The Attack of Vibrio and the Plummeting Deaths of Sea Stars

— Written by Vivian Lee

A keystone species, one that is largely depended upon by other species, acts as a fundamental instrument for balancing an ecosystem at a constant equilibrium. Thus, when a keystone species population declines or has an absence in an ecosystem, the consequences are detrimental. Recently, the Rocky Intertidal Community of the West Coast has been facing consequences such as overpopulation since the sea star wasting epidemic. In 2013, a mysterious disease spread from Washington State to as far North as Alaska and as far South as  Mexico, sweeping across the coast and taking away many sea stars species in its path.

As white lesions form on the body, the disease takes away each arm at a time, and clinging onto what becomes the last of themselves, the sea stars waste away until only a sheer outline of ossicles remain ghostly on the rocks of the intertidal. The wasting disease leaves sea stars hopeless as the progression to death can take less than a few days, leaving them unable to salvage themselves; causing populations to plummet to the verge of local extinction. Amongst the many species, Pisaster ochraceus was among those attacked the hardest by the disease,producing questions and possible hypothesis not only for the Pisaster ochraceus but the rest of the sea stars. Being one of the biggest marine epizootic outbreaks that occurred, questions are still on the rise, parameters have been continuously observed as the cause of the disease are countless.


Figure 1: Photos above display three different species of sea stars. 1a displays  two Pisaster ochraceus sea stars (orange and brown) and Pisaster brevispinus (pink). 1b is a closer view of the brown Pisaster ochraceus. 1c. Sea star species known as Pisaster giganteus

Is it the rise of seawater temperature along the west coast? Could the El Nino event have played a part in intensifying the pathology in infected stars from certain sites compared to others? Perhaps the salinity of the water? Has something changed in these Echinoderms’ diets? Finding a concluding answer has been as difficult as finding a needle in a hay stack; however, an explanation of the disease has been monitored. Vibrio, a bacteria found in sea water and some marine organisms such as crab and eel can affect both humans and other marine organisms. Vibrio was found on many sea stars that were collected for observation. This bacterium may have opened the doors that weaken the sea star, causing the white lesions to form and eventually leading to death. Site by site along the Southern California Coast, multiple bacterial swab samples of sea stars were collected during the time span during and after the outbreak. Whether the stars showed phenotypic/ physical attributes of sickness or not, samples were taken to observe the presence of the bacteria.

Previously, a collaborative team from Dr.Hofmann’s lab at UC Santa Barbara collected swab samples of Pisaster ochraceus from sites in Southern California ranging from Lompoc to San Diego, including the Channel Islands. This summer, a continuation of detecting the presence of the bacteria will be studied. Through this, we anticipate grasping a better understanding of the biodiversity of the bacterial community associated with sea stars from  samples collected during and after the outbreak. We hope to find current sea stars in sites locally around Santa Barbara as well to understand and monitor the differences compared to when the outbreak occurred.

Ara’s Fishy Adventures

— Written by Ara Yazaryan


Counting dorsal rays of a rockfish

As a research assistant in the Caselle laboratory, my entire experience revolves around fish. My day starts at 9 o’clock, when I report to the lab and march over to the microscope for duty. One of the ongoing projects in the Caselle lab which I have the good fortune to partake in is the SMURF monitoring program at Santa Cruz island. The SMURF discussed here, contrary to the little blue people that may come to mind, is a large black “cushion” of intertwined black fencing material. SMURF stands for Standard Monitoring Unity for the Recruitment of Fishes. This large object is meant to mimic kelp structure, and gives planktonic fish larvae a place to settle and grow. Every two weeks, these SMURFs are netted and the fish are collected and frozen for later study. And this is where my abilities with a microscope come in! One of my primary laboratory responsibilities is to count and sort the SMURF fishes into each respective species. Though some species, such as Cabezon (Scorpaenichthys marmoratus) are instantly recognizable, other families of fish, such as juvenile rockfish (Sebastes) and the Clinids require a closer look. In order to separate them into the respective species, all rockfish must be observed under a dissecting microscope in order to count their fin rays. Each species of rockfish has a unique combination of dorsal and anal fin rays, serving to identify these individuals when they are young and have not yet developed their respective mature morphological features. I examine these fish one-by-one and sort them, and then place them into a final freezer storage.


Otoliths – note the concentric ring structure

When my eyes need a break from the microscope, I move on to fish dissections. Another of my laboratory responsibilities is extracting the otoliths from fish heads. After opening the brain case, these “ear-stones” are extracted and saved for storage. Eventually, the otoliths will be polished and observed under a microscope. As a fish mature, information about what it eats, rates of growth, and potential environmental stressors is stored inside their otoliths. All this important information can be gleaned by extracting and observing the otoliths.


