Marine Science

Marine Science

Marine Science Senior Theses 2012

Evidence of abrupt climate change in the Gulf of Mexico during the last glaciation

Student: Charles S. Adams

Thesis Committee: David Hastings (Chair), Benjamin Flower, Gregg Brooks

The objective of this study was to analyze core MD02- 2551 from Orca Basin, Gulf of Mexico (GOM) segment 16.50m to 21.00m and construct a paleoclimate history for the GOM of sea surface temperature (SST) and δ18  Osw  using Globigerinoides ruber. Data was compared to core MD02-2551 section processed by Heather Hill (2006) and combined analysis conducted. The average temperature measured over core section 16.5m to 21.0m was 24.52°C with a relative range for temperature of 2.94°C  over  the core-section. This value compares to the average SST found by H. Hill (2006) Of 24.98°C. Both core sections had low standard errors of ±0.07°C and ±0.032°C respectively demonstrating consistent sampling and analysis methods. Temperature fluctuated through ±3.0°C across the two core sections with approximately a 6000 year oscillation around the average 24.9°C. The two local-minima values for SST are 23.1°C and 24.8°C while the local-maxima are 26.6°C and 29.6°C for the two oscillations present on this segment.

Analysis of d18 Osw trends between the two core sections show relative overall decrease in average d18 Osw values between 23,239 YBP to 28,761 YBP (the age range of this study) and H. Hill (2006) through combined core-bottom sections that may represent differences in the researcher’s precision or methods. The average value for the section processed in this study is just under 50% the d1 Osw average calculated for the H. Hill (2006)j section. The approximate onset for H2 is evaluated at 24,000 YBP and can be observed during a rapid decrease in d18 Osw  at 24,700 YBP, which may represent a possible Laurentide Ice Sheet meltwater pulse.

While the scope of this study was limited to a small section of core MD02-2551 the possible signature of Heinrich Event 2 will add to our understanding of climate cycles and further our ability to predict future trends.

Neurological effects of three common pesticides on Caenorhabditis elegans and the development of an oxidative stress assay

Student: Erik W. Burde

Thesis Committee: Denise Flaherty (Chair), Steve Denison, Katherine Sharp

As pesticide usage increases to maintain abundant harvests, humans are exposed to increasingly higher doses of pesticides. While the effects of single exposure of pesticides are very well studied, the combined effects of pesticides is an area that requires more research, especially since humans are exposed to these compounds daily. Three pesticides, indoxacarb, carbaryl, and chlorpyrifos, were combined at sub-lethal doses and applied to Caenorhabditis elegans to observe damage to acetylcholine signaling and oxidative stress damage. It was determined that carbaryl and chlorpyrifos had cancelling effect, suggesting a biofeedback loop or an organic reaction between the pesticides in solution. Indoxacarb and carbaryl did not change acetylcholine transmissions when combined and non-conclusive data was observed for the combination of indoxacarb and chlorpyrifos. Usage of a florescent microscope assay to determine oxidative stress was analyzed and modified for a more accurate depiction of stress damage caused by the pesticides.

Temperature and salinity effects on the pre-feeding life-stages of summer flounder, Paralichthys dentatus

Student: Corie Charpentier

Thesis Committee: William Szelistowski (Chair), Christopher Chambers, Jeannine Lessmann

