Interannual variability of PSP outbreaks on the north east UK coast

Paralytic shellfish poisoning (PSP) occurs sporadically on theNB UK coast. The degree of toxicity shows considerable interannualvariability, but particularly severe events occurred in 1968and 1990. The time sequence of PSP toxin production in 1990is described and compared with 1989 when no significant PSPtoxin occurred. In 1990, PSP toxin was widespread in shellfishsamples taken on 300 km of coastline, from Berwick to Whitby,and toxin was present at high concentrations for >1 month.The distribution of Alerandrium tamarense cysts in the sedimentsis described. High concentrations were found in the Firth ofForth and also in a number of regions offshore of the Scottishand English coasts. A water transport model has been used toestimate back trajectories, with the aim of determining thesource of the A.tamarense bloom. The Firth of Forth has previouslybeen suggested as the seed bed for A.tamarense outbreaks inthe area, but the transport model clearly shows that A.tanwrensemoved inshore over a wide area in 1990; there was no singlesource of the bloom. Sea surface temperatures, estimated fromsatellite imagery, show that water temperatures were much higherat the end of April 1990, when the bloom occurred, than in 1989when PSP toxin incidence was very low. These conditions wouldhave resulted in early seasonal stratification and would havefavoured phytoplankton growth in the water column.     

不同pH和盐度下海洋细菌对赤潮藻生长和产毒的影响

研究了在可控生态条件下。一株分离自厦门西海域沉积物的海洋细菌S10在不同pH和盐度条件下对赤潮原因种塔玛亚历山大藻(Alexandrium tamarense)生长和产毒的影响．结果表明。实验用藻株适宜生长pH为6～8,适宜盐度为20～34;该藻株在不同pH及不同盐度条件下,藻细胞毒力差异显著,且随着pH升高而下降。随着盐度增加而加大,到盐度为30时达到最高值。然后逐渐下降;菌株Sl0(1．02×10^l0cells·ml^-1)在pH7～9和盐度15～34下均能有效抑藻生长和产毒。且在pH7、盐度34时其抑藻生长作用最强;在pH7时抑藻产毒效果较好,且其抑藻产毒作用强度不随盐度变化而异．     

Observations on Alexandrium tamarense (Lebour) Balech and Other Dinoflagellate Populations in Golfo Nuevo, Patagonia (Argentina)

The toxic dinoflagellate Alexandrium tamarense and other dinoflagellatespecies were studied, along with water temperature and nutrientconcentrations, from September 1995 to December 1998 in theGolfo Nuevo, Chubut, Argentina. Nutrient concentrations werelow, showing a peak of high concentration in winter and a phaseof depletion in late spring and summer. Dinoflagellates tendedto be abundant during spring and summer, when Prorocentrum micanswas the most important species. Other dinoflagellates were Pyrophacushorologium and Dinophysis acuminata. Ceratium tripos, C. fususand C. horridum were present during the autumn, and a C. tripospeak up to 5.9 x 10³ cell l^–1 was observed in May 1997.Alexandrium tamarense showed strong interannual variation, thehighest concentration being found in spring (September–October)1995, with densities up to 15 x 10³ cells l^–1. The secondA.tamarense peak was observed during October–November1998 with maximal densities up to 5 x 10³ cells l^–1. Moderatelyhigh A. tamarense cyst densities, up to 300 cysts cm^–3of sediment, were found in the deep zone of the Golfo Nuevobasin. Among meteorolog-ical variables, increased late winterrain and higher solar radiation during spring may have influencedA. tamarense blooms.     

Timing of photoperiodic competency causes phenological mismatch in balsam poplar (Populus balsamifera L.)

Plant phenology is expected to be sensitive to climate warming. In boreal trees, spring flush is primarily temperature driven, whereas height growth cessation and autumn leaf senescence are predominantly controlled by photoperiod. Cuttings of 525 genotypes from the full range of balsam poplar were planted into two common gardens (Vancouver and Indian Head, Canada) at similar latitudes, but with differing winter temperatures and growing seasons. There was clinal variation in spring and, particularly, summer and fall phenology. Bud flush and, despite milder climate, bud set and leaf drop were earlier at Vancouver than at Indian Head by 44, 28 and 7 d, respectively. Although newly flushed growth is insensitive to photoperiod, many genotypes at both sites became competent before the summer solstice. At Vancouver, high‐latitude genotypes set dormant terminal buds in mid‐spring. Most other genotypes grew until midsummer or set bud temporarily and then experienced a second flush. In both gardens and in a growth chamber experiment, earlier bud set was associated with reduced height growth and higher root/shoot ratios. Shoots attained competency ～5 weeks after flushing, which would normally prevent dormancy induction before the solstice, but may be insufficient if spring advances by more than a few weeks.     

