Diversity and abundance of molluscs in Thalassia testudinum prairie of the Bay of Mochinma, Mochima National Park, Venezuela

The diversity and abundance of benthic malacological communities associated to Thalassia testudinum beds was studied at four localities of Mochima Bay, Sucre state, Venezuela. At each locality, samples were taken monthly on perpendicular transect at different depths (0-4 m), from January 1991 to December 1991, using a quadrate (0.25 m2) for collecting mollusks and sediments. A total of 2,988 organisms of infauna and epifauna belonging to 81 species of the classes Gastropoda (41) and Bivalvia (40) were collected. More abundant species were Anadara notabilis, Codakia orbicularis, Cerithium litteratum, Cerithium eburneum, Batillaria minima, Modiolus squamosus, Modulus modulus, Chione cancellata, Turritella variegata, Arca zebra, y Laevicardium laevigatum. There were significant differences in number of organisms between depth and month at La Gabarra which presented the highest value of total (4.51 bits/ind) and monthly diversity (2.71-3.90 bits/ind). Biomass and abundance were low in the Mochima Bay while Varadero station presented the highest value. The bivalve A. notabilis and gastropod M. modulus were species common to the four stations.     

Benthic macrofauna associated to Thalassia testudinum in Bahía de Mochima, Sucre, Venezuela

Diversity and abundance of benthic macrofauna associated to Thalassia testudinum were studied at Ensenada de Reyes, Mochima Bay, in the northeastern coast of Venezuela. Samples were taken monthly in six stations, three at 1 m in depth and three at 6 m, between December 1992 and February 1994, using a quadrat of 0.25 m2 for collecting plants and sediment; each sample was washed with seawater through a 1 mm sieve. The specimens were fixed in 6% formaldehyde. A total of 1722 organisms (6 888 ind x m2) and 127 species of macroinvertebrates were collected. Mollusks dominated with 53 species, followed by polychaetes (40), crustaceans (18) and echinoderms (8). Remaining groups were represented by 1-2 species. The highest abundance was in October (214 specimens), and the lowest in December 1993 (79 specimens). Specific richness was between 47 species in October and 18 in May 1993. Mean species diversity was 2.79-1.36 bits/ind. There were differences (ANOVA p<0.01) in number of specimens at the two depths but not throughout the 15 month study period (p>0.05). There were more specimens and species at the lowest depth and in stations with higher Thalassia testudinum biomass.     

浙江水源地河流浮游动物多样性与环境因子的通径分析

为探明水源地河流浮游动物多样性及与水环境因子的关系, 利用浮游动物多样性参数监测水质, 2010-2014年间, 我们于每年的冬季(1月)、春季(4月)、夏季(7月)和秋季(10月), 对浙江2个水源地河流采样站(H1站和H2站)展开浮游动物种类组成、丰度和多样性指数的季节性调查, 同时测定水环境因子。结果表明, H1站和H2站浮游动物平均丰度分别为1,387.4 ind./L和873.0 ind./L, 小型浮游动物(轮虫 + 桡足类无节幼体)丰度分别占92.8% (H1站)和91.5% (H2站)。两采样站轮虫、枝角类和桡足类的优势种均为针簇多肢轮虫(Polyarthra trigla)、短尾秀体溞(Diaphanosoma brachyurum)和温剑水蚤(Thermocyclops sp.)。多元逐步回归与通径分析结果表明: 冬季氮磷比是轮虫类Shannon-Wiener多样性指数(H′)波动的限制因子, 主要通过总磷含量对轮虫类H′指数产生较大的间接正向作用; 春季氮磷比是轮虫类H′指数发展的决策因子; 秋季氮磷比可通过总氮含量对轮虫类H′指数产生较大的间接正向作用。冬季氨氮、总氮含量分别是甲壳动物体积多样性指数(Hs)的决策因子和限制因子。夏季溶解氧含量是总浮游动物物种丰富度(d)波动的限制因子, 主要通过pH值对d指数产生较大的间接正向作用, 作用机制表现为轮虫类H′指数随着夏季溶解氧含量的升高呈极显著上升(P < 0.01), 而甲壳动物Hs指数则显著下降(P < 0.05)。水源地河流环境因子与浮游动物多样性之间的相互关系为浙江水源地生态学监测提供了可能性。     

