Soft corals are able to produce a rich source of chemical substances as they are mostly sessile during the adult phase. Their inability to escape from predators, competitors fighting for space and ultraviolet radiation exposure causes them to develop these bioactive molecules in order to discourage predators, prevent competitors to overgrow them and filter from harmful radiation (Fabricius & Alderslade 2001). The group of chemicals identified as terpenoids are toxic and capable to reduce palatability are responsible of deterring predators from feeding on the corals (Fabricius & Alderslade 2001). Besides that, the soft corals are also capable in producing anti-fouling substances which prevent overgrowth of algae or fungi on the colonies. In addition to that, soft corals such as Sinularia and Sarcophyton species are able to release allelopathic substances into the water to hinder neighbouring animals or plants to overgrow and compete for space (Fabricius & Alderslade 2001). Shallow water organisms including these soft corals have developed unique compounds known as mycosporine-like amino acids (MAAs) to screen out the high ultraviolet radiation exposure (Fabricius & Alderslade 2001).  

Studies were done to determine the chemical constituents of the genus Cladiella soft corals by various research groups as this genus is proved to have a rich supply of cytotoxic eunicellin-based sesquiterpenes and diterpenes. Cladiellin, acetoxycladiellin, cladioxazole and cladidiol are some of the examples that belong in this group (Radhika 2006). The most significant breakthrough related to the Cladiella pachyclados is the discovery of 5 new eunicellin diterpenes which are the pachycladins A-E. These diterpenes were found to show significant anti-invasive and migratory inhibitory activities of the prostate cancer cells (Hassan et al. 2010).

The next group is the ceramides, cerebrosides, lipids and glycolipids (Radhika 2006). A combination of cerebroside homologues and a lipid glycoside was researched independently and found that they have a significant antifungal and antibacterial activity (Radhika 2006). The last group of chemical constituents discovered are the sterols and sterol glycosides (Radhika 2006). In conclusion, 55 complementary metabolites have been isolated from the various Cladiella species and further studied by researchers.

Project 1:

The effect of water flow on the production and accumulation of mucus in the surrounding of Cladiella pachyclados.

Hypothesis:

Mucus produced by the colony tends to aggregates around it and potentially affects the coral health under low water flow.

Methods:

1.      Two colonies were obtained and placed in separate aquariums.

2.      One of the colonies was placed under strong to moderate water flow and the other in slow to no water flow.

3.      Observations were made over time.

Results:

As shown in the picture below, mucus coatings are seen in the slow to no water flow aquariums whereas in the strong to moderate water flow, no mucus aggregation is seen.

Discussion:

Some soft coral species are known to occasionally excrete a film of waxy mucus when stressed. The mucus functions as a chemical shield or to clean the colony surface from sediments and fouling organisms (Fabricius & Alderslade 2001). Accumulation of these mucus coatings leads to a build-up of bacteria and thus causes illness to the colonies. Therefore, moderate to high water flow is adamant for the Cladiella pachyclados to eliminate the mucus from the surroundings of the coral (Thiel 1997). This explains the need for the colonies to reside in the coastal waters on crests or rocky shores with high wave action in order for the current to remove the mucus and leave a clean colony. However, due to insufficient time on the Heron Island, this experiment was unable to be carried out to investigate the time taken and the quantity of mucus produced by the coral which will cause serious illness to the colonies.