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Masters Student- San Diego State University
Doctoral Scholarship Recipient, 2018
Seaweed Wars: Return of the Giant Kelp
A long time ago, in an ocean not so far away, a boat jetted across the calm swell of Point Loma. However, under the surface of the rolling waves a silent battle was raging. Algae just under the surface are locked in a constant fight for light and space. In recent years, foundational giant kelp, Macrocystis pyrifera, has been losing the battle for dominance on rocky temperate reefs. As a result, the giant kelp canopy off the coast of Point Loma, San Diego, California has dwindled. I dedicated my research to understanding exactly how other algae are winning the battle with giant kelp for space on the ocean floor.
Kelp forests are decreasing globally, and this loss is generally attributed to losing the tall canopy-forming species. Along the California coast, giant kelp forests are vanishing in response to a myriad of stressors, most of which are linked to winter storms. The tall giant kelp plants that you can see on the surface are particularly vulnerable to storms and the resulting wave force that rips them from the ocean floor. Following this disturbance, these kelp forests look drastically different. Low-lying opportunistic algae take advantage of this increased space and light, dominating the area previously covered with giant kelp. Think about walking through a tall redwood forest one day, and it turning into low-lying grasslands the next. This change in vertical structure has reverberating effects for invertebrates, fish, marine mammals, and humans that depend on these marine forests for both food and shelter. For us humans, giant kelp forests support lucrative fisheries, like California’s spiny lobster fishery, as well as protect our coasts from erosion through wave attenuation.
As a master’s student in Dr. Matthew Edwards’s Kelp Forest Ecology Laboratory at San Diego State University, I investigated how kelp species compete with each other. Specifically, I wanted to understand how smaller low-lying understory algae affect recovery of tall canopy species like giant kelp. In California, dense fields of “acid weed”, Desmarestia herbacea, appear following winter storms that remove the giant kelp canopy. These stands of acid weed can delay giant kelp canopy recovery up to 2 years following the storm! Acid weed is a fascinating alga because it possesses unique characteristics that may play an important role in its ability to affect giant kelp canopy recovery. Acid weed has the potential to affect neighboring algae through: 1) shading and blocking light from the bottom, 2) scouring or physical abrasion of the substrate (like sweeping a broom over a garden), or 3) allelopathy or “chemical warfare” resulting from acid weed’s acidic properties (the internal pH of acid weed is so low that it is similar to battery acid!). Using SCUBA, I out-planted tiny microscopic giant kelp individuals on tiles under treatments that isolated the effects of each mechanism. I used shade canopies, artificial acid weed, and natural acid weed individuals. Then, I monitored giant kelp recruitment, survival & growth over time.
My research found that different life stages of giant kelp are differentially susceptible to competitive mechanisms. Scouring is most important for giant kelp recruitment (the transition to just visible individuals), while shading and scouring are equally important for giant kelp survival and growth. Overall, this study helps to understand how algae compete with each other. Understanding how different life stages of giant kelp are affected by competition allows us to better predict recovery times for giant kelp following disturbances. It also provides information that can be used to conserve giant kelp and protect vulnerable life stages. As winter storms increase in frequency and intensity, the likelihood for opportunistic species, like acid weed, taking over and preventing giant kelp recovery will rise. This research helps us predict how different opportunistic species will affect the recovery of giant kelp following storms.
The AAUS research scholarship provided the opportunity to complete a diving-intensive research project off of Point Loma, San Diego, California. This project required mastering lots of rewarding underwater techniques as I like to call “underwater carpentry”. I drilled bolts into the ocean bottom using a pneumatic drill in order to secure the experiment, and I hammered tiles seeded with giant kelp and fake algae to the bottom (Image 4). Most importantly, this project allowed me to mentor and work with undergraduates both in the laboratory and diving in the field. Diving almost daily in the summer months provided an opportunity to observe firsthand the effects of storms on kelp forest resilience, and this sparked excitement to continue to understand changes to our local marine habitat.
