Advancing marine biotechnology: use of OCS oil platforms as sustainable sources of marine natural products

Abstract

This research was conducted in the Santa Barbara Channel, southern California. From Significant Conclusions: “Although the major macroinvertebrate taxa were common to all platforms, the relative abundance of these taxa (as percent cover) varied along the SBC such that platforms in close proximity to one another tended to have invertebrate assemblages more similar to each other than to platforms located further away. However, there were exceptions to this general gradient pattern. For example, the cover of sponge was highest at Platform Gail, one of the southern platforms and cover of Metridium was low (3%) at Hogan, one of the northern platforms. Further, conspicuous exotic species were present in high cover on two of the platforms, the anemone, Diadumene sp. on Gail and the encrusting byrozoan, Watersipora subtorquata on Gilda.

We propose that along-channel variation in platform invertebrate assemblages result, in part, from regional oceanographic gradients created through the advection of waters into the channel from the south via the Inshore Counter Current and Southern California Eddy during the spring and summer. Along-channel variation in water temperature measured at the platforms during this study was consistent with the temperature patterns reported by Otero and Siegel (2004) from the compilation of monthly satellite SST data covering the period 1997 to 2001. The anemone, Metridium sp. (probably M. senile) appears to prefer cooler waters with a distribution range extending from southern California to Alaska, which may explain the higher density of this species on the northern platforms. Current flow from the south also provides a mechanism for the transport of invertebrate larvae into the channel. The higher recruitment densities for three species of barnacles at the southern compared to the northern platforms was consistent with predictions of oceanographic conditions bringing warm water masses and the longer-lived planktonic larvae of southern taxa, such as Balanus trigonus into the channel.

Platform assemblages are probably also strongly influenced by founder effects. This supposition is supported by the presence of exotic species, Diadumene sp. and Watersipora subtorquata, each on different platforms. These species were probably introduced via barges or crewboats, have limited dispersal ability, but occur in high cover and appear to be superior competitors for space. In addition to founder effects, biological interactions, including predation and competition undoubtedly influence the structure of platform invertebrate assemblages.

Growth rates of caged Mytilus galloprovincialis also varied along the SBC during the summer, with highest growth rates at the southeastern platforms. This pattern coincided with the temperature gradient that typically develops from the east to the west end of channel during the summer. However, gradients in water temperature per se do not satisfactorially explain spatial and temporal variation of mussel growth in the channel. Alternatively, spatial and temporal variation in mussel growth rate may reflect food availability, or the interaction of food availability and water temperature. The existence of along-channel patterns in the composition of platform assemblages, and in invertebrate recruitment and growth, suggests that assemblages attached to platforms may be useful as barometers of short and long-term change in oceanographic climate. Over the shortterm, changes in oceanographic conditions may influence invertebrate recruitment and growth. Over the longer-term, changes in climate that alter ocean currents (e.g. ENSO events, global warming) may shift the composition of platform invertebrate assemblages. Our results indicate that invertebrates, such as sponges, tunicates, and bryozoans, that may contain potentially useful marine natural products can be abundant on offshore oil platforms. However, the significant variation found in the distribution, recruitment and growth of these invertebrates among platforms in the SBC suggests that factors such as location and temperature could affect the potential harvest of these organisms for use in the development of marine natural products.

Significant biological activity in the crude extracts of a number of species of platformdwelling organisms were found in this study, including species of anthozoa, bryozoa, and chlorophytes. Crude extracts of the exotic anemone, Diadumene sp. from Platform Gail showed strong biological activity in the sea urchin bioassay and a human cancer cell line. Our results on specific action and activity suggest that coumarins, such as dicoumarol, possess a unique anti-proliferative mechanism of action and possibly related pharmacophores are mediated by tubulin binding and the kinetic stabilization of spindle microtubule dynamics.

The coumarin pharmacophore thus may represent an attractive compound for development of new drugs for cancer treatment. The red pigment (WC01-A) found in the exotic species of foliose bryozoan, Watersipora subtorquata, from Platform Gilda appears to be a compound which has not been previously described before in the literature. The compound shows a high degree of bioactivity in the sea urchin embryo model assay and in other human cancer cell lines. These results suggest it is a viable candidate for further cell division studies. High instability of the compound is also indicated by our results. However, further analytical study of derivatives could provide key information for the characterization of the complete compound. For the branching bryozoan, Bugula neritina, no members of the ‘shallow’ clade were found on either OCS platform sampled. This may have been due to sampling only at moderate to deep depths though Davidson and Haygood (1999) found members of this clade at depths up to 10 meters. The very high frequency of the bryostatin-producing Deep-1 clade members on the platforms suggests that collections of B. neritina from these artificial habitats would contain high yields of bryostatins, undiluted by members of the Shallow clade that does not contain them. Very little population structure was identified though samples from the two oil platforms were members of a single subclade suggesting limited dispersal of this species. Sequencing larger and more variable regions of mtDNA between the 16s and COI genes, allowed us to identify a new cryptic species of B. neritina that is very closely related to the cryptic species that associates with the bacterium E. sertula and produces bryostatins. The new cryptic species of Bugula neritina that we identified was rare in our samples and was only obtained from reefs on Santa Cruz Island. The bryostatin-producing capabilities of this new cryptic species of Bugula neritina were not evaluated”