Native Hawai'ian seagrass in the fishpond

While looking for fish and crabs along the seawall this weekend, I found a few small plants like these growing among in cracks in the makaha. They belong to the genus Halophila, which is the only true seagrass found in the Hawai'ian Islands, and they are delicate plants usually found in sand flats. Patches of Halophila grow in other parts of Kaneohe Bay, so it's possible that fragments or seeds and pollen from these neighboring plants got caught in the seawall and took root. This seagrass is also found in completely marine waters (instead of estuarine environments, like some other seagrasses), which goes to show how much marine influence there is on the ocean side of the fishpond.

There are two species of Halophila present in Hawai'i: Halophila hawaiiana, which is native to Hawai'i, and Halophila decipiens, which is from Thailand. The only way to distinguish the two species from one another is by checking for the tiny spines that grow on the outside edge of the leaves of H. decipiens. It was hard to see these leaves very well, but it looks like this plant is H. hawaiiana: a rare endemic seagrass occupying the fishpond! This has exciting implications for pond rehabilitation: maybe if limu removal projects are successful, native plants like this can take over those niches. Seagrasses stabilize sediment and provide food for fish and turtles.