Significance of tintinnid grazing during blooms of Phaeocystis pouchetii (haptophyceae) in Dutch coastal waters

Extremely dense populations of tintinnids (24 000 to 118 000·dm⁻³) were found during the spring bloom of the alga Phaeocystis pouchetii in the Dutch Wadden Sea and coastal North Sea. Microscopic observations showed that these Protozoa grazed on the single-cell stage of the colony-forming Phaeocystis. At the end of the bloom, the biovolume of the tintinnid population equalled or even exceeded that of the Phaeocystis population, indicating that microfaunal grazing prevented further growth of the Phaeocystis spring bloom.     

Increased phytoplankton primary production in the Marsdiep area (Western Dutch Wadden Sea)

Annual phytoplankton primary production in the Marsdiep tidal inlet increased from ca 150 gC·m⁻² in the period 1964 to 1976, to ca 300 gC·m⁻² in 1981/1982 and 1985. This increase is considerable, but comparable to that observed in the outer Ems estuary, eastern Wadden Sea, from 240 gC·m⁻²a⁻¹ in 1972/1973 to 400–500 gC.m⁻².a⁻¹ in 1976/1980. Although the increase is most probably due to eutrophication, as illustrated by the regular increase in phosphate in the Marsdiep area since 1950, it is difficult to explain why this affected primary production not earlier than the late seventies. Primary production has probably not increased in the more turbid inner parts of the Wadden Sea, where light is the limiting factor, and P values were already higher than in the inlet areas.     

The spring bloom of phaeocystis pouchetii (haptophyceae) in Dutch coastal waters

A Phaeocystis pouchetii (Harlot) Langerh. bloom, which contained up to 22×10⁶ cells ·dm⁻³, occurred in the spring of 1984 along the Dutch coast of the North Sea. The largest cell numbers of P. pouchetii were observed near the coast, with cell numbers decreasing towards the open sea. In contrast to a shark peak in the cell numbers along the coast in May, P. pouchetii cell numbers in the open sea slowly increased towards June.During a preceding bloom of diatom, P. pouchetii was already present from an early stage onwards while at the end of the P. pouchetii bloom a high percentage of the cells was observed as microflagellates.The distribution of dissolved nutrients (Si, N, P) showed a typical pattern with highest values near the coast, apparently due to the Rhine outflow, and a gradual decrease towards the open water. This distribution pattern coincided with particular stages of the P. pouchetii bloom. Whereas growth of the P. pouchetii population may be due to increasing temperature and irradiance, its decline is probably caused by phosphate limitation.Total primary production measured at one station and based on short term ¹⁴C incubation experiments was 121 gC·m⁻² for the period 17 March to 20 May with a daily rate of production of up to 4.8 gC·m⁻². The mean proportion of extracellular carbon release based on 4 h incubation periods was 7.5%.     

Chemical and physiological changes of phytoplankton during the spring bloom,dominated by phaeocystis pouchetii (Haptophyceae): observations in Dutch coastal waters of the North Sea

During the spring bloom of phytoplankton in Dutch coastal waters of the North Sea the flux of ¹⁴C-labelled products into pools of protein, polysaccharides, small metabolic intermediates and lipids was studied. The molecular size distribution of extracellular products, amounting to 28% of the particulate production, was determined by gel filtration. Concentrations of protein and carbohydrates were determined in the same phytoplankton samples. At an early stage of the bloom protein synthesis and protein concentration dominated over carbohydrate synthesis and carbohydrate concentration, but after the peak of the bloom carbohydrates were the predominant photosynthetic endproduct. These observations have been compared to similar observations on unialgal cultures of Phaeocystis pouchetii. The influence of phosphate depletion on the extracellular release of organic compounds and the impact of the colonial growth form of Phaeocystis pouchetii on the distribution of intra- and extracellular labelled compounds are also discussed.     

