Trophic dynamics (Dissolved Inorganic Nitrogen-DIN and Dissolved Inorganic Phosphorus-DIP) in tropical urban estuarine systems during periods of high and low river discharge rates.

Carlos Noriega,Manuel Flores-Montes,Julia Araujo,Moacyr Araujo

doi:10.1590/0001-3765201920180244

Carlos Noriega, Manuel Flores-Montes + Show 2 more

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https://doi.org/10.1590/0001-3765201920180244

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Abstract

This paper focused on the use of the biogeochemical LOICZ (Land Ocean Interactions in the Coastal Zone) to investigate the dynamics of DIN and DIP nutrients among three highly urbanized tropical estuaries (Barra das Jangadas (BJ), Recife (RE) and Timbó (TB)), located in the northeastern region of Brazil. The input data were obtained through in situ measurements (2007) and governmental agency databases (2001-2007). The balances of the non-conservative elements showed that the RE and TB systems alternated between sources and sinks during the observation periods (0.2-0.8 mmoles DIP m-2 d-1 and 0.1-10 mmoles DIN m-2 d-1). The metabolism rates in the systems indicated that the BJ system was autotrophic during the two observation periods (10-26 mmoles C m-2 d-1), while the RE system was heterotrophic (9-12 mmoles C m-2 d-1). The river discharge rates observed during the period 2001-2007 showed averages ranging from 9.4±3.8 to 18.4±7.7 m3s-1. Measurements of the trophic status in the RE system during 2007 characterized the system as eutrophic, thereby demonstrating high levels of chlorophyll-a and inorganic nutrients. The applications of balance sheets modeling proved to be very useful toward understanding the dynamics of estuarine systems dominated by large urban centers.

Highlights

The transport and release of carbon (C), nitrogen (N) and phosphorus (P) from land to the coastal oceans has become a matter of notable concern and interest during recent decades (Liu et al 2010, Howarth et al 1996, Nixon 1995)
To understand the biogeochemistry of estuarine ecosystems, it is important to note that the hydrological system is the most important element in the biogeochemical cycle because it controls the retention of organic matter and dissolved inorganic nutrients derived from terrestrial environments or river discharge (Noriega and Araujo 2014)
Through hierarchical agglomerative cluster analysis and principal component analysis, we identified the areas and months that showed similar characteristics

Summary

Introduction

The transport and release of carbon (C), nitrogen (N) and phosphorus (P) from land to the coastal oceans has become a matter of notable concern and interest during recent decades (Liu et al 2010, Howarth et al 1996, Nixon 1995). To understand the biogeochemistry of estuarine ecosystems, it is important to note that the hydrological system is the most important element in the biogeochemical cycle because it controls the retention of organic matter and dissolved inorganic nutrients derived from terrestrial environments or river discharge (Noriega and Araujo 2014). In this way, the maintenance of the ecological properties in an estuary depends on the balance between its capacity to absorb or export pollutants versus the magnitude of the estuarine input into the system. The intake of nutrients is intensified within estuaries located in highly and densely populated regions due to contributions from domestic and industrial effluents and urban outflow, as well as those from agricultural effluents

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