Distribution of the under-ice mesozooplankton in the Kara Sea in February 2002

Mesozooplankton distribution was investigated under the sea ice in the Kara Sea at five stations in February of 2002 by Juday net hauls. Copepods dominated the mesozooplankton community, accounting for 46–88% of the total abundance and 68–99% of the biomass. Oithona similis was the most abundant species in Yenisei Bay, being present with all age stages (including egg-carrying females). For the first time, Oithona atlantica (CIII–CV copepodites, females and males) were found in the southeastern Kara Sea. In the southern part, Copepoda nauplii prevailed in terms of total abundance while the mesozooplankton in the northwestern part was entirely dominated by older stages of Pseudocalanus minutus. The mesozooplankton structure appears to be determined by available food resources and increased water temperature due to a strong influence of warm Atlantic waters.     

Distribution of capsulated bacterioplankton in the North Atlantic and North Sea

In laboratory experiments, bacterioplankton were incubated under different nutrient conditions, and the percentage of bacteria exhibiting a polysaccharidic capsule (capsulated bacteria) and that of CTC (cyanotetrazolium chloride)-positive and therefore metabolically highly active bacteria were determined. In these seawater cultures amended with nutrients more than 95% of the CTC-positive cells exhibited a capsule. During two cruises, one to the North Atlantic and one to the North Sea, we investigated the distribution of capsulated bacteria throughout the water column. Capsulated bacteria were generally more abundant in eutrophic surface waters than in deeper layers or more oligotrophic regions. In the upper 100 m of the North Atlantic, about 6–14% of the total bacterioplankton community was capsulated, while in the layers below 100 m depth, 97% of the bacteria lacked a visible capsule. The percentage of capsulated bacteria correlated with bacterial abundance and production, and chlorophyll a concentration. Also, the bioavailability of DOC (dissolved organic carbon), estimated by the ratio between bacterial production and DOC concentration, significantly correlated with the percentage of capsulated bacteria. In the North Sea, the contribution of capsulated bacteria to the total number of bacteria decreased from the surface (3 m depth) to the near-bottom (25–35 m) layers from 20% to 14% capsulated bacteria. In the nearshore area of the North Sea, about 27% of the bacteria exhibited a capsule. Overall, a pronounced decrease in the contribution of capsulated bacteria to the total bacterial abundance was detectable from the eutrophic coastal environment to the open North Atlantic. Using this epifluorescence-based technique to enumerate capsulated bacterioplankton thus allowed us to routinely assess the number of capsulated bacteria even in the oceanic water column. Based on the data obtained in this study we conclude that almost all metabolically highly active bacteria exhibit a capsule, but also some of the metabolically less active cells express a polysaccharide capsule detectable with this method.     

Distribution patterns of pelagic euphausiids in the East China Sea

Distribution patterns and abundance of the euphausiids were examined in the East China Sea (23°30′ –33°00′N, 118°30′ –128°00′ E) in relation to temperature and salinity. The data were collected in 4 surveys from 1997 to 2000. The density or yield density model was used to predict optimum temperature and salinity of water for euphausiid distribution, and thereafter distribution patterns of euphausiids were determined based on the predicted parameters. Of 23 species, Euphausia pacifica, E. nana, Pseudeuphausia sinica and P. latifrons were numerically dominant. The analyses indicate that Euphausia pacifica is an offshore temperate water species, E. nana is an offshore temperate warm water species, P. sinica is a coastal subtropical water species and P. latifrons is an oceanic tropical water species. The 4 species occupied 4 different water masses, respectively, namely, cold water mass, cold and warm water mixed masses in winter and spring, cold and warm water mixed masses in summer and autumn, and warm water mass, which could be the good designators of individual water masses, respectively. The predicated optimal temperatures for E. tenera, S. carinatum, E. diomedeae, Stylocheiron affine, Nematoscelis sp., N. gracilis, N. atlantica, Stylocheiron sp. and S. suhmii are all > 25°. These species are mainly distributed in southern Kuroshio in winter and spring, Kuroshio, the Taiwan Warm Current and Tsushima Current in summer and autumn, the equatorial waters of Pacific Ocean and the eastern waters of the Taiwan Strait. They are called as oceanic tropical water species. Nematoscelis tenella and T. tricuspidata are referred to as offshore subtropical water species according to their geographic distributions even if they are halobionts. Euphausia sanzoi is considered as a typical offshore subtropical water species, which inhabited waters below 25°. Stylocheiron microphthalma, occupying warm current waters where temperature and salinity are nearly 25° and 34 in summer and autumn, belongs to oceanic tropical water species. In the same way, E. similes, E. mutica, Euphausia sp., E. brevis and E. recurva are classified into offshore subtropical water species in accordance with the optimum temperature and salinity of waters as well as locations and seasons of their occurrence. Optimum temperature, rather than salinity, is a better parameter in determining the distribution patterns of euphausiids.     

