Scientia Marina 

About: Scientia Marina is an academic journal published by Spanish National Research Council. The journal publishes majorly in the area(s): Population & Mediterranean sea. It has an ISSN identifier of 0214-8358. It is also open access. Over the lifetime, 2391 publications have been published receiving 61620 citations.

Using flow cytometry for counting natural planktonic bacteria and understanding the structure of planktonic bacterial communities

Abstract: Flow cytometry is rapidly becoming a routine methodology in aquatic microbial ecology. The combination of simple to use bench-top flow cytometers and highly fluorescent nucleic acid stains allows fast and easy determination of microbe abundance in the plankton of lakes and oceans. The different dyes and protocols used to stain and count planktonic bacteria as well as the equipment in use are reviewed, with special attention to some of the problems encountered in daily routine practice such as fixation, staining and absolute counting. One of the main advantages of flow cytometry over epifluorescence microscopy is the ability to obtain cell-specific measurements in large numbers of cells with limited effort. We discuss how this characteristic has been used for differentiating photosynthetic from non-photosynthetic prokaryotes, for measuring bacterial cell size and nucleic acid content, and for estimating the relative activity and physiological state of each cell. We also describe how some of the flow cytometrically obtained data can be used to characterize the role of microbes on carbon cycling in the aquatic environment and we prospect the likely avenues of progress in the study of planktonic prokaryotes through the use of flow cytometry.

The oceanic fixed nitrogen and nitrous oxide budgets: Moving targets as we enter the anthropocene?*

Abstract: New data force us to raise previous estimates of oceanic denitrification. Our revised estimate of ~ 450 Tg N yr -1 (Tg = 10 12 g) produces an oceanic fixed N budget with a large deficit (~ 200 Tg N yr -1 ) that can be explained only by positing an ocean that has deviated far from a steady-state, the need for a major upwards revision of fixed N inputs, particularly nitrogen fixation, or both. Oceanic denitrification can be significantly altered by small re-distributions of carbon and dissolved oxygen. Since fixed N is a limiting nutrient, uncompensated changes in denitrification affect the ocean´s ability to sequester atmospheric CO 2 via the "biological pump". We have also had to modify our concepts of the oceanic N 2 O regime to take better account of the extremely high N 2 O saturations that can arise in productive, low oxygen waters. Recent results from the western Indian Shelf during a period when hypoxic, suboxic and anoxic waters were present produced a maximum surface N 2 O saturation of > 8000%, a likely consequence of "stop and go" denitrification. The sensitivity of N 2 O production and consumption to small changes in the oceanic dissolved oxygen distribution and to the "spin-up" phase of denitrification suggests that the oceanic source term for N 2 O could change rapidly.

The general specifications of the MEDITS surveys

Abstract: An international bottom trawl survey was designed from a European Commission´s initiative to produce biological data on the demersal resources in the Mediterranean Sea. Nine Mediterranean countries are associated in the programme, which covers all the trawlable areas along their coasts from 10 to 800 m depth. From 1994 to 2000, one survey was carried out each year, applying common standardized protocols. Seven yearly surveys have therefore been done, with a total of 7,500 stations prospected. This paper presents the methods adopted to carry out the surveys.

Fronts and eddies as key structures in the habitat of marine fish larvae: opportunity, adaptive response and competitive advantage

Abstract: Surface fronts and mesoscale eddies are two classes of ocean structures that engender significant pattern in the habitats of marine organisms. Both are sites where mechanical energy of the physical system may be accessible for augmenting trophic energy available to biological organisms. Accordingly, they may offer opportunities for exceptional local productivity and growth of species particularly adapted to excelling in such highly-productive rapid-growth/high-mortality situations. The major relevant physical mechanisms involved are presented. A widespread attraction of many types of fish to floating objects drifting in the ocean is cited as an apparent adaptive response to the desirable aspects of surface fronts. An apparent contrary tendency for certain important marine fish species to be particularly successful in relatively poorly productive situations, where slower growth may be offset by much lower early life predation mortality, is also noted. Competing tradeoffs between (1) early life nutrition and resulting growth, and (2) mortality of early stages due to predation are suggested. These tradeoffs are posed and illustrated via a “predator pit” conceptual framework. Illustrations of the evident reproductive habitat choices of several populations of large temperate tunas are briefly presented. It is concluded that the time may have come for a general shift in the approach of at-sea fish larval ecological investigations from the conventional focus on associations with environmental properties on a “macro” scale to intensive investigations of the real-time progressions of linked physical-biological interactions occurring on a “meso” (and smaller) scale.

Primary production in the northwestern Mediterranean

Abstract: SUMMARY: The Mediterranean is, globally considered, an oligotrophic sea. However, in spite of its small extension, it presents considerable heterogeneity and, specially in the Western sub-basin, a number of hydrographic features contribute to increase its potential fertility. Phosphorus appears to be the most important limiting nutrient in the Mediterranean, although it is closely followed by nitrogen in this limiting role. The basic mechanisms of nutrient enrichment in the Mediterranean photic zone include vertical mixing in winter, coastal upwelling and the input of Atlantic waters through Gibraltar. River runoff is important, specially in the Western basin. One of the main causes of Mediterranean oligotrophy may be the water exchange at Gibraltar. The Mediterranean losses deep, relatively nutrient-rich water to the Atlantic through the Gibraltar Strait and receives an excess of superficial, nutrient-poor Atlantic water which compensates for the deep water outflow and the evaporation losses in the Mediterranean basin. However, the water flows at Gibraltar contribute to the fertility of the area through several mechanisms. One of them is due to the relatively shallow depth of the Gibraltar sill; in this zone, the entering waters become partially mixed with the richer outflowing waters and entrain additional nutrients into the Alboran Sea. Another enrichment mechanism is linked with the gyres induced by the Atlantic jet in the Alboran Sea and the associated upwelling near the coast of the Spanish side. Besides the general fertilization mechanisms mentioned above, the Western Mediterranean presents a series of mesoscale structures which represent sites of enhanced nutrient inputs to the photic layers. These structures include the shelf-slope fronts along the continental and insular coasts and the central divergence zones of the Liguro-Provencal and Catalano-Balearic Seas, which appear to be parts of a continuum. The relevance of some of these features for plankton production remained unrecognized until the last decades. In the vertical dimension, it has become apparent that the deep chlorophyll maxima, typical of the stratification season in the Mediterranean and other oligotrophic marine areas, are sites in which significant pulses of new production may take place, specially above the divergences, in which the nutrient-rich waters are closer to the surface. The occurrence of several mechanisms of fertilization, responding in different ways to environmental forcing, helps to enhance primary production levels throughout parts of the year including the stratification period. In the Catalan Sea, for example, the shelf/slope front and the central divergence located mid-way between the continental coast and the Balearic Islands appear to vary their relative contributions from spring to summer, with the divergence becoming more important later during the stratification period. The optimisation of sampling strategies linked to a better knowledge of the productive hydrographic structures and the improvement of methodology have lead to higher estimates of the primary production in the northwestern Mediterranean than where previously accepted. However, even with these increased estimates, the present level of total fish catches appears to be close to what could be the predicted limit according to some simple assumptions.