Micro- and picoplankton in waters of the Saint Paul Island, Pribilof Islands, Bering Sea

On the basis of materials collected in June-August 1994 characteristic data on microplankton were gathered in three biotopes of the eastern shelf of the Bering Sea: open shelf (coastal zone), the harbor, and the salt lagoon of Saint Paul Island (Pribiof Islands). The following parameters of microplanktonic communities were analyzed: abundance, biomass, and production of autotrophic picoplankton (picoalgae and cyanobacteria); abundance, biomass, growth rate constant, and production of bacterioplankton; role of filiform bacteria in bacterioplankton; species composition of heterotrophic flagellates and ciliates, their abundance, and biomass. Growth rates and consumption rates of picoplankton and bacterioplankton by heterotrophic nano- and microplankton were estimated in the experiments using the dilution method. Temporal dynamics of all structural and functional parameters of microplankton were analyzed. The minor role of autotrophic picoplankton and significant role of bacterioplankton as well as heterotrophic nano- and microplankton in planktonic communities of studied biotopes during summer months was shown. During certain periods, bacterial biomass was as high as 50-65% of phytoplankton biomass, and production of bacteria was as high as 20-40% of primary production. In the middle of the season biomass of nano- and microheterotrophic organisms in different biotopes exceeded biomass of mesozooplankton 2-10 times. Average consumption of bacterial production by nano- and microplankton during the period of observations was 85-94%.

(Table 1, page 661) Average composition of fossil nodules from three localities studied in the Transdanubian Central Mountains of Hungary

Fossil manganese nodules and encrustations from seamount' and basin' localities in the Transdanubian Central Mountains of Hungary are lithologically, mineralogically and chemically similar to some modern marine ferromanganese oxide deposits, and show no evidence of postdepositional changes other than cementation. Five groups of deposits were encountered: Fe/Mn nodules, encrusted shells, pavements, stains, and Fe oxide encrusted intraclasts, the first three of which are specific to the 'seamount' environment and the last to the basins'. Optical and electron microprobe investigation of the samples shows them to exhibit many similarities with modern ferromanganese oxide deposits, and that many of the nodules are surrounded by a halo of dispersed ferromanganese oxides, strongly suggesting that they continued to accrete metals through the pore waters of unlithified sediments for a period after burial. By contrast, pavements which appear to have grown on hardgrounds at the sea floor show little or no evidence of derivation of metals from underlying sediments. Geochemical investigations on the deposits show the seamount' varieties to be closer in composition to most modern nodules and crusts than the basin' varieties, and that the latter are essentially manganese and trace-element-poor ferruginous deposits. Nevertheless, all can be more or less compositionally equated with modern ferromanganese oxide deposits forming in marginal Atlantic environments, which would be in accord with the proposed depositional environment of the Transdanubian Central Mountains based on other evidence.