Chattonella and Fibrocapsa (Raphidophyceae): First observation of,potentially harmful,red tide organisms in Dutch coastal waters

Species of the potentially toxic and red-tide-forming marine-phytoplankton genera Chattonella and Fibrocapsa (Raphidophyceae) were observed for the first time in 1991 in samples taken in Dutch coastal waters; they were again recorded and enumerated in the following years. Chattonella spp. cell numbers varied with the season, with a maximum in May or June in the Dutch Wadden Sea. Cell numbers of Chattonella and F. japonica Toriumi et Takano were up to 6.0·10³ cells·dm⁻³ in the Dutch Wadden Sea, except at one station in June 1993 when over 10⁴ cells·dm⁻³ Chattonella were counted. In May 1993, a minor bloom (over 2.0·10⁵ cells·dm⁻³) was observed at a station in the southern central North Sea, 100 km northwest of the island of Terschelling. The potentially neurotoxic species Chattonella marina (Subrahmanyan) Hara et Chihara was identified and discriminated from morphologically related species within the class of Raphidophyceae by immunofluorescence. F. japonica could only be clearly identified in live samples; in fixed samples cell morphology was severely affected. The identification of this species was supported by the presence of mucocysts, structures that can be observed readily by optical and electron microscopy.     

Phytoplankton primary production,chlorophyll and composition in an inlet of the Western Wadden Sea (Marsdiep)

From February 1974 to April 1976, estimates for in situ phytoplankton primary production in the Marsdiep tidal inlet area of the western Dutch Wadden Sea were made from incubator primary production data using a constant light source. Low values were estimated in winter with a minimum in January (average 0.016 g C·m⁻²·d⁻¹. Values increased rapidly from the middle of March during the spring phytoplankton bloom to a maximum in May (average 1.1 g C·m⁻² ·d⁻¹, maxima of 3 g C·m⁻²·d⁻¹ or more). During summer these estimates showed large short-term variations in in situ primary production from incubator data as well as in in situ measurements during 1 to 3 days in June and August in the years 1971 to 1979. This variability forms a problem in estimating annual phytoplankton primary production in the area. It also prevents a reliable comparison of the present estimate with earlier estimates of annual primary production based on fewer data (one per month or less). It is likely that also in other areas, in particular in coastal regions, similar difficulties in estimating primary production will be encountered.     

Primary production of phytoplankton in a turbid coastal plain estuary,the Westerschelde (The Netherlands)

An extensive survey was carried out in the Westerschelde estuary in 1989 to estimate phytoplankton primary productivity. High nutrient concentrations year round and very high turbidity resulted in light-limited growth of phytoplankton. This was reflected in a conservative behaviour of silicate and phosphate. The same was true for total inorganic nitrogen. However, in the inner part of the estuary nitrification took place. The calculated annual primary production was 200 – 300 gC·m⁻² at the range 29-20 salinity, 100–150 gC·m⁻² at 18-10 salinity and increased sharply to 900 gC·m⁻² at 2.5 salinity due to freshwater populations. In the inner part of the estuary the vertical mixing zone was frequently larger than 5 times the euphotic zone. The high rates of primary production we measured contrast with generally expected values. This corroborates Grobbelaar's hypothesis that the critical depth can be seriously underestimated. Phytoplankton copes with the turbid conditions by adjusting light-utilization efficiencies.     

The determination of suspended metals in coastal waters by different sampling and processing techniques (filtration,centrifugation)

The concentrations, on a sediment weight basis, of several metals in coastal suspended matter show a marked dependence on the amount of particulate matter per litre. The effects of filtration and centrifugation are compared. The resulting data are interpreted in terms of varying contributions of larger and denser bottom derived particles with higher concentrations of K, Fe, Mn, and Al and of smaller and less dense, continuously suspended particles with higher concentrations of Cu, Cd, Pb and Zn. No dependence on size or density was found for Cr, Si, Mg and Ca.Filtration results in higher concentrations of Cu, Cd, Pb, and Zn. For the other elements, centrifugation results in concentrations that are at least similar to those in particulates obtained by filtration, or even larger for elements with relatively large difference between the concentrations in the different fractions, such as K. Leaching particulates, obtained by filtration and centrifugation, with 0.1 N HCl leads to differences in the leached fractions for Cd, Cr, K and Mg at lower suspended loads, and for Fe at higher loads, while no differences are observed for Cu, Pb, Zn, Si, Mn, Al and Ca.Accurate particulate metal concentration data were obtained by measuring in each individual sample, the amount of both metal and particulate matter. This results in more accurate data than can be obtained by measuring each of the properties in separate samples. Another source of errors is eliminated by analyzing the entire content of a sampler in stead of part of it, because of sample inhomogeneity introduced by settling of particles in the sampler.In order to get accurate sediment weight data at low suspended matter concentrations, sea salt was removed from the particulate matter by a rinsing procedure with distilled water. No loss of the metals investigated (Cu, Cd, Zn, Cr, Si, Fe, Mn, and Al) was evident with a possible exception for Cd.     

