Life in the shelf seas - Introduction to the Physical and Biological Oceanography of Shelf Seas - page 129

5

Life in the shelf seas

Much of the physics in the preceding chapters can be traced back to the
fundamentals of fluid flow encapsulated in the equations of motion and continu-
ity, along with the eddy description of turbulence. By contrast, describing the
basics of life in the sea presents us with the difficulty of trying to distil a broad
set of concepts from a system which is inherently very complex. Our experience
of working at sea alongside biologists has been stimulating and fruitful, but
there is always a tension: physicists can get exasperated at the complexity of the
systems that biologists like to describe, while the biologists roll their eyes at the
physicists' insistence on boiling problems down to as simple a level as possible.
In this chapter we will take more of a physicist's view of biology in the ocean,
focusing mainly on those aspects of the biology that are relevant to understand-
ing how organisms' access to resources and growth are controlled by the
structure and motion of the fluid environment.
Broadly, we are aiming to understand how organic compounds are produced
in the ocean, and their fate. The schematic illustration of Fig. 5.1 provides us
with a framework for the chapter; you could also have a look at the final
schematic in Fig. 5.19 if you would like some idea of the details that we will
be adding to this framework. We will begin by describing the fundamental
biochemistry that lies at the heart of the growth of the , the single-

celled, photosynthesising phytoplankton which produce the organic matter and
so power both the rest of life in the ocean and the cycling of carbon. In contrast,
the

autotrophs

consume organic material, either recycling it back to inorganic
matter or passing it further up the food chain by being food for larger hetero-
trophs. Heterotrophs are much more varied in form and in their methods used for
finding and consuming their prey, so instead of trying to detail this variety we
will identify their broad roles in the ecosystem and some of the constraints
that life in a turbulent fluid imposes on them. The biological processes that we
will describe are in general common to the open ocean and to the shelf seas.
We will use shelf sea examples to illustrate the processes, and identify where the
important contrasts are between shelf and open ocean biology.

heterotrophs