A Comparative Analysis of the Macrofaunal Communities Associated with Whale, Wood, and Kelp Falls on the Deep Sea Floor

Abstract

The term food fall is used to refer to whale carrion and large parcels of wood and kelp that sink to the bottom of the ocean. • Organic flux to the deep sea floor in the form of large food falls is a defining factor in habitat-variation for the deep sea benthos. • Pulses of organic enrichment such as food falls impact the ecology of the deep ocean bottom by providing the ocean floor with an episodic source of large-scale enrichment. In doing so, large food falls foster highly productive, distinct, and highly populated patch-communities. Collectively, these patches augment overall deep-sea diversity via deep sea patch dynamics. • Falling detrital material and reduced compounds derived from chemautotrophy replace sunlight as the primary energy source in these deep benthic zones (Duxbury et. al., 1998). Primary production: Photosynthesis CO2 + H2O ⇒ [CH2O] + O2 Chemosynthesis (aerobic)CO2 + H2O + H2S + O2 ⇒ [CH2O] + H2SO4 • Whale, wood, and kelp falls harbor free-living bacteria, tube worms, molluscs, and several other species that prosper without the benefit of photosynthesis. • The chemosynthetic energy production that occurs hydrothermal vents and cold water seeps also occurs at food falls. • Rare species that had previously been considered endemic to vent and seep communities have been discovered in food fall communities. • It is theorized that whale, wood, and kelp falls acted as the intermediary “stepping stones” that linked the deep water and shallow water habitats (Distel et. al., 2000). • The genetic crossover between different food fall and vent/seep animals supports the hypothesis that vent, seep, and food fall habitats could foster evolutionarily linked parallel bottom communities. At present, whale falls are known to share 11 species with hydrothermal vents and 20 species with cold seeps, and genetic analysis and comparisons of wood and kelp fall animals have yet to be done (Smith and Baco, 2003). • The examination of whale falls, wood falls, and kelp falls provides an insight into the population dynamics and the evolution of deep sea macrofaunal communities.