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Abstract. The lipid and organic nitrogen isotopic (δ 15 N) compositions of two common deep-water corals (Lophelia pertusa and Madrepora oculata) collected from selected locations of the NE Atlantic are compared to the composition of suspended particulate organic matter, in order to determine their principle food source. Initial results suggest that they may feed primarily on zooplankton. This is based on the increased abundances of mono-unsaturated fatty acids and alcohols and the different ratios of the polyunsaturated fatty acids, 22:6/20:5 of the corals when compared to those of the suspended particulate organic matter. There is enrichment in L. pertusa of mono-unsaturated fatty acids and of δ 15 N relative to M. oculata. It is unclear whether this reflects different feeding strategies or assimilation/storage efficiencies of zooplankton tissue or different metabolism in the two coral species.

[1] Mechanisms supplying nitrogen (N) to phytoplankton, and thus constraining the levels of export production, over the oligotrophic subtropical Atlantic are assessed along a meridional transect. Stable nitrogen isotope signals reveal a localized region of N 2 fixation over the northern subtropical gyre. Elsewhere, particulate organic nitrogen was isotopically enriched and there was no widespread evidence of a trophic bias. Thus phytoplankton are utilizing an enriched source of N along the transect through much of the oligotrophic Atlantic, which may reflect utilization of nitrate from the deep ocean or, possibly, a supply of dissolved organic nitrogen (DON) from a non-N 2 fixing source. While there is a significant supply of DON over the subtropical gyres, reaching 0.15 mol Nm À2 yr À1 , less than 10% of the DON is semilabile and thus only implies a relatively small contribution to the nitrogen supply required for export production. Over the central part of the subtropical gyres, the supply of N to phytoplankton is probably from nitrate in the underlying thermocline, possibly from convection and diapycnic transfer, or more likely, from finescale upwelling by mesoscale eddies and frontal circulations. The lateral supply of dissolved organic phosphorus (DOP) appears to be a factor of 2-3 times more important than the lateral supply of semilabile DON, and thus might play a role in contributing to the phosphorus (P) supply for phytoplankton. The lateral supply of DON and DOP might also be important in closing the N and P budgets over the North Atlantic.

An extremely well-preserved dinosaur (Cf. Edmontosaurus sp.) found in the Hell Creek Formation (Upper Cretaceous, North Dakota) retains soft-tissue replacement structures and associated organic compounds. Mineral cements precipitated in the skin apparently follow original cell boundaries, partially preserving epidermis microstructure. Infrared and electron microprobe images of ossified tendon clearly show preserved mineral zonation, with silica and trapped carbon dioxide forming thin linings on Haversian canals within apatite. Furthermore, Fourier transform infrared spectroscopy (FTIR) of materials recovered from the skin and terminal ungual phalanx suggests the presence of compounds containing amide groups. Amino acid composition analyses of the mineralized skin envelope clearly differ from the surrounding matrix; however, intact proteins could not be obtained using protein mass spectrometry. The presence of endogenously derived organics from the skin was further demonstrated by pyrolysis gas chromatography mass spectrometry (Py-GCMS), indicating survival and presence of macromolecules that were in part aliphatic (see the electronic supplementary material).

Sedimentary evidence spanning the last 3500 years from cores taken from the centre of Gormire Lake, Cleveland, northeast England, points to two periods of deforestation and catchment erosion. The first, mainly late Iron Age/Romano-British phase, began c. 200 BC and ended c. AD 600. The second began c. AD 1200, the time of early Monastic activity, and continued into the nineteenth century. The chronology for the core rests on 137Cs, 210Pb and 14C measurements and on the history of lead accumulation in the sediments. The majority of the AMS 14C dates are shown to be too old to varying degrees, depending on the source of the organic matter in the sediments. The record of vegetation change is derived from pollen analysis. Evidence for changes in sediment composition and source and for catchment erosion comes from magnetic measurements, element analyses using XRF, and organic biogeochemical analyses. There is a high degree of coherence between all these lines of evidence. Interpretation of the magnetic record is complicated as a result of the formation of biogenic magnetite by magnetotactic bacteria, especially during periods of minimal erosion, by the presence of the authigenic magnetic sulphide greigite and by probable magnetite dissolution. Despite these modifications to the magnetic mineral assemblage in the sediments, magnetic indications of catchment erosion are clearly distinguishable, especially in the record of the antiferromagnetic minerals haematite and goethite. Partial estimates of catchment erosion rates are presented, based on the evidence from the sediments from the deepest part of the lake.

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Stable nitrogen isotopic determination of particulate organic matter over the eastern North Atlantic in spring 2000 reveal a region of low natural abundance of 15N relative to 14N between 26°N and 32°N along 20°W. This light isotopic signal, together with phytopigment data and persistently elevated nitrate to phosphate ratios in the upper thermocline, suggest that nitrogen fixation provides a local dominant supply of nitrogen to phytoplankton over part of the eastern North Atlantic. These independent biogeochemical proxies are coincident with a region of enhanced atmospheric dust deposition, as suggested by an atmospheric transport model. Hence, the atmospheric dust events may spatially and temporally constrain the distribution of N2 fixers.

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