Deep Sea Research Part II: Topical Studies in Oceanography
Summary and overview of the CYCLOPS P addition Lagrangian experiment in the Eastern Mediterranean
Introduction
This manuscript presents an overview of the CYCLOPS program and in particular a synthesis of the results of the P-addition experiment. Here we describe briefly the initial background and aims of the project. The location of the study area and the conditions in the surface waters prior to the experiment are presented, followed by a brief description of the logistics of the Lagrangian experiment. The sampling and methods of all the experiments are summarized. After describing the physical conditions in the Cyprus Eddy during the experiment, the biological changes caused by addition are summarized together with those chemical changes that are not presented elsewhere in this volume. A synthesis of the overall meaning of all the CYCLOPS results is then given. This is followed by a broad overview of the implications of our new understandings of the controls on nutrient cycling in the Eastern Mediterranean for environmental studies in the Eastern Mediterranean and elsewhere.
Section snippets
The logical basis for the CYCLOPS experiment
The Mediterranean in general and the eastern basin in particular is one of the largest bodies of water in the world that is thought to be phosphorus-limited (Krom et al., 1991). This conclusion was based originally on the molar ratio of nitrate:phosphate in the deep water of the Eastern Mediterranean, which is 29:1 (Kress and Herut, 2001; Krom et al., 1991, Krom et al., 2005) and far higher than that in the Western Mediterranean (23:1) and the Eastern North Atlantic (16:1). In the Eastern
The Eastern Mediterranean as a vulnerable ecosystem
The Mediterranean in general and the Eastern Mediterranean in particular is ultra-oligotrophic with the lowest nutrient content in the world found in its deep waters as well as nutrients below conventional analytical detection limits in its surface waters. This is caused by its unusual anti-estuarine circulation. Nutrient-depleted surface waters flow into the basin at the straits of Gibraltar and Sicily, while intermediate waters containing significant amounts of dissolved inorganic nutrients
Description of the CYCLOPS program
In May 2000 a microcosm experiment was carried out in the National Institute of Oceanography, Haifa, Israel. The purpose of this experiment was to test analytical methodologies for use in the ultra-oligotrophic conditions found in the South-East Levantine basin and to conduct a preliminary, controlled examination of the response of Eastern Mediterranean surface water to nutrient additions. In this experiment nitrate, phosphate and glucose were added to microcosm bottles and the biological and
Practical description of the May 2002 P-addition experiment
The P-addition experiment was undertaken on 17–27 May 2002 from the R/V Aegaeo in the center of the Cyprus Eddy (see Fig. 1). The phosphate solution was prepared prior to sailing on the quay at Limassol, Cyprus, by adding concentrated phosphoric acid to 500 kg of sodium bicarbonate in nutrient-depleted seawater in 6×3000-l tanks. The final mean concentration of ∼2.2 M dissolved inorganic orthophosphate was confirmed by direct measurement. SF6 saturation was achieved using an in-line saturation
Sampling and methods
Details of all the casts taken and the measurements made in each cast are given in Table 1, Table 2. A full listing of this information together with all the measurements made is available on the CYCLOPS website (www.earth.leeds.ac.uk/cyclops). The chemical and biological parameters determined during this study are given in Table 2. All of the methods for the data presented elsewhere in this volume are given in the relevant papers. The details of methods given below are only for the chemical
Physical oceanography of the Cyprus Eddy during the CYCLOPS experiment
The CYCLOPS addition experiment was carried out as close as was possible to the center of the Cyprus warm-core Eddy. This was done for practical reasons. The Eastern Mediterranean is highly dynamic. The CYCLOPS experiment was limited by having to raise P concentration significantly and the only way to do this practically was to start with a small patch. By carrying out the experiment in the center of a warm-core eddy we made it easier to constrain and thus follow the patch over time.
The Cyprus
Understanding the response of the microbial community to the P-addition
It is suggested that there are three, not mutually exclusive, mechanisms that could explain the observed increase in bacterial activity and positive predator responses, together with a decrease in phytoplankton biomass. One could be termed a “trophic bypass” mechanism. In this process, the added phosphate gets directly to the grazing part of the predatory food chain from the heterotrophic bacteria bypassing the phytoplankton compartment (Fig. 12). The second process is a “trophic tunneling”
Acknowledgements
This project was funded by the EU through project EVK3-CT-1999-00009 “CYCLOPS”. We wish to thank the crew of R/V Aegaeo for endurance and assistance, particularly the captain and first officer, Konstantinos Chandros and Theodoros Kanakaris for their enduring patience and the ships bosun Vassilis Panagiotopoulos who was consistently interested in what we were doing. His prayers to the sunset were memorable. The second cruise upon which most of this project was based took place from Limassol. We
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2019, Science of the Total EnvironmentCitation Excerpt :Redfield ratio (C:N:P:Fe – 106:16:1:0.001) is considered the optimal nutrient proportion for algal growth. Two field experiments were performed with addition of phosphorus in low nutrient waters (Krom et al., 2005): (i) using concentrated phosphoric acid mixed with sodium bicarbonate; and (ii) using anhydrous monosodium phosphate. In the Mediterranean, the addition of phosphorus was associated with the growth of bacteria and zooplankton, and a modest increase of nitrogen fixation rates.
The deep water of Eastern Mediterranean Sea is a hotspot for bacterial activity
2019, Deep-Sea Research Part II: Topical Studies in OceanographyCitation Excerpt :Inorganic nutrients (NO2+NO3, PO4) median concentrations in the epipelagic layer were usually close/below the detection limit in the Eastern Basin and 0.12 μmol kg−1 and 0.023 μmol kg−1 for NO2+NO3 and PO4, respectively, in the Central-eastern basin (t-test, p < 0.05, Tables 2 and 3). These values are similar to that previously shown in the EMS (Krom et al., 2005; Tanhua et al., 2013; Kress et al., 2014). Nutrient concentrations significantly increased with water depth, reaching values in the meso- and bathypelagic depths that are one order of magnitude higher than those measured in the epipelagic water (NO2+NO3, 3.29–5.24 μmol kg−1 average concentration in the meso- and bathypelagic depths; and PO4, 0.15–0.20 μmol kg−1 average concentration in the meso- and bathypelagic depths, Tables 2 and 3).