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Urban Runoff along the Palos Verdes Coast Negatively Impacts Diatom Diversity and Density, Impacts the Marine Ecosystem.

Posted by M Warner | California, United States

Numerous discharge pipes and spillways deliver wastewater from the communities constructed above the cliffs of Palos Verdes peninsula directly – and intentionally -- into the Pacific Ocean. Despite the area receiving little rain, pipes may flow rapidly year-round, fed by the day-to-day activities of the communities above. We studied the water quality and diatom assemblages in areas directly in the path of these pipes’ effluence.

Diatoms are single-celled, microscopic organisms and, as such, may seem inconsequential. However, they are the “plants” of the ocean. At the beginning of the marine food chain, their well-being affects every other organism up the chain. Species of diatoms are highly sensitive – so they perish -- or tolerant – so they thrive -- to environmental imbalances, such as water pollution. Three-quarters of the sea lions being treated at the Marine Mammal Center suffer from DA poisoning – a toxic compound produced by a pollution-tolerant species of diatoms. This is offered to demonstrate, not only the impact these unicellular organisms may have upon the marine ecosystem, but also the far-reaching, destructive effects of water pollution.

We consistently found a decrease in diatom species diversity at locations in the path of the pipes’ discharge (roughly 7, to 17 outside the discharge area) due to an excess of elements in the water known to be detrimental to their growth. Even those thriving species recognized as more tolerant of such pollution showed deformities. This suggests that all species of diatoms in these areas are endangered by the output of these pipes.

It’s very obvious, simply by sight, that diatom (and other algal) growth explodes on the rocks in the path of these pipes. To witness for yourself, visit a site just right of the Palos Verdes Beach and Athletic Club (parking’s free). There’s a paved path down just to the north of the Club. The rapidly running “river” you’re walking along as you move toward the shore carries urban waste. On the shore, you’ll see an abundant growth of brilliant green surf grass. But you’ll see it nowhere else. And you’ll see an abundance of diatom growth (the black, brown patches on the rocks), but you’ll see it nowhere else. What you won’t see, simply by sight, is those black patches contain only a few species of diatoms, while elsewhere, their variety is seemingly limitless. Biodiversity is paramount to this organism’s survival, and by extension, its habitat's.

How could we, in such an enlightened age, construct these spillways without regard to the impact their discharge would have upon their delivery site? Now that we know, what will we do?

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