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1.
The colony-forming Phaeocystis species are causative agents of dense bloom occurrences in coastal waters worldwide. It is difficult to separate them because of the different morphologies associated with their colonial stages. In this study we applied molecular approaches to analyze the genetic variation of Phaeocystis globosa and Phaeocystis pouchetii from several geographic regions, and to assist in tracing the dispersal of bloom-forming Phaeocystis species in coastal waters of China. The sequences of the internal transcribed spacers (ITS1 and ITS2) of rDNA and the 5.8S ribosomal RNA gene of Phaeocystis strains were determined. Sequence comparison shows that P.globosa was the most divergent to P. pouchetii, exhibiting sequence divergence higher than 0.08. However, lower genetic divergences existed between strains of P.globosa. The sequence comparison of the Phaeocystis rDNA ITS clearly shows that the species isolated from the southeast coast of China is identified as P.globosa rather than P. cf. pouchetii or other species. Furthermore, the significance of rDNA variation in distinct global populations of P.globosa suggested it might have had sufficient time to accumulate detectable mutations at the rDNA locus, supporting the hypothesis of ancient dispersal of P.globosa to many areas, meaning that P.globosa blooms in the coastal waters of China are endemic rather than a newly introduced species or a foreign source. Finally, based on the high divergent region of rDNA ITS, a pair of species-specific primers for P.globosa were designed, they could be useful to detect the presence of this species in mixed plankton assemblages or flagellate stages that are recognized with diffculties by means of conventional microscopy.  相似文献   

2.
There were two severe coral bleaching events at Ko Khang Khao, the inner Gulf of Thailand, occurred during the prolonged period of the elevated sea surface temperature (SST) in 2010 and low salinity as well as turbidity due to heavy flooding in 2011. The bleaching index (BI) and mortality index (MI) are calculated to compare the susceptibilities of coral species in the two bleaching events. The BI and MI vary significantly among the study sites and bleaching events. The most susceptible corals during both bleaching events are Acropora millepora, Pocillopora damicornis and Pavona decussate, while the most resistant species were Galaxea fascicularis, Fungia fungites, Pavona frondifera, Oulastrea crispate, and Symphyllia recta. The corals Favia favus, Goniopora columna, Platygyra pini, Symphyllia agaricia were relatively more tolerant to high SST but they are relatively more susceptible to low salinity. Coral bleaching is a phenomenon that the dissociation stress of the symbiotic relationship between zooxanthellae and their cnidarian host results in the reduction in photosynthetic pigment concentration. Among stressors, both prolonged exposure of high SST and low salinity, above and below their thresholds, respectively. The long-term resilience of coral communities at Ko Khang Khao and other coral communities close to the mouth of large rivers may depend on the frequency and duration of the exposure on the elevated SST due to atmospheric heating and low salinity due to river flooding.  相似文献   

3.
Short-term tidal and diel variations of autumn fish assemblage in a Zostera marina bed were investigated using 3 h interval samplings for 24 h in both spring and neap tide using a small beam trawl. A total of 1 346 fishes belonging to 19 species were collected at spring tide, whereas 1 115 fishes belonging to 17 species were at neap tide. The common fish species were Nuchequula nuchalis, Acanthogobius flavimanus, Takifugu niphobles, Acentrogobius pflaumii, and Pholis nebulosa with the former three species dominating at spring tide, while the latter two species being abundant at neap tide. Diel variation in abundance was significant with higher abundance at night than day, but there were no significant differences between spring and neap tides, and between ebb and flood tides (three-way ANOVAs). Diel variation in the abundance of fishes may be influenced by tidal range and cycle, and day-night differences of food availability and behaviors of fishes indirectly. Non-metric multidimensional scaling (nMDS) ordination and analysis of similarity (ANOSIM) results revealed significant differences in species compositions both between day and night, and between spring and neap tide. Eelgrass beds are highly productive marine ecosystem, and thus, our results will contribute to conservation of seagrass ecosystem in the study area.  相似文献   

