Reproductive effects of the water-accommodated fraction of a natural gas condensate in the Indo-Pacific reef-building coral Pocillopora damicornis.

Toxic effects of the water-accommodated fraction (WAF) of a natural gas condensate on the reproduction of the brooding coral Pocillopora damicornis were studied in short-term (24 h) laboratory experiments. Coral fragments were exposed to varying concentrations of condensate WAF during different reproductive phases: gametogenesis, early embryogenesis, and late embryogenesis (when nighttime planulation occurs). During gametogenesis, exposure to condensate WAF did not inhibit subsequent production of larvae. On the other hand, exposure to >25% WAF of gravid corals, at early and late embryogenesis, resulted in abortion and early release of larvae, respectively, with higher percentages of larvae expelled in fragments treated with higher concentrations of condensate WAF at least 3h after onset of exposure. Aborted larvae during early embryogenesis were 'premature', as they are of small size (0.06±0.03 mm³), low metamorphic competency (54%), and white in coloration, with a pale brown oral end (indicating low density of zooxanthellae). Those larvae released at the latter part of embryogenesis are bigger in size (0.22±0.08 mm³), possess 100% metamorphic competency, and are brown in coloration (high density of zooxanthellae). Aside from direct effects on reproduction, fragment mortality index was higher in samples exposed to higher concentrations of condensate WAF (>25%), hence lowering the number of potentially reproducing polyps. Altogether, exposure to >25% natural gas condensate WAF for at least 3h can potentially disrupt the replenishment of coral populations due to negative effects on reproduction and early life processes.

Postharvest culture in the dark: An eco-friendly alternative to alkali treatment for enhancing the gel quality of kappa/iota-hybrid carrageenan from Chondrus crispus (Gigartinales, Rhodophyta).

After harvesting from natural stocks, female gametophytes of the red seaweed Chondrus crispus were cultured for several days under a light-deprived regime in order to determine if dark treatment can improve the gel quality of carrageenan extracted from the seaweed. An increase in the gel strength of native carrageenan was observed after dark treatment for 10d, but not after 5d, as compared to that of freshly harvested (baseline) seaweed. Corresponding decrease in sulfate and increase in 3,6-anhydrogalactose (3,6-AG) contents of the carrageenan extract were also observed. We posit that during dark treatment, the production of sulfated carrageenan precursor units was prevented while the enzymatic conversion of the prevailing precursor units to the gelation-promoting 3,6-AG was allowed to proceed. The observed increase in carrageenan gel strength with a 10-d dark treatment was comparable to the effect of the widely-used industrial procedure of alkali treatment in improving the extract's gel quality. Hence, postharvest culture in the dark for 10d can be an eco-friendly alternative to alkali treatment.

Effects of natural gas condensate - water accommodated fraction on coral larvae.

The toxic effects of the water accommodated fraction (WAF) of a natural gas condensate on the larvae of five brooding coral species of the Family Pocilloporidae were examined in short term (96 h) bioassays. Lethality was observed in some larvae of Seriatopora hystrix and Seriatopora guttatus upon exposure to high concentrations of the condensate WAF, while those of Stylophora pistillata, Pocillopora damicornis and Pocillopora verrucosa did not experience mortality. Furthermore, increasing concentrations of WAF produced either delayed or impeded metamorphosis for all species except P. damicornis. Growth of juveniles, exposed to different WAF treatments for 96 h during their larval/early juvenile stages, was measured after 30 d. Marked decrease in subsequent growth rate (polyp count) was observed for S. hystrix, S. guttatus and S. pistillata with increasing WAF concentration. The results showed differential susceptibility of larvae of closely related coral species to oil stress, with the following sensitivity ranking: S. guttatus>S. hystrix>S. pistillata>P. verrucosa>P. damicornis. Oil exposure during the planktonic, larval stage of susceptible corals can adversely affect survivorship, recruitment and/or subsequent colony growth, thereby having profound consequences for the abundance of these corals in space and time.