Water temperature and salinity are environmental factors which affect the early life-stages of marine teleosts and are expected to fluctuate with changes in climate, especially in near-shore habitats where many resource species spawn and spend their early lives. Although temperature and salinity are expected to impact the embryonic development of marine fish, we lack robust quantitative descriptions of these effects on the early life-stages of many important resource species. In this study, I subjected embryos of summer flounder (Paralichthys dentatus) to a wide yet relevant range of constant temperatures and salinities and monitored effects on survival and developmental rate of eggs, size and condition of hatchlings, and persistence of pre-feeding larvae.  Adult summer flounder collected from New Jersey inshore waters were strip-spawned, and 40 100-mL beakers with 100 fertilized eggs each were incrementally transferred to 10 target constant temperatures (12.5 - 26.0 °C) and 4 salinities (20, 25, 30, and 35 ppt). Survival to hatching was maximal between 12.5 - 22 °C and decreased at temperatures     > 22 °C but was not significantly affected by salinity. Developmental rate increased nearly linearly with temperature (from 36 h to 6 d at 12.5 and 26.0 °C, respectively) but was unaffected by salinity. Hatchlings from the warmest temperatures were smaller and those that experienced the warmest temperatures and lowest salinities had less yolk reserves. Persistence of larvae after hatching was independent of the embryonic incubation temperature and salinity. These results provided accurate and realistic estimates of early life history traits, which can be used to parameterize population process models. They also suggest that changes in the thermal environment due to climate change could significantly affect the timing of critical events in the early-life stages of summer flounder, survival to hatching, and the size of young larvae, which in turn could affect their likelihood of recruitment.

Mass balance analysis of oyster biodeposits at Marinetics Oyster Farm, Cambridge, Maryland

Student: Sarah Kwon

Thesis Committee: David Hastings (Chair), Amy Wright, David Grove, Denise Flaherty

A mass balance, control volume model of the Marinetics oyster farm in Cambridge, Maryland, USA, has been constructed to predict the fluxes of biodeposits out of the farm and the biodeposition rate within the farm. A sequence of calculations at quasi-steady state approximate the entire tidal cycle.  Equations expressing fluxes into and out of control volume as well as internal sources and sinks are parameterized using field measurements. Measurement techniques include settling experiments, erosion experiments, current meter measurements, and sediment trap deployments. Results indicate that the area is ebb dominated; ebb currents are stronger and the ebb lasts longer than the flood. During ebb tide a significant fraction of the biodeposits are predicted to leave the farm before hitting the bottom. Accounting for resupension greatly increases the amound of export. During flood tide, less material is directly exported and much less is resuspended. In warmer months the model predicts that most of the biodeposits remain beneath the farm, but may be flushed out during episodic wind and wave events.  In cooler months, more material is predicted to be exported from the farm than is deposited by oysters. This creates a seasonal flushing effect with buildup of biodeposits during the warmer months and a flushing during the cooler months.

Identifying bioactive compounds from U.S. algae biofuel ponds

Student: Zoe G. O'Donoghue

Thesis Committee: David Hastings (Chair), Richard Schnabel, Yelda Hangun-Balkir, Peter Moeller

Biofuel derived from microalgae is a growing industry in the United States, but serious complications can potentially arise. Harmful Algal Blooms (HABs) cause millions of dollars worth of damage every year to global and local fishing industries. They also affect water quality, as well as animal and human health. Due to the extreme toxicity of HABs, it has become necessary to monitor algae from open-air biofuel ponds for known and novel toxins. Algal growth ponds are typically placed near larger bodies of water with high conductivity and/or are exposed to unknown factors in the natural ecosystem, creating the possibility for contamination via water-born or cyst transportation. Previous research has found that an uncontrolled environment has been involved in a toxic event in a preciously non-toxic pond. Due to rising concern over this issue, a number of biofuel generating organizations have provided samples from their raceway algal ponds for analysis. A sample taken from a supposedly non-toxic algal growth pond was extracted, tested and demonstrated to be bioactive on both mouse neuronal blastoma and rat pituitary cells. HPLC, LC/MS, bioassay0guided fractionation, and NMR analysis were used to further identify specific biologically active compounds found in the sample. Specifically, a nonpolar fatty acid was isolated and fully characterized. Additionally, it was determined that the pond sample contained at least two other distinct, and more relatively polar, bioactive compounds.

