Seasonality of Plankton Assemblages in a Temperate Estuary   总被引：3，自引：0，他引：3  

Jefferson T.  Turner  Stephen F.  Bruno  Ralph J.  Larson  Robert D.  Staker Gurdial M.  Sharma 《Marine Ecology》1983,4(1):81-99

Abstract. Synoptic measurements of temperature, salinity, nutrients, primary productivity, chlorophyll a, and abundance and composition of phytoplankton, zooplankton, and ichthyoplank-ton were made over an annual cycle on the Peconic Bay estuary (Long Island, New York, USA). There were pronounced seasonal fluctuations in all variables measured. During the warmer season, the plankton was dominated by nanophytoplankton (athecate microflagellates and chlorophytes, short chains of diatoms), small zooplankton (copepod nauplii, copepodites, and adults of small copepod species) and gelatinous carnivores (ctenophores and medusae). During the colder season, the plankton was dominated (in terms of primary productivity and chlorophyll a) by netplankton, larger zooplankton (adult copepods) and fish larvae. The winter bloom of apparent netplankton (> 20 μm fraction) was largely an artifact of the screening method employed, in that long chains of a diatom with small individual cell size (Skeletonema costatum) comprised 84.4–97.8% of the phytoplankton present. There was a significant negative relationship over the year between length of diatom chains and number of smaller zooplankton. For this reason, as well as initiation of the winter bloom during a period of declining levels of both light and zooplankton, inception of the bloom appeared more related to release of zooplankton grazing pressure than to illumination. Temporally offset pulses of ctenophores and other zooplankton during the warmer season suggest substantial predation by ctenophores. Apparent decimation of copepod populations by ctenophore predation in late summer and fall immediately preceeded inception of the winter diatom bloom. Larval Ammodytes americanus were the dominant ichthyoplankton, and these co-occurred in winter with increased abundances of larger adult copepods of species upon which A. americanus is known to feed. With certain modifications the patterns recorded for Peconic Bay corresponded to both of two generalized trophic pathways proposed by Greve & Parsons (1977) for temperate waters: nanoplankton → small zooplankton → gelatinous zooplankton carnivores or netplankton → larger zooplankton → young fish. The former pattern characterized the warmer season, and the latter the colder season. Comparison of patterns in Peconic Bay with those in some other temperate estuarine and coastal waters suggests similarity, particularly for estuaries of the northeastern United States.  相似文献   

Synoptic sampling reveals spatial stability in flow and chemistry patterns despite large seasonal variability in a subarctic mountain catchment     

Arsh Grewal  Sean K. Carey 《水文研究》2024,38(2):e15080

Seasonality plays a critical role in cold mountain regions as variation in air temperature, ground thermal status, and precipitation phase alter the rate, timing and magnitude of hydrological and chemical transport. Additionally, cold mountain catchments can have highly variable topography, geology, permafrost, and landcover, which intrinsically add to this irregularity. Understanding how external and internal variability act to control mass fluxes requires sampling at a high spatial resolution over time, which rarely occurs in cold remote regions. In this work, we conduct five snapshot sampling surveys across 34 subcatchments during the ice-free period in Wolf Creek Research Basin (a mesoscale montane subarctic catchment) and two additional winter surveys across a subset of sites to assess the drivers of variability in stream chemistry and discharge. We sampled for specific conductance (SpC), major ions, and dissolved organic carbon (DOC) and used statistical metrics and Bayesian mixing analysis to quantify patterns of flow and chemistry across space and time. Our results indicate patterns in both flow and chemistry remain largely consistent across seasons for all solutes. However, there was weaker correlation of chemistry between sites, suggesting asynchronous behaviour within the catchment. There was evidence of increasing production of ions and DOC along the stream network during high spring flows but not during low flows. Although concentrations and flows exhibit high seasonality in subarctic mountains, this seasonal variability does not alter spatial patterns that arise from highly variable catchment characteristics.  相似文献   

Remote sensing and avian influenza: A review of image processing methods for extracting key variables affecting avian influenza virus survival in water from Earth Observation satellites     

Annelise Tran  Flavie Goutard  Lise Chamaillé  Nicolas Baghdadi  Danny Lo Seen 《International Journal of Applied Earth Observation and Geoinformation》2010

Recent studies have highlighted the potential role of water in the transmission of avian influenza (AI) viruses and the existence of often interacting variables that determine the survival rate of these viruses in water; the two main variables are temperature and salinity.  相似文献   

Role of latitudinal shift and climate change in evolution of red and yellow palaeosols of the Himalayas: Implications for early Oligocene seasonality and Mid-Miocene enhanced precipitation     