The benthic fauna of Sabancuy Estuary, Campeche, Mexico]

The fish and invertebrates community structure in the Sabancuy estuary was analyzed in two seasons and 14 sampling stations (13 along the estuary and one in the marine adjacent coast). No significant differences were found between seasons. The environmental frame defines two zones within the estuary, the first extends from the access highway to Sabancuy town until the Pujo mouth in the west; the second from the bridge to the estuary head in the east. The most abundant invertebrates were mollusks (51.8% of the total), in biomass the crustaceans dominated. The fish included 21 families and 33 species; the most abundant were Gerridae, Scianidae, Sparidae, Lutjanidae and Ciprinodontidae. The highest diversities of both communities correspond to the central part of the estuary. These communities include three sections with notable differences in faunal distribution: one is influenced by the exit to Terminos lagoon, the secondary in the estuary head and a third is in a transition zone defined by the proximity of the town access bridge. The ecological organization suggests a strong division caused by the bridge, both sides are scarce in habitats and nutrient resources and this is reflected in the low species counts.     

福建省主要海湾潮下带大型底栖无脊椎动物组成与分布特征

根据2010年8月对福建省12个主要海湾潮下带大型底栖无脊椎动物的调查资料,分析了大型底栖无脊椎动物的种类组成、生物多样性和群落结构分布特征及其与环境因子的关系.结果表明: 12个海湾共采集到大型底栖动物382种,包括环节动物170种、甲壳动物75种、软体动物78种、棘皮动物19种,以及其他类群40种.物种数、丰度、生物量和生物多样性指数空间差异较大: 罗源湾物种数最高,为92种,旧镇湾最低,为25种,所有海湾平均(55±21)种;所有海湾在物种组成上均为多毛类占优势,其平均物种数百分比为(51.8±5.5)%;诏安湾平均丰度最高,为(1330±1094) ind·m^-2,其次为福清湾、厦门湾、湄洲湾,泉州湾最低;兴化湾平均生物量最高,为(821.2±2387.7) g·m^-2,其次为福清湾、厦门湾,深沪湾最低;丰富度指数和Shannon多样性指数在罗源湾、湄洲湾、深沪湾、厦门湾和东山湾呈现较高值,而在福清湾和旧镇湾呈现较低值,两者的全域均值分别为(0.80±0.09)和(2.73±0.64).以相似度20%为界,可将研究区域的大型底栖无脊椎动物划分为14个群组,其中罗源湾内各站位间群落相似度最高,湾内差异最小,其次为三沙湾、福清湾、深沪湾和诏安湾,而其他海湾不同站位的群落组成差异较大.物种数、多样性指数和环境因子间的相关性分析和主成分分析显示,造成研究区大型底栖动物群落结构组成和分布差异的主要环境因子依次为沉积物铜、水深和底层水体活性磷酸盐.     

Mollusks associated to the submerged roots of the red mangrove,Rhizophora mangle (L.), in the Gulf of Santa Fe,Sucre State,Venezuela

A qualitative and quantitative monthly study of the mollusks community associated to the submerged roots of the red mangrove, Rhizophora mangle (L.), between October of 1998 and September of 1999, in six stations of the Gulf of Santa Fe, (Sucre State, Venezuela). Were collected 4,704 specimens, 45 species of mollusks were identified (22 gastropods, 15 bivalves and 8 chitons). The most abundant species were: Crassostrea rhizophorae, Isognomon bicolar, I. alatus and Brachidontes exustus. The highest values in diversity and evenness, and the smallest dominant values, were in the stations three and four, while the opposed happened in the stations one and two. The analysis of likeness showed that in the first five stations the space variations in the composition of the community are bigger than the temporary variations, while in the station six the temporary differences prevail. They were factors that could be important to determine the structure of the community, as vicinity to other ecosystems and/or specific biological aspects of the species like adaptations to fluctuating conditions, nutritious habits and migration in search of shady and protected atmospheres.     

