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The Indonesian Seas play an important role in the marine global environment, from the oceanographic point of view as well as from the bioenvironmental perspective, since a large population of nearly 400 million people is living directly or indirectly in contact with these waters affecting the marine environment. In this chapter, we describe the history of oceanographic research in this region, the role of the Indonesian Seas in the global circulation, the most important features of the regional circulation, the distribution of tides, water exchange rates, and freshwater sources and sinks for certain subregions, and the effect of global warming as it is detectable nowadays already. Furthermore, we explain how satellite-derived data in connection with biooptical in situ measurements can support the investigation of the marine environment in a vast region, especially in coastal waters with respect to river discharge, transport of suspended matter, and primary production. Abstrak Perairan Indonesia memegang peranan penting dalam lingkungan laut global, mulai dari sisi oseanografis hingga ke perspektif lingkungan hidupnya, karena hampir 400 juta orang hidup berinteraksi baik secara langsung maupun tidak langsung dengan perairan yang berdampak pada lingkungan laut. Dalam bab ini dijelaskan sejarah penelitian oseanografi di wilayah ini, peran perairan Indonesia dalam sirkulasi global, fitur paling penting dari sirkulasi regional, distribusi pasang surut, percampuran air dan sumber air tawar dan pengurangannya untuk sub-daerah tertentu, serta efek dari pemanasan global yang sudah dapat dideteksi saat ini. Selanjutnya, kami menjelaskan bagaimana data satelit yang berhubungan dengan pengukuran in situ bio-optik dapat mendukung penelitian lingkungan laut di wilayah yang luas, terutama di perairan pesisir dengan adanya debit sungai, pengangkutan bahan-bahan tersuspensi dan produksi primer.

The Baltic Sea is a semi-enclosed, brackish water sea in northern Europe. The deep basins of the central Baltic Sea regularly show hypoxic conditions. In contrast, the northern parts of the Baltic Sea, the Bothnian Sea and Bothnian Bay, are well oxygenated. Lateral inflows or a ventilation due to convection are possible mechanisms for high oxygen concentrations in the deep water of the northern Baltic Sea. In March 2017, conductivity–temperature–depth (CTD) profiles and bottle samples, ice core samples, and brine were collected in the Bothnian Bay. In addition to hydrographic standard parameters, light absorption has been measured in all samples. A complementary numerical model simulation provides quantitative estimates of the spread of newly formed bottom water. The model uses passive and age tracers to identify and trace different water masses. Observations indicate a recent ventilation of the deep bottom water at one of the observed stations. The analysis of observations and model simulations shows that the Bothnian Bay is ventilated by dense water formed due to mixing of Bothnian Sea and Bothnian Bay surface water initializing lateral inflows. The observations show the beginning of the inflow and the model simulation demonstrates the further northward spreading of bottom water. These events occur during wintertime when the water temperature is low. Brine rejected during ice formation barely contributes to dense bottom water.

The Leeuwin Current (LC), an eastern boundary current, transports tropical waters from the Indo-Pacific Warm Pool (IPWP) towards southern latitudes and modulates oceanic conditions offshore southern Australia. New, high-resolution planktic foraminifer assemblage data and alkenone-derived sea surface temperatures (SST) provide an in-depth view on LC variability and mechanisms driving the current's properties during the mid to late Holocene (last c. 7.4 ka BP). Our marine reconstructions highlight a longer-term mid to late Holocene reduction of tropical heat export from the IPWP area into the LC. Mid Holocene (c. 7.4 to 3.5 ka BP) occurrence of high SSTs (>19.5 °C), tropical planktic foraminifera and a well-stratified water column document an enhanced heat export from the tropics. From c. 3.5 ka BP onwards, a weaker LC and a notably reduced tropical heat export cause oceanic cooling offshore southern Australia. The observed mid to late Holocene trends likely result from large-scale changes in the IPWP's heat storage linked to the El Nino-Southern Oscillation (ENSO) phenomenon. We propose that a strong and warm LC occurs in response to a La Nina-like state of ENSO during the mid Holocene. The late Holocene LC cooling, however, results from a shift towards an El Nino-like state and a more variable ENSO system that causes cooling of the IPWP. Superimposed on these longer-term trends we find evidence of distinct late Holocene millennial-scale phases of enhanced El Nino/La Nina development, which appear synchronous with northern hemispheric climatic variability. Phases of dominant El Nino-like states occur parallel to North Atlantic cold phases: the ‘2800 years BP cooling event’, the ‘Dark Ages’ and the ‘Little Ice Age’, whereas the ‘Roman Warm Period’ and the ‘Medieval Climate Anomaly’ parallel periods of a predominant La Nina-like state. Our findings provide further evidence of coherent interhemispheric climatic and oceanic conditions during the mid to late Holocene, suggesting ENSO as a potential mediator.

Photosynthetically available radiation (PAR) is one of the key requirements for primary production in the ocean. The ambient PAR is determined by incoming solar radiation and optical properties of sea water and the optically active water constituents along the radiation pathway. Especially in coastal waters, the optical properties are affected by terrigenous constituents like yellow substances as well as high primary production. Numerical models for marine ecosystems account for the optical attenuation process in different ways and details. For the consideration of coloured dissolved organic matter (CDOM) and shading effects of phytoplankton particles, we propose a dynamic parametrization for the Baltic Sea. Furthermore, products from biological turnover processes are implemented. Besides PAR and its attenuation coefficient, the model calculates the Secchi disk depth, a simple measurable parameter describing the transparency of the water column and a water quality parameter in the European Water Framework Directive. The components of the proposed optical model are partly implemented from other publications respectively derived from our own measurements for the area of investigation. The model allows a better representation of PAR with a more realistic spatial and temporal variability compared to former parametrizations. The effect is that regional changes of primary production, especially in the northern part of the Baltic Sea, show reduced productivity due to higher CDOM concentrations. The model estimates for Secchi disk depth are much more realistic now. In the northern Baltic Sea, simulated oxygen concentrations in deep water have improved considerably.

The coastal discharge of Indonesia is driven by high precipitation throughout the year. Monsoon and tides form a highly variable dynamical system that satellite remote sensing is the only method to acquire synoptic information. The large rivers of SE-Sumatra belong to the major tropical carbon and sediment sources for the world ocean. Knowledge of carbon sources is important because of their potential impact on coastal ecosystems and on climate change. Drainage of peatlands enhances the concentration of dissolved organic matter (DOM) and strong tidal currents the suspended particulate matter (SPM) load in the rivers. The high concentrations strongly reduce the available light in the water column of coastal regions. The coloured part of DOM (CDOM) absorbs light in the short wavelength range. Measured very high absorptions changed the colour brownish that the tributaries belong to so-called black water rivers. High SPM concentrations made the water milky and bright. Different compositions of water constituents led to large variations of water colour, which made ocean colour remote sensing to the preferred method for investigating river discharge and coastal transport in different spatial and temporal scales. Sources of different water masses were identified, the estuarine turbidity maximum zone and the spreading of river water in relation to tidal phases were detected. The transport processes in adjacent Malacca and Karimata Straits are described in relation to monsoon phases and ENSO. In addition to available satellite derived level 2 products, CDOM and DOC charts were retrieved using regional algorithms derived from measurements.

