摘要
波罗的海的大部分正在进行着富养化过程。本文记录了芬兰周围公海海域内几种与富养化有关的变量在最近几十年中的变化(冬季养分浓度、冬季养分比例和夏季表水叶绿素α浓度)。从20世纪60年代到80或90年代,波罗的海本体北部和芬兰湾内硝态氮和亚硝态氮的总和([NO_3+NO_2]-N)增加了近4倍,波的尼亚海内增加了约两倍。增加之后就是减少,在前两个子区域内下降不大。磷酸盐-磷(PO_4-P)浓度在波罗的海本体北部(增加3倍,后有轻微下降)和波的尼亚海(增加30%,后有轻微下降)呈现出相似的模式,但在整个研究中芬兰湾的浓度都是增加的,目前的浓度是20世纪70年代初期测量值的3倍。波的尼亚湾在整个研究中PO_4-P浓度都是下降的。从20世纪70年代初期到90年代后期,波罗的海本体北部、芬兰湾和波的尼亚海内硅酸盐-硅(SiO_4-Si)浓度下降了30%～50%,其后又增加了20%～40%。从20世纪70年代到21世纪初,波罗的海本体北部和芬兰湾内叶绿素α的增加超过150%。在波的尼亚海,从20世纪70年代后期到90年代后期,叶绿素α浓度的增加超过180%,其后下降。根据这些长期观测,芬兰湾和波罗的海本体北部表现出明显的富养化迹象,并被那些影响浮游植物群落并由此影响海藻生物量的水文地理变化加剧。
Eutrophication is an ongoing process in most parts of the Baltic Sea.This article reports on the changes during recent decades of several eutrophication-related variables in the open sea areas surrounding Finland (wintertime nutrient concentrations,wintertime nutrient ratios, and summer time chlorophyll a concentrations at the surface).The sum of nitrate- and nitrite-nitrogen ([NO_3+NO_2]-N) was observed to increase nearly fourfold in the Northern Baltic Proper and the Gulf of Finland and almost double in the Bothnian Sea from the 1960s until the 1980s or 1990s.The increase was followed by a decrease,which was modest in the two former subregions.Phosphate-phosphorus (PO_4-P) concentrations followed a similar pattern in the Northern Baltic Proper (threefold increase and subsequent slight decrease) and Bothnian Sea (30% increase and subsequent decrease),but increased throughout the study in the Gulf of Finland,with the present concentration being threefold to the measurements made in the early 1970s.The PO4-Pconcentration decreased throughout the study in the Bothnian Bay.Silicate-silicon (SiO_4-Si) concentrations decreased 30-50% from the early 1970s to the late 1990s and increased 20-40% thereafter in the Northern Baltic Proper,the Gulf of Finland,and the Bothnian Sea.Chlorophyll a showed an increase of over 150% in the Northern Baltic Proper and the Gulf of Finland from the 1970s until the early 2000s.In the Bothnian Sea the chlorophyll a concentration increased more than 180% from the late 1970s until the late 1990s,and decreased thereafter.According to these long-term observations,the Gulf of Finland and Northern Baltic Proper show clear signs of eutrophication,which may be emphasized by hydrographical changes affecting the phytoplankton communities and thus the algal biomass.