4.
Mangrove ecosystems are sites with high biodiversity of benthic fauna, and fiddler crabs (genus Uca) are common benthic fauna in mangroves. The North Sulawesi in Indonesia has a good condition of mangrove while the information of the fiddler crabs is still limited. Manual samplings were conducted in wet, dry and transient seasons at a mangrove in Kema, North Sulawesi to investigate the species composition, density and distribution pattern of fiddler crabs. A total of 168 individuals, subjected to eight species of genus Uca crabs were collected at the mangrove, with U. triangularis having the highest abundance and U. annulipes having the lowest abundance. The densities of fiddle crabs were 27.56 ind./m2, 32.89 ind./m2 and 14.22 ind./m2 at the seaward, middle and landward zones, respectively, and the density was higher in dry and wet seasons than in transient season.  相似文献   

5.
In the present study, we have investigated the conditions influencing encystment and excystment in the dinoflagellate Gyrodinium instriatum under laboratory conditions. We incubated G. instriatum in modified whole SWM-3 culture medium and in versions of modified SWM-3 from which NO3 −, PO4 3−, NO3 − + PO4 3−, or Si had been omitted and observed encystment. Percentage encystment was high in the media without N and without P, while the percentage encystment in the medium lacking both N and P was highest. Moreover, to investigate N or P concentration which induced the encystment, Gyrodinium instriatum was also incubated in media with different concentrations of inorganic N and P; the concentrations of NO2 − + NO3 − and PO4 3− were measured over time. The precursors of cysts appeared within 2 or 3 days of a decrease in NO2 − + NO3 − or PO4 3− concentration to values lower than 1 μM or 0.2 μM, respectively. When cysts produced in the laboratory were incubated, we observed excystment after 8–37 days, without a mandatory period of darkness or low temperature. We incubated cysts collected from nature at different temperatures or in the dark or light and observed excystments. Natural cysts excysted at temperatures from 10 to 30°C, in both light and dark, but excystment was delayed at low temperatures. These studies indicate that G. instriatum encysts in low N or P concentration and excysts over a wide temperature range, regardless of light conditions, after short dormancy periods.  相似文献   

6.
Our laboratory study concerns the competitive interaction between two marine rotifer species Brachionus plicatilis and Brachionus rotundiformis at five algal (Nannochloropsis salina) concentrations (0.4×106 to 32.4×106 cells/ml) and at four initial inoculation densities (numerically, 100% B. plicatilis; 75% B. plicatilis and 25% B. rotundiformis, 50% each of the two species; 25% B. plicatilis and 75% B. rotundiformis and 100% B. rotundiformis. The initial biomass varied as 0.33 and 0.22 μg/ml for B. plicatilis and B. rotundiformis respectively. Experiments were performed at (25±1)℃. Population densities were enumerated and the medium was changed daily up to 8 d in the experiment. At the lowest food level tested, B. rotundiformis formed superior competitor than B. plicatilis, regardless of starting inoculation density. Generally when the food concentrations increased, B. plicatilis showed a greater increase in biomass than B. rotundiformis. B. rotundiformis formed the largest in population growth, regardless of increasing food concentrations. When grown alone, B. plicatilis reached peak abundances of (1.311 5±0.028) and (137.5±0.014) μg/ml at low and high food densities respectively. The corresponding values of B. rotundiformis were 0.724 5±0.016 and 18.15±0.021. The adverse effects of B. rotundiformis on the peak abundances of B. plicatilis were observed at the lowest food level and higher initial density. The rate of population growth in controls varied from (0.792±0.162) to (1.482±0.132) μm/d for B. plicatilis and (0.445±0.041) to (0.856±0.012) μm/d for B. rotundiformis, depending on food level. When both species were introduced together, low food levels favoured higher abundance of B. rotundiformis than B. plicatilis, suggesting that increased population density of the smaller B. rotundiformis was more successfull than larger B. plicatilis in brackish waters. Our work reveals that available food (type and quantity) along with starting inoculation density had significant effect on the interspecific competition between marine sibling rotifer species in zooplankton community structure.  相似文献   