Composition, structure and distribution of the ichthyoplankton in a Mediterranean coastal lagoon

The species composition and assemblage structure of the ichthyoplankton from the Mar Menor Lagoon in south‐east Spain are given. The fish larvae were sorted from zooplankton samples collected at 20 stations with a plankton net (50 cm mouth diameter and 500 μm mesh) during 36 surveys between February and December 1997. A total of 39 575 fish larvae representing 14 families, 22 genera and 36 species were identified. Gobiidae was the most dominant family (77·0%) followed by Blenniidae (19·4%) and Atherinidae (1·3%). The most abundant species were Gobius niger and Gobius paganellus , which accounted for 42·7 and 19·3% of the total respectively. These species were followed in order of relative abundance by Pomatoschistus marmoratus (13·9%), Parablennius pilicornis (9·4%), Lipophrys pavo (7·7%), Atherina boyeri (1·3%) and Parablennius tentacularis (1·3%). The high species diversity (2·0–2·8 bits individual⁻¹ for the annual diversity spectra at each sampling station) reflected a diverse assemblage of species. The main commercial species in the lagoon (Sparidae and Mugilidae) were poorly represented among the ichthyoplankton and they probably enter the lagoon on the bottom as recruits. Chlorophyll a concentration in the water column was the main factor explaining the seasonal variation in larval abundance. Spatial distribution of larvae was related to hydrographical circulation patterns in the lagoon and the movement of marine‐spawned larvae through the channels connecting the lagoon with the Mediterranean Sea.     

Oligochaetes in the southern basin of the Venetian Lagoon: community composition, species abundance and biomass

The oligochaete community of the Chioggia Lagoon (southern basin of the Venetian Lagoon) has been studied from May 1992 to May 1994, at ten fixed sampling stations, distributed across the lagoon. Numerous data regarding composition, abundance, biomass and the breeding periods of the species in the community have been obtained. Nine tubificid species, recently reported for the Mediterranean and Ponto-Caspian areas have been collected. Among them only three were abundant everywhere, except in the innermost part of the lagoon, and throughout the year: Tubificoides vestibulatus, T. swirencowi and Limnodriloides maslinicensis. Only one enchytraeid genus, Grania, has been found restricted to an area near the connection with the sea. The values for the Shannon Diversity Index for the community never exceeded 0.8 and were mainly between 0.4 and 0.7. The most interesting result was the decrease of abundance and biomass, proceeding from the sea mouth (about 6000 ind m^–2) towards the innermost part of the lagoon (less than 100 ind. m^–2). Correlations are suggested with the different grain size of the sediment.     

The vertical distribution and abundance of gastropods and bivalves from rocky beaches of Cuastecomate Bay, Jalisco, México

The vertical distribution and abundance of conspicuous gastropod and bivalve species were studied at five rocky beaches in Cuastecomate Bay, Jalisco. Sampling was done from September, 1993 through March, 1994 with 0.75 m2 quadrants placed along replicate transect lines (10 m long) in the supralittoral and mesolittoral (upper, middle and lower intertidal) zones. A total of 6,643 mollusks were collected. Gastropods dominated the samples (6,272 individuals, 44 species); the bivalves were less abundant and diverse (371 individuals, five species). Seventeen species comprised 89.8% of all individuals collected. The gastropods Nodilittorina aspera and Nerita scabricosta were the most abundant with 637.8 and 71.43 individuals/m2, respectively. The most abundant bivalves were Brachidontes adamsianus and Chloromytilus palliopunctatus with 60.7 and 61.3 individuals/m2 respectively. The abundance of gastropods decreased from the supralittoral to the lower tidal zones while the number of species increased in the same direction. The number of species of bivalves also increased from the supralittoral to the lower intertidal zone; the abundance of individuals was higher at the middle intertidal zone. Affinities between groups of species among sampling stations were identified by computing Pearson's correlation coefficient using abundance values (ind./m2) and Jaccard's dissimilarity index using species presence or absence in the lower intertidal zone. Affinity among stations was not dependent upon their vicinity but on the high dominance of few species, the occurrence of many secondary species and beach characteristics.     