东海浮游磷虾类的生态类型

根据1997～2000年东海23°30'～33°00'N、118°30'～128°00'E海域4个季节海洋调查,运用磷虾类物种丰度和同步的温、盐度资料,进行曲线拟合,构造数学模型,计算各种磷虾分布的最适温度和盐度,并参考其地理和季节分布特征,对东海浮游磷虾类生态类型进行定量分析.结果表明,在磷虾优势种中,太平洋磷虾(Euphausia pacifica)是温带外海种,小型磷虾(E. nana)是暖温带外海种,中华假磷虾(Pseudeuphausia sinica)是亚热带近海种,宽额假磷虾(P. latifrons)是热带大洋种.这些物种的高丰度区依次代表黄海冷水团,冬春季的混合水团,夏秋季的混合水团和暖流水团的位置,是良好的水团指示种.柔弱磷虾(E. tenera)、隆柱螯磷虾(Stylocheiron carinatum)、长额磷虾(E. diomedeae)、近缘柱螯磷虾(S. affine)、Nematoscelis sp.、瘦线脚磷虾(N. gracilis)、长线脚磷虾(N. atlantica)、Stylocheiron sp.、三晶柱螯磷虾(S. suhmii)和二晶柱螯磷虾(S. microphthalma)是热带大洋种.娇嫩线脚磷虾(Nematoscelis tenella)、三刺燧磷虾(Thysanopoda tricuspidata)、大眼磷虾(E. sanzoi)、拟磷虾(E. similis)、鸟喙磷虾(E. mutica)、短磷虾(E. brevis)、卷叶磷虾(E. recurva)和Euphausia sp.是亚热带外海种.在确定磷虾类生态类型过程中,最适温度具有更好的参考价值.     

Long-term dynamics of main mesozooplankton species in the central Baltic Sea

Long-term dynamics (1959–1997) of the copepod speciesPseudocalanus elongatus, Temora longicornis, Acartia spp. andCentropages hamatus, as well as the taxonomic group of cladocerans,are described for the open sea areas of the central Baltic Sea.Differences between areas, i.e. Bornholm Basin, Gdansk Deepand Gotland Basin, as well as between 5 year periods, were investigatedby means of Analysis of Variance (ANOVA). No significant differencesin mesozooplankton biomass between areas were found. On theother hand, clear time-trends could be demonstrated and relatedto salinity and temperature, with P.elongatus biomass mainlydependent on salinity and T.longicornis, Acartia spp. and cladoceransbiomasses dependent, to a large extent, on thermal conditions.Decreasing salinities since the early 1980s due to a lack ofmajor inflows of highly saline water from the North Sea andincreased river run-off, both triggered by meteorological conditions,obviously caused a decrease in biomass of P.elongatus. Contrarily,the standing stocks of the other abundant copepod species andcladocerans followed, to a large degree, the temperature developmentand showed, in general, an increase. The shift in species compositionduring this period is considered to be a reason for decreasinggrowth rates of Baltic herring (Clupea harengus) since the early1980s, and for sprat (Sprattus sprattus) since the early 1990s.Generally, it is suggested that low mesozooplankton biomassesin the 1990s were caused, at least partially, by amplified predationby clupeid fish stocks.     

Estimations of mesozooplankton biomass in a coastal upwelling area off NW Spain

The abundance and several estimators of mesozooplankton biomass(dry weight, ash-free dry weight, displacement volume, carbonand nitrogen) were measured in a coastal upwelling area offLa Coru*****na (NW Spain) at monthly intervals between 1990and 1995. Holoplanktonic copepods dominated in most of the samples,but meroplanktonwere also important near the coast, especiallyduring late spring and through summer. Gelatinous organisms(medusae, siphonophores and larvaceans) reached significantabundances (-10%) in shelf waters by late summer, but also nearthe coast in spring. Log-linear equations were computed betweendry weight, displacement volumeand the other biomass estimators,to allow for interconversion among different measurements. Toprevent the influence of meroplankton and gelatinous zooplanktonin the estimations of biomass, the equations were adjusted usingonly samples in which the abundance of each of these groupswas <10% of total individuals. Our equations produced carbonand ash-free dry weight estimates that are comparable to thoseobtained with the ratiosgiven in other studies in the region.However, the esti mations of mesozooplankton carbon from displacementvolume using the adjusted equation with our data are lower thanthose reported previously for the area, which werecomputed usingequations adjusted with data from a different ecosystem. Theuse of interconversion factors taken from the literature isdiscussed, along with the implications of the estimations ofmesozooplankton biomass in the computations of the flux of carbonthrough the ecosystem.     