Trace metals as indicators of oil contamination in marine and beach sediments following the Deepwater Horizon blowout

Student: Tara Roeder

Thesis Committee: David Hastings (Chair), Gregg Brooks, David Duncan

We present an analysis of Gulf of Mexico marine and beach sediments impacted by the 2010 oil spill to determine if vanadium and nickel enrichment can be used as a proxy for oil contamination. Results show vanadium and nickel enrichment cannot be used successfully as a proxy for oil contamination in marine sediments. Possible explanations include that the oil never physically impacted the sediments sampled, the vanadium and nickel concentrations in the oil are too low to be detected, and/or the oil has been heavily diluted by the high rate of sediment accumulation that occurred shortly after the spill. Results of numerical modeling show contamination could be detected in a sample containing as low as 2% oil and 98% sediment if vanadium enrichment in crude oil is 400ppm. Beach sand samples with visible oil contamination were found to have elevated concentrations of vanadium and nickel relative to their clean counterparts. We believe vanadium and nickel enrichment in beach sands can serve as a more successful proxy because the beach sands sampled contain lower background levels of vanadium and nickel than marine sediments collected in the Gulf of Mexico.

Seasonal and interannual oceanographic variability in Kachemak Bay, Alaska

Student: Robert Skoumal

Thesis Committee: Laura Wetzel (Chair), Kris Holderied (NOAA NOS, David Hastings, Stephen Weppner

Cross-bay oceanographic surveys were conducted in the subarctic estuary of Kachemak Bay, Alaska, from June to October of 2011 to investigate seasonal and interannual oceanographic variability. Oceanographic data were collected during repeated mid-bay transects with a Sea Bird Electronics SEACAT 19plus conductivity-temperature-depth (CTD) vertical profiler. The results from the 2011 survey were compared to similar data collected in 2008 and 2009. The CTD data were compared with water quality and atmospheric conditions collected by sondes and meteorological stations located in the Bay to propose factors affecting seasonal and interannual oceanographic conditions. The freshwater contribution from the Harding Icefield was found to have a significant effect on the creation of a halocline and vertical stratification during the spring and summer months. A 60-fold increase in river-flow was observed when average air temperatures went above freezing, resulting in glacial and snowmelt. Minor changes in precipitation, solar radiation, temperature, and wind speed could have tremendous impacts on the physical properties, biological systems, and economic resources of Kachemak Bay; one more day of above freezing temperatures in a year could result in tens of thousands of additional cubic meters of freshwater input into the Bay. The analysis of seasonal and interannual water patterns provides an important baseline for the understanding of oceanographic variability within the estuary and is being used to plan future oceanographic monitoring within Kachemak Bay. The data collected from the study were also used to determine the effectiveness of capturing relevant oceanographic variability within the Bay using shore-based water quality monitoring stations at Homer operated by the Kachemak Bay National Estuarine Research Reserve. Given the large amount of data from the sonde and the difficulty in sampling year-round with the CTD, a model fit between the sonde and CTD data was attempted. The model fit was found to replicate general trends but failed to match short-term variability. Continued CTD, atmospheric, and shore-based water quality sampling with the expansion of river flow monitoring would result in a greater understanding of the impacts of freshwater input into Kachemak Bay.

Assessing sources of variability associated with Pb-210 geochronology by gamma ray spectroscopy

Student: Alexandra Valente

Thesis Committee: Denise Flaherty (chair), Jonathan Cohen, Greg Gerdeman

Lead-210 (210Pb) dating has become a common technique to determine periods of ecological change. Age dating of sediment cores using this method has become critical for determining sediment accumulation rates and precise timing of events that have occurred throughout the geologic past. The determination of the short-lived radioisotope 210Pb, by gamma emission, has undergone several modifications in the past three decades in order to achieve accurate results, but there are still variables that have not yet been systematically tested. This study examined the effects of radioactive equilibrium, sediment texture and sample mass.

In order to understand how these variables compare with the accuracy and precision of the equipment the detector variability was measured by counting multiple samples several times, observing the reproducibility of activities and how they compare to known activities. The theory of radioactive equilibrium is based on the assumption that a sediment sample requires thirty days for the 222 Rn and 210Pb isotopes to reach equilibrium before the sample can be counted for 210Pb activity. To test for this variability, standards were counted over a 40-day period. Errors associated with sediment texture were tested by comparing the activities among three different compositions of a standard mud and sand mixture (25%, 50% and 75% sand) at four different masses (10, 20, 30 and 40 grams). Activities of sediment samples from Charlotte Harbor, FL were then normalized to the percentage of mud and clay in each sample. Errors associated with mass were assessed using sample masses that ranged from 1 to 50 grams and observing how they compare to the known activity.

