Dataset: ALFA data - EKAMSAT

Name: Advanced Laser Fluorescence Analyzer (ALFA) data from the western Arabian Sea acquired on the R/V Roger Ravelle in June 2023
Published: 2024-11-01
Keywords: phytoplankton, Indian Ocean, Indian Ocean Dipole, Warm Pool, Indian monsoon, oceans

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Spatial Extent: N:12.535988 E:136.543725 S:-17.186432 W:66.406712

Western Arabian Sea

Temporal Extent: 2022-01-26 - 2023-06-21

Project:

Collaborative Research: Mesoscale variability in nitrogen sources and food-web dynamics supporting larval southern bluefin tuna in the eastern Indian Ocean (BLOOFINZ-IO)

RAPID - Assessing the response of the Seychelles-Chagos Thermocline Ridge ecosystem to an Indian Ocean Dipole event (SCTR_IOD)

Program:

Second International Indian Ocean Expedition (IIOE-2)

Co-Principal Investigator:

Joaquim Goes (Lamont-Doherty Earth Observatory, LDEO)

Helga do Rosario Gomes (Lamont-Doherty Earth Observatory, LDEO)

Contact:

Helga do Rosario Gomes (Lamont-Doherty Earth Observatory, LDEO)

BCO-DMO Data Manager:

Karen Soenen (Woods Hole Oceanographic Institution, WHOI BCO-DMO)

Version:

Version Date:

2024-11-01

Restricted:

Validated:

Current State:

Data not available

Advanced Laser Fluorescence Analyzer (ALFA) data from the western Arabian Sea acquired on the R/V Roger Ravelle in June 2023

Abstract:

We participated in the Indo-US EKAMSAT-PILOT cruise undertaken in the western Arabian Sea in May - June 2023. EKAMSAT is a collaborative Indo-US field campaign funded by the Ministry of Earth Sciences, Govt. of India and the Office of Naval Research, focused on the acquisition of contemporary oceanographic and atmospheric datasets deemed critical for improving the predictive skills of operational monsoon models. During the pre-monsoon season, akin to the warm pool that forms in the Western Equatorial Indian Ocean, there is a warm pool that forms in the Eastern Arabian Sea situated roughly west of the coast of Kerala. Our overarching objectives were two fold: 1) to understand whether phytoplankton communities of the warm pool were significantly different from those within the warm pool and from the surrounding waters and 2) whether there is a fundamental shift in phytoplankton functional types and their biomass following the onset of the summer monsoon. During the cruise our study area came under the influence of cyclone Biparjoy which led to a fundamental shift in phytoplankton functional types and biomass.

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Description

BLOOFINZ cruise (RR2201) was supported by the "Collaborative Research: Mesoscale variability in nitrogen sources and food-web dynamics supporting larval southern bluefin tuna in the eastern Indian Ocean" project.

EksamSat cruise (RR2306) was supported by the "RAPID - Assessing the response of the Seychelles-Chagos Thermocline Ridge ecosystem to an Indian Ocean Dipole event" project.

Methods & Sampling

Underway fluoresence sampling from the western Arabian Sea acquired on the R/V Roger Ravelle in June 2023 (EksamSat cruise) and the Eastern Indian Ocean Upwelling region on the R/V Roger Ravelle in January 2022 (BLOOFINZ).

When the instrument is used for underway sampling, the ALF is connected to the ship’s uncontaminated seawater flow-through system allowing for continuous measurements in water drawn from approximately 5m below the surface

The Automatic Laser Fluorometric Analyzer (ALFA) is a state-of-the-art instrument, that combines high-resolution spectral measurements of blue (405 nm) and green (532 nm) laser-stimulated fluorescence, with spectral deconvolution techniques to estimate CDOM, phytoplankton variable fluorescence (Fv/Fm), Chl a and three types of phycobiliprotein pigments.

