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Each system validation trial was considered separately for statistical analysis because of
the changes in taxa and densities of organisms in ambient water masses (i.e., initial intake ballast
water) found from day to day in the Port of Baltimore. Furthermore, given that holding times
were approximately 1 hour (i.e., time between fill samples and discharge samples) and the
percent of dead organisms found were extremely low (see below), simple one-way ANOVAs
were performed for total zooplankton and for total phytoplankton, for each of the three trials.
Zooplankton were examined live under a Wild-M8 binocular microscope in order to
determine percentage of dead, or live, but clearly damaged organisms, within 2 hours of sample
collection and while still on the
Cape Washington
. Samples were split quantitatively for this
analysis, since initial concentrations (approximately 70,000/m
3
) were too high to consider
examining every specimen. Sample splits held approximately 450 organisms each. Thus,
percent-dead estimates derived from studying approximately 450 representative organisms per
sample. After samples were fixed and brought to our lab, they were examined again under a
Miejji binocular microscope to better estimate total abundance of organisms and community
composition. The percent dead was then calculated as: (dead-concentration from live-analysis /
total concentration from fixed analysis) x 100.
Phytoplankton samples were also obtained and quantified during each of three system
validation trials, in much the same way as during a normal treatment test trial. Fifteen samples
were collected during each trial with 3 replicate samples taken from each sampling port (as
described above). From each whole water sample, 250 ml subsamples were collected and
preserved with Lugol’s solution to determine total cell abundances. The phytoplankton sample
analysis was conducted using a Zeiss IM inverted microscope with (1 ml to 500 µl depending on
cell density) direct counts under a Sedgewick rafter slide.
4. MERC Test Facility Validation Results
Essentially all zooplankton, including C-dis and T-dis, were alive and active. The
numbers of dead zooplankton never exceeded 1% of the total, and was typically below 0.5%,
across all treatments and time-points (Figure 2).
There were also no significant differences in abundance of zooplankton between C and T
lines during filling (May 12 p = 0.17, May 13 p = 0.19, and May 14 p = 0.98) or during
discharge (May 12 p = 0.052, May 13 p = 0.20, and May 14 p = 0.34) for any of the three trials.
In fact, when all samples (Y-fill, C-fill, T-fill, C-dis, and T-dis) were considered together for
individual trials, no significant differences were found for trials two and three (May 13 p = 0.36,
and May 14 p = 0.99). Therefore, zooplankton are well mixed and uniformly distributed
throughout the test facility control and treated lines and tanks, and losses of zooplankton as they
pass through the facility are minimal. In trial one (May 12), it appeared that rotifers, comprising
about 35% of community abundance in the fill, decreased moderately upon discharge. However,
this decline in rotifer abundance was consistent regardless of ballast tanks where they were held,