by Julia, Olivia, and Thomas
Bishop O’Dowd High School
Emerita analoga, or the common Pacific sand crab, is an small animal with a colossal impact on beach ecosystems. We will examine the population trend in sand crabs over time at ocean beach, and examine
possible environmental factors that could have caused this, specifically El Nino. The sand crab is an indicator species, so examining the health of their population will allow us to examine the health of the sandy beach ecosystem as a whole.
Sand crabs are herbivores and an important food source for other beach organisms, specifically shorebirds. We assumed that if the sand crab population is thriving on a beach, then the shorebird population should be doing well too. We looked at data of sand crabs and shorebirds along the north-central California coast over the course of a year. Our original hypothesis was that if the population of sand crabs was high, then naturally the population of shorebirds would also be high. But, contrary to our hypothesis, a flourishing sand crab population means there are less shorebirds… More
by Emily Gottlieb, LiMPETS Coordinator for Central California
How does a sea anemone eat? What time of year are the most pacific mole crabs found on the beach? How do you tell the difference between flattened and slender rockweed? These are not questions from last night’s Jeopardy episode or this year’s AP biology test. These are questions that real students ask while they collect real data in the field as part of LiMPETS (Long-term Monitoring Program and Experiential Training for Students). For over ten years, LiMPETS has encouraged scientific inquiry through hands-on science experience, a theme that now beats throughout the NGSS (Next Generation Science Standards).
The Pacific Grove Museum of Natural History has coordinated LiMPETS for the California Central Coast (Davenport to San Simeon) since 2011 as part of the larger LiMPETS network. The network engages approximately 5,500 students and teachers annually monitoring sites from the Sonoma Coast to Los Angeles.
Author: Jeff Sandler, teacher, The Berkeley School
In May 2014, the 7th grade life science class from The Berkeley School spent an entire week out in the field focusing
on some of our local communities. In addition to participating in both LiMPETS monitoring projects (sand crabs at Muir Beach and the rocky intertidal zone at Duxbury Reef in Bolinas), students and teachers spent a night camping and learning about the redwoods at Samuel P. Taylor park.
We collected data about sand crabs from Ocean Beach. From the data, we came up with a question about the sand crabs, and supported it with the data we collected. We compared our findings to that of other scientific resources, like the “Pacific Mole Crab” article. We were able to see if sand crabs changed from the time the articles were made to now. When we looked at the findings, we could come up with possible causes. We gathered the information and began to put it into a blog. This process helped us become more confident in science and in writing. It’s amazing that our research is contributing to the scientific world.
Have you ever seen a sand crab at the beach? If not, imagine little creatures with grey shells that wiggle backwards and live underneath the sand. You may ask yourself, why should we care about some tiny sand crabs? Well the answer is simple, they are actually very important to a beach’s ecosystem, as they are the basis of the food web. By monitoring sand crabs, we can indicate the health of the entire beach.
There are many reasons why it is important for beaches to be clean. Beaches that are covered in litter are not ideal places for life to thrive. Our group found this from the two sites that we visited. The first was the San Leandro Marina. This beach was covered in litter, and clearly was not well-maintained. There was not even a beach, only broken concrete filling the 10-foot gap from the walking path to the water. The only life we found here were seagulls and algae. Seagulls don’t even live on the beach, so they aren’t really affected by this, and algae will grow regardless of the lack of effort in supporting the site. However, compare this to Ocean Beach. This site is well taken care of, and the multitudes of species that live there illustrate this fact. These include the Western Snowy Plover, and the topic of this blog, the Sand Crab.
When our group went out and had an awesome time researching the sand crabs at Ocean Beach, we started to wonder if there were more females in the population of more male. Our question is concerning the sex ratio between males and females. Sex ratio is defined as “The proportion of males to females in a given population, usually expressed as the number of males per 100 females.” Are females dominating males in the sand crab population?