Benthic fauna associated to a Thalassia testudinum (Hydrocharitaceae) bed in Parque Nacional Morrocoy, Venezuela

The benthic fauna and diel variation in a shallow seagrass bed (Thalassia testudinum) were studied in Playa Mero, Venezuela. Samples of organisms and sediments were taken using PVC cylinders, 5cm in diameter, along a transect perpendicular to the coast. Seagrass cover, shoot density and biomass were estimated. The seagrass cover was homogeneous along the transect. The intermediate zone had the highest number of shoots and of above-ground and rhizome biomass. Composition and abundance of benthic organisms were related with seagrass and sediment characteristics. Sediment organic matter content and organism abundance were highest near the shore Molluscs, polychaetes, oligochaetes and nematodes were the most abundant groups. Species richness was higher in daytime (40 versus 28 at night). Gastropods were the most abundant organisms both at day and night while polychaetes and crustaceans increased during the day, and holoturids were more numerous at night.     

Peracarid crustacean assemblages of the Kolbeinsey Ridge,north of Iceland

On the Kolbeinsey Ridge, north of Iceland, 92 species of peracarid crustaceans were sampled using the epibenthic sledge. For an analysis of the multispecies distribution pattern across the ridge, a total of 46 species have been considered, which occurred at least at two stations and with at least 5% relative abundance at any one station. The analysis revealed four assemblages: a deep species assemblage, an eastern slope assemblage, an ubiquitous species assemblage and a western slope assemblage. The western slope assemblage consists mainly of Amphipoda, which were most abundant and diverse on the western slope. The ubiquitous and eastern slope assemblages, however, are dominated by Isopoda, which also comprised most species and individuals on the eastern slope. Cumaceans were the most representative species of the deep species assemblage. These differences in species composition and abundance can probably be attributed to food supply and sediment composition, rather than to salinity or bottom water temperature.     

Peracarid composition,diversity and species richness in the area of the Northeast Water polynya,East Greenland (Crustacea,Malacostraca)

During the ARK XI-2 expedition with RV Polarstern in September/October 1995, a transect of epibenthic sledge (EBS) samples was taken in the area of the Northeast Water Polynya off the Greenland coast, from the shelf down into the deep sea. A total of 85,304 specimens of Peracarida were collected at seven stations. These individuals comprised 45 families, 103 genera and 180 species. With regard to abundance, Cumacea occurred with highest numbers, 31,269, followed by Isopoda, Amphipoda, Mysidacea and Tanaidacea. Species richness was highest in Amphipoda with 94 species, followed by Isopoda with 43 species, Cumacea with 20 species, Tanaidacea with 15 and Mysidacea with 8 species. Species richness was highest at the shallowest station 37-016 and lowest at the deepest station 37-021, whereas the opposite pattern was found for abundance. Diversity and eveness were highest at the southernmost station and lowest at the deepest station. Amphipoda occurred more frequently at the shallower stations, while Cumacea were very frequent at the deepest station. Numbers of species were lowest for Cumacea at the deepest station, while Amphipoda and Isopoda generally occurred with high species richness at all stations. On the basis of the species composition stations were compared.     

Diversity and abundance of mollusks in the sublittoral epifaunal community of Punta Patilla, Venezuela

The diversity of a sublittoral epifaunal mollusk community of Punta Patilla, Sucre State, Venezuela, was studied from September 1990 to September 1991. We identified 25 species (14 bivalves and 11 gastropods) of mollusks that inhabit gravel, soft sand and bottoms covered by Thalassia testudinum. Total diversity indices were H' = 3.42. J' = 0.74 and 1-D = 0.85. Monthly diversity reached its maximum in March 1991 (3.12 bits/ ind.), June 1991 (2.88 bits/ind.) and September 1991 (2.95 bits/ind.); minimum diversity was recorded in August 1991 (1.20 bits/ind.). A log series model showed a diversity index alpha = 4.56 for species abundance data and alpha = 3.11 for biomass data. The more abundant species were Chione cancellata, Anigona listeri, Chione granulata and Area zebra among the bivalves, and Chicoreus brevifrons, Turritella variegata and Phllonotus pomum among the gastropods (which present maximum biomass). The average total biomass (56.80 g/m2) is low when compared to reports from other tropical zones.     

