A species of holothurian, Pannychia, swarms a whale fecal mound in the abyssal Pacific.
When Miriam visited me last week at MBARI, we discussed over lunch my current “great” hypothesis. Every scientist has them…these are the hypotheses that are high on creativity but lack quantitative data to test them. Usually, the hypothesis is a “big idea”, virtually untestable, and the only support is anecdotal. It’s more of a thinking exercise rather than a formal hypothesis. Anyway my current “great” hypothesis is that food limitation in the deep sea drives adaptations that you would never see in other habitats. For example, communities like hydrothermal vents, methane seeps, and whale falls don’t exist in shallow water because food is easily obtained through other mechanisms. No need to acquire symbiotic chemosynthetic bacteria or the ability to utilize whalebone.
A degraded whale fecal mound from 2301m in the Pacific Ocean.
New findings by S. Khat et al. provide more evidence for my hypothesis. The paper actually describes findings originally made by Jean-Michel Cousteau (yes that Cousteau, and third author on the study) in 2006 on the Pacific Ocean floor west of Hawaii. From the paper’s abstract…
On February 6, 2006, we discovered an unusual assemblage of deep-sea animals associated with a well-preserved organic mounds at 2891 m depth 281 nautical miles west of Niihau in the Hawaiian Island Chain. Approximately 40 of the mounds, the larges 1.93m in length, were seen in submersible transects over an area of approximately 5km square. Utilizing two nuclear (18S and 28S rRNA) and two mitochondrial genes (COI and ND4), we determined that the organic mounds originated from Balaenoptera musculus. Several other gene sequences were also extracted from the samples and compared to sequences on GeneBank. Several of these sequences were consistent with typical prey items of the B. musculus (e.g. Euphausia pacifica, Thysanoessa inermis, Thysanoessa longipes, Thysanoessa spinifera, Nyctiphanes symplex and Nematoscelis megalops). This genetic evidence, and visual identification of the mounds by an expert, suggests that the mounds represent organic waste egested by B. musculus. Sample from 21 of the 40 fecal mounds indicates originations with at least 12 different individuals. Each mound is estimated to deliver approximately 200 kg of organic material to a typically food-limited seaﬂoor. Particularly noteworthy are the large number of opportunistic deep-sea species, and an abundance of unusual polychaetes. Two of these polychaetes, a spionid and a siboglinid, and a holothurian are new to science.
According to the paper, the “organic enrichment” increased biodiversity from an average of 61 species per meter square in the background to well over 100 species per meter square near the fecal mounds. The new holothurian (Sheril will be happy) is named Parastichopus stercus and is a member of the family of the warty sea cucumbers (right). Cousteau noted in the press release in Science Daily
“For sixteen months we have been waiting for this moment to share our findings of this unique habitat with the public. It is a very exciting time in which technology allows us to explore, previously inaccessible parts of the ocean. It is a very important time for us and the people who have put the pieces together painstakingly.”
A graduate student of Khat, Bethane Fessies who also authors the study noted “The samples were really foul smelling and fishy, most of us who sorted the samples weren’t able to eat for a couple of days.”
Khat, S., Fessies, B., Cousteau, J-M. (2008). Description of A New Deep-Sea Habitat Based On Whale Feces. Deep Sea Research Part I: Oceanographic Research Papers, 4(01), 401-401. DOI: 04.01/j.dsr.2008.04.01