Monterey Bay Aquarium Research Institute
Marine Botany

Antithamnion defectum


Global Distribution

The genus Antithamnion is found everywhere in the world! Most representatives of the genus are found in the Pacific Ocean, and it is believed that the genus originated in the Pacific. [2] According to the literature, Antithamnion can be found in almost all water temperatures: off the coast of Alaska, British Columbia, along Washington, Oregon, California, Hawaii, the Caribbean, Japan, Korea, Australia, New Zealand, South Africa, Bangladesh, the Arabian Sea, Namibia, the Azores, the Canary Islands, Spain, the Mediterranean, the Black Sea, the Adriatic Sea, Ireland, and the North Sea. Most of the species have a regionally restricted distribution, but at least 4 have been found to have large distributions reaching into both hemispheres! [2] This global distribution of Antithamnion indicates that the genus can tolerate a wide range of temperatures and salinities, although particular species may be more regionally adapted to a smaller range of temperatures and salinities, and majority of species prefer cold temperate waters.

A. defectum has been reported mostly along the Pacific coast of North America from Alaska to Mexico, but also along the Pacific coast of the Russia, China, Sakhalin Is., Japan, Korea, Brittany in the Atlantic and the Red Sea. [2]

Regional Distribution

The genus Antithamnion is commonly found along the Pacific North American coast from Alaska to Mexico, and there are 12 species from Oregon north to Alaska. [5] Antithamnion defectum is characteristically found off the Pacific coast from Alaska to Baja California. [2] A. dendroidem is found in waters from Baja to Monterey, California, indicating that it prefers warmer water. There was one record of it from Alaska, but this record was never confirmed. [5] A. kylinii was reported in 1989 to have a range between British Columbia and Mexico. [5]

map of montereyLocal Distribution

Antithamnion defectum is common in the waters of Monterey Bay, as is A. dendroidem., A. kylinii as well as some other species such as A. glanduliferum, and A. plumula have also been found in the Bay in the past. The records from the Gilbert M. Smith Herbarium at Hopkins Marine Station indicate that A. defectum will grow epiphytically on a wide variety of other algae from large Macrocystis to small Calliarthron, epizoically on Cryptochiton stelleri (a large chiton found in Monterey Bay) , epilithically on rocks, and also commonly on the pilings and other man-made structures at the Monterey Wharf. The wide variety of substrates on which Antithamnion will grow may give it a generalist advantage, rarely being in danger of having no place to settle and grow, unlike obligate epiphytes which have one particular host. In addition, being an epiphyte could potentially allow Antithamnion to travel in currents, as the large algae to which Antithamnion is attached can drift long distances. This, in turn, could increase its dispersal range.

Effects of Global Warming on Distribution

According to the Partnership for Interdisciplinary Studies of Coastal Oceans (PISCO) data-base, Antithamnion dendroidem's northern limit to distribution is currently Monterey Bay, California. With the current rise in sea surface temperature due to global warming, there is a possibility of a northward-shift in distribution of this species. Future monitoring of this species' distribution could be very interesting. In addition, a look into the past at historical distribution could also provide evidence for global warming. A much more exhaustive survey would need to be done through herbariums along the central California coast; however, in my searches in the last couple months, I have found mostly A. dendroidem as opposed to other species of Antithamnion. Interestingly, most specimens of Antithamnion in the Gilbert M. Smith Herbarium, collected primarily by Isabella Abbott in the 1950s-60s, are A. defectum. The herbarium contains only three specimens of A. dendroidem. Could Antithamnion species distributions already have shifted over the last fifty years?

Epiphytic Growth

antithmnion on a nereocystis stipeAn amazing study was done in 1969 by James Markham at Friday Harbor on the patterns of epiphytic growth on Nereocystis luetkeana, the large bull kelp which is also common on the wave-swept coastline of Carmel, CA. This study found that young Nereocystis plants appeared in April, and epiphytes began to colonize them by June, but were not abundant until August. The first to colonize the plants was a diatom, Navicula grevillei, which completely disappeared once Enteromorpha linza appeared in July. Antithamnion appeared in August, and by October it was the dominant alga on the stipes. On the upper portions of the stipe (above 100 cm depth) which often laid horizontal on the water surface, Enteromorpha dominated the upper, light-exposed side, while Antithamnion and Ectocarpus shared the underside of the stipe. Below 100 cm, Antithamnion outcompeted most epiphytes, and extended down to deeper parts of the longest stipes. I think this may reflect a sensitivity of Antithamnion to high light intensity, or the fact that it is out-competed by Enteromorpha above 100 cm where light is high. Its dominance below 100 may be due to its high growth rate and its ability to grow under lower light levels due, at least in part, to accessory pigments. There is more discussion of Antithamnion's growth under various light conditions on the growth-experiment page.

