Silver is commonly used in clothes, cosmetics, pharmaceutical products as well as water refinement products these days. With the increased usage of silver there is an increased risk that the amount of silver in nature raises and that it affects ecosystems. Aquatic ecosystems have shown to be sensitive to the toxic effects of the silver. The bladderwrack (Fucus vesiculosus) is one of the most important species in the Baltic Sea and is of major importance for the survival of other species. The purpose of the study is to increase the knowledge of colloidal silver toxic effects on the bladderwrack. This study measures the stress level and leakage of pigment of the bladderwrack which has been exposed to different levels of colloidal silver. The study was conducted at Askö laboratory during the period 19/4 to 25/4 -2017. The results show that colloidal silver has a significant stressful effect on bladderwrack, especially at the higher levels. During a period of three days, significant values of the higher concentration, was found over three consecutive measurement events. Thereafter the bladderwrack recovers. A second study of two and a half days shows two significant values in succession, with a subsequent weak rejuvenation at higher levels. The study also shows that the stress level varies over time. Measures on the water that the bladderwrak laid in during the stress measurements showed that the bladderwrack released more dye, the higher the concentration of colloidal silver to which they were exposed. Despite the low sample size, the bladderwrack shows signs of stress but after multiple test corrections the values ​​were not significant. The Baltic Sea has aggravating factors such as slow water exchange, low salinity and a lot of pollution. Resistance is low. The bladderwrack is a structurally important species in the Baltic Sea ecosystem. If larger colloidal silver is released due to increased use, there is a risk that the bladderwrack may be stressed.