Study on the suspended particulate matter of a Mediterranean artificial lake (Sos Canales Lake) using Stable Isotope Analysis of carbon and nitrogen

¹ Dipartimento di Scienze della Natura e del Territorio, University of Sassari, via Piandanna 4, Sassari, Italy
² CNR Institute of Ecosystem Study (CNR-ISE), Largo Tonolli 50, Verbania, Italy
³ IASMA Fondazione Edmund Mach, San Michele all'Adige, TN, Italy
⁴ Ente Acque della Sardegna, via Mameli 88, Cagliari, Italy

^* Corresponding author: amedeofadda@gmail.com

Received: 30 July 2016
Accepted: 4 November 2016

Abstract

Stable isotope analysis of carbon (C) and nitrogen (N) was used to study the nature and origin of the suspended particulate matter (SPM) in a small Mediterranean reservoir, Lake Sos Canales (SC). The δ¹³C and δ¹⁵N isotopic ratios, physical-chemical parameters, nutrients and phytoplankton were analyzed ca. monthly over a hydrological year on the vertical profile at two stations (lacustrine and riverine). SPM quantity and composition were related to the hydrological annual dynamic. In Mediterranean reservoirs, water-level fluctuation is one of the most important stressors, largely dependent on the strong seasonality of climate and water exploitation for human uses. Mediterranean reservoirs show different phases during a hydrological year, alternating empty and low water level (summer–autumn), re-filling (winter–spring) and high water (spring–summer) phases. Isotopic ratios of C and N were similar on the vertical profile and at the two stations during the low water phase, but differed during the re-filling and high water phases. Significant correlations were found between δ¹⁵N and water level, and between δ¹³C and temperature in the surface layer at the lacustrine station. An unusual δ¹³C distribution along the water column during the re-filling phase was interpreted on the basis of phytoplankton species composition, mainly due by Gymnodinium uberrimum.