LiMPETS Sandy Beach Monitoring Classroom Presentation - SCRIPT

Transcription

1 LiMPETS Sandy Beach Monitoring Classroom Presentation - SCRIPT I m really excited to talk to you about the LiMPETS program for which you guys will participate as marine scientists. LiMPETS stands for Long-Term Monitoring Program and Experiential Training for Students. What does that mean? It means that you are going to participate in an ongoing scientific study tracking the environment that teaches scientific data collection to you! This monitoring project was created as by of the National Marine Sanctuaries in California. What is a National Marine sanctuary? Think about it as a National Park in the ocean. It is a protected area to limit human disturbance like oil drilling and pollution - to preserve the natural resources and protect the marine organisms like whales, fish, turtles, seabirds and little animals like squid and crabs. There are 13 sanctuaries and 1 US Monument in the US waters, and we have 4 in California! California is a very biologically rich area with many organisms to protect, like whales and sharks. We also have an amazing coastline which is where you come in.

2 We are going to collect data on the most important animal on the beach. Does anyone have a guess on what that animal is? The Pacific Mole Crab is an important widespread herbivore on the beach and serves as the food source for much of the sandy beach food web. Changes in sand crab populations could affect the populations of their predators like shorebirds and surfperch. Let s talk about sand crab anatomy. Sand crabs live where? -That s right, the sand! They burrow into the sand, but still need to see so they have stalked eyes. Their eyes can stick up out of the sand. -They have two sets of antennae. The shorter primary antennae are for breathing and the longer secondary antennae are used for feeding. -Sand crabs have a segmented exoskeleton that keeps them safe. The main shell is called the carapace; this is going to be important later. -They also have a tail like shell segment called the telson. It protects their bellies and in the female her eggs as well as helps the animal swim and anchor itself into the sand.

3 Reproduction occurs from February to November. Females carry the eggs for one month. The batch of eggs is called a clutch and they can have up to 50,000 eggs in one clutch. Once the eggs hatch, the larval forms are planktonic and they drift in the ocean for about 4 to 5 months. This is called the Planktonic Larval stage as the young crabs go through a number of developmental stages. Then, the larvae drift into the waters at the beach. When the crabs are carried by current back to the beach, we call this recruitment. Once they settle on the beach, we call them recruits. These recruits then live in the sand and grow by molting their exoskeletons and become adult sand crabs. Adult sand crabs can live up to 2 to 3 years.

4 Once they settle on the beach, sand crabs eat tiny algae/phytoplankton like diatoms and dinoflagellates as well as detritus which are sinking organic particles. They catch these tiny organisms and particles with their secondary antennae. This is called filter feeding. Let s watch them do it! [Show Video] What eats sand crabs? That s right, fish and birds. The crab s main predators are surfperch and shorebirds. The barred surf perch is a very common fish in the surf zone and sand crabs make up 90% of its diet! Sea Otters are one of the few mammalian predators that eat sand crabs too. Where do sand crabs live on the beach? Sand crabs live in the swash zone which is the area from the highest reach of the waves to the lowest reach of the waves. The swash zone moves up and down the beach with the tides which means that the crabs have to move up and down the beach to remain in the swash zone. Why do they live in the swash zone? That s right because it is the perfect place to get food without getting eaten by birds or fish. The swash zone may change in width depending on the slope of the beach. Now that you know all about sand crabs and their importance on the beach, let s talk about how we are going to find these little guys and what information we are going to collect.

5 One thing that is really cool about LiMPETS is we use the same protocol from Santa Barbara to San Francisco. Scientists use the technique called subsampling. Subsampling = taking smaller samples as a subset of a larger potential sampling area. Researchers use this technique in order to get an idea of many organisms exist without having to sample the entire area. The first thing we are going to do is set up the survey area. We use a 50-meter survey rope to this. This rope designates our sampling area. The rope is marked every meter, so there are 50 marks on the rope. The first thing you will do in your sampling team is to pick your random #. Close your eyes and point to a number on our random number sheet, that number is where you are going to set up your transect line. A transect is the line from which scientist collect their samples. We are going to split into teams to monitor multiple transect lines. What is a transect line? To survey sand crabs evenly across the swash zone, scientists use a 10-meter transect line that starts at the top of the swash zone.we are going to take samples every meter. Since the rope doesn t stick in the sand, we are going to

