北部湾海域小型底栖动物丰度和生物量

根据2008年10月4日至8日北部湾海域生态环境综合调查资料,对北部湾海域小型底栖动物的类群组成、丰度和生物量分布进行了分析研究,结果表明,研究海域的小型底栖动物平均丰度约为399.09±452.20 had·10cm^-2,平均生物量约为359.56±324.45μg·10cm^-2;按丰度来讲,分选出的14个类群中,自由生活海洋线虫的丰度为最优势,约占总丰度的92.69%,其次为底栖桡足类和多毛类,分别约占总丰度的3.28%和2.47%;线虫、多毛类和桡足类分别约占总生物量的41.16%、38.34%和6.76%。研究海域的钦州、防城港市沿岸海区小型底栖动物平均丰度相对较高,其平均丰度约为614.98±799.63 ind·10cm^-2;涠洲岛周边海区和北海南部近岸海区平均丰度分别约为481.68±240.03 ind·10cm^-2和278.14±126.38 ind·10cm^-2;对照海区的小型底栖动物平均丰度约仅有197.37±116.72 ind·10cm^-2。根据各站位小型底栖生物的种类组成及其丰度进行了多样性分析,各站位丰富度指数介于0.466～1.516之间,均匀度指数介于0.203～1.13之间,Shannon-Weiner指数(H')介于0.141～0.783之间。根据类群组成及其丰度进行组平均法聚类分析,把研究海区各站位分成了3个不同的底栖生物群落。研究海区线虫和桡足类丰度的比率变化范围在5.02～223.83之间。     

The Impact of Chemical Compounds on Benthic Invertebrates from the Danube and Danube Delta Systems

The aim of this study is to assess freshwater sediment in terms of biological and preliminary toxicological control linked to a series of variables along the Danube River and Danube Delta systems. The research is focused on eight points of the Romanian sector in the summer to autumn of 2012. Results show a high concentration of metals, pesticides, and petroleum products in sediment samples in the monitored period. The survey is designed to gauge the total chemical pollution effects on the composition, living, and growth of benthic organisms. To assess the toxic hazard of contaminated sediment samples, a microbiotest with meiobenthic ostracods Heterocypris incongruens was performed with evaluation of mortality and growth-inhibition percentages. The preliminary results showed an increase of sediment toxicity, in terms of growth inhibition (>80%), especially at Murighiol and Ivancea. The chemical pressures alongside the temporal conditions were important variables which affected benthic communities. Low benthic diversity was found in the Isaccea–St. Gheorghe Branch sector of the Danube River. In terms of ecological status, the study reveals that the Danube and Danube Delta ecosystem are eutrophic systems equilibrated for good ecological status.     

Meiobenthic naidid and aeolosomatid oligochaetes from the profundal zone,and relations of species to eutrophication

Oligochaetes were sampled using meiobenthos methods from depths of between 20 and 94 m in Lake Päijänne in 1986. Individuals belonging to several species of the Naididae and Aeolosomatidae, which are generally considered to include mainly littoral or lotic species, were found more or less regularly at these profundal depths. The naidid species Chaetogaster langi and Amphichaeta leydigii were more abundant in the deepest areas than at 20 m. Species also appeared to react differently to water quality. The naidid species Chaetogaster langi and the aeolosomatid species Aeolosoma quaternarium, A. hemprichi and Rheomorpha neiswestnovae were most abundant on average at oligotrophic, unpolluted stations, naidid species Amphichaeta leydigii, Specaria josinae and Vejdovskyella comata were more abundant at eutrophicated stations and Dero digitata was more abundant in organically loaded areas. The observations of Amphichaeta leydigii, Chaetogaster setosus and Rheomorpha neiswestnovae were new for Finland.     

