Browsing by Subject "ballast water"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Characterizing Antibiotic and Heavy Metal Resistance Genes from Bacteria in Commercial Ship Ballast Water Discharged into the Duluth-Superior Harbor
    (2019-12) Sloan, Caitlin
    Ballast water discharge is a powerful vector for introducing invasive species into aquatic ecosystems and microorganisms numerically dominate the discharge. Invasive bacteria may not only alter the diversity of native bacterial communities but also transfer genetic resistance to antibiotics and heavy metals into these communities. Antibiotic and heavy metal resistance was characterized for bacteria found in ballast water collected from commercial ships actively discharging ballast water into the Duluth-Superior Harbor during 2011 and 2012. Six fosmid libraries containing metagenomic DNA were constructed from ballast water and Duluth-Superior Harbor water. These libraries were screened for antibiotic resistance to benzylpenicillin, cefotaxime, and levofloxacin and heavy metal resistance to cadmium, zinc and mercury to determine resistance by bacteria in each water sample. There were differences between the proportions of microbial fosmids showing resistance to the three antibiotics from different ballast waters than originated from within the Great Lakes. The order of increasing proportion of resistance to benzylpenicillin was: Burns Harbor, IN=Hamilton, Ont.
  • Thumbnail Image
    Item
    Defining the Risk-Release Relationship of Daphnia magna, a Non-native Aquatic Species in the Environment of Duluth-Superior Harbor
    (2015-07) TenEyck, Matthew
    Understanding how inoculation characteristics (propagule pressure) affect establishment outcome of a non-native, invading species in the context of abiotic and biotic factors (ecological resistance) is a recent area of emphasis in ecology given an urgent need to prevent and manage invasive species globally. The overarching objective of this dissertation research is to quantify how a non-native species (Daphnia magna) establishes in response to different levels of propagule pressure in the context of a Laurentian Great Lakes port receiving system. Specifically, I described spatial and temporal patterns in the density and diversity of crustacean zooplankton in the context of abiotic factors of the Duluth-Superior Harbor and St. Louis River Estuary (DSHSLRE) and used those measures to develop establishment criteria for the propagule pressure experiments. Next, I evaluated the ability of a surrogate invader, D. magna to successfully colonize 200-L mesocosm aquaria by manipulating propagule pressure and several components of ecological resistance. Special attention was paid to the density of 10 individuals m-3 as this is the current standard suggested by the International Maritime Organization for density of permissible non-native species in ballast water discharge from oceangoing vessels. Lastly, I re-analyzed the results from the propagule pressure experiments to evaluate how different establishment criteria, which vary in rigor, influence the perceived outcome. Results demonstrate notable spatial and seasonal patterns in the abiotic conditions and zooplankton diversity and density measured at nine locations sampled biweekly during 2007 and 2008 in the DSHSLRE. Abiotic characteristics of upstream sites were indicative of littoral habitats and changed more dramatically within a year and from year to year. Overall 49 distinct taxa were identified, half at the genus level Copepoda and half Cladocera. Colonization of the mesocosm aquariums by D. magna populations ranged from 50-80% in the spring and fall experiments but never achieved success greater than 33% in the summer experiments. Only when the background assemblage of zooplankton was first removed from the tanks in the summer was D. magna able to establish suggesting that ecological resistance related to resource competition was prohibitive. Risk of establishment evaluated by different threshold criteria influenced the perceived outcome of the mesocosm experiments. This study demonstrates the multi-faceted nature of drivers that determine establishment success of a non-native species and the complexities of evaluating standards on permissible biological pollution using an experimental, mesocosm venue.
  • Thumbnail Image
    Item
    Evaluation Of A Method For Ballast Water Risk-Release Assessment Using A Protist Surrogate
    (2015-08) Aliff, Meagan
    Aquatic invasive species cost the United States billions of dollars annually and are most often introduced via ships' ballast tanks. The International Maritime Organization (IMO) adopted a set of standards that sets limits on the number of viable organisms that can be discharged with ballast water. These standards require scientific research to determining the risk-release relationship (i.e. the number of propagules needed for an invasion). To examine the risk-release relationship a surrogate invader, the diatom Melosira varians, was used. Varying densities of the surrogate were added to 19-L mesocosms containing water from Duluth-Superior Harbor. Each mesocosm was sampled weekly for four weeks and the response of the phytoplankton community was measured via cell counts. Population responses varied by starting conditions but M. varians establishment was generally noted at higher inoculation densities. These findings suggest the mesocosm approach can inform the understanding of risk-release relationships.