Influence of barley straw and submerged macrophytes on fishpond wastewater quality
MetadataShow full item record
Barley straw has received, recently, considerable attention as an algicide, which could be used to control algal growth in fishponds. It is regarded as cost-effective, user friendly and environmentally sounds. On the other hand, the submerged wetland macrophytes are crucial for the stabilization of clear water state in shallow lakes, by their active production of anti-algal compounds (allelochemicals) through allelopathy. Microcosm experiments using barley straw and the submerged macrophytes: Najas marina L., Potamogeton pectinatus L. and Ceratophyllum demersum L. in culture media with fishpond water were carried out outdoors to simulate the situation as natural as possible. Nutrients concentrations were measured beside the analysis of phytoplankton and zooplankton communities were analyzed during nineteen days incubation period. Nitrogen and phosphorus elements were determined in the tissues of used aquatic macrophytes at the beginning and by the end of the experiment. Multivariate statistical assessment using matrix correlation and principal components analysis was applied for interpretation of the experimental data. Principal component PC1 in barley straw medium accounted for about 47% of the total variance with strong correlation between selected parameters and a positive coefficient (r = 0.94 and 0.84) for diatoms – PO4 and diatoms – SiO4 respectively. On the other hand, PC1 in the status of N. marina and C. demersum contributed to 46% and 58% of the total variance, respectively with high positive loading between diatoms and green algae, while in case of P. pectinatus PC1 accounted for 62% of the variance with positive loading for chlorophyll – a, green algae and rotifers. Thus, rotted barley straw stimulated the growth and dominance of diatoms, rather than the green algae, throughout the incubation period. In the mean time, the macrophytes had allelopathic impact on the diatoms community, particularly Najas, while stimulated growth of the green algae. Zooplankton community was dominated by rotifers in all macrophytes media, while protozoan dominated barley straw medium. Complete depletion of nutrients was detected after few days in all media, while oxygen sustained acceptable levels. Phytoplankton assemblages shifting from green algae dominance to diatoms in barley straw medium is recommended as an invention to provide an integrated bioremediative product with readyto-use. Active biological compounds (algicides) derived from barley straw were more reliable than allelochemicals from aquatic macrophytes. Through their beneficial effects they would render aquatic environments such as, ponds, lagoons, aquaria, aquaculture systems, wastewater treatment, holding or conveying systems more aesthetically pleasing, efficient in aquatic animal production, and less susceptible to algae and other undesirable aquatic plants. They would thus require less maintenance. It is a tentative suggestion to use barley straw for field manipulation experiments.