Shipboard Plankton Dilution Experiment Chlorophyll collected at the mid-Atlantic Bight Shelfbreak on R/V Neil Armstrong AR29, R/V Ronald H. Brown RB1904 and R/V Thomas G. Thompson TN368 to the New England Shelfbreak in April 2018 and and May/July 2019

Website: https://www.bco-dmo.org/dataset/961794
Data Type: experimental
Version: 1
Version Date: 2025-05-14

Project
» Collaborative Research: Shelfbreak Frontal Dynamics: Mechanisms of Upwelling, Net Community Production, and Ecological Implications (SPIROPA)
ContributorsAffiliationRole
McGillicuddy, Dennis J.Woods Hole Oceanographic Institution (WHOI)Co-Principal Investigator
Petitpas, ChristianMassachusetts Division of Marine FisheriesCo-Principal Investigator, Contact
Turner, JeffersonUniversity of Massachusetts Dartmouth (UMass Dartmouth)Co-Principal Investigator
Zhang, Weifeng GordonWoods Hole Oceanographic Institution (WHOI)Co-Principal Investigator
Soenen, KarenWoods Hole Oceanographic Institution (WHOI BCO-DMO)BCO-DMO Data Manager

Abstract
As part of the Shelfbreak Productivity Interdisciplinary Research Operation at the Pioneer Array (SPIROPA) Project, twelve grazing experiments utilizing the two-point dilution technique were conducted during each of three research cruises (April of 2018, and May and July of 2019) in the Middle Atlantic Bight to estimate microzooplankton grazing rates and net phytoplankton growth rates. Stations where the dilution experiments were conducted were strategically located in one of three key cross-shelf water mass regimes: (1) at the shelfbreak front, (2) inshore of the front in continental shelf water and (3) offshore of the front in slope water. Grazing incubations were performed on water sampled from the chlorophyll maximum, when present, and conducted on the <200 µm fraction of water (what passed through a 200 µm sieve) in order to include only the microzooplankton grazers and avoid trophic cascades associated with mesozooplankton predators and grazers. The 2 dilution points were 10% and 100% of the < 200 µm sample water. All experiments were run in triplicate for 24 hours and consisted of a dark treatment incubation and a light treatment incubation at a simulated 30% E0.


Coverage

Location: Mid-Atlantic Bight Shelf break south of New England, OOI Pioneer Array
Spatial Extent: N:40.646633 E:-70.399952 S:39.583275 W:-71.083692
Temporal Extent: 2018-04-17 - 2019-07-17

Methods & Sampling

Daily Microzooplankton Grazing 2-Point Dilution Experiments were conducted on each of three cruises as a component of the SPIROPA project. 12 experiments/Cruise, Targeting 3 water mass regimes: shelf, shelfbreak front and slope waters.

Grazing experiment sample water was collected with a CTD/Niskin bottle rosette at depths ranging from surface to 56m, targeting chl-a max if present. The two dilution treatments were 100% of <200 µm filtered water and 10% of <200 µm water. Station water filtered through a Whatman 1.2 µm glass fiber filter was used as dilution water for the 10% treatment.


Data Processing Description

Separate triplicate 1-literclear PET jars of each dilution point were concurrently incubated for 24 hrs. in two separate incubation treatments: Dark and Light (30% Eo) flow-through seawater deck incubators. After 24-hour incubations 200 ml of each treatment replicate were filtered onto the glass fiber filters and frozen for later chlorophyll processing.

Chlorophyll samples were analyzed on a Turner AU10 laboratory fluorometer according to the methodology of Parsons et al. (1984).


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Data Files

File
961794_v1_chla.csv
(Comma Separated Values (.csv), 62.54 KB)
MD5:581cd8138d34251230385d3ce4a0ddfa
Primary data file for dataset ID 961794, version 1

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Related Publications

Parsons, T. R., Maita, Y., & Lalli, C.M. (1984). A manual of chemical and biological methods for seawater analysis. Pergamon Press. doi:10.1016/c2009-0-07774-5 https://doi.org/10.1016/C2009-0-07774-5
Methods

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Parameters

ParameterDescriptionUnits
CRUISE

Cruise identifier

unitless
EXPERIMENT

One experiment was conducted per cruise day. This is the consecutive experiment number.

unitless
STATION

Alphanumeric Station identifier.

unitless
LATITUDE

North latitude

decimal degrees
LONGITUDE

West longitude as indicated by negative

decimal degrees
SAMPLE_ID

Dilution experiment sample treatment and replicate number. See sample code in data spreadsheet

unitless
WATER_MASS

Identification of water mass type (shelf, slope, front) with hydographic feature( eddy, warm core ring, streamer) descriptor when present

unitless
DEPTH_M

Sample depth where dilution experiment water was collected with Niskin bottles

meters
DATE

Date of sample collection and start of 24 hour dilution experiment based on Local Time: EDT

unitless
CHLA

Chlorophyll a concentration

µg/L
PHEO

Pheopigments concentration

µg/L
PERC_Chla

Percentage of chlorophyll a to chlorophyll a + pheopigments

%
MEAN_Chla

Arithmetic mean of chlorophyll a concentrations for triplicate sample treatments

µg/L
SD

Standard Deviation of chlorophyll a concentration for triplicate sample treatments

µg/L
SE

standard error of the mean chlorophyll a concentration for triplicate sample treatments

