Ballast Water 2017-11-29T09:59:37+00:00

Evaluating the Transport of Aquatic Organisms via Ship Ballast Water

The primary objective of this project is to identify and quantify the bacteria, phytoplankton, and small fauna (maximum dimension < 80 µm) in the ballast water of vessels engaged in U.S. Department of Defense (DoD) operations, with emphasis on non-indigenous and/or harmful organisms. A second objective is to evaluate relationships between the observed biological diversity/abundance, environmental conditions, and ballast water management activities aboard theses ships. The project’s multi-disciplinary team of investigators includes Drs. JoAnn Burkholder and Howard Glasgow of the North Carolina State University Center for Applied Aquatic Ecology, Dr. Gustav Hallegraeff of the University of Tasmania, Dr. Andrew Cohen of the San Francisco Bay Estuary Institute, Dr. David Oldach of the Institute of Human Virology within the University of Maryland’s School of Medicine, and Dr. Michael Mallin of the University of North Carolina at Wilmington. Funding is provided by the Strategic Environmental Research and Development Program (SERDP).

The Ballast Water Problem

The discovery that marine species could be translocated in the ballast water of modern steel ships was first reported by Ostenfeld (1908). Large vessels take on and discharge ballast water primarily to adjust buoyancy and trim in response to changes in load and sea conditions. Ballast water is usually carried in dedicated ballast tanks, and sometimes in empty cargo holds. This essential vessel operation can result in the transport of large volumes of water from one coastal region to another, along with the resident organisms (Figure 1). The long-distance dispersal of marine microbes, plants and animals in ship ballast water is a potential environmental problem because, although the oceans are continuous, coastal marine life is geographically discontinuous. Many cases of exotic or non-indigenous species introductions have been documented, resulting in ecological and economic repercussions (e.g. Cohen 1998).

Project Research Activities

Thirty vessels on the U.S. Pacific and Atlantic Coasts are targeted for assessment in this project. The sampling pool is comprised of oilers (Fig 2a) and cargo vessels operated by or for the Military Sealift Command. Water quality measurements are made within the ballast tanks using a sensor bundle (Fig 2b). Concentrated biological samples are collected with 20-µm plankton nets (Fig 2c), while whole-water samples are collected with a controlled-fill, air displacement sampling canister (Fig 2d).

Biological Analyses

Bacteria – Bacteria abundance in the ballast tanks is being quantified by flow cytometry (Figure 4). Coupled with fluorometric detection and assuming reasonable distinction of particle attributes, this instrument rapidly produces particle distributions that allow differentiation and enumeration of populations within a given sample. For example based on size and chlorophyll autofluorescence, populations of bacteria and pico-eukaryotes can be distinguished from each other and from larger cells within a sample, thereby facilitating rapid enumeration of each group. Fluorometric stains that bind with nucleic acids, enzymes or other cellular constituents can also help differente biotic particles and indicate cellular viability in unpreserved samples. Molecular techniques are being used to screen for a suite of harmful bacteria: PCR is run to produce bacterial amplicon products; the bacterial amplicons have each been linked to a vector; and we are producing E. coli cell lines capable of incorporating the vector DNA product from each. Based on the data from these cell lines, we search nucleotide databases for a sequence match, and if it is not available, we determine the phylogeny. From the sequence data and species-specific PCR assays, we are identifying pathogens of interest.

Phytoplankton – Chlorophyll a concentrations are measured in the ballast tanks as an indicator of total phytoplankton biomass. Phytoplankton taxa analyses are conducted using phase contrast light microscopy (200-600X) (Figure 5), and Utermohl chambers for quantification. Scanning electron microscopy and molecular screens are also utilized as needed to aid in identifications.

Zooplankton – Small zooplankton (maximum dimension < 80 µm) are being identified and quantified using light microscopy. In addition to the microscopic analyses of preserved samples, live samples are collected for culture in media designed to simulate discharge into a receiving system where environmental conditions might permit establishment. The cultures are being used to assist in identification of some taxa. In addition, some of the cultured species are being tested in heat treatment experiments to assess temperature regimes that kill harmful organisms capable of surviving transport (Figure 6). Heat treatment has been considered as an effective way to treat ballast water in some ships, depending on the ship design.

Database Developments and Vessel Tracking

We are developing a comprehensive relational database that is designed to incorporate the extensive chemical and biological data from this project, as well as the relevant vessel and ballast management data being generated. This application is a powerful tool, facilitating rapid assessment of potential risk factors for species introductions. The design process is complete and the system is currently under construction using Microsoft Access as a front-end (Figure 7). Another useful feature will be the automated linkage we are creating between the database application and ARCVIEW 8.0, a GIS mapping program. This will take the information entered into the ballast management data module of the database, such as ballasting activity and the associated coordinates, and will enable automated mapping of specific voyages. Users will be able to rapidly map a biological variable (e.g. a species) of interest, following its voyage-specific ballasting history. This functionality, coupled with the query functions of the database for the biological and chemical data, will allow for any number of mapping scenarios and on multiple scales designed to help characterize risk of species introductions. In addition, we plan to incorporate web linkages from various remote-sensing resources, to allow consideration of other factors that may be relevant to organism occurrence and density in risk assessment. For example, voyage mapping coupled with the chemical and biological observations from this study, taken with NOAA sea surface temperature animations, may demonstrate that a given locale, at a given time of year represents a high risk for uptake of water that may be diverse and/or abundant (Figure 8).