Fertilizing naturally placid waters with nutrients is essentially
changing the food web structure. You're changing the nutrient concentration
but not changing the turbulence in a corresponding manner. By adding
nutrients to naturally placid waters you are not mimicking fertilization
by natural turbulence. The point is that it's difficult to predict
what would happen with nutrient additions to these waters. But there
are ocean areas that are analogs to high-nutrient, low-turbulence
situations, for example in regions of coastal eutrophication. Those
situations can promote a different assemblage of phytoplankton,
some of which are toxic species or are species that hog the nutrients,
and are not readily eaten by fish or the grazers that lead to fish
you fertilize the ocean to sequester carbon, you definitely change
the food web structure. It's not something that might happen. If
you don't change food web structure, you don't sequester carbon.
An important point to remember from Jon Cole's earlier talk on lakes
is that changing the food web is very unpredictable, and strongly
dependent on time-scale.
possible consequences of adding nutrients to ocean systems are reduced
oxygen in the deep sea, which can increase methane production, and
increased denitrification. Both processes can release greenhouse
gases to the atmosphere (methane and nitrous oxide) that are more
potent than CO2.
Another important consequence of nutrient additions to surface
water is to decrease the water transparency. When phytoplankton
bloom, the water becomes murky and less sunlight penetrates to depth.
If nutrient enrichment influences coastal waters, or waters over
coral reefs, the lack of sunlight would starve bottom habitats with
some very important ecological consequences.
The bottom line is that ideas are being explored, but there are
uncertainties about what might happen ecologically.
take a step back and talk about calculating potential carbon credits
from ocean sequestration. It's clear that the procedures for calculating
carbon credits are anything but settled. First, simple calculations
will not work.