On the impact of the Bimodal Oscillating System (BiOS) on the biogeochemistry and biology of the Adriatic and Ionian Seas (Eastern Mediterranean)

Analysis of 20-year time-series of the vertically averaged salinity and nutrient data in the Southern Adriatic shows that the two parameters are subject to strong decadal variability. In addition, it is documented that nutrient and salinity variations are out of phase. Nutrients in the Ionian and in the Adriatic vary in parallel except that generally the nutrient content in the Adriatic is lower than in the Ionian, a fact that has been attributed to primary producer consumption following the winter convective mixing. As shown earlier, North Ionian Gyre (NIG) changes its circulation sense on a decadal scale due to the Bimodal Oscillating System, i.e. the feedback mechanism between the Adriatic and Ionian. Cyclonic circulation causes a downwelling of the nitracline along the borders of the NIG and a decrease in the nutrient content of the water flowing into the Adriatic across the Otranto Strait, and vice versa. In addition, the highly oligotrophic central area of the Ionian shows annual blooms only during cyclonic NIG circulation. Inversion of the sense of the NIG results in the advection of Modified Atlantic Water or of the Levantine/Eastern Mediterranean waters in the Adriatic. Here, we show that the presence of allochtonous organisms from Atlantic/Western Mediterranean and Eastern Mediterranean/temperate zone in the Adriatic are concurrent with the anticyclonic and cyclonic circulations of the NIG, respectively. On the basis of the results presented, a revision of the theory of Adriatic ingressions formulated in the early 1950s is proposed

Effects of external nutrient sources and extreme weather events on the nutrient budget of a Southern European coastal lagoon

The seasonal and annual nitrogen (N), phosphorus (P), and carbon (C) budgets of the mesotidal Ria Formosa lagoon, southern Portugal, were estimated to reveal the main inputs and outputs, the seasonal patterns, and how they may influence the ecological functioning of the system. The effects of extreme weather events such as long-lasting strong winds causing upwelling and strong rainfall were assessed. External nutrient inputs were quantified; ocean exchange was assessed in 24-h sampling campaigns, and final calculations were made using a hydrodynamic model of the lagoon. Rain and stream inputs were the main freshwater sources to the lagoon. However, wastewater treatment plant and groundwater discharges dominated nutrient input, together accounting for 98, 96, and 88 % of total C, N, and P input, respectively. Organic matter and nutrients were continuously exported to the ocean. This pattern was reversed following extreme events, such as strong winds in early summer that caused upwelling and after a period of heavy rainfall in late autumn. A principal component analysis (PCA) revealed that ammonium and organic N and C exchange were positively associated with temperature as opposed to pH and nitrate. These variables reflected mostly the benthic lagoon metabolism, whereas particulate P exchange was correlated to Chl a, indicating that this was more related to phytoplankton dynamics. The increase of stochastic events, as expected in climate change scenarios, may have strong effects on the ecological functioning of coastal lagoons, altering the C and nutrient budgets.Portuguese Science and Technology Foundation (FCT) [POCI/MAR/58427/2004, PPCDT/MAR/58427/2004]; Portuguese Science and Technology Foundation (FCT

The role of EMODnet Chemistry in the European challenge for Good Environmental Status

The European Union set the ambitious objective to reach within 2020 the goal of Good Environmental Status. The European Commission (2008) represents the legislative framework that drives member state efforts to reach it. The Integrated Maritime Policy supported the need to provide a European knowledge base able to drive sustainable development by launching in 2009 a new European Marine Observation and Data Network (EMODnet). Through a stepwise approach, EMODnet Chemistry aims to provide high-quality marine environmental data and related products at the scale of regions and sub-regions defined by the Marine Strategy Framework Directive. The chemistry lot takes advantage and further develops the SeaDataNet pan-European infrastructure and the distributed approach, linking together a network of more than 100 National Oceanographic Data Centres providing data from more than 500 data originators. The close interaction with EEA, RSCs, ICES and EMODnet–MSFD coordination group facilitated the identification of the most appropriate set of information required for the MSFD process. EMODnet Chemistry provides aggregated and validated regional data collections for nutrients, dissolved gasses, chlorophyll, and contaminants, properly visualized with OGC WMS and WPS viewing services. Concentration maps with 10-year moving window from 1960 to 2014, by season and for selected vertical layers, are computed and made available

Nutrient depletions in the Ross Sea and their relation with pigment stocks

The present article depicts a first attempt to relate the governing nutrient uptake regime and phytopigment signature of the Ross Sea. Based on nutrient and phytopigment data obtained during two cruises in the Ross Sea, two distinct groups were recognised. The first one was characterised by moderate nutrient nitrate and silicic acid depletions in combination with relatively high diatom and Phaeocystis abundance. The second group showed very low nutrient depletions and very poor diatom abundance. Average depth specific nitrate depletions were 8.1 and 1.1 μM and average silicic acid depletions were 21.5 and 1.3 μM, respectively. The nutrient consumption patterns did not match the conditions of silicic acid excess (SEA) or nitrate excess areas (NEA), a clear trend being probably obscured by very poor seasonal maturity of several sampling stations. The contrast between both groups is largely explained by small differences in nitrogen uptake regime of the major phytoplankters. During early season, the diatoms meet the majority of their nitrogen requirements by nitrate uptake, with few exceptions where ammonium is the most important nitrogenous substrate. On average, their nitrate uptake capacity is lower than that of Phaeocystis (average specific nitrate uptake rates were 0.021 and 0.036 day y-1 for diatoms and Phaeocystis, respectively). The latter phytoplankton always shows predominance of nitrate uptake. Both groups are subject to inhibition of nitrate uptake when ammonium availability increases, and it is likely that the diatoms are more sensitive to the inhibitory effect of ammonium