The New Zealand species of Spaniocerca (Plecoptera,notonemourinae) and a generic correction in the notonemourinae

Variability within the genus Spaniocerca has been studied, and as a result S minor Kimmins has been synonymised with S. zelandica Tillyard. S zelandica is redescribed, the larva is figured, notes on ecology are given, and the nature of the variation found is discussed. Notonemoura cowleyi Winterbourn is transferred to Spaniocercoides Kimmins.     

Observations on Chatham Rise currents

New Zealand stream ecosystems differ from many of their North American counterparts, on which general stream ecosystem models are based, in several ways. In New Zealand, large particle detritivores (shredders) are poorly represented, and the dominant invertebrates are browsers which feed on fine particulate organic matter and stone‐surface organic layers. In contrast with the river continuum concept of Vannote et al. (Canadian Journal of Fisheries and Aquatic Sciences 37: 130–137, 1980), representation of functional feeding groups shows little change downstream and a temporal continuum of synchronous species replacements is not found. Many common benthic invertebrates are ecologically flexible species with poorly synchronised life histories. These differences appear to be associated with the non‐retentive, climatically unpredictable nature of the stream environment. The idea that stream communities are highly structured entities is questioned, as is the generality of the river continuum concept.     

Some effects of eutrophication and the removal of aquatic plants by grass carp (Ctenopharyngodon idella) on rainbow trout (Salmo gairdnerii) in Lake Parkinson,New Zealand

Temporary removal of aquatic plants in Lake Parkinson, a small, eutrophic dune lake, resulted in a number of changes to the population of stocked rainbow trout (Salmo gairdnerii). During each summer the lake stratified and low oxygen levels limited the distribution of trout to shallow (0–4 m) surface waters. In the first summer following weed removal the numbers of black shags (Phallacrocorax carbo) counted at the lake increased, and their predation resulted in a decline in trout density. However, the growth rate and condition of the trout population then exceeded that of trout present before weed removal. During the second summer after weed removal a cladoceran bloom was followed by low phytoplankton levels and high ammonia concentrations. A prolonged calm compounded this situation with the result that oxygen levels in bottom and surface waters dropped below 2 ppm. These low oxygen levels eliminated the trout population, but other fish species present survived. Elimination of aquatic plants affected the population dynamics of other fish species in the lake with potential implications for the trout. The experiment demonstrated the importance of weed beds in maintaining a stable fish community in lakes such as Lake Parkinson.     

Food and feeding of small fish in the Rakaia River,New Zealand

Benthic macroinvertebrates and fish species were collected at monthly intervals during a 12‐month period, from 3 areas of the lower Rakaia River. The composition and abundance of the benthos and stomach contents of the fish were analysed for seasonal trends, food niche breadth and overlap between pairs of fish species, and overlap between the benthos and the diet of each fish species. The diets of bluegilled bully (Gobiomorphus hubbsi), upland bully (G. breviceps), juvenile longfinned eel (Anguilla dieffenbachii), Galaxias brevipinnis, G. paucispondylus, and juvenile brown trout (Salmo trutta) were similar to the proportions of prey species in the benthos. Deleatidium and chironomid larvae dominated the benthos in all seasons and formed the majority of food items in the diet of these species. Food niche overlap between these species was high, indicating potential competition, but preferred habitat and feeding habit differences plus low fish population density and abundance of main prey items probably eliminate the occurrence of any serious competition. The diet of the other fish species differed from this pattern. The common bully (Gobiomorphus cotidianus) ate proportionally more chironomid larvae and fish eggs than occurred in the benthos; torrentfish (Cheimarrichthys fosteri) ate proportionally more chironomid larvae than occurred in the benthos; and quinnat salmon (Oncorhynchus tshawytscha) depended largely upon prey species of terrestial origin, such as adult Deleatidium and dipterans.     