Data Processing Description

The fluorescence intensities attributable to each of the variables are normalized to the water Raman and expressed as relative fluorescence units (RFU). The Raman–normalized Chl a (679nm) and CDOM (508nm) fluorescence signals stimulated by the blue laser allow for measurements of Chl a and CDOM, respectively, while the Raman-normalized PE fluorescence signatures stimulated with the green laser allow for detection and quantitative assessment of three PE-containing groups of phytoplankton. These include the:
1) PE-1 peak at 565nm from blue water oligotrophic cyanobacteria with high phycourobilin/phycoerythrobilin (PUB/PEB) ratios,
2) PE-2 peak at 578nm from green water cyanobacteria with low-PUB/PEB ratios that usually thrive in coastal mesohaline waters, and
3) PE-3 peak at 590 nm attributable to eukaryotic photoautotrophic cryptophytes that are rich in phycobiliproteins and often abundant in coastal, and estuarine environments and in enclosed bays (Chekalyuk and Hafez, 2008; Chekalyuk et al., 2012, Goes et al. 2014).

More Information about this dataset

Funding Sources

Funding Source	Award Number
NSF Division of Ocean Sciences	OCE-2019983

Deployments

Deployment	Synonyms	Start Date	Platform	Investigator
RR2201	BLOOFINZ-IO	2022-01-20	R/V Roger Revelle	Michael R. Landry (Chief Scientist)	data info
RR2306		2023-06-08	R/V Roger Revelle	Craig M. Lee (Chief Scientist)	data info

Instruments

Wet Labs Aquatic Laser Fluorescence Analyzer (ALFA)

Supplied Name: Automatic Laser Fluorometric Analyzer (ALFA)

Supplied Description:

Instrument Type

Generic Name: Wet Labs Aquatic Laser Fluorescence Analyzer (ALFA)

Acronym: ALFA

Generic Description:

WET Labs’ Aquatic Laser Fluorescence Analyzer (ALFA) provides spectrally and
temporally resolved measurements of key bio-environmental variables in oceanic,
coastal, and fresh waters. Operation modes allow underway shipboard measurements
and discrete sample analysis for accurate assessments of pigment biomass,
phytoplankton community structure and physiology.

Features
• Spectral deconvolution of overlapped fluorescence bands with Raman normalization
• Improved assessment of chlorophyll concentrations for estimating phytoplankton biomass
• Discrimination of 5 phycobiliprotein pigments for structural phytoplankton characterization
• Fluorescence assessment of chromophoric dissolved organic matter (CDOM)
• Measures variable fluorescence, Fv/Fm, with correction for background CDOM fluorescence
• Instrument software allows real-time data analysis and display with GPS coordinates and time

more information from Wet Labs

Parameters

Date and time formats are described in python strftime() syntax.

Supplied Name	Supplied description	Supplied Units	Standard Name
cruise_ID	Cruise identifier: BLOONZ_2022 or EXAMSAT-1	unitless	cruise_id
Date	Sampling date in ISO format Format: %Y-%m-%d	unitless	date
TIME_UTC	Sampling time in ISO format (UTc timezone) Format: %H:%M:%S	unitless	time
ISO_DateTime_UTC	Sampling datetime in ISO format (UTC timezone) Format: %Y-%m-%dT%H:%M:%SZ	unitless	ISO_DateTime_UTC
Latitude	Latitude of sampling location, south is negative	decimal degrees	lat
Longitude	Longitude of sampling location, west is negative	decimal degrees	lon
CDOM	Chromophoric Dissolved Organic Matter	rfu	CDOM
Chl_a	Chlorophyll a	mg m-3	chl_a
Fv_Fm	Phytoplankton Quantum efficiency	unitless	quantum yield
PE_1	PE-1 peak at 565nm from blue water oligotrophic cyanobacteria with high phycourobilin/phycoerythrobilin (PUB/PEB) ratios	rfu	wave_stats
PE_2	PE-2 peak at 578nm from green water cyanobacteria with low-PUB/PEB ratios that usually thrive in coastal mesohaline waters	rfu	wave_stats
PE_3	PE-3 peak at 590 nm attributable to eukaryotic photoautotrophic cryptophytes that are rich in phycobiliproteins and often abundant in coastal and estuarine environments and in enclosed bays	rfu	wave_stats

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Dataset: ALFA data - EKAMSAT