A series of molecular organic markers were determined in surface sediments from the Gulf of Genoa (Ligurian Sea) in order to evaluate their potential for palaeo-environmental reconstructions. Allochthonous input can be characterized by the distributions of n-C29 and n-C31 alkanes, n-C26 and n-C28 alkanols and branched glycerol dialkyl glycerol tetraethers (GDGTs), whose concentrations are generally highest near the river mouths. In the open basin however, terrestrial n-alkanes and n-alkanols may have an additional, eolian source. Autochthonous input is represented by crenarchaeol and isoprenoid GDGTs. Their concentrations are highest in the open basin showing the preference of Thaumarchaeota for oligotrophic waters. Indications of a significant degradation of sterols and C37 alkenones exclude these lipids as reliable productivity proxies. Using terrestrial and aquatic lipids as end-members allows estimating the percentage of terrestrial organic matter between 20% and 58% in the coastal area decreasing to 1–30% in the deep basin. The spatial distribution of sea surface temperature (SST) estimates using the alkenone-based UK′37 index is very similar to the autumnal (November) mean satellite-based SST distribution. Conversely, TEXH86-derived SST estimates are close to winter SSTs in the coastal area and summer SSTs in the open basin. This pattern reflects presumably a shift in the main production of Thaumarchaeota from the coastal area in winter to the open basin in summer. This study represents a major prerequisite for the future application of lipid biomarkers on sediment cores from the Gulf of Genoa.

Filaments are intrusions of upwelling water into the sea, separated from the surrounding water by fronts. Current knowledge explains the enhanced primary production and phytoplankton growth found in frontal areas by external factors like nutrient input. The question is whether this enhancement is also caused by intrinsic factors, i.e., simple mixing without external forcing. In order to study the direct effect of frontal mixing on organisms, disturbing external influx has to be excluded. Therefore, mixing was simulated by joining waters originating from “inside” and “outside” the filament in mesocosms (“tanks”). These experiments were conducted during two cruises in the northern Benguela upwelling system in September 2013 and January 2014. The mixed waters reached a much higher net primary production and chlorophyll a (chla) concentration than the original waters already 2–3 days after their merging. The peak in phytoplankton biomass stays longer than the chla peak. After their maxima, primary production rates decreased quickly due to depletion of the nutrients. The increase in colored dissolved organic matter (CDOM) may indicate excretion and degradation. Zooplankton is not quickly reacting on the changed conditions. We conclude that already simple mixing of two water bodies, which occurs generally at fronts between upwelled and ambient water, leads to a short-term stimulation of the phytoplankton growth. However, after the exhaustion of the nutrient stock, external nutrient supply is necessary to maintain the enhanced phytoplankton growth in the frontal area. Based on these data, some generally important ecological factors are discussed as for example nutrient ratios and limitations, silicate requirements and growth rates.

The dynamics of cooling water spreading in a non-tidal embayment is subject of a modelling-based study of Greifswald Bay, a shallow embayment at the south-western coast of the Baltic Sea. Potential cooling water spreading due to a possible power plant at Greifswald Bay is evaluated as differences between a realistic hind-cast simulation and a similar simulation but including the cooling water pumping. The model results are confirmed with satellite imagery of the embayment during operation of a nuclear power plant in the 1980s. The effect of cooling water pumping on the residual circulation, additional stratification and the heating of near-bed waters in the herring spawning areas is evaluated from the simulation. The model results for an idealised embayment and the realistic scenario, as well as the satellite images, show a clear dependence of the plume spreading on the wind direction. Although the surface plume affects a large area of the embayment, the results show a localised impact on residual circulation, bulk stratification and heating of the waterbody.

In the Baltic Sea, excess phosphorus after the spring bloom or phosphorus input from deeper layers e.g. by upwelling are nutrient sources for the development of filamentous cyanobacteria. The objective of this study was to investigate the ability of filamentous cyanobacteria to accumulate phosphate in depths within or below the thermocline under stratified conditions in the water column. Inorganic nutrient concentrations, as well as phytoplankton composition, chlorophyll a, POC, PON and POP and the ratios between them of water samples and of isolated filamentous cyanobacteria were estimated in five horizons of the upper 30 m surface layer together with phosphorus uptake and nitrogen fixation. During the investigation period, the water column was stratified with a surface temperature of 16 °C–18 °C in the eastern Gotland Basin. Cyanobacteria surface blooms occurred and constituted between 28 and 68% of the total phytoplankton biomass in the upper 5 m surface layer. Deduced from POC:POP ratios of 264–977, cyanobacteria were phosphorus depleted here. The POC:POP ratios became lower with increasing depth. In depths below 15 m, the cyanobacteria indicated phosphorus enrichment by POC:POP ratio declining down to 75 due to a forced gross uptake of 0.62 nmol P μg−1 Chla h−1compared to an uptake rate of 0.13 nmol P μg−1 Chla h−1 measured in the surface layer. Thus, filamentous cyanobacteria can acquire phosphate in deeper layers which enables further growth when they reach the surface. However, they occurred in low abundances there. In 30 m depth, cyanobacteria accounted for only 0.3–10% of their biomass in the surface layer. This contribution to bloom formation may therefore be of minor importance compared to other sources.

Hydrographic, current, and nutrient measurements were performed on board of the R/V Poseidon in the eastern Gotland Basin from 12 to 21 July 2007, complemented by satellite measurements of sea surface temperature and chlorophyll-a and by measurements of turbulent dissipation. The main aim of the investigations was to elucidate the pathways of phosphate from the intermediate winter water into the surface mixed layer and how this phosphate flux fosters phytoplankto growth. The deep water of the Gotland Basin was exposed to an enduring stagnation phase resulting in a nitrogen to phosphorus ratio very much lower than the Redfield ratio. The intermediate winter water was completely depleted of nitrate but contained a phosphate pool of about 0.40 µM. The surface mixed layer had a mean depth of about 18 m and water temperature of 16 °C and was depleted of both nitrate and phosphate. The average of photosynthetically active radiation during the cruise was about 700 µE/(m²s) at the sea surface. Three pulses of westerly wind with maximum wind speed of about 15 m/s forced upwelling during the cruise at the east coast of Gotland and downwelling at the Latvian coast. The corresponding eastward Ekman offshore transport moved surface water within about three days through the coastal boundary layer and in roughly 50 days across the Gotland Basin. Two mesoscale eddies were observed off the south eastern coast of Gotland which supported upwelling filaments near the southern tip of this island. Within the coastal boundary layer, the upwelling transported phosphate from the intermediate winter water into the surface layer off Gotland where it was mixed with the phosphate depleted surface water. Generally, the upwelled phosphate was taken up by the plankton community of the surface mixed layer already within the coastal boundary layer and transformed completely into the particulate and dissolved organic phase. However, at sites where upwelling filaments develop, dissolved phosphate is transported over a distance of about three times the internal Rossby radius in offshore direction. The phosphate transport into the surface mixed layer of the eastern Gotland Basin by upwelling exceeded the corresponding transport by turbulent mixing through the seasonal thermocline by about one order of magnitude during typical summerlike wind conditions.

