Dataset: phyto_growth
Deployment: HX242

Phytoplankton growth rates and microzoo grazing

Principal Investigator:

Suzanne Strom (Western Washington University, WWU)

Data Manager:

Hal Batchelder (Oregon State University, OSU-CEOAS)

BCO-DMO Data Manager:

Ms Dicky Allison (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Nancy Copley (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Shannon Rauch (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Project:

U.S. GLOBEC Northeast Pacific (NEP)

Data URL:

https://osprey.bco-dmo.org/dataset-deployment/450258/data

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Description

Phytoplankton Growth Rates in the coastal Gulf of Alaska

Phytoplankton growth rates, the phytoplankton growth rate response to nutrient enrichment, and microzooplankton grazing rates on phytoplankton in three different size classes were measured during three cruises to the coastal Gulf of Alaska in 2001.

Methods & Sampling

Dataset acquisition description

[excerpted from Strom, et al. (2006) Microzooplankton grazing in the coastal Gulf of Alaska: Variations in top-down control of phytoplankton. Limnol Oceanogr in press.]

Water drawn from multiple Niskin bottles closed at a single depth was pooled into two 25-liter polycarbonate carboys. Most often, water was collected from the depth corresponding to 50% of surface irradiance (50% Io, 3 to 10 m). Once during April, and once per station during July, water was collected from the depth of the subsurface chlorophyll maximum (SCM, 12 to 25 m). The contents of one carboy were gravity-filtered (0.2 um) to generate particle-free filtered seawater (FSW, the diluent for the dilution series). The contents of the other were gently pre-screened through 200 um Nitex mesh to exclude macrozooplankton (WSW, the whole seawater for the dilution series). Using gentle siphoning and mixing techniques, FSW and WSW were combined in known proportions in 2.35-liter polycarbonate bottles to generate a dilution series consisting of 9, 16, 24, 41, 61, and 100% WSW (each in duplicate). An additional pair of bottles diluted to 4% was added during the May and July cruises, as well as an additional pair of 100% WSW bottles to control for the effects of nutrient enrichment on phytoplankton growth rate. Clean techniques and inert materials (silicone, polycarbonate) were used throughout.

Deployment-specific acquisition description

[excerpted from Strom, et al. (2006) Microzooplankton grazing in the coastal Gulf of Alaska: Variations in top-down control of phytoplankton. Limnol Oceanogr in press.]

Water drawn from multiple Niskin bottles closed at a single depth was pooled into two 25-liter polycarbonate carboys. Most often, water was collected from the depth corresponding to 50% of surface irradiance (50% Io, 3 to 10 m). Once during April, and once per station during July, water was collected from the depth of the subsurface chlorophyll maximum (SCM, 12 to 25 m). The contents of one carboy were gravity-filtered (0.2 µm) to generate particle-free filtered seawater (FSW, the diluent for the dilution series). The contents of the other were gently pre-screened through 200 µm Nitex mesh to exclude macrozooplankton (WSW, the whole seawater for the dilution series). Using gentle siphoning and mixing techniques, FSW and WSW were combined in known proportions in 2.35-liter polycarbonate bottles to generate a dilution series consisting of 9, 16, 24, 41, 61, and 100% WSW (each in duplicate). An additional pair of bottles diluted to 4% was added during the May and July cruises, as well as an additional pair of 100% WSW bottles to control for the effects of nutrient enrichment on phytoplankton growth rate. Clean techniques and inert materials (silicone, polycarbonate) were used throughout.

Data Processing Description

Dataset Processing Description

Initial samples for size-fractionated chlorophyll (<5, 5 to 20, and >20 um, in quadruplicate), nutrients (nitrate, nitrite, silicic acid, phosphate), and microzooplankton abundance and composition (in duplicate, see below) were taken from the WSW carboy at intervals during experiment set-up. Initial chlorophyll levels in diluted bottles were calculated from these measured WSW values and known dilution factors. Coefficients of variation for quadruplicate initial chlorophyll samples averaged 7.9%, 13.5%, and 8.9% for the <5, 5 to 20, and >20 um size fractions, respectively. During May (all but outer shelf experiments) and July cruises, all diluted bottles and two 100% WSW bottles were enriched with nitrate (4.7 umol L-1 as NaNO3) and phosphate (0.27 umol L-1 as Na2HPO4). The other two 100% WSW bottles were left unenriched. Bottles were screened to collection-depth light levels with neutral density screening and incubated on deck in seawater-cooled incubators for 24 hr. All bottles were then sampled in duplicate for size-fractionated chlorophyll (filtration volumes ranged from 0.15 to 1.08 liter depending on WSW chlorophyll and dilution levels); 100% WSW bottles were additionally sampled for microzooplankton abundance and composition.