Large Male Sheephead (Semicossyphus pulcher) collected at Anacapa Island

The third project that I have just begun to work with is the monitoring of California Sheephead (Semicossyphus pulcher) stomach contents between sites at Anacapa Island. Fish were captured by spear or hook-and-line (much to my inner angler’s delight) and their stomach contents will be examined to determine how MPAs affect their feeding habits and population levels. The overarching goal of these three projects, and the information I aspire most to learn about, is how California fish communities are responding to Global Change. Fishing, climate-change, Ocean warming and acidification, and pollution all have the potential to degrade our rich fish stocks. By studying and monitoring these fish, I hope to gain a better understanding of California’s complex marine ecosystems. In particular, I want to more thoroughly understand how MPAs conserve fish populations, and correspondingly alter dietary structures. I will use the Sheephead (As Dr. Caselle has made very clear, there is no “s” in the middle) as a model organism for this experimentation. I seek to answer the question: Does dietary composition of Sheephead change inside and outside of Marine Protected Areas? Using observation of stomach contents coupled with statistical quantification, I set out to answer this question over the course of my REU program. Though only two weeks have gone by, I feel as if I have gained a year’s worth of scientific immersion. Between lab work, field research, and peer camaraderie, I have gained a much clearer understanding of what research in the marine science field consists of. I look forward to what is to come, and am excited to examine many more fish in the upcoming weeks at UCSB.

What does a changing climate mean for Phytoplankton and what does this mean for our planet?

— Written by Ean Eberhard

The microscopic marine algae known as Phytoplankton are incredibly important to our planet. Although minuet in size these organisms have an immense amount of responsibility within both aquatic and terrestrial ecosystems.

Phytoplankton are primary producers, the foundation of the marine food web, feeding everything from zooplankton to massive whales. As a primary producer these phytoplankton create the foundation of the aquatic food web and thus bare the weight of the rest of the aquatic food web. In other words, the fluctuation in phytoplankton abundance could mean a collapse in the web.  Phytoplankton are not only a source of food but are also a large contributor to the biological carbon pump, responsible for most of the carbon dioxide transfer from the atmosphere to the ocean. For this reason, changes in the growth of phytoplankton could have a great effect on atmospheric concentrations of carbon dioxide. Phytoplankton can also be detrimental. When nutrients levels are high, phytoplankton can grow out of control, creating algal blooms which produce extremely toxic compounds with many harmful effects.   There is no doubt that the balance in phytoplankton abundance is crucial to all life. Unfortunately, phytoplankton are experiencing more stress due to a changing climate.

For the next seven weeks I will be studying the photochemistry of phytoplankton in response to three different stressors. This experiment will be a multifactorial design that will give a more realistic look into how the stress of a changing climate is much more complex than rising temperatures. These three stressors include variances in light intensity, temperature, and CO2 levels. Each of these stressors correspond to variances in the phytoplankton’s environment due to the change in climate. I will dive deeper into the response of these phytoplankton by measuring cell abundance, cell efficiency, Dissolved Inorganic Carbon and pH. This experiment will give us an insight into just how exactly phytoplankton may respond to a changing world and the findings may provide an insight into how the effects on phytoplankton could have a ripple effect on all other life.

Will one of Japan’s most famous delicacies survive a changing climate?

— Written by Will Dejesus


Purple urchin feeding on giant kelp

Sea urchin is a famous Japanese delicacy used in sushi, called uni. The gonads, or sex organs, is the part of the urchin that is actually eaten. It is high in protein and contains omega-3 fatty acids, which can help lower blood pressure. Sea Urchins can be found along the West coast from Baja to Seattle. Sea Urchin harvesting along the coast of California has become one of the highest valued fisheries in the area. Almost 75% of the urchins caught along the California coast are sent to Japan, where they import over 250 million dollars worth every year.

Not only are sea urchins a relevant part of the food and fishing industry, but they also play a critical role in the kelp forest communities, as their preferred food source is giant kelp. With few native predators, sea urchins have the power to decimate kelp forests, which are already struggling with changes in ocean chemistry. Areas where sea urchin population has sky rocketed, kelp density has been nearly wiped out in a short period of time. From ocean to table, sea urchins play an important role in coastal communities on land and below the surface.

I am interested in taking a closer look at the feeding habits of these invertebrates given future predicted changes in ocean temperature. Their reactions to temperature changes in general and especially in feeding behavior is all of interest in this study. This will begin to paint a clearer picture of what we can expect our marine ecosystems and seafood industry to look like in the future.