Results show that variations in radioactive equilibrium fall within the variability of the technique. Sample texture influences activity, but simply normalizing activities to fine-grained sediment content assuming a linear relationship, does not achieve more accurate results. Variations in sample mass affects the precision of the activities, with a threshold at ~ 12 grams, which requires a correction in the efficiency calibration.

Preliminary assessment of population genetic structure in the bonnethead shark (Sphyrna tiburo) from the eastern Gulf of Mexico

Student: Lauren Van Woudenberg

Thesis Committee: William A. Szelistowski (Chair), Michael D. Tringali, Gregory L. Gerdeman

Sphyrna tiburo, the bonnethead shark, is a small estuarine member of the hammerhead shark family which grows to about 1m in length. Previous studies have shown that bonnetheads from several sites in Florida (Florida panhandle, Tampa Bay, Florida Bay) exhibit life history differences in traits such as growth rate, age and size at maturity, and fecundity. Because bonnetheads are relatively site-specific and may not exhibit the long migrations observed in many other shark species, these differences may reflect evolved adaptations at each site. If so, it may be possible to detect genetic population structure in sharks from this region. In this study a total of 90 bonnethead were sampled from Tampa Bay and the Panhandle to examine whether the sharks are separated into two genetically distinct populations. Eleven non-linked, microsatellite loci were used to assess relatedness. Allelic richness and gene diversity were low for both the Tampa Bay sample and the Panhandle sample, but within the range found in other shark population genetic studies. Only one significantly positive FIS value was found for Tampa Bay indicating a heterozygote deficit at that locus, and no significant FIS values were found for the Panhandle loci. A low FST value indicated no correlation of alleles within samples suggesting no structure between the two sample sites. Similarly, a 99.78% posterior probability that all specimens belong to one population, and a single cluster formed in a FCA plot suggested that one well-mixed population of bonnethead sharks occurs in the eastern Gulf of Mexico. The observed differences in life history traits are therefore most likely due to phenotypically plastic responses rather than evolved differences.

Carbon elemental and stable isotopic compositions of sediment cores from the DeSoto Canyon, Gulf of Mexico: Evidence for petroleum traces from the Deepwater Horizon blowout

Student: Nicola Zenzola

Thesis Committee: David Hastings, David Hollander, Isabel Romero, Yelda Hangun-Balkir

The Deepwater Horizon Macondo (MC 252) well spilled more than 4.9 million barrels of oil in the Gulf of Mexico. The release of oil at deep depths and high pressures caused gases and oil compounds to dissolve in the water column, forming an oil plume at 1000-1200m. The main purpose of this study was to use geochemical fingerprinting methods to investigate the presence of this oil in deep Gulf of Mexico sediments. Our study aims to: 1) find evidence of petroleum from the blowout event in sediments at two stations (DHS-08 and PCB-06); 2) investigate the potential organic and inorganic sources of the sedimentary material in the cores during 2010 and 2011; and 3) investigate if the signature of the MC252 oil is observed over time in deep sediments (2010-2011). Elemental and stable carbon isotopic analyses were used to characterize the composition of organic material in the sediment core samples. Organic carbon (TOC), inorganic carbon (%CaCO3), and stable carbon isotope (δ13C) were analyzed in cores taken at three different times (December 2010, February 2011, and September 2011) on both sides of the Desoto Canyon north of the DWH blowout. Stable carbon isotopic results show events in cores collected in December 2010 from station PCB-06, and February 2011 from station DSH-08, which demonstrates evidence of petroleum. TOC and %CaCO3 show that sediments from December 2010, February and September 2011 are composed of marine derived organic material. Results show that peaks observed in TOC and δ13C are lost in a time period of ten months (December 2010 to September 2011), as a result of biodegradation.

Student Research