Abstract
The overall aim of this PhD thesis was to investigate sedimentary micro-environments and ecosystem
functioning of two coastal areas. We combined different high spatial resolution methods and multivariate analyses at
different spatio-temporal scales to reveal interactions between benthic faunal and geochemical compartments. Firstly,
we investigated two stations with contrasted oxygen, nitrate and manganese conditions in the Gullmar Fjord (Sweden).
We revealed the high contribution (50–100 %) of denitrifying benthic foraminifera to the nitrogen cycle in oxygenated
and nitrate-rich micro–environments. Nitrogen and manganese cycles are closely related to oxygenation conditions of
the ecosystem. Our results highlighted the high contribution (87 %) of macrofaunal bioirrigation to Mn release to the
water column under hypoxic conditions. Secondly, we focused on a monthly monitoring of two ecological bioindicators
groups; microphytobenthos (MPB) and foraminifera in the Bourgneuf Bay mudflat (France). We showed that
foraminiferal reproduction events were modulated by unfavorable conditions (high hydrodynamic and winter conditions)
versus favorable conditions (low hydrodynamic and summer conditions). We also demonstrated that foraminiferal
species fed preferentially on diatom species based on their shape, size and life-forms. We further compared, with high
spatial resolution methods, geochemical conditions at two contrasted months, which allowed to clarify the behavior of
redox species and nutrients. Then, foraminiferal micro-distributions indicated the state of sediment instability versus
stability. Finally, this doctoral research opens new perspectives in the use of high spatial resolution in 2D/3D to solve
complex benthic ecology problems.
functioning of two coastal areas. We combined different high spatial resolution methods and multivariate analyses at
different spatio-temporal scales to reveal interactions between benthic faunal and geochemical compartments. Firstly,
we investigated two stations with contrasted oxygen, nitrate and manganese conditions in the Gullmar Fjord (Sweden).
We revealed the high contribution (50–100 %) of denitrifying benthic foraminifera to the nitrogen cycle in oxygenated
and nitrate-rich micro–environments. Nitrogen and manganese cycles are closely related to oxygenation conditions of
the ecosystem. Our results highlighted the high contribution (87 %) of macrofaunal bioirrigation to Mn release to the
water column under hypoxic conditions. Secondly, we focused on a monthly monitoring of two ecological bioindicators
groups; microphytobenthos (MPB) and foraminifera in the Bourgneuf Bay mudflat (France). We showed that
foraminiferal reproduction events were modulated by unfavorable conditions (high hydrodynamic and winter conditions)
versus favorable conditions (low hydrodynamic and summer conditions). We also demonstrated that foraminiferal
species fed preferentially on diatom species based on their shape, size and life-forms. We further compared, with high
spatial resolution methods, geochemical conditions at two contrasted months, which allowed to clarify the behavior of
redox species and nutrients. Then, foraminiferal micro-distributions indicated the state of sediment instability versus
stability. Finally, this doctoral research opens new perspectives in the use of high spatial resolution in 2D/3D to solve
complex benthic ecology problems.
| Original language | English |
|---|---|
| Qualification | Doctor |
| Awarding Institution |
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| Supervisors/Advisors |
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| Award date | 2021 Jul 9 |
| Place of Publication | Angers |
| Publisher | |
| Publication status | Published - 2021 Jul 9 |
| Externally published | Yes |
Subject classification (UKÄ)
- Environmental Sciences
- Ecology