Using a Remotely Operated Vehicle, researchers surveyed a large seamount in the Tyrrhenian Sea off the coast of Italy, finding three distinct biological communities. Seamounts, undersea mountains, can hugely affect the way water flows in an area and can provide hard substrate for benthic animals. These features are generally acknowledged to be potential hotspots in terms of how many species are in a given area (known as species richness).
Marzia Bo and colleagues1 detail the the species composition of the Vercelli Seamount in a paper appearing in PLoS ONE. Similar to other Mediterranean seamounts, the relatively shallow summit of Vercelli hosts kelp and algal-dominated communities at the very top (60-70 meters depth). A bit further down, from 70-80 meters, the southern flank of the seamount hosts mostly organisms that are well-suited for a high-flow environment, such as octocorals. Species found on the northern flank are adopted for lower-flow regimes and feed by active filter-feeding, for example, sponges and ascidians.
The study of seamounts, these seemingly esoteric oceanic peaks, is still very exploratory due to the difficulty in sampling in the open and deep ocean. Only a few hundred seamounts have been sampled biologically out of the estimated hundreds of thousands or millions thought to be present in the global ocean2. This work illustrates that seamounts can consist of multiple habitats over relatively little area. This is likely due to the different environmental conditions that are created by the feature itself, such as varying hydrodynamics (especially relevant here, with active and passive filter-feeders grouped), as well as slope and depth gradients. Bo et al. note that the conservation value of Vercelli should be focused on the variety of different communities the seamount supports and the diversity of life contained therein.
Though a seamount may have the impression of being remote and singular, the total global area represented by large seamounts is roughly equal to the size of Europe and Russia combined. This estimate is actually quite conservative and only takes into account seamounts with greater than 1500 meters in relief3.
This is an open-access paper; read the original work here.
The figures shown above are from Bo et. al. 2011 (cc).
1. Bo M, Bertolino M, Borghini M, Castellano M, Covazzi Harriague A, Di Camillo CG, Gasparini G, Misic C, Povero P, Pusceddu A, Schroeder K, & Bavestrello G (2011). Characteristics of the mesophotic megabenthic assemblages of the vercelli seamount (north tyrrhenian sea). PloS one, 6 (2) PMID: 21304906
2. Wessel, P, Sandwell, DT, & Kim, SS (2010). The global seamount census Oceanography, 23 (1), 24-33
3. Etnoyer, PJ, Wood, J, & Shirley, TC (2010). How Large Is the Seamount Biome?Oceanography, 23 (1), 206-209