In July 2007, phosphorus input by an upwelling event along the east coast of Gotland Island and the response of filamentous cyanobacteria were studied to determine whether introduced phosphorus can intensify cyanobacterial bloom formation in the eastern Gotland Basin. Surface temperature, nutrient concentrations, phytoplankton biomass and its stoichiometry, as well as phosphate uptake rates were determined in two transects between the coasts of Gotland and Latvia and in a short grid offshore of Gotland. In the upwelling area, surface temperatures of 11–12 °C and average dissolved inorganic phosphorus (DIP) concentrations of 0.26 μM were measured. Outside the upwelling, surface temperatures were higher (15.5–16.6 °C) and DIP supplies in the upper 10 m layer were exhausted. Nitrite and nitrate concentrations (0.01–0.22 μM) were very low within and outside the upwelling region. Abundances of filamentous cyanobacteria were highly reduced in the upwelling area, accounting for only 1.4–6.0% of the total phytoplankton biomass, in contrast to 18–20% outside the upwelling. The C:P ratio of filamentous cyanobacteria varied between 32.8 and 310 in the upwelling region, most likely due to the introduction of phosphorus-depleted organisms into the upwelling water. These organisms accumulate DIP in upwelling water and have lower C:P ratios as long as they remain in DIP-rich water. Thus, diazotrophic cyanobacteria benefit from phosphorus input directly in the upwelling region. Outside the upwelling region, the C:P ratios of filamentous cyanobacteria varied widely, between 240 and 463, whereas those of particulate material in the water ranged only between 96 and 224. To reduce their C:P ratio from 300 to 35, cyanobacteria in the upwelling region had to take up 0.05 mmol m −3 DIP, which is about 20% of the available DIP. Thus, a larger biomass of filamentous cyanobacteria may be able to benefit from a given DIP input. As determined from the DIP uptake rates measured in upwelling cells, the time needed to reduce the C:P ratio from 300 to 35 was too long to explain the huge bloom formations that typically occur in summer. However, phosphorus uptake rates increased significantly with increasing C:P ratios, allowing phosphorus accumulation within 4–5 days, a span of time suitable for bloom formation in July and August.

Interdisciplinary pollution studies were performed in the Siak River system in the Riau Province of East-Sumatra (Indonesia). Remote sensing investigations combined with in situ measurements in different seasons of the years 2004–2006 were focused on the identification of different sources of water masses in the tributaries and on the discharge into the estuary and Malacca Strait. Ship-borne measurements comprised the determination of the concentration and composition of optically active water constituents and water colour. Satellite data of different spectral and spatial resolution were implemented. Sources of different water masses such as humic substance dominated rivers, erosion areas of high suspended matter concentration and areas of limited bio-productivity are identified. Sources of humic substances are the rivers Tapung Kanan, Mandau, Siak Kecil, and Bukit Batu which are draining peatlands. The absorption coefficients of dissolved organic substances are partly (Siak Kecil, 51.8 m − 1 ) more than double of the currently admitted coefficients. The highest suspended matter concentrations near a channel between Siak and Siak Kecil leading to lowest transparency are caused by the estuarine turbidity maximum developing at the tidal front. The lowest Chlorophyll concentrations were measured between Pekanbaru and the channel, in and downstream of an industrial area. The concentration and distribution of water constituents are characterised by distinct regional patterns independent from the monsoon phases. The high absorption of dissolved organic humic substances originated from draining peatlands shifts the maximum of spectral reflectances to 700 nm leading to the extreme brownish to red-brownish water colour. High scattering of suspended particles increases the reflectance in the entire spectral range. The strong changes in the water colour enables satellite data of the visible spectral range to follow the distribution patterns of the Siak River discharge in the estuary which are strongly related to tidal phases. During low tide, the transport of Siak River water is directed into the Malacca Strait north-westwards and during high tide into Selat Panjang. Time series of daily available MODIS images have shown that the main transport direction in all seasons is the outflow into the Malacca Strait and further north-westwards following the large scale circulation.

During a dumping experiment on 20/21 June 2001, an extensive data record was collected to understand the dynamical processes in the water column of the investigation area and to validate model results. Weak westerly winds with strongly changing cloud coverage characterized the meteorological situation. During the second day the wind calmed down and moved shortly to easterly directions. The water column was characterized by a strong vertical stratification with discontinuity layers in temperature and salinity in 12 and 16 m. The current regime was dominated by outflow at the water surface and inflow along the German coast, with strong current shearing in the dumping area. The suspended matter clouds could be identified by optical methods and ADCP (Acoustic Doppler Current Profiler) scattering intensity. During the experiment the suspended matter plumes were only visible at the surface up to 1 h after the dumping. The aerial photographs document that the particle clouds at the surface drifted to the west and, after approximately 40 min, they were only weakly visible. The fine material was concentrated in the discontinuity layer leading to substantially higher values of optical parameters and suspended matter concentration than measured in the surface clouds. Due to the vertical current shears the material was transported in the water column in different directions. At the first day the maximum of the suspended matter in the discontinuity layer was in the north-western corner and in the bottom layer in the northeast corner of the dumping area. Strong wind conditions after the dumping led to periodical resuspension processes.

