2008 College of Sciences Awardees (From March 1, 2008)

President's Award Recipients: Oral Presentations
Marty Kandes
Marty Kandes:  Masters Student,  Physics
Mentored by Dr. Michael Bromley
Multimode Interferometry of Bose-Einstein Condensates in a Circular Waveguide
ABSTRACT Marty Kandes

Multimode Interferometry of Bose-Einstein Condensates in a Circular Waveguide

Simple circular waveguides promise to be an ideal architecture for building high-precision matter-wave interferometers that exploit the coherent source of atoms provided by Bose-Einstein condensates (BECs). Using finite difference methods, we perform numerical calculations of the time-dependent Gross-Pitaevskii equation in one and two dimensions to simulate gravity-induced quantum interference for counterpropagating BECs in a circular waveguide. The aim of this work is to clearly understand the impact multimode excitations and nonlinear interactions have on the feasibility of interferometric measurements. Our results vividly illustrate many of the challenges to be expected in performing these types of experiments.


Michael Virata
Michael Virata:  Doctoral Student,  Cell and Molecular Biology
Mentored by Dr. Robert Zeller
Ascidians as a Novel Invertebrate Chordate Model for Alzheimer’s Disease
ABSTRACT Michael Virata

Ascidians as a Novel Invertebrate Chordate Model for Alzheimer’s Disease

Research involving Alzheimer’s Disease (AD) pathogenesis has involved the use of model systems to reproduce aspects of AD histopathology, particularly β-amyloid-containing plaques. A variety of invertebrate model systems (i.e. Drosophila and C. elegans) have been exploited to study the disease process but questions remain as to whether lower invertebrate species can provide a direct comparison in understanding human neurological diseases. We believe that the ascidian, Ciona intestinalis, may provide an ideal model system to study the mechanisms coordinating AD due to their close phylogeny, simplified chordate nervous system, rapid development, and ease of experimental manipulation. Genetic studies suggest that excess amyloid-β1-42 (βα1-42) production is the first step in AD pathogenesis. In humans, βα1-42 is generated by cleavage of the amyloid precursor protein (APP) by α-, β- and γ-secretases. The absence of a functional βα1-42 sequence and lack of equivalent β-secretases in current invertebrate AD models have limited efforts in studying APP processing in vivo. However, bioinformatic analyses revealed that the ascidian genome contains all the putative secretases implicated in processing. Our studies have shown that ectopically expressed human APP (APP695) is cleaved to generate β1-42 peptides that subsequently aggregate to form thioflavin S-reactive plaques within 24 hours post-fertilization. Ectopic expression of an APP695 mutant linked to early-onset, familial AD causes a significant increase in plaque formation compared to wild-type. Furthermore, βα-1-42-expressing larvae fail to respond appropriately to gravity suggesting that βα1-42γ misexpression in the ascidian nervous system causes changes in the settling behavior of the tadpole larvae. Our preliminary results suggest that ascidians may serve as a rapid drug screening platform for candidate therapeutic compounds of AD. More importantly, their close phylogenetic relationship with vertebrates suggests that they are a superior invertebrate model that may bring us closer to finding improved treatments or potential cures for neurological diseases including AD.


Natalie Gude
Natalie Gude:  Doctoral Student,  Cell and Molecular Biology
Mentored by Dr. Mark Sussman
Notch Signaling in Adult Mouse Myocardium
ABSTRACT Natalie Gude

Notch Signaling in Adult Mouse Myocardium

Introduction: The Notch network regulates multiple cellular processes, including cell fate determination, development, differentiation, proliferation, apoptosis and regeneration. Notch receptor activation generates the Notch Intracellular Domain (NICD), which translocates to the nucleus and turns on target genes, including Hes1. Notch activity influences HGF/c-Met receptor and PI3K/Akt signaling cascades. Delineating connections within the Notch/c-Met/Akt signaling axis in surviving cardiomyocytes following infarction is critical to understanding myocardial stem cell based signaling. Hypothesis: Stimulation of Notch activity by HGF increases activation of Akt, which enhances Notch activation, implicating a bidirectional feedback mechanism between Notch and Akt in border zone cardiomyocytes. The impact of HGF on Notch signaling and vice versa was examined in mice subjected to myocardial infarction and in cultured neonatal rat cardiomyocytes (NRCMs). To test a potential cardioprotective role for Notch activity in myocardium, NICD expressing adenovirus was injected into mouse hearts following infarction, and function was assessed by echocardiography and hemodynamic measurements. Results: Notch1 is activated in border zone cardiomyocytes coincident with nuclear c-Met. Intramyocardial injection of HGF enhances Notch1 and Akt activation in adult mouse myocardium. NRCMs treated with HGF or insulin exhibit increased levels of Notch effector Hes1 in immunoblots. NRCMs infected with NICD show a fourfold increase in phosphorylated Akt, and infarcted hearts receiving adenoviral NICD exhibit better function after six weeks then vehicle and EGFP virus injected controls, implicating Notch signaling in a cardioprotective role following cardiac injury. Conclusion: Notch activation in cardiomyocytes is mediated through c-Met and Akt survival signaling pathways, and Notch1 signaling in turn enhances Akt activity. This suggests a positive survival feedback mechanism between Notch and Akt signaling in adult myocardium following injury.


