Fluorescent proteins in corals have been re-ported to have photoprotective function for algal sym-bionts, though it remains controversial whether the coral fluorescent proteins are actually photoprotective. Green (Gs) and brown (B) morphs of the coral Galaxea fascicularis have different contents of green fluorescent protein (GFP). To understand the function of GFP in the stress responses of the coral, we exposed polyps isolated from B and Gs morph colonies to medium or strong light (200 and 1000μmol quanta m-2s-1) at 26 or 32°C for 6h. Polyps were then allowed to recover for 6h under dim light. Although the GFP content was markedly different between Gs and B morphs, in hospite zooxanthellae in polyps of both morphs showed similar decreases in photochemical efficiency (Fv/Fm) after strong light treat-ment at normal or high temperature. Isolated zooxanthellae of both morphs showed similar decrease in the photo-chemical efficiency under light stress, indicating that they had similar tolerance to light stress. The present results suggest that fluorescent protein does not increase the tolerance of polyps to strong light and high temperature stress in G. fascicularis and that further studies are nec-essary to elucidate the function of GFP in this coral.
The response of Acanthaster planci or crown-of-thorns starfish (COTS) to intracoelomic injection of hypersaline solutions was investigated to establish its potential application as A. planci population control es-pecially during an outbreak. Adult A. planci when inverted had a normal righting response time (in seconds) of 163±1 (mean±SE; N＝298). Injection of concentrated salt solutions led to negative effects on adult A. planci. The spines bent down, body collapsed and the starfish became comatose and died after 24-hours. The higher the salt concentration, the higher is the % comatose indivi-duals. In addition, comatose specimens failed to recover with time. Mortality was highest at the highest treatment concentration with LC90 of 285.3 and LC99 of 383.2ppt. The effects of time, salt concentration and its interaction (salt concentration x time) were significant (p＝0.00). The ionic and osmotic disruption of the coelomic fluid can seriously affect physiological functions of the organism including neuromuscular activity. Thus, in the control of A. planci, concentrated salt solution can be used as a cheaper alternative to dry acid, acetic acid or ammonium hydroxide, all of which are expensive, may not be locally available and not environment friendly.
In May 2015, during summer, macro alga Chaetomorpha linum was seen entangled in high density on coral colonies at northern part of the Shingle Island (09°14’607”N 078°13’863”E) in Gulf of Mannar, Southeastern India. Underwater assessment revealed that C. linum bloom has proliferated on coral colonies of Acropora and non-acropora species. Filaments of C. linum formed larger mats and got entangled with coral colonies reducing light making hypoxia. The inter tidal zone of northern part of the Shingle Island has rich coral cover with about 23.5% at 0.5 to 3.0 meter depth (Patterson et al., 2007). Live coral cover decreased from 23.5% to 18.5% due to the sudden proliferation of C. linum. Maximum coral mortality was observed in branching corals such as Montipora divaricata, Acropora cytherea and Pocillopora damicornis. Other coral species under stress were Acropora intermedia, A. muricata, Montipora foliosa, Echinopora lamellosa, Porites solida and Favia pallida (Fig. 1 A to D). The present observation can be useful for further investigations regarding the spreading rate, algal biomass, nutrient level, and status of associated biodiversity from the bloom affected reef area.
To assess the effectiveness of the temperate coral, Alveopora japonica as an impact indicator, we examined the effects of various environmental variables on the coral’ short-term population dynamics in Tateyama Bay, Chiba, Japan. We measured coral cover, colony den-sity and colony size of A. japonica in June, August and November 2013. Newly identified colonies were recorded separately. We analyzed the relationships between colony density, substrate types, and seawater temperature using a generalized linear mixed model. Both coral cover and colony density decreased between August and November, showing high mortality during this period. In November, a decrease in mean colony size and skewness of colony size distribution, compared with August, was attributed to mortality of large colonies and an increase in the abun-dance of small colonies. Newly identified small colonies were observed in August and November. The presence of these colonies may be in part due to accelerated planulation (i.e., recruitment). The generalized linear mixed model showed a significant trend of increasing colony density with seawater temperature rise, potentially resulting from recruitment during the high-temperature period. In addi-tion, there was a negative effect of sand substrate on colony density. Since the sand substrate abundance was significantly correlated with typhoon occurrence, we sug-gest that typhoons could be one of the major factors affecting the short-term population dynamics of A. japonica in Tateyama Bay.