Paralytic shellfish poisoning toxins in France linked to a human-introduced strain of Alexandrium catenella from the western Pacific: evidence from DNAand toxin analysis

In 1998, the toxins responsible for paralytic shellfish poisoning(PSP) were detected in Thau Lagoon, France. The causative organismwas identified as Alexandrium tamarense, a member of the ‘tamarensis’species complex. This dinoflagellate was first observed in thelagoon in 1995 by a monitoring programme following more thana decade with no observations of this species. The species isthus new to these waters, but its origins were unknown. In thispaper, morphological and molecular data are analysed for twoclonal cultures established from the 1998 bloom. These dataare compared to results from Alexandrium isolates originatingelsewhere in the world to infer an origin. Thecal plate morphology,restriction fragment length polymorphism, DNA sequencing andtoxin analyses demonstrate that the Thau Lagoon strains areA. catenella, and are closely related to populations of A. catenellafound in temperate Asia, specifically the Japanese TemperateAsian ribotype of the tamarense/catenella/fundyense speciescomplex. They show no homology with strains from western Europeanwaters, including the Mediterranean. Until now, the JapaneseTemperate Asian ribotype has not been reported outside the westernPacific. The most likely scenario is that A. catenella was introducedto Thau Lagoon via the ballast water of a ship docked at Sète,France, a shipping port in direct communication with the lagoon.This case provides a clear example of the dispersal of a toxicAlexandrium species, probably via human activities.     

Does the western Irish Sea gyre influence the distribution of pelagic juvenile fish?

The western Irish Sea is an important spawning and nursery ground for many commercially exploited fish. Spawning begins in the Irish coastal regions in early spring, and moves offshore as the season develops. As a result of the onset of seasonal heating in spring, stratification isolates a dome of cold bottom winter water in the deep (>100 m) basin of the western Irish Sea. The resultant density fields drive a cyclonic gyre which dominates the circulation of the region during late spring and summer and is characterized by anticlockwise current speeds which exceed 0.2 ms^–1, after removal of tides. Surveys of pelagic juvenile (0-group) fish in 1994, 1995 and 1996, showed that they were coincident with the centre of the gyre. Physical data from 1994 and 1995, were used to describe the horizontal and vertical structure of the water column and the associated circulation regime. The behaviour and swimming speeds of pelagic juvenile fish were insufficient to explain their apparent shift in abundance away from the coast to the central western Irish Sea. Drifter and current data suggested that their entrainment into the gyre could provide both the transport and retention mechanisms.     

Some differences in the parasitic fauna of three samples of plaice (Pleuronectesplatessa L.) from the southern North Sea

Plaice ( Pleuronectesplatessa L.) from three spawning areas in the southern North Sea were examined for six species of metazoan parasite. Differences of both incidence and level of infestation with particular parasite species were found in fish from the three areas. Neither the incidence nor the level of infestation was associated with the length of fish in the samples except in the case of the larger male fish from Flamborough, which tended to contain more larval nematodes (Anisakidae). All fish contained the intestinal nematode Cucullanus heterochrous , although fewer were found in fish from Flamborough. Southern Bight fish were more likely to contain Capillaria wickinsi than were fish from Flamborough or the German Bight. Flamborough fish were more likely to contain Anisakidae larvae than were fish from the other two areas. Fish from the three areas were similarly infested with Zoogonoides viviparus. Male fish from Flamborough were less likely to be infested with Lepeophtheirus pectoralis than male fish from the German Bight.     

