LET’S NOT FORGET ABOUT THE LITTLE THINGS!

By Cindy Hardin, Director of Outdoor Education

Docent training has commenced for Los Angeles Audubon’s Environmental Education programs at the Ballona Wetlands and at Kenneth Hahn State Recreation Area. It’s always a great time of year, as returning docents prepare for another rewarding year of teaching children about the natural environment on-site, and new volunteers learn about the unique ecosystems found at these locations. Of course, both veterans and new recruits experience much excitement when we catch a view of a Red-tailed Hawk soaring on the air currents above, or a Snowy Egret, wiggling its feet in the mudflats in hopes of stirring up a meal.  This “charismatic fauna” is easy to see, and (to me at least!) breathtaking in their appearance. However, as we get carried away with awe in seeing these species right here in the midst of this big city, we may overlook the “little creatures”, whose presence is essential to the very existence of the larger animals.

Harvester-Ant-Hill-by-cindy HardinHarvester-Ant-Closeup-Cindy-hardin

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Harvester Ant Hill and Harvester Ants, Photo by Cindy Hardin

Western Fence Lizard, Photo by Leslie Davidson

These two species are linked by the food chain and geographically. Both photos were taken at the Ballona Wetlands within 50 feet of each other.

I spend a lot of time emphasizing these humble members of the lower levels of the food chain, in hopes of establishing the connectivity of both non-living and living components in any ecosystem. A simple example that is often described to visiting students would be the indigenous Harvester Ant, busily gathering the seeds of our native Buckwheat to bring back to its colony. An encounter with a Western Fence Lizard will not end happily for the ant, but will result in a tasty lunch for the lizard. The lizard’s enjoyment of his repast might be cut short by the predatory King Snake, who in turn will provide a great meal for the soaring Red-tailed Hawk. Take away the Buckwheat, and this chain will be broken, and our chances of sighting the Hawk will diminish. Thanks to the presence of natural habitat and native plantings that were installed and are maintained by LAAS at Kenneth Hahn, students and docents have a chance to witness parts of these segments of the food chain during field trips at the park.

Horn-Snail by-Cindy-hardin

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The California Horn Snail —just a stop along the way in the life cycle of the trematode worm.

A more complex relationship between prey, parasites, and predators is regularly on display at Ballona. The California Horn Snail is easy to see, and in great abundance at the Saltmarsh. Less apparent are the trematodes, a type of flatworm or fluke. The gut of the horn snail is the host for the larvae of the treamatode. The Horn Snail ingests the trematode eggs when it consumes the feces of the snowy egret (remember, the Horn Snail is the clean-up crew of the estuary!). The eggs hatch in the Horn Snail and emerge as larvae. On warm days we can actually see the larvae emerging from the Horn Snail while instructing children at the Microscope Station! Those larvae go on to burrow into the sides of small fish present in the waters. The larvae do not kill the fish, but they do slow them down a bit, making them an easy catch for the Snowy Egret, whose gut is the next stop in the parasites’ life cycle. The larvae mature in the gut of the Egret and lay their eggs, which are then ejected through the digestive system in the feces of the bird. The Horn Snail ingests the eggs, and the cycle continues. Although the larvae do not kill the Horn Snail, the do sterilize the gastropod, which helps to keep their population in check. Horn Snails also eat algae, an important habitat and food source for invertebrates that dwell in the tidal channels. Too many Horn Snails mean a decimation of algae, which would create a negative impact on the invertebrates living in the saltmarsh. Slow-moving fish that have been penetrated by the trematode larvae mean easy pickings for the Snowy Egret, that charismatic bird that everyone enjoys seeing! This system of mutualism is essential in enriching the biodiversity of a saltmarsh.  Up to twenty different species of trematodes have been sighted in Southern California saltmarshes, and scientists have shown that the greater variety of trematodes present is directly linked to the number of bird species at the site.

