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Touring Malibu Lagoon with Matthew Horns 5/19/12

May 24, 2012

NOTE:  Matthew is leading one more lagoon walk this coming Saturday, May 26 at 1 P.M.  Lagoon reconfiguration is scheduled to start June 1.

State Parks Lagoon Restoration Plot Map

Our first major stop around the lagoon perimeter was midway down the west side of west channel, next to the depth gauge.  The number scale on the lower portion of the gauge is covered by an encrustation of barnacles and ‘crud.’  Inside there is a device to record salinity, but we didn’t have access to it.  Amid much discussion – Jane and I on birds, Matthew on water – he measured the dissolved oxygen level at about 130%.  This seemed high to me.

Matthew explained:   The lagoon channel is currently open and we were at high tide, so the channels were full of ocean water, which is highly oxygenated from ocean turbulence.  Plus there were ocean diatoms (single-celled photosynthesizing organisms) busily converting carbon dioxide into food and oxygen, thus raising the oxygen level even higher.  The diatoms were so numerous they turned the water a murky brown.  Both these factors raise the oxygen levels well above what we get at low water.  Unfortunately, the lagoon is closed to the ocean from  1/3rd to 1/2 of the year, primarily in the summer, preventing tidal inflows.

We saw numerous chunks of giant kelp leaves, washed in on the tide, floating in the usual surface detritus of wood pieces, innumerable bits of plastic and a pair of flip-flops.  There were two dead pelicans: one completely submerged in west channel, one on the middle channel shore.

We took the next measurement out on the lagoon’s beach edge; results were about the same for the same reasons.  I counted about 150 Brown Pelicans and at least as many gulls on the nearby sand islands.  Elegant Terns flew above the lagoon, calling horsely.  I told Matthew about the reasoning behind the virtual fence enclosure for the Snowy Plovers:  in a nutshell, to provide them a human-free area where they can get some shut-eye during the 12-16 hours out of 24 hours they aren’t actively feeding.  Unfortunately someone had swiped about half of the rope linking the fence posts.

A close look at the “cliff” of dirt at the west end of the beach showed that it was all landfill, as the bottom of it consisted of chunks of concrete and asphalt.   Floating in the nearby detritus we found a blue egg, no doubt belonging to a Styrofoam Gull (see picture).

Blue egg of the Styofoam Gull with handy carrying loop; land fill and concrete behind. (J. Beseda 5/19/12)

We discussed dirt.  Matthew told us:  In the years since the 1983 lagoon project, soil has been developing on top of the remaining fill.  Three general habitat types exist at the lagoon; aquatic, inter-tidal, and upland.  In each of these habitats, unique physical characteristics develop within the soil.  Also, equally important, unique biological communities of invertebrates, microorganisms, and other life forms become established.  At the onset of grading operations, the top one-foot-deep layer of soil will be excavated from each habitat type and the soil will be stored in separate piles.  At the close of grading operations, this soil will be re-spread over the ground surface in appropriate locations.  This should “jump start” the process of natural ecosystem development after the project is completed.

The oxygen measurements we took from the middle of each footbridge again yielded about the same results for the same reasons.  By this time, several hours had passed – most of it in conversation. Tide was falling; water flowed out of the lagoon and channels.

Bob Purvey brought his video camera and struggled to get good angles for a film.  When it’s available we’ll provide a link to it so you can see us in action. (Inaction?)  Matthew is leading one more lagoon walk this coming Saturday, 1 PM, May 26.  Lagoon reconfiguration is scheduled to start June 1.  The lagoon will remain open to foot traffic, and we expect to continue our SMBAS 4th-Sunday-of-the-Month 8:30 AM birdwalks.  The parking lot will be closed and we won’t be doing our 10 AM parents & kids walk.

Almdale, Purvey & Horns (J. Beseda 5/19/12)

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