[en] Hydrothermal vent environments, particularly those
associated with the vestimentiferan Riftia pachyptila, are
believed to be among the highest chitin-producing systems. In
order to elucidate the chitin cycle in these environments, we
estimate the in situ chitin degradation rates of tube-worm
exoskeletons. Our in situ experiments show that the tubes of
Riftia are highly stable structures. Comparative measurements of
the degradation rates of Riftia tubes and crab shells immersed
at deep-sea vents show that the tubes would be degraded within
2.5 years, whereas the time for the total degradation of the
vent crab (Bythograea thermydron) carapaces would not exceed 36
days. The importance of the microbial participation in this
degradation was estimated for Riftia tubes. Based on previous
work, we calculated chitin production by a population of Riftia
tubes of about 750 g m(-2) year(-1) (763). From our in situ
experiments, we estimated a microbial chitinolysis rate of about
500 g m(-2) year(-1) (496) (65% of the