Research on red tide occurrences using enclosed experimental ecosystems in west Xiamen Harbor, China—Relationship between various factors and red tide occurrences

A series of enclosed ecosystem experiments were conducted in a land-based tank near the seaside of West Xiamen Harbor. The results of experiments conducted in different seasons and years showed a repeatable phytoplankton succession. In this relatively stable ecosystem with added nutrients and trace metals, diatoms dominated initially, dinoflagellates dominated in the later stage, and dinoflagellate red tides eventually occurred. Vitamin B₁₂ enrichment may speed up this succession process. Stirring the water column could stop this process. Soluble Mn at a level of 3–4 μg/L in seawater, which also is the existing concentration of soluble Mn in Xiamen Harbor seawater, is sufficient for the multiplication of algae and occurrence of red tide. The present study showed that excessive soluble Mn in Xiamen Harbor cannot cause red tide, and that Fe was one of the important factors causing diatiom red tide in this present study. Project 39570145 supported by NSFC.     

海洋围隔生态系中环境因子对长牡蛎的生态效应

本研究应用海洋围隔实验技术探索围隔生态系中环境因子对长牡蛎的生态效应。研究结果表明：牡蛎养殖密度与牡蛎体重增长呈负相关;养殖水体的Ｎ、Ｐ平均浓度分别达到２６．４和２．５μｍｏｌ／ｄｍ＾３的水平时牡蛎生物较佳;服物浓度过高会导致牡蛎死     

可溶性Fe对中尺度海洋围隔生态系中浮游生物群落数量变动的影响

作者首次应用3个中尺度海洋实验生态系围隔装置研究可溶性Fe 对浮游生物群落数量变动的影响。结果表明:添加10和50μg/dm~3的可溶性Fe,均大大促进了浮游植物,特别是硅藻类中中肋骨条藻(Skeletonema costatum)的生长。但浮游植物的过量繁殖并没有导致生态系中滤食性桡足类数量的增加。     

Effects of simulated benthic fluxes on phytoplankton dynamic and photosynthetic parameters in a mesocosm experiment (Bay of Brest,France)

Benthic faunal activity and density play an important role in determining the rates of benthic nutrient fluxes, which enrich the water column and contribute to phytoplankton growth. The intensity of nutrient fluxes in the Bay of Brest depends on the density of the invasive gastropod, Crepidula fornicata. In order to study the impact of benthic fluxes on phytoplankton dynamics, realistic daily nutrient inputs simulating various densities of C. fornicata were added to six enclosures during three weeks. The increase in fertilization intensity influenced the phytoplankton biomass. A succession from Chaetoceros spp. to Pseudo-nitzschia spp. and Leptocylindrus danicus was observed in all enclosures, but the dynamics of successions were different. Pseudo-nitzschia spp. was favored in the three more fertilized enclosures, while Chaetoceros spp. persisted longer in less enriched enclosures. Despite an apparent nitrogen limitation, the quantum efficiency of PSII (F_v/F_m) was high (>0.5) and stable in all enclosures. The maximal photosynthetic capacity (P^Bmax) was also invariable and oscillated around an average value of 2.23 mg C (mg Chl a)⁻¹ h⁻¹. The stability of F_v/F_m and P^Bmax observed at different nutrient input intensities demonstrates that the daily inputs maintained the physiological balance of the microalgae. The maximal light utilization efficiency (α) and the light saturation parameter (E_k) were also quite stable after day 8, which reveals that photosynthetic parameters were driven by growth constraints due to nutrient availability and not by incident light or species successions. We suggest that our results correspond to an “E_k independent variation” regulation. We propose that such regulation of photosynthetic parameters appears when there are frequent nutrient additions which do not allow replete nutrient conditions to be reached but lead to physiological equilibrium.     

RESEARCH ON RED TIDE OCCURRENCES USING ENCLOSED EXPERIMANTAL ECOSYSTEMS IN WEST XIAMEN HARBOR, CHINA——RELATIONSHIP BETWEEN VARIOUS FACTORS AND RED TIDE OCCURRENCES

ＩＮＴＲＯＤＵＣＴＩＯＮＲｅｄｔｉｄｅｓｏｃｃｕｒｒｅｄｉｎＸｉａｍｅｎＨａｒｂｏｒｉｎ1986ａｎｄ1987.Ｔｈｅｌｏｃａｌｍａｒｉｎｅｓｃｉｅｎｔｉｓｔｓｃｌｏｓｅｌｙｏｂｓｅｒｖｅｄｔｈｅｓｅｒｅｄｔｉｄｅｓａｎｄｏｂｔａｉｎｅｄｍｕｃｈｕｓｅｆｕｌｄａｔａ(Ｚｈａｎｇｅｔａｌ.,1988;Ｄｕ,1989;Ｚｈｕａｎｇ,1991;Ｃｈｅｎｇｅｔａｌ.,1993).Ｂｕｔｓｉｍｕｌｔａｎｅｏｕｓｔｒａｎｓｉｅｎｔｗａｔｅｒｍｏｖｅｍｅｎｔａｌｗａｙｓｍａｄｅｉｔｄｉｆｆｉｃｕｌｔｔｏｉｎｖｅｓｔｉｇａｔｅｔｈｅｓｅｒｅｄｔｉ…