The great variety of geological and hydrological conditions in the deep sea generates many different habitats. Some are only recently explored, although their true extent and geographical coverage are still not fully established. Both continental margins and mid-oceanic seafloors are much more complex ecologically, geologically, chemically and hydrodynamically than originally thought. As a result, fundamental patterns of species distribution first observed and explained in the context of relatively monotonous slopes and abyssal plains must now be re-evaluated in the light of this newly recognized habitat heterogeneity. Based on a global database of nematode genus composition, collected as part of the Census of Marine Life, we show that macrohabitat heterogeneity contributes significantly to total deep-sea nematode diversity on a global scale. Different deep-sea settings harbour specific nematode assemblages. Some of them, like coral rubble zones or nodule areas, are very diverse habitats. Factors such as increased substrate complexity in the case of nodules and corals seem to facilitate the co-existence of a large number of genera with different modes of life, ranging from sediment dwelling to epifaunal. Furthermore, strong biochemical gradients in the case of vents or seeps are responsible for the success of particular genera, which are not prominent in more typical soft sediments. Many

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The effects of 2 cold fronts on a shallow sublittoral system at the Island of Santa Catarina, southern Brazil, were investigated in June 2002. Atmospheric, pelagic and benthic data were taken daily covering the days before, during and after the passage of both fronts, for a total of 8 d of sampling. The passage of cold fronts, a short-term event, promotes changes in the entire shallow sublittoral ecosystem, i.e. both pelagic and benthic compartments. In the pelagic system, both fronts changed seston, nutrient and chl a concentrations. An increase in chl a just after the passage of the fronts probably resulted from phytoplankton retention and accumulation near the coast, from microphytobenthos resuspension and from an increase in nutrient availability. In the benthic system, sediment features and the 3 benthic components studied -microphytobenthos, meiofauna and macrofauna -were also affected by the passage of the cold fronts. The sediments at the site became more homogeneous. While mean grain size decreased, the fraction of fine sand gradually increased after the passage of the fronts. In contrast, sediment organic content was significantly higher immediately after the passage of the first cold front. Cold front effects in the benthos depended on the biological component, the vertical distribution of fauna and on the magnitude of the front. The sediment chl a concentration was lower exactly 1 d after the passage of the fronts, while phaeopigments were significantly higher. Both macrofauna and meiofauna, particularly nematodes, of the upper sediment layer exhibited a decrease in density and number of taxa during the passage of the first frontal system. The decrease in nematode abundance was mostly due to vertical migration to the deeper layers of the sediment, rather than being the result of erosion and transport during the passage of the cold fronts.KEY WORDS: Cold front · Short-term disturbance · Phytoplankton · Microphytobenthos · Meiofauna · Nematodes · Macrofauna Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 281: [79][80][81][82][83][84][85][86][87][88][89][90][91][92] 2004 blows from SW (in the cold sector) with a mean speed of 8 m.s -1 . Approximately 1 d after the passage of the front the wind returns to its predominant NE direction (see Fig. 1b).The surface wind field along the SBB is strongly influenced by the passage of frontal systems (Stech 1990). Considering that wind stress is one of the major low-frequency forcing mechanisms of the coastal circulation (Stech & Lorenzetti 1992), the frontal systems are expected to play a significant role in structuring the dynamics of shallow marine systems. However, effects of the passage of cold fronts on marine systems have thus far been inferred rather than documented (Odebrecht et al. 1995b, Sunyé 1999. This paper reports on the effects of the passage of cold fronts in a shallow sublittoral system of the Island of Santa Catarina, S Brazil. The study evaluates shortterm changes in abiotic and bio...

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