Nielsen Line Winkel, Dahllöf Ingela
Department of Marine Ecology, National Environmental Research Institute, 4000 Roskilde, Denmark.
Aquat Toxicol. 2007 Apr 20;82(1):47-54. doi: 10.1016/j.aquatox.2007.01.004. Epub 2007 Jan 30.
Eelgrass beds are important habitats for many organisms, but there has been a decline in the area covered by eelgrass during the last decades due to increased eutrophication resulting in increased shading from phytoplankton. The use of herbicides in terrestrial agriculture has also increased over the last century, and while the effects of herbicides on non-target organisms have been well studied in freshwater they are overlooked in coastal waters. It is not known if herbicides have any effect on the distribution of eelgrass (Zostera marina), or how natural phytoplankton communities respond to the same herbicides. Direct and indirect effects of the herbicides Glyphosate, Bentazone and MCPA both as single toxicants and as mixtures, on the eelgrass plants were investigated in this study. The direct effects on eelgrass were examined by measuring the four different endpoints; the relatively growth rate as length and weight, the chlorophyll a and b ratio, as well as the RNA-DNA ratio, at the end of a 3 days exposure period. The indirect effect was investigated by measuring the effect on a natural phytoplankton production from Roskilde Fjord six times during 1 year. The results showed that the chlorophyll a-b and RNA-DNA ratios were the most sensitive endpoints in single herbicide experiments. The effects of herbicide mixtures on eelgrass were much larger compared to the single substances. Nearly a halving was found for both the relatively growth rate in length and weight, and the RNA-DNA as well as the chlorophyll a-b ratios were also significant reduced. This indicates a possible synergistic effect, and calculations based on the concentration addition model indicate that the low concentrations mixture has a synergistic effect, whereas the high concentration mixture has an antagonistic effect on eelgrass (Z. marina). The low concentrations mixture is the one with the highest relevance for coastal areas. The effect on phytoplankton showed some variation over the year but mainly in a stimulation in primary production. This means that herbicides affect eelgrass both directly and indirectly.
鳗草床是许多生物的重要栖息地，但在过去几十年中，由于富营养化加剧导致浮游植物遮荫增加，鳗草覆盖面积有所减少。上个世纪，陆地农业中除草剂的使用也有所增加，虽然除草剂对非目标生物的影响在淡水中已得到充分研究，但在沿海水域却被忽视了。目前尚不清楚除草剂是否对鳗草（大叶藻）的分布有任何影响，也不清楚天然浮游植物群落对这些除草剂会有怎样的反应。本研究调查了除草剂草甘膦、灭草松和2-甲基-4-氯苯氧乙酸作为单一毒物以及混合物对鳗草植物的直接和间接影响。通过测量四个不同的终点指标来研究对鳗草的直接影响；在3天暴露期结束时，测量长度和重量的相对生长率、叶绿素a和b的比例以及RNA与DNA的比例。通过在1年中6次测量对罗斯基勒峡湾天然浮游植物产量的影响来研究间接影响。结果表明，在单一除草剂实验中，叶绿素a - b比例和RNA - DNA比例是最敏感的终点指标。与单一物质相比，除草剂混合物对鳗草的影响要大得多。发现长度和重量的相对生长率以及RNA - DNA比例和叶绿素a - b比例都显著降低了近一半。这表明可能存在协同效应，基于浓度相加模型的计算表明，低浓度混合物对鳗草（大叶藻）有协同效应，而高浓度混合物有拮抗效应。低浓度混合物与沿海地区最为相关。对浮游植物的影响在一年中有所变化，但主要是刺激初级生产。这意味着除草剂对鳗草既有直接影响也有间接影响。
