Respuesta fisiológica, productiva y cualitativa del cultivar Syrah (Vitis vinifera L) con diferentes frecuencias de riego y densidad de goteros en suelos arcillosos

La disponibilidad hídrica es uno de los principales factores que determinan el rendimiento del viñedo en muchas regiones vitícolas, por lo que sus consecuencias han sido ampliamente estudiadas. Sin embargo, para una cantidad de agua de riego determinada, otros aspectos como la frecuencia de aplicación, o la combinación entre el caudal de los goteros y la distancia entre los mismos (es decir, el patrón de distribución de agua en el suelo), pueden jugar un papel relevante, pero estos factores han sido poco estudiados. El objetivo de este trabajo ha sido evaluar las implicaciones agronómicas y fisiológicas de dos frecuencias de riego (IrrF, cada 2 y 4 días) y dos patrones de distribución de agua (DisP, goteros de 2 L h-1 separados 0,6 m vs. goteros de 4 L h-1 separados 1,2 m). El experimento se llevó a cabo durante cuatro temporadas consecutivas en un viñedo cv. Syrah con un suelo arcilloso en el centro de España, y los dos factores fueron evaluados bajo dos condiciones de disponibilidad hídrica (Baja: 20% de ETo y Media: 40% de ETo). El efecto de la frecuencia de riego y el patrón de distribución de agua en la respuesta agronómica del cv. Syrah se ha estudiado en el capítulo 1. La frecuencia de riego y el patrón de distribución de agua en el suelo afectaron a algunos aspectos de los componentes de rendimiento y desarrollo vegetativo en las dos condiciones de disponibilidad hídrica, aunque los efectos observados no fueron los mismos todos los años. Los efectos fueron más evidentes para IrrF en condiciones de baja disponibilidad hídrica y para DisP en condiciones de disponibilidad hídrica media. Dos de los cuatro años del experimento, el pasar de frecuencia de riego de 2 días a 4 días causó un incremento medio de rendimiento del 20% para la situación de baja disponibilidad hídrica. La textura del suelo, sin duda ha condicionado los resultados obtenidos en los tratamientos regados con el 20% de la ETo, ya que regar cada dos días implicaba la aplicación de pequeñas cantidades de agua y se formaban bulbos de riego superficiales, probablemente favoreciendo las pérdidas por evaporación. En el capítulo 2, se ha analizado el efecto de la frecuencia de riego y del patrón de distribución de agua en el estado hídrico de la planta y el intercambio gaseoso a nivel de hoja con el fin de explicar las diferencias observadas en la respuesta agronómica. En lo que respecta a la frecuencia de riego, en condiciones de baja disponibilidad hídrica, las plantas regadas cada 4 días (plantas 4d), mostraron mayores tasas de asimilación neta y conductancia estomática que las plantas regadas cada 2 días (plantas 2d), lo que es consistente con la hipótesis de que con la frecuencia de riego de 2 días se produjo una pérdida de eficiencia del uso del agua, probablemente debido a una mayor evaporación como consecuencia del hecho de que el volumen de suelo mojado creado era pequeño y cerca de la superficie. En condiciones de disponibilidad hídrica media, las diferencias en el intercambio gaseoso a nivel de hoja fueron mucho más pequeñas. Al comienzo del verano cada frecuencia de riego se comportó mejor uno de los días de medida, compensando al final del ciclo de riego de 4 días. Sin embargo, a medida que avanzó el verano y el déficit de agua se hizo más alto, las diferencias significativas aparecieron sólo en el 'día 4' del ciclo de riego, cuando las plantas 2d se comportaron mejor que las plantas regadas 4d que llevaban tres días sin regarse. Estas diferencias fisiológicas fueron menores que en condiciones de baja disponibilidad hídrica y al parecer no suficientes para afectar el comportamiento agronómico. En cuanto al patrón de distribución de agua, el efecto fue poco significativo, pero la mayor densidad de goteros tendió a presentar un mayor intercambio gaseoso a nivel de hoja, especialmente a media mañana. El efecto fue más importante para las condiciones de disponibilidad hídrica media. En el capítulo 3, se han comparado las relaciones entre el intercambio gaseoso a nivel de hoja, el estado hídrico y la demanda atmosférica, con el fin de explicar los cambios en la intensidad de la respuesta fisiológica observados en el Capítulo 2. No se han encontrado diferencias en dichas relaciones para el patrón de distribución de agua, por lo que sólo se ha analizado el efecto de la frecuencia de riego. El estudio se ha centrado fundamentalmente en si las plantas mostraron una respuesta fisiológica diferente a los cambios en el estado hídrico y en la demanda atmosférica según el tiempo transcurrido desde el último riego. Las diferencias observadas explican los resultados obtenidos en los capítulos anteriores, y sugieren la existencia de procesos de aclimatación vinculados a la frecuencia de riego y a la disponibilidad