7.
Microalgae are photosynthetic microorganisms that function as primary producers in aquatic ecosystems. Some species of microalgae undergo rapid growth and cause harmful blooms in marine ecosystems. Heterocapsa triquetra is one of the most common bloom-forming species in estuarine and coastal waters worldwide. Although this species does not produce toxins, unlike some other Heterocapsa species, the high density of its blooms can cause significant ecological damage. We developed a H. triquetra species-specific nuclease protection assay sandwich hybridization (NPA-SH) probe that targets the large subunit of ribosomal RNA (LSU rRNA). We tested probe specificity and sensitivity with five other dinoflagellates that also cause red tides. Our assay detected H. triquetra at a concentration of 1.5×104 cells/mL, more sensitive than required for a red-tide guidance warning by the Korea Ministry of Oceans and Fisheries in 2015 (3.0×104 cells/mL). We also used the NPA-SH assay to monitor H. triquetra in the Tongyeong region of the southern sea area of Korea during 2014. This method could detect H. triquetra cells within 3 h. Our assay is useful for monitoring H. triquetra under field conditions.  相似文献   

8.
The late Quaternary paleoceanographic changes in the western Arctic Ocean are revealed by quantitative studies of foraminiferal abundance, ice-rafted detritus (IRD) and its mineralogical and petrological compositions, planktonic Neogloboquadrina pachyderma (sin.) (Nps)-δ18O and -δ13C, biogenic and non-biogenic components in Core M03 token from the Chukchi Basin during the Second Chinese National Arctic Expedition cruise. Seven IRD events appeared at MIS 7, 5, 3 and 1. These IRD were carried in massive icebergs, which were exported to the Beaufort Sea through the M'Clure Strait Ice Stream, Canadian Arctic Archipelago, and then transported into the Chukchi Basin by the Beaufort Gyre. Low IRD deposition occurred during the glacial times when more extended ice cover and weakened Beaufort Gyre, while the open water condition and the intensified Beaufort Gyre during interglacial periods favored the IRD deposition. Therefore, the IRD events not only indicate the provenance of coarser detritus and ice export events, but also reflect the evolutionary histories of the Beaufort Gyre and North American ice sheet. Seven light Nps-δ18O and -δ13C excursions could respond to enhanced rates of sea ice formation resulting in the production and sinking of isotopically light brines, but was irrelevant to the warm Atlantic water and freshwater inputs. Whereas, the heavy Nps-δ18O and -δ13C values separately reflect the lessened Arctic freshwater and Pacific water, and well-ventilated surface water from the continental shelf and halocline water. Variations of CaCO3 content and planktonic foraminiferal abundance during the interglacial and glacial periods can demonstrate the incremental or diminishing input of the Atlantic water, while the total organic carbon (TOC) and opal contents increased and decreased during the glacial and interglacial periods, respectively, which could be related to the TOC degradation, opal dissolution and redox conditions of interface between the bottom water and sediments.  相似文献   

9.
The seasonal abundance of the dominant dinoflagellate, Ceratium fusus, was investigated from January 2000 to December 2003 in a coastal region of Sagami Bay, Japan. The growth of this species was also examined under laboratory conditions. In Sagami Bay, C. fusus increased significantly from April to September, and decreased from November to February, though it was found at all times through out the observation period. C. fusus increased markedly in September 2001 and August 2003 after heavy rainfalls that produced pycnoclines. Rapid growth was observed over a salinity range of 24 to 30, with the highest specific rate of 0.59 d−1 measured under the following conditions: salinity 27, temperature 24°C, photon irradiance 600 μmol m−2s−1. The growth rate of C. fusus increased with increasing irradiance from 58 to 216 μmol m−2s−1, plateauing between 216 and 796 μmol m−2s−1 under all temperature and salinity treatments (except at a temperature of 12°C). Both field and laboratory experiments indicated that C. fusus has the ability to grow under wide ranges of water temperatures (14–28°C), salinities (20–34), and photon irradiance (50–800 μmol m−2s−1); it is also able to grow at low nutrient concentrations. This physiological flexibility ensures that populations persist when bloom conditions come to an end.  相似文献   

10.
In Tokyo Bay the concentrations of dissolved gaseous mercury (DGM) in the surface seawater and total gaseous mercury (TGM) over the sea were measured during December 2003, October 2004 and January 2005. Based on these data, the evasional fluxes of mercury from the sea surface were estimated using a gas exchange model. In addition, an automatic wet and dry deposition sampler was used to measure the wet and dry depositional fluxes of mercury from December 2003 to November 2004 at three locations in and near Tokyo Bay. The results indicate that the average DGM and TGM levels of seven locations are 52 ± 26 ng m−3 and 1.9 ± 0.6 ng m−3, respectively, which shows that the surface seawater in Tokyo Bay is supersaturated with gaseous mercury, leading to an average mercury evasional flux of 140 ± 120 ng m−2d−1. On the other hand, the annual average wet and dry depositional fluxes of mercury at three locations were 19 ± 3 μg m−2yr−1 and 20 ± 9 μg m−2yr−1, respectively. These depositional fluxes correspond to the daily average total depositional flux of 110 ± 20 ng m−2d−1. Thus, it is suggested that in Tokyo Bay, the evasional fluxes of mercury are comparable to the depositional fluxes.  相似文献   

