standardization of environmental data and information - International ...

Commenting on a suggestion to utilize Th-234, Smith agreed that
that would be useful for shorter bioturbation rates. However, it might
provide a level of detail that need not be specified. One problem with Th-
234 was its short half-life of 24 days, so that, on a six-week exploration or
monitoring cruise, samples would have to be measured at sea.
One participant drew a distinction between macrofaunal and
meiofaunal bioturbation, which could be measured with the methods being
discussed, and surface bioturbation by the megabenthos, which could be
evaluated by a deep-sea profile recording animal traces and other seabed
features. Smith agreed, adding that looking at the abundance of
bioturbation features was not a rate measurement but might provide an
index of the nature of the community before and after a disturbance -- for
example, if bioturbation from megafauna could no longer be seen. Another
participant, however, cautioned against mixing up old and recent
bioturbation features, given the low sedimentation rate that did not cover
surface traces, thus making it difficult to understand them in a quantitative
way. Her laboratory combined these results with Pb-210 readings, but the
latter gave a mean measurement and were not useful for bioturbation by
large fauna.
Notes and References
1. International Seabed Authority, Recommendations for the guidance of the
contractors for the assessment of the possible environmental impacts arising from
exploration for polymetallic nodules in the Area: prepared by the Legal and Technical
Commission (ISBA/7/LTC/1), 10 April 2001; further revised and approved by the
Commission as ISBA/7/LTC/1/Rev.1 of 10 July 2001. On 12 July 2001, the ISA
Council deferred consideration of the recommendations until its eighth session
(August 2002).
2. A. Knap et al. (eds.) (1996), Protocols for the Joint Global Ocean Flux Study (JGOFS)
Core Measurements (JGOFS Report No. 19), vi+170 pp. (reprint of IOC Manuals and
Guides No. 29 [United Nations Educational, Scientific and Cultural Organization,
1994]), chapt. 24: JGOFS sediment trap methods.
3. Ibid.
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