Benthic fluxes of dissolved nutrients, oxygen, dissolved inorganic carbon, and total alkalinity were measured over a 2 yr period in Tomales Bay, California, USA, using in situ incubation chambers. Release of dissolved nutrients from the sediment peaked in late summer and was lowest in winter. The difference between C : N : P flux ratios and composition of suspended particulates indicated the existence of a sink for regenerated N, relative to C and P. Total alkalinity flux revealed that carbon metabolism by net sulfate reduction represented ca one-third of total benthic metabohsm Partitioning net system fluxes into component fluxes suggested that the equivalent of ca 70 to 80 % of the available particulate C, N and P was respired within the water column, while about 20 to 30 O/ O was respired by the benthos. During spring, increasing light resulted in higher water column productivity, followed closely by rising water column respiration. With low delivery of the new organic material to the benthos, and low residual organics in the sediment, benthic respiration remained low. Fallout of particulate material, coinciding with peak water temperature in late summer, resulted in a 'crossover' with benthic respiration temporarily exceeding water column respiration.
Coral reefs are highly complex systems characterized by mostly nonlinear relationships between biotic and abiotic components. Traditional models of reef dynamics often require unavailable data and precision, which limits their success and usefulness. We tested a new approach in coral reef modeling with fuzzy logic. Fuzzy logic has been applied successfully in modeling highly nonlinear systems in engineering, decision support systems, and ecology. As part of an integrated coastal zone management model, we constructed a coral reef model that predicts changes in coral cover and diversity under anthropogenic stress, namely nutrient enrichment and increased sedimentation. The model reflects our current knowledge of the fringing reefs of Curaçao, Netherlands Antilles. The seven input variables used were dissolved inorganic nitrogen and phosphate, suspended particulate matter, maximum colony size, substratum available for colonization, coral cover, and coral diversity. Each variable was divided into three triangular fuzzy sets reflecting low, medium, and high values. For each of the 2187 possible input combinations we estimated cover and diversity after 10 years. We consulted experts with a thorough knowledge of the local reef system and have automatically accounted for interactions between the variables described above. The model clearly shows how increases in nutrient and sediment inputs affect coral cover and diversity. Although the model can be refined continuously, it appears to reflect accurately the current knowledge of reef dynamics, making a beneficial contribution to education, management, and science. Modelo Lógico Indistinto para Predecir el Desarrollo de Arrecifes de Coral Bajo Estreees de Nutrientes y Sedimentos Los arrecifes de coral son sistemas altamente complejos caracterizados por relaciones mayormente no lineales entre sus componentes bióticos y abióticos. Tradicionalmente los modelos de arrecifes de coral requieren de datos que no están a la mano, así como de precisión, limitando su éxito y su utilidad. Probamos una aproximación nueva en modelado de arrecifes conocida como modelo lógico indistinto (fuzzy logic model). Este sistema ha sido aplicado satisfactoriamente en modelado de sistemas no lineales en ingeniería, en sistemas de soporte de decisiones y en ecología. Construímos un modelo de arrecife coralino como parte de un modelo de manejo integral de zonas costeras que predice cambios en la cobertura coralina y la diversidad bajo estrés antropogénico (enriquecimiento de nutrientes e incremento en sedimentación). El modelo refleja nuestro actual conocimiento de la franja de arrecifes de Curazao, Antillas de los Paises Bajos. Las variables utilizadas fueron nitrógeno y fosfato inorgánico disuelto, partículas en suspensión, tamaño máximo de la colonia, disponibilidad de substrato para colonización, cobertura coralina y diversidad coralina. Cada variable fue dividida en tres juegos triagulares indistintos reflejando valores bajos, medios y altos. Estimamos la cobertura y diversidad después de 10 años para cada una de las 2187 combinaciones posibles de datos. Las interacciones entre las variables descritas anteriormente fueron automáticamente tomadas en consideración utilizando expertos con un conocimiento meticuloso del sistema coralino local. El modelo muestra claramente como los incrementos en la entrada de nutrientes y sedimentos al sistema afectan la cobertura y diversidad coralina. Aunque el modelo puede ser refinado continuamente, aparentemente refleja con precisión el conocimiento actual de las dinámicas de arrecifes aportando una contribución benéfica para la educación, el manejo y la ciencia.
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