The distribution of meiofauna on back‐reef sandy platforms in the Maldives (Indian Ocean)

The Maldivian archipelago comprises some of the most characteristic and significant world atoll systems, but the meiobenthic assemblages of these islands continue to be largely unknown. To investigate variations in meiofaunal spatial distribution and biodiversity in back‐reef platforms, three transects were studied, two at Felidhoo (the north and east sides) and one at South Malé. The sedimentological features of the samples obtained were also analyzed to further current knowledge on the relationships that exist between sediments and meiofauna. Our results reveal that the meiofaunal assemblage at these locations is well diversified and includes 20 major taxa. Nematodes and copepods are dominant, together forming 68% of the total meiofauna, followed by platyhelminthes, polychaetes and ostracods. The nematode assemblage is very rich and composed of 34 families and 123 genera – 96 of which (78%) set new records for the Maldives. The structures of the meiofaunal and nematode assemblages are relatively similar on the ‘large‐scale’ level (i.e. when the different platforms are compared) and reveal a low β‐diversity. However, significant dissimilarities were detected within each platform, emphasizing that such ‘small‐scale’ differences are the main factors determining the structure of the meiofauna and, in particular, the nematode assemblages. Although significant differences were not detected between the transects, greater levels of dissimilarity were recognized at North Felidhoo. Here, the building of inclined deposit layers plays a significant role in increasing the heterogeneity of the platform habitats and sediments, confirming the great importance of sediment granulometry as an environmental variable. Indeed, a close relationship is observed between meiofauna (especially for the nematodes) and grain size, which appears to control the structure, diversity and trophic composition of the Maldivian meiofauna assemblages, thus highlighting the high biodiversity existing in the medium‐coarse sands.     

虾池小型底栖动物的数量研究

提出１９８７年５月至１０月在黄岛养虾池对虾生长周期内对小型底栖动物数量逐月调查。指出：小型底栖动物总平均密度为１０９２．４ｉｎｄｓ·１０ｃｍ－２，自由生活海洋线虫和底栖桡足类是主要类群，其总平均密度分别为４６６．９和４５７．９ｉｎｄｓ·１０ｃｍ－２。８９．７％的小型底栖动物分布在沉积物表层２ｃｍ内。结果指明小型底栖动物被对虾捕食，并提出了捕食模式。     

Monothalamous Soft-Shelled Foraminifera at an Abyssal Site in the North Pacific: A Preliminary Report

Soft-shelled monothalamous foraminifera, including species belonging to the suborders Allogromiida and Astrorhizida (families Saccamminidae and Psammosphaeridae), are an abundant and diverse component of the meiofauna in the deep NE Atlantic but have never been systematically documented in the Pacific Ocean. We examined the 32–63 µm and >63 µm fractions of a sample (0–1 cm layer, surface area 52.8 cm²) from an abyssal plain in the subarctic North Pacific, close to the Aleutian Trench (48°05.43 N, 176°55.06 E; 5289 m water depth). The residues yielded an estimated 2876 stained foraminifera (=545 per 10 cm²) of which >75% occurred in the upper 0.5 cm layer and almost half in the 32–63 µm fraction. Rather less than a third (30.5%) of individuals, and about half of the morphospecies (56 out of 121), were soft-shelled monothalamous forms. Many of these, particularly the saccamminids, were tiny, <120 µm in maximum dimension. Based on our analysis of this sample, and previous results in the North Atlantic and NW Indian Oceans, we suggest that these poorly known taxa are a consistently important component of the abyssal meiofauna in well-oxygenated areas.     

Surficial Hydrocarbon Seep Infauna from the Blake Ridge (Atlantic Ocean, 2150 m) and the Gulf of Mexico (690–2240 m)

Abstract.  Infauna, including foraminifera and metazoans, were enumerated and identified from five types of seep habitats and two adjacent non-seep habitats. Collections were made with the deep submergence research vessel 'Alvin' from three areas of active seepage in the Gulf of Mexico (Alaminos Canyon [2220 m], Atwater Canyon [1930 m], and Green Canyon lease block 272 [700 m]) and on the Blake Ridge Diapir [2250 m], which is located off the southeastern coast of the United States. The seep habitats sampled included four types of microbial mats ( Beggiatoa , Thioploca , thin and thick Arcobacter ) and the periphery of a large mussel bed. Sediments under large rhizopod protists, xenophyophores, were sampled adjacent to the mussel bed periphery. A non-seep site, which was >1 km away from active seeps, was also sampled for comparison. Densities of most taxa were higher in the Gulf of Mexico seeps than in Blake Ridge samples, largely because densities in the thick microbial mats of Blake Ridge were significantly lower. Diversity was higher in the Thioploca mats compared to other microbial-mat types. Within an ocean basin ( i.e. , Atlantic, Gulf of Mexico) we did not observe significant differences in meiofaunal or macrofaunal composition in Beggiatoa versus Thioploca mats or thin versus thick Arcobacter mats. Foraminifera represented up to 16% of the seep community, a proportion that is comparable to their contribution at adjacent non-seep communities. In general, the observed densities and taxonomic composition of seep sites at the genus level was consistent with previous observations from seeps ( e.g. , the foraminifers Bolivina and Fursenkoina , the dorvilleid polychaete Ophryotrocha ).     

