Invasive species are a growing global economic and ecological problem. Invasive Indo-Pacific lionfish (Pterois spp.) are known to have extreme negative effects on coral-reef communities in the Bahamas, so understating their distribution within and among reefs, what limits their local movements, and the effects they have on native prey species...
Although only a minority of introduced species become established and have noticeable consequences in their new communities, some can displace native species, alter food webs, and cause local extinctions. Studying these invasive species can provide new insights into basic ecological questions as well as inform management strategies. Pacific lionfish (Pterois...
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MarkA. Hixon
Although only a minority of introduced species become established and
Biological invasions have been identified as one of the prominent drivers of global environmental change. In particular, invasive predators typically have substantial negative effects on populations of native prey, even driving species to extinction in extreme cases. However, beyond direct predatory effects, little is understood regarding the specific mechanisms by...
What makes invasive species successful, and how do they affect native populations and communities? I addressed these key questions in the context of the invasion of Atlantic coral reefs by Pacific red lionfish (Pterois volitans). To assess the role of parasites in contributing to the success of this invasion, I...
Patterns of settlement of larvae and population dynamics
of juveniles are poorly known for coral reef fishes. During
1987 to 1989, I studied these phenomena in the domino
damselfish (Dascyllus albisella), a species endemic to the
Hawaiian Islands. Larvae settle onto branching coral heads
as new recruits (10-15 mm in...
Early theoretical models for the evolution of male-female
pairing were based largely on studies of birds. These models
assumed that biparental care of eggs and young was an
essential component of pairing. However, male-female pairing
is also a relatively common social system in coral-reef
fishes, and biparental care of young...
Ecologists have long questioned why fluctuating populations tend to persist rather than go extinct. Populations that persist indefinitely are regulated by mechanisms that cause demographic density dependence, which works to bound fluctuation above zero. In a series of studies, I have sought to determine the processes and mechanisms that regulate...
I examined two aspects of the reproductive behavior of the garibaldi, Hypsypops rubicundus, a temperate marine damselfish with male parental care. My primary objective was to determine the relationship between female choice and male parental investment in the care of offspring. In particular, I sought to determine: (1) how the...
The threespot damselfish, Stegastes planifrons,
maintains individual territories that are clustered on
coral patch reefs. My objective was to understand the
effects of territory clustering on behavior and fitness.
Fish with territories in the center of a cluster had
(relative to edge fish): higher mating success (number of
eggs), higher...
Understanding the dynamics of open marine populations is difficult. Ecological processes may vary with the spatial structure of the habitat, and this variation may subsequently affect demographic rates. In a series of observational and experimental studies in the Bahamas, I examined the roles of emigration, mortality, and predation in the...
Predatory lionfishes (Pterois volitans and P. miles) were introduced to Florida waters during the mid to late 1980s, and eventually established self-sustaining breeding populations in the tropical western Atlantic. These invasive species are now widespread along the southeastern seaboard of the United States, across the Caribbean Sea, and in the...
Understanding the processes that influence the composition of animal communities is a central goal in ecology. Interactions between established residents and colonizing juveniles that affect the subsequent survival of juveniles may influence community composition. In a series of experiments on coral reef fish communities in the Bahamas and Australia, I...
Many marine fish populations are severely declining due to over-fishing, loss of both juvenile and adult habitats, and accelerating environmental degradation. Fisheries management and the implementation of marine protected areas (MPAs) and other conservation tools are currently hindered by large gaps in knowledge about larval dispersal and its subsequent effects...
Many species have complex life cycles in which a dispersive larval stage is
followed by a relatively sedentary adult stage. For such species, reproductive output
is often high and large variation in survivorship throughout early life-history phases
(eggs and larvae) can lead to dramatic fluctuations in recruitment which may in...
Studies of geographic variation are central to understanding ecological and evolutionary processes. Geographic variation in the shell of the black abalone (Halioth cracherodii), a marine intertidal gastropod, involves both
clinal and local variation along the eastern Pacific coast in the number and size of tremata (=respiratory pores) on the shell....
Predators are fundamentally important for regulating and driving prey population dynamics as well as structuring ecological communities. Over-exploitation of marine resources has caused dramatic depletions of predatory fish species and shifts in marine community composition, with attendant declines in productivity and diversity of marine ecosystems. Despite the important ramifications of...
There is increasing awareness that human activities are altering the ways that natural systems operate and that local shifts in species composition and abundance can lead to abrupt and irreversible global change. Therefore, understanding the processes that buffer biological communities from critical shifts and how our actions affect natural stabilizing...
