Free Content The influence of deposit-feeding on chlorophyll-a degradation in coastal marine sediments

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Abstract:

To determine how macrofaunal activity affects rates and mechanisms of Chlorophyll-a (Chl-a) decomposition, we measured Chl-a concentrations during laboratory incubations of surface sediment with varying abundances of a subsurface deposit-feeder, Yoldia limatula. Decomposition patterns of Chl-a in sediment cores with and without a layer of algal-enriched sediment added to the surface were compared. Decomposition rate constants, kd, were calculated from the loss of reactive Chl-a and further quantified using a nonsteady state, depth-dependent, reaction-diffusion model. Values of kd decreased approximately exponentially with depth and were directly proportional to the number of Yoldia present. Yoldia increased the kd of both natural sedimentary Chl-a and algal enriched Chl-a in the upper 2 cm by up to 5.7×. Surface sediment porosity, penetration depths of a conservative tracer of diffusion (Br-), and oxidized metabolic substrates (e.g. Fe(III)) all increased significantly in the presence of Yoldia. Macrofaunal bioturbation increased the importance of suboxic degradation pathways. These experiments demonstrated that organic compounds from a single source can have a continuum of degradation rate constants as a function of biogenically determined environmental conditions (Chl-a kd ˜ 0.0043-0.20 d-1). In particular, Chl-a can have a continuum of kd values related to redox conditions, transport, and macrofauna abundance as a function of depth.

Document Type: Research Article

DOI: http://dx.doi.org/10.1357/002224000321511052

Publication date: July 1, 2000

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  • The Journal of Marine Research publishes peer-reviewed research articles covering a broad array of topics in physical, biological and chemical oceanography. Articles that deal with processes, as well as those that report significant observations, are welcome. In the area of biology, studies involving coupling between ecological and physical processes are preferred over those that report systematics. Authors benefit from thorough reviews of their manuscripts, where an attempt is made to maximize clarity. The time between submission and publication is kept to a minimum; there is no page charge.
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