Temporal nutrient dynamics in the Mediterranean Sea in response to anthropogenic inputs

Abstract

The temporal dynamics of the concentrations of nitrate (N), phosphate (P), and the N:P ratio in the upper water column (200–600 m) of the Mediterranean (MED) Sea were investigated using observational data (~123,100 data points) collected between 1985 and 2014. The studied variables were found to evolve similarly in the western and eastern MED Sea. In both basins, the N concentration increased during the first part of the observational period (1985–1998), and the temporal trend of N was broadly consistent with the history of riverine and atmospheric nitrogen input from populated areas in Europe, with a lag period of 20 years. In subsequent years, the N concentration was high and relatively constant between 1998 and 2005, after which N decreased gradually, although the decreasing trend was indistinct in the western basin. In particular, the trend of constant then declining N after 1998 is consistent with the history of pollutant nitrogen emissions from the European continent, allowing a 20 year lag following the introduction of regulation of pollutant nitrogen in the 1970s. The three‐phase temporal transition in P in both basins was more consistent with the riverine phosphorus input, with a lag period of 20 years. Our analysis indicates that the recent dynamics of N and P in the upper MED Sea has been sensitive to the dynamics of anthropogenic nitrogen and phosphorus input from atmospheric deposition and rivers.

Fluxes and sources of nutrient and trace metal atmospheric deposition in the northwestern Mediterranean

“…This weekly As flux represents the annual flux measured in a remote environment like a Scandinavian forest (0.1 mg m −2 yr −1 on average between 2002 and2005;Hovmand et al, 2008). It is much larger than the weekly fluxes recorded in an urban environment such as Venice where the reported fluxes range from 0.7 to 367 µg m −2 wk −1 between 2005 and 2010 (Morabito et al, 2014). The As/Al ratio (0.011) for this event shows a large enrichment in As (×16) in comparison to the average of other intense dust events (7.10 −4 ), which is in agreement with the crustal ratio (Mason and Moore, 1982).…”

Estimating chemical composition of atmospheric deposition fluxes from mineral insoluble particles deposition collected in the western Mediterranean region

“…Atmospheric inputs supply as much nutrients as riverine inputs in the Mediterranean and are less confined to coastal waters (e.g. Moon et al, 2016;Richon et al, 2017). They play a significant role in marine nutrient cycles during the Mediterranean water stratification period, i.e.…”

Aerosol Deposition Impacts on Land and Ocean Carbon Cycles

“…3]. Smaller basins may be more sensitive to atmospheric deposition; for example, temporal trends in N and P suggest that an initial increase in nitrogen in the Mediterranean resulted in lower N concentration in response to higher atmospheric deposition, while the phosphorus budgets seem more driven by [170] using a recent simulation the riverine inputs [176,177]. Atmospheric deposition often results in an oscillatory deposition and response cycle that needs to be considered in understanding short and long time scale responses, especially in low-nutrient low-chlorophyll regions [178].…”