Pelagic food web models were constructed for 28 acidic (pH < 5.0) Adirondack Mountain lakes, and multiple regression analyses were done to quantify relationships between abiotic variables (DOC, monomeric Al, total P, and H+ concentrations and lake area) and three food web attributes (number of species, number of links, and links per species) Regression models contained log DOC and H+ as significant predictors of food web structure. The models explained over 35% of the variation in species, links and links per species; most of the variation was explained by log DOC. Species, links and links per species increased as DOC increased from <2 to roughly 4 mg∙L−1. At higher DOC levels, the food web attributes reached plateaus at 35 species, 120 links, and 4 links per species. The results support the view that in acidic lakes, DOC ameliorates the toxic effects of Al, so that above a saturating DOC level of approximately 4 mg∙L−1, Al-sensitive biota can exist in acid waters. Hence, food webs of high DOC acid lakes are larger and more complex than their low DOC counterparts.
Effects of warming and shifts of pelagic food web structure on benthic productivity in a coastal marine system