There has been an explosion of research on marine microbial foodweb processes in the past decade. Today it is widely accepted that about 50% of the primary production in marine and fresh water is processed by bacteria each day (Williams, 1981; Cole et al., 1988). This striking finding was stimulated, as others have noted, by the introduction of convenient methods for the estimation of microbial biomass and activities in natural waters. Hobbie et al. (1977) and Watson et al. (1977) demonstrated conclusively that bacterial populations in the sea were large. By 1980, in addition to the pioneering and prescient work by Sorokin (e.g., Sorokin, 1971, 1973), reports of bacterial production measurements had begun to emerge (Sieburth et al., 1977; Karl, 1979; Larsson and Hagstrom, 1979; Fuhrman and Azam, 1980). Brock (1971) and Sieburth (1977) wrote early reviews on the subject, and Pomeroy (1974) introduced the importance of marine microbial processes to a large audience. In this chapter we review recent research on bacterial production in the ocean. The emphasis is on the open sea, but we will also discuss other marine habitats, partly because there are still few comprehensive studies of oceanic bacterial production. There is an equally large and rapidly growing literature on bacterial production in fresh waters (Cole et al., 1988; Currie, 1990) which deserves a review of its own, as well as comparison with the marine findings (Hobbie, 1988). We will not review related work in sediments, nor for the most part, related work on bacteriovores.

Oceanic Bacterial Production

Active heterotrophic bacterial communities exist in all marine environments, and although their growth rates or respiratory rates may be limited by the interaction of low substrate concentrations with temperatures near their lower limit for growth, temperature and substrate con- centrations are rarely considered together as limiting factors. Moreover, attempts to evaluate meta- bolic limits by both temperature and substrate concentration have sometimes led to confusing con- clusions, because, while we can measure dissolved organic carbon (DOC) concentrations in natural waters, much of it is not readily available to heterotrophic bacteria. In spite of this procedural limita- tion, it can be helpful to regard temperature and substrate concentration as potential limiting factors that interact. In temperate ocean surface waters and estuarine waters, where bacterial growth is often reduced in winter, growth and respiration may be increased experimentally either by raising the tem- perature or by increasing organic substrate concentrations, providing indirect evidence that the lim- itation is an effect of temperature on substrate uptake or assimilation. Experimental work with bac- terial isolates also has shown a temperature-substrate interaction. In permanently cold polar waters, most heterotrophic bacteria appear to be living at temperatures well below their optima for growth. Nevertheless, bacteria in permanently cold surface waters can achieve activity rates in summer that are as high as those in temperate waters. In sea ice, rates of bacterial production are most often low, even though concentrations of substrates, including free amino acids, are sometimes much higher than they are in seawater. This suggests that at sea ice temperatures heterotrophic bacteria have low- ered ability to take up or utilize organic substrates.

/pdf/temperature-and-substrates-as-interactive-limiting-factors-2a3dfc7mws.pdf

Temperature and substrates as interactive limiting factors for marine heterotrophic bacteria

The sea ice does not only determine the ecology of ice biota, but it also influences the pelagic systems under the ice cover and at ice edges. In this paper, new estimates of Arctic and Antarctic production of biogenic carbon are derived, and differences as well as similarities between the two oceans are examined. In ice-covered seas, high algal concentrations (blooms) occur in association with several types of conditions. Blooms often lead to high sedimentation of intact cells and faecal pellets. In addition to ice-related blooms, there is progressive accumulation of organic matter in Arctic multi-year ice, whose fate may potentially be similar to that of blooms. A fraction of the carbon fixed by microalgae that grow in sea ice or in relation to it is exported out of the production zone. This includes particulate material sinking out of the euphotic zone, and also material passed on to the food web. Pathways through which ice algal production does reach various components of the pelagic and benthic food webs, and through them such top predators as marine mammals and birds, are discussed. Concerning global climate change and biogeochemical fluxes of carbon, not all export pathways from the euphotic zone result in the sequestration of carbon for periods of hundreds of years or more. This is because various processes, that take place in both the ice and the water column, contribute to mineralize organic carbon into CO2 before it becomes sequestered. Processes that favour the production and accumulation of biogenic carbon as well as its export to deep waters and sequestration are discussed, together with those that influence mineralization in the upper ice-covered ocean.

/pdf/ecology-of-sea-ice-biota-2-global-significance-9a3z9vb36u.pdf

Ecology of sea ice biota 2. Global significance.

Climatological data on the distribution of surface pigment fields in the entire southern ocean over a seasonal cycle are examined. The occurrence of intense phytoplankton blooms during austral summer months and during other seasons in different regions is identified and analyzed. The highest pigment concentrations are observed at high latitudes and over regions with water depths usually less than 600 m. Basin-scale pigment distribution shows a slightly asymmetric pattern of enhanced pigment concentrations about Antarctica, with enhanced concentrations extending to lower latitudes in the Atlantic and Indian sectors than in the Pacific sector. A general increase in pigment concentrations is evident from the low latitudes toward the Antarctic circumpolar region. Spatial relationships between pigment and archived geophysical data reveal significant correlation between pigment distributions and both bathymetry and wind stress, while general hemispheric scale patterns of pigment distributions are most coherent with the geostrophic flow of the Antarctic Circumpolar Current.

Coastal zone color scanner pigment concentrations in the Southern Ocean and relationships to geophysical surface features

The influence of oceanographic processes on pelagic-benthic coupling in polar regions: A benthic perspective

Bacterioplankton in the marginal ice zone of the Weddell Sea: biomass, production and metabolic activities during austral autumn

https://www.int-res.com/articles/meps/63/m063p239.pdf

G.F. Cota

Papers

Bacterioplankton in the marginal ice zone of the Weddell Sea: biomass, production and metabolic activities during austral autumn

Distribution and activity of bacterio-plankton in the marginal ice zone of the Weddell-Scotia Sea during austral spring