Characteristics of macrofauna and their response to aquiculture in Yueqing Bay, China

Four seasons of investigations on macrofauna in Yueqing Bay, China were carried out from August 2002 to May 2003. One hundred and twenty four species of macrofauna were identified, including 41 species of polychaeta, 37 species of mollusc, 22 species of crustacea, 10 species of echinoderm and 14 others. The average biomass was 41.95 g·m⁻² and the average density was 85 ind·m⁻². The echinoderm contributed the highest proportion (about 60%) to the total biomass, and the mollusc contributed the maximum proportion (about 35%) to the total density. Biomass and density in spring were higher than those in other seasons. This article analyzes the macrofauna distribution, compares the study results with the history data of Yueqing Bay and adjacent bays, and discusses the response of macrofauna community to the aquiculture in Yueqing Bay.     

乐清湾大型底栖生物群落特征及其对水产养殖的响应

乐清湾大型底栖生物的四季采样研究。发现124种大型底栖生物,其中多毛类41种、软体动物37种、甲壳类22种、棘皮动物10种和其他类14种。乐清湾大型底栖生物年均生物量41．95g·m^-2年均密度85个·m^-2,生物量棘皮动物居首（约占60％）;密度软体动物最大（约占35％）。生物量和密度分布春季为最高。对乐清湾大型底栖生物分布现状与以往资料及邻近海湾进行了比较,并将大型底栖生物群落对乐清湾牡蛎养殖和网箱养殖的响应做了分析探讨。     

乐清湾潮间带大型底栖动物群落分布格局及其对人类活动的响应

于2006年9月和2007年5月对乐清湾5条潮间带断面进行了大型底栖动物调查。 共鉴定出大型底栖动物113种, 其中软体动物40种, 多毛类25种, 甲壳动物24种, 棘皮动物9种, 其它动物15种。从季节来看, 物种数秋季(81种)高于春季(68种),但平均生物量和平均栖息密度春季(分别为(91.90±59.14) g/m²和(1541±1261.41)个/m²)明显高于秋季(29.20±22.20)g/m²和(201±52.97)个/m²);春季以焦河蓝蛤 幼体、彩虹明樱蛤 、婆罗囊螺 、绯拟沼螺 为主要优势种,而秋季以短拟沼螺 、彩虹明樱蛤、淡水泥蟹 、巢沙蚕 为主要优势种,说明乐清湾大型底栖动物群落特征随着季节有着较大的变化。各断面的Shannon-Winner指数(H')为2.34-3.31,平均为2.85±0.35;Margalef's species richness 指数(d)为3.02-6.42,平均为4.29±1.10;Pielou's evenness 指数(J')为0.46-0.73,平均为0.62±0.09。运用ABC曲线、等级聚类和MDS对大型底栖动物群落结构分析发现,群落结构已受到中度干扰,稳定性差。与以往历史资料相比,乐清湾大型底栖动物向次生型群落转化,原因可能与过度采捕、生境恶化、海岸工程以及围塘养殖等人类活动的影响有关。     

Movement patterns of catfishes (Ariidae) in a tropical semi‐arid estuary

From December 2005 to November 2006, 216 samples were taken from the main channel of the Goiana Estuary, representing a total sampled area of 23 ha. Ariidae species were the most abundant in density (1600 individuals ha^?1, 53%) and biomass (18 813 g ha^?1, 63%). Cathorops spixii was the most abundant in density (1340 individuals ha^?1) and biomass (14 203 g ha^?1). The variables: number of species, total density and biomass, showed significant interactions between the factors of areas and seasons (P < 0·01). The highest total density (7394 individuals ha^?1) and biomass (70 292 g ha^?1) occurred in the middle and upper estuaries, respectively, during the early‐rainy season. The density of C. spixii differed significantly between areas and seasons (P < 0·01), while Cathorops agassizii differed significantly only between seasons (P < 0·01). The biomass differed significantly for the species C. spixii, C. agassizii and Sciades herzbergii between seasons, and C. spixii and C. agassizii between areas. Also, the density and biomass of C. spixii and C. agassizii showed interaction between areas and seasons. Only the biomass of S. herzbergii showed interaction between areas and seasons (P < 0·01). This indicates that seasonal variations influenced the distribution of Ariidae species in the different areas of the Goiana Estuary. Moreover, canonical correspondence analysis highlighted a strongly significant correlation (P < 0·01) between the seasonal variations of the environmental gradients (salinity and water temperature) and distribution of catfishes. The management and conservation of estuaries should take into account the life cycle of these species in different estuarine areas and hydrological seasons.     

