The fishes of the Pine Barrens are beautiful and distinctive. These species, which are so characteristic of blackwaters on the Atlantic Coastal Plain, rarely occur in nearby clearwaters.
Blackwaters have high concentrations of humic substances, which stain the water dark brown.
The humic substances come from the decomposition of lignin, the molecule that makes woody plants woody. In the Pine Barrens, much of the humic substances come from lignin in pine needles. Humic substances interfere with the transmission of light through water, and so floating and emergent macrophytes are the most important primary producers in blackwaters. Most blackwaters are also acidic. The Pine Barrens lies on the Cohansey Sand, a sedimentary deposit having very low buffering capacity.