Guanabara Bay, the second largest bay on the Brazilian coast, has tropical to subtropical, hypereutrophic water conditions. A survey of the macroalgae flora conducted over the past 200 years (1800–2013) yielded a list of 245 species, which represents 15.7% of the total macroalgae recorded in the Tropical Western Atlantic, while comprehends 29.9% and 50.2% of the marine flora in Brazil and Rio de Janeiro, respectively. When evaluating the macroalgal list throughout different periods, it is noticeable the gradual loss of biodiversity as anthropization increased over the last two centuries. The use of phytogeographic indexes and beta diversity confirmed the negative changes in macroalgae assemblages as a response to increasing environmental degradation. The use of floristic surveys to establish the reference conditions employing historical data and/or regionally referenced prove to be an efficient tool using macroalgae as an ecological indicator for water quality.

瓜纳巴拉湾是巴西海岸的第二大海湾，拥有热带至亚热带的富营养化水质。在过去200年（1800-2013年）内对大型藻类植物群进行的一项调查得出了245种物种的清单，占热带西大西洋记录的大型藻类总数的15.7％，而其中包括29.9％和50.2％的海洋菌群。分别在巴西和里约热内卢。在评估不同时期的大型藻类清单时，值得注意的是，在过去的两个世纪中，随着人类活动的增加，生物多样性逐渐丧失。植物地理指数和β多样性的使用证实了大型藻类组合的消极变化是对日益严重的环境退化的反应。