So, the next time you are admiring a peaceful view of the ocean, just think about the battles being fought under the surface on the ocean floor. If you see tall giant kelp blades on the surface, know that giant kelp is resisting the imperial march of the acid weed and the resilient giant kelp are seeking to restore balance to the force…in the ocean.
Thank you for awarding me the AAUS research scholarship and supporting my research in the Point Loma kelp forest.
Doctoral Candidate- University of Washington
Doctoral Scholarship Recipient, 2018
The environmental DNA (eDNA) era for reef fish surveys?
Every time I get to SCUBA dive in Vava’u for my PhD fieldwork, I have to pinch myself to make sure it is for real. Vava’u is the most northern island group in the beautiful Kingdom of the Tonga. This archipelago sets halfway between the hotspot for fish diversity called the Coral Triangle, and the south Pacific islands of French Polynesia. I chose this location as the focal point for my research because of the gap in knowledge about their reef fish fauna, and more specifically about cryptobenthic reef fishes (CRFs). Cryptic, because they are good at hiding, and benthic because they live on or near a substrate. But the most striking characteristic of these fishes is their very small size. Adults are 1-2 cm long, which is a great adaptation if you want to make use of all the crevices that a coral reef ecosystem provides.
CRFs are extremely abundant, diverse, and form a link in the food-web by consuming the micro-invertebrates and algae in the reef ecosystem, thus transferring this energy to larger reef fishes. While CRF are an essential food resource in coral reef ecosystems, they have not received much attention because they are hard for researchers to see while conducting traditional underwater visual censuses. Currently the only way to determine the CRF community composition is to use ichthyocide or anesthetic stations and collect all the fishes in the habitats. Environmental DNA (eDNA) sampling would be a much easier and non-lethal way to determine what species of CRFs are present. But will this method work?
Environmental DNA sampling is an exciting and relatively new technique which is gaining extreme popularity for a multitude of studies that require detection of organisms from DNA fragments that are shed into the environment. This involves collecting samples of soil, water, even air, and using complex laboratory and bioinformatic analyses to detect what species of organisms are present in the sample. Studies of this kind can be very specific, like detecting presence of invasive species, to very large in scope, like inventorying all the organisms present in a specific environment. For my research question, I collected water samples directly from the reef substrate and concentrated on detecting the presence of a specific taxa (CRFs). This is the first study of its kind, as in situ eDNA samples have never been collected from coral reef habitats in conjunction with fish samples.
My PhD research revolves around phylogenetic and ecological aspects of CRFs in general, with a focus on the genus Eviota, family Gobiidae. During the last visit to Vava’u in December 2018 through January 2019, in part funded by the AAUS Doctoral Scholarship, I wanted to compare how many species of the CRFs I could detect from eDNA samples collected underwater with the actual CRFs I collected from ichthyocide stations.
The most exciting and fun part of this research is that I not only go to a beautiful tropical place, but get to SCUBA dive to collect my samples. Since obtaining my diving certification in the Canary Islands, Spain after my undergraduate degree in Marine Sciences, I have participated in many research projects involving diving, from cold waters of Alaska and Puget Sound, to tropical ones like the Caribbean and Micronesia. I feel very comfortable and safe working underwater. It is a very peaceful feeling, even when you are doing work that sometimes it may be very physically demanding. I feel that all the training I have received, first for my first recreational diving certification from the European organization CMAS, and more recently, AAUS scientific diver status through the training program at the University of Washington, has prepared me very thoroughly for my research endeavors.
I also enjoy the intensity of sampling in the field. One of the things I wanted to test about this new eDNA sampling was the feasibility of conducting this type of operation in remote locations with no scientific research stations. We had to setup our own lab facilities and protocols that would work for this type of research. A typical day in the field would start by getting in the water with my diving partner (and hubby, Dr. Ray Buckley) and all the gear (a lot of gear!) and heading to one of our main sampling sites. Once we got to an area with suitable coral bommies or coral rubble microhabitats, we would set up our gear on the bottom, and then our very choreographed underwater sampling ballet would start. The first thing was to select a desired microhabitat (either coral bommie or coral rubble), then we would get the modified syringes and extract a water sample right from the interstices of the coral head or the rubble . Once we had collected the eDNA sample, we would set up an enclosure surrounding the microhabitat, quinaldine anesthetic was delivered inside the enclosure, and after a couple of minutes the collection would start. An airlift device designed for this project was used to suction the specimens, some of them as small as 4 mm! inside labeled jars for each of the microhabitats. This way we could make sure we knew which eDNA samples corresponded with each microhabitat and the fishes in it. Once we were back to the surface, the eDNA and fish samples were placed in a cooler with ice and processed as quickly as possible.
