Mixotrophy is a feeding strategy by which some organisms combine autrotrophic and heterotrophic activities. The seasonal dynamics of the fve most common mixotrophic ciliates were studied monthly in surface layers of the inner and middle zone of the Bahía Blanca estuary, a nutrient-rich, shallow and highly turbid environment in Argentina, from January to December 2009. Temperature, salinity, turbidity and chlorophyll a were recorded, as well as the abundance and biomass of Strombidium capitatum, Strombidium acutum, Cyrtostrombidium sp., Lohmanniella oviformis and Tontonia appendiculariformis. The highest mixotrophic ciliate abundance was recorded during the austral winter (June-July) in the inner zone, meanwhile in the middle zone of the estuary the presence of these ciliates was almost nuil. The highest chlorophyll contribution derived from mixotrophic ciliates to total chlorophyll a ranged from 6% in the inner zone to 23% in the middle zone, both registered in autumn. The low abundance of mixotrophs in the middle zone of the estuary during the winter, as is usually observed in other coastal ecosystems, could be explained through a higher grazing pressure in this zone (top-down control) by mesozooplankton (e.g., copepods) in comparison to the inner zone. The secondary bloom of phytoplankton consistently observed during the last summers dominated by small sized diatoms and nanoplankton phytofagelates, could have sustained the high abundance of mixotrophic ciliates registered in the middle zone in autumn and summer.

Dinámica de los ciliados mixótrofos en dos zonas de un estuario templado y turbio en Sud América, Argentina. La mixotrofía es una estrategia de alimentación por medio de la cual un organismo combina la autotrofa y la heterotrofa. La dinámica estacional de cinco ciliados mixótrofos comúnmente presentes en las aguas superfciales de la zona interna y media del estuario de Bahía Blanca, Argentina, rico en nutrientes, somero y con alta turbidez, se estudió mensualmente desde enero a diciembre de 2009. Se registraron los valores de temperatura, salinidad, turbidez y clorofla a, así como también la abundancia y biomasa de Strombidium capitatum, Strombidium acutum, Cyrtostrombidium sp., Lohmanniella oviformis y Tontonia appendiculariformis. La abundancia más alta de los mixótrofos se registró en el invierno en la zona interna, mientras que en la zona media del estuario la presencia de estos ciliados fue casi nula. La contribución más alta de clorofla proveniente de los mixótrofos a la clorofla a total fue 6% en la zona interna y 23% en la zona media (ambas estimaciones registradas en otoño). La baja abundancia de mixótrofos en la zona media del estuario durante el invierno, como usualmente es observado en otros sistemas costeros, podría ser explicada por una presión de pastoreo elevada en esta zona (control de tipo "top-down") por parte de mesozooplancton (e.g., copépodos), en comparación con la zona interna. La foración secundaria del fitoplancton observada durante los últimos veranos, dominada por diatomeas de pequeño tamaño y ftofagelados del nanoplancton, podría haber sustentado la alta abundancia de ciliados mixótrofos que se registró en la zona media en otoño y verano.

Nystatin is a polyene antibiotic applied on the treatment of topical fungal infections. It can undergo auto-oxidation and thermal degradation and has three known polymorphs called Type A and Type B, which may be interconvertible, and Type C. Previous studies related to the incorporation of Nystatin in bioadhesive films have revealed the presence of polymorph Type C, whereas the results presented in this work, obtained using a different lot, evidenced the presence of only polymorphs A and B with a significant proportion of amorphous phase. To overcome the lack of uniformity between individual commercial Nystatin lots, an adequate physico-chemical characterization is necessary performing prior using it in preformulation works. Solid state characterization techniques were employed.

La Nistatina es un antibiótico poliénico empleado en el tratamiento de infecciones fúngicas. Puede sufrir autooxidación y degradación térmica y presenta tres formas polimórficas denominadas Tipo A y Tipo B, que pueden interconvertirse, y Tipo C. Así, estudios previos referidos a la incorporación de Nistatina en films bioadhesivos revelaron la presencia del polimorfo Tipo C, mientras que los resultados presentados en este trabajo, obtenidos a partir de un lote diferente del fármaco, determinaron la presencia de los polimorfos A y B con una importante proporción de fase amorfa. Estas características del fármaco determinan falta de uniformidad entre diferentes lotes del mismo, por lo tanto es necesario efectuar su caracterización antes del empleo en el desarrollo de medicamentos. Para ello se emplearon diversas técnicas de caracterización de materiales.

