TITLE:
The Contribution of Nutrients and Water Properties to the Carbonate System in Three Particular Areas of the Tropical Atlantic (NE-BRAZIL)
AUTHORS:
Leonardo Bertini, Elisabete de Santis Braga
KEYWORDS:
N/P/Si Ratios, Total Alkalinity, CO2 Flux, Dissolved Inorganic Carbon, Trophic Conditions, Western Tropical Atlantic
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.10 No.2,
February
28,
2022
ABSTRACT: Tropical waters show different regional aspects due to specificities in
their nutrient biogeochemical cycles, which can affect the carbon system and
influence their regional role as sinks or sources of CO2. This study
was performed on particular tropical areas that present a different seasonal
behaviour related to the carbon cycle observed in the late rainy season (July
2013). Understanding the CO2 drawdown and outgassing potential in
these areas is needed to call attention to more long-term monitoring efforts
and protect understudied tropical coastal systems more efficiently. This study
is focused on nutrient values, hydrological data, biogeochemical carbon
behaviour linked to the carbonate system and includes estimates of CO2 fluxes in three contrasting areas off the northeastern Brazilian shelf: 1) an
urbanised estuary (Recife-REC), 2) a
coastal Island (Itamaracá-ITA) and 3) an
oceanic archipelago (Fernando de Noronha-FN). In general, REC acted as a
source, while ITA and FN as carbon sinks. In ITA, despite the high DIC and
Total Alkalinity observed (mean ~2360 μmol·kg-1), the sink is
associated with an effective cascading of atmospheric CO2 associated
with turbulent shallow waters coupled with biogenic removal of and precipitation of
CaCO3 by coralline algae. FN acted as a sink, linked to minor
decreases in Total Alkalinity (mean~2295 μmol·kg-1) influenced by
ammonium-based primary production, nitrogen fixation and sporadic entrainment
of nutrient rich waters in the upper thermocline. More studies in different
western tropical Atlantic coastal systems can improve the knowledge of tropical
shelf seas and their contribution to the ocean carbon budget under specific
regional trophic regimes.