Possibly the most fascinating part of this study was the distribution of various life-stages of Antithamnion on the Nereocystis stipes. Small, slow growing, vegetative Antithamnion grew on the upper and lower limits of the distribution. Inside of the vegetative Antithamnion at the top and bottom were the female gametophytes, and in the middle of the stipe were the tetrasporophytes. Male plants were so small and uncommon that they did not dominate anywhere on the stipe. This same pattern existed on shorter stipes in shallower water and on longer stipes in deeper water. This pattern was hypothesized not to be governed primarily by light, but by some other factor present at the bottom as well. More ecological studies of these patterns are needed.

A further experiment with artificial plastic kelps showed the same pattern of distribution suggesting Nereocystis was important only as the substratum. The lack of Antithamnion on the lowest part of the stipe was hypothesized to be due to snail grazing, as Antithamnion is abundant on rocks on the benthos. [9] It is an interesting pattern to see Antithamnion reproductive on the middle portion of the stipe surrounded on either side by vegetative Antithamnion.

Where I found Antithamnion:

I found Antithamnion defectum on horizontal rock surfaces at 30 feet (9 meters) while diving on the Western side of the Breakwater in Monterey Bay, as well as on the Monterey Bay aquarium water-intake pipe at 45 feet (13.7 meters). At Breakwater, Antithamnion was sharing the rock with crustose coralline algae, Pugetia fragilissima, juvenile Mazzaella flaccida (previously Iridaea flaccida), Fauchea laciniata, and Polysiphonia sp. On the aquarium intake pipe Antithamnion was growing among many other tiny red algae such as Polysiphonia, Callithamnion, Pterothamnion, and Microcladia. The water temperature at both sites was 55 degrees Fahrenheit (12.8 degrees Celsius), which is the warmer end of the range of temperatures for central California.

Antithamnion on a rock antithamnion on rock

I found A. dendroidem growing on a buoy line on the edge of the Hopkins Marine Life Refuge, on the aquarium sea-water intake pipe, on a floating boat launch dock at the Monterey harbor, on a Macrocystis pyrifera pneumatocyst (float) which had drifted onto Carmel Beach, on the stipe of Nereocystis leutkeana which had washed ashore on South Asilomar beach, and even growing in the outdoor laboratory bins at the marine station!


 Antithmnion on a buoy lineclose up of float

To see more pictures, including underwater shots of Antithamnion, please go to the Photo Gallery page. Please note that this page may take extra time to load due to the number of pictures.

Is Antithamnion intertidal?

Based on where I found Antithamnion and where it was found in the past, I hypothesize that it is unlikely to be found in the intertidal. This may be due to its delicate and fragile structure which could easily be damaged if rubbed against rocks by crashing waves. The fact that it is found on rocks deeper in the water where wave action is minimized and within the protected area of the wharf further supports this hypothesis. In addition, the thin single celled structure of Antithamnion would probably desiccate more quickly than a thicker algae, which is why I never found it in a place where it could fall below the tidal line. However, the fact that Antithamnion is found on Nereocystis stipes which are usually in areas with high wave action indicates that it probably can withstand significant water motion. Its ability to flatten down against the stipe probably reduces most of the drag.

Is Antithamnion an invasive species?

I believe that Antithamnion could be classified as having a fast growth rate and perhaps even an opportunistic life-style. Adult Antithamnion are present in the Hopkins tanks within two months of running sea water through the tank. Furthermore, the Japanese A. pectinatum is now officially an invasive species in the Venice harbor in Italy, and it has competed well for space with indigenous species. [6] Antithamnion's ability to live on almost any substratum, survive year-round, grow quickly, and live all over the world makes it a great competitor.

Benefits to the Kelp Forest Community?

Although Antithamnion may be a great competitor and even invasive in some parts of the world, it also may provide a benefit to the community in which it lives. A recent study found that gametophytes of the kelps Nereocystis luetkeana and Alaria esculenta became epiphytic on several algae, including Antithamnion defectum. [8] In this way, A. defectum harbors a microscopic life-stage of these kelps, indirectly contributing to the recruitment of the large sporophytes characteristic of kelp forest communities.

Antithamnion Home | Taxonomy | Distribution/Ecology | Morphology | Life History |

Growth Experiment |Photo Gallery | Terms

References and Acknowledgements

© 2005 Charlotte Stevenson

Last updated: Feb. 05, 2009