µg/L
NOTES

Additional notes

units
Sample_Code

Additional descriptor details for the alphanumeric code used in the Sample_ID field

unitless


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Instruments

Dataset-specific Instrument Name
Generic Instrument Name
CTD Sea-Bird SBE 911plus
Dataset-specific Description
CTD/Niskin bottle rosette equipped with a SBE 911 plus CTD system, and twenty-four 10 L Niskin bottles fitted with Teflon-coated external closures were used for water column sampling.
Generic Instrument Description
The Sea-Bird SBE 911 plus is a type of CTD instrument package for continuous measurement of conductivity, temperature and pressure. The SBE 911 plus includes the SBE 9plus Underwater Unit and the SBE 11plus Deck Unit (for real-time readout using conductive wire) for deployment from a vessel. The combination of the SBE 9 plus and SBE 11 plus is called a SBE 911 plus. The SBE 9 plus uses Sea-Bird's standard modular temperature and conductivity sensors (SBE 3 plus and SBE 4). The SBE 9 plus CTD can be configured with up to eight auxiliary sensors to measure other parameters including dissolved oxygen, pH, turbidity, fluorescence, light (PAR), light transmission, etc.). more information from Sea-Bird Electronics

Dataset-specific Instrument Name
Generic Instrument Name
Niskin bottle
Dataset-specific Description
CTD/Niskin bottle rosette equipped with a SBE 911 plus CTD system, and twenty-four 10 L Niskin bottles fitted with Teflon-coated external closures were used for water column sampling. Zooplankton were microscopically identified and counted using a Wild M5A dissecting microscope.
Generic Instrument 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.

Dataset-specific Instrument Name
Generic Instrument Name
Turner Designs Fluorometer 10-AU
Generic Instrument Description
The Turner Designs 10-AU Field Fluorometer is used to measure Chlorophyll fluorescence. The 10AU Fluorometer can be set up for continuous-flow monitoring or discrete sample analyses. A variety of compounds can be measured using application-specific optical filters available from the manufacturer. (read more from Turner Designs, turnerdesigns.com, Sunnyvale, CA, USA)


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Deployments

AR29

Website
Platform
R/V Neil Armstrong
Start Date
2018-04-16
End Date
2018-04-29

RB1904

Website
Platform
NOAA Ship Ronald H. Brown
Start Date
2019-05-12
End Date
2019-05-25

TN368

Website
Platform
R/V Thomas G. Thompson
Start Date
2019-07-05
End Date
2019-07-18
Description


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Project Information

Collaborative Research: Shelfbreak Frontal Dynamics: Mechanisms of Upwelling, Net Community Production, and Ecological Implications (SPIROPA)


Coverage: Shelf break south of New England, OOI Pioneer Array


NSF award abstract:

The continental shelf break of the Middle Atlantic Bight supports a productive and diverse ecosystem. Current paradigms suggest that this productivity is driven by several upwelling mechanisms at the shelf break front. This upwelling supplies nutrients that stimulate primary production by phytoplankton, which in turn leads to enhanced production at higher trophic levels. Although local enhancement of phytoplankton biomass has been observed in some circumstances, such a feature is curiously absent from time-averaged measurements, both from satellites and shipboard sampling. Why would there not be a mean enhancement in phytoplankton biomass as a result of the upwelling? One hypothesis is that grazing by zooplankton prevents accumulation of biomass on seasonal and longer time scales, transferring the excess production to higher trophic levels and thereby contributing to the overall productivity of the ecosystem. However, another possibility is that the net impact of these highly intermittent processes is not adequately represented in long-term means of the observations, because of the relatively low resolution of the in-water measurements and the fact that the frontal enhancement can take place below the depth observable by satellite. The deployment of the Ocean Observatories Initiative (OOI) Pioneer Array south of New England has provided a unique opportunity to test these hypotheses. The combination of moored instrumentation and autonomous underwater vehicles will facilitate observations of the frontal system with unprecedented spatial and temporal resolution. This will provide an ideal four-dimensional (space-time) context in which to conduct a detailed study of frontal dynamics and plankton communities needed to examine mechanisms controlling phytoplankton populations in this frontal system. This project will also: (1) promote teaching, training and learning via participation of graduate and undergraduate students in the research , (2) provide a broad dissemination of information by means of outreach in public forums, printed media, and a video documentary of the field work, and (3) contribute to improving societal well-being and increased economic competitiveness by providing the knowledge needed for science-based stewardship of coastal ecosystems, with particular emphasis on connecting with the fishing industry through the Commercial Fisheries Research Foundation.

The investigators will conduct a set of three cruises to obtain cross-shelf sections of physical, chemical, and biological properties within the Pioneer Array. Nutrient distributions will be assayed together with hydrography to detect the signature of frontal upwelling and associated nutrient supply. The investigators expect that enhanced nutrient supply will lead to changes in the phytoplankton assemblage, which will be quantified with conventional flow cytometry, imaging flow cytometry (Imaging FlowCytobot, IFCB), optical imaging (Video Plankton Recorder, VPR), traditional microscopic methods, and pigment analysis. Zooplankton will be measured in size classes ranging from micro- to mesozooplankton with the IFCB and VPR, respectively, and also with microscopic analysis. Biological responses to upwelling will be assessed by measuring rates of primary productivity, zooplankton grazing, and net community production. These observations will be synthesized in the context of a coupled physical-biological model to test the two hypotheses that can potentially explain prior observations: (1) grazer-mediated control and (2) undersampling. Hindcast simulations will also be used to diagnose the relative importance of the various mechanisms of upwelling. The intellectual merit of this effort stems from our interdisciplinary approach, advanced observational techniques, and integrated analysis in the context of a state-of-the-art coupled model. The project will address longstanding questions regarding hydrodynamics and productivity of an important ecosystem, leading to improved understanding of physical-biological interactions in a complex continental shelf regime. Given the importance of frontal systems in the global coastal ocean, it is expected that knowledge gained will have broad applicability beyond the specific region being studied.



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Funding

Funding SourceAward
NSF Division of Ocean Sciences (NSF OCE)

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