Fish Fauna Status in the Lugu Lake with PreliminaryAnalysis on Cause and Effect of Human Impacts

泸沽湖是位于滇西北的一个断陷湖泊，为滇川两省共有。文献记录泸沽湖原始的鱼类区系由4种鱼 类组成，隶属于裂腹鱼属和泥鳅属。于2001，2002和2004年3次考察泸沽湖，进行标本采集和鱼类区系现状调 查。查看了采自泸沽湖的鱼类标本518号，结合历史上的采集记录和大量相关文献，确定泸沽湖记录有鱼类12 种，隶属于3目4科10属；过度捕捞和毁林造成的泥石流是泸沽湖鱼类区系变化的主要原因。

Impacts of two biomanipulation fishes stocked in a large pen on the plankton abundance and water quality during a period of phytoplankton seasonal succession

Silver and bighead carp were stocked in a large pen to control the nuisance cyanobacterial blooms in Meiliang Bay of Lake Taihu. Plankton abundance and water quality were investigated about once a week from 9 May to 7 July in 2005. Biomass of both total crustacean zooplankton and cladocerans was significantly suppressed by the predation of pen-cultured fishes. There was a significant negative correlation between the N:P weight ratio and phytoplankton biomass. The size-selective predation by the two carps had no effect on the biomass of green alga Ulothrix sp. It may be attributed to the low fish stocking density (less than 40 g m(-3)) before June. When Microcystis dominated in the water of fish pen, the pen-cultured carps effectively suppressed the biomass of Microcystis, as indicated by the significant decline of chlorophyll a in the >38 mu m fractions of the fish pen. Based on the results of our experiment and previous other studies, we conclude that silver and bighead carp are two efficient biomanipulation tools to control cyanobacterial (Microcystis) blooms in the tropical/subtropical eutrophic waters. Moreover, we should maintain an enough stocking density for an effective control of phytoplankton biomass. (C) 2008 Elsevier B.V All rights reserved

Impacts of CO2 enrichment on growth and photosynthesis in freshwater and marine diatoms

The physiological responses of Nitzschia palea Kutzing, a freshwater diatom, to elevated CO2 were investigated and compared with those of a marine diatom, Chaetoceros muelleri Lemmermann previously reported. Elevated CO2 concentration to 700 mu l/L increased the dissolved inorganic carbon (DIC) and lowered the pH in the cultures of N. palea, thus enhancing the growth by 4%-20% during the whole growth period. High CO2-grown N. palea cells showed lower levels of dark respiration rates and higher I (k) values. Light-saturated photosynthetic rates and photosynthetic efficiencies decreased in N. palea with the doubling CO2 concentration in airflow to the bottom of cultures, although the doubling CO2 concentration in airflow to the surface cultures had few effects on these two photosynthetic parameters. N. palea cells were found to be capable of using HCO3 (-) in addition to gaseous CO2, and the CO2 enrichment decreased their affinity for HCO3 (-) and CO2. Although doubled CO2 level would enhance the biomass of N. palea and C. muelleri to different extents, compared with the marine diatom, it had a significant effect on the specific growth rates of N. palea. In addition, the responses of photosynthetic parameters of N. palea to doubled CO2 concentration were almost opposite to those of C. muelleri.

Impacts of a small dam on riverine zooplankton

In order to explore the temporal impacts of a small dam on riverine zooplankton, monthly samples were conducted from November 2005 to June 2006 in a reach of Xiangxi River, China, which is affected by a small hydropower plant. A total of 56 taxa of zooplankton were recorded during the study and rotifers were the most abundant group, accounting for 97% of total taxa, while the others were copepod nauplii and copepod adults. This study indicated that: (1) the small dam in the Xiangxi River study area created distinct physical and ecological conditions relative to free-flowing lotic reaches despite the constrained channel and small size of the dam; (2) the existence of the plant's small dam had a significant effect on the zooplankton community. In long periods of drought or dry seasons the effect of the dam on potamoplankton was more pronounced (e.g., November, February, March, and May). But the downfall or the connectivity of channel appeared to decrease the effect of small hydropower plants on riverine zooplankton (e.g., April). The present observation underscores the need for additional studies that provide more basic data on riverine zooplankton communities and quantify ecological responses to dam construction over longer time spans.