The late Cenomanian event in eastern England

The Cenomanian/Turonian boundary event has been fully documented from a series of localities between Flamborough Head in Humberside and Marham in Norfolk. The carbon isotope excursion can be identified and extrapolated to all the studied sections using bed‐by‐bed correlation. Evidence from studies of the isotope data, trace element geochemistry, and the micropalaeontology are presented. The famous “Black Band” is seen to change laterally into a “red” horizon and then a “green” horizon when traced southwards. This appears to represent the “feather‐edge” of the anoxic event when traced towards a palaeo‐high which is located in the region of the Wash. All the events, so‐identified, can be correlated with the A. plenus Marl succession in southern England.     

三峡三期蓄水后长江口海域浮游动物群落特征及影响因子

根据2010年8月、11月以及2011年5月3个航次、各次24个监测点的调查数据,分析了三峡工程三期蓄水后一个水文年内长江口浮游动物优势种、湿重生物量及丰度的变化,并用BIOENV筛选出影响浮游动物分布的关键环境因子。结果表明:长江口浮游动物春季绝对优势种为夜光虫(Noctiluca scientillans)与中华哲水蚤(Calanus sinicus),夏季绝对优势种为太平洋纺锤水蚤(Acartia pacifica steuer),秋季绝对优势种为针刺拟哲水蚤(Paracalanus aculeatus);浮游动物湿重生物量夏季(970.6 mg/m~3)秋季(613.8 mg/m~3)春季(571.5 mg/m~3),丰度夏季(783.5个/m~3)春季(691.3个/m~3)秋季(399.5个/m~3);影响浮游动物分布的关键环境因子为底层盐度、底层温度及底层硅酸盐。     

Life history and population biology of adult Acanthocephalus lucii (Acanthocephala: Echinorhynchidae)

The life history and population biology of adult A. lucii in perch, Perca fluviatilis L., from the Forth and Clyde canal, Scotland, was investigated during May 1979-September 1981. There was an annual cycle in the size of the parasite population; prevalence and abundance (+/- SE) were highest during late spring and summer (70-90% and 14 +/- 4.3 to 16 +/- 5.6 worms/fish, respectively) but declined during late autumn and reached a minimum during winter (50-60% and 2.1 +/- 0.9 to 3.2 +/- 0.6 worms/fish). Parasite maturation was associated with higher water temperatures during spring and summer and most shelled acanthors were probably produced during summer and fall. There was only 1 generation of A. lucii per year, although generations tended to overlap and individuals within each generation did not develop synchronously. The sex ratio of adults was initially near unity but favoured females in the later stages of the infection. The distribution of A. lucii among perch was highly aggregated and stomach content analysis suggested that this was partly due to heterogeneity in perch feeding behaviour. The negative binomial and Poisson lognormal models fitted the data on worm distribution. Seasonal changes in the degree of parasite aggregation were detected, but no conclusive evidence of density-dependent controls on parasite population growth was obtained.     

Temporal analysis of archived samples indicates marked genetic changes in declining North Sea cod (Gadus morhua)

Despite increasing evidence that current exploitation rates can contribute to shifts in life-history traits and the collapse of marine fish stocks, few empirical studies have investigated the likely evolutionary impacts. Here, we used DNA recovered from a temporal series of archived North Sea cod (Gadus morhua) otoliths, to investigate genetic diversity within the Flamborough Head population between 1954 and 1998, during which time the population underwent two successive declines. Microsatellite data indicated a significant reduction in genetic diversity between 1954 and 1970 (total number of alleles: 1954, 46; 1960, 42; 1970, 37), and a subsequent recovery between 1970 and 1998 (total number of alleles: 1970, 37; 1981, 42; 1998, 45). Furthermore, estimates of genetic differentiation (F(ST) and R(ST)) showed a significant divergence between 1998 and earlier samples. Data are consistent with a period of prolonged genetic drift, accompanied by a replacement of the Flamborough Head population through an increased effective migration rate that occurred during a period of high exploitation and appreciable demographic and phenotypic change. Other studies indicate that diversity at neutral microsatellite loci may be correlated with variability at selected genes, thus compromising a population's subsequent recovery and adaptive potential. Such effects are especially pertinent to North Sea cod, which are threatened by continuing exploitation and rising sea temperatures.     