Oxygen regime,respiratory activity and biomass of microorganisms,and the carbon budget in the Fladen Ground area (Northern North Sea) during spring

A watermass, on the Fladen Grounds, marked with a drifting buoy, was studied daily during one month in spring. Hydrographic parameters, nutrient regime, oxygen regime, biomass of microorganisms and respiratory activity were determined; the high variability of the observations is discussed. From these observations, and earlier publications on the same cruise, a carbon budget is calculated. From oxygen flux calculations it appeared that the net ecosystem production must be more than 2.5 g C m⁻².d⁻¹ which could not be verified by C-14 primary production measurements. Presumably high variability in the system in time and space makes it impossible to get a fitting budget.     

Input of selected chlorinated hydrocarbons into the coastal area of East Java and adjacent waters: Distribution patterns in the dissolved and suspended phase

Selected organochlorines were analysed in water and suspended particulate matter collected at stations in two rivers on East Java, the adjacent coastal zone, the Java Sea and the Indian Ocean. The sampling period covered the dry monsoon and the beginning of the wet monsoon. Concentrations of dissolved polychlorinated biphenyls (PCBs) were in the same range as in Western Europe and North America. In contrast, the concentrations of all measured organochlorines in suspended matter were lower and often not detectable.p,p′-DDT and its metabolites p,p′-DDD and p,p′-DDE showed the highest concentrations of all compounds determined. The rivers Bengawan Solo and Kali Porong can be considered sources of these compounds for the coastal environment, although their impact is restricted to a small area.Significant differences between the dry and wet monsoon were only observed for dissolved PCBs in the river Porong.     

Changes in spatial distribution of primary production,photosynthetic pigments and phytoplankton species composition during two surveys in the German bight

A grid of 61 stations was sampled twice in the German Bight. At all stations dissolved nutrients (Si, P, N), fluorescence, temperature and salinity were measured along the vertical at surface, 5 m, 10 m, and 10 m intervals till the bottom. At selected stations photosynthetic rates were measured with ¹⁴C method (both surveys) and pigment with a HPLC method (first survey). Phytoplankton species composition was dominated by small diatoms, mainly Leptocylindrus minimus, flagellates, both dinoflagellates and choanoflagellates and near shore blooms of Phaeocystis pouchetii. Primary production and chlorophyll-a showed a linear correlation (r=0.90, n=23). Primary production showed highest rates along the North and East Frisian islands, where phytoplankton was dominated by Phaeocystis and Leptocylindrus. These coastal stations were completely mixed whereas a large part already showed stratification due to salinity and temperature. Thermocline and pycnocline were at about 10 m depth. No differences in oxygen content of surface or bottom waters were observed. Silicate and phophate concentrations were very low whereas nitrogen still showed very high concentrations. Low hypolimnetic oxygen concentrations are only possible when transport of primary produced organic matter is transported to stratified regions later in summer. Rapid growth of blooms was observed within a weeks period. More primary production measurements in the German Bight should be done to allow for budget calculations of oxygen consumption below the thermocline.     

鸭绿江下游（丹东段）冬春季鱼类种类组成及区系特征初步研究

为补充和完善鸭绿江下游鱼类资源状况的基础资料,了解近年调查区域的鱼类组成特征,采用定性与定量相结合的方法,通过实地现场调查与渔获信息采集的方式,于2011年11月至2012年5月对鸭绿江下游（丹东段）的鱼类种类组成及其区系特征作了初步分析,结果表明：调查区域发现鱼类33种,其中鲤形目最多（12种）,鲈形目次之（8种）;鱼类区系组成较为复杂,土著鱼类占优势,温水性鱼类占优势,喜稳水或缓流水的鱼类占优势;鱼类区系在洄游习性、适温性和摄食习性上表现为不同的生态类型。鸭绿江下游丹东河段鱼类群落表现为河口鱼类群落类型,部分物种种群数量急剧减少、迁徙或者消失,鱼类种质资源较为珍贵,建议进一步加强鸭绿江下游的生态环境保护,注意水质污染控制。     

