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Multi-year observations of fluorescence and backscatter at the Southern Ocean Time Series (SOTS) shed light on two distinct seasonal bio-optical regimes

Citation

Schallenberg, C and Harley, JW and Jansen, P and Davies, DM and Trull, TW, Multi-year observations of fluorescence and backscatter at the Southern Ocean Time Series (SOTS) shed light on two distinct seasonal bio-optical regimes, Frontiers in Marine Science, 6, (SEPT) Article 595. ISSN 2296-7745 (2019) [Refereed Article]


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Copyright Statement

Copyright 2019 Schallenberg, Harley, Jansen, Davies and Trull. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0) https://creativecommons.org/licenses/by/4.0/

DOI: doi:10.3389/fmars.2019.00595

Abstract

This work presents insights from 6 years of chlorophyll-a (Chl) fluorescence and backscatter (700 nm) data at the Southern Ocean Time Series (SOTS) moorings, located in the Subantarctic Zone (SAZ) southwest of Tasmania. Using local calibrations from available voyage data, the fluorescence and backscatter records were related to Chl and particulate organic carbon (POC), allowing us to estimate and interpret carbon:Chl ratios. Surprisingly, observed carbon:Chl ratios were higher in winter than in summer, indicating that photo-acclimation of phytoplankton to decreased light levels in the deep winter mixed layer is not the main signal. Instead, the data suggest a seasonal succession of two trophodynamic regimes at SOTS: a phytoplankton-dominated community in summer, while in winter the proportion of "non-phytoplankton" POC increases. The two regimes can also be differentiated in an optical index based on fluorescence and backscatter, indicating two distinct bio-optical populations. Seasonal iron limitation and deep winter mixing in the SAZ, reaching as deep as 600 m, likely play key roles in setting the stage for the observed ecological succession of the two trophodynamic regimes.

Item Details

Item Type:Refereed Article
Keywords:chlorophyll fluorescence, backscatter, SAZ, POC, optical index, Southern Ocean, time series, SOTS
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Biological oceanography
Objective Division:Environmental Management
Objective Group:Management of Antarctic and Southern Ocean environments
Objective Field:Biodiversity in Antarctic and Southern Ocean environments
UTAS Author:Schallenberg, C (Dr Christina Schallenberg)
UTAS Author:Harley, JW (Mr James Harley)
UTAS Author:Jansen, P (Mr Peter Jansen)
UTAS Author:Davies, DM (Ms Diana Davies)
UTAS Author:Trull, TW (Professor Thomas Trull)
ID Code:137507
Year Published:2019
Web of Science® Times Cited:5
Deposited By:Oceans and Cryosphere
Deposited On:2020-02-18
Last Modified:2020-05-22
Downloads:5 View Download Statistics

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