The inner German Bight — an ecologically sensitive area as indicated by the bottom fauna

The muddy sediments of the sublittoral area of the inner German Bight are inhabited by a specialized macrofauna with few species. Long-term investigations on community and population dynamics have shown that the majority of this fauna are very susceptible to environmental stress (e. g. oxygen deficiency), and that the impoverishment trend recorded in 1977 has continued. The special hydrographic conditions of the inner German Bight, especially a long flushing time and the possibility of thermohaline stratifications, together with its function as a sediment trap are discussed. It is proposed that such areas should be considered as sensitive, and hence be protected from avoidable additional stress, e. g. introduction of wastes. This proposal is discussed with regard to the dangers arising from the view that muddy areas enriched with organic matter are inhabited by organisms preadapted to the decomposition of additional waste matter.     

The association between the caprellid Pariambus typicus Krøyer (Crustacea,Amphipoda) and ophiuroids

The work of Kazutsugu Hirayama over the past 25 yearspromoted the wide use of the marine rotifer Brachionusplicatilis as an experimental model in zooplanktonecology. His reports about the nature of geneticvariation in the B. plicatilis complex stimulated usto investigate how mate recognition maintains speciesboundaries. For the past several years, we haveexamined chemical communication between female andmale B. plicatilis. Here we report on the comparativebinding of polyclonal antibody against the materecognition pheromone (MRP) to three B. plicatilisstrains and three B. rotundiformis strains.Quantification of anti-MRP binding permitsinvestigation of how the female mating signal differsamong closely related Brachionus species and strains.Antibody binding reflects differentiation independentof the male receptor which has been describedelsewhere. Anti-MRP bound to females of all sixstrains and was localized in the corona. Antibodybinding greatly reduced mating in all three B. plicatilis strains. However, antibody bindingsignificantly reduced mating in only one of the B. rotundiformis strains. The MRP of both species has asimilar molecular weight, but the differential bindingsuggests that the mate recognition pheromone onfemales has differentiated in B. plicatilis and B. rotundiformis.     

Das de Mansche Organ der Oncholaimidae,eine genito-intestinale Verbindung bei Nematoden

The different types of the de Manian system are described and compared in 10 genera (for the first time in Viscosia and Oncholainmllus). By tracing a morphological sequence the organ is interpreted as a more or less segregated appendix of the female genital tube (duplication theory). The organ, which has distally an ingrowth of intestinal tissue, functions as a seminal receptacle.

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Hauptteil einer Dissertation zur Erlangung des Doktorgrades der Mathematisch-Naturwissenschaftlichen Fakultät der Universität Hamburg, angenommen am 16.4. 1969. Der Teil Systematische Bemerkungen zur Familie der Oncho laimidae wird in den Veröffentlichungen des Instituts für Meeresforschung in Bremerhaven erscheinen (Rachor, 1970). Die Untersuchungen wurden mit Unterstützung der Deutschen Forschungsgemeinschaft durchgeführt.     

BIODIVERSITY RESEARCH: Turning up the heat: the impacts of Andropogon gayanus (gamba grass) invasion on fire behaviour in northern Australian savannas

Aim This study aimed to quantify changes in fire severity resulting from the invasion of Australia’s tropical savannas by the African grass Andropogon gayanus Kunth. (gamba grass). Location Mesic savannas of the Northern Territory, Australia. Method Byram’s fire‐line intensity (I_f), fuel load and architecture, and two post‐fire indicators of fire intensity – scorch height (SH) and char height (CH) of woody vegetation – were determined for fires in native grass savanna and A. gayanus invaded savanna. Leaf scorch is the height at which the fire’s radiant heat browns leaf tissue, and leaf char is the height that radiant heat blackens or consumes leaf tissue and provides an indirect measure of flame height. These data, and 5 years of similar data collected from the Kapalga Fire Project in Kakadu National Park, were used to develop empirical relationships between I_f and the post‐fire indices of fire intensity. Results A relationship between A. gayanus I_f and SH could not be developed because complete canopy scorch occurred in most A. gayanus fires, even at low I_f. In contrast, A. gayanus I_f was strongly correlated with CH. This empirical relationship was substantially different from that for native grass fires. For a given I_f, there was a significantly greater CH in invaded sites. This increase in radiant heat is attributable to the increased biomass (mean 3.6 t ha^?1 in native grasses compared to 11.6 t ha^?1 in A. gayanus) and height (approximately 0.5 m in native grasses compared to 4 m in A. gayanus) of the standing fine fuel. Main conclusion Andropogon gayanus invasion resulted in substantial changes in fire behaviour. This has important regional implications owing to the current (10,000–15,000 km²) and predicted (380,000 km²) area of invasion and the negative consequences for the native savanna biota that has evolved with frequent but relatively low‐intensity fire.     