In the upwelling area along the Namibian coast of SW-Africa sulphur discolorations were investigated to study the impact of hydrogen sulphide on the ecosystem using satellite imagery. The formation of colloidal sulphur in the upper water layer results from the oxidation of hydrogen sulphide. The occurrence of sulphur plumes as well as their temporal and spatial development was investigated in relation to the driving meteorological and oceanographic conditions. Because of the sporadic occurrence of sulphur events and the limited number of ship-borne investigations in that area remote sensing of ocean colour is the only method to follow these phenomena continuously and synoptically. In the past the sulphur plumes were studied by true colour images derived from ocean colour satellite data like sea-viewing wide field of view sensor or moderate resolution imaging spectroradiometer and identified by their typical milky turquoise discoloration. For the first time, medium resolution imaging spectrometer (MERIS) reduced resolution Level-2 products were applied to identify sulphur discoloration in the surface water off Namibia. Based on their high spectral resolution typical spectral water-leaving reflectances were identified for sulphur enriched waters and distinguished from other optical water types dominated by absorbing or scattering phytoplankton groups and suspended matter. This was the basis for the development of a classification algorithm for the identification of sulphur plumes. This algorithm was derived on available MERIS scenes from the first half of the year 2004 and extended to summer 2005 to study the occurrence, the temporal and spatial development, the extension, and the strength of such events as well as inter-annual differences in these years. Only near-shore sulphur occurrences were identified in the considered time period compared to other studies. A lifetime of sulphur patches between 1 and 6 days and a zonal extent of up to 21 km were determined. The patches propagate in north-westerly direction with a current velocity of approximately 14 cm s −1 . The strongest events were detected in the Meob- and Saint Francis Bay in April 2004 and in April 2005.

Measurements of water-leaving reflectance and optically active water constituents in the Baltic Sea, the Namibian coastal area and the Atlantic Ocean were performed to validate MERIS Level-2 products. Two different validation methods were applied with the recommended match-up analysis based on comparison of in situ measurements with MERIS Level-2 products of simultaneous Envisat overpasses and the second analysis on comparison of natural variation ranges with derived MERIS product ranges. The MERIS water-leaving reflectances correlate to in situ shapes and magnitudes in all investigated areas. The comparison shows mean deviations of MERIS reflectances between 23% and 26% for the current official instrument processing facility (IPF 4.07) but only 20% for the prototype version 7.0 up to now only available to the validation team. The comparison of water constituents shows the underestimation of MERIS ALGAL_2 index, YSBPA and TSM in turbid waters of the Baltic Sea of the current instrument processing facility (IPF 4.07). The mean MERIS ALGAL_1 index is close to in situ values but the mean MERIS ALGAL_2 index, the MERIS YSBPA and MERIS TSM products are still too low in Namibian coastal areas for the prototype version 7.0. The investigations demonstrate the quality improvement of all MERIS Level-2 products from the current official instrument processing facility to the prototype version 7.0.

Sporadic occurrences of milky turquoise waters visible in true colour satellite imagery in the Benguela upwelling system off Namibia are characterized by high reflectances due to enhanced scattering properties. Previous opinion was that the features are due to increased reflectances by elemental sulphur (S0) resulting from upwelling or eruptions of hydrogen sulphide-enriched waters. In March/April 2003, a remotely sensed offshore plume was identified as a coccolithophore bloom for the first time in this region, followed by satellite imagery and intensively investigated using ship-borne measurements. Different methods were applied such as high-performance liquid chromatography (HPLC) pigment analysis, electronic disperse X-ray analysis, scanning electronic microscopy as well as spectral particle absorption and reflectance measurements. Ocean colour satellite data of the SeaWiFS and MERIS sensors were used to investigate the blooms. The SeaWiFS coccolithophore algorithm identified the bloom in March 2003. MERIS-derived spectral reflectances which were in a good agreement with in-situ measurements were used to study the occurrence of blooms in the first half of the year 2004. The observed offshore plumes can be optically divided into two groups. Far offshore the plumes are dominated by coccolithophores Emiliania huxleyi (Type-C) increasing the reflectance by scattering. Directly outside the active upwelling area the spectral shape of reflectance is affected by absorbing phytoplankton, but the magnitude is the result of scattering by coccolithophores and possibly diatom frustules. The coccolithophore bloom water was characterized by high calcite content, the occurrence of the marker pigment 19′- hexanoyloxyfucoxanthin as well as by a double maximum in the blue spectral range of the specific absorption of phytoplankton. The coccolithophore bloom develops as a phytoplankton succession during a low wind period in a stable stratified water body with a shallow top layer under high solar radiation with the starting conditions of low silicate and high N/P ratios. In the area off Namibia the sporadic occurrence of milky turquoise water may have two different causes. The features nearshore are due to sulphur discolouration but the further offshore plumes are caused by coccolithophores. The occurrence of coccolithophores is not as sporadic as the blooms which are visible in satellite data. These results improve the interpretation of milky turquoise water identified by ocean colour satellite data in the SE Atlantic Ocean off Namibia because they verified the occurrence of coccolithophores in that region for the first time with different methods.

The western Baltic Sea infront of the German coast is a highly variable dynamical system, dominated by a complex and small-scale morphometry, the water exchange between the Baltic and North Seas, and driven by local wind. Neither data collection, nor satellite images or model simulations alone were able to explain the observed spatial patterns and transport processes. Therefore, all these methods were combined to explain the dynamical features and to systematise them according to the typical local wind pattern and time series. The aim was to develop an instrument for regional authorities which supports the interpretation of coastal water monitoring data and forms a basis for an improved monitoring strategy. Satellite data of sea surface temperature and ocean colour from the sensors NOAA-AVHRR and SeaWiFS were applied for synoptic investigations in the entire region and Landsat-7-ETM+ for regional studies. Model simulations were performed for the western Baltic using a 3D model MOM-3 and for the Szczecin Lagoon using 2D model FEMFLOW. For the first time, regional particularities in the coastal dynamical features and processes are derived for the main wind directions and for transitions between dominant wind situations west and east as derived from wind statistics. The simulated transport of particles released from different coastal and open sea sources indicate the affected areas during changing forcing conditions. The results support the interpretation of acquired coastal monitoring data as well as the assessment and optimisation of the monitoring programme.

Inherent and apparent optical properties have been investigated in coastal regions and in the open Baltic Sea for more than 20 years. The area of investigation included the open parts of the central and western Baltic Sea and the Pomeranian Bight, with the largest fresh water inflow into the western Baltic via the Oder river. The main focus of the research was the seasonal and regional variation in the concentration and composition of optically active water constituents and their inherent optical properties and the influence on the apparent optical properties like spectral reflectance and the vertical attenuation coefficient. This publication combines results of earlier studies and new investigations on the absorption of yellow substances and the volume‐scattering function. A volume‐scattering phase function, an important variable in modelling of radiative transfer in the water, was derived for the Baltic Sea. The best correlation was found in a two‐term Henyey–Greenstein function, in contrast to the Petz...