O padrão sazonal da comunidade de fitoplâncton-ciliados aloricados é um indicador adequado das relações tróficas e reciclagem de nutrientes nos ambientes costeiros. A abundância, biomassa e composição da comunidade de fitoplâncton-ciliados foram determinadas por classes de tamanho durante um ciclo anual no estuário de Bahía Blanca. Além disso, foram estimadas também a produção e as taxas de excreção de ciliados. Uma floração de diatomáceas no período de fim de inverno e início de primavera foi o acontecimento mais importante do ciclo anual. Para avaliar a significância do tamanho do fitoplâncton em relação ao tamanho dos ciliados, foram determinadas as frações de clorofila de < 25µm e > 25 µm. A fração < 25µm foi dominante. As classes de tamanho dos ciliados determinadas entre< 10³ a > 10(5)µm³foram indicadoras dapresença dediferentes grupos tróficos e, consequentemente, da variedade das suas presas potenciais. Os ciliados pequenos dominaram em abundância e os maiores em biomassa. A abundância total de ciliados variou de 0,2 a 5,2 x 10³ células L-1 e de 0,55 a 83,9 µg C L-1. A concentração de clorofila a total de até 40,4 µg L -1 foi superior às registradas em outros sistemas de estuários em regiões temperadas. Os ciliados menores foram importantes como regeneradores de nitrogênio no verão e na primavera, quando a sua produção estimada foi mais alta. A produção potencial anual de 3 mg C L-1 representa um importante parâmetro de referência na qual possíveis mudanças do status trófico deste ambiente podem ser previstas.

The seasonal pattern of the phytoplankton-aloricate ciliate community is an adequate indicator of trophic coupling and nutrient cycling in coastal environments. The size-fractionated, abundance, biomass and composition of a phytoplankton-aloricate ciliate community were ascertained in the Bahía Blanca Estuary from February 1994 to February 1995. In addition, ciliate production and excretion rates by size class were estimated. A winter-early spring diatom bloom was the most important event in the annual cycle. To evaluate the significance of phytoplankton size in the food web, <25 µm and > 25 µm fractions of chlorophyll a were determined; the < 25 µm fraction was dominant. To classify the ciliate community in trophic groups, it was divided into volume-size classes, from <10³ µm³to > 10(5) µm³; this wide range of size indicated the potential prey. The smaller ciliates dominated abundance but the larger ones dominated biomass. Values of total ciliates, ranging from 0.2 to 5.2 x 10³ cells L-1 and 0.55 to 83.9 µg C L-1, and levels of total chlorophyll a reached 40.4 µg L-1 and were higher than those recorded for other temperate estuarine systems. The smaller ciliates were potentially important as nitrogen regenerators in summer and spring, when their estimated production was highest. The annual potential production of 3 mg C L-1 represents a reference parameter from which possible changes in the trophic status of this environment could be predicted.

The specific composition and abundance variation of the ciliate community from a wastewater discharge zone in the Bahía Blanca estuary, Argentina, were studied all throughout a year, from June 1995 to May 1996. The polluted area exhibited high values of particulate organic matter and nutrients, particularly phosphates. Aloricate ciliates were represented by 15 species belonging to the genera Strombidium Claparède & Lachmann, 1859; Strombidinopsis Kent, 1881; Cyrtostrombidium Lynn & Gilron, 1993; Strobilidium Schewiakoff, 1983; Lohmmanniella Leegaard, 1915 and Tontonia Fauré-Fremiet, 1914. Tintinnids were represented by nine species belonging to the genera Tintinnidium Kent, 1881, Tintinnopsis Stein, 1867 and Codonellopsis Jörgensen, 1924. The total abundance of aloricate ciliates reached a peak of 1,800 ind. 1-1 and the total abundance of tintinnids reached a peak of 9,400 ind. 1-1. Tintinnidium balechi Barría de Cao, 1981 was the most abundant ciliate in the community. Considerations on the presence and abundance of ciliates are made in relation to physicochemical and biochemical parameters.

Seven species of aloricate planktonic ciliates were identified using protargol staining. Choreotrichida: Strombidinopsidae, Strombidinopsis elongata Song & Bradbury, 1998; Strobiliidae, Strobilidium epacrum Lynn & Montagnes, 1988 and Strombidiida: Strombidiidae, Strombidium capitatum (Leegaard, 1915) Kahl, 1932; S. emergens (Leegaard, 1915) Kahl, 1932; S. acutum Leegaard, 1915; S. dalum Lynn, Montagnes & Small, 1988 and Cyrtostrombidium longisomum Lynn & Gilron, 1993; they were collected from the inner zone of the Bahía Blanca estuary in the southern region of the Buenos Aires province, Argentina. These species represent new records to South America (Argentina).