THE DISTRIBUTION OF ORGANIC MATTER AND MODERN SEDIMENTARY PROCESSES IN AN URBAN TROPICAL ESTUARINE SYSTEM, BRAZIL

Abstract Aim: There are few studies dealing with the biogeochemical processes occurring in small estuaries receiving high sewage loading in tropical regions. The aim of this investigation was to characterize the biogeochemical behavior of nutrients in superficial waters collected at the Iguaçu estuarine system, during specific conditions (neap tide), located at the inner sector of a heavily eutrophicated embayment (Guanabara Bay, SE Brazil). Methods Physical and chemical variables were measured in situ (pH, temperature, conductivity, salinity, total dissolved solids, transparency, dissolved oxygen), whereas suspended particulate matter, chlorophyll a, phaepigments and nutrients (carbon, nitrogen and phosphorus forms) were measured in laboratory across the mesohaline estuarine gradient. Results The Iguaçu River mouth is in a high stage of eutrophication, considering nutrient concentrations, chlorophyll a and transparency of water column. Results indicate a transition from heterotrophic conditions to autotrophic conditions, since the nutrients concentrations showed a decreasing pattern along the saline gradient, while the chlorophyll an increased over the transects. The pH values and chlorophyll : phaeopigments ratios are significantly related to the amount and quality of organic matter contents, especially at transects under strong marine influence. More than 95% of the dissolved and total nitrogen concentrations are represented by NH4+ contributions, which are related to the ammonification of organic matter contents in this region, indicating the existence of untreated sewage loads in this area. Conclusion In this study, the Iguaçu River seemed to contribute with high inputs of nutrients that support important phytoplankton production at the inner regions of the bay related to the CO2 sink and autotrophic metabolism, showing the importance of verifying the biogeochemical behaviors of nutrients in estuarine areas, even in small scale.

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Linking patterns of freshwater discharge and sources of organic matter within the Río de la Plata estuary and adjacent marshes

Marine and Freshwater Research ◽

10.1071/mf16286 ◽

2017 ◽

Vol 68 (9) ◽

pp. 1704 ◽

Cited By ~ 5

Author(s):

Leandro Bergamino ◽

Mark Schuerch ◽

Adriana Tudurí ◽

Silvina Carretero ◽

Felipe García-Rodríguez

Keyword(s):

Organic Matter ◽

Surface Sediments ◽

Sediment Cores ◽

Freshwater Discharge ◽

C3 Plants ◽

Estuarine System ◽

Rio De La Plata ◽

Río De La Plata ◽

La Plata ◽

Matter Transport

We investigated carbon isotopic ratios (δ13C) v. carbon to nitrogen (C : N) ratios for surface sediments throughout a large estuarine system (Río de la Plata, RdlP), combined with sediment cores from adjacent marshes to infer main carbon sources. We also evaluated the influence of the El Niño–Southern Oscillation (ENSO) and associated high freshwater-discharge events on the organic-matter transport within the estuary. The isotopic pattern in surface sediments of the RdlP showed the upper reaches to be influenced by riverine particulate matter (δ13C range: –24 to –26‰). Similarly, in the sediment cores from marshes of the upper reaches, δ13C values decreased from –24‰ in ancient sediments to –28‰ in recent sediments, reflecting an increased contribution of organic matter from land, including C3 plants and freshwater phytoplankton, during the past 50 years. However, the lower reaches represent a depositional environment of marine algae (δ13C range: –21 to –23‰), with no influence of detritus from adjacent marshes, indicating minor erosion of the marshes in the lower reaches operating as carbon-sink habitats. Our isotopic analysis showed that the transport and deposition of terrigenous organic matter within the RdlP and adjacent marsh habitat appear to be both temporally and spatially linked to hydrology patterns.

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Phytoplankton community structure is governed by salinity gradient and nutrient composition in the tropical estuarine system

Continental Shelf Research ◽

10.1016/j.csr.2021.104643 ◽

2022 ◽

pp. 104643

Author(s):

M.D. Bharathi ◽

V. Venkataramana ◽

V.V.S.S. Sarma

Keyword(s):

Community Structure ◽

Phytoplankton Community ◽

Salinity Gradient ◽

Nutrient Composition ◽

Estuarine System ◽

Phytoplankton Community Structure ◽

Tropical Estuarine

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Nitrogen fixation and carbon uptake in a tropical estuarine system of Goa, western India

Journal of Sea Research ◽

10.1016/j.seares.2018.09.018 ◽

2019 ◽

Vol 144 ◽

pp. 16-21

Author(s):

Ayaz Ahmed ◽

Hema Naik ◽

Sarvesh S. Adel ◽

Pratirupa Bardhan ◽

Mangesh Gauns ◽

...

