For decades, benthic ecologists assumed that the deep-sea floor was a biological desert, largely devoid of localized organic abundance and dependent solely on a faint, steady drizzle of microscopic marine particulate known as marine snow. This paradigm began to shift significantly with the discovery of "whale falls"—the carcasses of large cetaceans that sink to the abyssal plain. Rather than serving merely as fleeting nutritional windfalls, these biological depositions initiate complex ecological successions that can persist for decades, functioning as ephemeral evolutionary stepping stones across vast, nutrient-poor marine expanses.
Upon settling, a whale carcass undergoes three distinct ecological stages. In the initial mobile-scavenger phase, lasting up to two years, large necrophagous fauna such as sleeper sharks, hagfish, and lysianassoid amphipods rapidly strip the soft tissues. Once the soft tissue is depleted, the opportunistic phase commences, during which dense populations of bone-eating polychaetes, mollusks, and crustaceans colonize the sediment and remaining organic matter. The third and longest phase, the sulfophilic stage, can endure for over a half-century. During this period, anaerobic bacteria within the lipid-rich skeletal matrix break down bone lipids, producing hydrogen sulfide. This byproduct sustains chemosynthetic microbial mats and endosymbiotic invertebrates remarkably analogous to organisms inhabiting hydrothermal vents and cold seeps.
Some marine theorists previously argued that whale fall assemblages are merely incidental aggregations of generalist deep-sea scavengers with little bearing on broader speciation dynamics. However, contemporary phylogenetic analyses demonstrate that numerous specialized taxa inhabiting cold seeps and vents evolved directly from ancestors that adapted to sulfophilic whale bones. Consequently, the ecological role of sunken cetaceans extends far beyond local nutrient enrichment; they constitute essential biogenic islands that facilitate deep-sea biodiversity and macroevolutionary dispersal across ocean basins.
Which one of the following most accurately expresses the main idea of the passage?
- AThe mobile-scavenger and opportunistic phases of a whale fall rapidly consume soft tissues, leaving behind lipid-rich bones that provide temporary sustenance for generalist scavengers.
- Sunken whale carcasses initiate a prolonged, multi-stage ecological succession that not only supports unique local communities but also plays a vital role in deep-sea speciation and dispersal.Answer
- CWhale falls represent incidental gatherings of generalist scavengers that have negligible influence on long-term macroevolutionary processes across ocean basins.
- DDeep-sea hydrothermal vents and cold seeps depend almost entirely on hydrogen sulfide produced by the decomposition of whale skeletons to support their microbial communities.
- EThe breakdown of bone lipids by anaerobic bacteria during the sulfophilic stage is the primary mechanism that prevents deep-sea floors from becoming biological deserts.