Based on satellite imagery in combination with ground data measurements and numerical modelling, the distribution patterns of water masses along the German Baltic Sea coast of the state of Mecklenburg–Vorpommern (M–V) were investigated. The dynamic processes forming these patterns are driven by the local wind. Distinct wind directions induce typical features in several regions of the M–V coast. The processes considered are the distribution of Oder river water in the Pomeranian Bight, the upwelling off Hiddensee and off the coast of the Mecklenburg Bight including the Warnow river outflow, and the special dynamic regime in Lubeck Bay. In the Pomeranian Bight, a strong relation was found between the wind and transport direction of river water which was also applied to interpret the distribution of inorganic and organic pollutants. During easterly winds, different upwelling cells arise with the highest intensity in the Hiddensee area. The cells merge by increasing wind velocity. Lubeck Bay is mainly excluded...

SeaWiFS data were applied to investigate coastal processes in Indonesian waters around the most populated island of Java. Coastal processes due to wind forcing were studied the first time using SeaWiFS-derived chlorophyll and TSM concentrations in combination with AVHRR-derived SST in the period from September 1997 to December 2001. Upwelling events were studied along the southern coast of Java during the southeast monsoon (June to September). Satellite-derived chlorophyll concentrations higher than 0.8 mg / m 3 and sea-surface temperatures lower than 28°C are indications of upwelling. Upwelling events influence the distribution and growth of phytoplankton and provide by that good feeding condition for zooplankton, larvae, juvenile and adult of pelagic fish. Coastal discharge into the western Java Sea contains organic and inorganic materials originating from different sources. Diffuse impacts, particularly from fish farms and aquaculture, as well as coastal erosion influence large coastal areas during the rainy season (December to March), and to a lesser extent during the dry season. Strong Citarum river discharge was observed during the transition phase from the rainy to the dry season (March and April), when the maximum amount of transported material reaches the sea. The river plume is evident from chlorophyll concentrations higher than 2.5 mg / m 3 , and suspended particulate matter concentrations of more than 8 mg/dm 3 . The Sunda Strait is seasonally influenced by water transport from the Java Sea and from the Indian Ocean. The satellite data show that water transport from the Java Sea occurs during the pre-dominantly easterly winds period (June to September). This is characterized by warm water (SST higher than 29.5°C) and chlorophyll concentrations higher than 0.5 mg / m 3 . This water transport influences the fish abundance in the Sunda Strait. High fish catches coincide with the presence of Java Sea water, while the surface currents lead to the migration of pelagic fish. Conversely, during the dominant westerly winds period, oceanic waters from the Indian Ocean with low chlorophyll concentrations influence the Sunda Strait water.

In the area off Namibia satellite remote sensing data of the visible and infrared spectral range were used to investigate the upwelling processes and the biological response. Satellite derived Sea Surface Temperature was applied to study upwelling processes in relation to the driving trade winds. The investigations were focussed on the intensity and horizontal extent, the temporal and spatial variability including inter-annual and climate scales. Ocean colour satellite data allow investigation of the response of surface water to the nutrient input into the euphotic zone by upwelling processes. Observations in the area revealed, that the phytoplankton development starts with species absorbing light in the visible spectral range (diatoms and dinoflagellates) and may end in persistent shallow surface filaments with light scattering algae blooms. These blooms of coccolithophores identified by different in situ methods changed the water colour by strong particle scattering to milky turquoise discolorations. Further milky turquoise discolorations were identified as sulphur plumes. Low wind periods support the degradation of organic matter and the development of hydrogen sulphide in the bottom layer. After the onset of the trade winds and the offshore transport of surface water hydrogen sulphide enriched waters reaches with the near-bottom counter current the coast. Upwelling transports the water to the surface where the hydrogen sulphide will be oxidised to elemental sulphur. An algorithm was developed to identify and separate the sulphur plumes from algae blooms and other features on the basis of highly spectrally resolved satellite data from the MERIS sensor. The algorithm identified only coastal plumes as sulphur and that offshore plumes are formed by coccolithophores. The sulphur season is the boreal spring starting in February and reaching the maximum in April.

The main sources of nutrient supply in the area off Northwest Africa are upwelling and Saharan dust deposition. Their influence on phytoplankton development was evaluated by different methods. Statistical analyses showed that alongshore wind stress and induced upwelling were most significantly responsible for surface Chl-a variability mainly in winter and spring with delay of up to 16 days. Only 5 % of the Chl-a variability was related to the dust input. All strong Saharan dust storms between 2000 and 2008 were identified by remote sensed dust aerosol optical depth. Only some of the events caused a biological response expressed by an increase of surface chlorophyll-a. Time lags between dust deposition and enhancement of chlorophyll-a between 8 and 16 days were determined. The chlorophyll-a concentration was increased up to 2.4 mg m−3. Atmospheric dust modifies the amount and spectral distribution of the water light field. In the applied optical model the dust effect on incident solar radiation was parameterized by radiation measurements. The photosynthetically active radiation was reduced up to 19.3 % in the upper water column. The impacts of spectral effects on photosynthetically active radiation were different in oceanic and coastal regions. A compensation of the spectral effects at water depths of about 7 m was only observed in ocean regions because of different light attenuation in coastal areas. Saharan dust also impacts satellite derived ocean surface wind speeds. The influence depended mainly on the strength of dust storms, the microwave frequency and the wind speed. The impact was higher for stronger dust storms, higher frequencies and lower wind speeds.

The Oder (Odra) river is the most important nutrient source and pollutant for the south-western Baltic Sea. Adjacent German-Polish coastal waters, the Oder (Szczecin) Lagoon and the Oder (Pomeranian) Bight therefore suffer from severe eutrophication and water quality problems. At the same time, summer (bathing) tourism is the most important economical factor in this coastal zone, especially on the islands of Usedom and Wolin. On the basis of model simulations and remote sensing data we analysed the spatial extent and variability of the Oder river plume in the lagoon and the Balic Sea in common summer situations and during the extreme Oder flood in August 1997. Water quality shows pronounced gradients between coastal waters and open Baltic Sea. In the lagoon, it usually takes more than 6 weeks until Oder water enters the large western bay, the Kleines Haff. During transport, degradation, transformation and sedimentation processes alter the water quality and prevent the inner coast of Usedom from direct impact of polluted Oder water. Ongoing nutrient supply promotes intensive algal proliferation in all parts of the lagoon and contributes to the low water transparency. Oder water passing the lagoon and entering the Baltic Sea is transported over long distances in narrow bands along the shore. Under easterly winds the water quality near well-known spas on Usedom is reduced due to Oder river plume impact. Upwelling effects can have negative impact on water quality, too. Intensive blooms of potentially toxic blue-green algae species, are the rule in the lagoon and frequent in the Oder Bight in summer. They are a hazard and limit the acceptance of swimming beaches at the inner coast of Usedom. Practical consequences of variable water quality gradients e.g. on hygienic water sampling are discussed.

