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opportunist
Guembelitria
(Keller & Abramovich, 2009). The shading of sunlight reduced the
depth of the marine euphotic zone and affected water temperature. A thick cover by ash
dust probably lowered sea-water and Earth surface temperature. A less dense screen may
have resulted in a greenhouse effect, keeping the warmth of partially penetrating sun-light
from escaping into the atmosphere. Paleotemperature fluctuations in the latest Maastrictian
marine environments (Li & Keller, 1998) are accordingly related to fluctuations in the
intensity of the Deccan volcanic eruptions and world-wide dispersal of volcaniclasts.
The polyps of reef-building hermatypic
corals
house symbiotic zooxanthellae which are
involved in the precipitation of the calcareous skeleton and in other physiological processes,
but they can also become part of the coelenterate diet. Unlike in planktonic foraminifera
these symbiotic relationships observed on extant corals in the Great Barrier Reef of Australia
can be stopped for a while (coral bleaching) during which coral growth slows down while
the polyps feed on other algae and microorganisms, organic debris and bacteria (Vernon,
1993). This may explain the survival of some hermatypic coral groups, though a great deal
disappeared during the latest Cretaceous (MacLeod et al., 1997).
The fatal influence of the Deccan volcanism on the latest Cretaceous marine planktonic
microorganisms applies to marine and large terrestrial creatures as well. The darkening of
the atmosphere by dispersed volcaniclasts blurred the distinction between the annual
seasons controlling plant growth and blooming, as well as the biological clock of animal
reproduction, which provides a significant food source to carnivores after months of near
starvation. Seasonality controls the timing of sperm and egg spawning into the water, most
of which is consumed by predators awaiting this process. Mating and reproduction among
larger animals is coordinated with availability of food supply (plant and meat) which will
assure the survival and development of the young. Long-ranging darkness confused the
instincts and physiology of animals, reducing birth rate and hence food supply crucial for
predating mammals to feed the young as well as for reptiles and birds. The reduction in
birth rate (including the laying of eggs) immediately reduced the food supply. The
aggressive and large predators (mainly among the reptiles) were forced to consume part of
the prey that smaller predators used to eat, whereby the 'normal' food chain collapsed,
resulting in the intensive predation of the temporarily unprotected ones. These were
dinosaurs and pterosaurs eggs in nests on flat-land and their hatched young, as well as
mature ones sitting on the eggs, and other creatures which for a moment were careless. The
over-predation of this easy prey reduced the size of the victim's population which gradually
diminished until the remaining ones could not preserve the species, leading to extinction.
The organisms which were not affected by the collapse of the food chain were small
creatures which could escape and hide themselves or their brood such as crocodiles and
turtles which covered their brood, birds which laid the small eggs in between plants, small
mammals which could hide underground or among bushes, and amphibians and fishes
capable of hiding in aquatic environments. The darkening effect of the Deccan volcaniclasts
must have slowed down the metabolism of cold-blooded reptiles, among which were
probably some large dinosaurs. During the severe darkening they were completely unable
to defend themselves even from small predators. The selective elimination of the temporary
vulnerable ones is an extreme example of
natural selection
as the result of catastrophic
changes in the regular pattern of the long-operating ecological system in which organisms
and plants lived in harmony. The additional destructive effect of a single or multiple
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