Hawai'i Seagrass - Not your average flowering plant

HIMB beach scene - underwater.    Photo M Heckman

It is not really a seaweed, it is a sea-grass. What is the difference?

Seaweeds do not have true veins to move nutrients internally, whereas seagrasses do, very similar to flowering land plants.

A single seagrass blade. M Heckman photo

Seaweeds do not produce flowers for reproduction. Seagrasses, however, have both male and female flowers, they are just rather subtle so we don't tend to notice them.

Seagrass flower. Photo from UH Botany site

Seagrasses are a secondary invasion of the sea. Millions of years ago, plants moved ashore, then, at some time a very few moved back - there is just no stopping nature.

Image from National Marine Fisheries Service SWR

When most folks in the world think of seagrass beds, they think of the long flat blades of the eelgrasses or aptly named turtlegrasses. These environments are nursery areas for juvenile marine animals, feeding areas for turtles and manatees, they stabilize sediments, recycle nutrients, clear water and are just generally a good thing. Like many of the soft sediment communities, seagrass meadows tend to be under-appreciated. They do not have the bright colors of the hard corals, but they are tremendously important.

Image from National Marine Fisheries Service SWR

A recent article in Live Science notes that a seagrass meadow in the Mediterranean might be the oldest living plant in the world. Instead of thinking of a single tree, like a redwood, with one trunk soaring up into the sky, think of a low flat tree just spreading out and out - a clonal structure. As some parts die off, others continue on - a meadow of one. Years pass by, and the seagrass meadow is now over 9 miles across. Still one clone, one being - now 100,000 years old. Redwoods have nothing on these plants.

In Hawaii, the seagrasses in our shallow waters are quite elegant. They are the Halophilas, the salt lovers (from the Greek hals for salt and philos for love). We have two species, Halophila hawaiiana (endemic) and Halophila decipiens (worldwide distribution). Rather than having long flat blades, they have small canoe paddle-like blades - only an inch or so long. Most folks pass them right by, although our sea turtles do not (free greens for browsing)!

HIMB beach scene - the meadow - depth 1 foot. Photo M Heckman

Once you stop to admire these delicate meadows, you will never miss them again. One such meadow is in just inches of water right off of the beach at HIMB. Out of the water it appears as just a slightly darker patch in the sand. In the water they are translucent and emerald green. More than one seahorse has been seen drifting through the tiny blades. So next time you are headed out or in from a snorkel on the coral reef, take a moment to view the sandy patches - and possibly magnificent meadows of our native seagrasses.

We will have more on this later, with some entries from Castle H.S. intern Rebecca Weible, who has been studying one of the patches off of the beach - and finding some surprising results.

In the mean time - check out the following sites or references for more information (and as sources for this articles).

Note the micro algae growing on the seagrass! Photo M Heckman

My favorite: Hawaiian Reef Plants Huisman, John, Isabella Abbott, and Celia Smith. Hawaiian Reef Plants.Honolulu :University of Hawai'i Sea Grant College Program, 2007. Pp:199-202. Print.

Most enthusiastic sea grass website: Singapore's Team Seagrass.
"Cyrene Reef." Team SeaGrass.National Biodiversity Center, 11 Mar. 2012. Web. 17 March 2012.

For ID and other accurate info locally: University of Hawaii Botany Department, Marine Algae of Hawaii, http://www.hawaii.edu/reefalgae/invasive_algae/seagrasses/seagrasses.htm

Is that a flower on our seagrass? Photo M Heckman

"Halophila decipiens." Invasive Marine Algae of Hawaii. Department of Botany University of Hawaii at Manoa, 2002. Web. 17 March 2012.


See also:
Seagrass Watch International.


Choi, Charles. "Behemoth Seagrass Clones Among Earth's Oldest Organisms." LiveScience, 1 Feb. 2012. Web. 17 March 2012. <http://www.livescience.com/18253-ancient-seagrass-clones-oldest-life.html>.

Fourqurean, J.  "Sea Grass Monitoring Project." Florida Keys National Marine Sanctuary. NOAA, Aug 2011. Web. 16 March 2012.
 http://floridakeys.noaa.gov/scisummaries/seagrass_monitor.pdf

"Importance." South Florida Aquatic Environments,Seagrasses.Ichthyology at the Florida Museum of Natural History. Web. 16 March 2012.
http://www.flmnh.ufl.edu/fish/southflorida/seagrass/importance.html 

Coles, R. "Seagrasses in Queensland Waters." CRC Reef Research Centre, 2004 Web. 16 March 2012.
http://www.reef.crc.org.au/publications/brochures/CRC_Reef_seagrass_web.pdf

 "Seagrass- Socioeconomic Importance."Habitat Conservation Division. NOAA's National Marine Fisheries Service, Southwest Regional Office, 03 Aug. 2011. Web. 16 March 2012.
http://swr.nmfs.noaa.gov/hcd/hcd_webcontent/socal/HAPC/seagrass3.htm

Greek definitions from: http://dictionary.reference.com/browse/philo- and
http://dictionary.reference.com/browse/halo