THE IMPACT OF IRON SMELTING ON OCTOBER CADDISFLY CASES FROM KNOB BROOK, IRONVILLE, NY

October caddisflies live on rocks in streams and lakeshores and are considered indicator species. Throughout their larval stage, caddisflies use materials they find in their habitat and build a protective tubular case to pupate. Studying their cases is an exercise that merges together mineralogy, chemistry, and sedimentology since the particles they use vary in size, media, and angularity depending on what the habitat has to offer. Through the use of a binocular microscope and an SEM equipped with EDS, it was determined that the healthy population of caddisflies in Knob Brook are not adverse to using slag in their cases, but seem to prefer geological materials.

Knob Brook is a small stream in Ironville, NY which is located in the SE region of the Adirondack Mountains. The sediments in this waterway are composed of lithic fragments from the Adirondack granitoids and metamorphics as well as mineral grains of quartz, k-spar, magnetite, mafics, and slag fragments. Slag is a byproduct of iron smelting which took place in Ironville from 1882 to 1886. The presence of slag in the bed load of Knob Brook is unsurprising since the brook bisects the slag pile. Ironville slag is predominantly glassy and is chemically dominated by SiO₂ and CaO (making up a total of ~82 wt. % oxide). MgO, FeO, and K₂O and Al₂O₃ are also present but in much smaller amounts. The most concentrated trace elements are Sr, Y, Zr, Cu and Ba.

The October caddisfly cases of Knob Brook contain angular to subangular sand-sized grains that reflect the geology of the stream sediments and contain very few slag particles. What is refreshing to note is that in a stream heavily impacted by industrial activities, there is a thriving caddisfly population and that the presence of slag does not appear to have an adverse effect. This type of study could be applicable to other industrially disturbed sites where caddisflies are present or when their cases are found in sediment samples.