Carbon dynamics at the river–estuarine transition: a comparison among tributaries of Chesapeake Bay
<p>Sources and transformation of carbon (C) were quantified using mass balance and ecosystem metabolism data for the upper segments of the James, Pamunkey and Mattaponi estuaries. The goal was to assess the role of external (river inputs and tidal exchange) vs. internal (metabolism) drivers in...
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2022-09-01
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Series: | Biogeosciences |
Online Access: | https://bg.copernicus.org/articles/19/4209/2022/bg-19-4209-2022.pdf |
Summary: | <p>Sources and transformation of carbon (C) were quantified using mass balance
and ecosystem metabolism data for the upper segments of the James, Pamunkey
and Mattaponi estuaries. The goal was to assess the role of external (river
inputs and tidal exchange) vs. internal (metabolism) drivers in influencing
the forms and fluxes of C. C forms and their response to river discharge
differed among the estuaries based on their physiographic setting. The
James, which receives the bulk of inputs from upland areas (Piedmont and
Mountain), exhibited a higher ratio of inorganic to organic C and larger
inputs of particulate organic C (POC). The Pamunkey and Mattaponi receive a
greater proportion of inputs from lowland (Coastal Plain) areas, which were
characterized by low dissolved inorganic C (DIC) and POC and elevated
dissolved organic C (DOC). I anticipated that transport processes would
dominate during colder months when discharge is elevated and metabolism is
low and that biological processes would predominate in summer, leading to
attenuation of C throughputs via degassing of CO<span class="inline-formula"><sub>2</sub></span>. Contrary to
expectations, the highest retention of organic C occurred during periods of high
throughput, as elevated discharge resulted in greater loading and retention
of POC. In summer, internal cycling of C via production and respiration was
large in comparison to external forcing despite the large riverine influence
in these upper-estuarine segments. The estuaries were found to be net
heterotrophic based on retention of organic C, export of DIC, low primary
production relative to respiration and a net flux of CO<span class="inline-formula"><sub>2</sub></span> to the
atmosphere. In the James, greater contributions from phytoplankton
production resulted in a closer balance between production and respiration,
with autochthonous production exceeding allochthonous inputs. Combining the
mass balance and metabolism data with bioenergetics provided a basis for
estimating the proportion of C inputs utilized by the dominant metazoan. The
findings suggest that invasive catfish utilize 15 % of total organic C
inputs and up to 40 % of allochthonous inputs to the James.</p> |
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ISSN: | 1726-4170 1726-4189 |