NO DIRECT EFFECT OF FRESHWATER ‘BROWNING’ ON LARVAL FISH FORAGING
Many freshwater ecosystems are becoming browner in color due to increased inputs of terrestrially-derived organic matter. This ‘browning’ has the potential to decrease fish foraging due to a reduction in light for visual predation. We conducted laboratory feeding experiments to compare the selectivity and efficiency of larval fish preying on zooplankton across a gradient of brown water. Moreover, larvae were collected from lakes of varying transparency to determine if fish currently living in brown systems are better adapted to ‘browning’ than fish from ‘blue’ waters. Fish were placed in tanks with artificial lake water and increasing concentrations of SuperHume (absorbance at 440 nm = 1.4 – 9.6 m<-1>). An equivalent number of zooplankton was introduced to each tank, and fish were allowed to feed for 10 - 30 minutes. After which, the fish were removed and the remaining zooplankton were collected, preserved, and enumerated. Surprisingly, no significant difference in foraging selectivity or efficiency was observed across our brown water treatments, regardless of the color of the lake in which the fish were collected. Based on previous research, ‘browning’ appears to more negatively affect larval fish indirectly through food web dynamics.
Troy Clift (Primary Presenter/Author), Longwood University, firstname.lastname@example.org;
Jacob Spain ( Co-Presenter/Co-Author), Longwood University, email@example.com;
Dina Leech ( Co-Presenter/Co-Author), Longwood University, firstname.lastname@example.org;