西印度洋地区海草生态系统

海草是海洋被子植物,广泛分布在温带和热带的海岸带水域,是地球上水生生态系统中最具生产力的生物之一.     

Remote sensing of the atmosphere by VHF radar experiments

Problems in atmospheric dynamics, in particular in micro- and mesoscale processes, which can be solved by radar investigations, are summarized. The method of atmospheric radar experiments is described. Some relevant results obtained with the new SOUSY-VHF-Radar are presented, including observations of a warm-front passage, of layered structures, and of vertical and horizontal velocities in the troposphere. A power profile of radar echoes from heights up to the stratosphere proves that the SOUSY-VHF-Radar in its final operating state will be able to investigate structures and dynamics in the mesosphere too.     

Isozymes and general protein patterns as taxonomic markers in the taxon Nephtyidae (Annelida Polychaeta)

Seven Nephtys species and one species of the genus Aglaophamus (collected from different European tidal and subtidal locations between 1989 and 1991) were compared with respect to six isozyme systems (-amylase, esterase, hexokinase, malate dehydrogenase, malic enzyme, phosphoglucoseisomerase) as well as with respect to general protein patterns with non-specific staining. The proteins were obtained from the tissue (proboscis, individual segments) of single individuals, the species of which had previously been accurately determined, and were separated by isoelectric focusing (IEF) in polyacrylamide gels. The enzymes were identified by their specific catalytic activities, and the general proteins were visualized by silver staining. All the isozymes proved to be monomorphic within each of the various polychaete populations. With a single exception, it was impossible to distinguish geographically separated populations of the same species, because the band patterns were completely consistent within the species. The individual enzymes varied in their suitability for species differentiation. Only with respect to esterase and -amylase could all species be distinguished; the other enzymes studied were identical in morphologically similar species. In contrast, each species could be identified by its general protein pattern, although some species differed from others in the position of a few bands only. Individuals of N. hombergii, N. caeca and N. cirrosa with abnormally shaped parapodia, as well as juvenile nephtyids, could be unequivocally assigned to their respective species by IEF. Only in the case of N. longosetosa were two morphological variants found to differ in their electrophoretic characteristics; one of them is interpreted as a new species, not previously described.     

Seasonal study of planktonic copepods and their benthic resting eggs in northern California coastal waters

Few investigations have examined the occurrence of zooplankton resting eggs in the sea bed of waters deeper than 20 m. In this study the distribution and abundance of planktonic copepods and their benthic resting eggs in coastal waters off northern California, U.S.A., were determined and related to environmental parameters (temperature, salinity, depth, and sediment grain size). Sediment cores, net tows, and CTD profiles were obtained in April and October 1989, and February, April, and October 1990. Water depths in the study area ranged from approximately 60 to 120 m. The mean abundance of eggs was as high as 1.2×10⁵ m^-2 for Acartia clausi Giesbrecht and 1.9×10⁵ m^-2 for Tortanus discaudatus Thompson and Scott. These egg concentrations are comparable to those reported previously for shallower more protected regions. The abundance of eggs in the sediments decreased with increasing depth of the water column. For the region as a whole, eggs were least abundant in muddy sediments. The mean abundance of eggs in the sea bed also varied seasonally and annully. Benthic resting eggs of A. clausi were more abundant in April 1989 than in April 1990, and adults of the species were never found in the plankton samples. The lack of adults is not unusual since results of previous studies indicate that A. clausi is a cold-water species, and in this region water temperatures are colder in summer, than in winter, due to upwelling. Temperature and salinity data indicated that the upwelling season had commenced by the time of the April 1990, but not the April 1989 sampling. Thus, the reduced abundance of benthic eggs in April 1990 may have been due to egg-hatching in response to reduced temperatures. The results suggest that the presence of A. clausi in coastal waters off northern California is linked to recruitment from benthic resting eggs.