Distribution patterns of bacterioplankton and chlorophyll-a in the German Wadden Sea

 In a first synoptic evaluation, the temporal and spatial distribution of bacterioplankton and chlorophyll-a were determined in the German Wadden Sea. Three surveys were undertaken in winter, spring, and summer of 1994 using up to eight ships simultaneously between the river Ems and Sylt island. Despite intensive hydrodynamic mixing of the Wadden Sea water, spatial gradients were obvious. The abundance of bacterioplankton ranged from 0.4 to 26×10⁵ ml^–1 and chlorophyll-a varied between <0.1 and 79 μg l^–1. In winter, relatively homogeneous distribution patterns of both parameters with small gradients were found. Highest chlorophyll-a values connected with a highly patchy structure were observed in spring, while in summer both total chlorophyll-a values and the complexity of the distribution pattern had decreased. In contrast, bacterial numbers increased steadily from January to July with the highest bacterial densities and greatest patchiness observed in summer. Moreover, in some regions of the Wadden Sea, a trophic succession of algae as carbon producers and bacteria as consumers was evident. Correlation analysis verified the relationship between bacteria and chlorophyll a, indicating bottom-up control of bacterial abundance in the northern part of the German Wadden Sea. Since the observed regression slope is remarkably low (0.12–0.46) compared to literature values (0.5–0.8), we suggest that the link between phytoplankton and bacteria found here is a special characteristic of the Wadden Sea as a transition zone between the coastal region and the outer North Sea. Received: 26 May 1998 / Accepted:12 November 1998     

长江口北港和北支浮游动物群落比较

根据2004年5、8、11月和2005年2月在长江口4个航次的海洋综合调查,通过物种多样性、累积优势度曲线等群落水平指标和相似性检验分析(ANOSIM),对长江口北港和北支浮游动物群落及其主要优势种的差异,以及主要生态因子对浮游动物群落的影响进行了分析.结果表明：北港主要由潮汐影响的淡水和低盐水组成,北支由中、高盐水组成.春季,北港浮游动物丰度和多样性均低于北支,主要优势种为中华华哲水蚤;北支浮游动物优势种数较多,主要优势种为真刺唇角水蚤.夏季,北港和北支的多样性较接近,但种类组成差别较大,北港以中华华哲水蚤为主;北支由火腿许水蚤、虫肢歪水蚤和太平洋纺锤水蚤等构成河口和近岸群落.秋季,北港的丰度和多样性均低于北支,且两个水域的浮游动物群落差异明显,北港以中华华哲水蚤为主,北支则由小拟哲水蚤、针刺拟哲水蚤、真刺唇角水蚤和中华哲水蚤等组成.冬季,两个水域种数和多样性均较低,群落差别在四季中最小,均以中华华哲水蚤占绝对优势.温度和盐度及其相互作用是决定长江口浮游动物群落特征的最主要因素.其中温度是研究水域浮游动物群落季节变化的主要因素,而由径流和外海水之间的消长引起的盐度变化是北港和北支浮游动物群落区域变化的决定因素.     

Spatial variability of the mesozooplankton biomass and ichthyoplankton in the Canary region, in autumn 1991

In this paper, we study whether the variability introduced inthe Canary region by the Canary Islands on perturbing the generalflow of the Canary Current and trade winds, and by the NorthwestAfrican upwelling, is manifested in the mesozooplankton biomassdistribution and ichthyoplankton population. Two transects weresampled and two stations were occupied for 24 h during the firstpart of the cruise Canarias 9110. One transect and one stationwere located to the north, upstream of the Canary Islands, inthe ‘non-perturbed’ zone, and the other transectand station were to the south, downstream of the islands, inthe ‘perturbed’ zone. Oceanographic conditions,as represented by the vertical temperature structure, changedboth latitudinally, between upstream unperturbed and downstreamperturbed conditions, and longitudinally, between upwellingand oceanic situations. However, differences were evident onlyin mesozooplankton biomass and in the latitudinal sense. Likewise,the results obtained suggest that (i) there is an interconnectionbetween the neritic fish populations of the Macaronesian archipelagos,in a north–south sense and in a southerly direction, bymeans of the transport of fish larvae by the Azores and Canarycurrents, and (ii) this interconnection could affect both thosespecies whose larvae are well adapted for a long survival inthe pelagic environment, possessing morphological specializations,and those whose larvae do not present these characteristics.     

