d15N of lipids in marine animals of the Dutch Wadden Sea

Lipid extraction of biomass prior to stable isotope analysis is known to cause variable changes in the stable nitrogen isotopic composition (d15N) of residual biomass. However, the underlying factors causing these changes are not yet clear. Here we address this issue by comparing the d15N of bulk and residual biomass of several marine animal tissues (fish, crab, cockle, oyster, and polychaete), as well as the d15N of the extracted lipids. As observed previously, lipid extraction led to a variable offset in d15N of biomass (differences ranging from -2.3 to +1.8 per mil). Importantly, the total lipid extract (TLE) was highly depleted in 15N compared to bulk biomass, and also highly variable (differences ranging from -14 to +0.7 per mil). The TLE consisted mainly of phosphatidylcholines, a group of lipids with one nitrogen atom in the headgroup. To elucidate the cause for the 15N-depletion in the TLE, the d15N of amino acids was determined, including serine because it is one of the main sources of nitrogen to N-containing lipids. Serine d15N values differed by -7 to +2 per mil from bulk biomass d15N, and correlated well with the 15N depletion in TLEs. On average, serine was less depleted (-3 per mil) than the TLE (-7 per mil), possibly due to fractionation during biosynthesis of N-containing headgroups, or that other nitrogen-containing compounds, such as urea and choline, or recycled nitrogen contribute to the nitrogen isotopic composition of the TLE. The depletion in 15N of the TLE relative to biomass increased with the trophic level of the organisms.

Potential of RapidEye image data for sediment monitoring of the German tidal flats

The Wadden Sea is located in the southeastern part of the North Sea forming an extended intertidal area along the Dutch, German and Danish coast. It is a highly dynamic and largely natural ecosystem influenced by climatic changes and anthropogenic use of the North Sea. Changes in the environment of the Wadden Sea, natural or anthropogenic origin, cannot be monitored by the standard measurement methods alone, because large-area surveys of the intertidal flats are often difficult due to tides, tidal channels and unstable underground. For this reason, remote sensing offers effective monitoring tools. In this study a multi-sensor concept for classification of intertidal areas in the Wadden Sea has been developed. Basis for this method is a combined analysis of RapidEye (RE) and TerraSAR-X (TSX) satellite data coupled with ancillary vector data about the distribution of vegetation, mussel beds and sediments. The classification of the vegetation and mussel beds is based on a decision tree and a set of hierarchically structured algorithms which use object and texture features. The sediments are classified by an algorithm which uses thresholds and a majority filter. Further improvements focus on radiometric enhancement and atmospheric correction. First results show that we are able to identify vegetation and mussel beds with the use of multi-sensor remote sensing. The classification of the sediments in the tidal flats is a challenge compared to vegetation and mussel beds. The results demonstrate that the sediments cannot be classified with high accuracy by their spectral properties alone due to their similarity which is predominately caused by their water content.

Bird count in Mastbos forest (Breda, Netherlands) in the years 1950 to 1981

Notes from Henrik de Nie: The project started as a phenological study in cooperation with the (Dutch) meteorological institute (KNMI) to register the time of arrival of Fitis and Tjiftaf. During 1951 to 1969 he went every day to the wood (except 1966, in this year his wife died). Thereafter he went no more daily, but because he knew the wood very well and he was free to choice the day on which he did a survey, therefore he choose days with relatively good weather. He did not observe very common bird species, maybe because they are dependent on nest boxes and he did not want to be dependent on the management of the nest box-people (in fact I forgot precisely his arguments, and now I cannot ask him this): Common Starling; Eurasian Tree Sparrow (not common); Great Tit; Eurasian Blue Tit Pieter mentioned 14 species that scored many zero values or only one observation: Stock Dove; Common Cuckoo; Lesser Spotted Woodpecker; Eurasian Golden Oriole; Eurasian Nuthatch; Short-toed Treecreeper; Common Nightingale; Marsh Warbler; Lesser Whitethroat; Goldcrest; Common Firecrest (after 1970 he had difficulties in hearing these two species); Spotted Flycatcher; Eurasian Bullfinch; Black Woodpecker He also mentioned species that he found much fewer as: European Greenfinch; European Pied Flycatcher; Long-eared Owl; Red Crossbill; Sedge Warbler; Icterine Warbler; Eurasian Woodcock; Eurasian Siskin; European Green Woodpecker; Great Spotted Woodpecker; Eurasian Hobby; Western Barn Owl; Woodlark; Common Wood Pigeon; Little Owl; European Crested Tit; Hawfinch. But for these species I think that observations are strongly dependent on the number of visits to the wood. Also here, many zeros and few 1 x during the whole series of visits.