These methods, instrumentation and/or protocols apply to all data in this dataset:| Methods and protocols used in the collection of this data package |
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Field Methods
Phytoplankton samples are collected with a submersible pump or a Van Dorn sampler from a water depth of one meter (approximately three feet) below the water surface.
Samples are stored in 60-milliliter glass bottles. Two mL of Lugol's solution are added to each sample as a stain and preservative. All samples are kept at room temperature and away from direct sunlight until analyzed.
Phycoplankton data is collected electronically via the bbe PhycoProbe instrument. The instrument conducts in vivo analysis of chlorophyll-a in microalgae and cyanobacteria and creates profiles for each algal class via fluorescence signals. The data is post-processed to average the data in 10 second intervals and add coordinate metadata. The corresponding water quality data is gathered by a YSI EXO multiparameter sonde.
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Laboratory Methods: EcoAnalysts, Inc.
Phytoplankton are identified to the lowest taxonomic level possible using the Utermöhl method and APHA standard methods (Utermöhl 1958, APHA 2012). An aliquot is allowed to settle onto a counting chamber for a minimum of 12 hours. The aliquot volume is adjusted according to the algal population density and turbidity of the sample. For the Estuary, the aliquot volume is usually about 10 ml. Aliquots are enumerated at a magnification of 630X using a Leica DMIL inverted microscope. For each settled aliquot, phytoplankton in randomly chosen transects are counted and photos are taken of the specimen, first encounter; measurements are made with an ocular micrometer. Taxa are enumerated as they appear along the transects. A minimum of 400 total algal units are counted, and a minimum of 100 algal units of the dominant taxon. For taxa that are in filaments or colonies, the number of cells per filament or colony is recorded. Length measurements are performed on 10 to 25 algal units of the dominant taxon, and up to 5 units of each minor taxon. The measurements taken are 1st greatest axial length, 2nd greatest axial length, and 3rd greatest axial length. From these measurements, biovolume is calculated for each cell measured. Biovolume equations are considered proprietary by the contractor but are based on the equations found in Hillebrand et. al. 1999. EcoAnalysts, Inc. processed data from 2008 to 2013, except for September 2013 and November 2013, which were contracted out to BSA Environmental, Inc.
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Laboratory Methods: BSA Environmental, Inc.
Phytoplankton are identified to the lowest taxonomic level possible using the Utermöhl method and APHA standard methods (Utermöhl 1958, APHA 2012). An aliquot is allowed to settle onto a counting chamber for a minimum of 12 hours. The aliquot volume is adjusted according to the algal population density and turbidity of the sample. For the Estuary, the aliquot volume is usually about 10 ml. Aliquots are enumerated at a magnification of 1200X using a Leica DMIL inverted microscope. For each settled aliquot, phytoplankton in randomly chosen transects are counted and photos are taken of the specimen, first encounter; measurements are made with an ocular micrometer. Taxa are enumerated as they appear along the transects. A minimum of 400 total algal units are counted, and a minimum of 100 algal units of the dominant taxon. For taxa that are in filaments or colonies, the total number of cells counted is recorded. Length measurements are performed on 10 algal units of the dominant taxon, and up to 5 units of each minor taxon. The measurements taken are 1st greatest axial length, 2nd greatest axial length, and 3rd greatest axial length. From these measurements, biovolume is calculated for each cell measured. Biovolume equations are considered proprietary by the contractor but are based on the equations found in Hillebrand et. al. 1999. BSA Environmental, Inc. processed samples from September 2013, November 2013, and from 2014 to present.
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Natural Unit Density Calculations (Organisms per mL)
Both contractors calculate natural unit density per unit volume of water using the same equation. Organism counts for each sample can be converted to organisms/ml using the following formula:
Organisms/ml = (C x Ac) / (V x Af x F)
where:
C = count obtained
Ac = Area of cell bottom (mm2)
Af = Area of each grid field (mm2)
F = Number of fields examined
V = volume settled, in ml
This simplifies to:
Organisms/ml = C / cV
where:
C = count obtained
cV = counted volume, in ml (cV = Ac /(V x Af x F))
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