hídrica. Las plantas bajo condiciones de baja disponibilidad hídrica se mostraron más aclimatadas al estrés hídrico que aquellas en condiciones de disponibilidad hídrica media. La frecuencia de riego afectó claramente la relación entre los parámetros de intercambio gaseoso a nivel de hoja, el estado hídrico de la planta y las condiciones atmosféricas, y junto con la cantidad de agua aplicada tuvo implicaciones en el desarrollo de mecanismos de aclimatación que afectaron a la respuesta fisiológica de la planta, afectando a la eficiencia del riego. ABSTRACT Water availability is one of the major factors that determine vineyard performance in many grape growing regions, so its implications have been widely studied before. However, for a given irrigation water amount, other aspects such as application frequency, or emitter spacing and flow rate (i.e., distribution pattern), may play a relevant role, but these factors have been scarcely studied. The aim of this work was to evaluate the agronomic and physiological implications of two irrigation frequencies (IrrF, every 2 and 4 days) and two water distribution patterns (DisP, 2 L h−1 emitters every 0.6 m vs. 4 L h−1 emitters every 1.2 m). The experiment was carried out during four consecutive seasons in a cv. Syrah vineyard with a clay soil in central Spain, and the two factors were evaluated under two water availability conditions (LOW WA: 20% of ETo and MEDIUM WA: 40% of ETo). The effect of irrigation frequency and water distribution pattern on the agronomical response of cv. Syrah was studied in Chapter 1. IrrF and DisP affected some aspects of vegetative development and yield components under both water availability conditions, although the effects observed were not the same every year. The effects were more evident for IrrF under low water availability and for DisP under medium water availability. Two out of the four years of the experiment, the change of irrigation frequency from 2 days to 4 days promoted an average yield increase of 20% for the LOW WA situation. Soil texture certainly conditioned the results obtained under LOW WA conditions, since high frequency irrigation implied applying small amounts of water that resulted in limited superficial water bulbs, which probably favored water evaporation. In Chapter 2, the effect of irrigation frequency and water distribution pattern on plant water status and leaf gas exchange was analyzed to explain the differences observed in the agronomical response. Concerning irrigation frequency, under LOW WA conditions, applying irrigation every 4 days, resulted in higher net assimilation rates and stomatal conductance than doing it every 2 days, supporting the hypothesis that the latter frequency resulted in a water use efficiency loss, probably due to higher evaporation as a consequence of the fact the wetted soil volume created was small and close to the surface. Under MEDIUM WA conditions, differences in leaf gas exchange were much smaller. At the beginning of the summer each irrigation frequency behaved better one of the measurements days, compensating at the end of the 4-day irrigation cycle. However, as the summer progressed and water deficit became higher, significant differences appeared only on ‘day 4’ of the irrigation cycle, when 2d plants behaved better than 4d plants. These physiological differences were smaller than under LOW WA conditions and apparently not sufficient to affect agronomical performance. Regarding water distribution pattern, the effect was less significant but the closest emitter spacing resulted in general terms in a higher leaf gas exchange, especially at midmorning. The effect was more noticeable for MEDIUM WA conditions. In Chapter 3, the relationships between leaf gas exchange and leaf water status and atmospheric demand were compared to explain the changes in the intensity of the physiological response observed in Chapter 2. No differences were found in the relationships for water distribution pattern, so only the effect of irrigation frequency was analyzed focusing on whether the plants have a different physiological response to changes in water status and atmospheric demand according to the time elapsed since the last irrigation. Differences observed in the relationships explained the results obtained in the previous chapters, and point at the occurrence of acclimation processes linked to irrigation frequency and to water availability. Plants under LOW WATER AVAILABILITY conditions seemed to be more acclimated to water stress than those under MEDIUM WATER AVAILABILITY conditions. Irrigation frequency clearly affected the relationship between leaf gas exchange parameters, plant water status and atmospheric conditions, and together with the amount of water applied had implications in the development of acclimation mechanisms that affected plant physiological response, thus affecting irrigation efficiency.