Kelp-Holdfast by-Cindy-Hardin sml-WEB 

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Remnant of a thriving ecosystem or teaching tool?  Both! This kelp holdfast, found on the beach after monster swells generated by Hurricane Norbert, was a point of discussion during Ballona docent training.

One of the most diverse and abundant ecosystems around can be found right off the coastline here in Southern California. That would be the Giant Kelp Forests. This year, on the first day of training at Ballona, I brought in a Kelp holdfast attached to a rock. The holdfast is the foundation and beginnings of a Kelp forest. The first point I wanted to make was about the rock itself. Kelp is dependent upon the rocky substrate upon which it attaches.  Many of the rocks found on the ocean floor did not originate in the sea. Instead, they were part of the mountain topography found upstream from the ocean. If we dam and channelize our natural streams and rivers, large boulders become trapped upstream, and are unable to reach the sea.  Giant Kelp can live up to seven years, but its survivorship during heavy storms correlates with the hardiness of the substrate to which they are attached. The smaller the rock, the less hardy the substrate; and the modern system of channelizing and damming rivers and streams prevent these larger boulders from descending into the sea, forming a strong substrate.

If a large boulder is present, the Kelp will form its holdfast around that chunk of geological history. A healthy large holdfast is home to thousands of invertebrates. A study that examined five Giant Kelp holdfasts in Monterey Bay found 23,000 individuals from nine different invertebrate phyla. This included polycheate worms, amphipods, decapods, gastropods and ophiuroids. These invertebrates are food for the next level of the food chain found in the Kelp forest. Jellyfish, crustaceans and fish larvae are all found in the water column around the Giant Kelp. These creatures attract larger fish, like rockfish and surfperch, which browse on the crustaceans associated with the fronds and canopies. These smaller fish are in turn a banquet for Harbor Seals, Tuna and Porpoises. The topsmelt and anchovies that lurk near the top of the forest bring in foraging seabirds, like cormorants, Least Terns and Brown Pelicans. A healthy Kelp Forests can also shelter our largest sea mammals. Gray Whales have been observed entering Kelp forests to escape predation from Killer Whales. The whales have also been known to feed on midwater crustacean swarms present in the forest. The growth rate of Kelp in peak season can be up to two feet per day, creating huge amounts of habitat for all of these creatures. Peak season in our local waters is winter time, when water temperatures drop and upwelling of nutrients from colder waters below is more common. Winter winds and storms drive this essential upwelling.

The kelp’s utility and productivity does not end in the water. When the substrate is dislodged from the bottom due to large swells and/or storm activity, parts of the forest wind up on our shores in the form of wrack. Initially, invertebrates trapped in the holdfast are consumed by foraging shorebirds. Then, the kelp flies attracted by the decomposing kelp provide a food source for the Snowy Plover and other insect eating birds, like swallows. Finally, as the kelps completely dries out and crumbles, it is blown or washed back into the sea, bringing nutrients back to its point of origin.

Knowledge and fascination about this incredible ecosystem is not new. Witness Charles Darwin’s thoughts on Kelp, recorded in 1834 as he visited Tierra de Fuego, in Chile:

“I can only compare these great aquatic forests . . . with the terrestrial ones in the intertropical regions. Yet if in any country a forest was destroyed, I do not believe nearly so many species of animals would perish as would here, from the destruction of the Kelp. Amidst the leaves of this plant numerous species of fish live, which nowhere else could find food or shelter; with their destruction the many cormorants and other fishing birds, the otter, seals and porpoise, would soon perish also; and lastly, the Fuegians . . . would . . . decrease in numbers and perhaps cease to exist.”

The rock that started it all for the Kelp Forest is inanimate, and to the casual observer may have little significance. The “little things” are difficult to see, and hardly charismatic to most. But, in all three of the examples above, their presence is essential to the larger creatures that thrill us. The next time you are treated to the sight of a diving Brown Pelican or a soaring Red-tailed Hawk, perhaps you will be reminded that it’s the unseen players that helped to create the spectacle.


 

Published Western Tanager Vol. 81 No. 2 Nov/Dec 2014

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