Neha Upreti  Pankaj Srivastava 《Sedimentology》2020,67(4):2189-2221

Cenozoic atmospheric circulation, climatic changes, sedimentation and weathering over the Indian sub-continent were mainly influenced by the northward drift of the Indian Plate, the shrinking Paratethys, India-Asia collision and the rise of the Himalayas. This study is aimed at exploring the fluvial sedimentary record of the north-west part of the Himalayan Foreland Basin to interpret weathering and pedogenesis during early Oligocene to Mid-Miocene time. Palaeopedological investigation of a 3.1 km thick succession from Kangra sub-basin of the Himalayan Foreland Basin shows that the lower 2 km part of the succession is characterized by the red (10R hue) and the upper 1.1 km part of the succession by the yellow (2.5Y hue) palaeosols with varying intensity of weathering and pedogenesis. The association of sedimentary rocks and pedogenic expression in palaeosols indicate four (Type-A to Type-D) pedofacies in the entire Oligocene–Miocene succession. The pedofacies are defined by a decrease in the intensity of palaeopedogenic development from strongly-developed palaeopedofeatures in Type-A, moderately-developed palaeopedofeatures in Type-B, weakly-developed palaeopedofeatures in Type-C and to the only incipient stage of palaeopedogenesis in Type-D pedofacies. The palaeolatitudinal shift during the convergence of the Indian Plate played a major role in weathering and palaeopedogenesis with the inception of seasonality during the early Oligocene, which is demonstrated by the formation of the red palaeosols with pedogenic CaCO₃ and vertic features in tropical conditions. The transition to yellow palaeosols at about 20 Ma is marked by increased humidity, rapid aggradation, pronounced uplift and enhanced erosion of the hinterland. These yellow palaeosols are characterized by the abundance of weakly-developed Bw and Bss horizons, pure clay pedofeatures and absence of any pedogenic CaCO₃ during short pedogenic intervals in subtropical conditions.  相似文献   

Epilithic ectoenzyme activity in a nutrient-rich Mediterranean river     

Anna M. Romaní  Sergi Sabater 《Aquatic Sciences - Research Across Boundaries》1999,61(2):122-132

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1948—2015年北半球平流层爆发性增温的统计特征和月际环流差异          下载免费PDF全文

王华曌  饶建  生宸  王博 《大气科学学报》2019,42(6):880-891

利用NCEP/NCAR第1套再分析资料,分析过去68 a(1948—2015年)平流层爆发性增温(Stratospheric Sudden Warming,SSW)频次、强度和环流特征的月际差异。统计结果表明:1948—2015年北半球共发生30次SSW,其集中发生在11—3月,而1—2月发生频次尤为集中,且SSW发生频次表现出显著的年代际变化特征。11—12月SSW比1—3月SSW的持续时间长。而3月SSW事件的强度最弱,持续时间最短。1月和3月SSW纬向平均信号下传得较深,而11月、12月和2月的环流信号仅能传到200 hPa。11—3月SSW爆发前1～2周500 hPa均观测到西太平洋遥相关型(Western Pacific,WP)的负位相;太平洋-北美遥相关型(Pacific-North America,PNA)的正位相仅仅出现在11月、12月和3月SSW爆发前。SSW爆发后1～2周,仅有11月、1月和3月的事件对应着负位相的北大西洋涛动(North Atlantic Oscillation,NAO)。  相似文献   

Growth dynamics and bioactivity variation of the Mediterranean demosponges Agelas oroides (Agelasida, Agelasidae) and Petrosia ficiformis (Haplosclerida, Petrosiidae)     

Cristina Ferretti  Simone Vacca  Chiara De Ciucis  Barbara Marengo  Alan R. Duckworth  Renata Manconi  Roberto Pronzato  & Cinzia Domenicotti 《Marine Ecology》2009,30(3):327-336

Growth dynamics and bioactivity variation of the Mediterranean demosponges Agelas oroides and Petrosia ficiformis were investigated over 15 months at Paraggi and Colombara within the Marine Reserve of Portofino Promontory (Mediterranean Sea, Ligurian Sea, Italy). For both species, growth rates varied between individuals and were unaffected by initial sponge size. The two species showed a different trend in growth pattern: A. oroides did not vary significantly between seasons, sites and depths; in contrast, some individuals of P. ficiformis showed a seasonal pattern, shrinking during winter as water temperature decreased and growing during summer when water temperature increased. Differences in growth between the two species may result from different reproductive cycles, food availability, species-specific thermophily and patterns of spatial competition. Moreover, spatial competition probably induced sponges to produce bioactive secondary molecules. Spatial and temporal variation of bioactivity of both species was examined for the first time by studying its effect on human neuroblastoma cells. The bioactivity of A. oroides extracts differed significantly between seasons, sites and depths, whereas the cytotoxicity of P. ficiformis differed significantly between seasons and depths (differences for sites were not determined). These results suggest the possible influence of environmental factors on bioactive metabolite biosynthesis.  相似文献   