11.
球形棕囊藻(Phaeocystisglobosa)是我国南方沿海近年来主要的赤潮原因种之一,由球形棕囊藻形成的赤潮对海水养殖业发展和海域生态环境构成了严重威胁。棕囊藻通常以囊状群体形式形成赤潮,很难获取其丰度数据,以往研究中多以19′-己酰氧基岩藻黄素(Hex-fuco)或19′-丁酰氧基岩藻黄素(But-fuco)作为其特征色素,利用化学分类软件CHEMTAX计算其生物量。为了解我国近海球形棕囊藻的色素组成特征,本文采用高效液相色谱方法,分析了6株球形棕囊藻的色素组成与含量状况,其中5株分离自我国近海。结果表明, 6株球形棕囊藻均以岩藻黄素和叶绿素a为主要色素,但其特征色素Hex-fuco却存在显著的株系间差异,即便是分离自相同海域的不同球形棕囊藻藻株也存在差别。对比棕囊藻游离细胞和囊状群体的色素组成,可以看出两者在色素组成上基本一致,但囊状群体中捕光色素(Light-harvesting pigment)含量低于游离细胞,而光保护色素(Photoprotective pigment)则高于游离细胞,可能与不同存在形态的棕囊藻对光照的适应特征差异有关。以上研究表明,在以CHEMTAX方法计算球形棕囊藻生物量时,需要充分调查海域棕囊藻的特征色素组成情况,获取其特征色素信息,构建合理色素比例初始矩阵,为球形棕囊藻赤潮监测奠定基础。  相似文献   

12.
沈萍萍  齐雨藻  欧林坚 《海洋科学》2018,42(10):146-162
球形棕囊藻(Phaeocystis globosa Scherffel)是全球海洋广泛分布的有害藻华种类。1997年10月,中国东南沿海首次暴发了此种藻类的大规模藻华,其后陆续在福建、广东、广西、海南、河北及天津等省市沿海暴发多起同种藻华。中国近海的球形棕囊藻藻华呈现两大独有的特点,即藻类囊体较大(可达3厘米),以及藻华可毒害养殖业。历经20多年,球形棕囊藻在中国沿海已从一个"藻华新记录种"变成了"藻华常见种"。值得注意的是, 2014年以来,广西北部湾海域棕囊藻藻华肆虐,威胁核电冷源安全,受到了社会高度关注,也对球形棕囊藻藻华的研究提出了新的挑战与要求。针对这一生态灾害的最新发展趋势,本文总结了20年来中国球形棕囊藻及其藻华灾害的发生与发展状况,分别就棕囊藻的分类、生活史特征、营养特性、藻华形成的环境驱动因素、生态毒理等诸多方面开展简要综述,冀望为棕囊藻藻华的研究及防治提供基础资料及思路。  相似文献   

13.
通过制备针对东海原甲藻细胞破碎物的多克隆和单克隆抗体,建立了基于双抗体酶联免疫分析定量检测东海原甲藻(Prorocentrum donghaiense)的检测方法。利用该方法对单一藻种、混合藻种和现场样品中的东海原甲藻进行检测的结果与镜检结果相一致,最低检测限度为1×103 cells/m L。该方法的建立对中国近海赤潮暴发的实时监控具有重要意义。  相似文献   

