环境因素对杭州湾中型浮游动物群落结构的控制作用

A quarterly study of mesozooplankton community structure and environmental variables in the Hangzhou Bay was conducted to examine the response of mesozooplankton community to the variation of water mass and environmental condition. The southeast coast of China is a typical region under the intensive influence of Asia monsoon and freshwater discharge from rivers. The water mass and environmental condition of the Hangzhou Bay, which were influenced by the interaction of currents, freshwater discharge of the Qiantang River and Changjiang River Plume, showed significant seasonal variation. Our results showed that both biomass and abundance were significantly higher in summer((247.7±148.8) mg/m~3 and(350.9±215.6) ind./m~3, respectively)than those in other seasons. Four eco-geographical regions were divided based on the cluster analysis of zooplankton community of the Hangzhou Bay throughout the year, except for winter. Monsoon and the dissolved inorganic nitrogen(DIN) input from freshwater discharge of the Qiantang River and Changjiang River resulted in temporal and spatial variations of environmental gradient in the Hangzhou Bay, which significantly influenced the structure of mesozooplankton community. Redundancy analysis(RDA) indicated that the mesozooplankton community structure was strictly correlated with the DIN gradient, while salinity gradient showed a weak influence in the Hangzhou Bay.     

大型水母沙海蜇暴发的温带贫营养海洋生态系统中细菌和浮游植物的关系

Bacterial abundance, phytoplankton community structure and environmental parameters were investigated to study the relationships between bacteria and phytoplankton during giant jellyfish Nemopilema nomurai blooms in the central Yellow Sea during 2013. N. nomurai appeared in June, increased in August, reached a peak and began to degrade in September 2013. Results showed that phosphate was possible a key nutrient for both phytoplankton and bacteria in June, but it changed to nitrate in August and September. Phytoplankton composition significantly changed that pico-phytoplankton relative biomass significantly increased, whereas other size phytoplankton significantly decreased during jellyfish bloom. In June, a significantly positive correlation was observed between chlorophyll a concentration and bacterial abundance(r=0.67, P0.001, n=34).During jellyfish outbreak in August, there was no significant correlation between phytoplankton and bacteria(r=0.11, P0.05, n=25), but the relationship(r=0.71, P0.001, n=31) was rebuilt with jellyfish degradation in September. In August, small size phytoplankton occupied the mixed layer in offshore stations, while bacteria almost distributed evenly in vertical. Chlorophyll a concentration significantly increased from(0.42±0.056) μg/L in June to(0.74±0.174) μg/L in August, while bacterial abundance just slightly increased. Additionally, the negative net community production indicated that community respiration was not entirely determined by the local primary productivity in August. These results indicated that jellyfish blooms potentially affect coupling of phytoplankton and bacteria in marine ecosystems.     

秦皇岛海域浮游植物的群落结构特征

2014年4~9月对秦皇岛海域进行了调查,共鉴定出浮游植物3门33属70种,以硅藻门为主,7、8月份浮游植物种类数最多,约40种。在整个调查期间,浮游植物丰度在不同站位和月份之间差异较大,平均值为2.42×108个/m3,浮游植物优势种有北方娄氏藻、尖刺拟菱形藻、丹麦细柱藻、微小原甲藻等,优势种种类数9月最多,6月最少。浮游植物多样性指数为1.27~3.6,均匀度为0.31~0.73,6月份群落结构较单一,其他月份群落结构较稳定。     

Linking Structural Equation Modeling with Bayesian Network and Its Application to Coastal Phytoplankton Dynamics in the Bohai Bay

Bayesian networks (BN) have many advantages over other methods in ecological modeling, and have become an increasingly popular modeling tool. However, BN are flawed in regard to building models based on inadequate existing knowledge. To overcome this limitation, we propose a new method that links BN with structural equation modeling (SEM). In this method, SEM is used to improve the model structure for BN. This method was used to simulate coastal phytoplankton dynamics in the Bohai Bay. We demonstrate that this hybrid approach minimizes the need for expert elicitation, generates more reasonable structures for BN models, and increases the BN model’s accuracy and reliability. These results suggest that the inclusion of SEM for testing and verifying the theoretical structure during the initial construction stage improves the effectiveness of BN models, especially for complex eco-environment systems. The results also demonstrate that in the Bohai Bay, while phytoplankton biomass has the greatest influence on phytoplankton dynamics, the impact of nutrients on phytoplankton dynamics is larger than the influence of the physical environment in summer. Furthermore, although the Redfield ratio indicates that phosphorus should be the primary nutrient limiting factor, our results show that silicate plays the most important role in regulating phytoplankton dynamics in the Bohai Bay.     

The biota of Romanian saline lakes on rock salt bodies: A review

An inventory of the aquatic and circum-lacustrine flora and aquatic fauna of 23 karst- and anthroposaline lakes formed on Miocene rock salt bodies in Romania was undertaken. Simultaneous field determinations of water and sediment pH, total dissolved solids, Secchi transparency and lake maximum depth were also made. Environmental conditions for phytoplankton, microphytobenthos, macrophyte and cormophyte species were defined. Relations between the numbers of plankton, microbenthos, macrophyte and cormophyte species differentiated pelogenous (usually, therapeutic) and non-pelogenous lakes. High densities and occurrence frequencies characterized the most representative species. For three of these species, Amphora veneta, Artemia sp. and Potamogeton pectinatus, ecological conditions were noted. In the circum-lacustrine vegetation, glycophytes were more important than halophytes.     