Comparison of contemporary and fossil diatom assemblages from the western Antarctic Peninsula shelf

During the past ten years, the Antarctic Peninsula has been identified as the most rapidly warming region of the Southern Hemisphere and it is important to place this warming in the context of the natural climate and oceanographic variability of the recent geological past. Many biological proxies, such as marine diatom assemblages, have been used to determine Southern Ocean palaeoceanographic conditions during the Late Quaternary, however, few investigations have attempted to link observations of modern floras with the fossil record. In this study we examine a suite of modern austral spring (December 2003) and summer (February 2002) surface water samples from along the western Antarctic Peninsula (WAP) continental shelf and compare these to core-top, surface sediment samples. Using detrended correspondence analysis (DCA) and principal component analysis (PCA) of diatom abundance data we investigate the relationship of contemporary diatom floras with the fossil record. This multivariate analysis reveals that our modern assemblages can be divided into three groups: summer southern WAP sites, summer northern WAP sites, and spring WAP sites. Sea surface temperature (SST) is an important environmental variable for explaining seasonal differences in diatom assemblages between spring and summer, but sea surface salinity (SSS) is more important for understanding temporally-equivalent regional variations in assemblage. Our summer diatom samples are more reminiscent of early season assemblages, reflecting the unusually late sea ice retreat from the region that year. When the modern assemblages are compared to the fossil record, it is clear that most of the important diatoms from the summer assemblage are not preserved into the sediments, and that the fossil record more closely reflects spring assemblages. This observation is important for any future attempts to quantitatively reconstruct palaeoceanographic conditions along the WAP during the Late Quaternary and highlights the need for many more such studies in order to address longer timescales, such as interannual variability, in the context of the fossil record.     

Paralytic shellfish poisoning (PSP) in Margarita Island, Venezuela

A severe outbreak of Paralytic Shellfish Poisoning (PSP) occurred in Manzanillo and Guayacán, northwestern coast of Margarita Island, Venezuela, between August and October 1991. A bloom of dinoflagellates including Prorocentrum gracile, Gymnodinium catenatum and Alexandrium tamarense seemed to be responsible for this outbreak. Levels of PSP toxins in mussels (Perna perna) exceeded the international safety limit of saxitoxin, 80 microg STX/100 microg meat. PSP toxin values varied between 2548 and 115 microg STX/100 g meat in Manzanillo, and between 1422 and 86 microg STX/100 g meat in Guayacán. At both locations, the highest levels were detected in August, when 24 patients exhibited typical symptoms of PSP toxicity after consuming cooked mussels (16 required hospitalization). A high pressure liquid chromatographic (HPLC) procedure was recently used on the 1991 samples. The major toxin detected in samples of both locations was decarbamoyl saxitoxin (dcSTX), but low concentrations of saxitoxin were also found in Manzanillo samples. Gonyautoxins GTX1, GTX2 and GTX3 were detected only at Guayacán, while in both locations, decarbamoylgonyatouxin (dcGTX2,3) toxins were detected. These findings represent the first time that causative toxins of PSP in Venezuela have been chemically identified, and confirm the presence of dcSTX and dcGTX in mussels from the Caribbean Sea. The presence of dcSTX and dcGTX in shellfish is indicative that Gymnodinium catenatum was a causative organism for outbreak of PSP.     

IDENTIFICATION OF GROUP- AND STRAIN-SPECIFIC GENETIC MARKERS FOR GLOBALLY DISTRIBUTED ALEXANDRIUM (DINOPHYCEAE). II. SEQUENCE ANALYSIS OF A FRAGMENT OF THE LSU rRNA GENE1