The light and temperature dependence of growth rate and elemental composition of Phaeocystis globosa scherffel and P. Pouchetii (HAR.) Lagerh. in batch cultures

The light and temperature dependence of growth, cellular elemental composition (C, N, P) and chlorophyll content during exponential growth and phosphate starvation of batch cultures of the temperate algal species Phaeocystis globosa were investigated. Temperature-dependent minimum generation time and cell phosphorus content were compared with those of the cold water species P. pouchetii. The variation in growth and cell carbon content was due to the different origin of seawater used for the culture media. Coastal, estuarine seawater enabled shorter doubling times than “offshore” and oceanic-influenced seawater. At nutrient-saturated growth, P. globosa was able to compete with diatoms only if high temperature (14°C) and high irradiances (180 μE·m⁻²·s⁻¹) predominated. P. pouchetti showed markedly shorter generation times than P. globosa did at temperatures below 10°C. At 6°C, the cell carbon content exceeded the value at 18°C by a factor of 1.7. High C/N atomic ratios of 6.9±0.7 and high C/Chl a ratios of ≥ 54.0 during exponential growth could not entirely be explained by the carbon content of the colony mucus. There was no significant light and temperature dependence of the : N : P ratio during exponential growth. At phosphate starvation (subsistence P quota of cells) this was so only at temperatures higher than 10°C. With their stored phosphorus quota P. globosa and P. pouchetii were capable of only two cell divisions. Hence, because of their limited ability to store phosphorus, the two Phaeocystis species cannot compete with planktonic diatoms for growth. The frequent change in nutrient concentrations (particularly of silicate and phosphate) in coastal and estuarine waters at summer temperatures and light conditions causes a rapid alternation of smaller blooms of P. globosa and diatoms.     

Monsoonal alternation of a mixed and a layered structure in the phytoplankton of the euphotic zone of the banda sea (Indonesia): a mathematical analysis of algal pigment fingerprints

The chlorophyll a concentration of the upper 25 m of the euphotic zone of the Banda Sea was 5 times higher in August 1984, in the upwelling season during the southeast monsoon, than in February 1985, during the northwest monsoon when a deep chlorophyll maximum layer was presented at 40–80 m. Similarity between stations was calculated by means of a cluster analysis of the concentrations of 4 different chlorophylls and 6 carotenoids. High similarity over large areas, one to the west and one to the east of the Banda Arc, is evidence of the importance of large-scale phenomena influencing the phytoplankton during the monsoons. All samples taken in the deep chlorophyll maximum layer during the northwest monsoon were clustered as a separate group.Multiple regression analysis of chlorophyll a and the four most important accessory pigments suggests that in August 1984 (upwelling season) the fucoxanthin-containing group (mainly diatoms) contributed 50% to the chlorophyll a in the euphotic zone; green algae and Prymnesiophyceae contributed each 20%, Cyanobacteria only 9%. In February 1985, during the downwelling season, pico- and nanoplankton containing 19'-hexanoyloxyfucoxanthin (Prymnesiophyceae) and zeaxanthin (Cyanobacteria) each contributed 40% of total chlorophyll a, both near the surface and in the deep chlorophyll maximum layer; 19'-butanoyloxyfucoxanthin (a marker of certain Prymnesiophyceae and Chrysophyceae) was only present at depth. On the assumption that Chl. b is a pigment confined to green algae, this group contributed 14% of the Chl. a in the deep maximum. Other green-algal pigments were, however, scarce at depth (lutein, violaxanthin), which suggests presence of Prochlorophyta.Shifts in pigment ratios (zeaxanthin : Chl. a; Chl. b : Chl. a), probably related to light adaptation, hinder the use of algal pigment fingerprints for estimating quantitative composition of natural phytoplankton; indeed, differences between samples in pigment signature can have both a floristic and an ecophysiological background. Statistical analysis of pigment fingerprints may further be complicated due to presence of intermediates of pigment synthesis and breakdown, and poor taxon specificity of fucoxanthins and possibly even of Chl. b and zeaxanthin.     