Rodrigo Negreiros
Rodrigo Negreiros:  Doctoral Student,  Computational Science
Mentored by Dr. Fridolin Weber
Structure and Thermal Evolution of Neutron Stars
ABSTRACT Rodrigo Negreiros

Structure and Thermal Evolution of Neutron Stars

Neutron stars are among the most enigmatic objects in the Universe. They possess the mass of our sun but are several billion times smaller than it. The matter in the cores of neutron stars is therefore compressed to densities that are several times higher than the density of atomic nuclei. Under such extreme physical conditions the conventional building blocks of matter as we know (atoms, protons, electrons) give way to new and widely unexplored states of matter, such as superconducting quark matter and novel particle condensates searched for in the most powerful terrestrial collider experiments. In this paper we study the thermal evolution of neutron stars in order to explore the properties of ultradense matter and the inner workings of these objects. Due to the extreme complexity of the thermodynamics and structure equations we must solve them numerically. All the calculations are performed in the framework of Einstein’s theory of general relativity, since neutron stars curve the geometry of space-time so strongly that classical Newtonian theory of gravity fails to describe their properties. We have found that the thermal evolution of the star might vary significantly, depending on its composition. We hope that with our research we will be able to further constrain the current models for the composition of Neutron Stars.


Shady Amin
Shady Amin:  Doctoral Student,  Chemistry
Mentored by Dr. Carl Carrano
The Role of Symbiotic Bacterial Siderophores in the Development of Primary Productivity in the Ocean
ABSTRACT Shady Amin

The Role of Symbiotic Bacterial Siderophores in the Development of Primary Productivity in the Ocean

The development of primary productivity in the marine environment is critical to the marine food web and the potential sequestration of anthropogenic carbon dioxide. While the phytoplankton themselves fix carbon dioxide into biomass, the microbial milieu that surrounds them in the so-called phycosphere, has recently been shown to be critically important to the growth and physiological well being of the algal cells. Indeed, many if not most, phytoplankton cultures cannot be maintained axenically. However, our understanding of the nature of the factor(s) produced by the bacteria and required for algal growth is still in its infancy. One attractive hypothesis concerning the nature of such an obligate interaction that we are pursuing is, that phytoplankton ‘hijack’ iron, an element that often limits their growth, from extracellular siderophores produced by their bacterial associates. Using various analytical, biochemical and spectroscopic techniques, we have isolated and characterized the dicitrate siderophore vibrioferrin (VF) from phylogenetically coherent clades of marine bacteria that were all isolated from geographically diverse strains of phytoplankton. In addition to functioning as a siderophore for the bacterial strains that produce it, VF exhibits a number of unusual properties including weak iron binding, considerable affinity for the element boron, and most surprising, extreme sensitivity of its iron complex towards photoredox reactions. The unique features of VF may provide important clues about the nature of the interaction between phytoplankton and their associated bacteria.





Provost's Award Recipients: Poster Presentations
Adam Renteria
Adam Renteria:  Masters Student,  Psychology
Mentored by Dr. Paul Gilbert
Age-related Changes in Conditioned Flavor Preference in Rats
ABSTRACT Adam Renteria