Shark abundance shown with dermal denticles

— Written by Maria Rivera

How can we know how many sharks there are in a specific area? We cannot track or observe them as easily as other animals, especially land animals. This is a major issue because we do not have sufficient data that tells us about shark communities in the past nor present. Without this knowledge, we cannot analyze how humans have impacted shark communities near reefs. Fortunately, there are new techniques being developed that help us measure the relative abundance of sharks near coral reefs. One of these new techniques involves analyzing dermal denticles. Dermal denticles are the microscopic tooth-like scales that cover sharks’ bodies. Sharks shed these denticles, and they are deposited and preserved in coral reef sediments. Hundreds of denticles can be preserved in the sand, recording a timeline of what shark communities where like in the past and how they have changed.


Fig. 1 shows different types of denticles that belong to different kinds of sharks. Denticle A has high ridges for swimming, while denticle B is smooth and thick for protection. Photographs courtesy of Natalie Minouei taken on July 6, 2018.

How do denticles help us estimate/determine the relative abundance of sharks? By comparing the denticles we find in sediments from different regions and time periods, we can qualitatively estimate the abundance of sharks. Not only do the number of denticles help us interpret the abundance of sharks near reefs, but we can also use the wide array of denticle shapes and sizes to learn more about the ecology of sharks. Variation in denticle morphology serves different purposes. For example, thin denticles with high ridges are for drag reduction and allow the shark to swim faster (Fig. 1). These denticle characteristics are common with pelagic sharks that spend a majority of the time in open waters and are fast swimmers, like great whites for example. In contrast, there are denticles that can be smooth and thick for abrasion strength, this provides protection to the shark from the ocean floor (Fig. 1). Denticles like these would be found on sharks that live near reefs, such as nurse sharks. Variations of denticles for different sharks gives us an insight into the structure and composition of the shark communities roaming that reef.

We can also look at denticle distributions in areas across gradients of human impacts to investigate how shark communities are affected by human activities. For example, if there is a lot of fishing in an area, there might be lower numbers of sharks and thus lower number of denticles. If we compare that to a place that is less impacted by humans, we would expect to see more sharks and more denticles. This can help us understand how humans have impacted the marine ecosystem through time and in a context of local baselines. This is a great way to analyze the relative abundance of sharks near coral reefs when there are limited tools and scientists cannot go physically count sharks one by one in the ocean.

Studying Santa Barbara Fisheries: Spotlight on Rock Crabs

— Written by Gabbie Baillargeon


Walking along Stern’s Wharf, accompanied by the bustling crowd of downtown Santa Barbara tourists and locals alike, signs proudly boasting the sale of delicious rock crabs seem to line the boardwalk.  Similar to their more famous and tasty cousin, the Dungeness crab, rock crabs are a group of crab that comprise a productive and lucrative fishery along the coast of Southern California and the Northwestern Pacific states.  Three distinct species of rock crab are found off the shores of California: Yellow (Cancer anthonyi), Red (Cancer producutus), and Brown (Cancer antennarius) rock crabs.  All three species are available to purchase as seafood, though red rock crabs have the highest demand due to their larger size and sweeter meat.  For the amount of recreational and commercial fishing that surrounds Rock Crabs, shockingly little research has been dedicated to studying them and even less information is available to shed light on how these crabs operate in the unique environmental conditions of Santa Barbara.


Two yellow rock cabs inside a cinderblock, a favorite resting spot.

My research project investigates how changing fishing pressures on rock crab populations alters their foraging behavior.  In order to mimic fishery pressure, different densities of rock crabs will be put in controlled environments and fed different densities of California mussels (Mytilus californianus) to measure their predation rates in each case. The goal of this project is to determine if changing the number of rock crab competitors of a single species will affect how they forage.  In an effort to better understand how fishing plays a role in shaping the nearshore marine environment, the potential consequences of varied foraging behavior in response to population shifts on the larger ecosystem will be analyzed.


A Brown rock crab being measured and tagged after collection from Stern’s Wharf.

In the early stages of the project, plenty of challenges quickly multiplied when working with the rock crabs or “little monsters” as we fondly like to think of them.  The rock crabs have earned this nickname as they seem to have a bit of a angst-ridden destructive streak in them, especially when it comes to following some basic tank rules.  After only 24 hours, the crabs had deftly removed their identifying leg bands – I’m sure they planned this operation carefully and helped each other out.  Then, instead of being happy with their buffet of mussels and clean tank to play in, some crabs decided that they simply must explore what was on the other side of the tank barrier and crawl into their neighbor’s tank.  The mussels are bluer on the other side, right? Lastly, although the names red, yellow, and brown rock crab seem to indicate that it would be simple to distinguish between the three species, I painfully came to find out that could not be farther from the truth.  Despite the roadblocks, learning to care for the crabs and become excited over little things such as a crab finally deciding to eat mussels, has all been a part of the learning curve and given me invaluable skills of patience, problem-solving, and a lightning-fast reaction to a feisty crab claw.

