Space and Productivity may be Co-limiting Factors for Bay and Marsh Detrital Invertebrates

University Hall, Rm 134

By fragmenting and urbanizing habitats, humans are reducing the amount of area available for species. To predict how these reductions in area impact species diversity and activity, we must understand Species-Area Relationships (SARs), which predicts species abundance and diversity based on habitat size. SARs are difficult to examine in decomposer systems because decomposer habitat (detritus) is also their food making it difficult to distinguish whether productivity or space is most important. This is particularly true of marine systems because most marine decomposers are sessile, and productivity is limiting. To test how space impacts decomposer diversity and activity, we manipulated resource space while keeping productivity constant in both a marine and marsh habitat. Two 100% cellulose sponges (‘wood’) were combined to vary the amount of surface area (space) while volume (productivity) remained constant in four shapes that ranges from 1:1 to 2:1: surface area to volume. After one month, decomposers were extracted and IDed from sponges and sponge decomposition was measured. We found that 1) invertebrate diversity and abundance were not impacted by sponge type or location, and that 2) decomposition rate was positively related to space. Our results suggest that diversity and abundance may be driven by productivity at a community level, but that decomposition is driven by space at an ecosystem level. This experiment further extended our current understanding of SARs in marine decomposer systems, and ultimately suggests that both space and productivity can be co-limiting factors in saline environments.