6 use flags to mark each meter. Once you plant the flags, roll up the rope and put it high on the beach. Alright, now that your transect line is set up, let s core that is the way scientists collect the subsample of sand crabs. When the water washes away, stick your core into the sand to the bottom of the tape. To hold all the sand in the core, tilt it and stick your hand underneath. Don t disturb the crabs! Your teammate will have two different sized sieves: one for big crabs and one for small crabs. A sieve is a fast way to get the sand crabs separated from the sand. Dump the sand into the sieves. make sure you have them stacked on top of each other, the big holes are on top. Now a third person needs to scoop up water from the ocean and pour it in the sieves. This washes the sand away and leaves you with sand crabs! So you found a sand crab, now what? So you found a sand crab, now what? The first thing you do with the crab is measure it. Scientists are interested in the size of the

7 crabs. So we are going to measure their carapace remember the main shell-segment on the crab. To do this, we use a caliper, which is a great tool to measure round things and things that can squirm around in your hand like sand crabs. Put one point of the caliper between the eyes of the crab that is where their carapace starts - and at the end of the carapace. Make sure you read the number at zero. So you measure a sand crab and it is 7mm that is a recruit. Remember recruits are the new crabs on the beach. Any crab 9mm or less is a recruit. There are different-sized recruits and its important to measure every crab you find! Now, if you get a sand crab that is 10mm or more that is an adult and now we are going to determine its sex. To do this, we lift the tail section do you remember what that is called? Right, the telson! Lift the telson and you can see if the crab is a male or female. So what do you think this one is? That s right, it s a female! You can tell because she has a whole bunch of eggs. What is her bunch of eggs called again? That s right, it is a clutch. But what if a female doesn t have eggs at the moment? Well, a female has special body parts that hold her eggs. These are called pleopods and they look like little strings that start at her back legs and meet up at the center of her body. Males don t have pleopods. What about this crab? Male or female?

8 That s right, female. See the pleopods. How about this one? That s right, it doesn t have pleopods so it is a male. Now let s talk about recording your data! It is important for you to write down what you find! Write the beach name, your school, the recorder s name, and date. When you pick that random number at the beginning of the setup, write it in the random number section. Each sample represents a core. Make sure you mark if the core is taken in the swash zone or in dry sand. So, you take your first core, you use the sieve and water to get rid of the sand, and you find drum roll please you find no crab. Anti-climactic but completely valuable data. We are just as interested in where sand crabs are not as in where they are. Check the zero box and move onto the next core. (Sand crabs are not uniformly distributed across the beach) The next core you find sand crabs! You pick up your first crab. What is the first thing you do?

9 That s right, measure it. It is 27mm. Note: we don t use.5 or.8; whole numbers only. Now what? That s right, determine its sex. It is a female with eggs. Sometimes you can get a lot of crabs so we use tallies to save space. 1 tally for a 27 female with eggs. You measure and determine sex for the rest. Awesome job, now you can move onto the next core. Before you do that, make sure you put the sand crabs back either in their original hole or in the ocean away from your transect line. When you get back to a computer, enter your data. Remember, your datapoints go into a state-wide 13-year database. You are contributing to an important scientific study. On the LiMPETS site you can also see the data you collected as well as the long term data. The National Marine Sanctuary uses your data to measure the health of the coast. One very important thing that LiMPETS does is establish a baseline at beaches in case any human disaster occurs like an oil or sewage spill. The state of California uses your data to judge the success of Marine Protected Areas. You can do a lot of things with your data once you enter it. At LiMPETS we have many different options if you want to stay involved like making a poster to present at a science conference,

10 blogging about your sand crab findings, spreading your knowledge or cool photos through social media, or making a video that explains the importance of sandy beaches in California. the datasheet. Now lets talk about what to expect while you are out in the field. What are the two things that are ALWAYS on a beach? That s right, water and sandy. So you will get wet and sandy. I like to wear shorts or roll up my pants and go barefoot on the beach. But sometimes it is cold, so make sure you bring layers. I have two very important rules: #1 Don t turn your back towards the ocean. #2 Don t go in water above your knees. Measuring Activity