Biological Oceanography

(ff) #1

among the bones and can remain intact for several years. For example, a blue- or fin-
whale carcass discovered during a submarine investigation in a basin off Southern
California in 1987 was still a distinct skeleton in 2005 (Glover et al. 2005a), with
filamentous mats of the colonial bacterium Beggiotoa developed over it. Bathykurila,
a genus of polynoid scale worms (polychaetes) also found at hydrothermal vents,
were grazing on the mats. Thus, whale falls could be “stepping stones”, allowing
larvae of these worms and other fauna to transit between vents. Whale skeletons can
also be densely covered by gutless siboglinid worms similar to vestimentiferans at
vents, but belonging to a distinct genus, Osedax. They are only recently described
from whale falls (Rouse 2004), but the genus currently has more than eleven species
(e.g. Glover 2005b). Rouse reports that nutrition is absorbed through a root-like,
posterior structure penetrating the bone and populated by heterotrophic symbiotic
bacteria, while Glover suggests that the possibility of chemosynthetic symbionts has
not yet been excluded. Whale bone is rich in sulfo-lipids. Whether these several
worms are important in the wider economy of the benthos is uncertain but unlikely,
whereas the distribution and redistribution of deadfall meat and soft organs may be
moderately significant.


(^) Wood is often collected by trawls on the deep seabed. Logs and sticks acquire
modestly complex faunas of animals tightly adhering and eating or abrading sockets
for themselves, such as limpets. Several groups of clams, shipworms (Teredinidae),
and wood-specializing pholads (Xylophagainae), bore into the mass of the wood as
they grow (Pailleret et al. 2007; Voight 2007). To some extent the importance of the
wood is as solid substrate, but given symbiotic cellulose-digesting bacteria for
digesting the wood, the case with at least shipworms, it serves also as food.


Seasonal Cycling in the Deep Sea


(^) The 1–2% of primary production that eventually sinks to the deep seafloor has been
shown to be almost as strongly seasonal as is surface productivity. Results from an
early time-series trap (Deuser 1981) showed the seasonal sequence in the Sargasso
Sea of productivity reflected in arrival of materials reaching 3200 m (well above the
seafloor). The ∼1% fraction reaching depth was found in deep-sea particle flux, and
unexpectedly so was the seasonal variation of productivity. That time-series was
extended (Conte et al. 2001) near the BATS Sargasso Sea site for 20 years, and with
two-week resolution from 1989 to 1998 (Fig. 13.28). The timing of the annual (with
exceptions) late winter bloom at this subtropical station is in a general way
reproduced by flux at 3200 m (despite the lack of significant time-series cross-
correlation according to Conte et al.).
Fig. 13.28 Top: BATS approximately monthly time-series of primary production (^14 C-

Free download pdf