Marine microbial food webs

Jumars, P., J. Deming, P. Hill, L. Karp-Boss, P. L. Yager, and W. Dade. 1993. Physical constraints on marine osmotrophy in an optimal foraging context. Marine Microbial Food Webs 7 121-161. 

Williams, P. J. L. 1990. The importance of losses during microbial growth Commentary on the physiology, measurement, and ecology of the release of dissolved organic material. Marine Microbial Food Webs 4 175-206. 

The microbial loop concept has been the prevailing paradigm for marine microbial food webs for two decades and has stimulated work on DOM sources and composition, rates of biomass production, transfer efficiencies, and respiratory losses (Benner, 1998 del Giorgio and Cole, 2000 Ducklow, 2000 Williams, 2000). The only major modification has arisen from new information on the abundance and ecology of viruses (Wilhelm and Suttle, 1999 Fuhrman, 1999, 2000). 

Sanders, R.W. and Wickham, S.A. (1993) Planktonic protozoa and metazoa predation, food quality and population control. Marine Microbial Food Webs, 7, 197-223. 

The second pattern evident in Table II is that the photochemically mediated transfer of carbon into the microbial food web is more pronounced for deep-water marine DOM than for surface water marine DOM. In two studies that explicitly compared relative photoreactivity of surface and deep samples, the biological lability of deep-water DOM was consistently greater after exposure to sunlight, whereas surface waters typically... 

Peduzzi, P., and G. J. Herndl. 1991. Decomposition and significance of seagrass leaf litter (Cymodocea modosa) for the microbial food web in coastal waters (Gulf of Trieste, Northern Adriatic Sea). Marine Ecology Progress Series 71 163—174. 

The production of DMS is almost exclusively through biogenic processes and shows strong seasonal and latitudinal variation (Kettle et al. 1999). DMS mainly results from the enzymatic cleavage of DMSP, a compound that is produced in several groups of marine phytoplankton. A complex network of production and consumption pathways of both DMSP and DMS involves most of the microbial food web (Fig. 1) and determines the concentration of... 

DMS(P)] quotas and microbial yields is still too limited. Such insights are needed to inform laboratory and field studies and aid us in the development of more robust DMS(P)-modules within ecosystem models. During the past decade, many excellent reviews have been written on several aspects of the marine sulphur cycle. One of the emerging pictures is that this cycle is not only of interest for global climate, but that DMS and DMSP are compounds which are central to the microbial food web in their own right. The purpose of this review is not so much to reiterate these reviews, but rather to use pertinent information from them in an attempt to assist the development of parameterisations for DMSP and DMS modelling. 

The chemical half-life of DMSP in seawater is >8 years (Dacey and Blough 1987), which results in high abiotic stability under natural conditions (moderate temperatures and pH). Therefore, most of the DMSP removal is through enzymatic processes. In the microbial food web, dissolved DMSP has many fates and several recent reviews on the microbial pathways and involved mechanisms have been published (Bentley and Chasteen 2004 Kiene et al. 2000 Lomans et al. 2002 Yoch 2002). They all show that DMSP can be readily used in a complex network of enzymatic conversions. This versatility indicates that this single compound is of major importance for the nutrition of the bacterial community. Indeed, several studies have shown that DMSP alone can contribute 1 to 15% of the total bacterial carbon demand in surface waters. Moreover, DMSP assimilation can satisfy most, if not all the, sulphur demand of marine bacteria (Kiene and Linn 2000 Simo et al. 2002 Zubkov et al. 2001). Since the focal point of this section is the quantification of DMSP removal, only the overall effects of the main pathways originating from DMSP (Fig. 1) will be discussed here. 

Figure 16.3 Microbial food web processes sustain the marine N-cycle in the North Pacific trades biome. Shown are (A) a schematic view of the various sources, transformations and sinks for key N pools and...

Epstein, S. S. (1997). Microbial food webs in marine sediments.1. Trophic interactions and grazing rates in two tidal flat communities. Microb. Ecol. 34, 188-198. 

Pile, A. J. (1996). The role of microbial food webs in benthic-pelagic coupbng in freshwater and marine ecosystems, Ph.D. dissertation. School of Marine Science. The College of WiUiam and Mary, VA. 

Nagata, T., and Kirchman, D. L. (1997). Roles of submicron particles and colloids in microbial food webs and biogeochemical cycles within marine environments. In Advanced Microbial Ecology Qones, Ed.). Plenum Press, New York. pp. 81-103. 

Katechakis, A., Stibor, H., Sommer, U. and Hansen, T. (2002) Changes in the phytoplankton community and microbial food web of Blanes Bay (Catalan Sea, NW Mediterranean) under prolonged grazing pressure by doliolids (Tunicata), cladocerans or copepods (Crustacea). Marine Ecology Progress Series, 234, 55-69. 

The inefficiency of microbial heterotrophy does have a side benefit as it enhances nutrient remineralization rates. This serves to increase the availability of inorganic nitrogen and phosphorus for the photoautotrophs. The multiple roles of bacteria in the marine food web were shown in Figure 23.2, with the component of the food web controlled by the algal herbivores depicted on the left side and the microbial loop on the right. The viral shunt acts on both pathways. 

Nutrient pollution has contributed to other notable disturbances in the structure of marine food webs. These include (1) bioinvasions of macroalgae and microbial mats... 

Murray, A. G., and P. M. Eldridge. 1994. Marine viral ecology Incorporation of bacteriophage into the microbial planktonic food web paradigm. Journal of Plankton Research 16 627-641. 

Decho, A. W. 1990. Microbial exopolymer secretions in ocean environments their role(s) in food webs and marine processes. Oceanography and Marine Biology Annual Review 28 73-153. 

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