The results from this testing of eDNA sampling, after processing the samples back at the labs at the University of Washington and the sequencing lab where the final analysis was done, indicated that this eDNA sampling was a poor method for detecting CRFs. Of the overall number of CRF species collected with the ichthyocide stations, about 40, the eDNA samples detected only four. Although it was disappointing to have such low level of detectability with the in situ eDNA sampling technique, these are very important results that define the potential limits of this emerging sampling technique. Negative results in science can sometimes be equally as important as positive findings. Nevertheless, it was encouraging to see that we were able to detect some of the species of CRFs that we collected with the traditional method. We also detected several of larger coral reef fish species, as well as a multitude of invertebrate’s species and other metazoans. My analysis of this eDNA sampling is still ongoing, and the process of going over every step of the procedures followed, from collection to the bioinformatic analysis of the sequenced data, is being scrutinized to determine how future projects using this eDNA technique could improve the detectability of this very important group of fish fauna, the cryptobenthic reef fishes.
I am extremely thankful for the support I received from AAUS for this research. I am also very lucky to have found very collaborative partners from the strong grassroots NGO, Vava’u Environmental and Protection Association, and the Government of Tonga. After I complete my PhD, I intend to continue our long-term collaboration with the local groups in Tonga doing underwater research, and to contribute to the knowledge of the functioning of our changing coral reef ecosystems from the perspective of the smallest fish inhabitants!
Master's Candidate- California State Northridge
Master's Scholarship Recipient, 2018
Sunlight enters the lab as I sit down to peer through the microscope. I always make sure to slowly increase the light, adjust the ocular lenses, set the magnification to 4x, and look carefully. After some fine adjustments, microscopic circular objects come into view. These tiny objects are algal endosymbionts (Symbiodiniaceae), and there are thousands of these cells living in the tissues of their coral hosts. Reef-forming corals are the foundation of the most elaborate and diverse marine ecosystems in the world, and share a complex symbiosis with their algal endosymbionts that dictates aspects of their physiological response to multiple environmental parameters. I will never forget my first time seeing these microscopic powerhouses in a coral tissue sample. Conducting this research enticed me to explore and understand coral ecophysiology for my master’s research project.
Coral reef ecosystems are hubs of biodiversity supporting a multitude of complex ecological interactions within our oceans. They captivate the imagination of millions of people and provide essential services for societies worldwide. Yet, human impacts are rapidly degrading them. Since these impacts are becoming ever more prominent, I want to dedicate myself to research that closes the gap between fascination with coral reefs and action. Over the past seven years, I have dedicated myself to countless hours of academic, volunteer, laboratory, and field work in that pursuit. These experiences fueled my passion for research-based science and mentoring, preparing me to share my scientific knowledge through collaboration and outreach. For my graduate research, my focus was to study how local and global anthropogenic stressors interact to affect coral physiology and thermal tolerance. More specifically, we investigated the influence of nutrient and sediment loading on coral thermal tolerance in Mo'orea, French Polynesia at the Richard B. Gump South Pacific Research Station.