2013年夏威夷东南部海区表层砂壳纤毛虫的群落结构和分布特征

鉴于东太平洋热带海区表层砂壳纤毛虫和其他微型浮游动物的群落结构资料几乎空白, 我们于2013年8月14日至9月18日在夏威夷东南部海区的23个站位采样调查了表层砂壳纤毛虫群落。23个站位共采集到砂壳纤毛虫22属36种, 均为透明壳种类。各站砂壳纤毛虫种丰富度范围为15-21种, 总丰度范围为4,730-23,693个/m³, 生物量范围为9.60-88.61 μg C/m³。本海区主要优势种为镯形囊坎虫(Ascampbelliella armilla)、斯廷细瓮虫(Steenstrupiella steenstrupii)、薄壳真铃虫(Eutintinnus tenuis)和纤弱细瓮虫(Steenstrupiella gracilis), 这4种主要优势种的口径范围不同。     

莱州湾大型砂壳纤毛虫群落季节变化

为揭示莱州湾砂壳纤毛虫群落季节变化规律, 在莱州湾设置8个站位, 于2011年5-11月及2012年3-4月进行了9个航次的调查, 用浅海III型浮游生物网由底至表垂直拖网采集砂壳纤毛虫。结果表明, 莱州湾3-11月砂壳纤毛虫物种丰富度的变化范围为5-19, 周年变化呈现一峰两谷的趋势。丰度的范围为0-318 ind./L, 丰度较大(> 50 ind./L)的种类有运动类铃虫(Codonellopsis mobilis)和清兰拟铃虫(Tintinnopsis chinglanensis)。各月平均丰度随时间的变化趋势为双峰型, 最大值出现在7月(63 ind./L), 次峰值出现在5月(48 ind./L), 最小值出现在3月(2 ind./L)。黏着壳种类在3-11月均有出现, 透明壳种类仅在温度较高(> 15°C)的6-9月出现。各月的优势种数目为1种(5月)到8种(8月), 其中运动类铃虫在所有月中都是优势种, 对砂壳纤毛虫丰度周年的变化规律产生较大影响。使用各月所有种类的平均丰度对各月砂壳纤毛虫群落进行聚类分析, 得到两个群落(相似度30%): 群落I(7-9月)和群落II(3-6月、10-11月), 说明砂壳纤毛虫群落发生了明显的季节变化。砂壳纤毛虫的物种丰富度、丰度与环境因子(温度、盐度)均没有明显的相关性。     

Composition and distribution of benthic isopod (Crustacea,Malacostraca) families off the Victoria-Land Coast (Ross Sea,Antarctica)

The benthic fauna off the Victoria-Land-Coast, Ross Sea (Antarctica) was investigated during the 19th Italica expedition in February 2004. Samples were taken along a latitudinal transect from Cape Adare down to Terra Nova Bay at water depths ranging from 84 to 515 m. A Rauschert dredge was used at 18 stations to collect epi- and infaunal macrobenthos. 9,494 specimens of Isopoda were collected, representing 19 families. Desmosomatidae were the most abundant family (35,297 ind/1,000 m²), followed by Paramunnidae (23,973 ind/1,000 m²). Paramunnidae was the most frequent taxon and was collected at all stations, in contrast to the Desmosomatidae, which did not occur at any station off Cape Adare.     

Environmental Influence on Planktonic Cladocerans and Copepods in the Floodplain of the Upper River Paraná, Brazil

The abundance of microcrustacean species recorded in plankton samples from the littoral and pelagic zones of the Upper Paran River, State of Mato Grosso do Sul, Brazil, was evaluated in relation to abiotic and biotic environmental factors. The cladocerans Bosminopsis deitersi and Bosmina hagmann i were most abundant. The presence or absence of aquatic macrophytes also influenced abundance and species composition. The true zooplankton species were most abundant at the pelagic stations, while species of Chydoridae and Macrothricidae contributed markedly to microcrustacean abundance and species richness at littoral stations. Species abundance was also strongly affected by water level variation. Microcrustaceans, mainly bosminids, were most abundant during low water. During high water, bosminids decreased in abundance while most other species increased. The higher variation of the environmental factors during high water probably explains the shift in abundance patterns. Changes in water level increased mixing of littoral and pelagic microcrustaceans between sampling stations.     