Uptake of palytoxin‐like compounds by shellfish fed Ostreopsis siamensis (Dinophyceae)

Abstract

Greenshell? mussels (Perna canaliculus Gmelin), scallops (Pecten novaezealandiae Reeve), and Pacific oysters (Crassostrea gigas Thunberg) were fed with a New Zealand strain of mass cultured Ostreopsis siamensis Schmidt (for 27 and 84 h and with 1.5 × 10⁶ or 8.6 × 10⁶ cells, respectively) under laboratory conditions. The microalgal cells contained 0.3 pg palytoxin equivalents cell^–1 (as determined by the haemolysis neutralisation assay (HNA) of Bignami (1993)) and extracts of these cells were toxic to mice after intraperitoneal injection. No palytoxin‐like material was detected either in the hepatopancreas or the muscle and roe of mussels fed O. siamensis. Oysters contained detectable amounts of toxin in hepatopancreas muscle, and roe while higher concentrations were present in the hepatopancreas of scallops. Extracts of control shellfish (tested biotoxin free and not fed O. siamensis) were toxic to mice, and there was no definitive evidence that feeding shellfish with O. siamensis at the levels employed in the present experiment increased the toxicity of shellfish tissue extracts to mice.     

微型异养鞭毛虫摄食选择性的研究进展

微型异养鞭毛虫(HNF)是海洋微微型浮游生物的重要摄食者,通过摄食作用对后者的种类(或类群)组成、粒径分布、数量结构和营养价值等属性具有重要的影响,而这与HNF的摄食选择性有直接关系。对HNF摄食选择性的研究有助于深入了解HNF在海洋微食物环乃至整个海洋生态系统中的作用。就国际上已开展的HNF摄食选择性相关研究进行了回顾,分析和总结了影响HNF选择性摄食的关键因素,如食物大小、游动性、营养价值及食物细胞表面的生化结构特征等,并重点介绍了HNF摄食选择性形成的主要机制以及HNF的选择性摄食在调节海洋微微型浮游生物群落结构中的作用。     

黄海夏季沙海蜇食物需求的估算方法及应用

自20世纪90年代末起,沙海蜇频繁暴发于东亚海域,特别是8、9月份为黄海沙海蜇生物量的高峰期/大量暴发期。研究沙海蜇的大量出现对所在生态系统的影响十分必要,最直接的影响表现在对饵料生物浮游动物的影响。本文研究了黄海2006和2007年8、9月份沙海蜇的呼吸率、摄食率,估算了沙海蜇的食物需求量及其在黄海的分布格局,获得了其每天对中、大型浮游动物现存量及生产力的潜在摄食压力。结果表明沙海蜇的食物需求量的分布格局与其生物量的分布格局一致。在沙海蜇的捕获率为最大时,2006年9月上旬沙海蜇的摄食率为47.84(0.7—215.05)mg C/(m2d)。假设中、大型浮游动物都可以作为沙海蜇的摄食对象,那么每天对中、大型浮游动物现存量及生产力的摄食压力平均分别为6.4%(0.09%—28.79%)和76.61%(1.12%—344.28%)。2006年9月下旬及2007年8月沙海蜇的食物需求比2009年9月上旬有所降低。因此,沙海蜇在暴发期间对中、大型浮游动物潜在的消耗非常大,甚至是毁灭性的。尤其是沙海蜇在高生物量站位对浮游动物的食物需求非常高,沙海蜇对浮游动物的摄食压力远超过了浮游动物本身的生产力(大于100%),这时的浮游动物远远不能满足沙海蜇的食物需求。本文的研究结果为探讨沙海蜇暴发对黄海浮游生态系统的影响程度提供了基础资料。     

