In aquatic ecosystems, primary production (the transformation of inorganic materials and light into living matter by photosynthesis) is operated mainly by small, unicellular algae that float freely in the upper layers of oceans and lakes and are collectively called phytoplankton, see for an illustration the phytoplankters depicted in figure 1. Since phytoplankton need light, they are confined t...

[1] In the surface water of the winter Sargasso Sea, ‘‘dissolved’’ Fe concentrations (defined as iron that passes through a filter with an 0.4 micrometer diameter pore size) decrease with increasing latitude from 0.8 nM at 26 N to 0.2 nM at 31 N. It does not appear that this pattern can be explained solely by spatial variations of eolian Fe deposition. Vertical mixing, phytoplankton growth and ...

[1] Transformation processes in the euphotic and mesopelagic zones are of crucial importance to the biological pump and global elemental cycles. In this study, elemental stoichiometries and chemical compositions of particulate and dissolved organic matter (DOM) were investigated in the euphotic and upper mesopelagic zones of the North Pacific Subtropical Gyre. The distributions of bacterial bio...

A reverse-phase h.p.l.c. technique was used to estimate the concentration of chlorophyll b in phytoplankton cultures, fecal pellets of Calanuipacificus, and suspended paniculate matter from the Central North Pacific, Oregon coastal waters, and Dabob Bay (a temperate fjord in Puget Sound, WA, USA). The purpose was to assess the distribution of this pigment in the euphotic zone and its effect on ...

Protistan community structure was examined from 6 depths (1.5, 20, 42, 150, 500, 880 m) at a coastal ocean site in the San Pedro Channel, California. A total of 856 partial length 18S rDNA protistan sequences from the six clone libraries were analyzed to characterize diversity present at each depth. The sequences were grouped into a total of 259 Operational Taxonomic Units (OTUs) that were infe...

Sequestration of carbon by the marine biological pump depends on the processes that alter, remineralize, and preserve particulate organic carbon (POC) during transit to the deep ocean. Here, we present data collected from the Great Calcite Belt, a calcite-rich band across the Southern Ocean surface, to compare the transformation of POC in the euphotic and mesopelagic zones of the water column. ...

Microbial transformations are key processes in marine phosphorus cycling. In this study, we investigated the contribution of phototrophic and heterotrophic groups to phosphate (Pi) uptake fluxes in the euphotic zone of the lowPi Mediterranean Sea and estimated Pi uptake kinetic characteristics. Surface soluble reactive phosphorus (SRP) concentrations were in the range of 6–80 nmol L across the ...

We examined rates of N2 fixation from the surface to 2000 m depth in the Eastern Tropical South Pacific (ETSP) during El Niño (2010) and La Niña (2011). Replicated vertical profiles performed under oxygen-free conditions show that N2 fixation takes place both in euphotic and aphotic waters, with rates reaching 155 to 509 µmol N m(-2) d(-1) in 2010 and 24±14 to 118±87 µmol N m(-2) d(-1) in 2011....

Microbial biomass on suspended organic matter in seawater of the euphotic zone of Saanich Inlet was investigated. The viable microorganisms were measured by the glucose-uptake method. Microbial carbon on particulate organic matter in seawater was determined to be, on the average, 9.9 ,ug of C/liter, and there was a regression relationship as y = 0.0062 x 1.79 with an unbiased variance Vyx12= 0....

The critical depth concept was first recognized by Gran and Braarud (1935). During summer, in the Bay of Fundy, they observed an unexpected no bloom situation. Their interpretation was that high amounts of detritus of terrestrial origin caused too murky water and insufficient light for the tidallymixedphytoplankton. Almost 20 years later, thiswas elaboratedby Sverdrup (1953) into ahypothesis fo...