Net growth rates (k, d-1) for total chlorophyll and individual chlorophyll size fractions were calculated as (1/t)(ln[Pt/Po]), where Pt = final chlorophyll concentration, Po = initial chlorophyll concentration, and t = incubation time in d. Intrinsic growth rates (µ,d-1) of phytoplankton were estimated from the y-intercept of net growth rates regressed upon fraction WSW. For experiments exhibiting saturated grazing (i.e. a leveling of net growth rate across the least-dilute bottles) (Gallegos 1989), instrinsic growth rate estimates were based on regression of net growth rates in only the most dilute bottles (generally those with <40% WSW). Microzooplankton grazing rates (g, d-1) were estimated from the slope of the regression for experiments with linear relationships between net growth and fraction WSW, and as g = µ_n - k_n (where k_n = net growth rate of phytoplankton in enriched, 100% WSW bottles) for experiments with saturated grazing. In experiments with nutrient enrichment, unenriched phytoplankton growth rates (µ_o) were calculated as µ_o = k_o + g, where k_o = net growth rate of phytoplankton in unenriched, 100% WSW bottles. Estimates of µ_o were used to compare microzooplankton grazing to phytoplankton growth in situ (g : µ_o). These ratios represent the fraction of primary production consumed each day by microzooplankton grazing. Ratios were arctan transformed for estimation of means and standard deviations.

More detailed methods reference in Strom, et al. (2006).

Deployment-specific processing description

Initial samples for size-fractionated chlorophyll (<5, 5 to 20, and >20 µm, in
quadruplicate), nutrients (nitrate, nitrite, silicic acid, phosphate), and microzooplankton
abundance and composition (in duplicate, see below) were taken from the WSW carboy
at intervals during experiment set-up. Initial chlorophyll levels in diluted bottles were
calculated from these measured WSW values and known dilution factors. Coefficients of
variation for quadruplicate initial chlorophyll samples averaged 7.9%, 13.5%, and 8.9%
for the <5, 5 to 20, and >20 µm size fractions, respectively. During May (all but outer
shelf experiments) and July cruises, all diluted bottles and two 100% WSW bottles were
enriched with nitrate (4.7 µmol L-1 as NaNO3) and phosphate (0.27 µmol L-1 as
Na2HPO4). The other two 100% WSW bottles were left unenriched. Bottles were
screened to collection-depth light levels with neutral density screening and incubated on
deck in seawater-cooled incubators for 24 hr. All bottles were then sampled in duplicate
for size-fractionated chlorophyll (filtration volumes ranged from 0.15 to 1.08 liter
depending on WSW chlorophyll and dilution levels); 100% WSW bottles were
additionally sampled for microzooplankton abundance and composition.

Net growth rates (k, d-1) for total chlorophyll and individual chlorophyll size
fractions were calculated as (1/t)(ln[Pt/Po]), where Pt = final chlorophyll concentration,
Po = initial chlorophyll concentration, and t = incubation time in d. Intrinsic growth rates
(µ,d-1) of phytoplankton were estimated from the y-intercept of net growth rates
regressed upon fraction WSW. For experiments exhibiting saturated grazing (i.e. a
leveling of net growth rate across the least-dilute bottles) (Gallegos 1989), instrinsic
growth rate estimates were based on regression of net growth rates in only the most dilute
bottles (generally those with ?40% WSW). Microzooplankton grazing rates
(g, d-1) were
estimated from the slope of the regression for experiments with linear
relationships
between net growth and fraction WSW, and as g = µn - kn
(where kn = net growth rate of
phytoplankton in enriched, 100% WSW bottles) for experiments with saturated
grazing.
In experiments with nutrient enrichment, unenriched phytoplankton growth rates
(µo)
were calculated as µo = ko + g, where ko = net
growth rate of phytoplankton in
unenriched, 100% WSW bottles. Estimates of µo were used to compare
microzooplankton grazing to phytoplankton growth in situ (g : µo).
These ratios
represent the fraction of primary production consumed each day by
microzooplankton
grazing. Ratios were arctan transformed for estimation of means and standard
deviations.

More detailed methods reference: 
Strom, et al. (2006) Cross-shelf gradients in phytoplankton community structure, nutrient
utilization, and growth rate in the coastal Gulf of Alaska. Marine Ecology
Progress Series (in press)

More information about this dataset deployment

Funding

Award Number	Funding Source
OCE-0101397	NSF Division of Ocean Sciences
unknown NEP NOAA	National Oceanic and Atmospheric Administration

Instruments

Niskin bottle

Supplied Name: Niskin Bottle

Supplied Description:

Niskin bottle cast, use Bottle_Niskin

Instrument Type

Generic Name: Niskin bottle

Community Identifier: http://vocab.nerc.ac.uk/collection/L22/current/TOOL0412/

Generic Description:

A Niskin bottle (a next generation water sampler based on the Nansen bottle) is a cylindrical, non-metallic water collection device with stoppers at both ends. The bottles can be attached individually on a hydrowire or deployed in 12, 24, or 36 bottle Rosette systems mounted on a frame and combined with a CTD. Niskin bottles are used to collect discrete water samples for a range of measurements including pigments, nutrients, plankton, etc.

