Importance of extracellular organic carbon production in the total primary production by tidal-flat diatoms in comparison to phytoplankton

Abstract

extracted with EDTA) to total primary production (TPP) were rneasured using "C-tracer to estirnate the ratio for each fraction of organic carbon photosynthetically produced by microphytobenthos and phytoplankton. TEOC for rn.icrophytobenthos ranged frorn 4 2 to 73% of TPP and was rnade up mostly of 14C-Colloidal-OC The TEOC/TPP for phytoplankton ranged frorn 1.5 to 220,). The ratio of I4C-EPS to I4C-CoUoidal-OC for rnicrophytobenthos was 41 to 53%, and for phytoplankton was 4.4 to 24%. Algal species in the transitional phase were used for experiments because microphytobenthos Nitzschia hybridaeformis most abundantly produced TEOC and EPS in the transitional phase during growth in experirnents studying the effect of the growth phase. By using EDTA for the extraction of extraceUular organic matter, it beComes clear that excretion of colloidal organic matter by rnicrophytobenthos has always been underestimated. These results suggest that the large arnount of TEOC containing EPS produced by microphytobenthos plays a more mportant role than secretion of phytoplankton as a source of organic carbon for heterotrophic organisms in the intertidal-flat ecosystem.

Effects of temperature on photosynthetic parameters and TEP production in eight species of marine microalgae

“…The slope values were, respectively, 0.067, 0.20 and 0.30 for Thalassiosira pseudonana, Skeletonema marinoi and Pseudonitzschia fraudulenta, which signifies that, respectively, 6.7, 20 and 30% of the photosynthetic carbon production was excreted as TEP. Estimations reported in the literature for benthic diatoms, which are known to produce large amounts of EPS, range from 30 to 73% of photosynthate being excreted, whereas for pelagic phytoplankton estimations range from 1.5 to 22% (Goto et al 1999, Smith & Underwood 2000. Because no relationships were found between photosynthetic production and TEP production for the other species, this percentage was estimated at T opt(ETR) at growth irradiance: 17.3% was calculated for Emiliania huxleyi, 6.8% for Isochrysis galbana, 15.9% for I. aff.…”

Uncoupling of bacterial production and flagellate grazing in aquatic sediments: a case study from an intertidal flat

“…Underwood et al 1995, Underwood & Smith 1998. These carbohydrates constitute a major part of the carbon fixed by microphytobenthos (Goto et al 1999, Smith & Underwood 2000 and may serve as an important substrate for bacteria (van Duyl et al 1999, Goto et al 2001). The strong relationship between bacterial production and the chl a content of the sediment therefore suggests that in our study bacterial production was mainly regulated by substrate supply.…”

Eutrophication in shallow coastal bays and lagoons: the role of plants in the coastal filter

“…A large part of benthic microalgal production is thought to pass through the macrofaunal grazing/deposit feeding chain (Asmus & Asmus 1985, Duarte & Cebrián 1996, Herman et al 2000, while part of it may also be channeled through the 'small food chain' consisting of micro-and meiofauna (Kuipers et al 1981, Sundbäck et al 1996, Pinckney et al 2003. However, since much of the organic matter is released as DOM by live and dead material (Goto et al 1999, Wolfstein et al 2002, processing of particulate organic matter by grazers and bacteria may only account for a portion of the total carbon fixed by benthic microalgae. During the initial stage of eutrophication, grazing of benthic microalgae by meiofauna can be expected to increase (Nilsson et al 1991), however, we still lack a clear understanding of how grazing modulates the benthic microalgal response to nutrient loading (Hillebrand & Kahlert 2002).…”