Biomass and abundance of macrofauna in intertidal sediments of Königshafen in the northern Wadden Sea

Intertidal sediments of Königshafen (Island of Sylt, North Sea) were sieved for mesofauna (>0.25 mm) and macrofauna (>1 mm) in spring and autumn 1990. Although sediments are coarser than in other parts of the Wadden Sea, the macrobenthic fauna was very similar but with a tendency towards higher species density, abundance and biomass. Taking into account the areal size of sandy flats, seagrass beds, mud flats and mussel beds, the average biomass is calculated to be 65 g ash-free dry weight m^?2 The lugwormArenicola marina dominates the biomass (28%), followed by the bivalvesMytilus edulis (21%),Mya areanaria (16%),Cerastoderma edule (10%) and the mudsnailHydrobia ulvae (9%). While spring and autumn biomass are almost alike, abundance is highly variable and entirely dominated byH. ulvae. Mesofauna is mainly composed of oligochaetes, small and juvenile polychaetes. Abundance is similar to that of macrofauna, while biomass is only about 1 g m^?2. Macrophyte biomass amounted to 9% of that macrofauna. In the course of the centurym mussel beds expanded while muddy areas declined. The concomitant effects on biomass presumably compensated each other.     

Community characteristics and of zooplankton in Qinzhou Bay

Qinzhou Bay, the biggest bay in Guangxi Province, is very species-rich and is developing a robust marine economy. In recent years, as human impact has increased, problems associated with the environment have become more complicated. Measuring zooplankton diversity and abundance is a way to monitor environmental conditions. According to the data from four ecological surveys of the zooplankton in Qinzhou Bay during 2008 and 2009, a total of 134 species of zooplankton were identified, including 52 Copepoda species, 27 Medusa species, 14 Planktonic larvae, 9 Chaetognatha species, 8 Pteropoda species, 5 Amphipoda species, 4 Cladocera species, 4 Ostracoda species, 3 Thaliacea species, 2 Appendiculata species, 2 Sergestdae species, 2 Protlsta species, 1 Rotiera species and 1 Cumacea species. The fauna was clearly characterized as tropical population. The total species number was highest in autumn, followed by spring, winter and summer. Zooplankton species diversity in Qinzhou Bay has increased compared with the results obtained in 1983–1985 (83 species). However, compared with other bays, the number of zooplankton species in Qinzhou Bay is close to Daya Bay (128), higher than in Zhilin Bay (60), Jiaozhou Bay (81) and Luoyuan Bay (70), and far lower than in the north South Sea (709). We adopted the dominant index Y > 0.02 as the distinguishing standard of dominant species. The number of dominant species in spring, summer, autumn and winter were six, nine, eight and five. There was only one common dominant species (Penilia avirostris) appeared in different seasons, For summer and autumn, the shared dominant species numbered about four. Between other seasons, the shared dominant species varied between two and three. The number of uniquely dominant species was four in summer, three in autumn and one in both spring and winter. The dominant species in different seasons have some overlaps and some differences. The average biomass of zooplankton was 378 mg/m³ at all times of year. The average biomass was largest in autumn, followed by winter, and was the least in spring and summer. The average density of zooplankton for the entire year was 805.11 ind/m³. The average density was largest in summer, followed by winter, and was least in autumn and spring. Copepoda and Planktonic larvae were the major components of zooplankton in spring and summer at Qinzhou Bay, with the other species’ densities under 10%. In autumn, Copepoda, Planktonic larvae and Chaetognatha were the major components of the biomass, and in winter, the major species were Copepoda and Cladocera, with the others species’ density under 10%. The average value of the Shannon–Wiener diversity index (H′) was 3.84 and the evenness index (J′) was 0.77. The zooplankton diversity index and community evenness overall were good and the community organization had a complete and stable state, but the status of the community was relatively weak. The relationship between biomass/density of zooplankton and environmental factors is remarkable. Biomass and density are positively correlated with temperature and nutrient concentration, and are negatively correlated with salinity.     

