Taxonomic distinctness and diversity patterns of a polychaete (Annelida) community on the continental shelf of the Southern Gulf of Mexico.

The spatial patterns of taxonomic diversity of annelid polychaete species from the continental shelf in the Southern Gulf of Mexico were examined in this study. We used taxonomic distinctness and its spatial variations to explore the diversity patterns and how they change between Southern Gulf of Mexico regions. In addition, using taxonomic distinctness as a dissimilarity measure and Ward's Clustering, we characterized three distinct faunal assemblages. We also investigated patterns of richness, taxonomic distinctness, and distance decay of similarity between sampling stations as a ß-diversity measure. Finally, we examined the spatial relationships between polychaete assemblages and environmental variables to test the relative importance of spatial and environmental components in annelid polychaete community structure from the Southern Gulf of Mexico. We used a combination of eigenvector-based multivariate analyses (dbMEMs) and distance-based redundancy analysis (dbRDA) to quantify the relative importance of these explanatory variables on the spatial variations of taxonomic distinctness. The significance level of spatial and environmental components to the distribution of polychaete species showed that the combined effect of spatial processes and sediment characteristics explained a higher percentage of the variance than those parameters could alone.

Chaos and periodicities in a climatic time series of the Iberian Margin.

We analyze the time series of the temperature of the sedimentary core MD01-2443 originating from the Iberian Margin with a duration of 420 kyr. The series has been tested for unit-root and a long term trend is estimated. We identify four significant periodicities together with a low climatic activity every 100 kyr, and these were associated with internal and external forcings. Also, we identify a high-frequency fast component that acts on top of a nonlinear, irreversible slow-changing dynamics. We find the presence of chaos in the climate of the Iberian Margin by means of a neural network asymptotic test on the largest Lyapunov exponent. The analysis suggests that the chaotic dynamics is associated with the fast high-frequency component. We also carry out a statistical analysis of the dimensionality of the attractor. Our results confirm the possibility that periodic behavior and chaos may coexist on different time scales. This could lead to different degrees of predictability in the climate system according to the characteristic time scales and/or phase-space locations.

Efectos de los vórtices en sistemas acuáticos y su relación con la química, biología y geología / Effects of vortices in aquatic systems and its relation to chemistry, biology and geology / Efeitos dos vórtices em sistemas aquáticos e sua relação com a química, biologia e geologia

Se discute la importancia de los vórtices en el transporte de energía interna (calor), sales, nutrientes y sedimentos en los ecosistemas marinos y continentales. Se presentan los efectos de afloramientos de la termoclina y nutriclina ocasionados por la formación de remolinos ciclónicos, los cuales se resumen en un incremento de nutrientes hacia la zona eufótica, lo que conlleva al aumento en producción biológica. También se discuten los efectos de los remolinos anticiclónicos en el transporte de clorofilas y sedimentos a grandes distancias comparadas con sus diámetros. El corolario principal es la necesidad de un trabajo conjunto de las diferentes disciplinas, para un completo entendimiento de los fenómenos que coadyuve a predecir y obtener una razonable explotación de los recursos marinos.

The importance of vortices as one of the principal actors in transporting the internal energy (heat), salts, nutrients and sediments in marine and continental ecosystems is discussed. The thermocline and pycnocline uplift effects caused by the formation of cyclonic vortices, which bring about an increase in nutrients in the euphotic zone, are presented. Also, the effects of anticyclonic vortices in the transport of chlorophyll and sediments over large distances compared to their diameters, are described. The end result is the need of joining efforts by different disciplines to achieve a complete understanding of the phenomena, which could help to predict and reasonably exploit marine resources.

Neste ensaio fala-se da importância dinâmica dos remoinhos como um dos principais atores na transportação de energia interna (calor), sales, nutrientes e sedimentos nos ecosistemas marinhos e continentais. Apresentam-se tambem alguns de seus efeitos no oceano como as urgências causadas pela formação de remoinhos ciclônicos, que têm como consequência um incremento de nutrientes à zona eufôtica. Por outro lado, fala-se tambem sobre os efeitos dos remoinhos anticiclônicos na transportação de clorofilas e sedimentos à grandes distâncias comparadas com os seus diâmetros. O corolario principal é a necessidade de um trabalho conjunto das diferentes disciplinas, para um completo entendimento dos fenômenos que ajude a predizer e a obter uma razoável explotação dos recursos marinhos.