Geoscience Reference
In-Depth Information
linked to loss of benthic biodiversity. They also indicate one possible consequence, a re-
versal of the energy flow in the ecosystem towards microbial levels. These results suggest
that a reduction in functional biodiversity may be associated with an exponential decline in
the ecosystem processes.
The significance of these findings may be highlighted by recalling the discovery of
deep-sea vents in the 1970s and the subsequent documentation of rich and diverse com-
munities of organisms in the deep sea. The discovery of ocean vents, where hot gases erupt
from the ocean floor, changed our understanding of life. The gases support a surprisingly
activelifeandecosystem,whichdoesnotuselightandphotosynthesis,butdependsonbac-
terial processes for organic production. Further discoveries in the 1980s documented life at
cold methane seeps, which use methane as the energy source. Thus the deep-sea ecosys-
tem has a rich diversity. The 'surprise' discoveries referred to highlight the importance of
avoiding 'surprise' disruptions of deep-sea ecosystems through lack of understanding and
adequate management of human interferences.
The key factors influencing the degree of ecosystem degradation in hypoxia are dur-
that 'currently hypoxia and anoxia are among the most widespread deleterious anthropo-
genic influences on estuarine and marine environments and now rank with over-fishing,
habitat loss and harmful algal blooms as major global environmental problems'. Manage-
ment restrictions of nutrient inputs have improved conditions in some cases, for instance
rivers in the eastern USA and in the UK, but have not improved conditions in the Ches-
apeake Bay in eastern USA. Reduction of nutrient inputs from fertilizing the land is re-
quired, at least to levels around those of the 1950s, thus before the time of the spread of
eutrophication. This situation could be seen as in parallel with the need for a reduction in
atmospheric greenhouse gas levels.
The development of dead zones is also strongly coupled with the physical conditions
in the water column: the stratification, the mixing, temperature, water exchange, circula-
tion, and the air-sea interaction. The potential effects of climate change can influence these
