Zooplankton Feeding Ecology: Contents of Fecal Pellets of the Cyclopoid Copepods Oncaea venusta, Corycaeus amazonicus, Oithona plumifera, and O. simplex from the Northern Gulf of Mexico

Abstract. In situ feeding habits of the cyclopoid copepods Oncaea venusta, Corycaeus amazonicus, Oithona plumifera , and O. simplex were investigated by scanning electron microscope examination of fecal pellets, the contents of which reflected copepod gut contents upon capture. Peilet contents were compared with assemblages of phytoplankton present in surface waters at times of copepod collection. All samples were from the northern Gulf of Mexico. All four copepods fed upon phytoplankton and O. venusta also ingested other crustaceans. Dominant components of fecal pellets generally did not mirror those of available phytoplankton assemblages. In some cases, O. venusta ingested primarily larger-sized particles even when these were not most abundant, and in other cases it did not ingest large cells even when they were present in bloom concentrations. The presence of small (< 2–5 urn diameter) centric diatoms in O. venusta pellets suggests the possibility of feeding by mechanisms other than suspension or raptorial feeding. Limited observations suggest that C. amazonicus and O. plumifera may feed raptorially on larger particles even when these are not particularly abundant, and that the small O. simplex (< 500 nm total length) feeds mainly upon nanoplankton. It appears that cyclopoid feeding mechanisms are complex, and likely more so than those of many calanoids.     

膨润土颗粒混合物的堆积性质与水-力特性研究进展

膨润土颗粒混合物是高放废物深地质处置库中的一种缓冲/回填材料,掌握其堆积性质与水-力特性是开展处置库安全性能评估的关键基础。本文全面回顾和总结了近年来国内外学者对膨润土颗粒混合物的堆积性质、持水特性、结构特征、渗透特性、胀缩特性及本构模型等方面的研究进展与取得的成果,展望了几个值得进一步研究的问题。结果表明,颗粒混合物的堆积性质与粒径级配密切相关;湿化过程中,颗粒混合物由初始松散结构逐渐转变为胶结融合结构,孔隙结构逐渐趋于均一化,并伴随着颗粒破碎和错动,进而影响其水-力特性。考虑到处置库实际运营环境的复杂性,颗粒混合物的原位填充技术以及多场(热-水-力-化)耦合条件下颗粒混合物的水-力特性是今后值得深入研究的方向。     

粉末压片制样-X射线荧光光谱法测定锂云母中的高含量氟

锂云母中的氟含量很高(1. 36%～8. 71%),在焙烧锂云母矿物时锂的浸出率随着含氟量的增加而逐步下降,随着锂云母脱氟率的提高,锂的浸出率也相应提高,准确测定锂云母中的氟、控制氟含量可为确定焙烧过程的工艺条件、设备参数及成本提供依据。目前氟的测定主要采用离子选择电极法,但过程复杂、分析时间长且空白值高。本文采用粉末直接压片制样X射线荧光光谱法测定锂云母中的氟,氟的检出限为46±4μg/g。将锂矿石标准物质和人工配制校准物质制成工作曲线,经验系数校正基体效应和谱线干扰,方法精密度(RSD,n=10)为1. 03%。采用本法分析由标准样品合成的样品,测定值与理论值吻合良好;用实际样品验证,测定结果与离子选择电极法的测定值相符。本法适用于分析锂云母中0. 68%～9. 14%的氟。     

Zooplankton Feeding Ecology: Contents of Fecal Pellets of the Copepods Acartia tonsa and Labidocera aestiva from Continental Shelf Waters Near the Mouth of the Mississippi River

Abstract. Feeding habits of adult female Acartia tonsa and Labidocera aestiva and L. aestiva CV copepodites were examined by comparing fecal pellet contents and available phytoplankton. Samples were collected from eight stations in the northern Gulf of Mexico near the mouth of the Mississippi River. Fecal pellets of both copepods contained remains of a wide variety of chain-forming and solitary phytoplankters of various sizes, as well as remains of other crustaceans. Contents of fecal pellets generally mirrored the composition and relative abundance of fluctuating assemblages of available natural phytoplankton. Both species fed upon a wide size range of cells, from solitary centric diatoms of 2–8 um diameter up to large solitary centrics of 33–53 urn diameter. Both copepods also ingested the elongate solitary pennate diatom Thalassiothrix sp. (264–330 urn long) and chain-forming diatoms such as Skeletonema costatum. Remains of large or chain-forming diatoms and crustaceans were more dominant in fecal pellets of L. aestiva. This suggests that L. aestiva is primarily a raptorial feeder, grasping larger particles while A. tonsa is a more typical suspension feeder. Both copepods are opportunistic omnivores, however, and there is considerable overlap in their diets.     