Local scale stressors, such as nutrient and sediment loading, can make corals more vulnerable to global climate change by suppressing carbonate productivity (growth) and reducing their photosynthetic capacity. Interactions between global and local scale stressors have become more frequent and are projected to increase with anthropogenic climate change. Therefore, a better understanding of the ecological ramifications of thermal anomalies on coral reef ecosystems is necessary. While many studies have used respirometry (techniques for obtaining estimates of rates of metabolism) to determine the physiological response of numerous invertebrate species (clams, snails, insects, etc.) to temperature changes, the role of nutrient and sediment loading in determining thermal tolerance is unknown. To address this research gap, we collected coral fragments of Pocillopora acuta along a nutrient and sedimentation gradient in Mo'orea, French Polynesia to test their performance (photosynthesis, respiration, and calcification) across a range of temperatures (20-36°C) .
Quantitative Marine Ecology Lab, supported by the 2018 AAUS Master’s Research Scholarship, was to determine the influence of nutrient and sediment loading on coral thermal tolerance in Mo'orea, French Polynesia. We collected adult P. acuta coral colonies from our six sites along the northshore fringing reefs in Mo'orea by using SCUBA. At each site, we categorized coral abundances through the use of benthic surveys, deployed HOBO loggers to measure environmental parameters, installed sediment traps, and set up cages for coral recovery after fragmentation. I felt comfortable in completing my research due to scientific diving techniques strongly developed through my AAUS dive training at the Bermuda Institute of Ocean Sciences (BIOS) and CSUN. I was so thankful to be able to dive in such a dynamic tropical coral reef ecosystem.
The 2018 AAUS Masters Research Scholarship provided me with the means to travel to Mo'orea this past Summer 2019 to complete research pertaining to the first chapter of my master’s degree. Our study found that along an increasing nutrient and sedimentation gradient, metabolic responses of corals such as photosynthesis, respiration, and calcification significantly decreased. Mechanisms linked to thermal sensitivity, performance and overall rate processes were involved, illustrating the role of local scale anthropogenic inputs, and how they may exacerbate the detrimental impacts of global anthropogenic stressors on coral reef ecosystems. Once we understand these effects, management of land use, dredging, pollution and nutrient influx can be adjusted to reduce our impacts on coastal coral reef ecosystems experiencing the most damage from local scale stressors.
Not only has the 2018 AAUS Masters Research Scholarship provided me with the opportunity to complete my research in a tropical marine ecosystem, it helped me emphasize the importance of diversity in STEM fields by mentoring undergraduate students at CSUN and providing the opportunity to take an undergraduate student to Mo'orea to engage in hands-on laboratory and field research experiences related to my project. I was also able to collaborate with the Mo'orea Coral Reef Long-term Ecological Research (MCR LTER) site and the local community through the Coral Reefs of Mo'orea Education Program . Through this collaboration, we educated various public schools about the ocean, coral reefs, and the research of the MCR LTER program. Since island nations will be among the first communities to experience the detrimental effects of anthropogenic climate change, involving local communities in coral reef conservation initiatives can help protect the ecosystems they depend on for shoreline protection and food security. By understanding these mechanisms, my graduate research can help advise management strategies that protect coral reefs most vulnerable to these stressors. Ever since my first time observing the Symbiodiniaceae cells at work in coral tissue, I wanted to answer the question of how to preserve reefs. I believe my graduate research findings will help provide valuable insight to the scientific community that may bring us closer to reducing our impacts on coastal coral reef ecosystems.
Thank you AAUS for awarding me the 2018 AAUS Masters Research Scholarship. I appreciate the AAUS Foundation’s continued commitment to supporting graduate student research.
Master's Candidate- California State Northridge
Master's Scholarship Recipient, 2018
Afraid to reproduce? Measuring fish reproduction in risky environments
I have spent the past two summers studying the reproductive behavior of bluebanded gobies, Lythrypnus dalli. This species is highly abundant at Santa Catalina Island, CA, and female gobies reproduce by laying nests of eggs, which has allowed me to directly examine their reproductive responses to environmental conditions. Bluebanded gobies are constantly threatened by a suite of natural predators, particularly the kelp bass, Paralabrax clathratus, and it has been shown that gobies alter their behavior in response to this piscivore. My research aims to assess the short and long-term effects of risk on bluebanded goby reproduction through a series of caging experiments. This work has the potential to improve our understanding of how sublethal effects of predators, which are often overshadowed by lethal effects alone, may shape prey communities and behavior.