Annual pattern of micro- and mesozooplankton abundance and biomass in a subtropical estuary

The pattern of biomass and abundance of microzooplankton andmesozooplankton were studied over an annual cycle in the NuecesEstuary, Texas. Zooplankton samples and associated hydrographicdata were collected at four locations at biweekly intervalsfrom September 1987 through October 1988. This is a broad, shallowbay system with an average depth of 2.4 m. The concentrationof chlorophyll a in the surface waters averaged 7.4 µgl^–1with 85% passing through a 20 µ mesh. Microzooplankton(20–200 µ in length) were extremely abundant throughoutthis study. Abundances of ciliates (including both aloricateciliates and tintinnids) ranged from 5000 to 400 000 l^–,with a mean of 38 000 l^–1 of seawater over the entirecourse of the study. Mesozooplankton (200–2000 µmin length) abundance averaged 6100 m^–3 for samples collectedduring the day and 10 100 m^–3 for samples collected atnight. Mesozooplankton were dominated by Acartia tonsa whichmade up {small tilde}50% of the total. Biomass estimates formicrozooplankton (based on volume estimates) were often higherthan measured biomass of mesozooplankton. Given the shortergeneration times and higher metabolic rate of microzooplanktoncompared to mesozooplankton, microzooplankton should have agreater effect on the trophic dynamics of the Nueces Estuarythan mesozooplankton.     

Vertical distribution of mesozooplankton in the central and eastern Arabian Sea during the winter monsoon

The vertical distribution of mesozooplankton in the centraland eastern Arabian Sea was investigated during the winter monsoonin 1995. Samples were analysed from discrete depth zones definedaccording to oxygen and temperature profiles of the water column.Zooplankton had higher standing stock in the mixed layer comparedto the strata below. The mixed layer had 78.5% of the totalcolumn biomass, while the deepest (500–1000 m) layer accountedfor only 0.9%. The stratum between 500 and 1000 m had the lowestabundance of copepods as well as other zooplankton. A notablefeature was that zooplankton biomass and density did not showmuch variations between coastal and offshore regions. Copepodawere the dominant group. Herbivores were generally more abundantat all depths. A total of 94 species of calanoid copepods wereidentified. Based on vertical distributions, they were assignedto four groups: (i) species restricted to the upper 200 m; (ii)predominantly surface-living species with tails to deeper waters;(iii) sparser deeper-living species generally confined below300 m; (iv) species occurring throughout the water column. Diversitywas fairly high in all strata with equitability being higherin the deeper strata.     

The distribution of bacterioplankton and mesozooplankton biomass in the White and Barents Seas coastal water

The total population density and the biomass of bacterioplankton, mesozooplankton, and phosphate-accumulating bacteria (PAB) were estimated during the 2000-2001 summer-autumn seasons in the coastal waters of the White and Barents Seas, which are subjects to the action of tidal and sea currents, the inflow of riverine waters, and anthropogenic impact. In the shallow estuarine waters with salinities of 6.5-32@1000 near the Chernaya, Pesha, and Pechora River mouths, the population of PAB fluctuated from 0.1 to 9.1 million cells/ml (0-36% of the total bacterial population). In pelagic seawaters, which are low in phosphates (12-50 micrograms/l) and are characterized by an increased iron/phosphorus ratio (2.0-3.6), bacterioplankton amounted to 0.1-1.6 million cells/ml and was mainly represented by small organisms with a volume of 0.08-0.15 micron 3, commonly lacking intracellular polyphosphates. In the pelagic zone of the Barents Sea, the biomass of mesozooplankton (Bz) was comparable with that of bacterioplankton (Bb = 39-175 mg/m3), the Bb/Bz ratio being 1.4-4.6. Off the Varandeiskii, Pechora, and Kolguyev oil terminals, Bb increased to 155-300 mg/m3 and the Bb/Bz ratio rose to 1.4 to 50.3 (with an average value of 20.9), presumably due to the severe anthropogenic impact on these waters. In this case, the dense population of bacterioplankton (0.9-7.6 million cells/ml) was mainly represented by large cells (0.12-0.76 micron 3 in volume), most of which (3-43% of the total bacterioplankton population) contained polyphosphates. The chemical composition of these waters was characterized by an elevated content of the total phosphorus (65-128 micrograms/l) and by a low iron/phosphorus ratio (0.9-1.2).     