A new species of Peltidium Philippi, 1839 (Crustacea,Copepoda, Harpacticoida) from the Pacific coast of Mexico

During the analysis of phytal meiobenthic samples collected from a rocky-sandy beach in the state of Nayarit, in the Mexican Pacific, several specimens of harpacticoid copepods were obtained and taxonomically examined. These specimens were found to represent an undescribed species of the peltidiid genus Peltidium Philippi, 1839. The new species, Peltidium nayarit sp. n. is described herein. It resembles Peltidium nichollsi Geddes and Peltidium lerneri Geddes from Bahamas but also the widespread Peltidium speciosum Thompson & Scott and Peltidium purpureum Philippi. The new species from the Mexican Pacific differs from its known congeners by its possession of a unique combination of characters, including a modified pectinate seta on the antennary exopod, three terminal setae on the second endopodal segment of leg 1, third exopodal segment of leg 1 with three elements, inner terminal claw twice as long as outer claw, female fifth leg with 5 exopodal setae, exopodal setae I-III stout, spinulose and seta IV being as long as seta V. This is the second species of the family known to be distributed in the Eastern Tropical Pacific and in Mexico. Pending additional data, the distribution of this species appears to be restricted to this area of the Mexican Pacific.     

Seasonal patterns of reproductive activities among deep-sea benthic copepod species in the bathyal Sagami Bay, central Japan

Little is known about the life histories of the deep-sea metazoan meiobenthos. At a bathyal site (depth 1430 m) in Sagami Bay, central Japan, temporal changes in abundance and reproductive activity of deep-sea benthic copepods were investigated for eight abundant species that composed about 50% of total individuals, based on samples collected before fresh organic matter increased in the sediment (December 1996 and 1997), 1 month thereafter (June 1997 and May 1998), and a few months after the event (August 1997 and 1998). Densities of adults of these species fluctuated among samples (the total abundance was 5–30 individuals/10 cm²), but did not show any seasonal trend. Strong evidence for competitive relationships among species could not be detected, and there was no significant negative correlation in abundance between any species pair. The percentage of ovigerous females among total adult females of Schizopera sp. 1 differed significantly by month. Furthermore, the adult sex ratio of the species appeared to fluctuate temporally. These suggest a temporal change in reproductive activity and synchronized growth of Schizopera sp. 1. There was no temporal trend, however, in any parameter for the other species. Mean egg number per brood and egg diameter differed among species, but did not change seasonally in any species. Our study suggests the rarity of seasonal breeding species among the deep-sea benthic copepods, one of the major metazoan meiofaunal groups, as well as among other macro-megafaunal metazoans.     

Is there competition among ciliates and nematodes?

1. Biotic interaction between the ciliate Cyclidium glaucoma and the nematode Caenorhabditis elegans was investigated by manipulating the densities of the organisms in microcosms with and without sediment. 2. After 11 days the abundance of ciliates, nematodes and bacteria as well as extracellular enzyme activity were determined. Ciliates had a negative effect on nematode abundance in microcosms without sediment and in microcosms with sandy sediment, whereas in muddy sediment the effect was less distinctive. An effect of nematodes on ciliates was not observed. 3. The common resource bacteria were not affected negatively by the activity of the grazers. Overall grazer biomass increased with the addition of sediment to the microcosms, suggesting a rise of the carrying capacity in the experimental system. Especially in muddy sediment the abundance of bacteria and extracellular enzyme activity was higher compared to the microcosms without sediment. 4. The results of the experiment suggest a strong interspecific competition between nematodes and ciliates, where nematodes are, at least temporary, strongly affected.     

珠江口伶仃洋海域小型底栖生物丰度和生物量

分别于2006年7-8月(夏)、2007年4月(春)和10月(秋)对珠江口伶仃洋附近海域小型底栖生物丰度和生物量进行调查.3个航次共鉴定小型底栖生物类群15类,包括线虫、桡足类、多毛类、介形类、动吻动物、端足类、颚咽动物、涟虫、纽虫、腹足类、双壳类、星虫、螠虫、原足类和其他未鉴定种类;春、夏、秋3个航次小型底栖生物丰度分别为(272.1+281.9)、(165.1±147.1)和(246.4±369.3) ind·10 cm-2,线虫为主要优势类群,分别占小型底栖生物总丰度的86.8％、83.5％和93.4％.小型底栖生物丰度垂直分布不均匀,分布于沉积物0～2 cm、2～5 cm、5～10 cm的数量比例分别为54.1％、35.2％和10.8％,线虫分布于沉积物0～5 cm数量比例为87.4％;春、夏、秋3个航次小型底栖生物生物量分别为(374.6±346.9)、(274.1±352.2)和(270.8±396.0) μg·10 cm-2,多毛类平均生物量最高,分别占小型底栖生物总生物量的30.1％、46.7％和46.0％,其次为线虫(25.2％、20.1％和34.0％)和介形类(20.6％、15.3％和14.8％).伶仃洋小型底栖生物丰度平面分布呈现从北向南升高、东部高于西部的趋势.伶仃洋小型底栖生物丰度、生物量分布与水深呈显著正相关.     