To test the effects of predators on reproduction in bluebanded gobies, I ran a manipulative experiment in Big Fisherman Cove, a marine reserve at USC’s Wrigley Marine Science Center (WMSC). I constructed a series of subtidal rocky reefs, stocked them with populations of 20 bluebanded gobies, and covered them with one of three cage types to simulate risk levels perceived by the gobies: large exclusion cages (low-risk environment), small exclusion cages (medium-risk environment), and small cages with side panels removed to allow for predators to move freely on and off the reefs (high-risk environment). I also stocked each reef with artificial nests (short PVC tubed lined with acetate), where female gobies laid eggs to later be fertilized and guarded by males. I performed SCUBA surveys twice a week for one month, during which I checked each nest for eggs and photographed the nests when eggs were present. I uploaded those nest photos to my computer and counted the eggs to compare reproductive output among the three treatments.
Though my analyses are ongoing, I’ve found that gobies lay the same amount of eggs on each reef, regardless of risk level, and that this pattern persists over time. These results are consistent with our behavioral observations, where gobies exhibited similar risk response behaviors for exposure times and foraging rates, even when subjected to different risk levels. Interestingly, egg production varied over time, with maximum output mirroring the natural reproductive cycle for this species. These findings posit that predation risk is having less of an impact on prey populations than has been suggested in other marine systems, at least in this species of reef fish. As mentioned previously, this study was conducted in a marine reserve, where predators reach high, natural abundances not achieved in unprotected areas. As such, we may have seen a different result had this study taken place outside of the reserve, where predator presence, both lethal and sublethal, has been altered by anthropogenic activities.
The AAUS scholarship has benefitted my thesis project immensely. Without this financial support, I would not have had the opportunity to gain invaluable field research, mentorship, and outreach experience at Catalina Island. Having the means to conduct research remotely allowed me to interact and foster professional relationships with top scientists and public stakeholders. I am grateful for AAUS and its continued support of graduate research. Thank you to all the fantastic volunteer divers and undergraduate researchers that have helped me carry out this project, and to my faculty mentors for their time and support during my thesis work. After my Master’s I hope to pursue more studies involving fitness responses and life history strategies of marine critters in a PhD program.
Lastly, if you are an undergraduate or graduate student interested in conducting field research at WMSC, check out their fellowship opportunities at this link: https://dornsife.usc.edu/wrigley/wrigleysummerfellowship/
Biological Science Master’s Candidate-Cal Poly, San Luis Obispo
Master's Scholarship Recipient, 2016
“Crunch... crunch... crunch.” I will never forget the first time I heard the unforgettable sound of a parrotfish grazing on coral reefs. Nearly two years after hearing that sound for the first time, I, along with my research team and hundreds of pounds of scientific dive equipment, headed from California to the Caribbean. The island of St. Croix, part of the U.S. Virgin Islands, was our destination; our mission: to get to know these charismatic parrotfishes on a more personal level. Our focus was to study the feeding behavior of the resident parrotfish species, who are important herbivores in coral reef systems.
Herbivory on coral reefs is a recent focus of research, as herbivores often consume algae in a way that is beneficial to the growth and recovery of live coral. Parrotfishes are an abundant herbivore on coral reefs and provide a plethora of positive impacts, particularly by consuming a significant amount of algae on the reefs. Interestingly, each parrotfish species, which come in an assortment of colors from stunning greens and blues (Image 1) to rainbow sherbet (Image 2), plays a unique role in their community. For example, the Queen parrotfish, Scarus vetula eats mostly small turf algae on complex reef structure, while the Yellowtail parrotfish, Sparisoma rubripinne prefers a bushy, brown macroalgae on a range of substrate types. Our current knowledge of parrotfish behavior comes from studies conducted in locations that have an abundance of each key parrotfish species. However, in some locations such as St. Croix, these fishes are an important source of nutrition, income and cultural value to the local fishing community and are thus subject to high fishing pressure and species loss.