Parameters

Supplied Name	Supplied description	Supplied Units	Standard Name
cruiseid	Cruise ID.	text	cruiseid
expt	Experiment number.	dimensionless	no_bcodmo_term
date_local	Day-month-year.	dd-mon-yy	date_local
station_std	standard station number	dimensionless	station_std
lat	Latitude	decimal degrees (North is positive)	lat
lon	Longitude	decimal degrees (East is positive)	lon
time_start_local	experiment start time	24-hour clock	time_start_local
depth	water collection depth	meters	depth
chla_start_gt20um	initial chlorophyll concentration for dilutions experiments	micrograms/liter	no_bcodmo_term
chla_start_5_to_20um	initial chlorophyll concentration for dilutions experiments	micrograms/liter	no_bcodmo_term
chla_start_lt5um	initial chlorophyll concentration for dilutions experiments	micrograms/liter	no_bcodmo_term
chla_start_total	sum of three size fractions	micrograms/liter	no_bcodmo_term
fed_phyto_growth_gt20um	enriched (addition of nitrate and phosphate) phytoplankton growth rate	per day	no_bcodmo_term
fed_phyto_growth_5_to_20um	enriched (addition of nitrate and phosphate) phytoplankton growth rate	per day	no_bcodmo_term
fed_phyto_growth_lt5um	enriched (addition of nitrate and phosphate) phytoplankton growth rate	per day	no_bcodmo_term
fed_phyto_growth_total	sum of three size fractions	per day	no_bcodmo_term
fed_phyto_growth_std_err_gt20um	enriched phytoplankton growth rate standard error	per day	no_bcodmo_term
fed_phyto_growth_std_err_5_to_20um	enriched phytoplankton growth rate standard error	per day	no_bcodmo_term
fed_phyto_growth_std_err_lt5um	enriched phytoplankton growth rate standard error	per day	no_bcodmo_term
fed_phyto_growth_std_err_total	total standard error	per day	no_bcodmo_term
unfed_phyto_growth_gt20um	unenriched phytoplankton growth rate	per day	no_bcodmo_term
unfed_phyto_growth_5_to_20um	unenriched phytoplankton growth rate	per day	no_bcodmo_term
unfed_phyto_growth_lt5um	unenriched phytoplankton growth rate	per day	no_bcodmo_term
unfed_phyto_growth_total	sum of three size fractions	per day	no_bcodmo_term
unfed_phyto_growth_std_err_gt20um	unenriched phytoplankton growth rate standard error	per day	no_bcodmo_term
unfed_phyto_growth_std_err_5_to_20um	unenriched phytoplankton growth rate standard error	per day	no_bcodmo_term
unfed_phyto_growth_std_err_lt5um	unenriched phytoplankton growth rate standard error	per day	no_bcodmo_term
unfed_phyto_growth_std_err_total	total standard error	per day	no_bcodmo_term
microzoo_graz_gt20um	microzooplankton grazing rate for >20µ size fraction	per day	no_bcodmo_term
microzoo_graz_5_to_20um	microzooplankton grazing rate for >5 and <20µ size fraction	per day	no_bcodmo_term
microzoo_graz_lt5um	microzooplankton grazing rate for <5µ size fraction	per day	no_bcodmo_term
microzoo_graz_total	total microzooplankton grazing rate for all size fractions	per day	no_bcodmo_term
microzoo_graz_std_err_gt20um	standard error	per day	no_bcodmo_term
microzoo_graz_std_err_5_to_20um	standard error	per day	no_bcodmo_term
microzoo_graz_std_err_lt5um	standard error	per day	no_bcodmo_term
microzoo_graz_std_err_total	total standard error	per day	no_bcodmo_term
temp	temperature at sample depth	degrees Celsius	temp
sal	dalinity at sample depth	Practical Salinity Units (PSU)	sal
irradiance_mol_per_m2	irradiance at sample depth	mol photons/meter^2(per second?)	irradiance

Database

Contribute Data

Dataset: phyto_growth
Deployment: HX242

Dataset acquisition description

Deployment-specific acquisition description

Dataset Processing Description

Deployment-specific processing description

Database

Contribute Data

Dataset: phyto_growthDeployment: HX242

Dataset acquisition description

Deployment-specific acquisition description

Dataset Processing Description

Deployment-specific processing description

Dataset: phyto_growth
Deployment: HX242