Production in Natural and Restored Seagrasses: A Case Study of a Macrobenthic Polychaete.

Abstract

Restoration of seagrass beds has been suggested as a method to correct declining vegetation cover in shallow waters. Secondary production of the polychaete Kinbergonuphis simoni was used to evaluate faunal equivalency of newly restored (2-yr-old) seagrass beds to beds that are mature (at least 17 yr old) in an embayment in Tampa Bay, Florida. Information on density of polychaetes, size structure, reproductive characteristics, and production (growth increment summation method) was collected from May 1989 to February 1991 from individuals within monthly sediment cores from both planted and natural seagrass beds. Additionally, total macroinfauna were sampled every 3 mo at the same sites. Deposit-feeding polychaetes were the dominant macroinfaunal taxa in all seagrass beds examined. Three polychaete species, including Kinbergonuphis simoni, displayed significantly enhanced abundances in planted compared to natural seagrass beds. Population abundance and size class distribution of Kinbergonuphis within planted sites displayed more rapid and consistent population increases after populations disappeared in winter 1989 than that recorded for natural sites. Production values of planted areas over 22 mo were an order of magnitude higher than that recorded in natural areas. Higher production values resulted principally from rapid recovery of populations in planted areas in contrast to natural beds, which did not display such resiliency. Biomass allocation to reproduction did not vary among individuals from natural and planted beds, but more total individuals were participating in reproductive events in planted areas. Results of this study suggest that in addition to abundance of some frequently encountered deposit-feeders, functional characteristics of a common polychaete from seagrass beds vary with age of bed. Moreover, the link between faunal functional equivalency and vegetational cover remains obscure.