Persistent organic pollutants carried by synthetic polymers in the ocean environment

Thermoplastic resin pellets are melted and formed into an enormous number of inexpensive consumer goods, many of which are discarded after a relatively short period of use, dropped haphazardly onto watersheds and then make their way to the ocean where some get ingested by marine life. In 2003 and 2004 pre-production thermoplastic resin pellets and post-consumer plastic fragments were collected and analyzed for contamination for persistent organic pollutants (POPs). Samples were taken from the North Pacific Gyre, and selected sites in California, Hawaii, and from Guadalupe Island, Mexico. The total concentration of PCBs ranged from 27 to 980 ng/g; DDTs from 22 to 7100 ng/g and PAHs from 39 to 1200 ng/g, and aliphatic hydrocarbons from 1.1 to 8600 microg/g. Analytical methods were developed to extract, concentrate and identify POPs that may have accumulated on plastic fragments and plastic pellets. The results of this study confirm that plastic debris is a trap for POPs.     

Occurrence, distribution and characteristics of beached plastic production pellets on the island of Malta (central Mediterranean)

The distribution, abundance and chemical characteristics of plastic production pellets on beaches of the island of Malta have been determined. Pellets were observed at all locations visited and were generally most abundant (>1000 m⁻² at the surface) on the backshores of beaches with a westerly aspect. Most pellets were disc-shaped or flattened cylinders and could be categorised as white, yellow, amber or brown. The polymeric matrix of all pellets analysed by infrared spectroscopy was polyethylene and the degree of yellowing or darkening was associated with an increase in the carbonyl index, hence extent of photo-oxidation or aging. Qualitatively, pellets are similar to those reported for other regions of the Mediterranean in surveys spanning three decades, suggesting that they are a general and persistent characteristic of the region.     

饵料、温度和盐度对两种海洋桡足类摄食与排粪的影响

中华哲水蚤是中国近海典型的浮游桡足类,猛水蚤是青岛胶州湾和汇泉湾常见底栖桡足类,研究2种海洋桡足类的摄食和排粪规律可为大量培养桡足类提供最佳条件。论文研究了在6种不同饵料(球等鞭金藻、亚心形扁藻、小球藻、绿色巴夫藻、三角褐指藻、小新月菱形藻)的条件下,温度和盐度对中华哲水蚤和猛水蚤摄食和排粪的影响。温度和盐度对2种桡足类摄食和排粪的影响具有种间差异性。中华哲水蚤在15℃的摄食率、滤水率和排粪率高于在20和25℃的摄食率、滤水率和排粪率。在15、20和25℃3个温度范围内,猛水蚤的摄食率、滤水率和排粪率随温度升高而升高。在20～36盐度范围内,中华哲水蚤的摄食率、滤水率和排粪率随盐度的升高先升高后降低,在盐度为28时达到最大值,猛水蚤的摄食率、滤水率和排粪率随盐度升高而逐渐降低,猛水蚤摄食和排粪的最适盐度为20。温度和盐度实验均表明,在6种饵料中,亚心形扁藻和球等鞭金藻有利于中华哲水蚤的摄食,球等鞭金藻有利于猛水蚤的摄食,而小球藻对2种桡足类的摄食均不利。     

Zooplankton Feeding Ecology: Contents of Fecal Pellets of the Copepod Anomalocera ornata from Continental Shelf and Slope Waters of the Gulf of Mexico

Abstract. The diet of the copepod Anomalocera ornata was examined by comparing contents of fecal pellets produced on natural diets with assemblages of available phytoplankton. Samples were collected in continental shelf and slope waters of the northern Gulf of Mexico. A wide size and taxonomic array of phytoplankters was ingested, and remains of phytoplankton taxa in fecal pellets reflected the composition of phytoplankton assemblages in the water. Absence of crustacean remains in fecal pellets suggests that A. ornata feeds primarily as an opportunistic grazer.     

饵料浓度对中华哲水蚤摄食的影响

用饵料浓度差减法和排粪率法研究中华哲水蚤(Calanus sinicus)在饵料(青岛大扁藻、新月菱形藻)浓度从1500到350000个/cm3时摄食率的变化。实验证明中华哲水蚤具有很强的摄食潜力,摄食率在实验饵料浓度范围内一直在增加,在较低的饵料浓度(如青岛大扁藻4000个/cm3)下停止摄食。     

Zooplankton Feeding Ecology: Contents of Fecal Pellets of the Copepod Undinula vulgaris from Continental Shelf Waters of the Gulf of Mexico

Abstract. The in situ diet of the copepod Undinula vulgaris was examined by comparing contents of fecal pellets produced on natural food with assemblages of available phytoplankton. Samples were collected in continental shelf waters of the northern Gulf of Mexico. U. vulgaris was an indiscrimi-nant suspension feeder, ingesting a broad size, shape, and taxonomic array of phytoplankters. Contents of fecal pellets generally matched those of available phytoplankton assemblages. The presence within the same fecal pellets of remains of microplankters ranging over two orders of magnitude in longest dimension suggests that feeding is nonselective, and that U. vulgaris may rapidly switch between several modes of feeding.