An Assessment of Variation for Nutritional and Non-nutritional Carbohydrates in Lentil Seeds (Lens culinaris)

The levels of the raffinose family of α-galactosides (raffinose, stachyose, verbascose and ciceritol) and of the nutritional carbohydrates (fructose, sucrose and starch) were determined in the seed of a range of lentil lines from germplasm collections and commercial Spanish cultivars. Significant levels of variation were found for all the measured characters, and particularly for the α-galactosides. The greatest variation was found in verbascose content, which ranged from about 1 % of the seed dry weight to undetectable amounts. The relationship between these chemical components and morphological seed characteristics was assessed. The only significant relationship between the different groups of characteristics was a positive correlation between the level of verbascose and the average seed weight for each genotype.     

Cell wall disassembly during papaya softening: Role of ethylene in changes in composition,pectin-derived oligomers (PDOs) production and wall hydrolases

Cell wall disassembly in ripening climacteric fruit is a highly complex process where ethylene plays a crucial role. Ethylene inhibitors can be used to explore the changes in the cell wall matrix and cross-linked polysaccharides in ethylene-regulated processes. The results of applying the ethylene receptor blocking inhibitor 1-methylcyclopropene (1-MCP) and the ethylene-releasing compound ethephon (2-chloroethylphosphonic acid) indicate that softening of ‘Maradol’ papaya fruit is dependent on ethylene. When fruit were induced to ripen extensively by exposure to a high dose of ethephon, 1-MCP inhibited the subsequent softening dramatically, but when inhibition of the ethylene response was caused by application of 1-MCP, subsequent fruit treatment with ethephon promoted extensive loss of galactose from the water-soluble polysaccharides, but this was not accompanied by fruit softening. The cell wall changes accompanying normal fruit softening were pectin solubilization and polyuronide depolymerization and these processes occurred simultaneously. Polygalacturonase likely is responsible for the ripening-associated changes in ‘Maradol’ papaya fruit texture and pectin polymer integrity. An increase in extractable fruit polygalacturonase follows the increased presence of pectin-derived oligosaccharides.     

Identification of molecular markers associated with oleic and linolenic acid in spring oilseed rape (Brassica napus)

The quality of the oil derived from oilseed rape is determined by its fatty acid composition. Breeding oilseed rape for enhanced oil quality includes the development of cultivars with high oleic and low linolenic acid. Random amplified polymorphic DNA (RAPD) and intersimple sequence repeat (ISSR) techniques were investigated for the development of molecular markers for genes controlling oleic and/or linolenic acid. Markers that were identified were converted to sequence characterized amplified region (SCAR) markers for use in breeding. Molecular markers associated with these two fatty acids were identified in a doubled haploid population derived from a cross between the oilseed rape lines TO99‐5318‐20, very high oleic (>79%) and very low linolenic acid (<2%) × DH12075, high oleic (68%) and higher linolenic acid (>7%). Eight RAPD markers were associated with oleic and linolenic acid contents. The RAPD marker UBC 2₈₃₀ accounted for 43% and 13% of the genetic variation for oleic and linolenic acid levels, respectively. The RAPD marker UBC 153₅₅₀ accounted for 19% of the genetic variation for linolenic acid. The UBC 2₈₃₀ fragment was converted to a SCAR marker. The markers identified in this study should be useful tools for the early generation selection of high oleic and low linolenic acid genotypes in oilseed rape breeding programmes.     