Age-related Changes in Conditioned Flavor Preference in Rats

Age-related changes have been documented in regions of the brain shown to process reward information. However, few studies have examined the effects of aging on associative memory for reward. The present study tested 7- and 24-month-old rats on a conditioned flavor preference task. Half of the rats in each age group received an unsweetened grape-flavored solution (CS-) on odd-numbered days and a sweetened cherry-flavored solution (CS+) on even-numbered days. The remaining rats in each age group received a sweetened grape-flavored solution (CS+) on odd-numbered days and an unsweetened cherry-flavored solution (CS-) on even-numbered days. During the acquisition phase of testing, the designated solution (CS+ or CS-) was presented to each rat for 15min daily across six consecutive days. On the preference phase, each rat received unsweetened cherry and unsweetened grape-flavored solutions simultaneously for 15min daily across four consecutive days. The 7-month-old rats showed a significant preference for the flavor that was previously sweetened during the acquisition phase (CS+) compared to the previously unsweetened solution (CS-) when the two unsweetened solutions were presented simultaneously during the preference phase of testing. In contrast, the 24-month-old rats did not show a preference and consumed roughly equal amounts of the previously sweetened (CS+) and unsweetened (CS-) solutions. Thus, the data suggest that the ability to form flavor-reward associations declines with increasing age, resulting in impaired conditioned flavor preference.


Brianne Bartlett
Brianne Bartlett:  Undergraduate Student,  Psychology
Mentored by Dr. Paul Gilbert
Temporal Order Memory Deficits in Presymptomatic Gene Carriers for Huntington’s Disease
ABSTRACT Brianne Bartlett

Temporal Order Memory Deficits in Presymptomatic Gene Carriers for Huntington’s Disease

Studies suggest that the frontal lobes may be important for accurate temporal order memory. Since the frontal-striatal loop is affected very early in the course of Huntington’s Disease (HD), temporal order memory may be particularly sensitive to neuropathological dysfunction in presymptomatic HD and may serve as a powerful tool for the early detection of cognitive changes in preclinical stages of this disorder. The participant group consisted of presymptomatic gene carriers less than 10 years away from estimated onset of HD, gene carriers more than 10 years away from estimated onset of HD, and normal controls. Participants were administered a visuospatial temporal order memory task on a computerized radial 8-arm maze. On the study phase, the participant was shown a random sequence of circles presented one at a time at the end of each of the eight arms. On the choice phase, the participant was presented with a circle at the end of two of the study phase arms and was asked to choose the circle that came earlier in the sequence. Parametric manipulations of the temporal metric were carried out by systematically changing the temporal separation lag between the two circles in the choice phase. Temporal order memory was impaired in gene carriers less than 10 years to HD onset relative to gene carriers more than 10 years to HD onset and normal controls; however, performance on the temporal order task increased as a function of temporal separation lag. There were no significant differences between gene carriers more than 10 years from onset and normal controls on the temporal order task. These results suggest that temporal order memory impairment is detectable in gene carriers less than ten years away from onset of HD.


Denise Buenrostro
Denise Buenrostro:  Undergraduate Student,  Biology
Mentored by Dr. Paul Paolini
Cross-platform Microarray Gene Expression Changes in Neonatal Rat Cardiocytes Responding to the Antidiabetic Drug Rosiglitazone
ABSTRACT Denise Buenrostro

Cross-platform Microarray Gene Expression Changes in Neonatal Rat Cardiocytes Responding to the Antidiabetic Drug Rosiglitazone

Recent reports regarding a possible link between use of the drug rosiglitazone and incidence of cardiovascular death from heart failure and myocardial infarct has created a controversy regarding this drug’s safety. A number of recent and ongoing clinical data studies indicate that the link is not statistically significant (Diamond et al., Ann. Int. Med. 147, 2007). However, earlier studies from our laboratory have demonstrated a positive inotropic effect of the drug via the short-term calcium signaling pathway (Shah et al. Cell. Physiol. Biochem. 15: 41-50; 2004) We have employed two different microarray platforms to study this response to rosiglitazone, first with Motorola/Amersham/GE BioSciences Uniset Rat I genomic microarray chips and a CodeLink Bioarray Flex Chamber, and more recently with Illumina’s BeadArray™ microarray technology, to examine the time course gene expression of neonatal Rattus norvegicus ventricular myocytes with rosiglitazone treatment. We have also used calcium ratio fluorescence microscopy measurements and kinetic analysis from contracting myocytes with video tracking to provide functional data (the calcium transient, sarcomere shortening) to relate to observed expression changes. Significantly regulated genes in rosiglitazone treatment include 671 genes involving lipid metabolism and 288 genes associated with fatty and monocarboxylic acid metabolism. While some gene expression changes from microarray data were validated by real-time PCR, we have now used cross-platform microarray data validation. Our results confirmed that fatty acid and lipid metabolism pathway genes are overrepresented with drug treatment. We are currently analyzing the data to determine the regulatory networks and pathways that are directly involved in the excitation-contraction coupling–the calcium signaling pathway. Observed early up-regulation of the cardiac ryanodine receptor gene, Ryr2, one of the SERCA genes, Atp2a3, and the NCX genes Slc8a1 and Slc8a2 could be responsible for the improved contractile behavior of rosiglitazone-treated cells.


