Ecosystem effects of dense water formation on deep Mediterranean Sea ecosystems: an overview

Abstract

Natural episodic events, such as gravity flows, submarine landslides, and benthic storms can determine severe modifications in the structure and functioning of deep-sea ecosystems. Here, we report and compare the ecosystem effects produced by dense water formation events that occurred in the Gulf of Lions (NW Mediterranean) and the Aegean Sea (NE Mediterranean). In both regions, the rapid sinking of cold dense waters, driven by regional meteorological forcings, results in important immediate modifications that can be summarised in: (i) increased organic matter content in the deep basin; (ii) diminished benthic abundance; and (iii) changes of benthic biodiversity. At longer time scale the analysis reveals, however, different resilience times in the two regions. The Gulf of Lions is characterized by a very fast (months) recovery whereas the Aegean Sea shows much longer (45 years) resilience time. New long-term studies are further needed to identify the potential effects that changes in the duration, intensity and frequency of episodic events could have on the structure, biodiversity and functioning of the deep Mediterranean Sea under environmental and climate change scenario

Marine litter on the floor of deep submarine canyons of the Northwestern Mediterranean Sea: The role of hydrodynamic processes

“…5 in Canals et al, 2013). During offshore convection events organic matter from the photic zone is transferred to the deep basin and fine, loose deep-sea floor sediments are remobilized (Pusceddu et al, 2010;Stabholz et al, 2013).…”

Species richness, species turnover and functional diversity in nematodes of the deep Mediterranean Sea: searching for drivers at different spatial scales

“…The data presented here suggest that species richness and beta diversity have opposite patterns in the deep Mediterranean Sea: species richness is significantly greater in the western Mediterranean than the eastern Mediterranean, whereas beta diversity is higher within the eastern Mediterranean than the western Mediterranean. These patterns might be the result of the effects of different environmental characteristics (topography and trophic conditions), the history and environmental events (episodic events and climate change, with different spatial extension and intensity) that characterize these two basins (Danovaro et al, 2004(Danovaro et al, , 2008bCanals et al, 2006;Gambi & Danovaro, 2006;Pusceddu et al, 2010Pusceddu et al, , 2013. All of these environmental factors probably have different effects on the biodiversity attributes in the western and eastern Mediterranean basins.…”

“…However, recent evidence has suggested that this ecosystem is much more temporally and spatially variable than previously thought, with potentially important implications for biodiversity patterns (Lampitt et al, 2010;Pusceddu et al, 2010Pusceddu et al, , 2013Rex & Etter, 2010). Several mechanisms have been invoked to explain the spatial patterns of biodiversity: (1) sediment grain size and substrate/ habitat heterogeneity (Etter & Grassle, 1992;Danovaro et al, 2009Danovaro et al, , 2010Bongiorni et al, 2010;McClain & Barry, 2010;Vanreusel et al, 2010;Zeppilli et al, 2012); (2) productivity (Smith et al, 2008;Lampitt et al, 2010;Tittensor et al, 2011;McClain et al, 2012); (3) food resources (Danovaro et al, 2008b;Gambi et al, 2010); (4) oxygen availability (Diaz & Rosemberg, 1995); (5) water currents (Lambshead et al, 2001); and (6) occasional catastrophic disturbances (Levin et al, 2001;Pusceddu et al, 2010Pusceddu et al, , 2013. Nonetheless, all of these factors are subjected to strong scientific debate because they are often sitespecific and constrained by local (or regional) conditions (Levin et al, 2001).…”

On and off the beaten track: Megafaunal sessile life and Adriatic cascading processes

“…Besides such physical responses, DSW cascading events reverberate also on ecosystems Puig et al, 2008aPuig et al, , 2013Würtz, 2012), impacting on the nutrient cycle by increasing organic matter availability at depth, modifying the local biodiversity, and temporarily altering the trophic state of the deep-sea benthic communities (Pusceddu et al, 2010Dell'Anno et al, 2013). A recent study suggests that DSW cascading events in the north-western Mediterranean are directly correlated with fluctuations in the populations of the commercially-valuable deep-sea shrimp Aristeus antennatus (Company et al, 2008).…”