Abstract
The Nazare submarine canyon extends similar to 210 km westward from the coast of Portugal, down to a water depth of > 4300 m. The considerable habitat heterogeneity found throughout the canyon is affected by strong currents and high turbidity, especially in the upper parts of the canyon. The canyon morphology comprises steep slopes, scarps, terraces, and overhangs, and a deeply incised thalweg is found in the lower part of the canyon. The seabed within the canyon is composed of varying proportions of rock and sediments that range from sand to fine mud. This great variation in physical environment is reflected by the varied fauna inhabiting the canyon. Diversity tends to decrease with depth, but there is also continual replacement of species with increasing water depth. Certain groups, such as the gorgonians and sea lilies, tend to be found on rocky surfaces, while large protozoans dominate the sediments at 3400-m depth. In addition to describing the fauna of Nazare Canyon, we discuss experiments undertaken as part of the HERMES project to elucidate the ecosystem function processes operating in the deeper parts of the canyon.
Highlights
Morpholo gy and Sedimentolo gy A wide variety of features contributes to the high morphological heterogeneity of Nazaré Canyon, and impacts its biodiversity
Thick sequences of muddy turbidites are presently accumulating on these terraces (Figure 2C), with sediment cores indicating accumulation rates of 0.4–1.4 cm yr-1 over the last few hundred years. This terraced area defines a distinct depocenter within the middle canyon, with little sediment passing beyond this zone to the lower canyon
The thalweg floor is comprised of coarse gravel and large boulders often draped with soft sediment that appears to be constantly reworked by tidally driven near-bottom currents
Summary
4000 m b y Paul T y ler , T eresa A mar o , R a q uel A r z o la , M arina R. C unha , H en kodeS ti g ter , A n d re wGood ay, V eerle H uvenne , J er o en I n g els ,. K o stas Kiria k o ula k is , Gal d eric L astras , D o u g las M ass o n , A na b ela Oliveira , A b i g ail Patten d en , A nn V anreusel , T jeer d V an Weerin g , JoaoV it o rin o , U rsula Witte , an d Ge orgeWo lff
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