278 Understanding Temporal Dynamics in Hydrogeochemistry and Sedimentary Processes in Estuarine Environments
This session explores temporal changes in estuarine environments with respect to water chemistry and sediment inputs. Effects of evolving physiochemical properties and isotopic composition of water, as well as the geochemical attributes of sediments on the environment will be presented.
Wednesday, 22 October 2025
1:30 PM - 5:30 PM
HBGCC, 213AB
Understanding the spatial and temporal dynamics of the Amazon estuary and the Guianas mudbanks
Paper number: 278-8
Program: Technical Sessions
Time: 3:30 PM – 3:50 PM
Authors
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Valier GalyWoods Hole Oceanographic Institution, Woods Hole, MA
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José MouraUniversidade Federal de Oueste de Pará, Santarém, Pará
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Aline ValerioInstituão Nacional de Pesquisas Espaciais, São Paulo, São Paulo
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Kristen BuckOregon State University, Corvallis, OR
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Manuel ColomboVirginia Institute of Marine Science, Gloucester Point, VA
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Christopher HeinVirginia Institute for Marine Science, Gloucester Point, VA
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Salvatore CapraraOregon State University, Corvallis, OR
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Nicholas WardPacific Northwest National Laboratory, Richland, WA
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Milton KampelInstituçào Nacional de Pesquisas Espaciais, São Paulo, São Paulo
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Jeffrey RicheyUniversity of Washington, Seattle, WA
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Calyn CrawfordUniversity of South Florida, Saint Petersburg, FL
Abstract
The Amazon River, the world’s largest by discharge, displays estuarine processes over a broad range of spatial and time scales. A recent survey of water and surficial sediments from the Amazon’s mouth and its northwestward migrating mudbanks provides new insights into the spatial extent and timing of key processes controlling carbon cycling, nutrient loading, and sediment budgets. Our results indicate that organic carbon loss from river-transported sediments occurs over a surprisingly limited zone (~100 km), especially when contrasted with large drainage basin length (~3000 km, river length of ~7000 km) and the extensive nearshore depositional system along 1500 km of the northern coast of South America. This does not negate the role of coastal sediments, which periodically experience estuarine (mixed freshwater/saltwater) conditions. Our initial results indicate that nutrients stored in sediment porewaters may be more slowly released into the water column than organic carbon over a much larger area. Moreover, our data suggest that nutrients trends have remained consistent, potentially since the Holocene, along this highly dynamic coastal system. Importantly, our results indicate that carbon burial efficiency in this region is substantially higher than previously estimated for this and similar coastal environments.
Geological Society of America Abstracts with Programs. Vol. 57, No. 6
doi: 10.1130/abs/2025AM-413093
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