Calling for a change in our definition of sandy beaches

— Written by Emma Saas


Kelp washed up on shore, providing resources for many sandy beach invertebrates

The California coast is world famous for its miles of sandy beaches, sunbathing, beach volleyball, and morning jogs along the water line. Each year, millions of tourists come to enjoy what this state’s shorelines have to offer- and why wouldn’t they? Watching sunsets in bathing suits after a long day of surfing sounds like a pretty postcard worthy vacation. What many tourists -and locals!- don’t always think about,is the fact that beaches are also rich coastal ecosystems. Food webs on beaches depend on subsidies from other marine ecosystems, like kelp forests. On many tourist beaches, beach grooming removes washed up kelp and other organic material from the beaches using large machines. Kelp is food and shelter for many important invertebrates including talitrid amphipods, commonly known as beach hoppers that look like little jumping shrimp.


Megalorchestia corniculata, a talitrid amphipod, begins burrowing into the sand

Several species of beach hoppers are commonly found on southern California beaches including Megalorchestia corniculata, M. californiana, M. minor, and M. benedicti. All four of these highly mobile crustacean species burrow into the damp sand near the high tide line and emerge to feed on kelp, damp paper, and even cardboard after dark. As vital parts of the beach food web, talitrids are preyed upon by birds and other animals. They are most active at night to avoid becoming an afternoon snack! Deep damp burrows create a cozy place for talitrids to remain safe and out of sight all day long. Unfortunately, widespread destructive practices, such as beach grooming disrupt their burrowing, shelter, and food supply.



Picture of an adorable talitrid amphipod for good measure

This wealth of unique intertidal life found on ungroomed beaches begs the question, what is a pristine sandy beach?  The definition of ‘pristine’ has to cease to be ‘empty combed sand’, and instead turn into ‘healthy ecosystems rich with life’. Global warming threatens our sandy beaches with rising sea level and higher temperatures, beach grooming mechanically removes sustenance and habitat, and humans need to truly realize our impacts on the places we love. For as much as we love our sandy beaches, we do not want to love them to death.


Turning up the heat on the painted sea urchin

— Written by Carlos Estrada

With global ocean temperatures and acidification on the rise, it is becoming increasingly important to study in what ways marine life may be affected. Slow-moving echinoderms, such as sea urchins, may be especially vulnerable due to their inability to migrate far distances in a short time. Ocean acidification has been shown to stunt the skeletal growth of purple urchin larvae whereas elevated temperatures increases their developmental rate (Padilla-Gamino 2013). If these increases in acidity and temperature continue, urchin larvae size may decrease, leading to further predation and low survivability. These effects on urchins are not only threatening to this species, but to the entire ecological system in which they belong. Sea urchins are important in keeping kelp forests in check and also serve as food to a variety of organisms, including the California sheephead and otters. Any detriment to urchin development may prove disastrous to this delicate balance, which is why this summer I will be studying an urchin species not previously studied in the Hofmann lab known as Lytechinus pictus, commonly referred to as the painted sea urchin.


Lytechinus pictus. Picture taken in the Hofmann Lab’s seawater room

Unlike the purple urchin, which is found as far north as Vancouver and as far south as Baja California, L. pictus is found from central California all the way down to the Ecuador. This makes L. pictus particularly interesting to study due to its tropical habitat and wide-ranging temperatures that fall anywhere between 9°C and 23°C. My project will attempt to answer a few questions regarding the effects of increased rearing temperatures on L. pictus larval development. The focus of this project will be to find the thermal tolerance of L. pictus and whether thermal tolerance varies across developmental stages by observing four different stages. This will allow me to see if there are any developmental stages that are most vulnerable to increased water temperatures. Morphometrics will also be involved by taking pictures of these different stages to check for differences in size or abnormalities. Lastly, but certainly not leastly, my project will have me look at whether thermal tolerance reflects expression of the heat shock protein hsp70. What makes this project so exciting (other than learning about invertebrate development, as well as new molecular skills!) is that very few studies have been conducted on L. pictus, making it feel as though I’m traveling directly into uncharted waters. So, hopefully, by the end of this summer we will have a better understanding of how echinoderms in warmer climates might fare when faced with increasing ocean temperatures.