Foraging conditions of planktotrophic larvae of echinoderms in the southwestern part of Peter the Great Bay of the Sea of Japan

Foraging of planktotrophic larvae of echinoderm common species in the Peter the Great Bay (Sea of Japan) was estimated on the basis of distribution of phyto- and meroplankton. The diversity and abundance of phytoplankton in the studied area in summer months were shown (141 algae species; abundance—up to 743000 cells/m³; biomass—more than 2.7 g/m³ of fresh weight). It was found that in Peter the Great Bay the diet of echinoderm larvae depended on their feeding behavior, duration of their pelagic stage, and abundance and size composition of phytoplankton, included up to several micrograms of fresh algae per larva.     

Seasonal dynamics and grazing rate of zooplankton in Yueqing Bay,China

The species composition,biomass,abundance,and species diversity of zooplankton were determined for samples collected from August 2002 to May 2003 from 14 stations in Yueqing Bay,China.Phytoplankton growth rate and microzooplankton grazing rate were obtained by using the dilution method developed by Landry and Hassett.The spatial and temporal variations of zooplankton and its relationship with environmental factors were also analyzed.The results showed that the zooplankton in the Yueqing Bay could be divided into four ecotypes,namely coastal low saline species,estuary brackish water species,offshore warm water species,and eurytopic species.A total of 75 species of zooplankton belonging to 56 genera and 17 groups of pelagic larva were identified in the Yueqing Bay.The coastal low saline species was the dominant ecotype in the study area,and the dominant species were Labidocera euchaeta,Acartia pacifica,Acrocalanus gibber,Pseudeuphausia sinica,and Sagitta bedoti among others.There was considerable seasonal variation in zooplankton biomass and abundance in the surveyed areas.The peak biomass appeared in August,descending in November and in May,and the lowest biomass appeared in February.Similarly,the highest abundance of zooplankton was observed in August,with the abundance descending in the following months:May,November,and February.There were similar horizontal distribution patterns for the biomass and the abundance of zooplankton.They both increased from the upper to the lower bay in February and May,but decreased from the upper to the lower bay in August.Biomass and abundance were evenly distributed in the Yueqing Bay in November.Moreover,there was marked seasonal variation in the species diversity of zooplankton,which conformed to the abundance of zooplankton.Results of the dilution experiments indicated that there was grazing pressure of microzooplankton on phytoplankton in the Yueqing Bay throughout the year though the rate of microzooplankton grazing on phytoplankton varied seasonally.Phytoplanktons were growing at 0.26-2.07/d and grazed by microzooplankton at a rate of 0.15--0.48/d in different seasons.     

Structure of littoral zoocenoses in the macroalgae zones of the Neva River Estuary

The biodiversity and spatial distribution of macrofauna biomass are studied for 12 sites of stonesand littoral in the Neva Estuary in 2002–2005. The highest biodiversity has been observed for chironomids and oligochaetes in the Neva Bay (36% and 24% of total species number) and in the eastern Gulf of Finland (33% and 23%). Amphipods (≤89%), molluscs (≤61%), and chironomids (≤37%) dominate by biomass. The biomass spatial distribution vary dramatically from 9 to 37 g m⁻² in the freshwater Neva Bay and from 1 to 68 g m⁻² for the other Neva Estuary areas. The bottom fauna biomass in the Neva Bay is significantly lower than in the 1980–1990’s and constitutes 20–50% of the biomass previously observed. We explain such a significant decrease by a reduction of the insects and aborigine crustaceans Gammarus lacustris Sars and Asellus aquaticus L. The invasive amphipod species Gmelinoides fasciatus (Stebbing) dominated by biomass for the study period (3.8–15.6 g m⁻², or >30% of total macrozoobenthos biomass).     

