- 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.
Ballast Water- Bilogical Analyses
- 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.