Experimental evidence for aging food patches as a factor contributing to high deep‐sea macrofaunal diversity

Abstract

To determine whether deep‐sea macrofaunal succession is observed in response to small‐scale patches, we deployed colonization trays at 900‐m depth for 23 d and 28 months. Treatments included sediment that was unenriched or enriched with Sargassum natans. Short‐term Sargassum trays contained significantly higher and short‐term unenriched trays significantly lower total densities than the ambient sediment. Both Sargassum treatments attracted high densities of a low‐diversity fauna, but they differed in species composition. Short‐term, unenriched trays attracted low densities of a high‐diversity fauna, and long‐term unenriched trays attracted high densities of a moderately diverse fauna. All treatments showed low faunal affinity with the ambient community. In a 19‐d experiment with S. natans incubated in situ or in sterilized seawater, different species dominated. Thus, differences between 23‐d and 28‐month Sargassum trays may have been related to changes in the food source; a succession of different species colonize aging patches, indicating that patch age may be an important source of microheterogeneity for deep‐sea macrofauna.

Macrofaunal colonization across the Indian margin oxygen minimum zone

“…Other relatively short-term colonization experiments using a similar tray apparatus have yielded a variety of results. In a 23 day experiment in the Northwest Atlantic, macrofaunal densities in Thalassiosira and Sargassum-enriched trays reached 66 450 ind m −2 and 16 000 ind m −2 , respectively, greatly exceeding ambient densities (Snelgrove et al, 1994(Snelgrove et al, , 1996. However, the unenriched controls did not exhibit the same ambient density overshoot seen in the enriched trays (Snelgrove, 1994(Snelgrove, , 1996.…”

“…The colonization trays consisted of an 11.1 cm diameter central cup (9 cm deep) lined with 20 µm mesh, surrounded by a flat delrin nylon collar 40 cm in diameter. The design of the colonization trays is described by Levin and DiBacco (1995) and is identical to those used by Snelgrove et al (1992Snelgrove et al ( , 1994Snelgrove et al ( , 1996 in the Atlantic Ocean and Levin et al (2006Levin et al ( , 2013 in the Pacific Ocean. The broad collar is designed to reduce turbulent flow over the central cup and prevent scour.…”

“…In a 23 day experiment in the Northwest Atlantic, macrofaunal densities in Thalassiosira and Sargassum-enriched trays reached 66 450 ind m −2 and 16 000 ind m −2 , respectively, greatly exceeding ambient densities (Snelgrove et al, 1994(Snelgrove et al, , 1996. However, the unenriched controls did not exhibit the same ambient density overshoot seen in the enriched trays (Snelgrove, 1994(Snelgrove, , 1996. Macrofauna in the Indian margin exhibited a density overshoot at 1147 m but it was not correlated with the presence of phytodetritus and the overshoot was not as extreme as that observed in previous studies.…”

“…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).…”