Matthew San Pedro
Matthew San Pedro:  Undergraduate Student,  Biology
Mentored by Dr. Stanley Maloy
The Mechanism of Superinfection Exclusion of the P22 sieA Protein
ABSTRACT Matthew San Pedro

The Mechanism of Superinfection Exclusion of the P22 sieA Protein

Background: Susskind and Botstein (1979) have shown that the sieA protein expressed by a P22 lysogen is responsible for excluding superinfecting DNA. However, the mechanism of how sieA prevents superinfection is not known. Hofer, et. al. (1995) has shown that sieA localizes to the cytoplasmic membrane of Salmonella Typhimurium. Another protein that associates with the cytoplasmic membrane of Salmonella Typhimurium is the gp16 pilot protein that is closely associated with the P22 DNA (Perez, et. al. unpublished). Together with gp7 and gp20, gp16 is responsible for targeting, anchoring, and transporting the P22 DNA across the cytoplasmic membrane of Salmonella Typhimurium (Perez, et. al. unpublished). Since both gp16 and sieA are closely associated with the cytoplasmic membrane, I hypothesized that sieA interacts with gp16 to prevent superinfecting DNA from infecting the P22 lysogen. Methods: A triple ligation of gp16, GST-tag adaptor, and sieA was performed in the pET46 vector (Novagen). To confirm the association between sieA and gp16, the GST-tag of sieA was replaced with a Nus-tag. Protein-protein interaction between gp16 and sieA was studied using pull down and co-immunoprecipitation assays. Since there is a possibility that sieA interacts with the superinfecting P22 DNA, gel retardation assays were performed. Results: 6XHis-gp16 co-eluted with GST-sieA and co-immunoprecipitated with Nus-sieA. Nus-sieA also co-eluted with 6XHis-gp16 in the reverse pull down assay. The protein-protein interaction between 6XHis-gp16 and GST-sieA or 6XHis-gp16 and Nus-sieA, provide convincing evidence that gp16 associates with sieA. The gel retardation assays showed that sieA does not bind with DNA. Conclusion: The P22 sieA protein forms a complex with gp16. Since sieA does not associate with any DNA, the sieA protein excludes superinfecting DNA by directly associating and modifying the function of gp16. --- Acknowledgement: Funding provided by NIH/NIGMS SDSU MARC Program 5T34GM08303.


Norma Herrera
Norma Herrera:  Masters Student,  Psychology
Mentored by Dr. Claire Murphy
Neuropsychological and Behavioral Performance in Children with Sleep Disordered Breathing
ABSTRACT Norma Herrera

Neuropsychological and Behavioral Performance in Children with Sleep Disordered Breathing

Objective: Sleep disordered breathing (SDB) ranges from primary snoring to obstructive sleep apnea (OSA). OSA affects 1-3% of children, with up to 10% being primary snorers, and is associated with significant morbidity. SDB has serious sequelae in adults; however, few studies have examined SDB morbidity in children. One sequela suggested in the pediatric SDB literature is a neurobehavioral deficit. Other potential negative sequelae in children are deficits in neuropsychological functioning. Furthermore, the relationship between SDB and olfaction has not been investigated in children. Participants/Methods: The present study examined the effects of SDB on neurobehavioral, neuropsychological, and olfactory function before and after surgical intervention for children with SDB. The surgical patients included 26 male and 16 female children. Age and gender match controls were recruited from the surrounding community. Children 4-12 years of age were tested using standardized neurobehavioral, neuropsychological, and psychophysical tests. Surgical and control subjects underwent a multi-channel home sleep test the night of their testing session. Results: Analysis of variance, using repeated measures, revealed significant neurobehavioral differences between the SDB and control groups. Trends toward poorer performance for the surgical groups were detected when compared to the control group on neuropsychological indices, though in this sample size the effects were not statistically significant. Conclusions: Thus, the findings from the present study suggest that further investigation of neuropsychological deficits in pediatric SDB patients is warranted.


