Reply: Dear David,
We are finding that whales are a good indicator of the health of the seas.
Whales (especially toothed whales such as sperm or killer whales) are top
order predators, meaning that they eat the large fish which eat the smaller
fish and so on down the food chain to the primary producers. In all, they
top about seven levels of prey items, as do humans. The oceans have been
contaminated by human-created chemicals. Because these chemicals are not
found in nature, animals have not had time to adapt to break them down.
Instead, they accumulate in the fats of animals. When a predator eats a
prey item, it ingests all of the toxins that that animal has ingested
through its lifetime. It is estimated that the levels of toxins in animals
increases tenfold for every step in the food chain, so a whale (or human)
eating at the top can ingest 10 million times the toxins that the first
animal ingested. These chemicals are also passed from mammal mother to
child through the fats in her milk, so young animals start out in life with
approximately the same level of toxins in their bodies as their mothers
had. In the US, we consider anything with 50 parts per million of
organohalogens to be toxic waste. Beluga whales in the St. Lawrence river
have been found with 6900 parts per million in their bodies and must be
disposed of carefully.
As we learn more about whales, we also learn more about our oceans and the
threats we humans are posing to life in the oceans and to ourselves.
Also look at http://whale.wheelock.edu/whalenet-stuff/ed_resources.html#biblio
Thank you for your question!
Question: Would it be possible for you to tell me in as much detail as
possible, how heavy metals, such as mercury and lead can harm aquatic life,
such as zoo plankton and other organisms? I would be very grateful if you
could, as I'm doing a project in school, and I need to use IT and seek an
Whale Conservation Institute/Ocean Alliance
191 Weston Road, Lincoln, MA
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