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An inner shelf foraminiferal fauna and its response to environmental processes (Adriatic Sea, Italy)

2003; Volume: 35; Issue: 2 Linguagem: Inglês

0556-655X

M. Morisieri, Sandra Donnici, R. Serandrei Barbero, Laura Carbognin,

Isotope Analysis in Ecology

espanolEntre febrero de 1991 y enero de 1995, desde una estacion fija ubicada en la plataforma continental adriatica (16 m de profundidad) con influencias del delta, se extrajeron 25 muestras de sedimento para el estudio de la asociacion de foraminiferos bentonicos y sus variaciones. Conjuntamente con la extraccion se realizo un registro de los parametros hidrologicos del fondo durante 24 horas y se extrajo una muestra de agua para la evaluacion del contenido de nutrientes, carbono organico y hierro. El ambiente de plataforma continental interna se encuentra preferentemente sujeto a fenomenos de mezcla vertical con las aguas fluviales. Los parametros hidrologicos se caracterizan por una ausencia marcada de estacionalidad. La biocenosis (tenida con rosa bengala), representada por 64 taxones, muestra una composicion anual constante, pero posee una dinamica compleja con evolucion temporal de las poblaciones individuales irregulares e inconstantes; su entropia se mantiene constante. La asociacion de individuos muertos, constituida por 88 especies, muestra una gran homogeneidad temporal y espacial, y diferencias sistematicas con la asociacion de individuos vivos. Las relaciones estadisticas entre los taxones vivientes y los parametros ambientales indican una disponibilidad intermitente de fitoplancton como factor de principal influencia en la productividad de los foraminiferos bentonicos; estas fluctuaciones en los taxones dominantes y subdominantes parecen estar controladas por mecanismos de competitividad interespecifica. EnglishFrom February 1991 to January 1995, 25 samples of sea bottom sediment were collected at a depth of 16 m from a station located on the Adriatic inner shelf, to study the temporal changes of benthic foraminifera association. During the sampling, 24-hour recordings of sea bottom hydrological parameters were performed and one water sample was taken to evaluate nutrient, organic carbon and iron content. The inner continental shelf environment studied here is subject to vertical mixing with river waters. The main feature of the hydrological parameters is their marked lack of seasonality. The living assemblage (stained with Rose Bengal) is composed of 64 taxa. The number of living individuals remains yearly constant, although the dynamics are complex, with irregular and discontinuous time behavior for single populations. In confirmation of this, the H values of the Shannon?s index of species diversity, calculated on each sampling interval, in spite of their variability, do not show any trend or seasonality. The dead assemblage, composed of 88 species, shows systematic differences with the living assemblage: Rotaliina dominate in the living assemblage and Textulariina and Miliolina dominate in the dead one. To obtain an overall view of the complex system, both univariate and multivariate statistical analyses of living taxa and environmental parameters were used. The results indicate that the occasional availability of phytoplankton is the main factor influencing the productivity of benthic foraminifera in this shallow water basin with deltaic influence. Fluctuations in dominant and subdominant taxa are linked to biotic interactions.