The role of food patches in maintaining high deep‐sea diversity: Field experiments with hydrodynamically unbiased colonization trays

Abstract

To test whether deep‐sea macrofaunal diversity is enhanced by specialization on small‐scale food patches, we deployed colonization trays by submersible at 900‐m depth for 23 d. Trays were buried flush with the seafloor to minimize potential hydrodynamic bias. Treatments included prefrozen, natural sediment that was unenriched or enriched with either Thalassiosira sp. or Sargassum sp. Density comparisons and rarefaction analysis indicate that Thalassiosira sp. attracted high densities of several taxa of juvenile opportunists, and Sargassum sp. trays were colonized by fewer individuals of a more diverse fauna. Ambient faunal diversity was higher and densities lower than enrichment treatments, although unenriched trays did not attain ambient densities. Results suggest that juveniles, rather than adults, specialize on specific patch types, thus contributing to high deep‐sea diversity; this bottleneck may be fundamentally different from less diverse, shallow‐water macrofaunal assemblages.

Macrofaunal colonization across the Indian margin oxygen minimum zone

“…Colonization experiments in the low-oxygen Santa Catalina Basin also yielded assemblages containing a significant proportion of ambient fauna (Levin and Smith, 1984). In contrast, early colonization tray experiments in the Atlantic revealed abundant, opportunistic colonizers that were often rare in ambient sediments (Desbruyères et al, 1980;Grassle and Morse-Porteous, 1987;Snelgrove et al, 1992). These included capitellid, hesionid, dorvilleid, spionid, and sigalionid polychaetes, cumaceans and leptostracans.…”

“…The type of food present also affected colonization. In the Atlantic, trays containing the diatom Thalassiosira attracted significantly more colonists than those containing the seaweed Sargassum (Snelgrove et al, 1992(Snelgrove et al, , 1994. On the Pakistan margin, consumers of phytodetritus varied as a function of oxygen regime (Woulds et al, 2007(Woulds et al, , 2009, with protists dominating phytodetritus consumption at O 2 concentrations below 0.1 mL L −1 (4 µM) and macrofauna dominating at slightly higher oxygen levels.…”

“…Temperature, salinity and % POC data are taken from Hunter et al (2012); these authors made measurements at identical study sites at the same time. seamounts (Levin and DiBacco, 1995), increased quantity of organic matter (Levin and Smith, 1984;Menot et al, 2009), and preferred food types (Snelgrove et al, 1992). Six-month exposures of defaunated sediments on seamount and slope habitats in the NE Pacific have shown recovery rates of 50 to 75 % of ambient densities, with most individuals belonging to taxa present in ambient cores (Levin et al, 2006;Levin and DiBacco, 1995), whereas sediment trays collected after only 7 weeks yielded densities as low as 6 % of ambient levels in coarse-grained seamount sediments (Levin and DiBacco, 1995).…”

“…The stability of different patches in the deep sea was thought to allow for more specialization than in shallow water and to promote succession (Snelgrove et al, 1994). Longer-term (6 months to > 1 yr) colonization experiments in the deep sea have been performed to determine which taxa are the most efficient colonizers in a given area and to observe the effect of variable food type (Grassle and Morese-Porteous, 1987), organic matter quantity and quality (Snelgrove et al, 1992(Snelgrove et al, , 1994(Snelgrove et al, , 1996Menot et al, 2009), hydrodynamics/current and terrain, (Levin and DiBacco, 1995), and sulfide present in sediments (Levin et al, 2006;Menot et al, 2009).…”

Baseline biogeochemical data from Australia's continental margin links seabed sediments to water column characteristics

“…Sediment percentage total organic carbon (%TOC) concentrations are the most widely available sedimentary parameter for representing the flux of particulate OM (POM) to the sea floor (Seiter et al 2004;2005), which exhibits significant regional variability (Lutz et al 2002). These concentrations can be a useful measure of resources available to support benthic biota (Snelgrove et al 1992) because positive relationships have been observed between %TOC and benthic biodiversity (Snelgrove and Butman 1994;Snelgrove et al 1996). %TOC is often inversely correlated with grain size (Mayer 1994;Keil et al 1997) because ,99% of sedimentary OM occurs in fine fractions as discontinuous blebs on clay surfaces (Ransom et al 1997).…”