if there's a long term trend all of that variability makes it hard to detect a a long term pattern of change. Here's where all the data Ada comes in at the USGS. Jim was also part of a project that since one thousand nine hundred sixty eight has been collecting water samples in the bay to measure changes changes over time. These sampling cruises happen about once a month. I talked with Erica. Nishad on one of them. She's a biologist who works for the. US She s this day. She was using specialized instruments to collect the measurements of several different factors including chlorophyll content so so the C. T.. He is taking vertical profiles of the water column at different stations. Every station we stopped at is getting a complete vertical profiler of how space and time the TD that stands for conductivity temperature and depth is a bundle of different sensors attached together at the end. A cable at each of the sampling locations. Erica lowers this thing. Slowly to the bottom of the bag. He added this nice camera so I can see when the CD's surface. So I WANNA start right sitting at surface and then I go to as Costa bottom as I can get without reading it into the bottom so I can see back here all the way down. It's scanning taking measurements and reporting them. Back it comes back up with a sample of deep water water so they can study the phytoplankton species later. There's also a continuous surface. Water sampler running inside the lab on the boat and and a special instrument that is taking pictures of individual fighter plankton in real time. They're collecting a ton of information. So that when you look at the larger data data set patterns start to emerge. Here's Jim again. We have measured over the last two decades a trend of increasing phytoplankton. So two things. You're going on. That would make the bay look greener over time decreased sediment input less brown increasing Fayek Langton abundance more green so yes. There is a trend of increasing greenness in the bay. There you have it. It is greener. But we're not done yet because elect Ricardo Montalban in the wrath of Khan. I want to know why why. Why are there more phytoplankton now than before now we need to talk about biological communities? Phytoplankton are small but they take up a lot of space little on the aggregate but like massive on the whole if you weigh all of the communities that live in the bay the phytoplankton the bacteria the clams the muscles that crabs the fish the phytoplankton would way most it's the living component that has the largest living biomass in the bay. There right at the base of the Food Web. A lot of them are eaten by clams mussels which are filter. feeders they pull in and blue water through a tube like structure called a siphon and in the process they filter out the nutritious phytoplankton. They used to do this at a pretty astounding rate and we calculated all. This is over the three decades ago. That if you if you know how many clams mussels are in the bay. How large they are? You can calculate how fast they're filtering water her. The clams and Mussels that live in the bay are pumping volume of water this equal to the volume of water in the bay every one or two days during the summertime. If you've ever gone swimming in the Bay and gotten watering your mouth just know that it has probably been filtered through a clam so back before nineteen ninety eight. Those clams and Mussels. Were keeping the fighter plankton population under control but then things started to shift and in nineteen ninety nine. We started seeing changes in the seasonal pattern of the phytoplankton. We saw bloom in the autumn. We'd never seen anything like that before. Our Question Asker Justin was living in New York in one thousand nine hundred nine so he didn't see this shift until it was well underway the extra phytoplankton blooms. Were a mystery to Jim in the team team until they checked in with their colleagues who studied the clams they could hardly find any in the bay but other species numbers were growing. They started seeing record high numbers of crabs in the bay flatfish in the bay looking those soul and record high numbers of shrimp. Those animals are all coastal hosted marine organisms. Who Live their adult lives in the ocean? But they're young spent the first year or two of life in the shelter of the bay and they all eat eat clams so Amanda to make sure I have this starting in nineteen ninety nine. We have more clam eaters so a fewer clams thus more fido plankton and greener water. Yeah this is called a trophic cascade. A change in one part of the food web sets off a cascading effect on the other organisms in it and the clam eater numbers are still up. Which is why the water is still that rich shade of artichoke joke? Okay but why the Senate influx of those other animals. We have learned over the last couple of decades that there are natural cycles of the climate it system that fluctuate over periods of multiple decades. There are these huge wind oscillations. That happened way out in the North Pacific Ocean around around nineteen ninety nine the direction of the winds shifted in a way that caused the ocean along our coast to churn up cold water from the deep this is called coastal upwelling in the cold. Deep water is rich nutritious so this phase of strong winds strong upwelling is a period of high biological productivity activity. Okay so the winds blow it shifts. The ocean climate feeds the flat fish crabs and shrimp. Their babies drift into the bay. Eat the clams. The fighter plankton populations grow and the water turns green. That's how it works and this all has something to do with human caused climate change. I take they get actually know. Jim made it clear that this is not something that has been caused by human actions. These are responses to global climate change. This is part of the natural oscillation of the climate system. Does that mean the water will eventually go back to looking more blue so this Greening period that we've experienced since nineteen ninety ninety eight. We might reverse that pattern if we see this next climate shift. The only way. We'll really know for sure is if we keep collecting data so we can observe long-term changes. It's really important for us to keep making measurements. Keep making observations. Because the longer we do this the more were surprised. Yeah surprises are new discovers that was reporter Amanda Fund. She took the story back to Listener Justin Heart tongue to see what he thought. I'm glad to know that It's not the climate. I'm glad to know it's not my failing eyesight or my bad memory. So mystery definitely solved and I can also tell my dad not that I am not crazy what she was when I told him about this. So thanks for asking the question. Justin digging the podcast. It will definitely dig our email. Newsletter we send it on the first Wednesday of the month and has answers to more listener questions than we have time on the show. Plus behind the scenes like how we used a ferryman to make sound effects for this episode in San Francisco Ooh.."