灌浆期气象条件对小麦灌浆及产量的影响

利用两种典型年份小麦灌浆期气象资料和产量资料，分析了灌浆期气象条件对灌浆进程及产量的影响，结果表明，土壤水份对灌浆速率和灌浆持续时间均有明显影响，并进而影响产量。     

Aquatic primary production in relation to microalgal responses to changing light: A review

Dynamic aspects of algal photosynthesis are set against the background of physical water motions which change the light experienced by the phytoplankton. These time-dependent photosynthetic responses are reviewed in relation to the proposition that phytoplankton primary production may be incorrectly estimated by the commonly used static incubation of light and dark bottles for periods significantly longer than the response-time of phytoplankton to changing light. This proposition is supported by the clear overlap between the timescales which characterize water motions and the timescales reported for the complex responses of algae to changing light. Empirical studies comparing static and dynamic incubations have been inconclusive, as have models incorporating some representation of the dynamic photosynthetic response to changing light. These results reflect weaknesses in the simple formulations used to describe photosynthesis in relation to irradiance, the simplicity of physical schemes used to generate changes in irradiance with time, and a lack of data (field and laboratory) on dynamic responses of microalgae to changing light. The quantitative significance of many physiological mechanisms is not known in relation to their effect on photosynthesis.     

Has the 1998 regime shift also occurred in the oceanographic conditions and lower trophic ecosystem of the Oyashio region?

To examine whether the regime shift in 1998 that has been variously reported to have occurred in the oceanographic conditions of the central and eastern North Pacific also occurred in the Oyashio region, western North Pacific, we compared data over the period 1990–2003. Oceanographic conditions were compared before 1997 with those after 1998, using the A-line dataset (1990–2003) obtained by the oceanographic surveys of the Hokkaido National Fisheries Research Institute, Fisheries Research Agency (HNFRI/FRA). Seasonal changes of the monthly-mean SST (as temperature in the surface layer) show a significant increase in spring after 1998. After 1998, the mean concentration of chlorophyll a at the surface was higher in spring than that before 1997. This was more remarkable in the main current of the Oyashio. These changes suggest that the spring phytoplankton bloom in the Oyashio region after 1998 was larger in magnitude and initiated earlier. Consumption of nutrients during the spring bloom and standing stock of netplankton also shows a distinct difference between the time period before 1997 and after 1998. These results support the occurrence of the regime shift around 1998 in the Oyashio region. The changes of hydrographical conditions accompanying with the 1998 regime shift are discussed. The hydrographic mechanism of enhancement of primary productivity during the spring phytoplankton bloom was not fully clarified, though. Results in this study may support the usefulness of the A-line dataset for analysis of long-term variability in the western subarctic Pacific.     

Microscale gradients of planktonic microbial communities above the sediment surface in a mangrove estuary

The microscale (1 and 4 cm sampling resolution) distributions of chemical (O₂, NH₃, NO₃⁻, NO₂⁻, PO₄³⁻) and biological (Chl a, phytoplankton, bacterioplankton, viruses) parameters were measured in the 16 cm of water immediately overlaying the sediment-water interface (SWI) within a temperate mangrove estuary in South Australia during December 2003 and March 2004. Shear velocities (u_*) during the time of sampling were very low (<0.1 cm s⁻¹), and we consequently predict that resuspension of organisms and materials was negligible. In December 2003, profiles were often characterised by strong gradients in nutrients and organisms, with the highest concentrations often observed within 0.5 cm of the SWI. Microscale patterns in O₂, NH₃, NO₃⁻ and NO₂⁻ indicated that a variety of anaerobic and aerobic transformation processes probably occurred at the SWI and within profiles. Strong gradients in PO₄³⁻ were indicative of nutrient flux across the SWI as a consequence of degradation processes in the sediments. Pico- and nanophytoplankton concentrations were strongly correlated (p < 0.01) to PO₄³⁻, and exhibited 12- and 68-fold changes in abundance, respectively, with highest concentrations observed nearest to the SWI. Several bacterial subpopulations were discriminated using flow cytometry and significant shifts in the ‘cytometric structure’ of the bacterial community were observed within microscale profiles. Two populations of viruses were correlated to the phytoplankton and low DNA (LDNA) bacteria, and each exhibited elevated concentrations within 0.5 cm of the SWI. In March 2004, microscale distributions of O₂ and nutrients were more homogenous than in December 2003, and dissimilar microbial community structure and patterns were observed above the SWI. The patterns observed here support the prediction that benthic processes can strongly influence the ecology of planktonic communities in the overlaying water, and provide further evidence for the existence of microscale variability amongst communities of aquatic microorganisms.     

Temporal Variations of Nutrients, ­Chlorophyll a and Particulate Matter in Three Coastal Lagoons of Amvrakikos Gulf (Ionian Sea, Greece)

Abstract. The temporal variations of nutrients, chlorophyll a (chl a ), suspended particulate matter (SPM) and particulate organic carbon (POC) were measured over 12 months in three shallow coastal brackish water lagoons of the Amvrakikos Gulf, Ionian Sea. Two of the lagoons, Tsoukalio and Rodia, are interconnected but separated from Logarou by a narrow strip of land. Logarou has a better water exchange with the sea as indicated by the higher salinity and dissolved oxygen concentrations and the smaller variation of the above-mentioned parameters. Nitrate concentrations were largely the same in the three lagoons and higher than in the Amvrakikos Gulf. Phosphate concentrations in Logarou exceeded by far those of Tsoukalio/Rodia; the increased phosphate levels recorded in January caused an extended phytoplankton bloom with chl a concentrations higher than in the other two lagoons. Chl a in Tsoukalio was positively correlated with nitrate whereas in the most shallow lagoon, Logarou, it showed a positive correlation with light winds (force 4 and lower), probably caused by resuspension from the sediment. Increased phytoplankton biomass in Logarou coupled with the better water exchange may be related to the higher fish production in this lagoon.