A fragment of the large-subunit (LSU) ribosomal RNA gene (rDNA) from the marine dinoflagellates Alexandrium tamarense (Lebour) Balech, A. catenella (Whedon et Kofoid) Balech, A. fundyense Balech, A. affine (Fukuyo et Inoue) Balech, A. minutum Halim, A. lusitanicum Balech, and A. andersoni Balech was cloned and sequenced to assess inter- and intraspecific relationships. Cultures examined were from North America, western Europe, Thailand, Japan, Australia, and the ballast water of several cargo vessels and included both toxic and nontoxic isolates. Parsimony analyses revealed eight major classes of sequences, or “ribotypes,” indicative of both species- and strain-specific genetic markers. Five ribotypes subdivided members of the A. tamarense/catenella/ fundyense species cluster (the “tamarensis complex”) but did not correlate with morphospecies designations. The three remaining ribotypes were associated with cultures that clearly differ morphologically from the tamarensis complex. These distinct sequences were typified by 1) A. affine, 2) A. minutum and A. lusitanicum, and 3) A. andersoni. LSU rDNA from A. minutum and A. lusitanicum was indistinguishable. An isolate's ability to produce toxin, or lack thereof, was consistent within phylogenetic terminal taxa. Results of this study are in complete agreement with conclusions from previous work using restriction fragment-length polymorphism analysis of small subunit rRNA genes, but the LSU rDNA sequences provided finer-scale species and population resolution. The five divergent lineages of the tamarensis complex appeared indicative of regional populations; representatives collected from the same geographic region were the most similar, regardless ofmorphotype, whereas those from geographically separated populations were more divergent even when the same morphospecies were compared. Contrary to this general pattern, A. tamarense and A. catenella from Japan were exceptionally heterogeneous, displaying sequences associated with Australian, North American, and western European isolates. This diversity may stem from introductions of A., tamarense to Japan from genetically divergent sources in North America and western Europe. Alexandrium catenella from Japan and Australia appeared identical, suggesting that these two regional populations share a recent, common ancestry. One explanation for this genetic continuity was suggested by A. catenella cysts transported from Japan to Australia via ships' ballast water: the cysts contained LSU rDNA sequences that were indistinguishable from those of known populations of A. catenella in both Japan and Australia. Ships ballasted in South Korea and Japan have also fostered a dispersal of viable A. tamarense cysts to Australia, but their LSU rDNA sequences indicated they are genetically distinct from A. tamarense/catenella previously found in Australia and genetically distinct from each other, as well. Human-assisted dispersal is a plausible mechanism for inoculating a region with diverse representatives of the tamarensis complex from geographically and genetically distinct source populations. The D1-D2 region of Alexandrium LSU rDNA is a valuable taxo-nomic and biogeographic marker and a useful genetic reference for addressing dispersal hypotheses.     

Gonadal cycles and the evolution of breeding seasons in British Columbidae

The gonads of Wood-pigeons in a Cambridgeshire study area attain peak reproductive condition in July and this condition persists until late September or early October when rapid regression takes place. Gametogenesis recommences in early March. In the same area the Stock-dove has a similar cycle but gametogenesis begins about two months earlier and regression apparentlytakes place about one month later. A wild Rock-dove population at Flamborough Head, Yorkshire has an even longer physiological breeding season, gametogenesis commencing from December. Seasonal regression occurs in October.     

Effects of toxic Alexandrium species on the survival and feeding rates of brine shrimp, Artemia salina

Zooplankton is an important link between phytoplankton and higher consumers in the marine food chain. To investigate the harmful effects of the toxic dinoflagellate Alexandrium species on zooplankton, 4 strains of Alexandrium spp., isolated from the Chinese coast, were used to test the species' effects on the survival and feeding rates of the brine shrimp, Artemia salina. The experiment was designed to assess the response of A. salina in each stage of its life cycle: nauplii, metanauplii, and adult. Each experiment was conducted in a 500 ml treatment that was added. The toxic treatments consisted of single strains of A. minutum, A. catanella, and A. tamarense (Nanhai and Donghai strain), while non-toxic species (dinoflagellate Prorocentrum donghaiense and diatom Chaetoceros minutissimus) were used as control treatments. An additional phytoplankton treatment consisted of, a mixture of A. tamarense (Nanhai strain) and P. donghaiense. Alexandrium spp. species were found to have lethal effects on the brine shrimp at a density of 2000 cells/ml. All the brine shrimps died within 24-168 hours of inoculation with the 4 treatments each containing single toxic Alexandrium species. During the feeding experiment, toxic Alexandrium spp. caused a reduction in the feeding rates in all the three stages of the life cycle of A. salina, whereas this response was not obvious in the treatment involving the nontoxic species P. donghaiense. The body surface of the brine shrimp that were fed on Alexandrium species was consistently covered by a sticky floc. Mortality of A. salina was observed to increase with the occurrence of the floc. The toxicity of the paralytic shellfish poisons (PSP) produced by the Alexandrium species was not significantly correlated with the survival or the feeding rate of the brine shrimp. When A. tamarense was mixed with P. donghaiense, the lethal effect of A. tamarense decreased, as shown by an increase in the survival and the feeding rates of the brine shrimp. A. salina metanauplii were found at the life stage most sensitive to the toxic algae and hunger. In summary, toxic Alexandrium spp. were found to have lethal effects on A. salina and to restrain the brine shrimp's feeding rate. Nontoxic Prorocentrum mitigated the toxicity of Alexandrium to a certain extent. The results also imply that the sticky material on the surface of the body of the brine shrimp may have been an important lethal factor rather than the PSP toxins.     