Light histories influence the impacts of solar ultraviolet radiation on photosynthesis and growth in a marine diatom, Skeletonema costatum

Phytoplanktonic species acclimated to high light are known to show less photoinhibition. However, little has been documented on how cells grown under indoor conditions for decades without exposure to UV radiation (UVR, 280-400 nm) would respond differently to solar UVR compared to those in situ grown under natural solar radiation. Here, we have shown the comparative photosynthetic and growth responses to solar UVR in an indoor-(IS) and a naturally grown (WS) Skeletonema costatum type. In short-term experiment (<1 day), phi(PSII) and photosynthetic carbon fixation rate were more inhibited by UVR in the IS than in the WS cells. The rate of UVR-induced damages of PSII was faster and their repair was significantly slower in IS than in WS. Even under changing solar radiation simulated for vertical mixing, solar UVR-induced higher inhibition of photosynthetic rate in IS than in WS cells. During long-term (10 days) exposures to solar radiation, the specific growth rate was much lower in IS than WS at the beginning, then increased 3 days later to reach an equivalent level as that of WS. UVR-induced inhibition of photosynthetic carbon fixation in the IS was identical with that of WS at the end of the long-term exposure. The photosynthetic acclimation was not accompanied with increased contents of UV-absorbing compounds, indicating that repair processes for UVR-induced damages must have been accelerated or upgraded. (C) 2008 Elsevier B.V. All rights reserved.

Field and experimental studies on the combined impacts of cyanobacterial blooms and small algae on crustacean zooplankton in a large, eutrophic, subtropical, Chinese lake

Field and experimental studies were conducted to evaluate the combined impacts of cyanobacterial blooms and small algae on seasonal and long-term changes in the abundance and community structure of crustacean zooplankton in a large, eutrophic, Chinese lake, Lake Chaohu. Seasonal changes of the crustacean zooplankton from 22 sampling stations were investigated during September 2002 and August 2003, and 23 species belonging to 20 genera were recorded. Daphnia spp. dominated in spring but disappeared in mid-summer, while Bosmina coregoni and Ceriodaphnia cornuta dominated in summer and autumn. Both maximum cladoceran density (310 ind. l(-1)) and biomass (5.2 mg l(-1)) appeared in autumn. Limnoithona sinensis, Sinocalanus dorrii and Schmackeria inopinus were the main species of copepods. Microcystis spp. were the dominant phytoplankton species and formed dense blooms in the warm seasons. In the laboratory, inhibitory effects of small colonial Microcystis on growth and reproduction of Daphnia carinata were more remarkable than those of large ones, and population size of D. carinata was negatively correlated with density of fresh large colonial Microcystis within a density range of 0-100 mg l(-1) (r = -0.82, P < 0.05). Both field and experimental results suggested that seasonal and long-term changes in the community structure of crustacean zooplankton in the lake were shaped by cyanobacterial blooms and biomass of the small algae, respectively, i.e., colonial and filamentous cyanobacteria contributed to the summer replacement of dominant crustacean zooplankton from large Daphnia spp. to small B. coregoni and C. cornuta, while increased small algae might be responsible for the increased abundance of crustacean zooplankton during the past decades.

Daily timing of emersion and elevated atmospheric CO2 concentration affect photosynthetic performance of the intertidal macroalga Ulva lactuca (Chlorophyta) in sunlight

The lunar day differs in length from the solar day so that times of low tide vary from day to day. Thus, aerial exposure of intertidal seaweeds may be during the day or during the night. We measured photosynthetic CO, assimilation rates of the intertidal green macroalga Ulva lactuca during exposures of varied daily timings during sunny days of summer to establish how photosynthetic performance responds to emersion timing under varied CO2 levels [at ambient (360 ppmv) and 2x ambient (720 ppmv) atmospheric CO2 concentrations]. There was an increase in net photosynthetic rates following some duration of exposure when the initial timing of exposure occurred during early morning (06.30 h) and late afternoon (17.15 h). In contrast, net rates exhibited a sharp decline with exposure duration when the initial timing of exposure occurred at 09.30 h, 15.30 h and especially at noon (12.30 h), implying the occurrence of a severe photoinhibition resulting from mid-day insolation. Doubled atmospheric CO2 concentration significantly enhanced the emersed photosynthetic rates, indicating that the emersed photosynthesis is CO2-limited at ambient CO2 levels. However, increasing CO2 barely stimulates the emersed photosynthetic rates during mid-day insolation.