Ronald Schneider
Ronald Schneider:  Masters Student,  Psychology
Mentored by Dr. Jennifer Thomas
Postnatal Choline Supplementation Reduces the Severity of Working Memory Deficits in Rats Exposed to Alcohol during Development
ABSTRACT Ronald Schneider

Postnatal Choline Supplementation Reduces the Severity of Working Memory Deficits in Rats Exposed to Alcohol during Development

Prenatal alcohol exposure can adversely influence the development of the fetus, leading to a range of physical, neuropathological and behavioral alterations. Given that women continue to consume alcohol during pregnancy, there is a need to identify effective treatments to reduce the severity of fetal alcohol spectrum disorders (FASD). We have previously shown that pre- and/or early postnatal choline supplementation can attenuate ethanol’s adverse effects on learning and memory, as well as activitylevel. However, it is not known if choline administered later in life, during late adolescence or early adulthood, would have similar beneficial effects. Sprague-Dawley rats were exposed to binge-like alcohol (6.0 g/kg/day) via intubation from postnatal days (PD) 4-9, a period of brain development that is equivalent to the human third trimester. Sham intubated and non-intubated controls were included. On PD 40-60, a period of development equivalent to adolescence/young adulthood, subjects were treated with 100 mg/kg/day choline or saline vehicle via sc injection. Beginning on PD 65, spatial learning was assessed with the Morris water maze and beginning on PD 84, subjects were trained on a working memory version of the water maze. Ethanol exposure significantly impaired performance on both the spatial learning and working memory versions of the Morris water maze. Choline administration did not significantly improve performance of ethanol-treated subjects on the spatial learning version of the Morris maze, but it did significantly improve performance on the working memory version. In fact, ethanol-exposed subjects treated with choline performed at control levels on the working memory task. These data suggest that choline supplementation may effectively mitigate some of ethanol’s effects cognitive performance, even when administered later in life. These data have important implications for the treatment of individuals exposed to prenatal alcohol exposure. ---Supported by AA12446.


Ryan Robinson
Ryan Robinson:  Undergraduate Student,  Psychology
Mentored by Dr. Lisa Kath
The Mediating Role of Job Satisfaction in the Job Stress-Intent to Quit Relationship: A Study of Grocery Store Employees
ABSTRACT Ryan Robinson

The Mediating Role of Job Satisfaction in the Job Stress-Intent to Quit Relationship: A Study of Grocery Store Employees

Workplace accidents cost companies in the U.S. billions of dollars each year. An important factor in preventing workplace accidents is an employee’s personal motivation to engage in safe behavior. We were interested in what factors in the employee’s workplace environment influences his or her motivation to engage in safe behavior. Some of these workplace environment factors included organization safety climate, store safety climate, department safety climate, safety peer pressure, and tenure with the organization. Survey data was collected from 965 workers employed at a regional supermarket chain in the Northeastern United States. Hierarchical multiple regression was used to analyze factors from a variety of levels within the organization (i.e., organization, store, department, job, and individual). Results showed there was no significance for variables at the organization-level or store-level. At the department level, however, safety climate and safety peer pressure were significant predictors of safety motivation. In addition, at the job-level, perceived safety of the physical work environment and the extent to which job demands conflict with safety were significant. At the individual-level, only age was significant, with older employees having higher safety motivation. These results suggest that to increase individual safety motivation, organizations should primarily focus on department and job-level factors in creating and enhancing safety climate. Replication of the current study in another industry is necessary to determine whether the current findings are specific to this industry and/or organization.


Shea Gluhm
Shea Gluhm:  Undergraduate Student,  Psychology
Mentored by Dr. Paul Gilbert
Emotional Memory for Faces and Words in Healthy Younger Adults
ABSTRACT Shea Gluhm

Emotional Memory for Faces and Words in Healthy Younger Adults

Prior studies suggest that memory for highly emotional stimuli is enhanced compared to neutral stimuli. In young adults, studies have found that recall memory for negative stimuli is better than positive stimuli. However, the effects of emotion on recognition memory is still highly debatable. The present study examined recognition memory and recall for neutral, positive, or negative facial expressions and words in healthy young adults. A total of 20 participants were given computerized memory tests comprised of face or word stimuli. The participants were counterbalanced throughout the study. In the study phase, the participant rated the intensity of the word or face on a seven point likert scale. Word recall was assessed directly after the study phase for words. The participant was asked to orally list all the words remembered from the study phase. In the recognition phase, the participant was presented with a word or face and was asked to indicate if it was present earlier in the study phase. For recall, negative words were recalled better than neutral words, p < .01. However, there was no significance found for positive words. In recognition memory, positive faces were correctly recognized more for the neutral faces, p < .03, and negative faces, p < .01. No significance was found for positive, negative, or neutral words. Therefore, recall memory supported prior research in showing an emotional enhancement for negative words. Recognition memory showed an emotional enhancement for positive faces, but not for words. This research was supported by SDSU University Grants Program.


