Effects of watershed and in-stream liming on macroinvertebrate communities in acidified tributaries to Honnedaga Lake, NY

Liming techniques are being explored in many regions as a means to accelerate the recovery of aquatic biota from decades of acid deposition. The preservation or restoration of native sportfish populations has usually been the impetus for liming programs, and as such, less attention has been paid to its effects on other biological assemblages such as macroinvertebrates. In 2012, a program was initiated using in-stream and aerial (whole-watershed) liming to improve water quality and Brook Trout (Salvelinus fontinalis) recruitment in three acidified tributaries of a high-elevation lake in New York State. Concurrently, macroinvertebrates were sampled annually between 2013 and 2016 at 3 treated sites and 3 untreated reference sites to assess the effects of each liming technique on this community. Despite improvements in water chemistry in all three limed streams, our results generally suggest that neither liming technique improved the condition of macroinvertebrate communities. The watershed application caused an immediate and unsustained decrease in the density of macroinvertebrates driven largely by a one-year reduction of the acid-tolerant Leuctra stoneflies. The in-stream applications appeared to reduce the density of macroinvertebrates, particularly in one stream where undissolved lime covered the natural substrate. The inability of either liming technique to improve the condition of macroinvertebrate communities may be partly explained by the persistence of acidic episodes in all three streams. This suggests that in order to be effective, liming programs should strive to eliminate even temporary episodes of unsuitable water chemistry.