caa a22 4500 465792723 CHVBK 20180323112029.0 cr unu---uuuuu 170327e19901201xx s 000 0 eng 10.2307/1351784 doi (NATIONALLICENCE)springer-10.2307/1351784 Marsh-water column interactions in two Louisiana estuaries. I. Sediment dynamics [Elektronische Daten] [Daniel Childers, John Day] Throughflow marsh flumes were used to measure total sediment exchanges (TSS) between the marshes and water column of two Louisiana estuaries. One, the Barataria Basin estuary, is isolated from significant riverine sediment input. There were significant (p<0.05) imports of 33.9 to 443 mg TSS m−2 h−1 at the Barataria Basin brackish marsh (BM) site. The Barataria Basin saltmarsh (SM) site exported TSS in two summer samplings, but significant uptake was measured in April (166 mg m−2 h−1) and November (45 mg m−2 h−1) during a winter frontal passage event. The other estuary, Fourleague Bay, receives large sediment inputs from the Atchafalaya River, and TSS imports of 22.5 to 118.5 mg m−2 h−1 were measured at the BM site here. We calculated sediment accumulation from fluxes quantified in marsh flumes using site-specific sedimentological data and flooding regimes at each site. Water level records from May 1987 to April 1989 showed an extended period of unusually low flooding frequencies. As a result, calculated accretion rates were low, with monthly rates of 0.02 to 0.11 mm and −0.06 to 0.06 mm at the Barataria BM and SM sites, respectively, and −0.18 to 0.08 mm at the Fourleague Bay marsh flume site. Actual net sediment deposition, determined by feldspar marker horizon analysis, was 0.7-1.6 mm mo−1 at the Barataria SM and 0.2-1.3 mm mo−1 at the Fourleague Bay BM. Even the highest calculated accretion rates, based on flume measurements, were half to one order of magnitude lower than actual measured sediment deposition. This discrepancy was probably because: 1) most sedimentation occurs during episodic events, such as Hurricane Gilbert in September 1988, which deposited 3.5-15.5 mm of sediment on the Barataria Basin saltmarsh, or 2) most vertical accretion in Louisiana marshes occurs via deposition of in situ organic matter rather than by influx of allochthonous sediment. Our results affirm the variability of short-term sediment transport and depositional processes, the close coupling of meteorologic forcing and flooding regime to sediment dynamics, and the importance of understanding these interrelated mechanisms in the context of longer term measurements. Estuarine Research Federation, 1990 Childers Daniel Coastal Ecology Institute Department of Marine Sciences Center for Wetland Resources, Louisiana State University, 70803-7503, Baton Rouge, Louisiana aut Day John Coastal Ecology Institute Department of Marine Sciences Center for Wetland Resources, Louisiana State University, 70803-7503, Baton Rouge, Louisiana aut Estuaries Springer-Verlag 13/4(1990-12-01), 393-403 0160-8347 13:4<393 1990 13 12237 https://doi.org/10.2307/1351784 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.2307/1351784 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Childers Daniel Coastal Ecology Institute Department of Marine Sciences Center for Wetland Resources, Louisiana State University, 70803-7503, Baton Rouge, Louisiana aut NATIONALLICENCE 700 1- Day John Coastal Ecology Institute Department of Marine Sciences Center for Wetland Resources, Louisiana State University, 70803-7503, Baton Rouge, Louisiana aut NATIONALLICENCE 773 0- Estuaries Springer-Verlag 13/4(1990-12-01), 393-403 0160-8347 13:4<393 1990 13 12237 Metadata rights reserved Springer special CC-BY-NC licence nationallicence SWISSBIB 465792723 BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer