BGSO Spring Symposium

The Biology Graduate Student Organization Spring Symposium was held March 19, 2011. This year there were 24 presentations; 11 were MS students, 7 from the PhD in Ecological Sciences, and 6 from the PhD in Biomedical Sciences program. Obviously, with this number of students the topics were wide and varied, this made judging difficult; there was a tie for 3^rd place in the PhD student category.  Below are summaries of the top place finisher’s presentations

Top Presentations by a PhD student (Faculty mentor):

1.    Matthew R. Semcheski (Dr H. Marshall)

Dirty Little Secrets: An introduction to one of the most important, yet overlooked primary producers in Chesapeake Bay.

Primary production by microphytobenthos (MPP) is trophically important to a variety of micro- and macroheterotrophs in marine and estuarine habitats. In Chesapeake Bay, MPP facilitate survival and development of ecologically and economically relevant vertebrate and invertebrate fauna. MPP rates have been measured in habitats from sandy bottoms to tidal mudflats worldwide. However, productivity measurements in Chesapeake Bay are lacking, with few published studies in the last 30 years. This project aims to quantify microphytobenthic primary production rates in intertidal areas of lower Chesapeake Bay in relation to water column (phytoplankton) primary production (PPP). Eight sites throughout lower Chesapeake Bay were identified for measurements of PPP and MPP rates. Seasonal variations in community composition are examined in addition to MPP and PPP fluctuations.  MPP and PPP samples were processed for productivity following a ¹⁴C-incubation protocol. After one year, MPP and PPP varied among and between stations, with PPP showing much higher production rates per volume than MPP. Cell densities in the benthos were several orders of magnitude higher than those in the water column. Phytoplankton and microphytobenthic community composition fluctuated both seasonally and between stations, with phytoplankton production and composition consistent with historical Chesapeake Bay data.

2.    Amanda Ackiss (Dr. K. Carpenter)

Assessing the Population Structure of an Artisanal Fishery, Caesio cuning, in the Philippines and Indonesia

The redbelly yellowtail fusilier, Caesio cuning, has a tropical Indo-West Pacific range that straddles the Coral Triangle, a region of dynamic geological history and the highest marine biodiversity on the planet. Caesio cuning is a reef-associated artisanal fishery, making it an ideal species for assessing regional patterns of gene flow for evidence of speciation mechanisms as well as for regional management purposes. We evaluated the genetic population structure of Caesio cuning using a 382bp segment of the mitochondrial control region amplified from over 620 fish sampled from 33 localities across the Philippines and Indonesia. Phylogeographic analysis showed that sites in Western Sumatra formed a single population, resulting in pronounced regional structure between Western Sumatra and the rest of the Coral Triangle (FCT = 0.4596, p<0.0031). The species’ range and measures of genetic diversity at these Indian Ocean localities point toward low effective population size west of Sumatra and indicate that historic changes in sea level and ocean currents during periods of Pleistocene glaciation may have led to the divergence seen between Caesio cuning populations west and east of the Sunda shelf. East of Sumatra, there were additional significant genetic differences between the central sites sampled from the Philippines south to Java and Nusa Tenggara and the sites west of Halmahera to the edge of our sampling range at Cenderawasih Bay. Detected haplotype frequency differences in these sites may have arisen as a result of present-day ocean currents. These signatures, particularly the linage divergence between Western Sumatra and all other sampled sites, corroborate other studies in this region, indicating region wide mechanisms for lineage divergence across multiple taxa.

3.    Brian L. Stockwell (Dr K. Carpenter)

The species-area relationship and marine reserves: no reserve is an island

The argument over the effectiveness of a single large or several small (SLOSS) reserves has been continued for decades, yet analyses have focused on terrestrial examples. This study examined the effects of marine reserve area and networks on fish diversity.    Diversity from six mainstream reef fish families was collected from 28 no-take marine reserves within the central Philippines.   Diversity was plotted against reserve area, number of reserves within 10km, and area of reserves within 10km.  Regression analyses were then run to evaluate the strength of these relationships.   The linear regression analysis of diversity versus reserve area and diversity versus years of protection were both non-significant while the regression of diversity versus the number of marine reserves within 10km  and area of reserves within 10km were both strong (r² > 0.75) and highly significant (p < 0.001).  The greater diversity in networked reserves suggests a connection through larval dispersal.    The current system of many small but closely spaced marine reserves in the Philippines appears to be an effective strategy for improving and maintaining reef fish diversity.

