Enzyme-based resource allocated decomposition and landscape heterogeneity in the Florida Everglades

Enzyme catalyzed reactions are generally considered the rate-limiting step in organic matter degradation and may be significantly influenced by the structure and composition of plant communities. Changes in these rates have the potential to effect long-term peat accumulation and influence the topography of a wetland ecosystem. To determine habitat influences on enzyme activities, we examined slough and sawgrass plots within enriched and reference phosphorus (P) sites in the Everglades. Assays were performed for the enzymes involved in carbon (C), nitrogen (N), and P cycling and lignin depolymerization. Enzyme activities were normalized and analyzed in terms of a resource allocation strategy. Plant composition was found to significantly alter the allocation of enzymatic resources due to varying substrate complexities. Potential decomposition in the slough was less influenced by lignin than in the sawgrass habitats. Additionally, an index relating hydrolytic and oxidative enzymes was significantly greater in the slough habitats, whereas C/N ratios were significantly lower. These indices suggest more favorable decomposition conditions and thus slower peat accretion within the slough communities, which may contribute to the development of elevation differences within the sawgrass ridge and slough topography of the Everglades.     

Capelin (Mallotus villosus) fecundity in post-1990s coastal Newfoundland

In the 1990s, a cold water event was associated with drastic changes in the biology of Newfoundland capelin (Mallotus villosus), the key forage fish in the north Atlantic. In contrast to studies conducted prior to the 1990s, we report a lower maximum potential fecundity (7,616–42,880) and a weak relationship between fecundity and body size based on fecundity of 218 female capelin (12.3–16.9 cm) collected within two coastal regions of Newfoundland in 2008 and 2009. Further, using forward stepwise multiple regression and hierarchical partitioning, we conclude that life history traits (mass, somatic mass and egg size) and condition indices (Fulton’s K, Hepatosomatic Index and Gonadosomatic Index) are not appropriate proxies for fecundity of capelin in our study area. Hierarchical partitioning revealed that egg size and condition indices suppress the variance in fecundity explained by other factors. Based on the insight it provides into the influence of traits on fecundity, we suggest that hierarchical partitioning is a powerful analysis technique that could be used in further investigations.