Both Russia and Ukraine have accused each other of blowing up the dam.
Ukraine on Tuesday said 150 tonnes of engine oil had spilled into the Dnipro River after an attack on the Kakhovka dam and warned of a "negative impact" for the environment.
"One hundred fifty tonnes of engine oil got into the Dnipro River due to the explosion," Daria Zarivna, communications adviser to the head of the Ukrainian president's office, said on social media.
Ukrainian President Volodymyr Zelensky said there was "a risk of further leakage of more than 300 tons."
Upstream from the dam is the Kakhovka reservoir, which holds an estimated 18 cubic kilometres of water -- approximately the same capacity as Utah's Great Salt Lake.
Ukrainian Foreign Minister Dmytro Kuleba said the floods from the dam could cause "long and irreversible harm" to the region's ecosystems.
"Animals in the Nova Kakhovka zoo have already died in the rising water," he said, adding it was "only the beginning of harm" for the wildlife in southern Ukraine.
"We are witnessing (an) ecocide on a regional, not just Ukrainian, scale," he added.
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