14.
在实验室内不同盐度梯度下培养常见的两种赤潮藻——中肋骨条藻(Skeletonema costatum s.l.)和东海原甲藻(Prorocentrum donghaiense),根据logistic生长模型获得了终止生物量Bf和最大生长速率μmax,并测定了藻体中过氧化物酶(POD)、二胺氧化酶(DAO)、多胺氧化酶(PAO)的活性和丙二醛(MDA)、腐胺(Put)、亚精胺(Spd)、精胺(Spm)的含量。结果表明,高、低盐度胁迫下,两种藻均会积累MDA,活性氧自由基的伤害增强,藻的生长受到了抑制。同时,两种藻都会提升多胺含量,通过多胺的调节作用来缓解胁迫的伤害,促进生长,但是在提升的多胺种类和形态上,两种藻存在着差异。高盐胁迫下,中肋骨条藻会提升多胺尤其是游离态多胺的含量来缓解伤害,东海原甲藻则依靠结合态的亚精胺和游离态的精胺的调节作用。低盐胁迫下,中肋骨条藻会提升游离态腐胺的含量,而东海原甲藻体内各形态的多胺都会上升。  相似文献   

15.
本文主要探究了东海原甲藻(Prorocentrum donghaiense)与三角褐指藻(Phaeodactylum tricornutum)之间的他感作用。在实验室模拟条件下,分别研究了添加比例为10%、40%、60%、90%、100%的三角褐指藻无藻细胞滤液的培养基对东海原甲藻生长的影响,以及相同比例的东海原甲藻无藻细胞滤液培养基对三角褐指藻生长的影响。结果表明,低浓度三角褐指藻滤液对东海原甲藻(P.donghaiense)的生长表现为促进作用,高浓度则抑制其生长,因此,不同浓度的三角褐指藻藻液对东海原甲藻生长表现出两种相反的他感作用效果;而东海原甲藻滤液对三角褐指藻(P.tricornutum)的生长没有显著影响,说明东海原甲藻并未对三角褐指藻表现出他感作用。  相似文献   

16.
采用单养和混养的方法,在实验条件下研究了东海原甲藻对中华哲水蚤摄食和消化酶活性的影响.结果表明:(1)中华哲水蚤对东海原甲藻存在一定摄食行为,藻类密度对摄食率有明显的影响.实验密度下,中华哲水蚤对东海原甲藻的最大摄食率为930cells/(ind·h).滤水率随着藻密度的增加而呈单一性的下降;(2)混养条件下,中华哲水蚤对金藻和东海原甲藻的摄食率均较单养时下降,滤水率的变化与摄食率相似;(3)不同藻密度下,昆布多糖酶活性都明显高于麦芽糖酶和纤维二糖酶的活性,而麦芽糖酶活性又稍高于纤维二糖酶的活性.与金藻相比,东海原甲藻实验组中华哲水蚤3种消化酶活性明显升高(P<0.05).  相似文献   

17.
利用改性粘土去除藻华生物是目前有害藻华应急处置最常用的方法。本文研究了六种铝盐改性粘土(PAC-MC、PAFC-MC、PAFCs-MC、AC-MC、AS-MC、PAS-MC)对藻华生物球形棕囊藻(Phaeocystis globosa)、东海原甲藻(Prorocentrum donghaiense)的去除效率,考察了悬浮液pH、改性粘土颗粒表面电位及粒径分布等因子对去除效率的影响。结果显示:不同赤潮生物由于生物特征不同,其去除效率存在较大差异,PAC-MC、PAFC-MC、PAFCs-MC对东海原甲藻有较高的去除效率,但对于球形棕囊藻去除能力较差;AC-MC、AS-MC、PAS-MC对两种藻华生物均有较好的去除效果,但对水体酸碱扰动较大,在pH敏感水域应注意用量;对于同一种改性粘土,提高铝离子含量、增加改性粘土浓度有利于除藻效率的提升;自絮凝程度越低、表面正电性越强(或负电性越弱)、悬浮液pH值越低的改性粘土,除藻能力越强。本研究进一步为改性粘土应急处置有害藻华提供了参考。  相似文献   

18.
《Journal of Sea Research》2000,43(3-4):345-356
During spring blooms 1998 and 1999, three complementary methods were used to evaluate the in situ feeding activities of the dominant copepod species of the Belgian coastal zone: gut pigment content analysis using HPLC, the 14C tracer method, and cell count experiments. The results obtained by all three methods consistently showed that Phaeocystis globosa is not an adequate food source for the spring copepods in the Belgian coastal zone. Our results demonstrated that, among the potential prey, copepods strongly selected diatoms and microzooplankton, and that these types of prey accounted for the major part of the ingested carbon. However, diatoms and microzooplankton ingestion did not always seem sufficient in terms of carbon to avoid food limitation. Comparison of clearance rates exerted on different potential prey types during the P. globosa peak with those before and after the P. globosa peak showed that the copepods' feeding pressure on diatoms was reduced during the P. globosa peak while that on microzooplankton was not. The low grazing pressure on P. globosa, together with the preferential grazing on diatoms, which reduces the competition for nutrients, and the predation on microzooplankton organisms, which reduces the microzooplankton grazing pressure on P. globosa cells, are likely to favour the P. globosa bloom in the Southern Bight of the North Sea.  相似文献   

