底栖藻对水丝蚓生物扰动效应的抑制研究

Inhibiting effect of benthic algae on the bioturbation of Limnodrilus hoffmeisteri

霍甫水丝蚓(Limnodrilus hoffmeisteri)是富营养化湖泊中的底栖动物优势种,通过生物扰动可以提高水体营养盐浓度,并促进浮游植物生长.富营养浅水湖泊经生态修复后,水体透明度会得到改善,有利于底栖藻快速生长,从而降低水体营养盐水平.那么,底栖藻能否抑制水丝蚓对富营养水体水质的不良影响?为此,本文开展了双因素(底栖藻和水丝蚓)的室外受控实验,结果表明:在无底栖藻处理中,水丝蚓显著提高了水体总氮(TN)、总磷(TP)、总溶解磷(TDP)和叶绿素a(Chl-a)浓度,同时显著降低水体溶解氧(DO)浓度;而在有底栖藻处理中,水丝蚓对水体TP、DO及Chl-a浓度的影响不显著.研究结果表明,水丝蚓的生物扰动提高了水体营养盐和浮游植物浓度,促进水体富营养化.但底栖藻群落的发展能在一定程度上抑制水丝蚓的生物扰动效应.

Limnodrilus hoffmeisteri is the dominant species of zoobenthos in the eutrophic lakes which could increase the nutrient concentration in the water though the bioturbation, meanwhile stimulate the growth of phytoplankton. After the implementation of ecological restoration project in the shallow eutrophic lake, the benthic algae will grow quickly due to the improvement of water transparency, resulting the decrease of nutrient concentration in the water because of the growth of the benthic algae. To explore whether the benthic algae could inhibit the negative effect of L. hoffmeisteri on the eutrophic water quality, a outdoor mesocosm was set up which include two-factors （L. hoffmeisteri and benthic algae）. The results show that L. hoffmeisteri could increase the concentration of total nitrogen, total phosphorus, total dissolved phosphorus and Chl-a in water column remarkably when the benthic algae was absent. Furthermore, L. hoffmeisteri could decrease the concentration of dissolved oxygen remarkably. However, the L. hoffmeisteri did not show a significant effect on the total phosphorus, dissolved oxygen and Chl-a in water column when the benthic alage was present. This study shows that the bioturbation of L. hoffmeisteri could increase the concentration of both nutrient and phytoplankton in the water, which may promote the eutrophication.However, the development of benthic algae community could exert inhibiting effect on the bioturbation of L. hoffmeisteri.