Effects on periphyton and macroinvertebrates from removal of submerged wood in three Ontario lakes

Abstract

We removed 40%–70% of nearshore wood habitat from three lakes to test the link between habitat and productive capacity, specifically focusing on the provision of substrate for periphyton and invertebrate production by submerged wood. Our objectives were fourfold: (i) to calculate the total amount of invertebrate and periphyton biomass removed with the wood; (ii) to explore wood's value as habitat for invertebrates and periphyton; (iii) to determine the response within residual epixylic periphyton and invertebrate biomass; and (iv) to assess interactions between periphyton and invertebrates and other factors that may influence wood's productivity. Invertebrate biomass was greater on wood than in sediment, but the total available sediment area exceeded that of wood, thus a relatively small proportion of overall productivity was lost. Highly decayed wood supported greater chlorophyll a concentrations and more invertebrate biomass and diversity than fresh wood. The removal had no measurable effect on whole-lake water chemistry, nor did it result in a response in residual epixylic periphyton and invertebrate biomass. We conclude that we permanently reduced a dynamic and concentrated biomass of primary and secondary productivity in lakes by removing submerged wood habitat.