A new approach to model oxygen dependent benthic phosphate fluxes in the Baltic Sea

• Published in: Journal of marine systems Vol. 144; pp. 127 - 141
• Main Authors: Almroth-Rosell, Elin, Eilola, Kari, Kuznetsov, Ivan, Hall, Per O.J., Meier, H.E. Markus
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2015
• Subjects: Baltic Sea; Biogeochemical modelling; Coastal; Deposition; Dynamics; Earth and Related Environmental Sciences; Eutrophication; Geovetenskap och miljövetenskap; Mathematical models; Ocean models; Oxygen penetration depth; Phosphates; Phosphorus; Phosphorus release; Saltwater inflow; Sediments; ANE, Baltic Proper; ANE, Baltic Sea; Phosphorus release; Saltwater inflow; Oxygen penetration depth; Biogeochemical modelling; Baltic Sea; Eutrophication; oxygen penetration depth; eutrophication; saltwater inflow; biogeochemical modelling
• ISSN: 0924-7963; 1879-1573; 1879-1573
• DOI: 10.1016/j.jmarsys.2014.11.007

The new approach to model the oxygen dependent phosphate release by implementing formulations of the oxygen penetration depths (OPD) and mineral bound inorganic phosphorus pools to the Swedish Coastal and Ocean Biogeochemical model (SCOBI) is described. The phosphorus dynamics and the oxygen concentrations in the Baltic proper sediment are studied during the period 1980–2008 using SCOBI coupled to the 3D-Rossby Centre Ocean model. Model data are compared to observations from monitoring stations and experiments. The impact from oxygen consumption on the determination of the OPD is found to be largest in the coastal zones where also the largest OPD are found. In the deep water the low oxygen concentrations mainly determine the OPD. Highest modelled release rate of phosphate from the sediment is about 59×103t P year−1 and is found on anoxic sediment at depths between 60–150m, corresponding to 17% of the Baltic proper total area. The deposition of organic and inorganic phosphorus on sediments with oxic bottom water is larger than the release of phosphorus, about 43×103t P year−1. For anoxic bottoms the release of total phosphorus during the investigated period is larger than the deposition, about 19×103t P year−1. In total the net Baltic proper sediment sink is about 23.7×103t P year−1. The estimated phosphorus sink efficiency of the entire Baltic Sea is on average about 83% during the period. •A new description of sediment phosphorus dynamics was implemented in a 3D-model.•Oxygen consumption affects oxygen penetration in coastal sediments.•Low oxygen concentrations determine the oxygen penetration in deeper water sediments.•More than 80% of the phosphorus loads (1980–2008) are retained in the Baltic Sea.•Phosphorus is released from anoxic sediments and retained in oxic sediments.