B vitamins are some of the most commonly required biochemical cofactors in living systems. Therefore, cellular metabolism of marine vitamin-requiring (auxotrophic) phytoplankton and bacteria would likely be significantly compromised if B vitamins (thiamin B 1 , riboflavin B 2 , pyridoxine B 6 , biotin B 7 , and cobalamin B 12 ) were unavailable. However, the factors controlling the synthesis, ambient concentrations, and uptake of these key organic compounds in the marine environment are still not well understood. Here, we report vertical distributions of five B vitamins (and the amino acid methionine) measured simultaneously along a latitudinal gradient through the contrasting oceanographic regimes of the southern California-Baja California coast in the Northeast Pacific margin. Although vitamin concentrations ranged from below the detection limits of our technique to 30 pM for B 2 and B 12 and to ∼500 pM for B 1 , B 6 , and B 7 , each vitamin showed a different geographical and depth distribution. Vitamin concentrations were independent of each other and of inorganic nutrient levels, enriched primarily in the upper mesopelagic zone (depth of 100-300 m), and associated with water mass origin. Moreover, vitamin levels were below our detection limits (ranging from ≤0.18 pM for B 12 to ≤0.81 pM for B 1 ) in extensive areas (100s of kilometers) of the coastal ocean, and thus may exert important constraints on the taxonomic composition of phytoplankton communities, and potentially also on rates of primary production and carbon sequestration.T he evolution of organic catalysts (enzymes and coenzymes) that accelerated biochemical reactions by orders of magnitude compared with inorganic catalysis alone was a critical step for the emergence of major cellular processes (1). Well-known coenzyme molecules include the B vitamins, which catalyze many important biochemical reactions in central metabolism (2). Those reactions include rearrangement-reduction of C-C bonds and methyl transfer reactions, synthesis of deoxyribose/fatty acids/ carbohydrates/branched-chain amino acids, electron transfer in oxidation-reduction reactions, and CO 2 fixation (2). This means that without an exogenous source of B vitamins, central metabolism in vitamin-requiring (auxotrophic) organisms would be compromised and the cells would not be able to grow, a situation that could have great bearing on many biological processes in the ocean, including the biological carbon pump.In the marine environment, vitamins have been implicated as important factors regulating the growth and succession of phytoplankton species (3). This inference was based on the fact that many species of eukaryotic phytoplankton require vitamins when they are cultured in the laboratory (3-7). Although it was thought that marine prokaryotes were the major producers of vitamins in the sea (4), genomic data indicate that it is common for both eukaryotic phytoplankton and bacterioplankton to be auxotrophic for at least one B vitamin, mainly because they lack the complete biosynthetic...

In order to establish the status of metal contamination in surface waters in the coastal ocean off Los Angeles, California, we determined their dissolved and particulate pools and compared them with levels reported in the 1970s prior the implementation of the Clean Water Act. These measurements revealed a significant reduction in particulate toxic metal concentrations in the last 33 years with decreases of ∼100-fold for Pb and ∼400-fold for Cu and Cd. Despite these reductions, the source of particulate metals appears to be primarily anthropogenic as enrichment factors were orders of magnitude above what is considered background crustal levels. Overall, dissolved trace metal concentrations in the Los Angeles coastal waters were remarkably low with values in the same range as those measured in a pristine coastal environment off Mexico's Baja California peninsula. In order to estimate the impact of metal contamination on regional phytoplankton, the internalization rate of trace metals in a locally isolated phytoplankton model organism (Synechococcus sp. CC9311) was also determined showing a rapid internalization (in the order of a few hours) for many trace metals (e.g., Ag, Cd, Cu, Pb) suggesting that those metals could potentially be incorporated into the local food webs.