Kelp at Casino Point - how long will it take to return?

[Lee Coller]

I'd seen the reports that the kelp was disappearing at Casino Point due to both warm water and the high seas that blew through last month. I just did my first dive there in a couple months with two OW students. The kelp is completely gone. It seemed really weird without it.

Once the temperature of the water cools down how long will it take for the kelp to recover?

 

[drbill]

It depends on a number of things. First, the causes. Elevated water temperatures above 68 F for a period of weeks cause nutrient levels to plummet thus impacting kelp growth and strength. Storm surge from Hurricane Marie and her kin was able to rip out the weakened kelp (and a lot of the healthy ones as well). Note that the only reasonably healthy kelp in the dive park is down at the harbor end where colder water from the submarine canyon off the harbor replenishes nutrients to some degree at that end and the deeper adjacent water probably lessens the impact of the storm surge somewhat.

Over the last 8 years (following the appearance of the Asian invasive alga Sargassum horneri), when we have warm water episodes like this and the giant kelp is decimated, the Sargassum tends to grow in early and very thick further restricting the recovery of the giant kelp both by overshading the young sporophytes growing up from the reef as well as by ripping off the blades of the young kelp sporophytes as they try to grow up through the bed of Sargassum.

During some of the recent warm water events the Sargassum has so dominated the reefs that giant kelp has had a hard time making a comeback even when temperatures drop and nutrients increase.

It will be interesting to see how this interplay of natural events (warm water) and "unnatural" ones (the introduction of the Sargassum from Japan on a ship's hull). I am working with a group of Japanese scientists who will be out here next month. This is one question we will be looking at. In its native habitat in Asia, the Sargassum horneri is in decline which is of economic consequence to those cultures.

 

[davidbaraff]

Are we saying there is just totally zero kelp in the dive park? I'm (hopefully) going to be there on Friday. That would be a bit disappointing...

 

[drbill]

The area at the south end of the dive park near the harbor mouth does have some kelp left but in most areas it has been decimated and you only see a few straglers

 

[descent]

Volunteers sometimes restore damaged environments. They replant hillsides after fires to stabilize the soil. They chop down invasive plants like fennel on Catalina Island. They rip out non-native seaweed species in our harbors.

Should there be a system of restoration for damaged kelp forests, similar to what we already do for forests on dry land?

As divers, could we help to do this?

 

[red_instead]

Volunteers sometimes restore damaged environments. They replant hillsides after fires to stabilize the soil. They chop down invasive plants like fennel on Catalina Island. They rip out non-native seaweed species in our harbors.

Should there be a system of restoration for damaged kelp forests, similar to what we already do for forests on dry land?

As divers, could we help to do this?

I think Santa Monica Baykeeper is doing that in Santa Monica Bay.

Would probably need some kind of environmental review for a concerted effort. Plus approval of CDFW. Casino Point being an MPA might also complicate things.

 

[undrwater]

The waters not being suitable for the organism might complicate matters more.

 

[Steve_C]

How about the Kelp beds at Pt. Loma off San Diego? Anybody know what shape they are in? Supposed to dive them in a few days.

Slated to dive Casino in Dec. Hopefully a bit recovered by then but if not we will see what we will see. Always interesting stuff in the ocean.

 

[drbill]

I don't think there is any need to attempt human mediated restoration of the kelp beds. There are natural water temperature fluctuations like this every decade and the kelp recovers, sometimes even healthier than it was before. Any attempt at restoration under the prevailing water conditions would not likely succeed due to the low nutrient levels associated with the elevated water temperatures.

The one thing that humans could do to lessen the impacts on our native giant kelp (Macrocystis pyrifera) would be to remove as much of the invasive Asian Sargassum horneri as possible. It will over-shadow the recovering giant kelp this fall and quite possible form tall (15-20 ft) forests itself that totally over-shade native species and suck available nutrients out of the water that the natives would otherwise use. However, the Invasive Species section of the California Dept. of Fish & Wildlife has imposed what I feel are ridiculous constraints on us doing that... while doing absolutely NOTHING itself despite warnings from scientists since 2003.

One of the fundamental issues I see is modifying the MLPA so that it allows the removal of NON-NATIVE invasive species from MPAs. Currently it apparently makes no distinction between them and native species, and thus imposes unreasonable limitations on controlling non-native species in MPAs.

 

[CAPTAIN SINBAD]

Interesting and informative. I am wondering how long does it take for Kelp to grow to over 50 feet? Is it possible to plant kelp in areas where environment may be favorable? Has this happened anywhere?