Generation of secretable and nonsecretable interleukin 15 isoforms through alternate usage of signal peptides

Two isoforms of human interleukin 15 (IL-15) exist. One isoform has a shorter putative signal peptide (21 amino acids) and its transcript shows a tissue distribution pattern that is distinct from that of the alternative IL-15 isoform with a 48-aa signal peptide. The 21-aa signal isoform is preferentially expressed in tissues such as testis and thymus. Experiments using different combinations of signal peptides and mature proteins (IL-2, IL-15, and green fluorescent protein) showed that the short signal peptide regulates the fate of the mature protein by controlling the intracellular trafficking to nonendoplasmic reticulum sites, whereas the long signal peptide both regulates the rate of protein translation and functions as a secretory signal peptide. As a consequence, the IL-15 associated with the short signal peptide is not secreted, but rather is stored intracellularly, appearing in the nucleus and cytoplasmic components. Such production of an intracellular lymphokine is not typical of other soluble interleukin systems, suggesting a biological function for IL-15 as an intracellular molecule.

Kinase Activity-dependent Nuclear Export Opposes Stress-induced Nuclear Accumulation and Retention of Hog1 Mitogen-activated Protein Kinase in the Budding Yeast Saccharomyces cerevisiae

Budding yeast adjusts to increases in external osmolarity via a specific mitogen-activated protein kinase signal pathway, the high-osmolarity glycerol response (HOG) pathway. Studies with a functional Hog1–green fluorescent protein (GFP) fusion reveal that even under nonstress conditions the mitogen-activated protein kinase Hog1 cycles between cytoplasmic and nuclear compartments. The basal distribution of the protein seems independent of its activator, Pbs2, and independent of its phosphorylation status. Upon osmotic challenge, the Hog1–GFP fusion becomes rapidly concentrated in the nucleus from which it is reexported after return to an iso-osmotic environment or after adaptation to high osmolarity. The preconditions and kinetics of increased nuclear localization correlate with those found for the dual phosphorylation of Hog1–GFP. The duration of Hog1 nuclear residence is modulated by the presence of the general stress activators Msn2 and Msn4. Reexport of Hog1 to the cytoplasm does not require de novo protein synthesis but depends on Hog1 kinase activity. Thus, at least three different mechanisms contribute to the intracellular distribution pattern of Hog1: phosphorylation-dependent nuclear accumulation, retention by nuclear targets, and a kinase-induced export.

Dopamine receptor subtypes modulate olfactory bulb γ-aminobutyric acid type A receptors

The γ-aminobutyric acid type A (GABAA) receptor is the predominant Cl− channel protein mediating inhibition in the olfactory bulb and elsewhere in the mammalian brain. The olfactory bulb is rich in neurons containing both GABA and dopamine. Dopamine D1 and D2 receptors are also highly expressed in this brain region with a distinct and complementary distribution pattern. This distribution suggests that dopamine may control the GABAergic inhibitory processing of odor signals, possibly via different signal-transduction mechanisms. We have observed that GABAA receptors in the rat olfactory bulb are differentially modulated by dopamine in a cell-specific manner. Dopamine reduced the currents through GABA-gated Cl- channels in the interneurons, presumably granule cells. This action was mediated via D1 receptors and involved phosphorylation of GABAA receptors by protein kinase A. Enhancement of GABA responses via activation of D2 dopamine receptors and phosphorylation of GABAA receptors by protein kinase C was observed in mitral/tufted cells. Decreasing or increasing the binding affinity for GABA appears to underlie the modulatory effects of dopamine via distinct receptor subtypes. This dual action of dopamine on inhibitory GABAA receptor function in the rat olfactory bulb could be instrumental in odor detection and discrimination, olfactory learning, and ultimately odotopic memory formation.

Análise do papel da via miR156/SQUAMOSA Promoter-Binding Protein-Like (SPL) na organogênese in vitro a partir de raízes de Arabidopsis thaliana

Os microRNAs (miRNAs) são pequenos RNAs endógenos não codantes de 21-24 nucleotídeos (nt) que regulam a expressão gênica de genes-alvos. Eles estão envolvidos em diversos aspectos de desenvolvimento da planta, tanto na parte aérea, quanto no sistema radicular. Entre os miRNAs, o miRNA156 (miR156) regula a família de fatores de transcrição SQUAMOSA Promoter-Binding Protein-Like (SPL) afetando diferentes processos do desenvolvimento vegetal. Estudos recentes mostram que a via gênica miR156/SPL apresenta efeito positivo tanto no aumento da formação de raízes laterais, quanto no aumento de regeneração de brotos in vitro a partir de folhas e hipocótilos em Arabidopsis thaliana. Devido ao fato de que a origem da formação de raiz lateral e a regeneração in vitro de brotos a partir de raiz principal compartilham semelhanças anatômicas e moleculares, avaliou-se no presente estudo se a via miR156/SPL, da mesma forma que a partir de explantes aéreos, também é capaz de influenciar na regeneração de brotos in vitro a partir de explantes radiculares. Para tanto foram comparados taxa de regeneração, padrão de distribuição de auxina e citocinina, análises histológicas e histoquímicas das estruturas regeneradas em plantas com via miR156/SPL alterada, incluindo planta mutante hyl1, na qual a produção desse miRNA é severamente reduzida. Além disso, foi avaliado o padrão de expressão do miR156 e específicos genes SPL durante a regeneração de brotos in vitro a partir da raiz principal de Arabidopsis thaliana. No presente trabalho observou-se que a alteração da via gênica miR156/SPL é capaz de modular a capacidade de regeneração de brotos in vitro a partir de raiz principal de Arabidopsis thaliana e a distribuição de auxina e citocinina presente nas células e tecidos envolvidos no processo de regeneração. Plantas superexpressando o miR156 apresentaram redução no número de brotos regenerados, além de ter o plastochron reduzido quando comparado com plantas controle. Adicionalmente, plantas contento o gene SPL9 resistente à clivagem pelo miR156 (rSPL9) apresentaram severa redução na quantidade de brotos, além de terem o plastochron alongado. Interessantemente, plantas mutantes hyl1-2 e plantas rSPL10 não apresentaram regeneração de brotos ao longo da raiz principal, mas sim intensa formação de raízes laterais e protuberâncias, respectivamente, tendo essa última apresentado indícios de diferenciação celular precoce. Tomados em conjunto os dados sugerem que o miR156 apresenta importante papel no controle do processo de regeneração de brotos in vitro. Entretanto, esse efeito é mais complexo em regeneração in vitro a partir de raízes do que a partir de cotilédones ou hipocótilos.