Seasonal dynamics and grazing rate of zooplankton in Yueqing Bay, China

The species composition, biomass, abundance, and species diversity of zooplankton were determined for samples collected from August 2002 to May 2003 from 14 stations in Yueqing Bay, China. Phytoplankton growth rate and microzooplankton grazing rate were obtained by using the dilution method developed by Landry and Hassett. The spatial and temporal variations of zooplankton and its relationship with environmental factors were also analyzed. The results showed that the zooplankton in the Yueqing Bay could be divided into four ecotypes, namely coastal low saline species, estuary brackish water species, offshore warm water species, and eurytopic species. A total of 75 species of zooplankton belonging to 56 genera and 17 groups of pelagic larva were identified in the Yueqing Bay. The coastal low saline species was the dominant ecotype in the study area, and the dominant species were Labidocera euchaeta, Acartia pacifica, Acrocalanus gibber, Pseudeuphausia sinica, and Sagitta bedoti among others. There was considerable seasonal variation in zooplankton biomass and abundance in the surveyed areas. The peak biomass appeared in August, descending in November and in May, and the lowest biomass appeared in February. Similarly, the highest abundance of zooplankton was observed in August, with the abundance descending in the following months: May, November, and February. There were similar horizontal distribution patterns for the biomass and the abundance of zooplankton. They both increased from the upper to the lower bay in February and May, but decreased from the upper to the lower bay in August. Biomass and abundance were evenly distributed in the Yueqing Bay in November. Moreover, there was marked seasonal variation in the species diversity of zooplankton, which conformed to the abundance of zooplankton. Results of the dilution experiments indicated that there was grazing pressure of microzooplankton on phytoplankton in the Yueqing Bay throughout the year though the rate of microzooplankton grazing on phytoplankton varied seasonally. Phytoplanktons were growing at 0.26–2.07/d and grazed by microzooplankton at a rate of 0.15–0.48/d in different seasons. __________ Translated from Acta Ecologica Sinica, 2005, 25(8): 1853–1862 [译自: 生态学报, 2005, 25(8): 1853–1862]     

EFFECTS OF ISLAND GROUPS,DEPTH, AND EXPOSURE TO OCEAN WAVES ON SUBTIDAL MACROALGAL ASSEMBLAGES IN THE RECHERCHE ARCHIPELAGO,WESTERN AUSTRALIA1

Temperate Australia has a speciose highly endemic algal flora. This study explored the influence of geographical isolation between islands, depth and exposure to ocean swells on the diversity of macroalgae in the Recherche Archipelago (Western Australia). Macroalgae were harvested (0.25‐m² quadrats) from sites at two exposures (sheltered and exposed to wave energy), three depths (<10, 10–20, and 21–28 m), and two island groups (three islands within Esperance Bay and three islands outside the bay). A total of 220 species were collected. Species richness and biomass were significantly different at the smallest spatial scale (0.25 m²), and density of overstory species decreased with depth. Results from analysis of similarity tests suggested that macroalgal assemblages differed with depth, exposure and to a lesser extent with island group. Assemblage differences were often associated with particular overstory or understory taxa and not the entire assemblage composition. Average species richness·0.25 m^?2 ranged from 13 to 29 species, typically with a few species contributing more than 50% of average biomass. Species richness was maintained by species turnover at the 0.25‐m² spatial scale. Our results suggest that richness in temperate Australia is maintained by turnover of broadly distributed species. More dominant species in assemblages were associated with differences in depth and exposure to ocean swells. Our findings support the hypothesis of a geographical transition of dominant species from kelp‐dominated in the west to a fucalean‐dominated assemblage in the Recherche Archipelago and east of the Great Australian Bight.     

Seasonal dynamics of zooplankton and grazing impact of microzooplankton on phytoplankton in Sanmen Bay, China

