Sinking particles in the photic zone: relations with biogeochemical properties in different sectors of the Cananéia-Iguape Estuarine-Lagoon Complex (CIELC)-Brazil
Over the last decades, regional climate changes, erosion, and heightened agricultural runoffs have increased nutrient and particle input in rivers, unbalancing the biogeochemical cycle of this suspended material along estuaries. In this context, particle fluxes in the euphotic zone, a very producti...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Instituto Oceanográfico da Universidade de São Paulo
2024-04-01
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| Series: | Ocean and Coastal Research |
| Subjects: | |
| Online Access: | https://www.journals.usp.br/ocr/article/view/222818 |
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| Summary: | Over the last decades, regional climate changes, erosion, and heightened agricultural runoffs have increased
nutrient and particle input in rivers, unbalancing the biogeochemical cycle of this suspended material along
estuaries. In this context, particle fluxes in the euphotic zone, a very productive layer and important to
maintain the food chain and estuarine preservation, require better understanding. This study aims to evaluate
particle sedimentation fluxes in the photic zone of the Cananéia-Iguape Estuarine-Lagoon Complex (CIELC),
considering sectors under different salinities and trophic statuses. A cylindrical sediment trap was installed at
the base of the photic layer to measure particle fluxes and photopigments. Meanwhile, water samples were
taken to measure temperature, salinity, pH, dissolved oxygen, and nutrients. Valo Grande (a freshwater domain)
showed high nutrient concentrations, in which high fluxes of phaeopigments and chlorophyll-b highlighted the
contribution of vegetable detritus to particle sinking. In the Batatais mangrove creek, the high fluxes of organic
particles (675.32 mg m-2 d-1) and chlorophyll-a (98.40 mg m-2 d-1) evinced a high contribution of microplankton
to carbon sinking. During the winter of 2018, flocculation processes were evinced in the flood tide of the
Cananéia Bay as an important driver of sedimentation rates, with considerable fluxes of inorganic particles
(1161.20 mg m-2 d-1) and chlorophyll-a (83.27 mg m-2 d-1). In the summer of 2019, we observed a lower flux in
total particles (451.24 mg m-2 d-1) in a period of haline stratification. In the Ararapira Channel, the lowest organic
particle fluxes (<100 mg m-2 d-1) were associated with ultra-oligotrophic conditions, indicating a low influence
of microplankton on sinking particles. These findings suggest that freshwater input, tidal variation, and trophic
status are relevant controls of sinking particles in different CIELC sectors.
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| ISSN: | 2675-2824 |