Seasonal and interannual patterns of intertidalmicrophytobenthos in combination with laboratoryand areal production estimates
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From April 1994 to December 1997, we studied the microphytobenthic assemblages in surface(0 to 0.5 cm) and subsurface (0.5 to 2 cm) sediments at spring low tide along a transect of 5 stationsin an estuarine sandflat of the Seto Inland Sea, Japan. At the innermost sampling station, microphytobenthosbiomass (chl a) was also investigated in a vertical profile to 10 cm depth from December 1994to April 1996. The chl a contents at the 2 uppermost layers were well correlated with each other, with amean decrease of 34% from the surface to subsurface layer. Chl a tended to decrease rapidly throughthe vertical profile and was reduced to 3.2 ± 1.4% SD in the 9 to 10 cm layer. There was a progressive decreasein the chl a content every year in fall and the occurrence of major peaks in early spring and/orsummer. This was accompanied by a significant increase in microphytobenthos biomass from 1994 to1995 and from 1995 to both 1996 and 1997. The microphytobenthos biomass in surface sediments (meanof 5 stations) ranged between 27.7 (October 1994) and 120 mg chl a m–2 (July 1997), or between 3.9(November 1994) and 20.3 μg chl a g–1 dry wt (July 1996). Annual mean (1995 to 1997) biomass was72.3 ± 27.1 mg chl am–2 and 11.0 ± 4.3 μg chl a g–1 dry wt. These values rank in the mid-upper range ofmicrophytobenthic biomass for intertidal sediments. In addition to the field investigations, we conductedlaboratory experiments on a dominant diatom species, Navicula sp. The photosynthetic rate of Naviculasp. was saturated at a light intensity of 165 μE m–2 s–1 at 21°C. No photoinibition was found at higherlight intensities up to 400 μE m–2 s–1. The relationship between temperature and photosynthetic rate waspositive and linear within a temperature range between 10 and 35°C at 55 μE m–2 s–1. Areal 'potential'primary production of microphytobenthos was between 0.32 (December 1994) and 3.0 gC m–2 d–1 (July1997), with an annual mean of 1.2 gC m–2 d–1. Uni- (summer) or bi-modal (spring and summer) peaks ofmicrophytobenthos biomass and primary production highlighted a marked interannual variability.Marked seasonal patterns were also recognizable, with primary production of microphytobenthossignificantly higher both in spring and summer than in winter and fall.
- Inter-Researchの論文
- 2003-03-10
Inter-Research | 論文
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