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One could also make the opposite argument, that these species
lists and identities were based on morphological species -- preserved
animals brought into the laboratory and identified under the microscope --
whereas it was becoming increasingly evident from molecular studies that
many of the populations identified as a single species based on morphology
were actually multiple-species complexes. Molecular genetics based on
DNA sequences showed much greater diversity and much more restricted
species distribution than biologists had been led to believe from
morphology-based taxonomy, so from that perspective the percentage of
endemics could be much higher. Until proper studies were conducted to
look at the molecular genetics of species ranges, it would not be known
whether predictions of the levels of species turnover across the region were
conservative or otherwise.
Temporal variability
It was increasingly evident that, on a variety of scales -- seasonal,
interannual, sometimes decadal and even multidecadal -- the productivity
regime in the North Pacific Ocean including the CCFZ was changing over
time. As the amount of organic carbon sinking to the seafloor and the deep
sea changed, community structure was also likely to vary. To understand,
predict and monitor the effects of mining, those effects would have to be
distinguished from natural temporal variability.
Citing data from a number of stations across the central North
Pacific, from the slope off California to the North Pacific central gyre, Smith
noted that the amount of oxygen respired varied over relatively short time
scales, as did POC flux. There was also evidence of longer time scales of
variability, including major changes on a decadal scale in the productivity of
the North Pacific Ocean. North Pacific salmon catches off Alaska and
Washington had shown major shifts about 1976-77 and again in 1985-86,
related to long-term climatic changes and primary production of POC flux.
Similar changes in productivity on decadal time scales were also likely to be
impacting the CCFZ. For example, they affected the lobster fishery in Hawaii,
the survivorship of monk seals and many components of the pelagic food
web. While salmon offered the most elegant example, it was likely that
decadal time-scale variations in the flux of POC to the seafloor in the CCFZ
would result in temporal variability in the abundance and potentially the
species structure of seafloor ecosystems.
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