Vertical mesozooplankton abundance and distribution in the deep Eastern Mediterranean Sea SE of Crete

Mesozooplankton from the Levantine Basin, Eastern Mediterranean,were analysed for composition and vertical distribution fromthe surface to 4000 m, with special emphasis on calanoid copepods.Copepods were dominant, ostracods and chaetognaths ranked next.Zooplankton abundance and biomass were highest in the top 100m layer. A secondary concentration maximum was between 450 and750 m. The exponential decrease of zooplankton with depth wasstronger than in the open ocean, but less strong than in theRed Sea. Similarly to the Red Sea, three genera among calanoidcopepods were predominant in the deep sea. As with the WesternMediterranean, but different from the Red Sea, populations ofmesopelagic and one bathypelagic species were found to occurwell below 1250 m to depths of at least 3000 m. Similarly toboth seas, long-range vertical migrators were rare, those presentmainly belonging to the genus Pleuromamma, and diel migrationswere restricted to the upper 600 or 1000 m. Due to the hightemperatures in the deep water bodies of the Levantine and RedSeas, the decomposition of sedimentary particles is assumedto be accelerated. This prevents much detritus from reachingthe sea floor which may explain the anomalous low abundancesof deep-sea zooplankton and benthos. Though the similaritiesto the Red Sea seem to be strong, the Levantine Sea is likelyto hold an intermediate position between the open ocean andthe Western Mediterranean on one side and the Red Sea on theother side.     

Summer mesozooplankton distribution near Novaya Zemlya (eastern Barents Sea)

Regional variations in mesozooplankton composition, abundance and biomass were studied during a cruise in August 2006 near Novaya Zemlya Archipelago (eastern Barents Sea) using Juday net hauls from the bottom (or 100 m depth) to the surface. A comparison with multiannual literature values revealed that the mean temperature and salinity in the south and centre of the study area were similar to typical values, while temperature in the north was significantly higher. A total of 36 species and higher taxa were identified. Mesozooplankton abundance and biomass varied from 47 to 851 ind m⁻³ and from 5 to 74 mg dry weight m⁻³, respectively. Copepods dominated the mesozooplankton community, reaching 73–98% and 61–97% of the total abundance and biomass. Calanus finmarchicus and Oithona similis were the most abundant species at all stations. The biodiversities (Shannon indices) of the mesozooplankton community varied between stations from 1.10 to 2.46 (estimated from species abundances) and from 0.19 to 1.92 (estimated from species biomasses), averaging 1.93 ± 0.127 and 1.34 ± 0.151, respectively. Three groups at the 48% level of dissimilarity of species abundance were delineated by cluster analyses. The clusters differed significantly with respect to temperature and salinity. The total mesozooplankton abundance and biomass as well as quantitative parameters of most common taxa scaled negatively with temperature.     

Distribution, diversity and biomass of summer zooplankton from the coastal Canadian Beaufort Sea

Composition, abundance, biomass and distribution of zooplankton in the coastal Canadian Beaufort Sea were studied in the summer of 2005 and 2006. Data were collected from two cross-shelf transects (11 stations in each). Sampling was conducted with vertical hauls using a conical net of 153-μm mesh size. Our results revealed that there are three ecological zones, Intense Plume, Diffuse Plume and oceanic, which are primarily shaped by the highly variable Mackenzie River plume. The Intense Plume Grouping was located at stations influenced greatly by the Mackenzie River, where Podon leuckarti, Pseudocalanus spp., Copepoda nauplii and Limnocalanus macrurus were most abundant. The Diffuse Plume Grouping, that was located in the transitional zone between the river plume and the ocean, had the highest diversity. This grouping was characterised by high abundance of Copepoda nauplii, Polychaeta larvae, Pseudocalanus and L. macrurus. The Oceanic Grouping, located farthest from shore beyond the 85-m depth contour, was mainly inhabited by marine taxa—Calanus glacialis, C. hyperboreus, Triconia (Oncea) borealis and Microcalanus spp.—and had the greatest overall zooplankton abundance and biomass of all groupings.     

甲藻孢囊在长山群岛海域表层沉积物中的分布

2007年10月,在大连长山群岛海域采集了25个站点的表层沉积物,研究了甲藻孢囊的水平分布。在沉积物样品中共检测出甲藻孢囊46种,其中Pentaphasodinium dalei和Warowia rosea,在我国是首次报道。各站位孢囊种类数在7-20之间,平均14种;丰度在182-2960 个/g干重之间,平均为1201 个/g干重。香农-威纳指数(H')的变化范围为2.4-3.4。麻痹性贝毒藻--亚历山大藻的孢囊在调查海域分布广泛,最高密度达829个/g干重,可能是造成该海域虾夷扇贝贝毒超标的原因之一。