Keyword(s):

Nitrogen Fixation ◽

Carbon Uptake ◽

Western India ◽

Estuarine System ◽

Tropical Estuarine

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The Mangrove Periwinkle Littoraria angulifera (Mollusca: Littorinidae) in the Urabá Gulf (Colombian Caribbean): Finding Ways in an Urbanizing Coast?

Frontiers in Marine Science ◽

10.3389/fmars.2021.641567 ◽

2021 ◽

Vol 8 ◽

Author(s):

Jhostin Ramos ◽

Marco Boto ◽

Juan Felipe Blanco-Libreros ◽

José M. Riascos

Keyword(s):

Urban Areas ◽

Size Structure ◽

Woody Debris ◽

Land Use Changes ◽

Estuarine System ◽

Mangrove Forests ◽

Demographic Traits ◽

Tropical Estuarine ◽

Anthropogenic Substrates ◽

Different Populations

Periwinkles (Littorinidae: genus Littoraria) are one of the very few molluscan clades showing an adaptive radiation closely associated to the mangrove habitat. However, pervasive land use changes associated to urbanization is prompting mangrove loss or degradation, with unknown consequences for mangrove-associated fauna. In the southern Colombian Caribbean, mangrove ecosystems have been encroached by human settlements and different populations of Littoraria angulifera (Lamarck, 1822) now inhabit anthropogenic intertidal substrates in urban areas, but the demographic traits of populations thriving in these novel environments are unknown. We studied the relative abundance and size structure of L. angulifera in remnant mangrove patches, woody debris and anthropogenic substrates (boulder seawalls and built structures) in 13 locations throughout the Urabá Gulf, a human-transformed tropical estuarine system. The abundance of L. angulifera was up to two orders of magnitude higher in anthropogenic than in quasi-natural or natural substrates. Snails also displayed a significant preference for wave protected positions in boulder seawalls and built structures exposed to heavy wave action, which was not previously reported in mangrove forests. Moreover, snail populations in anthropogenic substrate were consistently dominated by individuals of small sizes in comparison with mangroves or driftwood. We argue that the anthropogenic disturbances caused by the expansion of Turbo city during nearly one century in a coast formerly dominated by mangrove forests are providing novel and expanding habitats, whose quality might be good enough as to support high-density populations of L. angulifera. However, we hypothesize that shifted thermal regimes in hard and novel wave-exposed urban seascapes might also be prompting behavioral adjustments and the selection of smaller size ranges than those observed in mangrove forests.

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Hydrology of a Tropical Estuarine System: Itamaracá, Brazil

Estuarine Coastal and Shelf Science ◽

10.1006/ecss.1993.1030 ◽

1993 ◽

Vol 36 (5) ◽

pp. 495-515 ◽

Cited By ~ 27

Author(s):

Carmen Medeiros ◽

Björn Kjerfve

Keyword(s):

Estuarine System ◽

Tropical Estuarine

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Transport and transformation of dissolved organic matter in the Neuse River estuarine system, NC, USA, following Hurricane Irene (2011)

Marine and Freshwater Research ◽

10.1071/mf15352 ◽

2016 ◽

Vol 67 (9) ◽

pp. 1313 ◽

Cited By ~ 5

Author(s):

Richard L. Miller ◽

Matthew M. Brown ◽

Ryan P. Mulligan

Keyword(s):

Organic Matter ◽

Dissolved Organic Matter ◽

Estuarine System ◽

Spectral Parameters ◽

Visible Absorption ◽

Neuse River ◽

Hurricane Irene ◽

Rain Events ◽

River Estuarine

Rivers are major conduits for the transport of allochthonous dissolved organic matter (DOM) to the ocean in coupled land–coastal systems. DOM can regulate biogeochemical processes and affect water quality, depending on the concentration and quality of DOM. By using spectral parameters calculated from chromophoric dissolved organic matter (CDOM) ultraviolet-visible absorption spectra, along with dissolved organic carbon (DOC) concentrations, we examined the input and change in the amount and quality of DOM in surface waters of the lower Neuse River and upper–middle regions of the Neuse Estuary following a major rainfall (30cm in 1 day) associated with Hurricane Irene (2011). CDOM and DOC nearly tripled in the 3 days following the storm. Although a strong linear relationship was observed between DOC and CDOM absorption coefficient at 350nm (R2=0.85), a higher fraction of non-chromophoric DOC to CDOM was observed during the rising river discharge. The spectral slope at 275–295nm and the slope ratio (275–295:350–400nm) indicated a shift from higher to lower molecular-weight DOM as it transited through the estuary, probably as a result of photodegradation. The present study demonstrated the utility of using CDOM spectral parameters for examining the flux and transformation of DOM in coastal waters following major rain events.

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