Tanya Diaz
Tanya Diaz:  Undergraduate Student,  Psychology
Mentored by Dr. Paul Gilbert
Effects of Normal Aging on Temporal Order Memory for Sequences
ABSTRACT Tanya Diaz

Effects of Normal Aging on Temporal Order Memory for Sequences

Episodic memory has been found to be impaired in aging adults. A specific component of episodic memory that has been shown to be particularly sensitive to aging is temporal order memory. Research has found that the temporal and frontal lobes are affected as a result of the normal aging process. These regions, specifically the hippocampus and the prefrontal cortex, also are involved in temporal order and sequence memory. Therefore, temporal sequence tasks may be helpful for the early detection of cognitive dysfunction. The present study compared healthy young and older adults on a visuospatial temporal order memory task involving parametric manipulations of the temporal metric. Temporal order memory was tested using a computerized radial 8-arm maze presented on a computer screen. During the sample phase, a circle appeared at the end of each arm one at a time in a random sequence. Followed by a choice phase, in which two circles were presented simultaneously in two different arms of the maze. Participants had to choose which circle appeared earliest in the sample phase sequence. Choice phase circles were presented randomly as a function of 0, 2, 4, or 6 temporal separation lags. Temporal separation lags represent the number of circles that occurred during the sample phase sequence between the two circles. Previous research has found that items that occur closer in time are more difficult to differentiate than items that occur further apart in time. The study found that performance of all participants improved as a function of increased temporal separation lags. Older adults showed significant impairments compared to young adults across proximal and moderate temporal separations, but improved on distal separations. Thus, temporal order memory is impaired in older adults compared to young adults. The findings suggests that tasks involving temporal order memory for sequences may be used as a tool sensitive enough to detect early cognitive impairments in healthy older adults.





Dean's Award Recipients: Oral Presentations
Hau-Jian "Jason" Liu
Hau-Jian "Jason" Liu:  Undergraduate Student,  Physics
Mentored by Dr. Richard Morris
Magnetic Field Comparison Between Helmholtz Coils and a Simulated Three-coil Array
ABSTRACT Hau-Jian "Jason" Liu

Magnetic Field Comparison Between Helmholtz Coils and a Simulated Three-coil Array

Helmholtz coils are a two coil array commonly used to produce a homogeneous magnetic field over a relatively large region about the center of the coils. In a recent article in The Review of Scientific Instruments three physicsists in China performed a computer simulated model of a three coil array superior in homogeneity to the two coil array. The simulated parameters used in the model were extended to four significant figures. We have constructed a three coil array limited to two significant figures. We will compare the homogeneity of constructed three coil and two coil array.


Levi Lewis
Levi Lewis:  Masters Student,  Ecology
Mentored by Dr. Todd Anderson
Predation in Eel Grass Beds: Do Trophic Manipulations Result in Cascading Effects?
ABSTRACT Levi Lewis

Predation in Eel Grass Beds: Do Trophic Manipulations Result in Cascading Effects?

Seagrasses provide important nursery grounds to fishes and invertebrates throughout the world. Although much work has been conducted in these habitats, it remains unclear how trophic interactions influence ecosystem function in seagrass beds. Previous work suggests that an abundance of fishes that feed on invertebrate grazers may, in turn, allow epiphytic algae to grow and smother seagrasses. The aim of our research is to explore the importance of microcarnivorous fishes in the functioning of eelgrass (Zostera marina) habitats in San Diego Bay, California. We conducted a 12-wk field experiment in summer 2007 for which we manipulated the abundance of microcarnivorous fishes and observed their direct and indirect effects on invertebrates, algae, and eelgrass performance. We used the following four treatments: fish enclosures, fish exclosures, open plots, and cage controls. Contrary to our expectations, our results indicate that fishes had positive indirect effects on eelgrass performance (e.g., growth); possibly by directly removing invertebrates which appeared to damage eelgrass leaves. These results suggest that microcarnivorous fishes exert top-down effects that ultimately benefit eelgrass.