The species composition, biomass, abundance and species diversity of zooplankton were determined for samples collected from 12 stations in Sanmen Bay, China, in four cruises from August 2002 to May 2003. Growth of phytoplankton and grazing rates of microzooplankton were measured using the dilution technique. The spatial and temporal variation of zooplankton and its relationship with environmental factors were also analyzed. The results showed that a total of 89 species of zooplankton belonging to 67 genera and 16 groups of pelagic larvae were found in Sanmen Bay. The coastal low-saline species was the dominant ecotype in the study area, and the dominant species were Calanus sinicus, Labidocera euchaeta, Tortanus derjugini, Acartia pacifica, Pseudeuphausia sinica and Sagitta bedoti. Maximum biomass was recorded in August, followed by November and May, and the lowest biomass was recorded in February. Similarly, the highest abundance of zooplankton was observed in August, followed by May, November, and February. Grazing pressure of microzooplankton on phytoplankton in Sanmen Bay existed throughout the year, although the grazing rate of microzooplankton on phytoplankton varied with the season. Estimates for growth rate of phytoplankton ranged from 0.25 d^?1 to 0.89 d^?1, whereas grazing rate of microzooplankton ranged between 0.18 d^?1 and 0.68 d^?1 in different seasons. The growth rate of phytoplankton exceeded the grazing rate of microzooplankton in all the seasons. Grazing pressure of microzooplankton on phytoplankton ranged from 16.1% d^?1 to 49.1% d^?1, and the grazing pressure of microzooplankton on primary production of phytoplankton ranged from 58.3% d^?1 to 83.6% d^?1 in different seasons.     

Soil microarthropods and macrofauna in monsoon tropical forests of Cat Tien and Bi Dup-Nui Ba National Parks,southern Vietnam

The abundance, biomass, vertical distribution, and taxonomic composition of soil invertebrates (springtails, macrofauna, and termites) were studied in forest formations differing in edaphic and climatic conditions: lowland forests dominated by Lagerstroemia spp. or Dipterocarpus spp. in the Cat Tien National Park and in a mountain pine (Pinus kesiya) forest on the Da Lat Plateau, southern Vietnam. In the lowland forests, springtails had a relatively low density (10000–12000 ind./m²), but their diversity was high (41–43 species in each forest). The density of large soil invertebrates (without ants and termites) reached 500–700 ind./m² at a biomass of approximately 30 g/m² (with earthworms accounting for up to 230 ind./m² and 19–28 g/m²). Among termites, species of the genera Macrotermes and Odontotermes were dominant. Their total biomass in some areas exceeded 15–20 g/m². In the mountain pine forest, the total biomass of soil macrofauna was approximately 11 g/m², the abundance and diversity of springtails were low (7500 ind./m², 28 species), and wood-destroying species of the genera Schedorhinotermes sp. and Coptotermes sp. dominated among termites.     

钦州湾大型底栖动物生态学研究

通过2008年~2009年在钦州湾及附近海域进行的4个航次的大型底栖动物调查,共获大型底栖动物8门62科94种,软体类最多,其次为多毛类,种类季节变化较大。以优势度指数Y>0.02为判别标准,调查区春季优势种为方格皱纹蛤（Periglypta lacerata (Hanley)）、刺足掘沙蟹（Scalopidia spinosipes Stimpsom）和独齿围沙蚕（Perinereis cultrifera Grube）,夏季优势种为方格皱纹蛤、刺足掘沙蟹和持真节虫,秋季优势种为曲波皱纹蛤和网纹藤壶,冬季优势种为肋鲳螺和方格皱纹蛤。春、夏季优势种变化不大,秋、冬季优势种变化较大,除方格皱纹蛤外均为季节特有种。海区底栖生物平均总密度和平均总生物量分别为439ind./m2和115.14g/m2。与20世纪80年代钦州湾茅尾海调查结果相比,平均栖息密度有所升高,但是平均生物量却有较大程度的降低。底栖动物群落的丰富度指数（D）、Shannon-Wiener多样性指数（H′）和均匀度指数（J′）平均值分别为4.01、1.80和0.73,水平不高。用SPSS软件将各站大型底栖动物的平均密度、平均生物量、多样性指数等生态特征值与水深等理化因子进行了Pearson相关分析,结果表明春季各特征指数与环境因子相关性不显著;夏季丰度、多样性指数和均匀度指数均与水深呈显著负相关,种类数、丰富度和多样性指数与沉积物pH呈显著负相关;秋季密度与硫化物呈显著正相关;冬季生物量与硫化物和有机质均呈显著正相关。     