Desenvolvimento floral e do óvulo e aspectos da reprodução em Aechmea sp. e Vriesea sp. (Bromeliaceae)

A utilização de Bromélias tem sido crescente no mercado de plantas onamentais, por outro lado, muitas espécies encontram-se ameaçadas, grande parte pelos impactos humanos no ambiente. Aechmea correia-araujoi E. Pereira & Moutinho, Aechmea gamossepala Wittm, Vriesea ensiformis (Vell.) Beer e Vriesea saundersii (Carrière) E. Morren ex Mez, espécies nativas da Mata Atlântica brasileira, têm sido alvo de extrativismo. Informações básicas sobre a espécie são essenciais para subsidiar a condução de programas de conservação e melhoramento genético, que aliados a ferramentas biotecnológicas permitem a incorporação de estratégias inovadoras aos métodos de melhoramento. Neste sentido, o objetivo do presente trabalho foi descrever essas espécies, quanto à micromorfologia floral, aspectos reprodutivos envolvidos no processo de polinização, desenvolvimento floral e deesenvolvimento gametofítico, como mecanismo de preservação e produção comercial. A caracterização morfológica e anatômica das flores das espécies de Aechmea e Vriesea contribuiu para a compreensão do processo reprodutivo. As espécies apresentam grãos de pólen com alta capacidade reprodutiva, viabilidade polínica superior a 93%, germinação in vitro maior que 80% e o estigma apresenta-se receptivo da antese ao final do dia. A ontogênese floral de A. correia-araujoi é centrípeta, os primórdios desenvolvem-se na ordem, sépala, pétala, androceu e gineceu. O apêndice petalar é formado na fase final do desenvolvimento. O primórdio de óvulo tem origem placentária e caráter trizonal, o óvulo é anátropo, bitegumentado e crassinucelado. O meristema floral de A. gamosepala se desenvolve de forma centrípeta, de forma unidirecional reversa. O estigma diferencia-se na fase inicial do desenvolvimento e os apêndices petalares, na fase final. O óvulo é anátropo, crassinucelado, bitegumentado, tétrade linear, megásporo calazal funcional, desenvolvimento tipo monospórico e Polygonum. As anteras são bitecas, tetraesporangiadas, com tapete secretor. Botões florais de 8,7 - 13,0 mm são indicados no estudo de embriogênese a partir de micrósporo. As alterações celulares e o padrão de distribuição de pectinas e AGPs foram caracterizadas por análise citoquímica com azul de toluidina, KI e DAPI e imunocitoquímica por imunofluorescência com os anticorpos para RNA, pectinas esterificadas (JIM7), não esterificadas (JIM5) e AGPs (LM2, LM6, MAC207, JIM13, JIM14) e analisadas por microscopia de fluorescência. Foram caracterizados padrões de distribuição espaço-temporal de pectinas e AGP que podem ser utilizados como marcadores de desenvolvimento gametofítico masculino. As observações feitas nesse trabalho fornecem dados sobre aspectos reprodutivos das espécies que podem ser utilizados em programas de melhoramento genético, conservação e desenvolvimento de haploides

Fatores abióticos condicionantes da distribuição de espécies arbóreas em quatro formações florestais do Estado de São Paulo

