Three terms describing pond bottom soils are used here and in the technical literature.
The term ‘‘sediments’’ is used in the limnological and oceanographic literature pertaining
to the fact that bottom of lakes and oceans are made mostly of materials sedimenting from
the water during long periods of time. Ponds are constructed in native soils, having bottom
soils. Later, both the sedimentation of plankton and feed residues as well as the scouring of
loosely consolidated soil and deposition of fine particles on the bottom, leads to a change
in the properties of the bottom soil. Often, one finds in the stagnant or deeper parts of the
pond an accumulation of very soft loose material, relatively rich in organic matter that is
often called sludge. Sediments accumulating in lined ponds, having high organic matter
concentrations would also be defined as sludge. There is a continuum from bottom soil,
through sediment to sludge. In this work, the terms bottom soil and sediment will describe
the bottom of the pond, while the term sludge will be used specifically to the soft,
fluidized, organic-rich residue.
This manuscript is a literature review of the physical, biological and chemical processes
occurring at the pond bottom that influence aquaculture production, giving special
attention to shrimp culture including supporting data obtained in fish ponds. In addition,
potential technologies to mitigate problems occurring at the soil–water interface in ponds
are discussed.