Nitrogen balance and losses through drainage waters in an agricultural watershed of the Po Valley (Italy)

Sustainable agriculture requires assessments of nitrogen fluxes and monitoring of potential nitrate losses. Watershed studies are particularly valuable to calculate nitrogen balances and quantify the relative importance of different sources of inputs and outputs. A nitrogen balance was calculated from September 2004 to October 2006 in an agricultural watershed named Valle Volta (Northern Italy) located in a Nitrate Vulnerable Zone. The area, consisting of 17.4 km² of arable land, with limited presence of urban areas and roads, is entirely below the sea level (3 m b.s.l. in average). Soils are typically Vertic Cambisols and Thionic Fulvisols with fine texture (silty clay or silty clay loam). About 45% of the agricultural soil is pipe-drained. The ground water level is maintained at 4.6 m b.s.l. by the activity of pumps that raise excess waters into a river. Water fluxes in and out from the basin were daily registered, and dissolved inorganic nitrogen concentration (N–NO₃ + N–NH₄) analyzed periodically. Data about fertilizers applications, seeds and crop yield were obtained from farmers’ interviews. Biological nitrogen fixation (BNF) was estimated on the base of dry matter yield. Major N inputs derived from fertilizers (174–188 Mg watershed⁻¹ year⁻¹), followed by BNF (126–131 Mg watershed⁻¹ year⁻¹). Maize was the crop receiving the highest fertilization rates, accounting for more than 40% of total fertilizer inputs. Saleable products were the main form of N leaving the watershed (317–338 Mg watershed⁻¹ year⁻¹). Nitrate was the main N form in irrigation and efflux water; its concentration was higher from autumn to spring, with peaks of 10–20 mg N L⁻¹ in efflux water, while it was low in summer. Nitrogen losses with efflux water were higher in spring and in autumn. Overall, losses of nitrate by efflux water were limited if compared with literature data. Water balance in the area remained near zero at the beginning and the end of the first year, confirming the suitability of the area for this kind of study. The potential net contribution of each hectare of agricultural soil of Valle Volta basin to the N load toward the Adriatic sea is about 5.5 kg N. Our study demonstrated that in the Valle Volta watershed, total N outputs and inputs are of similar magnitude, indicating that crop management and especially N fertilization techniques has reached good levels of ecological sustainability.     

Genetic differentiation between summer and autumn maturing cultivars of soybean (Glycine max (L.) Merrill) in Kyushy district of Japan

Summary 135 soybean landraces and pure line selections from Kyushu district fo Japan were assayed for isozyme and seed protein loci in order to determine the genetic structure groups of summer and autumn maturing cultivars. Out of the 16 tested loci, Dial, Enp, Estl, and Ti exhibited a marked difference in allelic frequency between both groups. The summer cultuvar groups had a high frequency for Dial-b, Enp-b, Estl-a and Ti-b, whereas Dial-a, Enp-a, Estl-b, and Ti-a were predominant in the autumn groups. The analysis of multi-locus genotypes revealed that both groups mostly consisted of different multi-locus genotypes. The allelic combination Dial-b Enp-b Estl-a Ti-b was most frequently observed in the summer cultivars, whereas four genootypes, Dial-a Enp-a Estl-a Ti-a, Dial-a Enp-a Estl-b Ti-a, Dial-a Enp-b Estl-b and Dial-a Enp-a Estl-b Ti-b, occupied most of the autumn cultivars. These results indicated that both groups were appreciably differentiated from each other. The summer cultivar groups also included a few accessions having the multi-locus genotypes observed predominantly in the autumn groups or Acol-b charcteristic of the landraces native to northern Japan. It seems likely that the summer cultivar groups was not phyletically derived from a single common ancestor, but partly involves the landraces with early maturity derived from northern Japan. Dial, Enp, Estl and Ti are useful genetic markers ot trace the origin and dissemination paths of Japanse soybean landraces.     

Discovery of a new gene causing dark green cotyledons and pathway of pigment synthesis in lentil (Lens culinaris Medik)

A new gene is reported which functions as a master gene for synthesis of the pigments determining cotyledon colour in lentil. This gene is different from the two earlier reported genes which are responsible for synthesis of yellow (gene Y) and brown (gene B) pigments. Double recessive homozygous condition of these two genes results into loss of both pigments and, consequently, produces light green cotyledons. The new gene, in contrast, produces dark green cotyledons in recessive condition irrespective of the dominance or recessive state of the Y and B genes. It is hypothesized that the new gene for dark green cotyledon colour (Dg) acts at an earlier stage in the biosynthesis of the two cotyledon-specific pigments, which are derived from a common precursor, whose synthesis is blocked when Dg mutates to its recessive condition. This revised version was published online in August 2006 with corrections to the Cover Date.