UPTAKE AND RELEASE OF NITROGEN BY THE MACROALGAE GRACILARIA VERMICULOPHYLLA (RHODOPHYTA)1

Macroalgae, often the dominant primary producers in shallow estuaries, can be important regulators of nitrogen (N) cycling. Like phytoplankton, actively growing macroalgae release N to the water column; yet little is known about the quantity or nature of this release. Using ¹⁵N labeling in laboratory and field experiments, we estimated the quantity of N released relative to assimilation and gross uptake by Gracilaria vermiculophylla (Ohmi) Papenfuss (Rhodophyta, Gracilariales), a non‐native macroalgae. Field experiments were carried out in Hog Island Bay, a shallow back‐barrier lagoon on the Virginia coast where G. vermiculophylla makes up 85%–90% of the biomass. There was good agreement between laboratory and field measurements of N uptake and release. Daily N assimilation in field experiments (32.3±7.2 μ mol N·g dw^?1·d^?1) was correlated with seasonal and local N availability. The average rate of N release across all sites and dates (65.8±11.6 μ mol N·g dw^?1·d^?1) was 67% of gross daily uptake, and also varied among sites and seasons (range=33%–99%). Release was highest when growth rates and nutrient availability were low, possibly due to senescence during these periods. During summer biomass peaks, estimated N release from macroalgal mats was as high as 17 mmol N·m^?2·d^?1. Our results suggest that most estimates of macroalgal N uptake severely underestimate gross N uptake and that N is taken up, transformed, and released to the water column on short time scales (minutes–hours).     

PHYSIOLOGICAL VARIATION AND ELECTROPHORETIC BANDING PATTERNS OF GENETICALLY DIFFERENT SEASONAL POPULATIONS OF SKELETONEMA COSTATUM (BACILLARIOPHYCEAE)1

Clones of Skeletonema costatum (Grev.) Cl. isolated from Narragansett Bay, R.I., during different seasons were grouped according to their electrophoretic banding patterns. The growth rates, pg chlorophyll · cell^?1, carbon uptake · cell^?1· h^?1, and carbon uptake · pg chl^?1· h^?1 were measured at 20°C, in a 14:10 h L:D cycle at 180 μE · m^?2· s^?1. Statistically significant sources of variation were found among groups of clones in growth rate, pg chl · cell^?1, and carbon uptake · pg chl^?1· h^?1. It was concluded that there is a significant relationship between the physiological characteristics of clones isolated from populations in different seasons and patterns of genetic variation inferred from the electrophoretic studies. However, genetic diversity detected by banding patterns tends to underestimate the total genetic diversity in natural populations. The groups of clones most common in summer bloom populations had significantly higher growth rates, lower values of pg chl · cell^?1, and higher rates of carbon uptake · pg chl^?1· h^?1 at 20°C than did the group of clones most common in winter bloom populations. However, differences among groups in these parameters at 20°C alone cannot account for the seasonal cycling of genetically variable populations of Skeletonema in Narragansett Bay. The range of growth rates among clones of this species is 0.1–5.0 divisions · d^?1 under a single set of temperature and light conditions. Chlorophyll concentrations range from 0.2–1.7 pg chl · cell^?1 and carbon uptake · pg chl^?1· h^?1 varies by a factor of 7 among clones. The range of physiological variation in this species means that it is difficult to use laboratory studies of single clones to analyze the responses of natural populations of Skeletonema.     

Measurements of salmonid population performance in relation to habitat in eastern Newfoundland streams

The density, biomass and estimated production of brook trout Salvelinus fontinalis and Atlantic salmon Salmo salar were related to habitat factors in streams of Terra Nova National Park, Newfoundland, Canada. Fish communities at 29 sites (18 brooks; 15 watersheds) were sampled in the summer of 2002, 2003 and 2005. Salmonid density, biomass per unit area and production (derived from biomass and fish size using allometric P:B relationships) were compared with site habitat characteristics (wetted width, lactustrine habitat, per cent riffle habitat, canopy coverage and stream gradient), using an interactive stepwise multiple linear regression. Salmonid biomass (mean: 2·87 g m^?2; range: 0·33–10·88 g m^?2) and estimated production (mean: 3·05 g m^?2 year^?1; range: 0·32–10·98 g m^?2 year^?1) within the study area varied by an order of magnitude, however, habitat variables accounted for much of this variation. Specifically, wetted width and lacustrine area of the tributary played important roles in explaining density, biomass and production. Wetted width was important for all measurements of brook trout and total salmonids while lacustrine area was important for all measurements of Atlantic salmon and played a lesser role in total salmonid biomass. Other factors such as the percentage of riffle habitat, site gradient and canopy coverage provided modest improvements to the fit of some relationships. When models using the same environmental factors were compared, those using production estimates derived from allometric P:B equations in the literature provided improved predictive capability than did those from direct density and biomass estimates. It is proposed that allometric P:B relationships have utility in improving comparisons of stream fish communities, particularly in studies with insufficient resources to measure production directly.     