No estudo das comunidades florestais, estabelecer a importância relativa dos fatores que definem a composição e a distribuição das espécies é um desafio. Em termos de gradientes ambientais o estudo das respostas das espécies arbóreas são essenciais para a compreensão dos processos ecológicos e decisões de conservação. Neste sentido, para contribuir com a elucidação dos processos ecológicos nas principais formações florestais do Estado de São Paulo (Floresta Ombrófila Densa de Terras Baixas, Floresta Ombrófila Densa Submontana, Floresta Estacional Semidecidual e Savana Florestada) este trabalho objetivou responder as seguintes questões: (I) a composição florística e a abundância das espécies arbóreas, em cada unidade fitogeográfica, variam conforme o gradiente edáfico e topográfico?; (II) características do solo e topografia podem influenciar na previsibilidade de ocorrência de espécies arbóreas de ampla distribuição em diferentes tipos vegetacionais? (III) existe relação entre o padrão de distribuição espacial de espécies arbóreas e os parâmetros do solo e topografia? O trabalho foi realizado em parcelas alocadas em unidades de conservação (UC) que apresentaram trechos representativos, em termos de conservação e tamanho, das quatro principais formações florestais presentes no Estado de São Paulo. Em cada UC foram contabilizados os indivíduos arbóreos (CAP ≥ 15 cm), topografia, dados de textura e atributos químicos dos solos em uma parcela de 10,24 ha, subdividida em 256 subparcelas. Análises de correspodência canônica foram aplicadas para estabelecer a correspondência entre a abundância das espécies e o gradiente ambiental (solo e topografia). O método TWINSPAN modificado foi aplicado ao diagrama de ordenação da CCA para avaliar a influência das variáveis ambientais (solo e topografia) na composição de espécies. Árvores de regressão \"ampliadas\" (BRT) foram ajustadas para a predição da ocorrência das espécies segundo as variáveis de solo e topografia. O índice de Getis-Ord (G) foi utilizado para determinar a autocorrelação espacial das variáveis ambientais utilizadas nos modelos de predição da ocorrência das espécies. Nas unidades fitogeográficas analisadas, a correspondência entre o gradiente ambiental (solo e topografia) e a abundância das espécies foi significativa, especialmente na Savana Florestada onde observou-se a maior relação. O solo e a topografia também se relacionaram com a semelhança na composição florística das subparcelas, com exceção da Floresta Estacional Semicidual (EEC). As principais variáveis de solo e topografia relacionadas a flora em cada UC foram: (1) Na Floresta Ombrófila Densa de Terras Baixas (PEIC) - teor de alumínio na camada profunda (Al (80-100 cm)) que pode refletir os teor de Al na superfície, acidez do solo (pH(H2O) (5-25 cm)) e altitude, que delimitou as áreas alagadas; (2) Na Floresta Ombrófila Densa Submontana (PECB) - altitude, fator que, devido ao relevo acidentado, influencia a temperatura e incidência de sol no sub-bosque; (3) Na Savana Florestada (EEA) - fertilidade, tolerância ao alumínio e acidez do solo. Nos modelos de predição BRT, as variáveis químicas dos solos foram mais importantes do que a textura, devido à pequena variação deste atributo no solo nas áreas amostradas. Dentre as variáveis químicas dos solos, a capacidade de troca catiônica foi utilizada para prever a ocorrência das espécies nas quatro formações florestais, sendo particularmente importante na camada mais profunda do solo da Floresta Ombrófila Densa de Terras Baixas (PEIC). Quanto à topografia, a altitude foi inserida na maioria dos modelos e apresentou diferentes influências sobre as áreas de estudo. De modo geral, para presença das espécies de ampla distribuição observou-se uma mesma tendência quando à associação com os atributos dos solos, porém com amplitudes dos descritores edáficos que variaram de acordo com a área de estudo. A ocorrência de Guapira opposita e Syagrus romanzoffiana, cujo padrão variou conforme a escala, foi explicada por variáveis com padrões espaciais agregados que somaram entre 30% e 50% de importância relativa no modelo BRT. A presença de A. anthelmia, cujo padrão também apresentou certo nível de agregação, foi associada apenas a uma variável com padrão agregado, a altitude (21%), que pode ter exercido grande influência na distribuição da espécie ao delimitar áreas alagadas. T. guianensis se associou a variáveis ambientais preditoras com padrão espacial agregado que somaram cerca de 70% de importância relativa, o que deve ter sido suficiente para estabelecer o padrão agregado em todas as escalas. No entanto, a influência dos fatores ambientais no padrão de distribuição da espécie não depende apenas do ótimo ambiental da espécie, mas um resultado da interação espécie-ambiente. Concluiu-se que: (I) características edáficas e topográficas explicaram uma pequena parcela da composição florística, em cada unidade fitogeográfica, embora a ocorrência de algumas espécies tenha se associado ao gradiente edáfico e topográfico; (II) a partir de características dos solos e da topografia foi possível prever a presença de espécies arbóreas, que apresentaram particularidades em relação a sua associação com o solo de cada fitofisionomia; (III) a partir de associações descritivas o solo e a topografia influenciam o padrão de distribuição espacial das espécies, na proporção em que contribuem para a presença das mesmas.

