Life in the littoral zone
August 27th, 2008 | Category: Fats, Vitamins & Minerals > Takaw at Sursur!As expected, we woke up too late for the morning market!
However, we did manage to go swimming - err, actually, wading - today. Excited, we had our goggles and masks but the tide was really really low.
I looked in the water and saw a small metallic blue fish! When I went in, I saw more fish, more starfish and more corals and sea anemones, urchins, tiny shrimps, a tiny jellyfish …
I also spotted a blue starfish - at first, I thought that it was a plastic toy but when I picked it up it started moving!
I looked it up and found out that it is a Linckia laevigata:
An inhabitant of coral reefs and sea grass beds, this species is relatively common and found in sparse density throughout its range. They live subtidally, or sometimes intertidally, on fine (sand) or hard substrata.
Hmmm … where we were wading is certainly a seagrass bed!!
Seagrasses form extensive beds or meadows, which can be either monospecific (made up of one species) or multispecific (where more than one species co-exist). In temperate areas, usually one or a few species dominate (like the eelgrass Zostera marina in the North Atlantic), whereas tropical beds usually are more diverse, with up to thirteen species recorded in the Philippines.
Aha!
The Baclayon seagrass bed certainly is a diverse eco-system - all those marine plants and animals. Because the tide was very low this afternoon, there were more people wading picking up edible seaweeds and shellfish. The seagrass surely provide the conditions needed for the abundance of marine life just there along the coast.
Seagrasses are sometimes labeled ecosystem engineers, because they partly create their own habitat: the leaves slow down water-currents increasing sedimentation, and the seagrass roots and rhizomes stabilize the seabed. Their importance for associated species is mainly due to provision of shelter (through their three-dimensional structure in the water column), and for their extraordinarily high rate of primary production. As a result, seagrasses provide coastal zones with a number of ecosystem goods and ecosystem services, for instance fishing grounds, wave protection, oxygen production and protection against coastal erosion.
I also saw tons of sea urchins, and am quite surprised that people here don’t seem to be harvesting them for food. According to the Wikipedia entry on sea urchins:
Sea urchins are an important fishery and are harvested for food. Contrary to popular belief, the portion of the sea urchin sold and served as one of the ocean’s most opulent treasures is not the roe. It is the gonads of this hermaphrodite sea creature that are scooped out of the urchin’s spiny shell in five custard-like, golden sections. Known in Japan as “uni” and traditionally considered an aphrodisiac, gonads are the only edible part of the urchin.
Hmmm…
Interesting, but those spines!!
The spines, which in some species are long and sharp, serve to protect the urchin from predators. The spines can inflict a painful wound on a human who steps on one, but they are not seriously dangerous, and it is not clear that the spines are truly venomous (unlike the pedicellariae between the spines, which are venomous).
Next time, I’ll bring my camera and take photos of all these creatures. Trevor and I spent the whole afternoon just wading around and looking at these things under the water!