浙江沿岸产卵场春、夏季鱼类资源密度和群落多样性研究

根据2015年4月(春季)和7月(夏季)在浙江沿岸产卵场进行的渔业资源底拖网调查资料, 采用多重比较(LSD)和分类回归树(CART)方法研究了浙江沿岸产卵场春、夏季群落多样性和鱼类资源的变化, 以及多样性与诸多环境因子(生物和非生物)的关系, 结果表明: (1)该水域春季共捕获鱼类92种, 隶属17目50科77属, 夏季捕获鱼类114种, 隶属16目59科92属; (2)春季全区生物量平均为434.40 kg/km2, 中部和南部生物量差异极显著(P=0.005), 全区尾数密度平均为58.42千尾/km2, 不同区域差异不显著; 夏季全区生物量平均为1532.73 kg/km2, 北部生物量与中部差异极显著(P=0.000), 与南部差异显著(P=0.017), 全区尾数密度平均为205.50千尾/km2, 北部尾数密度与南部差异显著(P=0.034), 其他区域间差异不显著; (3)春季H′平均值为1.52, D平均值为2.18, 北部和南部D差异显著(P=0.048), 其他区域间H′和D差异均不显著; 夏季H′平均值为1.34, D平均值为1.81, 中部和北部H′差异极显著(P=0.000), 和南部差异接近极显著(P=0.01), 北部和中部D差异显著(P=0.039), 其他区域间差异不显著; (4)CART分析表明, 影响春季多样性和丰富度的主要因素有水深、浊度和溶氧; 秋季多样性水平主要受的水深、桡足类、温度和浊度的影响; (5)从空间和时间上与其他水域的多样性水平相比较得出, 在空间上, 纬度与H′并不存在简单的线性关系, 但当纬度跨度比较大时, 低纬度水域的H′值明显高于高纬度水域的H′值; 在时间上, 多样性水平较2008年明显升高, 但与2011年的调查结果相近, 表明产卵场(南部)近几年渔业生态环境处于相对较稳定的状态。     

Effects of toxic Alexandrium species on the survival and feeding rates of brine shrimp, Artemia salina

Zooplankton is an important link between phytoplankton and higher consumers in the marine food chain. To investigate the harmful effects of the toxic dinoflagellate Alexandrium species on zooplankton, 4 strains of Alexandrium spp., isolated from the Chinese coast, were used to test the species' effects on the survival and feeding rates of the brine shrimp, Artemia salina. The experiment was designed to assess the response of A. salina in each stage of its life cycle: nauplii, metanauplii, and adult. Each experiment was conducted in a 500 ml treatment that was added. The toxic treatments consisted of single strains of A. minutum, A. catanella, and A. tamarense (Nanhai and Donghai strain), while non-toxic species (dinoflagellate Prorocentrum donghaiense and diatom Chaetoceros minutissimus) were used as control treatments. An additional phytoplankton treatment consisted of, a mixture of A. tamarense (Nanhai strain) and P. donghaiense. Alexandrium spp. species were found to have lethal effects on the brine shrimp at a density of 2000 cells/ml. All the brine shrimps died within 24-168 hours of inoculation with the 4 treatments each containing single toxic Alexandrium species. During the feeding experiment, toxic Alexandrium spp. caused a reduction in the feeding rates in all the three stages of the life cycle of A. salina, whereas this response was not obvious in the treatment involving the nontoxic species P. donghaiense. The body surface of the brine shrimp that were fed on Alexandrium species was consistently covered by a sticky floc. Mortality of A. salina was observed to increase with the occurrence of the floc. The toxicity of the paralytic shellfish poisons (PSP) produced by the Alexandrium species was not significantly correlated with the survival or the feeding rate of the brine shrimp. When A. tamarense was mixed with P. donghaiense, the lethal effect of A. tamarense decreased, as shown by an increase in the survival and the feeding rates of the brine shrimp. A. salina metanauplii were found at the life stage most sensitive to the toxic algae and hunger. In summary, toxic Alexandrium spp. were found to have lethal effects on A. salina and to restrain the brine shrimp's feeding rate. Nontoxic Prorocentrum mitigated the toxicity of Alexandrium to a certain extent. The results also imply that the sticky material on the surface of the body of the brine shrimp may have been an important lethal factor rather than the PSP toxins.     

