Dead fish and birds in <a href="//commons.wikimedia.org/wiki/Bonn" title="Bonn">Bonn</a>. In summer 2018, around 400 dead animals were removed from the <a href="https://de.wikipedia.org/wiki/Rheinaue_(Bonn)" class="extiw" title="de:Rheinaue (Bonn)">Rheinauesee</a>.
<dl><dd>Favored by the low water depth (0.5 to three meters), the lack of running water, an increased production of organic deposits and other factors, there is a significant reduction in the oxygen content in longer, sunny periods, which leads to the death of a part of the fish. The formation of <a href="https://en.wikipedia.org/wiki/Sapropel" class="extiw" title="en:Sapropel">sapropel</a> at the bottom of the lake can be associated with the formation of toxins such as <a href="https://en.wikipedia.org/wiki/Botulinum_toxin" class="extiw" title="en:Botulinum toxin">botulinum toxin</a>, which can cause the death of waterfowl. Also the feeding of the animals by park visitors and the thereby increased propagation contaminated the lake by the feces of the large bird population. All factors together, the lake may reach the <a href="https://en.wikipedia.org/wiki/Dead_zone_(ecology)" class="extiw" title="en:Dead zone (ecology)">tipping point</a>.</dd></dl>
<p><a href="//commons.wikimedia.org/wiki/User:Spielvogel" title="User:Spielvogel">Spielvogel</a>
</p>
<dl><dd>For a gallery of some more of my uploaded pictures see: <a href="//commons.wikimedia.org/wiki/User:Spielvogel" title="User:Spielvogel">here</a>.</dd></dl>
<span class="int-own-work" lang="en">Own work</span>