PubMed · 13615800
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S VISCO. 1958. [Nutritional problems in countries bordering the Mediterranean sea].. https://pubmed.ncbi.nlm.nih.gov/13615800/
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Nitrogen fixation, nitrate assimilation and primary production ((13)C/(15)N method) were investigated during one year and half in the northwestern Mediterranean Sea. Nitrogen fixation was detectable all over the year with rates ranged from 2 to 17 nmol N l(-1) d(-1)(d). Highest values being obtained during spring associated with the phytoplankton bloom. High rates (4-8 nmol N l(-1) d(-1)(d)) were also measured during summer, when primary productivity was very low. Then, diazotrophy process supplies significant new nitrogen during summer oligotrophic periods. This new nitrogen input can balance the annual nitrogen biogeochemical budget in the Mediterranean Sea and should explain the high nitrate/phosphate ratio observed in deep waters.
Nutrient concentrations (orthophosphate, orthosilicate and dissolved inorganic nitrogen-DIN) were measured on three transects in the northern Adriatic approximately monthly in the period June 1999-July 2002. The net nutrient transports across the three transects were estimated from these concentration values and calculated water fluxes [Grilli F, Paschini E, Russo A, Precali R, Supić N. Circulation and horizontal fluxes in the Northern Adriatic Sea in the period June 1999_July 2002. Part I: geostrophic circulation and current measurement. Sci Total Environ 2005-this issue], with the aim to verify their possible role in the mucilage phenomenon. The nutrient transports in the northern Adriatic were very variable, seasonally and from year to year, both in intensity and direction. Some differences were noticed also among the nutrient species. At the northernmost transect Po Delta-Rovinj minimal values and variable directions were recorded, probably due to the prevailing of eastward transversal transports, observed already in late winter, and generally dominant in spring and summer. Northward transport was often measured at the central transect Cesenatico-Cape Kamenjak, particularly in spring 2000 and 2002, and summer 2001, as well as for only DIN in summer 1999. In contrast, southward directions prevailed at the southernmost transect Senigallia-Susak Island. In October significant southward transports occurred at all transects and for all nutrients, particularly strong in 2000, when exceptionally high Po River discharges occurred, and the Western Adriatic Current (WAC) was well developed. However, the nutrient transports in the upper water column were low or northwards at both transect Cesenatico-Cape Kamenjak and Senigallia-Susak Island in June and July 2000, 2001, and 2002, when the mucilage phenomenon developed, but were opposite in 1999, a year without events. The results suggest that high variations of nutrient fluxes and their ratios, in conditions of reduced water dynamics, are essential for the development of the phenomenon, rather than the absolute amounts of the nutrient inputs.
A Gram-negative, slightly halophilic, non-pigmented, strictly aerobic, chemo-organotrophic bacterium was isolated from sea water off the western Mediterranean coast near Valencia (Spain). This strain was able to grow on several organic acids and amino acids added to a minimal medium as carbon sources, but used few carbohydrates or yielded slight growth when sugars were used. Phylogenetic analysis based on an almost complete 16S rRNA gene sequence revealed that strain XSM19T was a member of the Roseobacter group within the 'Alphaproteobacteria', with its closest phylogenetic neighbour being Ruegeria gelatinovorans (97.6 % sequence similarity). Following a polyphasic approach, it was concluded that strain XSM19T represents a new genus and novel species, for which the name Thalassobius mediterraneus sp. nov. is proposed. The type strain is XSM19T (=CECT 5383T=CIP 108400T=CCUG 49438T). It is also proposed that R. gelatinovorans (Rüger & Höfle 1992) Uchino et al. 1999 is reclassified as Thalassobius gelatinovorus comb. nov.