Low spring primary production and microplankton carbon biomass in Sub-Antarctic Patagonian channels and fjords (50–53°S)

Jose Luis Iriarte,Luis Antonio Cuevas,Fernanda Cornejo,Nelson Silva,Humberto E González,Leonardo Castro,Paulina Montero,Cristian A Vargas,Giovanni Daneri

doi:10.1080/15230430.2018.1525186

Abstract

ABSTRACT It is relevant to understand the processes and factors that modulate the efficiency of the carbon pump throughout the ecosystem of Patagonian fjords. Spatial variability of primary productivity and bacteria-microplankton biomass was assessed in relation to inorganic nutrients and stratification across nearshore zones of southern Patagonia (50–53°S) in austral spring 2009. Estimates of primary productivity (300–500 mg C m−2 d−1) and phytoplankton biomass (9–180 mg chlorophyll-a m−2) were low at offshore and inshore waters. Synergistic effects of low silicic acid concentrations and poor light penetration because of salinity-driven stratification of glacier meltwater in springtime appeared to negatively affect phytoplankton carbon biomass and primary production in this sub-Antarctic region. The knowledge of the relative importance of nutrient sources and light is especially significant for Patagonian glacier-fjord systems that are expected to receive higher freshwater inputs and will be more stratified in the future.

Highlights

Patagonian fjord systems are responsible for a significant portion of primary productivity (PP; Iriarte et al 2007; González et al 2010; Torres et al 2011)
Studies have pointed out that Patagonian fjords are thought to be sinks for atmospheric CO2 (Torres et al 2011), and they are important aquatic systems where high concentrations of organic matter and biogenic opal contents in the sediments have been associated with high primary productivity estimates (Aracena et al 2011; Silva and Prego 2002)
The aim of this study was to assess the spring variability in microplankton biomass and the productivity of phytoplankton along several transects of the inner sea of south Patagonia, which is influenced by freshwater inputs from coastal rivers and glaciers

Summary

Introduction

Patagonian fjord systems are responsible for a significant portion of primary productivity (PP; Iriarte et al 2007; González et al 2010; Torres et al 2011). Coupling between freshwater inputs (from rivers and glaciers), nutrients, and biological responses of coastal systems in the outflow region of Patagonia’s inner seas has been a major oceanographic issue in the past fifteen years, especially given actual scenarios of climatic-driven hydrological regime changes (León-Muñoz et al 2018). Studies have pointed out that Patagonian fjords are thought to be sinks for atmospheric CO2 (Torres et al 2011), and they are important aquatic systems where high concentrations of organic matter and biogenic opal contents in the sediments have been associated with high primary productivity estimates (Aracena et al 2011; Silva and Prego 2002).

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Conclusion