Journal
BIOGEOCHEMISTRY
Volume 96, Issue 1-3, Pages 87-100Publisher
SPRINGER
DOI: 10.1007/s10533-009-9346-4
Keywords
Allochthonous; Autochthonous; C:N ratios; Organic matter; Sediment resuspension; Stable isotopes
Funding
- Tom Conry and the City of Waco (Texas)
- Environmental Protection Agency through an ENSR, Inc. [102200]
- Texas Water Resources Institute [570251]
- Folmar and Gardner Graduate Student Research Grants through Baylor University Department of Biology
Ask authors/readers for more resources
Because allochthonous organic matter (OM) loading supplements autochthonous OM in supporting lake and reservoir food webs, C and N elemental and isotopic ratios of sedimenting particulate OM were measured during an annual cycle in a polymictic, eutrophic reservoir. Particulate organic C and N deposition rates were greatest during winter and lowest during spring. C: N ratios decreased through our study indicating that OM largely originated from allochthonous sources in winter and autochthonous sources thereafter. delta C-13 were influenced by C-4 plant signatures and became increasingly light from winter through autumn. delta N-15 indirectly recorded the OM source shift through nitrate utilization degree with maximum values occurring in May as nitrate concentrations decreased. Unlike relationships from stratified systems, delta C-13 decreased with increasing algal biomass. This relationship suggests that minimal inorganic C fixation relative to supplies maintained photosynthetic isotopic discrimination during productive periods. Water column mixing likely maintained adequate inorganic C concentrations in the photic zone. Alternatively, OM isotopic composition may have been influenced by changing dissolved inorganic nutrient pools in this rapidly flushed system. delta N-15 also recorded increased N-2 fixation as nitrate concentrations declined through autumn. Secondary sediment transport mechanisms strongly influenced OM delivery. Particulate organic C and N deposition rates were 3X greater near the sediment-water interface. Isotopic ratio mixing models suggested that river plume sedimentation, sediment resuspension, and horizontal advection influenced excess sediment deposition with individual mechanisms being more important seasonally. Our findings suggest that allochthonous OM loading and secondarily-transported OM seasonally supplement phytoplankton production in productive reservoirs.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available