气候变化领域集成服务门户

To investigate the relative importance of microphytobenthos (MPB) oxygen (O-2) production on a river-dominated shelf, we made sediment core incubation measurements of MPB O-2 production and sediment O-2 consumption, and compared these to water-column measures of primary production and respiration during one spring and two summer cruises. Sites were located across a light attenuation (Kd) gradient on the inner Louisiana shelf (<25 m depth) with three sites on the eastern shelf and one site on the western shelf. MPB production rates were highest (range = 0.7-33.4 mmol O-2 m(-2) d(-1)) at the western site where light attenuation was lowest (range = 0.13-0.16 m(-1)). Near the river plumes, where Kd was higher (range = 0.17-0.64 m(-1)), MPB production was lower (range = 0-2.0 mmol m(-2) d(-1)) MPB production influenced the magnitude and direction of sediment O-2 exchanges at the western site and was observed to be a function of light availability. Overall, though, in comparison with integrated bottom layer production and respiration rates, MPB photosynthetic O-2 production as a percentage was small (range of means = 0%-2%) at the eastern shelf sites. At the western site, MPB production was larger, and more variable, 39% (SE 34%) of bottom layer O-2 production. Though based on a small data set, results suggest distinct differences between eastern and western shelf Kd and MPB contributions to bottom water O-2 due to proximity to the freshwater discharges of the Mississippi and Atchafalaya rivers.