香港巨牡蛎对3种浮游植物摄食率和滤清率的研究

本文在室内条件下研究了大、中、小3种规格的香港巨牡蛎（Crassostrea hongkongensis）对牟氏角毛藻（Chaetoceros muelleri）、亚心形扁藻（Platymonas subcordiformis）、球等鞭藻（Isochrysis galbana）3种浮游植物在同等密度、同等生物量条件下的摄食率和滤清率,探讨了香港巨牡蛎对3种浮游植物的摄食差异及其影响因素。结果表明,在28℃水温条件下,香港巨牡蛎的单位个体滤清率和单位体质量滤清率分别为1.40~8.94 L/（ind·h）和0.86~3.17 L/（g·h）,等密度和等生物量浮游植物条件下香港巨牡蛎均表现出单位个体滤清率由高到低依次为:大规格、中规格、小规格;不同规格香港巨牡蛎的单位体质量滤清率相近。相同藻类密度条件下,香港巨牡蛎的单位体质量滤清率由高到低依次为:亚心形扁藻、球等鞭金藻、牟氏角毛藻;相同生物量条件下,香港巨牡蛎对3种浮游植物单位体质量滤清率由高到低依次为:球等鞭金藻、亚心形扁藻、牟氏角毛藻。香港巨牡蛎对不同浮游植物种类和密度的滤清率、摄食率差异主要是受饵料的大小、营养质量和密度等因素影响。     

饵料浓度、温度对缢蛏能量代谢的影响

本文以缢蛏（Sinonovacula constricta）为实验对象,使用实验室静水法,研究其在不同饵料浓度、温度梯度下的代谢情况,测定其摄食、呼吸、排粪、排泄等生理参数,并根据能量平衡原理估算了缢蛏的能量收支情况。结果表明:（1）缢蛏的摄食能、呼吸能、排泄能随饵料浓度的上升而增加;随着温度的变化,其摄食能呈峰值性改变,呼吸能和排泄能有缓慢增长趋势;（2）缢蛏从球等鞭金藻（Isochrysis sphaeric）中摄取的有机碳源主要通过呼吸代谢消耗,以粪便的形式排出,少部分随排泄代谢产物流出,余下的碳主要用作贝类自身的生长;（3）单因素方差分析表明,饵料浓度和温度均显著影响缢蛏的摄食率和耗氧率（P<0.05）,温度为23℃时,缢蛏的摄食率和耗氧率在饵料浓度为3.0×105 cells/mL时达到最高;饵料浓度为3.0×105 cells/mL时,缢蛏的摄食率在23℃时达到最大值,而耗氧率和排氨率在31℃时达到最高。     

Feeding of European cisco (Coregonus albula and C. lucinensis) on the glacial relict crustacean Mysis relicta in Lake Breiter Luzin (Germany)

Lake Breiter Luzin, located in north-eastern Germany, is known for the rare occurrence of sympatric populations of European cisco, Coregonus albula and C. lucinensis. Moreover, the lake is inhabited by the glacial relict crustacean Mysis relicta, currently found in only three other lakes in Germany. In the present study, the role of M. relicta in the diet of ciscoes was investigated. Between 2001 and 2002 ciscoes, mysids and zooplankton were caught in Lake Breiter Luzin and stomach contents of ciscoes were analysed. There were seasonal changes in the food items in the stomachs, largely reflecting changes in prey availability. The main food items were copepods (45–81%) and mysids (5–26%). Cladocerans had high amounts in the diet only in summer. Seasonal changes in selectivity were also noted for most prey groups. There were also some consistent patterns of prey preference, with an overall preference for mysids. In general, the prey composition in cisco stomachs did not show significant diet changes, but there were some significant differences between day and night feeding in single prey groups, such as cladocerans. Diet composition of ciscoes varied with the different depth strata in which the fish were caught. With increasing depth, the proportion of mysids in the diet significantly increased, whereas that of copepods significantly decreased. Between C. albula and C. lucinensis, no distinct differences in feeding were evident. Mysids provided an additional and important food resource to ciscoes, and were mainly consumed when the availability of other prey organisms decreased, as in autumn and in the deeper strata of the water column. However, mysids preyed on the same food organisms as ciscoes, indicating a strong competition for food between fish and mysids.