The Occurrence and Prevention of Filamentous Algae in Ecological Purification System of Micro-polluted Water

[ Objective ] The aim was to study the influence of filamentous algae on the process of water ecological purification. [ Method ] The occurrence mechanism of filamentous algae and its ecological system were summarized and analyzed. Considering the ecological purification in north- ern Jiangsu, the occurrence and prevention of filamentous algae in water, the method to prevent filamentous algae in polluted water was discussed. [ Result] The results showed that by measures of improving planting density, regular harvesting, and water flow state control before the filamentous algae blooming period, together with improving local pH value, light interference and ecological control during the blooming period, can effectively control the filamentous algae blooming. [ Condusion] The study of the happening mechanism of filamentous algae provided theoretical references and the technical basis in the work of filamentous algae prevention and control.

Filamentous Green Algae Reduce Walleye Fingerling Production in Earthen-Substrate Ponds

Reduced walleye (Sander vitreus) fingerling production possibly related to nuisance filamentous green algae and overly stable water chemistry patterns is a concern in earthen-substrate ponds at Blue Dog State Fish Hatchery, South Dakota, USA. We describe the success of alfalfa (Medicago sativa) meal (AFM, n = 2), alfalfa meal plus soybean (Glycine max) meal (AFM + SBM, n = 1), and alfalfa meal plus liquid 28N:0P:0K (AFM + 28:0:0, n = 1) at achieving walleye production objectives (>104,000 walleye and 32 kilograms/hectare) as well as the occurrence of filamentous green algae and the associated patterns of ammonia-nitrogen, pH, and dissolved oxygen in earthen-substrate ponds. Walleye production objectives were only achieved when filamentous green algae were absent preceding harvest, which occurred in one pond that received AFM and in the pond that received AFM + 28:0:0. The presence of filamentous green algae preceding harvest was associated with higher dissolved oxygen and pH, whereas declines in these variables occurred when filamentous green algae were absent. Organic fertilizer alone exhibited low ammonia-nitrogen (<0.1 mg/L) despite the substitution of higher protein content soybean meal, but supplementation with 28:0:0 increased ammonia-nitrogen to 0.23 mg/L. These findings highlight the reduction in walleye fingerling production that occurred in the presence of filamentous green algae and the unpredictability of results when two earthen-substrate ponds are treated exactly the same with alfalfa meal. Achievement of walleye production objectives, lack of nuisance filamentous green algae, and promotion of favorable patterns in water chemistry warrant future experimentation with alfalfa meal supplemented with 28:0:0 in earthen-substrate ponds at this hatchery.

Analysis of expressed sequence tags from the Ulva prolifera (Chlorophyta)

In 2008, a green tide broke out before the sailing competition of the 29th Olympic Games in Qingdao. The causative species was determined to be Enteromorpha prolifera （Ulva prolifera O. F. Miiller）, a familiar green macroalga along the coastline of China. Rapid accumulation of a large biomass of floating U. prolifera prompted research on different aspects of this species. In this study, we constructed a nonnormalized cDNA library from the thalli of U. prolifera and acquired 10072 high-quality expressed sequence tags （ESTs）. These ESTs were assembled into 3 519 nonredundant gene groups, including 1 446 clusters and 2 073 singletons. After annotation with the nr database, a large number of genes were found to be related with chloroplast and ribosomal protein, GO functional classification showed 1 418 ESTs participated in photosynthesis and 1 359 ESTs were responsible for the generation of precursor metabolites and energy. In addition, rather comprehensive carbon fixation pathways were found in U. prolifera using KEGG. Some stress-related and signal transduction-related genes were also found in this study. All the evidences displayed that U. prolifera had substance and energy foundation for the intense photosynthesis and the rapid proliferation. Phylogenetic analysis of cytochrome c oxidase subunit I revealed that this green-tide causative species is most closely affiliated to Pseudendoclonium akinetum （Ulvophyceae）.

Freshwater snail and shrimp differentially affect water turbidity and benthic primary producers

Benthic macroinvertebrates play key roles in shallow aquatic ecosystems and can contribute substantially to aquatic food webs.However,how macroinvertebrates with different behaviors(for example,pertaining to locomotion,foraging and burrowing)impact water quality and primary producers has not been fully explored.Here,we performed two consecutive microcosm experiments to test the effects of(1)macroinvertebrates with different behaviors(a low mobility scraper aquatic snail Bellamya aeruginosa and a high mobility shredder freshwater shrimp Macrobrachium nipponense)and(2)different shrimp biomasses on water clarity and the composition of benthic primary producers.The results showed that presence of snails significantly increased the biomass of filamentous green algae and decreased the biomass of periphyton.In contrast,presence of shrimp significantly decreased the biomass of filamentous green algae and increased the biomass of periphyton,and these effects were biomass dependent.Filamentous green algae disappeared when shrimp biomass reached 9.8 g m^(-2).No interactive effects of snail and shrimp presence were found.This could be attributed to different food preferences by the two consumers,with snails preferring periphyton(mainly diatoms)and shrimp preferring filamentous green algae.The presence of snails decreased water turbidity,while shrimp increased water turbidity,which showed a hump-shaped response to shrimp biomass with a peak at 24.2 g m^(-2).These results are likely because the snail is a low mobility grazer and can filter suspended particles,while the shrimp is a high mobility shredder with burrows,which can strongly disturb sediment.The decrease in water disturbance at high shrimp biomass might be due to food limitation,thus reducing burrowing and foraging activities.Neither snail nor shrimp affected the biomass of H.verticillata,while the biomass of V.spinulosa increased with shrimp biomass.The reason for this could be that shrimp increased nutrient availability and decreased the growth of filamentous green algae that compete with macrophytes.Our study demonstrated that different macroinvertebrates have complementary functions in benthic habitats;thus,maintaining macroinvertebrate diversity is important for shallow aquatic ecosystems.Furthermore,the freshwater shrimp M.nipponense could be a potential consumer to control filamentous green algal blooms in its native range,but their biomass should be taken into consideration.