Biogeochemical markers across a pollution gradient in a Patagonian estuary: A multidimensional approach of fatty acids and stable isotopes

G.A Kopprio,M.S Dutto,J.E Garzón Cardona,A Gärdes,R.J Lara,M Graeve

doi:10.1016/j.marpolbul.2018.10.059

Abstract

A combined approach merging stable isotopes and fatty acids was applied to study anthropogenic pollution in the Río Negro estuary. Fatty acid markers of vegetal detritus indicated considerable allochthonous inputs at freshwater sites. Correlative evidence of diatom fatty acids, δ13C, chlorophyll and particulate organic matter suggested the importance of diatoms for the autochthonous organic matter production at the river mouth. Low δ15N values (~0‰) and high fatty acid 18:1(n-7) concentrations in the suspended particulate matter, in combination with the peaks of coliforms and ammonium, indicated a strong impact of untreated sewage discharge. The 15N depletion was related to oxygen-limited ammonification processes and incorporation of 15N depleted ammonium to microorganisms. This work demonstrates that the combined use of lipid and isotopic markers can greatly increase our understanding of biogeochemical factors and pollutants influencing estuaries, and our findings highlight the urgent need for water management actions to reduce eutrophication.

Highlights

Temperate estuaries are highly dynamic systems located in to rapidly changing environments
Correlative evidence of diatom fatty acids, δ13C, chlorophyll and particulate organic matter suggested the importance of diatoms for the autochthonous organic matter production at the river mouth
The freshwater stations were characterized by significant higher values of the bacterial marker 15:0, 16:0, the terrestrial marker 24:0, the diatom marker 16:1(n-7), the bacterial marker 18:1(n-7), the 18:1(n-9), and the terrestrial vegetation or chlorophyte markers 18:2(n-6) and 18:3(n-3)

Summary

Introduction

Temperate estuaries are highly dynamic systems located in to rapidly changing environments. These systems are subject to ever-changing hydrology due to tides, coastal storms, winds, and seasons, in conjunction with human activities that strongly influence the cycle of nutrients and the ecology of coastal communities (Biancalana et al, 2014; Fricke et al, 2016; Bermejo et al, 2018). Considerable biogeochemical research has focused on these systems, knowledge about the source, fate and transformation of the organic matter in estuaries is still limited (Bristow et al, 2013; Dubinenkov et al, 2015; Canuel and Hardison, 2016). Likely effects of global change are projected to be similar to effects of eutrophication (Jarvie et al, 2012; Kopprio et al, 2015a), with undesirable consequences including increases of microbial load and activity, algal blooms, hypoxia and nekton mortality

Objectives

Methods

Results

Discussion

Conclusion