Atmospheric Deposition of Nitrogen to a Caribbean Coastal Zone (Cayo Coco,Cuba): Temporal Trends and Relative Importance as a Nitrogen Source |
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| Authors: | Roberto González-De Zayas Martín Merino-Ibarra Felipe Matos-Pupo Martín F Soto-Jiménez |
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| Institution: | 1.Posgrado en Ciencias del Mar y Limnología. Instituto de Ciencias del Mar y Limnología,UNAM, Ciudad Universitaria,Mexico DF,Mexico;2.Unidad Académica de Ecología Marina, Instituto de Ciencias del Mar y Limnología,Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria,Mexico DF,Mexico;3.Centro de Investigaciones de Ecosistemas Costeros,Morón,Cuba;4.Unidad Académica Mazatlán, Instituto de Ciencias del Mar y Limnología,Universidad Nacional Autónoma de México,Mazatlán,Mexico |
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| Abstract: | Nitrogen (N) deposition to the ocean is thought to be increasing worldwide, but the amount of coastal and open ocean measurements
is very limited. In this paper, we assess N deposition in the coastal zone of Cayo Coco, in central Cuba, during a multi-annual
period (2005–2007). Wet and dry N depositions were estimated based on the NH4+ and NOx– concentrations in the rain. Cold fronts and troughs, coming from the west, contributed most to rain (41%) and to N deposition,
followed by tropical waves and storms coming from the east, which caused 31% of the rain. Average concentrations of NH4+ and NOx– in the rain were 8.8 and 8.3 μM. NOx– presented a clearly decreasing trend (0.26 μM per month), decreasing by half during 2005–2007. Total N deposition averaged
3.23 kg N ha−1 year−1, similar to that found in Virgin Islands and Puerto Rico, but lower than previously measured in Cuba and in nearby areas
of the USA and than model predictions for the oceanic region around Cuba. These low values and the decreasing trend found
are attributed to drastic reduction of fossil fuel and fertilizer use in Cuba since 1990. Because land input has decreased
even more drastically, deposition seems to be nowadays the most important N source to the coastal zone of Cayo Coco. The δ15N range of seagrass (Thalassia testudinum) and macroalgae (Penicillus dumetosus) in the area (−1.83‰ to 3.02‰ and +1.02‰ to +4.17‰, respectively) sustain that atmospheric sources (deposition and N2 fixation) comprise 70–90% of the N budget. |
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