Variabilidad espacio-temporal de paralarvas de cefalópodos en el mar peruano entre los años 2013 y 2014

Se describe la composición de especies, distribución, abundancia y frecuencia de paralarvas de cefalópodos en el mar peruano. Se determinó un total de 14 familias, 8 géneros, 4 especies en un total de 1109 muestras de zooplancton colectadas con red Hensen a 50 metros de profundidad desde la superficie, proveniente de 8 cruceros de investigación ejecutados durante los años 2013 y 2014; siendo las especies más dominantes Argonauta spp. (41.4%) y Abraliopsis sp. (6.4%); y las familias Ommastrephidae (13%), Octopodidae (9.1%), Gonatidae (3.9%) y Pyroteuthidae (3.7%). Las paralarvas mostraron una distribución espacial y una relación especie-específica con las masas de agua. Las especies de Argonauta spp. estuvieron relacionadas con ASS, ACF y AES/ATS, y el aumento de sus abundancias relacionadas con el aumento de temperatura; la familia Ommastrephidae relacionadas con ASS y ACF, con una distribución oceánica; la familia Octopodidae distribuida solo en el norte-centro dentro de la plataforma continental; la familia Gonatidae asociadas únicamente a ACF; mientras que las familias Onychoteuthidae y Pyroteuthidae no mostraron patrón de distribución ni preferencia por alguna masa de agua específica.

(Table 1) Abundance of tunicate spicules along the Great Barrier Reef-Queensland Plateau transect

The abundance patterns of tunicate spicules are documented for the Pliocene-Pleistocene sediments at seven sites along the Great Barrier Reef-Queensland Plateau transect. The spatial distribution pattern indicates that tunicate spicules were limited to waters shallower than 900 m. The occurrences of tunicate spicules at Sites 822 and 823 that are deeper than 900 m are ascribed to downslope transport, and their distribution patterns can be used to monitor downslope transport processes. The first common occurrence of tunicate spicules at Sites 822 and 823 around 1.6 Ma may suggest the initiation of the central Great Barrier Reef at this time. The morphology of tunicate spicules varies greatly and appears to be gradational among different forms. Older tunicate assemblages are less diverse than those in younger sediments, presumably because of diagenesis. Tunicate spicules do not appear to be a promising biostratigraphic tool for the Pliocene-Pleistocene.

Environmental controls on the Emiliania huxleyi calcite mass

Although ocean acidification is expected to impact (bio)calcification by decreasing the seawater carbonate ion concentration, [CO3]2-, there exists evidence of non-uniform response of marine calcifying plankton to low seawater [CO3]2-. This raises questions on the role of environmental factors other than acidification and on the complex physiological responses behind calcification. Here we investigate the synergistic effect of multiple environmental parameters, including temperature, nutrient (nitrate and phosphate) availability, and seawater carbonate chemistry on the coccolith calcite mass of the cosmopolitan coccolithophore Emiliania huxleyi, the most abundant species in the world ocean. We use a suite of surface (late Holocene) sediment samples from the South Atlantic and southwestern Indian Ocean taken from depths lying well above the modern lysocline. The coccolith calcite mass in our results presents a latitudinal distribution pattern that mimics the main oceanographic features, thereby pointing to the potential importance of phosphorus and temperature in determining coccolith mass by affecting primary calcification and possibly driving the E. huxleyi morphotype distribution. This evidence does not necessarily argue against the potentially important role of the rapidly changing seawater carbonate chemistry in the future, when unabated fossil fuel burning will likely perturb ocean chemistry beyond a critical point. Rather our study highlights the importance of evaluating the combined effect of several environmental stressors on calcifying organisms to project their physiological response(s) in a high CO2 world and improve interpretation of paleorecords.

