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MERC - HYDAC Test Plan
6
Zooplankton
Exactly 1 m
3
of water from each replicate (n=5) control, and treated mesocosm will be
drained through a 35 µm (50 µm diagonal dimension) plankton net to concentrate the
zooplankton for examination under a dissecting microscope. Total concentration of organisms
will be determined using standard techniques of fixation and analysis. Zooplankton samples will
be fixed with buffered, 10% formalin in 125ml Nalgene bottles and transported to SERC for
quantification. Total counts and general taxonomic classification will be conducted under a
dissecting microscope at approximately 25X. In the case of samples containing high numbers of
zooplankton such as the unfiltered or ‘control’, this assay may involve subsampling and scaling
to report concentrations in the form of numbers per cubic-meter. Where numbers are very low,
as may be if filtering is very effective, every organism in the sample will be individually
counted. Larval forms of invertebrates will be identified to higher taxonomic levels such as
order (e.g., Decapoda) suborder (e.g., Balanomorpha) or class (e.g., Bivalvia). Adults will be
identified to species in most cases.
Phytoplankton
Finally, 500 ml of unfiltered water for each mesocosm will also be collected immediately
after filling (in an amber Nalgene bottle) to determine concentrations of phytoplankton. These
subsamples will be fixed with standard Lugol’s solution and analyzed by using a Zeiss IM
inverted microscope with (1 ml to 500 µl depending on cell density) direct counts under a
Sedgewick rafter slide.
Sample and Data Management:
We will take advantage of the established SERC ballast water sample labeling and
databases format and structure for this evaluation. Sample-labels and record keeping check-lists
will be generated using SERC protocols, and data will be stored both in existing SERC databases
(servers) and in a MERC repository for analytical data.
Data Analysis
Although multiple mesocosms, samples, and measures from each tank will be taken, to
avoid pseudo-replication, the unit of replication for statistical analyses is each trial (n = 3+). We
assume that all measures for a single trial provide one estimate of filter system efficacy. Thus,
efficacy for any parameter is estimated as changes found before and after filtration (percent
reduction). This approach controls for variation due to temporal changes in environmental
conditions.