Faunenverarmung in einem Schlickgebiet in der Nähe Helgolands

Variations in abundance and species composition of macro-zoobenthos were studied at a sublittoral muddy-bottom station in the inner part of the German Bight from 1969 to 1976. The fauna of this area can be included in the classicalAbra alba community. A total of 98 species were found in 62 samples. Of these, only 4 species occurred in all samples:Nucula nitidosa, Diastylic rathkei, Ophiura texturata andNephtys hombergii. Species richness has declined since 1969. Populations of several species disappeared in the investigated area and its surroundings. Other populations are shown to exhibit remarkable fluctuations in abundance with sometimes heavy spatfalls or sudden breakdowns in population density, mainly during late summer. The long-term trend of impoverishment of the fauna is attributed to the development of anaerobic conditions in the muddy sediment. Such conditions are favoured by stable, thermohaline strafications of the water during summer, resulting in low oxygen levels and, probably, enrichment of hydrogen sulfide even in near-bottom water. Moreover, both continuou influx into the area of Elbe water, rich in suspended matter and nutrients and dumping of sewage sludge about 8 km east of the investigated area are considered to have increased the strees on the bottom fauna.     

Sesquiterpenes and a phenylpropanoid from Cordia trichotoma

Two new secondary metabolites, the phenylpropanoid 3-(2',4',5'-trimethoxyphenyl)propanoic acid (1) and the sesquiterpene (+)-1beta,4beta,6alpha-trihydroxyeudesmane (2) were isolated from the heartwood of Cordia trichotoma Vell., along with the known sesquiterpenes (-)-1beta,4beta,7alpha-trihydroxyeudesmane (3) and (+)-1beta,4beta,11-trihydroxyoppositane (4). Their structures were elucidated by means of spectroscopic data interpretation, mainly 1D and 2D NMR and mass spectrometry.     

A seafloor crater in the German Bight and its effects on the benthos

 In 1963 a deep crater was formed about 65 m below sea level in the western part of the German Bight, due to a gas eruption caused by drilling carried out from the platform ’Mr. Louie’. The study area is situated in a sandy to muddy bottom area inhabited by an Amphiura filiformis association (sensu Salzwedel et al. 1985). The crater, sometimes called ’Figge-Maar’, functions as a sediment trap, concentrating particles and organisms from the water column, thus leading to extreme sedimentation rates of about 50 cm, on average, per year. Crater stations, compared with stations situated in the vicinity, show enrichments of juveniles. Echinoderms, especially the subsurface-dwelling heart urchin Echinocardium cordatum and ophiuroids are responsive to enrichment. Other species that are typical of the Amphiura filiformis association are shown to be unable to cope with the special conditions in the crater. Received: 12 June 1998 / Accepted:16 September 1998     

Red List of macrofaunal benthic invertebrates of the Wadden Sea

Parasites were observed in medium- and small-sized fish taken from the discards of a commercial shrimper during seven different cruises in the tidal channels of the North Frisian Wadden Sea (Süderaue, North Sea) from April to September 1991. In total, 442 fish comprising four species (Sprattus sprattus, Hyperoplus lanceolatus, Ammodytes tobianus, Pomatoschistus minutus) were investigated. The parasite fauna consisted of 22 species. The parasite community structure of the 4 hosts was compared. The diet of the hosts seemed to be the main factor determining the structure of the parasite community. Other factors could not be assessed. Eight species of parasites occurred as larval stages. This indicated that fish were intermediate or paratenic hosts in their life cycle. The nematodeHysterothylacium sp. (Anisakidae) and the digeneanCryptocotyle lingua (Heterophyidea) were the dominant parasites, reaching their highest prevalence and density in sprat and sand eel. Sprat and sand eel play a very important role in parasite transmission to predacious fish and seabirds.     

An annotated checklist of macrozoobenthic species in German waters of the North and Baltic Seas

The present compilation is the first attempt to generate a comprehensive list of all macrozoobenthic species recorded at least once in the German regions of the North Sea and Baltic Sea including non-indigenous species and freshwater species which occurred in brackish waters (estuaries, bays, fjords etc.). Based on the data of several research institutes and consultancies, the macrozoobenthic species inventory comprises a total of 1.866 species belonging to 16 phyla including 193 threatened species. The most common groups were: malacostracan crustaceans (21%), Polychaeta (19%), and Gastropoda (12%). Even though the two major marine regions are separated by only 50 km of land, the composition of the respective communities was different. The two seas shared only 36.6% of the recorded species which should have profound and far-reaching consequences for conservation purposes. Considering all macroinvertebrates listed 96 species, or the equivalent of 5.2%, were introduced mainly during the last two centuries. Both seas are heavily affected by human activities and are sensitive to climate change displayed by effects on the faunal compositions. The present checklist is an important step to document these changes scientifically and may act as a base for political and management decisions.     

Interactions between Plants and Epiphytic Bacteria Regarding Their Auxin Metabolism

Proofs of different kind are presented of the existence of highly active bacteria producing IAA from tryptophan on plant surfaces and in plant homogenates. Both homogenates and washing solutions of nonsterile pea plant parts are active in producing IAA from tryptophan. Activity is much enhanced by the addition of glucose or by preincubating the preparations; it is abolished by sterile filtration, by some bactericidic and bacteriostatic substances, by chloramphenicol, streptomycin, and albucid (penicillin being only partly effective). Preparations of sterile plants do not produce IAA from tryptophan within the detection limit of the Salkowski test. The bacteria are even present on seed surfaces, in the air, and in aceton or ammonium sulfate precipitations of homogenates. Main products of the bacterial tryptophan conversion, as demonstrated by paper chromatography, are indolepyruvic acid, indoleacetic acid, indolecarboxaldehyde, and indolecarboxylic acid. In presence of glucose indolepyruvic acid is by far dominating. Many hitherto known results about tryptophan conversion to IAA by higher plants are likely to be falsified by epiphytic bacteria.