Compositional Data Analysis as a Potential Tool to Study the (Paleo)ecology of Calcareous Nannoplankton from the Central Portuguese Submarine Canyons(W off Portugal)
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Submarine canyons are deep and steep incisions on the continental margins. The physical forcing
mechanisms linked with these marine systems, such as the enhancement of upwelling and bottom
sediment resuspension, are expected to provide a nutrient source that will increase phytoplankton
density (Hickey, 1995, Kampf,2006).
Coccolithophores are the predominant phytoplanktonic group within the calcareous
nannoplankton and their sensitivity to a variety of surface water environmental parameters makes
them important markers of oceanographic processes and proxies of sea surface water masses and
temperatures, productivity and past climate changes (e.g. Ziveri et al., 2004; Silva et al., 2008).
In the present work we propose to test compositional analysis (Buccianti & Esposito, 2004;
Pawlowsky-Glahn & Egozcue, 2006) as a tool to: a) achieve a clearer distinction between
opportunistic coastal-neritic species (r-strategists) and typical oceanic species (k-strategists) in the
central Portuguese margin, and b) to identify a coccolith assemblage that might reflect favorable
environmental conditions found in the vicinity of the canyon that promotes the productivity of
calcareous nannoplankton. Our main difficulty will be in distinguishing the ecological signal from
the effects of other environmental factors mentioned before (i.e. advection, dissolution, bottom
resuspension). One way to infer the species’ ecological inter-relationships is by determining species
relative percentages. The main concern is how the closure problem and the inconsistency of
percentage determinations will affect our results. Compositional analysis was designed to provide
more reliable and thus representative results, since the inference made on the coccolith assemblage
features from which the data are drawn is correctly performed from a theoretical point of view
(Buccianti & Esposito, 2004). Here, we present the first insights from applying compositional data
analysis to coccolith assemblages from 85 surface sediment samples collected from the central
Portuguese margin
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