Changes in the levels and spatial distribution of polycyclic aromatic hydrocarbons (PAHs) as a consequence of the Oder flood in the summer of 1997 were investigated in surface water samples and fluffy layer material from the Oder Lagoon and the Pomeranian Bight. The measurements of the contaminants were complemented by satellite data to describe the spreading of the Oder flood discharge including the distribution of the particulate material. During the flood elevated levels of PAHs were discussed in the surface water and fluffy layer material of the Oder River Estuary in comparison to the average values in this region. These increased concentrations were attributed to flooding of municipal and industrial waste disposal areas in the drainage area of the Oder River. The meteorological conditions during the sampling period were characterized by predominant easterly winds, which guided the river plume along the German coast into the Arkona Sea, as verified by satellite observations. The highest concentrations of PAHs were observed near the mouth of the Swina and along the main direction of the river plume. Elevated concentrations of PAHs were also found in fluffy layer samples taken from the Oder Lagoon in late August. As derived from satellite data the eastern and the western parts of the lagoon differed in their SPM load during the entire flood period. The eastern part was covered by Oder water, while the western part contained a mixture of Oder Lagoon water. The highest concentrations of PAHs were not observed in the western part with the highest suspended matter values, but in the eastern part where the flood water entered the lagoon. Despite the significantly increased PAH levels measured during the flood, all measured concentrations were below the values that are considered to pose a risk to the ecosystem.

The impact of extreme weather, in terms of temperature, that is the seventh coldest winter 1995/1996 and the warmest summer 1997 in this century, on some peculiarities in nutrient concentrations in the Świna Strait is discussed on the basis of monthly mean sea surface temperature maps. These maps were derived from synoptic remote sensing data of the Advanced Very High Resolution Radiometer (AVHRR) operating at the NOAA (National Oceanic and Atmospheric Administration) weather satellites. The Swina Strait drains ca. 75 % of the water from the Szczecin Lagoon which is a recipient of the Oder waters. Severe winter 1995/1996 with low water temperature and ice sheet in the Oder estuary were found to be responsible for record low oxygen and high ammonium concentrations (90 μmol dm-3) in the Swina Strait. Moreover, harsh winter conditions resulted in passive transport of ammonium through the estuary in 1996; in contrast, mild winter’97 caused significant reduction of ammonium loads exported to the Pomeranian Bay. Delayed spring’96 caused later than in 1997 freshet water outflow and it suppressed/delayed biological uptake of nutrients (spring contribution of inorganic to total nitrogen discharged was by 19 % higher in 1996 than in 1997). Delayed sedimentation of freshly produced organic matter, together with low water temperature must have reduced PO4 fluxes from the sediments and therefore strengthened and prolonged phosphorus limitation of primary production in the Oder estuary on the turn of spring and summer 1996. Extremely hot summer’97 must have intensified phosphate fluxes at water column/sediments interface as their concentrations before the flood’97 were considerably higher than comparable ones in 1996 and 1998. High temperature and low oxygen content in July/August 1996 and 1997 were responsible for ammonium peaks, reaching ca. 20 μmol dm-3 in the Świna bottom waters in summer 1996 and during the Oder flood 1997. Both, high and low water temperatures play extremely important role in nutrient transformation in the Oder estuary.

Monthly mean Sea Surface Temperature (SST) maps derived from approximately 14.200 NOAA-AVHRR scenes for the period 1990–1998 were used to discuss seasonal and interannual climatic variations in the Baltic Sea in relation to air temperature and to solar radiation. In a validation analysis the comparison between SST data and time series as well as climatological in-situ temperatures showed very good correlations. The applicability of the meteorological parameters measured at the German coast is limited to the western and central Baltic Sea due to meteorological scales.

The winter of 1997/1998 was mild in the northern Baltic Sea and even very mild in the southern Baltic, among the warmest of this century. The summer and autumn were relatively cool in northern Europe. The mild winter led to sea surface temperatures that were 1 -1.5 K above the long-term mean during winter and early spring. This resulted in relatively warm water being trapped in the summer intermediate water layer of the central Baltic Sea. The surface temperatures in the summer lay close to the long-term mean due to the cool summer. The deep water temperatures of the central Baltic Sea were anomalously high, 0.5 -1.5 K above the mean for the period 1950–1998. The meteorological conditions gave rise to only several small inflows which had no significant effects in the central Baltic in 1998. As a result temperature and salinity in the deep water of the Gotland Deep decreased during the year. The inflow of saline and oxygen-rich, but unusually warm water into the Baltic Sea in autumn 1997 temporarily interrupted the anoxic conditions in the eastern Gotland Basin between January and April 1998. From May onwards hydrogen sulphide was again measured in the Bornholm Basin and, beginning in June, in the eastern Gotland Basin. The thickness of the anoxic deep layer increased in 1998 and spread southwards. Oxygen depletion also continued in the deep water of the western Gotland Basin resulting in the lowest annual mean in oxygen concentrations since the mid-eighties. This development indicates continuation of the stagnation that started in 1995 in the central Baltic deep water. In the winter of 1997/1998, the decrease in winter concentrations of nitrate appears to have continued whereas the phosphate concentrations were comparable to 1996/1997 levels. In 1998, the concentrations of organic nutrients lay in the range measured over the last years. The time series of dissolved organic carbon and nitrogen compounds indicated a gradient with increasing concentrations from the western to the central Baltic. The exceptional surface temperatures in summer 1997 combined with inflow events in autumn caused an unusual increase in the deep water temperatures of the central Baltic Sea in 1998. During the present century, such unusual high temperatures were only measured in 1977. Data from long-term measurements at representative stations were studied to identify periods of extreme temperatures and marked temperature trends in the central Baltic deep water between 1950 and 1998. In the entire Gotland Basin, the highest temperatures were observed in the late 1970s/early 1980s, and in the eastern Gotland Basin additionally in 1998. Low temperatures were measured before 1935, at the end of the 1980s/beginning of the 1990s, and during the mid-nineties. Significant trends in the deep water temperature regime occurred during the first half of the present century with a mean increase of 0.8 to 1.3 °C, and from the mid-seventies to the early 1990s when a drastic downward trend of 1.3–1.6 °C was observed due to the absence of major Baltic inflows.

The exceptional Oder flood in summer 1997 was a unique event in order to investigate the impacts on and the consequences for the ecosystem of the Baltic Sea of about 6.5 km3 additional water loaded with nutrients and contaminants and discharged within only 5 weeks. About 15 institutions participated in this investigation in both the Szczecin Lagoon and the Pomeranian Bight. The Baltic Sea Research Institute Warnemunde studied the water and nutrient inflow, the spreading of the Oder discharge, and the impact of the discharge on the ecosystem. The main topic of the presented investigations is a detailed study of the spatial and temporal spreading of the extreme river discharge in the Pomeranian Bight and the southern Baltic Sea by satellite data, ship observations and continuous buoy measurements as well as numerical modelling.