·         Rachel Wigton (Dr. I. Bartol)

Turning Performance in Cuttlefish Sepia pharaonis

Using complex motions of fins that extend along the length of the mantle and pulsed jets that are directed through a flexible funnel, cuttlefishes are capable of making frequent turns when hunting for prey, evading predators, and navigating complex habitats. While cuttlefish appear to be quite adept at making rapid, tight turns during these maneuvers based on field observations, turning performance has not been quantified to date in any species of cuttlefish.  For this study, we recorded a variety of turns performed by cuttlefish Sepia pharaonis from lateral and ventral perspectives using two high-speed video cameras.  Various landmarks on the cuttlefish mantle, funnel, arms, and fins were tracked and parameters, such as minimum radius of the turning path (a measure of maneuverability) and angular velocity of turns (a measure of agility) were calculated using Matlab routines.  Arm movements, asymmetric fin motions, angle adjustments of the mantle and arms, and funnel movements all were employed to minimize the radius of the turning path, whereas vigorous jetting and/or rapid fin waves were closely correlated with the highest angular turning velocities.  The extensive repertoire of mantle, funnel, fin, and arm movements displayed by cuttlefish facilitates their ability to achieve high levels of maneuverability and agility. 

Top Presentation by a MS student (Faculty mentor):

1.    Robyn Nadolny (Dr H. Gaff/Dr R. Rose)

Survey of Ticks in Hampton Roads: Tick Populations

Ixodid ticks are vectors of emerging diseases throughout the southeastern United States, including Lyme disease, Rocky Mountain Spotted Fever, and erlichiosis. In order to understand which areas are most at risk of expressing high prevalence of these and other diseases in human populations, it is imperative to first have an understanding of the tick populations. We have begun a comprehensive long-term sampling effort to understand the distribution and composition of tick populations in the Hampton Roads area. 24 locations at 10 sites throughout Hampton Roads were sampled, and we collected more than 13,000 individual ticks during the summer of 2010. We found established populations of four ixodid tick species, including one species not previously known to have been established in Virginia. With this data we can identify populations that are at high risk of a tick encounter and provide insight as to which times of year are most risky for contracting a tick-borne disease. We are in the process of analyzing our collected ticks for disease so that we can identify areas where disease is endemic in the tick populations at high rates.

2.    Toufic Mayassi (Dr C. Osgood/Dr D. Gauthier)

Imaging biofilms on the Frontiers of Microscopy

Bacterial biofilms are dynamic systems that change over time and in response to changes in the environment.  Mycobacterium marinum are a type of nontuberculosis mycobacteria (NTM) known to form unique biofilms characterized by their cording morphology.  M. marinum can cause granulomatous infections in various fish species leading to financial hardships for affected fisheries.   M. marinum are also capable of infecting humans and have been isolated from commercial water sources, making them an interesting and relevant microorganism to study.  The work presented focuses on better understanding the biofilm growth of M. marinum using scanning electron microscopy (SEM) and atomic force microscopy (AFM).  Escherichia coli was used as a model system for growing biofilms and imaging with SEM and AFM.  Imaging of M. marinum with SEM was able to demonstrate the dynamic nature of biofilms with respect to time and exposure to different levels of nutrition, while also revealing their characteristic cording morphology.  The MBEC assay system was used to further investigate M. marinum biofilms along with the effect of different fixatives on the preservation and stability of the biofilms.  M. marinum biofilms imaged with SEM revealed extensive extracellular polymeric substances (EPS) when fixed with glutaraldehyde as opposed to formaldehyde.  Novel web-like EPS ultrastructure, which may play a structural role in maintaining biofilm stability, was also observed.  The MBEC assay system also allowed for the first images of M. marinum biofilms using AFM.  The results from this study provide groundwork for live cell imaging of M. marinum biofilms with liquid cell AFM in hopes of better understanding the structures of these systems in nature.

3.    Stephen Rice (Dr. R. Rose)

Patterns of transiency, sex bias, and body weight in open-habitat rodent populations.

Rodents belong to the most abundant and diverse order of the Class Mammalia, and as such have served as a common basis for study and modeling biological concepts.  Rodents are presumed to be philopatric with minimal vagility, except for the notion that juvenile males are the most probable subgroup to disperse.  To test these assumptions weight, reproductive status, and previous captures were evaluated to determine departure from unity, examine the proportion of each group in trappable populations, and identify differences between residents and transients.  Long-term data sets from CMR studies in Kansas and Illinois combined with trapping efforts in eastern Virginia were coded to evaluate the patterns of transiency, sex bias and body weight in six species of open-habitat rodent populations.  Preliminary analysis of Sigmodon hispidus from Kansas indicates male biased populations for residents and transients as expected.  No discernable difference in body weight was detected; however the total population consisted of 51% transients.  Further analysis is ongoing for populations and species in eastern Virginia, Kansas, and Illinois.