A second example concerns the sustainability of baleen whales in relation to the availability of plankton and krill. Baleen whales constitute a particularly interesting example in that they simultaneously point to the importance of the ecological relationships among different species at different scales, as well as to the importance of considering the temporal complexity of these processes. Most species of whales are migratory, with complex migratory patterns across the oceans, sometimes spanning more than half the planet. These patterns are fairly well-known across a relatively long span of history, not only through the efforts of scientific research and data collected by nongovernmental organizations, but also through many detailed records of whales' movement of that were collected by the whaling industry during the 18th and 19th centuries.
The migratory movement of whales tends to be coupled with the availability of nutrition. The main source of nutrition for baleen whales is krill. Krill, in turn, depend on plankton as their main source of nutrition. If ocean waters become too warm, plankton populations tend to expand to the point where they are poisoned by their own metabolic processes. Without plankton, krill populations are not sustainable, and, consequently, baleen whales may find themselves deprived of their main source of nourishment. In recent years, it has been reported that warmer ocean waters have affected the level of krill available to whales.
This example sheds light on the complexities of scale and time that are inherent in patterns of inter-species relations in an ecosystem. While ecosystems may become toxic from the perspective of the scale of plankton, they may not be toxic from the perspective of the scale of larger species, such as baleen whales. However, baleen whales are still affected, because their survival relies on a food chain in which plankton play a crucial role.
This example also raises the issue of temporal complexity in ecosystems. Whales live for several decades, on average 70-80 years. Therefore, understanding the long-term effects of krill deprivation will require years of systematic investigation and data analysis. As there are other factors that affect the health state of whales, scientists will have to consider which of these other factors may accentuate or attenuate the effects of the lack of krill-based nutrition on whales.
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