The lionfish (Pterois volitans) is a successful invasive predator with large impacts on native fish populations in the western Atlantic. Lionfish predation may affect competition between prey species so it is important to understand whether lionfish display preferences between prey species. I investigated lionfish and native graysby grouper prey preference...
he Great Barrier Reef Marine Park is widely known as one of the best-managed marine protected areas in the world. The park is divided into different management zones, the most prevalent of which are marine national park zones, which are designated as no-take, and conservation zones in which some regulated...
Because many coral-reef fishes are observable in situ, are amenable to transplantation, have small home ranges and short generation times, they provide a excellent system to investigate many topics within general ecology, fisheries biology, and conservation biology. The primary goal of this dissertation was to use the coral-reef fishes system...
Natural disturbances and human activities can alter the benthic composition of coral reefs and other marine ecosystems. Reef fishes that associate with particular structures on the sea floor, such as coral heads, may be vulnerable to perturbations of those habitats. The spread of a newly discovered crustose alga (Ramicrusta sp.)...
Marine reserves are known to directly replenish overfished species. However, the
community-wide effects of reserves are less clear. I examined the community of coralreef
fishes in a large, fully protected marine reserve in The Bahamas: the Exuma Cays
Land and Sea Park. Visual-transect surveys provided estimates and comparisons of the...
Because global warming is predicted to increase the severity of El Niño events in the future, understanding how warmer temperatures affect seaweed growth and the animals associated with seaweeds is important for predicting how marine ecosystems will change. The Galapagos Islands of Ecuador are considered a living laboratory for studying...
The purpose of this study was to determine the effects of plyometric training on both spinal and supraspinal motor control as well as the rate of torque development (RTD) in healthy active females. Thirty-one subjects were recruited to participate in the study and participated in either the training or control...
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MarkA. Hoffman
The purpose of this study was to determine the effects of plyometric
Blackberries, genus Rubus, are an important Oregon agricultural commodity. In their fresh and processed forms, they offer many health benefits and may be able to help Americans better achieve fruit consumption recommendations because of convenience and pleasant sensory qualities. However, the susceptibility of blackberry products to contamination with bacterial pathogens...
Nisin, an antimicrobial peptide used in food preservation was
evaluated for thermal stability. Nisin retained antimicrobial
activity after having been heated at 121°C for seven hours.
Anhydrous nisin and concentrated nisin solutions (5-10 mg/ml) were
still active after having been heated up to 190°C or 230°C. When
exposed to high...
Objectives: To evaluate the effect of leg muscle fatigue on balance and to determine the contributions of the somatosensory, visual, and vestibular systems to balance of apparently healthy males and females. Design: Forty-two subjects were randomly assigned to either the experimental or control groups and then subdivided based on gender...
Objectives: To evaluate postural control in individuals with functional ankle instability using static, dynamic, and clinical balance tests. Also, to examine the relationships between the performances in each of these tests. Design: Postural control was evaluated with a single leg balance test, a balance test involving movement, and the star...
Objectives: To compare the neuropsychological concussion assessment testing
batteries of the Standardized Assessment of Concussion (SAC™) test and the
Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT™) test
and determine if the tests measure similar neuropsychological functions as well as
determine the test-retest reliability of the pre and post season measures...
The purpose of this research was to evaluate the effects of a long-term
static stretching program on flexibility and spinal reflexes in the
human soleus muscle. Day-to-day reliability over two days of H-reflex gain
(Hslp/Mslp) and pre-synaptic inhibition of spinal reflexes in the human
soleus was measured in an initial...
Hen egg white lysozyme is a hydrolytic enzyme effective at preventing the growth of Gram positive bacteria by degrading the bacterial cell wall to a point of cell lysis. Investigating lysozyme as a processing tool in wine to control the growth of lactic acid bacteria and malolactic fermentation has significant...
It has been suggested that cellular damage from oxygen radicals is one of the processes leading to cardio-vascular disease and cancer. Natural antioxidants prevent uncontrolled oxidative reactions by decreasing molecular oxygen levels, scavenging chain-initiating and chain-propagating free radicals, chelating metals, or decomposing peroxides. Beer is rich in antioxidants, derived both...
Lysozyme is a natural antimicrobial agent that is effective against many
food spoilage and pathogenic microorganisms by disintegrating their cell walls.
Immobilization of lysozyme has attractive applications for use in the food
industry: (1) The enzyme could be readily separated from treated foods and
beverages and re-used while the foods...