(Table 1) Organohalogen contaminants in adipose tissue of captive sledge dogs (Canis familiaris) fed with whale blubber or pork fat

Studies on the fate of organohalogen contaminants (OHCs) in wild top predator mammals in the Arctic have often been a challenge due to important knowledge deficiencies in the life history of the sampled animals. The present study investigated the influence of age, dietary and trans-generational factors on the fate of major lipophilic chlorinated and brominated OHCs in adipose tissue of a potential surrogate captive species for the polar bear (Ursus maritimus), the sledge dog (Canis familiaris) in West Greenland. Adult female sledge dogs (P) and their sexually-mature (F1) and/or pre-weaning pups (F1-MLK) were divided into an exposed group (EXP) fed blubber from a Greenland minke whale (Balaenoptera acutorostrata) and a control group (CON) given commercially available pork fat. Large dietary treatment-related differences in summed and individual congener/compound adipose tissue concentrations of polybrominated diphenyl ethers (PBDEs), hexachlorobenzene (HCB), chlordanes (CHLs) and polychlorinated biphenyls (PCBs) were found between the EXP and CON groups for all the sledge dog cohorts. However, among the F1-MLK, F1 and P dogs in both of the EXP and CON groups, little or no difference existed in PBDE, HCB, CHL and PCB concentrations, suggesting higher state of equilibrium in adipose tissue concentrations from a very early stage of life. In contrast, the distribution pattern (proportions to the summed concentrations) of OHC classes, and the major congeners/ compounds constituting those classes, varied on a dietary group- and/or cohort-dependent manner. The present captive sledge dog study demonstrated the importance of the confounding effects of diet composition, mother-pup association (maternal transfer), reproductive status (nursing), and to a lesser extent age in the fate of OHCs in adipose tissue of a large top carnivore mammal.

(Table T1) Ages of white mica clasts in core samples of ODP Hole 210-1276A

Fifty-seven white mica clasts were separated from five samples taken from near the bases of turbidites ranging in age from early Albian to middle Eocene. Twenty two (39%) of the micas have ages between 260 and 340 Ma and five (9%) have older ages (~400-600 Ma). The former age range is characteristic of the North American Alleghenian orogeny and the Iberian Variscan orogeny. The latter range is characteristic of the North American Acadian orogeny and older basement rocks in the Grand Banks and Newfoundland areas. Both age ranges are present in the middle Eocene sample, but only the younger range occurs in the middle Albian sample. This difference could be a sampling artifact. If this is not the case, then the most likely explanation is that the Acadian-aged micas within the Meguma Zone underlying the Grand Banks were totally reset by Alleghenian reactivation of the zone, a feature which occurs extensively in Nova Scotia. The addition of Acadian-aged micas in the middle Eocene sample may reflect a change in sediment provenance as drainage systems unrelated to rift topography developed. With the exception of one clast dated at 186 Ma, the 12 other micas obtained from the upper Paleocene sample yielded ages between 55 and 74 Ma, with 7 falling within ±2 m.y. of the 57-Ma age of the sample indicated by the biostratigraphic age-depth plot for Site 1276. This, together with the volcaniclastic content of the sample, indicates an input from near-contemporaneous volcanism. The nearest known occurrences of near-contemporaneous late Paleocene volcanism that could have produced white micas are in Greenland and Portugal, some 2000 and 1500 km distant, respectively, from Site 1276 during the Paleocene. However, ages of volcanism in these areas indicate that they could probably not be sources of micas younger than 60 m.y., which suggests some as-yet unknown volcanic source in the North Atlantic area. Accumulation in the Grand Banks area of airborne-transported volcaniclastic material from eruptions of slightly different ages, followed by a single resedimentation event, could account for the spread of dates obtained from the sample. White micas from the lowermost Albian sample show a spread of ages between 37 and 284 Ma that is completely different from the age distribution pattern of the middle Albian and middle Eocene samples. The sample location is between, and at least 25 m above and below, two igneous sills dated at 98 and 105 Ma. The sills have narrow thermal aureoles and ages older than the youngest detrital micas in the sample. It is unlikely, therefore, that the spread of mica ages in the sample is due to partial resetting of ages caused by thermal effects associated with the intrusion of the sills. The resetting may have been associated with a longer lived thermal event.