Abundance and biomass of meiobenthos in the spawning ground of anchovy (Engraulis japanicus) in the southern Huanghai Sea

1 Introduction Meiofauna is an important group in benthic small food web energetically due to their small size, high abundance and fast turnover rates. The production of meiofauna is equal to or higher than that of macrofau- na in estuaries, shallow waters and deep sea (Gerlach, 1971; Platt and Warwick, 1980; Heip et al., 1985; Zhang et al., 2004). A role of meiofauna may be the recycling of nutrients. Marine nematodes may keep the bacterial colonies on sand grains in active phase of growth …     

The effects of brine disposal on a subtidal meiofauna community

Desalination plants generate notable (>1,000 s m³) quantities of hypersaline brine which potentially affect the biological communities in the receiving area. We assessed whether proximity to a brine discharge point located off Gran Canaria (Canary Islands, eastern Atlantic) altered patterns in the abundance and assemblage structure of subtidal, soft-bottom, meiofauna. Samples were collected twice (May 2008 and January 2009) at 0, 15 and 30 m away from the brine discharge point, corresponding to a change in salinity from 45 to 36. Proximity to the brine discharge point affected overall meiofaunal abundances: lowest abundances were observed at 0 m (64.55 ± 39.86 ind 10 cm⁻², mean ± SD) than at 15 (210.49 ± 121.01 ind 10 cm⁻²) and 30 m (361.88 ± 102.64 ind 10 cm⁻²) away from the brine discharge point. This pattern was particularly notable for the most conspicuous meiofaunal groups: nematodes and copepods, and meiofaunal assemblage structure also differed with varying proximity to the brine discharge point. Although multivariate techniques identified changes in salinity as a relevant driver of patterns in meiofaunal assemblage structure with varying proximity to the brine outfall, a shift in particle size composition between May 2008 and January 2009 also contributed to explain differences in meiofaunal abundances and assemblage structure with varying proximity to the brine discharge point. Hence, meiofauna can be considered a suitable tool to monitor environmental impacts derived from the discharge of hypersaline effluents on subtidal, soft-bottom, assemblages if potential confounding drivers, i.e. here temporal changes in particle size composition, are accounted for to avoid possible confusing interpretations.     

南海北部深海小型底栖动物丰度和生物量

2010年9月在南海北部5个深海站位和1个浅海站位进行了小型底栖动物和环境因子采样,对小型底栖动物的丰度和生物量进行了定量研究。本次调查中,共鉴定出10个小型底栖动物类群,分别是线虫、桡足类、多毛类、介形类、甲壳类幼体、异足类、寡毛类、涡虫、无板类和等足类。从丰度来看,线虫是绝对的优势类群,占总丰度百分比为94.72%;桡足类次之,占2.70%;多毛类再次,占1.62%;其他类群之和仅占0.96%。从生物量来看,线虫的生物量最大,占总生物量的53.83%;其次是多毛类,占32.17%;居生物量第三位的是桡足类,占7.14%;其他类群之和占6.85%。小型底栖动物的丰度和干重生物量分别为566.12±635.61个·(10cm2)-1和398.43±431.98μg·(10cm 2)-1,线虫的丰度和干重生物量分别为536.21±593.48个·(10cm 2)-1和214.48±237.39μg·(10cm 2)-1。研究站位线虫、桡足类、多毛类和小型底栖动物丰度,小型底栖动物生物量与环境因子的相关分析表明,影响线虫丰度、小型底栖动物丰度、小型底栖生物生物量的主要环境因子包括底层水pH值、沉积物粉砂黏土含量和有机质含量。单因素方差分析(One-way ANVOA)结果表明,线虫丰度、桡足类丰度、小型底栖动物丰度和生物量在不同站位均有显著差异。与渤海、北黄海、南黄海、长江口、芽庄湾(越南)、大亚湾、北部湾、南海近海等海域相比,本研究海域的小型底栖动物丰度和生物量偏低。     

Distribution of meiofaunal abundance in relation to environmental factors in Beibu Gulf, South China Sea

This study aims to explore the distribution of meiofaunal abundance in relation to environmental factors in the Beibu Gulf,a natural semi-enclosed part of the South China Sea,surrounded by China and Vietnam.Meiofauna and ten benthic environmental factors were determined at 27 sampling stations in the Beibu Gulf in four surveys during 2006-2007.The results show a clear geographical trend in meiofaunal abundance,water depth,salinity and clay content.The meiofaunal abundance and the clay content decreased,whereas the water depth and the salinity increased from the north to the south of the Gulf.The percentage of meiofaunal abundance in the 0-2 cm layer increased,whereas in the 2-5 cm and 5-10 cm layers it decreased from the north to the south of the Gulf.Correlation analysis show significant negative correlations between meiofaunal abundance and water depth,benthic temperature,salinity and pH,but significant positive correlations between meiofaunal abundance and dissolved oxygen,chlorophyll a and clay content.     

东寨港红树林小型底栖动物的密度和生物量研究

2012年2月对海南省东寨港红树林滩涂沉积物小型底栖动物进行研究,结果表明,红树林中有六大类小型底栖动物,包括自由生活线虫、桡足类、涡虫、多毛类、寡毛类、海螨.在种类组成上,自由生活线虫为优势类群,在4个采样站位中,分别占小型底栖动物总数量的95.30％,97.02％,96.45％,90.53％.东寨港红树林小型底栖动物的总栖息密度为(1 082.23±563.76)个/(10 cm2),总生物量为(764.06±511.63)μg/(10 cm2).4个采样站位平均多样性指数H'分别为0.26、0.17、0.20、0.45,平均均匀度指数 J 分别为0.13、0.09、0.10、0.23.最小显著极差法(LSR)进行多重比较分析表明,4个采样点小型底栖动物差异明显.海洋线虫与桡足类的数量之比(N/C)显示东寨港红树林受到了有机质污染.