My project as a California Polytechnic State University Master’s student in the Ruttenberg lab, supported by the Kevin Gurr Scholarship, was to determine whether fishing pressure and subsequent species loss has had an effect on parrotfish feeding behavior, and ultimately their positive impact on the coral reefs. We gathered feeding behavior data by using SCUBA and followed individual parrotfishes of each species for 20 minutes at three sites around the island (Image 3). During this time we recorded data such as what food each fish ate and how many bites it took, all while towing a surface float with a GPS unit to track how far the fish traveled (Image 4). A highlight of this study was to be able to dive the beautiful Buck Island Reef National Monument (Image 5). I was prepared for this challenging data collection technique thanks to my rigorous AAUS scientific diving training through the University of North Carolina Chapel Hill and experience as a dive technician prior to my graduate studies.
Although research is still ongoing, my data so far has shown that, broadly, parrotfish species in St. Croix play similar roles to the same species in other Caribbean locations. At a higher-resolution, we do see fine-scale differences in feeding behavior, but we are still working to determine if fishing pressure, species loss, or other environmental variables caused such differences. We also found that three key parrotfish species typically found throughout the Caribbean were absent from the reefs on St. Croix. Similar to the dysfunction and loss of productivity if a restaurant were to lose entire positions such as cooks, servers, and receptionists, this absence indicates the loss of important roles from these St. Croix reefs and potential decline in reef condition if these roles remain unfilled
The Kevin Gurr scholarship not only provided me the means to conduct a dive-intensive field season in the Caribbean to answer important ecological questions, but also gave me the opportunity to develop important relationships with members of the St. Croix fishing community, National Park Service and the University of the Virgin Islands. Over the course of three seasons in St. Croix, I developed relationships of trust and respect with local fishermen who granted me rare access in personal interviews to the family traditions and food-dependence associated with parrotfish and other species. Through conversations with these individuals, I learned the importance of incorporating both cultural and ecological value into metrics for fisheries management in collaboration with local residents. I hope to maintain the relationships that I made through this project and continue to promote discussions between the fishing community, scientists, and policymakers on how to manage the parrotfish fishery in St. Croix in a way that will result in measurable success for all stakeholders.
So, the next time you have the opportunity to snorkel or dive on a coral reef, take the time to listen for that unmistakable “crunch,” and observe the parrotfishes that are crucial to maintain the health of our beautiful coral reefs. You never know what interesting behavior you might witness!
Thank you AAUS for awarding me the Kevin Gurr scholarship and the opportunities that came from it.
Texas A&M University Galveston
PhD Scholarship Recipient, 2016
Jacque Cresswell is a PhD candidate in the Marine Biology Program at Texas A&M University’s Galveston campus. The AAUS Kathy Johnston Scholarship helped support her research on the benthic ecology of Bermuda’s underwater caves. Her main objectives are to complete a modern ecological analysis of benthic foraminifera and to investigate environmental change and primary succession of benthic foraminifera in the Palm Cave System in Bermuda. Specifically, she is exploring the impact of Holocene sea-level rise on the benthic environment in the Palm Cave System. Jacque is comparing microfossil data collected from surface sediment samples to cave sediment cores to analyze the changes in diversity and abundance of benthic foraminifera over time. Benthic foraminifera are single-celled protists that secrete a calcium carbonate shell which remains in the sediment long after the organism has died. Their fossil remains are widely used to reconstruct environmental change in the marine realm and also show excellent promise as environmental indicators for underwater caves.
The underwater caves of Bermuda have limited dry access. Therefore, SCUBA diving played a critical role in the execution of this research. Over a seven-day sampling trip, advanced cave diving techniques were used to collect 50 surface sediment samples, ten sediment cores, and hydrographic data (i.e., pH, salinity, dissolved oxygen, and temperature) from the Palm Cave System. Samples were then taken to Texas A&M University’s Galveston campus, where they are currently being processed and analyzed. Additional SCUBA diving will be necessary to collect more sediment samples. Such an extensive sample collection has greatly increased the impact of Jacque’s research and would not have been possible without the support of the Kathy Johnston Scholarship.