Respiration rates of tropical Atlantic copepods from the Cape Verde Islands

Copepods were sampled at two sampling sites off the island of São Vicente, Cape Verde Archipelago, in spring (March/April) and early summer (May/June) of 2010. The two sampling sites were located in Mindelo Bay (16.90N, 25.01W; bottom depth 22 m) and around 8 km off the town of São Pedro (16.77N, 25.12W; bottom depth 800 m). Samples were collected on board the local fishing vessel 'Sinagoga' using a WP-2 net (Hydrobios, 0.26 m**2 mouth opening, 200 µm mesh size). The net was either applied as a driftnet, drifting for 10 min in 22 to 0 m depth below the surface, or it was towed vertically with a towing speed of 0.5 m/s**1. For stratified sampling, the net was deployed in repetitive hauls from 560 to 210 m, from 210 to 80 m, and from 80 to 0 m in March/April and from 600 to 300 m, 300 to 100 m, and 100 to 0 m in May/June. Additional depth-integrated hauls were conducted from 600-0 m or 500-0 m during both field campaigns. Respiration rates of epi- and mesopelagic calanoid copepods were measured in the land-based laboratory at the Instituto Nacional de Desenvolvimento das Pescas (INDP) in Mindelo. Oxygen consumption was measured non-invasively by optode respirometry at three different ambient temperatures (13, 18, and 23°C) with a 10-channel oxygen respirometer (Oxy-10 Mini, PreSens Precision Sensing GmbH, Regensburg, Germany). All experiments were run in darkness in temperature-controlled incubators (LMS Cooled Incubator Series 1A, Model 280) equipped with water baths to ensure constant temperatures throughout the experiments, tolerating a variation of ±1°C.

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%.

Composition of phosphorites from continental margins, seamounts, and islands

Behavior of molybdenum and manganese is studied in phosphorite samples from shelves, seamounts, and islands of the ocean. In shelf phosphorites molybdenum and manganese contents are 2-128 and 12-1915 ppm, respectively, while the Mo/Mn ratio varies from 0.004 to 4.5. Phosphorites from ocean seamounts impregnated with ferromanganese oxyhydroxides contain 0.84-14.5 ppm Mo and 0.1-17% Mn. The Mo/Mn ratio varies within 0.0008-0.004. Phosphate bearing ferromanganese crusts overlying seamount phosphorites contain 54-798 ppm Mo and 10-20% Mn; the Mo/Mn ratio varies within 0.002-0.005. Corresponding values for most island phosphorites are 0.44-11.2 ppm, 27-287 ppm, and 0.008-0.20. Phosphorites from reduced environment are characterized by relative enrichment in Mo and depletion in Mn, whereas the Mo/Mn ratio reaches maximum values. The ratio decreases with transition to suboxic and oxic conditions. Molybdenum content in recent shelf sediments is commonly higher than that in authigenic phosphorites from these sediments. Recent phosphorite nodules from the Namibian shelf become depleted in Mo and Mn during their lithification, but Pliocene-Pleistocene nodules of similar composition and origin from the same region are enriched in Mo and characterized by variable Mn content. Higher Mo contents in phosphate bearing ferromanganese crusts result from coprecipitation of Mo and Mn from seawater. Unweathered phosphorites on continents and phosphorites from ocean shelves are largely enriched in Mo with the Mo/Mn ratio varying from 0.01 to 1.0. This is an evidence of their formation in reduced conditions.