Macrobenthos of Accumulative Plains and Slopes of Ekspeditsii Bay (Pos'eta Bay,Sea of Japan)

The submarine accumulative plain of Ekspeditsii Bay is heterogeneous in terms of ground pattern and the composition and biomass of macrobenthos. The smallest values of the total biomass are characteristic of soft pelites (58.9 g/m²), siltstone pelites (55.9 g/m²), and pelites with an insignificant admixture of broken mollusk shells (108 g/m²). The greatest total biomass (649.2 g/m²) is registered around biogerms, in bottom areas composed of pelites with large fragments and entire valves of mollusk shells. On accumulative slopes of the bay, in the community of seagrasses, Zostera marina constitutes 90% of the biomass and macrofauna provides the remaining 10%. The values of the total biomass of macrobenthos of the accumulative plain and macroflora of the accumulative slopes of the bay are close to each other (about 12000 tons); however, both values are only 0.4 times as great as the biomass of macrobenthos on biogerms that occupy only 6.2% of the total bottom area in the bay.     

Interannual fluctuations in copepod abundance and contribution of small forms in the Drake Passage during austral summer

The relative importance of small forms of copepods has been historically underestimated by the traditional use of 200?C300-??m mesh nets. This work quantified the distribution and abundance of copepods, considering two size fractions (<300???m and >300???m), in superficial waters (9?m deep) of the Drake Passage and contributed to the knowledge of their interannual fluctuations among three summers. Four types of nauplii and eleven species of copepods at copepodite and adult stages were identified, with abundance values of up to 13 ind L^?1 and 28,300???g C m^?3. The <300-??m fraction, composed of Oithona similis, small cyclopoids and nauplii, dominated the copepod communities in the 3?years; it accounted for more than 77% of the total number and for between 40 and 63% of the total biomass. Changes in density and biomass values among the three cruises differed according to copepod size fraction and water mass; the >300-??m fraction showed no changes among the 3?years, both in Antarctic (density and biomass) and in Subantarctic waters (density), whereas the <300-??m fraction showed higher (density and biomass) values in 2001 both in Subantarctic and in Antarctic waters. Sea surface temperature and its anomaly accounted for the largest proportion of variability in copepod density and biomass, particularly for the <300-??m fraction.     

Abundance and biomass estimates of the benthic fauna in Admiralty Bay,King George Island,South Shetland Islands

Summary Quantitative benthic samples were collected along three transects in Admiralty Bay, King George Island, South Shetlands. At each of a total of 18 stations, between 15 and 250 m depth, we took 3 replicate samples with a van Veen grab. Animals collected were classed into major groups. Abundance and biomass per m² was calculated for each sampling site. Considerable population densities and high biomass values were found. Most abundant groups were Bivalvia, Polychaeta and Amphipoda, whereas the largest part of the biomass was due to Ascidiacea, Ophiuroidea, Echinoidea, Polychaeta and Bivalvia. The maximum abundance recorded was 36,000 ind m^-2 while the average was approximately 6500 ind m^-2. Maximum biomass was over 2400 g m^-2 with an average of ca. 700 g m^-2. The contribution to the total biomass by groups such as the Oligochaeta, Cumacea and Tanaidacea was higher in the inner shallow part of Admiralty Bay (Ezcurra Inlet) than in the deeper areas of the bay. Our results confirm the reports on an unusually high density and biomass of the Antarctic sublittoral benthic fauna. Sessile suspension feeders belonging to the Bivalvia, Ascidiacea, sedentary Polychaeta, and vagile scavengers of the Ophiuroidea, Amphipoda and errant Polychaeta are the most significant groups in the Antarctic Ecosystem. The total benthic biomass in Admiralty Bay, based on the present preliminary quantitative data, was estimated to be over 600,000 t. This value is probably still an underestimate.