19.
A straightforward ecophysiological characterization of Phaeocystis globosa is hampered by its complex polymorphic life cycle in whic flagellates and colonial cells express different physiological and morphological properties. There is also increasing evidence that, besides the existence of different species, the most widespread species Phaeocystis globosa (Scherffel) has to be subdivided into at least five different ecotypes which again differ in their ecophysiological properties. Most research has been performed on the P. globosa ecotype North European (English Channel/ North Sea isolates). From the available literature it must be concluded that flagellate cells are better competitors for light and phosphate than colonial cells, due to their superior uptake characteristics. To a limited extent this phenomenon is compensated in colonial cells by their ability to continue growth and cell division in the dark at the same rate as in the light, at the expense of extracellular colonial mucus. In contrast with other algal species, colonial cells of P. globosa are better competitors for nitrogen than for phosphorus.Flagellates transform into vegetative cells and form colonies in environments with irradiance levels of about 50 μE·m−2·s−1 or more and an optimum phosphate concentration of 1 μM. A solid substrate and the presence of calcium are prerequisites for colony formation. In environments where phosphorus is limiting no new colonies are formed. There is some evidence that nitrate stimulates colony formation, whereas high ammonium values (above 1 μM) tend to suppress colony formation. Massive blooms of P. globosa colonies can be attributed to a combination of environmental conditions that induce colony formation and smaller grazing losses of colonial cells than of flagellates, rather than to superior ecophysiological characteristics of colonial cells.  相似文献   

20.
Rhodoliths are important marine carbonate producers that provide habitat for several marine organisms, and are threatened by ongoing global climate change. Meter‐sized sedimentary patches rich in living rhodoliths, interspersed among corals, were discovered in the back reef of Ras Ghamila lagoon, Southern Sinai, at less than 1 m water depth. In this shallow and relatively sheltered subtropical environment, rhodoliths were found to be monospecific or oligospecific, spheroidal, 3.5 to 9.4 cm in maximum diameter, with warty/lumpy or fruticose (protuberance degree IV) growth forms, and corresponded to the unattached branches or praline type. They grew in bright light under seasonal, moderate, wind‐driven water motion. The dominant rhodolith‐forming species recorded were: Lithophyllum kotschyanum, Porolithon onkodes, Hydrolithon sp. and three species of Neogoniolithon: Neogoniolithon fosliei, Neogoniolithon brassica‐florida, and an undescribed species noted in the text as Neogoniolithon sp. A total of 38 Alizarin‐stained rhodoliths was released in the field and collected after 1 year. They showed different banding patterns (alternating long and short cells) that revealed seasonal growth, with the lowest rates occurring in winter for all species, and an additional summer growth slackening in Neogoniolithon fosliei. Lithophyllum kotschyanum presented evidence of occasional growth cessation, possibly due to temporary burial. The observed annual growth rate of rhodoliths was unrelated to their size. The mean accretion rates were 1.08 mm · year?1 in L. kotschyanum, 0.75 mm · year?1 in P. onkodes, 0.49 mm · year?1 in Hydrolithon sp., 0.85 mm mm · year?1 in N. fosliei, 0.63 mm · year?1 in N. brassica‐florida and 0.57 mm · year?1 in Neogoniolithon sp. The annual mean marginal elongation rate for these taxa was respectively 8.74, 13.92, 3.59, 9.40 and 9.25 mm · year?1, with the exception of Neogoniolithon sp., for which this parameter was not recorded. Maximum marginal elongation occurred in P. onkodes pointing out its greater ability as a space competitor in comparison with the other rhodolith species. The highest accretion rate and common presence of L. kotschyanum indicate its importance as carbonate producer in tropical reef.  相似文献   

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