Abundance and diversity of peracarid taxa (Crustacea, Malacostraca) along a transect through the Beagle Channel, Patagonia

During the joint Chilean-German-Italian Magellan “Victor Hensen” Campaign in November 1994, samples were taken on a cruise of the RV Victor Hensen in order to obtain faunistic information from the Beagle Channel. Peracarida are an important fraction of the macrobenthos and were sampled in high numbers. Using an epibenthic sledge, 104,618 individuals were collected in total, comprising 62,860 Amphipoda, 14,685 Cumacea, 17,992 Isopoda, 7,168 Mysidacea and 1,893 Tanaidacea. To allow comparisons between stations, these numbers were standardized to a 1,000 m trawling distance, yielding about 368,000 individuals from all stations. Peracarida were most abundant at station 1213, southeast of Isla Picton, in the oceanic area close to the eastern entrance of the Beagle Channel (166,361 ind./1,000 m). Generally, stations off the eastern entrance were characterized by a high number of Peracarida. In the Beagle Channel itself, however, the abundance decreased from east to west with a single peak in peracarid number in the channel east of Punta Yámana. Numbers were much lower at the western entrance (792 ind./1,000 m) and even fewer Peracarida were collected in the Magdalena Channel off Punta Sánchez. Lowest numbers were recorded close to the glacier Romanche and west of Isla Picton at two locations. The composition of peracarid crustaceans was analysed in relation to the background of hydrographical and sedimentological differences, nutrient availability, and knowledge of the other associated fauna in the Beagle Channel. The available data lead us to conclude that abundance and composition of peracarid taxa in and south of the Beagle Channel (off the eastern entrance) seem to be influenced mainly by sediment composition and hydrographical characteristics as indicated above. Received: 18 October 1996 / Accepted: 19 December 1996     

Bathymetric distribution and diversity of deep water polychaetous annelids in the Sigsbee Basin, northwestern Gulf of Mexico

The deep water polychaete fauna is analyzed in this study particularly regarding its composition and variations with depth in the Sigsbee Basin, northwestern region of the Gulf of Mexico. Samples were taken at 10 stations along a bathymetric gradient with depth ranges from 200 to 3760 m with a USNEL (0.25 m²) corer. A total of 287 individuals were identified, from 21 families and 65 species. The most important families, both in terms of abundance and species richness, were: Paraonidae (65.4 ind./0.25 m², 9 spp.), Cirratulidae (28.93 ind./0.25 m², 7 spp.) and Spionidae (18.07 ind./0.25 m², 7 spp.). In general, density tended to decrease with depth with minima at around 2000 m, although two abundance peaks were detected at 3700 and 3760 m, making the pattern seem an inverted parabolic curve. The Shannon-Wiener diversity values varied from 0.54–0.92 at around 2000 m to 3.39 at 3620 m and 3.34 at 3760 m. These results contrast with what is already reported from the North Atlantic and the Tropical Pacific deep benthic communities, where highest diversities are found at 2000 m. Faunal changes evaluated through Beta Diversity (0.08–0.1) and the low similarity found between the stations, emphasized the high variability in the composition of the fauna in the Sigsee Basin, meaning that the faunal composition is practically different at all the sampling stations. Ten species are newly recorded for the Mexican fauna.     

Polychaeta (Annelida) associated with Thalassia testudinum in the northeastern coastal waters of Venezuela

Seasonal variations of polychaetes in a Thalassia testudinum bed were studied from June 2000 to April 2001 in Chacopata, northeastern Venezuela. Eight replicate samples were taken monthly with a 15 cm diameter core and the sediment was passed through a 0.5 mm mesh sieve. A total of 1,013 specimens, belonging to 35 species, was collected. The monthly density ranged from 387 ind/m2 (September) to 1,735 ind/m2 in May (x = 989+/-449 ind/m2). Species richness was lowest in August and September (8) and highest (25) in April (x = 18.00+/-5.29). The shoot density of Thalassia showed an average of 284+/-77.60 shoots/m2, with extreme values in February (164) and May (422). Species diversity ranged from 1.25 in August and 3.33 bits/ind in December (x = 2.47+/-0.64). Significant positive correlations were detected among the number of Thalassia shoots, polychaete abundance and species richness, as well as among species richness, polychaete abundance and species diversity. Species number and average density were found within the intervals of mean values reported in similar studies. The higher number of species and organisms obtained in March-April and June-July can be attributed to the recruitment correlated with the regional up-welling.