Impacts of elevated CO2 concentration on biochemical composition, carbonic anhydrase, and nitrate reductase activity of freshwater green algae

To investigate the biochemical response of freshwater green algae to elevated CO2 concentrations, Chlorella pyrenoidosa Chick and Chlamydomonas reinhardtii Dang cells were cultured at different CO2 concentrations within the range 3-186 μ mol/L and the biochemical composition, carbonic anhydrase (CA), and nitrate reductase activities of the cells were investigated. Chlorophylls (Chl), carotenoids, carbonhydrate, and protein contents were enhanced to varying extents with increasing CO2 concentration from 3-186 μ mol/L. The CO2 enrichment significantly increased the Chl a/Chl b ratio in Chlorella pyrenoidosa, but not in Chlamydomonas reinhardtii. The CO2 concentration had significant effects on CA and nitrate reductase activity. Elevating CO2 concentration to 186 μ mol/L caused a decline in intracellular and extracellullar CA activity. Nitrate reductase activity, under either light or dark conditions, in C. reinhardtii and C. pyrenoidosa was also significantly decreased with CO2 enrichment. From this study, it can be concluded that CO2 enrichment can affect biochemical composition, CA, and nitrate reductase activity, and that the biochemical response was species dependent.

Mobilization potential of heavy metals: A comparison between river and lake sediments

Toxic metals introduced into aquatic environments by human activities accumulation in sediments. A common notion is that the association of metals with acid volatile sulfides (AVS) affords a mechanism for partitioning metals from water to solid phase, thereby reducing biological availability. However, variation in environmental conditions can mobilize the sediment-bound metal and result in adverse environmental impacts. The AVS levels and the effect of AVS on the fate of Cu, Cd, Zn, Ni in sediments in the the Changjiang River, a suboxic river with sandy bottom sediment and the Donghu Lake, a anoxic lake with muddy sediment in China, were compared through aeration, static adsorption and release experiments in laboratory. Sips isotherm equation, kinetic equation and grade ion exchange theory were used to describe the heavy metal adsorb and release process. The results showed that AVS level in the lake sediment are higher than that of the river. Heavy metals in the overlying water can transfer to sediments incessantly as long as the sediment remains undisturbed. The metal release process is mainly related to AVS oxidation in lake sediment while also related to Org-C and Fe-Mn oxyhydroxide oxidation in river sediment. The effect of sulfides on Zn and Ni is high, followed by Cd, and Cu is easy bound to Org-C. AVS plays a major role in controlling metals activity in lake sediment and its presence increase the adsorption capacity both of the lake and river sediments.

Impacts of Choerospondias axillaris growth on acidity of Udic Ferrosols in subtropical China

Changes in acidity of Udic Ferrosols, caused by growth of Choerospondias axillaris (Roxb.) Burtt et Hill, in comparison to wild grass, were investigated for pH distribution in the soil profile, exchangeable acidity, and cation status in the soil leachate of a simulated leaching experiment. Soils were sampled in profiles at 5 cm intervals to a depth of 100 cm. In the 1.5-60 cm layer the soils with 10-year old C. axillaris had significantly lower pH (P < 0.05), with the largest difference being 0.41: and in the 25-75 cm soil depths, especially in the 30-55 cm layer, the soils had a significantly higher exchangeable acidity, ranging 1.93 to 3.02 cmol(c) kg(-1). There was also higher aluminum, potassium, and sodium contents in the soil leachate under C. axillaris than with wild grasses. This suggested that the growth of C. axillaris accelerated acidification of Udic Ferrosols and promoted soil clay mineral weathering.