Abundance of copepods from multinet samples during POLARSTERN cruise ANT-XX/1

Abundance and species composition of copepods were studied during the expedition ANT XXI/1 on a latitudinal transect in the eastern Atlantic from 34°49.5' N to 27°28.1' S between 2-20 November 2002. Stratified zooplankton tows were carried out at 19 stations with a multiple opening-closing net between 300 m water depth and the surface. Cyclopoid and calanoid copepods showed similar patterns of distribution and abundance. Oithona was the most abundant cyclopoid genus, followed by Oncaea. A total of 149 calanoid copepod species were identified. Clausocalanus was by far the most abundant genus, comprising on average about 45% of all calanoids, followed by Calocalanus (13%), Delibus (9%), Paracalanus (6%), and Pleuromamma (5%). All other genera comprised on average less than 5% each, with 40 genera less than 1%. The calanoid copepod communities were distinguished broadly in accordance with sea surface temperature, separating the subtropical from the tropical stations, and were largely determined by variation in species composition and species abundance. Nine Clausocalanus species were identified. The most numerous Clausocalanus species was C. furcatus, which on average comprised half of all adult of this genus. C. pergens, C. paululus, and C. jobei, contributed an average of 19%, 9%, and 9%, respectively. The Clausocalanus species differed markedly in their horizontal and vertical distributions: C. furcatus, C. jobei, and C. mastigophorus had widespread distributions and inhabited the upper water layers. Major differences between the species were found in abundance. C. paululus and C. arcuicornis were biantitropical and were absent or occurred in very low numbers in the equatorial zone. C. parapergens was found at all stations and showed a bimodal distribution pattern with maxima in the subtropics. C. pergens occurred in higher numbers only at the southern stations, where it replaced C. furcatus in dominance. In contrast to the widespread species, the bulk of the C. paululus, C. arcuicornis, C. parapergens, and C. pergens populations was concentrated in the colder, deeper water layers below the thermocline, thereby avoiding the warm surface waters. C. lividus was found only at the most northern and C. ingens only at the most southern stations. Both species were found almost exclusively in the upper 50 m. The distinct differences in abundance and horizontal and vertical distribution suggest a strong ecological differentiation among the Clausocalanus species.

Dinoflagellate cyst species composition of recent surface samples (Appendix)

Dinoflagellate cysts and other organic-walled microfossils have been studied in recent surface sediments from the entire Norwegian-Greenland Sea. More than 30 taxa have been recognized, of which only few show a distinct distribution pattern, and allow description of four assemblages. The occurrence of most taxa is related to the relatively warmer waters of the Norwegian Sea. Algidaspaeridium? minutum s.1., Brigantedinium simplex and Impagidinium? pallidum are the only species showing a preference for colder water masses. Two species, I.? pallidum and Nematosphaeropsis labyrinthus are mainly restricted to the oceanic environment, whereas the other species have also been reported from neritic environments in previous studies. Due to the limited knowledge of the ecological and sedimentological factors influencing the occurrence of dinoflagellate cysts in oceanic environments, their distribution in recent sediments can be only related to surface water masses in a broad sense. Although the distribution of assemblages correlates with specific surface water masses, comparison with assemblages recovered from sediment traps deployed basinwide in the Norwegian-Greenland Sea (Dale and Dale, 1992) revealed some major discrepancies in species composition and percentage abundances. The differences cannot be explained with certainty at the moment, although there is some evidence that transport of dinoflagellate cysts and other fossilizable microplankton in water masses by currents, in sea-ice and sediments may modify the assemblages found in recent oceanic surface sediments from the Norwegian-Greenland Sea.

Paleotemperature reconstructions of the Atlantic Sector of the Southern Ocean

Diatom assemblages from ODP Leg 177 sites 1093, 1094 and core PS2089-2, from the present Antarctic sea ice free zone and close to the Polar Front, were analyzed in order to reconstruct the climate development around the Mid-Brunhes Event 400 000 yr ago, as reflected by summer sea surface temperature (SSST) and sea ice distribution. Dense sample spacing allows a mean temporal resolution during Marine Isotope Stage (MIS) 11 (423-362 ka) of 300-400 yr. SSST values were estimated from diatom assemblages using a transfer function technique. The distribution pattern of sea ice diatoms indicates that the present-day ice free Antarctic Zone was seasonally covered by sea ice during the cold MIS 12 and MIS 10. These glacial periods are characterized by sea ice fluctuations with a periodicity of 3 and 1.85 kyr, suggesting the occurrence of Dansgaard-Oeschger-style millennial-scale oscillations in the Atlantic sector of the Southern Ocean during the glacial stages MIS 12 and MIS 10. Termination V (MIS 12/11) is characterized by a distinct temperature increase of 4-6°C, intersected especially at the southern site 1094 and core PS2089-2 by two distinct cooling events reminiscent of the Younger Dryas, which are associated with a northward shift of the winter sea ice edge in the Antarctic Zone. The SSST record is characterized by distinct temperature intervals bounded by stepwise, rapid changes. Maximum temperatures were reached during Termination V and the early MIS 11, exceeding modern values by 2°C over a period of 8 kyr. This pattern indicates a very early response of the Southern Ocean to global climate on Milankovitch-driven climate variability. The SSST optimum is marked by millennial-scale temperature oscillations with an amplitude of ca. 1°C and periodicities of ca. 1.85 and 1.47 kyr, probably reflecting changes in the ocean circulation system. The SSSTs during the MIS 11 temperature optimum do not exceed values obtained from other interglacial optima such as the early periods of MIS 5 or MIS 1 from the Antarctic Zone. However, the total duration of the warmest period was distinctly longer than observed from other interglacials. The comparison of the South Atlantic climate record with a high-resolution record from ODP Leg 162, site 980from the North Atlantic shows a strong conformity in the climate development during the studied time interval.