Eight foodborne pathogenic and spoilage Gram-positive bacteria were
evaluated for their spontaneous resistance frequencies to the peptide
antimicrobial nisin. In brain heart infusion (BHI) medium, nisin resistance
frequencies were in the range of l06 to l08 when exposed to nisin at
concentrations 2 to 4 times the minimal inhibitory concentrations....
Alfalfa sprouts have been implicated in several salmonellosis outbreaks in recent years. Electrolysis of a NaCl solution generates, in the anode side of a two-chamber electrolyzer, acidic electrolyzed oxidizing (EO) water which contains Cl₂, HOC1, dissolved oxygen, and it is characterized by a low pH and a high oxidation reduction...
To provide a possible alternative for the antimicrobial action of sulfur dioxide in winemaking, and address the issue of stuck fermentations, I studied the efficacy of chicken lysozyme (EC 3.2.1.17) as an antimicrobial in grape juice. Two different forms of lysozyme were used: native lysozyme (NL), that is known to...
There have been several epidemiological studies linking alcohol
consumption to a decreased risk of contracting illness from foodborne
bacterial contamination. To study this phenomenon, we examined the
survival of Escherichia coli 0157:H7 and Salmonella typhimurium in grape
juice and wine and then designed a model stomach to investigate the effect...
Female athletes exhibit three- to six-fold greater incidence of noncontact anterior cruciate ligament (ACL) injury relative to their male counterparts. The increased risk appears to stem from interactions between several risk factors, that can roughly be categorized as anatomic, biomechanical, hormonal, and neuromuscular. Neuromuscular risk factors have recently gained a...
Wine has recently been shown to be a possible protective agent against
microbial foodbome illness. The chemical environment of wine makes it difficult, if
not impossible, for microorganisms to survive. The low pH, high concentration of
organic acids, relatively high ethanol concentrations, and the potential for high levels
of sulfur...
Jalapeño peppers are usually consumed raw and fresh with minimal processing. They
contain antioxidants and bioactive compounds which are of human health benefits.
There have been an increasing number of reports of foodborne outbreaks attributed to
inaccessibility of sanitizers to Salmonella , E.coli and Listeria monocytogenes when
embedded in fruit...
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MarkA. Daeschel
Jalapeño peppers are usually consumed raw and fresh with minimal
Mechanisms of motor control and function are interesting to those from the medical, athletic training and sports performance professions primarily during the development of conditioning and rehabilitation programs. The aim of this study was to assess spinal control mechanisms in two groups of explosively trained, female athletes from a NCAA...
Despite years of research, females continue to have a higher incidence of non-contact ACL injuries. One of the major findings of this research is that males and females perform certain tasks, such as, cutting, landing, and single-leg squatting, differently. In particular, females tend to move the knee into a more...
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MarkA. Hoffman
Despite years of research, females continue to have a higher incidence of
We developed a scientific information management system to facilitate remote access and analysis of earth and space science data, using the Component Model of software development provided by the Java language. The data sets are part of the Earth Observing. System project, being carried out at the College of Oceanic...
The accurate simulation of snowpack deposition and ablation beneath forested areas is confounded by the fact that the vegetation canopy strongly affects the snow surface energy balance. The canopy alters the radiation balance of the snowcover, and reduces the wind speed at the snow surface. Data collected as part of...
β-lactoglobulin (β-Lg), bovine serum albumin (BSA), α-lactalbumin
(α-Lac), and β-casein were adsorbed onto
silanized silica surfaces of low and high hydrophobicity
for 8 h, and β-Lg and BSA for 1 h. The surfaces were
incubated in buffer for 0, 5, 10, or 15 h and then contacted
with Listeria monocytogenes...
The objectives of this project were to evaluate the efficacies of electrolyzed oxidizing (EO) and ozonated waters as antimicrobial agents for enhancing the microbiological safety of fresh strawberries (Fragaria x ananassa). The influence of sodium chloride (NaCl) concentrations used for preparing EO water was evaluated on their bactericidal activities against...
Cheatgrass (Bromus tectorum L.) is a widespread exotic weed in the Intermountain sagebrush steppe. An annual grass, it is highly prolific and very competitive with native perennial grass seedlings. A clipping experiment carried out at two cheatgrass-dominated sites (Lincoln Bench and Succor Creek) in eastern Oregon analyzed effects of defoliation...
Rapid change-of-direction tasks have been associated with non-contact anterior cruciate ligament (ACL) injuries and females are more likely to suffer this injury compared to males. The purpose of this investigation was to evaluate the biomechanical behavior of running and three rapid change-of-direction tasks and determine whether sex differences exist across...