Continental and marine sources of organic matter and nitrogen for rías of northern Galicia (Spain)

Abstract

Sources of organic matter and nitrogen to the rías of Ortigueira, O Barqueiro and Viveiro (Galicia, N Spain) were traced using stable carbon and nitrogen isotopes. Samples of water, seston, benthic organisms and sediments were collected in summer 2007 and 2008. Instantaneous sources were inferred from the concentrations and isotopic composition of seston, while averaged sources over longer time scales (months) were inferred from stable isotopes in macrophytes (Ascophyllum nodosum and Fucus vesiculosus) and mussels (Mytilus galloprovincialis). Dissolved nitrate, nitrite and ammonium concentrations in surface water were low in the estuarine zone and generally increased towards the river and the open sea in all rías. Nitrite and ammonium values were generally low, suggesting low importance of in situ nitrification and denitrification processes. The concentrations of ammonium, chlorophyll, and heavy nitrogen isotopes in seston were higher only in the main river of Viveiro, suggesting local pollution. Isotopic signatures and high nitrogen concentrations in seston discharged from the wastewater treatment plants indicated incomplete removal of nitrogen. However, taking into account water discharge fluxes and the isotopic composition of all compartments analysed, all rías shared similar biogeochemical and trophic diversity and showed a low impact of anthropogenic sources at both short and long time scales. Dominance of marine waters, low river flow, and small urban population sizes in the watershed all contribute to the maintenance of the relatively pristine status of northern Galician rías.

Influence of mussel biological variability on pollution biomarkers

“…The intensity of the upwellings decrease from Cabo Finisterre to Santander, which is considered the limit of the Iberian upwelling (Lavín et al, 2012;Molina, 1972). The Atlantic coast has also shown several periods of upwelling in late summer or autumn (Bode et al, 1996(Bode et al, , 2011Botas et al, 1990). The Cantabrian coast also shows the upwelling phenomenon between the late spring and summer but with less intensity and duration than in the Atlantic coast (Gil, 2008;Lavín et al, 1998;Llope et al, 2003).…”

Variability in δ 15 N of intertidal brown algae along a salinity gradient: Differential impact of nitrogen sources

“…Terrestrial inputs are represented by independent river basins draining in each ria. Riverine nutrient concentrations are generally higher than oceanic waters, but the low river flows compared to the water volume exchange by tides result in a small effect of the river water in the rias (Álvarez-Salgado et al, 1996;Bode et al, 2011). Nutrient concentrations of these continental inputs may be increased by the presence of urban nuclei and anthropogenic activities, as agriculture or cattle breeding.…”

“…Fucoid species are long-lived species appropriate for detecting chronic nitrogen loadings and to obtain long-time integrative measures (Bode et al, 2011;Carballeira et al, 2013;Savage and Elmgren, 2004;Viana and Bode, 2013). As they are perennial, and they live in the intertidal area of a wide variety of environments, they are subject to a wide spatial and seasonal variability of abiotic factors and nitrogen sources.…”

Experimental assessment of the macroalgae Ascophyllum nodosum and Fucus vesiculosus for monitoring N sources at different time-scales using stable isotope composition

“…First studies with Fucaceae were focused on detecting wastewater effluents (Hobbie et al, 1990;Savage and Elmgren, 2004) but later, they were reliable used to discern anthropogenic from natural sources (Carballeira et al, 2013;García-Sanz et al, 2010Viana and Bode, 2013). Their high tolerance to broad salinity ranges have also enable to study the status of estuaries and rias in both native populations (Bode et al, 2011Raimonet et al, 2013;Viana et al, 2011) and transplant studies in the field (Deutsch and Voss, 2006).…”