巢湖流域地下水硝态氮含量空间分布和季节变化格局

2009年冬季、2010年春季和夏季分别在巢湖流域采集了253个、249个和230个水井的地下水样品,分析了其硝态氮含量。结果表明,巢湖流域的地下水硝酸盐污染比较严重,冬季、春季和夏季的地下水硝态氮的超标率(≥10 mg/L)均超过20%。巢湖北部区的地下水硝态氮含量高于南部地区。在巢湖北部区,东北部江淮分水岭丘陵区的地下水硝态氮含量较低。在巢湖南部区,地下水硝态氮含量具有从西部山区向东部平原逐渐升高的趋势。不同土地利用类型的地下水硝态氮含量排序是村庄菜地旱地乡镇水稻-油菜(或小麦)轮作田果园单季水稻田养殖场,传统水稻田绿色水稻田。巢湖流域地下水硝态氮含量的季节变化总趋势为冬季≈春季夏季,主要与降水有关。不同土地利用类型的地下水硝态氮含量的季节变化格局不同,其中地下水硝态氮含量呈现冬季春季夏季的土地类型为菜地、果园和水稻田,春季冬季夏季的土地类型为旱地、乡镇、畜禽养殖场,春季夏季冬季的土地类型为村庄,这种季节变化格局主要与不同土地利用类型的施肥量、施肥时间的不同有关。     

莱州湾及黄河口水域鱼类群落结构的季节变化

根据2011年5月—2012年4月对莱州湾及黄河口水域9个航次的渔业底拖网调查数据,对该水域鱼类群落结构特征及其季节变化进行了初步研究。结果表明:莱州湾及黄河口水域共捕获鱼类62种,隶属于11目、34科、53属,主要由暖水种和暖温种组成,其中鲈形目种类最多(37种),其次是鲉形目(7种)和鲽形目(6种)。春季优势种包括矛尾鰕虎鱼(Chaeturichthys stigmatias)、鲱衔(Callionymus beniteguri)、短吻红舌鳎(Cynoglossus joyneri)、矛尾复鰕虎鱼(Synechogobius hasta)和方氏云鳚(Enedrias fangi),其渔获量占总渔获量的70.8%;夏季包括矛尾鰕虎鱼、斑鰶(Konosirus punctatus)、鲱衔和短吻红舌鳎,占总渔获量的68.1%;秋季包括矛尾鰕虎鱼、赤鼻棱鳀(Thrissa kammalensis)、鳀(Engraulis japonicus)、青鳞小沙丁鱼(Sardinella zunasi)、斑鰶、小黄鱼(Larimichthys polyactis)和矛尾复鰕虎鱼,占总渔获量的87.1%。平均单位时间渔获量存在显著季节变化,以秋季最高(22.63kg/h),其次是夏季(16.75kg/h),春季最低(1.29kg/h)。春季(5月)平均单位时间渔获量为0.69kg/h,为1959年、2003年、2006年和2008年春季(5月)的0.3%、0.3%、1.7%和541.2%,鱼类资源量虽有所回升,但总体呈大幅下降的趋势。鱼类种类数、丰富度指数和多样性指数夏季较高,秋季次之,春季最低,但是以渔获尾数计算的均匀度指数,夏季最大,春季最小,以渔获量计算的均匀度指数则相反,且丰富度指数和多样性指数与表层温度呈极显著相关(P0.01),丰富度指数和均匀度指数与表层盐度呈极显著相关(P0.01)。