Where Turbellaria? Concerning knowledge and ignorance of marine turbellarian ecology

Present knowledge of marine free-living turbellarians is reviewed in the light of a standard ecological text. Little is known of their ecological adaptations or fitness but they are clearly successful animals. Diversity within communities can be considerable, possibly relating to the small size of individuals and temporal and spatial resource gradients. Little is known about genetic diversity, environmental tolerances and demography. Local distribution patterns are better known but rarely proven with appropriate statistics. New data from work in Northern Ireland on behaviour and habitat choice of Procerodes littoralis and on species richness, population aggregation and microdistribution of meiofaunal turbellarians is presented.Nothing appears known about intra-specific competition but more about inter-specific relationships including responses to biogenic structures. Dietary information is sparse and mostly observational with little known about feeding efficiency. Studies at Sylt have revealed mainly univoltine or polyvoltine annual life cycles partly related to habitat preference and possibly giving some evidence of r and K selection. Factors controlling local abundance are largely uninvestigated and the reasons for the apparent rarity of many species not understood.Lists and counts of turbellarians within particular habitats provide some knowledge of community structure but very few numerical analyses, e.g. of diversity and similarity, exist. Contribution to energy flux and to structuring communities has not been determined in spite of the turbellarians' assumed major role as meiofaunal predators. Nevertheless marine turbellarians appear particularly fitted to studies such as habitat heterogeneity, community stability and biogeography and are surely suitable subjects for field and laboratory experiments. There is no lack of direction for studies to proceed. Impulsion is required.     

A re-evaluation of marine nematode productivity

Nematodes are the most abundant multicellular animals in marine sediments but their role in the benthos has not been properly quantified yet. In nearly all energy-flow budgets of marine systems their annual production P is given as about nine times their mean biomass B and their part in the total energy-flow is consequently estimated as anywhere between 3 and 30% of the total (carbon) input in the benthic system. Our laboratory experiments demonstrate that nematode productivity is much higher than P/B 9 per year and may reach values of over 60 for bacterial grazers. To obtain more reliable estimates for field populations we propose a regression equation relating egg-to-egg development time T_min to temperature (t) and adult female weight (W in µg wet weight):log T_min = 2.202–0.0461 t + 0.627 log W. When multiplied by the constant biomass turnover per generation (P/B)_gen = 3, development rate 1/T_min is a good predictor of daily P/B. This method was applied to two series of field data. A rather stable community from a sublittoral mud in the North Sea had an annual P/B = 20. A less stable Aufwuchs community from Sargassum in Japan had an annual P/B = 58.     

Problems in meiofauna energy-flow studies

The direct estimation of energy flow through marine meiobenthic populations poses several difficulties, mainly relating to sampling problems. The usefulness of some indirect estimation methods is discussed.Direct production estimates and respiration measurements for three brackish water crustacean populations are given, indicating a relative constant proportion between population production and respiration. The production: assimilation ratio for these populations fluctuates between 0.3 and 0.4. This is contrasted to literature data revealing much higher production: assimilation ratios as determined in the laboratory for nematode populations. Using data on laboratory cultures of the nematode Monhystera disjuncta some factors that can possibly generate this discrepancy are discussed. An analysis of P:B in different life stages of this population justifies the use of a life-cycle turnover of about 3 for meiobenthic populations, provided some conditions are met. Among these is that no drastic change in productivity occurs between juveniles and adults, and that the biomass of hatchlings, not of freshly laid eggs, is considered as generative production.