For decades, marine biologists have attributed the widespread degradation of coral reef ecosystems primarily to global ocean warming. According to the standard thermal stress model, elevated sea surface temperatures disrupt the symbiotic relationship between corals and zooxanthellae—microscopic algae residing within coral tissues that provide essential nutrients through photosynthesis. When thermal thresholds are exceeded, corals expel these algae, resulting in bleaching and eventual mortality. Consequently, global climate mitigation has long been viewed as the only viable strategy for preserving reef habitats.
However, recent empirical research indicates that this conventional perspective oversimplifies reef dynamics by ignoring localized environmental stressors. A ten-year study of Caribbean reefs demonstrated that elevated nitrogen and phosphorus levels from agricultural runoff significantly lower the temperature threshold at which coral bleaching occurs. Excess nutrients stimulate macroalgal growth, increasing coral susceptibility to thermal stress. By showing that local pollution interacts synergistically with rising sea temperatures, these findings suggest that local watershed management—such as reducing fertilizer runoff—can provide coral reefs with critical resilience while broader climate initiatives are pursued.
Which of the following best describes the logical organization of the passage?
- It presents a prevailing explanation for a natural phenomenon, introduces new empirical evidence that qualifies that explanation, and highlights a practical application of the revised understanding.Answer
- BIt outlines a historical scientific consensus, details a series of experiments that completely disprove that consensus, and advocates discarding the original hypothesis entirely.
- CIt describes an environmental crisis, provides specific chemical data regarding agricultural runoff, and analyzes competing economic policies for marine preservation.
- DIt introduces a biological model, describes the physiological mechanism underlying it, and systematically refutes counterarguments raised by opposing researchers.
- EIt summarizes a conventional view on coral bleaching, contrasts it with a recent study, and concludes that global climate mitigation efforts are unnecessary.