SIBER SPIS sept 2011.pdf - IMBER
SIBER SPIS sept 2011.pdf - IMBER
SIBER SPIS sept 2011.pdf - IMBER
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<strong>SIBER</strong><br />
Science Plan and Implementation Strategy<br />
●● Characterisation and quantification of microbial processes<br />
●● Determination of the cycling and burial of bioelements<br />
●● Determination of benthic fluxes of dissolved nutrients, organic matter, gases and metals<br />
and their significance to ocean inventories<br />
●● Tracer studies of benthic organic matter cycling and trophic interactions, and of bioturbation<br />
and sediment irrigation<br />
These need to be conducted in the AS and BoB, but also in other selected IO regions, from<br />
the abyssal plain to the continental shelf (spanning the OMZ), and should include seasonal<br />
comparisons (monsoon versus intermonsoon and interannual).<br />
Benthic sampling and experiments should be integrated with pelagic process studies to provide<br />
information on the amounts and nature of organic matter delivered to the sea floor (sediment<br />
traps) and to elucidate relationships and mechanisms in benthic-pelagic coupling. The logistical<br />
impediments to such integrated efforts (e.g. compatible cruise track and strategy, wire-time<br />
constraints, ship berthing capacity, etc.) can be significant and the time scales for studying<br />
surface-ocean phenomena and benthic community response are quite different. Therefore,<br />
pelagic-benthic collaborations that can be placed in the context of time series investigations<br />
at specific locations or exploit common infrastructures (e.g. instrumented mooring sites) stand<br />
the greatest chance of achieving success.<br />
For assessing organic matter losses between euphotic zone export and the underlying<br />
benthos, respiration rates in the mesopelagic realm are almost completely unknown. This is<br />
especially true in the OMZs, where extremely low dissolved oxygen concentrations make direct<br />
measurements of O 2 changes virtually impossible. All available rates are instead based on the<br />
indirect index of O 2 utilization, electron transport system (ETS) activity (Naqvi and Shailaja,<br />
1993; Naqvi et al., 1996). New methods, like non-invasive eddy correlation techniques (Berg<br />
et al., 2003) for estimating benthic O 2 flux, should be adopted<br />
Similarly, respiration rates need to be measured in deep sea sediments and in shelf/slope<br />
waters that are in contact with the OMZs. It is possible to determine O 2 consumption in<br />
sediments under low O 2 conditions (e.g. Law et al., 2009), however, new technologies and<br />
sensors are required. These include provision for better/constant power supply (long-life<br />
batteries) to power underwater monitoring and sampling devices. Results from such efforts<br />
have to be incorporated into new budgets for organic matter production and consumption for<br />
OMZ waters to better determine magnitudes and to resolve imbalances in previous budget<br />
calculations.<br />
Zoo p l a n k t o n st u d i e s<br />
Intensive process-oriented studies of zooplankton in the IO have mostly been focused in the<br />
AS (Smith, 2005), although reports on zooplankton distribution in the BoB (Fernandes, 2008;<br />
Jyothibabu et al., 2008) and Southern IO (Cornelia et al., 2009) have recently appeared and<br />
mesoscale eddies in the LC off west Australia have also been an area of recent study (Strzelecki<br />
et al., 2007; Waite et al., 2007). Within the AS, additional studies are needed to understand<br />
how zooplankton populations interact with and tolerate the OMZ and how these interactions<br />
might impact biogeochemical cycling. Are significant fluxes of elements (C, N and P) generated<br />
as a result of active zooplankton migrations in and out of the OMZ More generally, studies<br />
also need to be undertaken in the AS and elsewhere in IO basins to characterize species<br />
composition and seasonality of the resident populations. As discussed in Theme 4, the degree<br />
and spatio-temporal variation in grazing control of phytoplankton production in the AS remains<br />
an open question that needs to be addressed. In fact, the role of grazing is potentially an<br />
open question over vast areas of the southern tropical and subtropical IO, where modeling<br />
and remote sensing studies suggest that iron limitation may be an important limiting factor for<br />
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