Massive Consumption of Gelatinous Plankton by Mediterranean Apex Predators

Stable isotopes of carbon and nitrogen were used to test the hypothesis that stomach content analysis has systematically overlooked the consumption of gelatinous zooplankton by pelagic mesopredators and apex predators. The results strongly supported a major role of gelatinous plankton in the diet of bluefin tuna (Thunnus thynnus), little tunny (Euthynnus alletteratus), spearfish (Tetrapturus belone) and swordfish (Xiphias gladius). Loggerhead sea turtles (Caretta caretta) in the oceanic stage and ocean sunfish (Mola mola) also primarily relied on gelatinous zooplankton. In contrast, stable isotope ratios ruled out any relevant consumption of gelatinous plankton by bluefish (Pomatomus saltatrix), blue shark (Prionace glauca), leerfish (Lichia amia), bonito (Sarda sarda), striped dolphin (Stenella caerueloalba) and loggerhead sea turtles (Caretta caretta) in the neritic stage, all of which primarily relied on fish and squid. Fin whales (Balaenoptera physalus) were confirmed as crustacean consumers. The ratios of stable isotopes in albacore (Thunnus alalunga), amberjack (Seriola dumerili), blue butterfish (Stromaeus fiatola), bullet tuna (Auxis rochei), dolphinfish (Coryphaena hyppurus), horse mackerel (Trachurus trachurus), mackerel (Scomber scombrus) and pompano (Trachinotus ovatus) were consistent with mixed diets revealed by stomach content analysis, including nekton and crustaceans, but the consumption of gelatinous plankton could not be ruled out completely. In conclusion, the jellyvorous guild in the Mediterranean integrates two specialists (ocean sunfish and loggerhead sea turtles in the oceanic stage) and several opportunists (bluefin tuna, little tunny, spearfish, swordfish and, perhaps, blue butterfish), most of them with shrinking populations due to overfishing

Anion interaction with ferrocene-functionalised cyclic and open-chain polyaza and aza-oxa cycloalkanes

A family of ferrocene-functionalised receptors of different topologies have been used as receptors for anions. The compounds have been designed to contain both amine nitrogen and ether oxygen atoms and comprises from monoaza to pentaaza derivatives both open-chain (L1, L2, L3) or cyclic (L4, L5) and having from one to five ferrocenyl groups. Solution studies directed to determine the protonation constants of L1, L2 and L3 have been carried out in water (0.1 mol dm3 KNO3, 25 °C) and those of L4 and L5 in 1,4-dioxane-water (70:30 v/v, 0.1 mol dm -3 KNO 3, 25 °C). The protonation behaviour of the receptors can be explained taking into account electrostatic considerations. Speciation studies in the presence of phosphate have been carried out in water for L', L2 and L3 and in dioxane-water for L4 and L5. Speciation studies have also been performed in the presence of ATP with L1, L2 and L3 in water. Selectivity of a mixture of receptors against a certain anion is discussed in terms of ternary diagrams. The shift of the redox potential of the ferrocenyl groups as a function of the pH has been studied. The difference between the oxidation potentials at basic and acidic pH has been determined experimentally and is compared with that theoretically predicted using an electrostatic model previously reported. The electrochemical shift in the presence of ATP and phosphate has been measured in water for L1, L2 and L3 and in the presence of phosphate and sulfate in 1,4-dioxane-water for L4 and L5 as a function of the pH. The electrochemical response found against those anions is quite poor with maximum cathodic shifts off. 30tO mV. The electrochemical response induced by HSO4 and H2PO4- has also been studied in acetonitrile solutions where a large cathodic shift for H 2PO 4- up to ca. 200 mV was found. © The Royal Society of Chemistry 2000

Cyclic and open-chain aza-oxa ferrocene-functionalised derivatives as receptors for the selective electrochemical sensing of toxic heavy metal ions in aqueous environments

A new family of aza-oxa open-chain and macrocyclic molecules functionalised with ferrocenyl groups have been synthesized and characterised. The crystal structures of the [HL1][PF6], [H2L3][PF6]2, [H2L4][PF6]2 and [H2L5][PF6]2 salts have been determined by single crystal X-ray procedures {L1 = 10-ferrocenylmethyl- 1,4,7-trioxa-10-azacyclododecane, L3 = 7,13-bis(ferrocenyl)-1,4,10-trioxa-7,13-diazacyclopentadecane, L4 = 1,8-bis[bis(ferrocenylmethylamino)]-3,6-dioxaoctane, L5 = 1,8-bis(ferrocenylmethylamino)-3,6-dioxaoctane}. They consist of cationic protonated amines linked via ionic interactions with hexafluorophosphate anions. Additionally hydrogen-bonding interactions have also been found. The receptors have been designed to promote discrimination, using electrochemical techniques, between toxic heavy metal ions such as Hg2+ over other commonly water present cations in aqueous environments. The presence in the receptors of oxygen and nitrogen donor atoms has been used to control the selectivity of large metal ions over small ones. Potentiometric and electrochemical studies have been mainly carried out to find pH ranges of selective electrochemical recognition. Potentiometric titrations were carried out in water (25°C, 0.1 mol dm-3 potassium perchlorate) for L1 and L2 [1,1′-(5,8-dioxa-2,11-diazadodecane-1,12-diyl)-ferrocene] and in 1,4-dioxane-water (25°C, 0.1 mol dm-3 potassium nitrate) for L3 and L5 with Ni2+, Cu2+, Zn2+, Cd2+, Pb2+ and Hg2+. All receptors show larger stability constants with Hg2+ than with the remaining metal ions studied. This is especially so for L1 and L2. The receptors L1, L2 and L5 are able electrochemically and selectively to sense the presence of Hg2+, whereas maximum electrochemical shifts are produced in L3 upon addition of Pb2+. Of importance is the large and selective electrochemical shift monitored in water for L2 and Hg2+ with an anodic displacement of the oxidation potential of ca. 130 mV which is one of the largest shifts ever reported in electrochemical cation sensing in water using related receptors. A good agreement has been found between potentiometric and electrochemical results. Selective electrochemical response against Hg2+ appears to be associated with (i) pH ranges of selective complexation or (ii) the existence of strong predominant receptor-metal complexes in a wide pH range. Additionally the electrochemical behaviour of receptors L1 and L2 in the presence of metal ions can be roughly predicted from potentiometric data. The stability constants of the complexes between L1 and Cu2+, Cd2+, Pb2+ and Hg2+ were also determined in the presence of Cl-. Whereas there is no important change in the stability constants of the L-H+-M2+ systems when M2+ = Cu2+, Cd2+ or Pb2+, there is a decrease of the co-ordination ability of L1 towards Hg2+. This is also reflected in electrochemical studies which demonstrate that [Hg(L1)]2+ electrochemically sense Cl- at pH 7. To the best of our knowledge this is the first time it has been shown that metal complexes functionalised with ferrocenyl groups can electrochemically sense anions