Skip to main content

Conservation palaeobiology of oil-polluted tropical marine biota

Final Report Summary - CONSERV PALAEOBIOL (Conservation palaeobiology of oil-polluted tropical marine biota)

Objectives
The project is designed to analyse the effects of chronic pollution by off-shore oil and gas infrastructures on marine life with innovative approaches aimed at overcoming a common problem in environmental assessment: the lack of previous recorded observations of the study site. Indeed, regular environmental monitoring has been a requisite of environmental permits only in the last few decades and only in some areas of the world. As a consequence, missing baseline data are a major impediment to a correct assessment of ecosystem change.
How is it possible to overcome the lack of recorded direct observation? Palaeontology may provide an answer. Palaeontologists reconstruct the history of life on earth – without ever having directly recorded it themselves. They exploit evidence such as fossils, traces, and geochemical observations, and use techniques such as coring and dating, which can be used also to spread light on events much more recent than those they usually inspect. Indeed, the core idea is to transfer these palaeontological approaches to a modern problem, trying to overcome the lack of direct observation.
The study was conducted in two major oil-fields in the Persian (Arabian) Gulf. Pollution effects have been evaluated by classical benthic ecology methods and by palaeontological approaches such as the study of the agreement between the living and death assemblages (all living organisms, and their post-mortem remains such as shells and bones, respectively) and dating techniques (radiocarbon calibrated amino acid racemization).
Hence, the major questions are:
1) what is the pattern of contamination and disturbance to living organisms in relation to the distance from the oil platforms?
2) Can we assess if there has been an ecosystem change since the installation of the platforms, although there are no baseline data?

Work carried out
Our case study was based on two large oil platforms in the Persian (Arabian) Gulf, drilling in the Umm al Dalkh field (discovered in 1969, oil extraction started in 1985) and the Zakum field (discovered in 1963, production started shortly afterwards).
Samples were already available, due to field work carried out by a member of the team back in 1999. The study was focused on molluscs because their shells accumulate in the sediments over long time frames. Polychaetes were also studied to provide a better picture of the living assemblage. The empty shells of two bivalve species were dated with radiocarbon calibrated amino acid racemization, an emerging technique that allows for cost-efficient dating of fossil and modern shells.

Results
Our study showed low contamination values in the sediments and no change of molluscan and polychaete communities in relation to distance from the platform. This result implies that communities did not show significant disturbance.
We have also observed a significant difference in structure and composition between the living and the death assemblage, which can be evidence of a major ecosystem change that occurred in the last decades. Shell dating, however, helped us to understand that this mismatch was not due to disturbance to the ecosystem, but to the peculiar population dynamics of a single, but overwhelmingly abundant (ca. 50% of all shells) species, which was present only as empty shells and was not found alive. Shell dating showed indeed that the species had heterogeneous demographic peaks in space and time.

Conclusions
The project allowed to assess disturbance around two major oil infrastructures in the Persian (Arabian) Gulf, and results suggest there was no major disturbance to living organisms at the time of sampling. On one side this may be related to the lack of major accidents in the studied areas, on the other side the presence of the platforms may have a protective role because no other human activities (such as fishing, trawling, anchoring) are allowed in the nearby areas.
Moreover, the project allowed to discriminate between natural and anthropogenic sources of mismatch between the living and death assemblages, contributing to the development of palaeontological methods for environmental assessment. Species characterized by large, but fluctuating populations may interfere with our ability to evaluate change in the ecosystems with live-dead studies, but shell dating is a powerful tool which supports the interpretation of data.

Impact
Lack of recorded direct ecosystem observation before infrastructures were realized is very common in environmental assessment studies. Anthropogenic pressures to marine ecosystems such as fishing, damming of rivers (which interferes with nutrient and sediment transport), pollution, started much before systematic environmental monitoring was even conceived.
Our project demonstrated that palaeontological approaches can overcome this impediment by providing evidence of whether a major community shift ever occurred.

Contacts:
Dr. Paolo G. Albano, e-mail: paolo.albano@univie.ac.at
Prof. Martin Zuschin, e-mail: martin.zuschin@univie.ac.at
Project website: http://www.univie.ac.at/conservationpalaeobiology/