All Along the Outfall

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Posted by Merry on November 19, 2013 at 15:26:13:

I felt a little guilty asking Phil to take us to the White Point outfall pipe again. A boulder-buttressed, sand-flanked sewer pipe with a few strands of scraggy kelp doesnít promise a stellar underwater experience. It turned out to be a good call.

Off White Point, San Pedro CA, two reinforced, spun concrete pipes carry L.A. County Sanitation Districtís treated wastewater into the ocean on a daily basis. Lying between the main pipes is a double-barrel pipeline that extends to about 1 mile offshore. One leg serves hydraulic relief during heavy rains; the other leg is standby.

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Taken from Physical and Chemical Oceanography at White Point by J. Stein

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The western-most pipe is 8-ft in diameter and has been in operation since 1957. This is the conduit by which Montrose Chemical Corporation dumped an estimated 2,000 tons of DDT onto the Palos Verdes Shelf. The environmental calamity was enhanced by other sources with the introduction of PCBs and other industrial wastes into the sanitation system.

The eastern-most pipe is the one we dove. Ten feet in diameter, it has the most relief. Completed in 1967, it extends 2.25 miles offshore and empties in ~200 fsw.

We dropped anchor in 65-70 fsw. Given that it was a little dark and a little silty, the tangle of rocks and algae was bursting with some of our favorite photo subjects. Even better, the adjacent seabed tantalized us with a bonanza of newly deposited, glistening, squid egg cases. In some, development was far enough along that the embryos could be seen. Note the tear-shaped yolk sac and the faint red iris of the eyes (tighter shots).

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Kelp tops supported dense aggregations of the lion nudibranch, Melibe leonina, which was feeding on drifting invertebrates.

 photo MelibeleoninaDSC_3442_zps1d4e3518.jpg

Juvenile Polycera atra feeding and laying eggs on the bryozoan-covered kelp.

 photo PolyceraatrababyDSC_3562_zps39798846.jpg

 photo PolyceraatrababyDSC_3582_zpscd6ab910.jpg

Juvenile Triopha maculata, ditto.

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Bluering topsnail

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During construction of the outfall, boulders were piled around the pipe to prevent scour caused by ocean currents. These rocks also provide rich habitat for many species.

Phil spotted this cabezon guarding 2 nests of eggs.

 photo Cabezonampeggs800DSC_3531_zps43c40a6a.jpg

 photo CabezonwitheggsimplightDSC_3488_zps5636510c.jpg

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On one nest, larval fish had begun to escape their confines and begin their tenuous life in the plankton.

 photo CabezoneggsemptyDSC_3544_zps908ecab2.jpg

Sea slugs abound:

Peltodoris nobilis
 photo PeltodorisnobilisDSC_3476_zps23dfe212.jpg

Acanthodoris hudsoni
 photo Acanthodorishudsoni800DSC_3367_zps9e94680a.jpg

One of my favorites, Acanthodoris lutea
 photo AcanthodorisluteaDSC_3474_zps68459ed0.jpg

The uncommon Felimida macfarlandi
 photo Felimidamacfarlandi6802DSC_3405_zps0ebcb1ff.jpg

 photo PeltodorisnobilismatingDSC_3484_zps72fbc115.jpg

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