The winter of 1996/97 can be characterized as moderate in the western and central Baltic Sea but was only weak in the Gulfs of Bothnia, Finland and Riga. The temperatures in the winter surface and summer intermediate layers met the long-term mean. The summer of 1997 was the warmest since 1890. Water temperatures reached positive anomalies up to 6 K in the 10 m upper layer due to sunny weather conditions and weak winds during August.

In Eastern Boundary Upwelling Systems nutrient-rich waters are transported to the ocean surface, fuelling high photoautotrophic primary production. Subsequent heterotrophic decomposition of the produced biomass increases the oxygen-depletion at intermediate water depths, which can result in the formation of oxygen minimum zones (OMZ). OMZs can sporadically accumulate hydrogen sulfide (H2S), which is toxic to most multicellular organisms and has been implicated in massive fish kills. During a cruise to the OMZ off Peru in January 2009 we found a sulfidic plume in continental shelf waters, covering an area >5500 km(2), which contained similar to 2.2 x 10(4) tons of H2S. This was the first time that H2S was measured in the Peruvian OMZ and with similar to 440 km(3) the largest plume ever reported for oceanic waters. We assessed the phylogenetic and functional diversity of the inhabiting microbial community by high-throughput sequencing of DNA and RNA, while its metabolic activity was determined with rate measurements of carbon fixation and nitrogen transformation processes. The waters were dominated by several distinct gamma-, delta- and epsilon-proteobacterial taxa associated with either sulfur oxidation or sulfate reduction. Our results suggest that these chemolithoautotrophic bacteria utilized several oxidants (oxygen, nitrate, nitrite, nitric oxide and nitrous oxide) to detoxify the sulfidic waters well below the oxic surface. The chemolithoautotrophic activity at our sampling site led to high rates of dark carbon fixation. Assuming that these chemolithoautotrophic rates were maintained throughout the sulfidic waters, they could be representing as much as similar to 30% of the photoautotrophic carbon fixation. Postulated changes such as eutrophication and global warming, which lead to an expansion and intensification of OMZs, might also increase the frequency of sulfidic waters. We suggest that the chemolithoautotrophically fixed carbon may be involved in a negative feedback loop that could fuel further sulfate reduction and potentially stabilize the sulfidic OMZ waters.

The severe winter of 1995/96, which was among the coldest in the western and central Baltic Sea since 1946 (4th rank), caused negative temperature anomalies in the winter surface and summer intermediate waters. The surface temperatures remained below the long-term mean until July, but reached positive anomalies between 2 and 4 K in August due to sunny high pressure weather conditions and weak winds.

Radiation measurements in the area off Northwest Africa (research cruise, February 2008) and at Mindelo (Cape Verde Islands, May 2009) were used to investigate the impacts of Saharan dust and clouds on solar irradiance and on photosynthetically available radiation, to derive a relationship between dust aerosol optical depth (AOD) and photosynthetically available radiation and to determine the annual variations of photosynthetically available radiation. Three different kinds of atmospheric conditions were considered: cloudy skies, which decreased or increased the irradiance and dusty skies. The reduction by clouds was up to 67.2% at 400 nm and up to 84.4% at 700 nm. Enhancements of up to 21.9% at 400 nm and 34.0% at 700 nm were observed. The decrease by dust was up to 19.7% at 400 nm and up to 4.1% at 700 nm. Clouds decreased or increased the photosynthetically available radiation by up to 79.9% or up to 31.2%. The reduction by dust depended on the dust AOD and was between 3.6% and 12.3%. A linear relationship confirmed a decrease of photosynthetically available radiation of 1.2% by an increase of dust AOD of 0.1. Keywords: Saharan dust; downward solar irradiance; photosynthetically available radiation; Northwest Africa (Published: 30 January 2012) Citation: Tellus B 2012, 64 , 17160, DOI: 10.3402/tellusb.v64i0.17160

The western part of the Baltic Sea is a shallow transition area which is characterized by the water exchange between the Baltic and the North Sea. The dynamic processes in this area are forced by sea-level differences between the North Sea and Baltic Sea as well as by local wind and freshwater input. The response patterns are modified by Earth's rotation, bathymetric structures and the alignment of the coast. Series of satellite images permit synoptical views of these pattern and their temporal and spatial development.

Data of the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) are used to investigate phytoplankton blooms in the Baltic Sea in 1998 in combination with shipborne measurements and images of the Advanced Very High Resolution Radiometer (AVHRR) aboard the National Oceanic and Atmospheric Administration (NOAA) satellites. The SeaWiFS data were atmospheric corrected using an improved procedure, B. Sturm (1998). Algorithms derived for the Baltic were applied to retrieve the chlorophyll concentration and compared with the results of the standard SeaWiFS-algorithm and B. Sturm (1998). On the basis of SeaWiFS images of 1998 the spatial and temporal development of phytoplankton is studied. Meteorological conditions, ship measurements and NOAA-AVHRR derived sea surface temperature (SST) are considered to describe the initiating and influencing factors.

Satellite data of both sea surface temperature and ocean colour provide the opportunity to study dynamic features and the distribution of water constituents synoptically. A number of available and future satellite sensors with different spatial, temporal and spectral resolutions are presented. They allow to monitor both water temperature and quality in special areas influenced by algal blooms (including cyanobacteria) or in river water containing high concentrations of chlorophyll, suspended matter or yellow substances that change the turbidity. The optical properties and water constituents are also related to associated variables such as dissolved and particle-bound nutrients as well as inorganic and organic pollutants, especially in river mouth areas.

The summer of 1997 was exceptional in the Baltic Sea. Stable high pressure over Scandinavia in the first 10 days of August, associated with high solar radiation, resulted in the highest air and water temperatures of this century. These warm and calm conditions were favorable for a strong bloom of cyanobacteria in the southern Gotland Sea. In addition, two strong rainfall periods in the drainage area of the Oder River caused the century's most extensive regional flooding, with floodwaters reaching the Pomeranian Bight in August. Satellite data from different sensors and spectral ranges were used to study these specialevents. The monthly mean summer sea surface temperature (SST) distribution for the years 1990-1998, as derived from the National Oceanic and Atmospheric Administration (NOAA) Advanced Very-High Resolution Radiometer (AVHRR) data, showed a large interannual variation. The mean SST in the Baltic Sea exceeded 22°C in August 1997, the warmest month of the 1990s. In addition to SST, visible data from NOAA AVHRR and Indian Remote-Sensing Satellites (IRS-P3 and IRS-1C) Multispectral Optical Sensor (MOS) and Wide Field Sensor (WiFS) were used to investigate the blooms of cyanobacteria and coccolithophores and the distribution of river discharge during the Oder flood.