Spatial and temporal prokaryotic variability in the northern Adriatic Sea     

Paola Del Negro  Mauro Celussi  Erica Crevatin  Alessandro Paoli  Fabrizio Bernardi Aubry  Alessandra Pugnetti 《Marine Ecology》2008,29(3):375-386

The prokaryotic community, both in terms of abundance and activity (exoenzymatic hydrolysis of proteins, polysaccharides and phosphorylated molecules and leucine uptake), was investigated seasonally for a 3‐year period (2004–2006) in the Gulf of Venice (northern Adriatic Sea). By focusing on spatial and temporal variability, the prokaryote dynamics showed significant variations on a horizontal and seasonal scale, but no substantial differences were observed among years. The basin‐scale variability was mainly influenced by allochthonous inputs from the Po river and the Venice Lagoon, which were the main source of nutrients, acting as a ‘bottom up’ control on prokaryotes. On a seasonal scale, all the microbial parameters (except the polysaccharide degradation) showed significant variations following the temperature fluctuations. The annual rate of change was very low for all the chemical, physical and biological parameters and only the abundance and phosphatase activity of the prokaryotes differed significantly among years.  相似文献   

Fish assemblages and rapid colonization after enlargement of an artificial reef off the Algarve coast (Southern Portugal)     

Francisco Leitão  Miguel N. Santos  Karim Erzini  Carlos C. Monteiro 《Marine Ecology》2008,29(4):435-448

Artificial reefs (ARs) have been deployed in Algarve (Southern Portugal) coastal waters to contribute to the sustainability of local nearshore fisheries. Herein, we describe the colonization process of the recently deployed Faro/Ancão AR, and assess the time until the fish assemblage reaches stability and their seasonal patterns. In addition, we compare the results from the present study with those previously reported for an older AR. The fish assemblages were monitored monthly over a 2‐year period by means of visual census. A rapid increase in fish colonization occurred within the first 4 months. After this initial period the assemblage structure showed high similarity (> 73%). The high rate of colonization of the AR was related to the maturity already achieved by the nearby 14‐year‐old AR and to the fish migration from the Ria Formosa lagoon, a nearby nursery habitat. The reef fish assemblage structure showed a seasonal pattern, mainly associated with recruitment episodes of occasional demersal species (Boops boops, Trachurus trachurus and Pagellus spp.) in spring and summer. A total of 66% of the species found in AR are of commercial and recreational importance. The overall mean density and biomass were 2.8 ind·m^?3 and 207 g·m^?3. The occasional demersal species accounted for 42% of the fish density. The most important species in terms of biomass belong to the Sparidae family along with Dicentrarchus labrax. The fish assemblage of the new ARs showed higher mean number of species, diversity, density and biomass values than those reported for the older AR. This result was associated with enlargement of the AR area and with the fishing exploitation of the isolated, small and patchy old AR. Moreover, the high biomass values recorded in the new ARs were mainly due to the increased density of D. labrax after AR enlargement. The results of the present study are used to define guidelines for suitable management strategies for the AR areas that are exploited by the local commercial and recreational fisheries.  相似文献   

基于熵测度方法的旅游季节性研究   总被引：1，自引：1，他引：0  

余向洋  张圆刚  朱国兴  李德明  王娟 《地理科学进展》2019,38(8):1240-1247

针对旅游季节性研究缺乏深入细致的长期纵向跟踪研究和测度方法众多问题,论文采用国内旅游学者尚未使用过的熵测度方法,以黄山风景区连续10 a的日接待数据为基准,深入剖析周、月、年度多个层面的季节性,结果表明：① 熵冗余指数测度旅游的年、月、周季节性具有一定的简洁性优势,并且其组合方法具有较强的政策指导意义。采用月度数据计算的熵冗余指数与基尼系数、季节强度指数具有同样的功效,其两两相关性达0.968以上;另外,利用日数据计算的月和周熵冗余指数及与其他指数的组合方法,能够判识各月、各周的季节性变动,具有微观的政策指导意义。② 熵分解方法既可以分析历年的季节性趋势,又可以观察出季节性变动趋势的内在根源。根据熵分解结果,黄山风景区季节性变动总体趋缓,月际和周际的季节性波动减弱,但月内周内的不均衡性反而增强。根据案例分析结果,将熵测度方法用于旅游季节性研究,很大程度上完善了旅游季节性研究的理论内涵和测度方法,更为重要的是提升了旅游季节性研究的政策指导作用。  相似文献