Spatial and temporal variations due to seasonal and regional development of phytoplankton and the freshwater inflow in river mouth areas influencing the optical properties in the Baltic Sea. The phytoplankton blooms in different seasons are dominated by special taxonomical groups. The variation intervals for the concentration of different optical active water constituents are presented. Regional and seasonal variations in the absorption of phytoplankton, detritus and gelbstoff are discussed in relation to the sources. The specific absorptions of chlorophyll show more regional differences than temporal. Measured volume scattering functions from the open Baltic and Pomeranian Bight are compared with published data. The bb/b- ratio deliver the known values for different dominating water constituents, which influences also the spectral shape the backscattering coefficient. Derived spectral specific absorption and backscattering coefficients were used to control the reflectance model by comparison to measurements of the total internal reflectance. Selected inherent optical properties for the spring bloom were included in the inverse procedure by Krawczyk et al. for the derivation of water constituents from simultaneous satellite data of the Modulator Optical Scanner at the Indian Satellite IRS-P3.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The variation of optical properties of water was studied in the open Baltic Sea and in coastal waters of the Pomeranian Bight for more than ten years. The optical properties in the open Baltic Sea are strongly influenced by plankton blooms with typical phytoplankton compositions. This led to significant seasonal variations in spectral reflectances. In coastal waters of the Pomeranian Bight, the origin of the water masses and the dwell period of the river water in different lagoon-like areas and bays determine the composition of the water constituents and their optical properties. Strong temporal and spatial variations in spectral reflectance, the spectral absorption of phytoplankton pigments, detritus and yellow substances were found within an area of 50 km2. The data set was used to develop ground truth algorithms to determine water constituents of Baltic Sea water from satellite data using CZCS, SeaWiFS, and MERIS.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Die Carbonyl-C-Atome von Ketonen (Aceton, Cyclohexanon) und Aldehyden (Propanal, 2,2-Dimethylpropanal, Acrolein, Benzaldehyd und p-Methoxybenzaldehyd) wurden uber ein – von Tetrabrommethan stammendes – Kohlenstoffatom zu trisubstituierten Allenen verknupft (9 und 10, siehe Schema 1). Die Reaktionssequenz besteht dabei aus vier Schritten: a) Olefinierung des Ketons zu einem 1,1-Dibromalken (1, 2); b) Br/Li-Austausch bei – 105 °C und Addition des entstehenden Brom-lithium-carbenoids (3, 4) an einen Aldehyd zum allylischen Bromhydrin (5, 6); c) O-Silylierung zum Silylether (7, 8); d) Eliminierung mit tert-Butyllithium zum Allen (9, 10). Preparation of Allenes from Geminal Dibromo Olefins and Aldehydes The carbonyl carbons of ketones (acetone, cyclohexanone) and aldehydes (propanal, 2,2-dimethylpropanal, acrolein, benzaldehyde, p-methoxybenzaldehyde) are joined through a single carbon atom (originating from carbon tetrabromide) to give trisubstituted allenes (9 and 10, see Scheme 1). The sequence consists of four operational steps: (i) olefination of the ketone to a 1,1-dibromoalkene (1, 2); (ii) Br/Li-exchange at – 105°C and addition of the resulting bromolithio-carbenoid (3, 4) to the aldehyde to give an allylic bromohydrine (5, 6); (iii) silylation at oxygen ( 7, 8) by treatment with chlorotrimethylsilane/hexamethyldisilazane/pyridine; (iv) elimination of the elements of BrOSiMe3 with tert-butylithium to produce the allenes (9, 10).

1,2,4-Pentatrien (1) dimerisiert beim Erhitzen auf 170°C in der Gasphase zu den Sechsringdimeren 2, 5 und 13, den Achtringkohlenwasserstoffen 8 und 18 sowie dem Tetrahydronaphthalin 16; in einer Nebenreaktion entsteht auserdem durch Cycloisomerisierung von 1 das 3-Methylen-1-cyclobuten (11). Die Bildung der C10H12-Kohlenwasserstoffe erfolgt vermutlich uber diradikalische Zwischenstufen, wobei nur 2, 5 und 13 Primarprodukte sind. Fur die Dimeren 8,16 und 18 konnen jedoch plausible elektrocyclische Bildungswege formuliert werden. Die sensibilisierte Photodimerisierung von 1 liefert die Cyclobutanderivate 31, 33 und 35 und als thermisches Folge-produkt von 33 das Achtringtetraen 28. Die ausschliesliche Cyclobutanbildung legt nahe, das sich 1 analog 1,3-Butadien bei sensibilisierter Photodimerisierung verhalt. Alkynes and Cumulenes, XIV. - Thermal and Photochemical Dimerization of 1,2,4-Pentatriene (Vinylallene) On heating at 170°C in the gas phase 1,2,4-pentatriene (1) dimerizes to the six-membered hydrocarbons 2, 5, and 13, to the eight-membered ring hydrocarbons 8 and 18 as well as to the tetra-hydronaphthalene 16; in a side reaction 1 cycloisomerizes to 3-methylene-1-cyclobutene(11). The C10H12-hydrocarbons are very likely produced via diradical intermediates, only 2, 5, and 13 being primary products. On the other hand, for the dimers 8, 16, and 18 reasonable electrocyclic reaction paths may be postulated. The sensitized photodimerization of 1 leads to the cyclobutane derivatives 31, 33, 35 and to 28 as a thermally produced secondary product from 33. The exclusive cyclobutane formation suggests that 1 behaves analogously to 1,3-butadiene in sensitized photo-dimerizations.

Die aus α-Bromlithiocyclopropanen und Aldehyden oder Ketonen erhaltlichen Bromhydrine (C, 2, 5) werden durch eine O-Silylierung mit Chlor- oder Iodtrimethylsilan/Hexamethyldisilazan/Pyridin und anschliesende Behandlung mit tert-Butyllithium in hohen Ausbeuten in Methylencyclopropan-Derivate (4a–f, 7) ubergefuhrt. Damit wird diese synthetisch nutzliche Substanzklasse leicht zuganglich aus Olefinen, Bromoform und Carbonylverbindungen (B). Preparation of Substituted Methylenecyclopropanes from gem.-Dibromocyclopropanes and Carbonyl Derivatives The bromohydrins (C, 2, 5) from α-bromolithiocyclopropanes and aldehydes or ketones can be O-silylated quantitatively by chloro- or iodotrimethylsilane/hexamethyldisilazane/pyridine. Treatment of the products (3, 6) thus obtained with tert-butyllithium at −95°C in THF/pentane and warming up to −25°C furnished methylenecyclopropanes (4a–f, 7) in >90% spectroscopic and in >65% “distilled” yields. These two steps complete a sequence which constructs the synthetically useful methylenecyclopropanes from an olefin, bromoform, and a carbonyl derivative (B).