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.

Fauna of Natural Seagrass and TransplantedHalodule wrightii(Shoalgrass) Beds in Galveston Bay, Texas

“…Our study indicated that, in the Galveston Bay system, nekton and benthos densities, numbers of taxa, and species composition in transplanted shoalgrass would take more than 3 years to reach equivalence with natural seagrass. Studies in Florida demonstrated that transplant beds reached densities and species compositions similar to those of reference sites in 1–2.3 years for nekton (Fonseca et al 1996) and in 2–4 years for annelids (Bell et al 1993). Benthic communities elsewhere also seem to reach equivalence faster than in Galveston Bay, for example, after 7 months in North Carolina (Homziak et al 1982) and after 9 months in Oregon (Posey 1988).…”

“…Functional equivalence in processes such as nutrient cycling, primary and secondary productivity, predation, or growth rates has rarely been addressed, perhaps because it is more costly and time‐consuming to test. To our knowledge, Bell et al (1993) provided the only published comparison of secondary production rates in restored and natural seagrasses, and this was for only a single species of polychaete. The database necessary to predict structural equivalence of restored and natural seagrass systems remains small (only a few sites around the world), and if the literature we cite herein is any indication, variation in restoration response and success criteria is large.…”

“…Transplanted seagrass beds appear to provide at least some of the structural and functional attributes of natural seagrass beds. Benthic faunal densities in transplanted Zostera marina (eelgrass) and Halodule wrightii (shoalgrass) beds have been shown to exceed those of adjacent bare substrates in relatively short order (203 days; Homziak et al 1982) and, for polychaetes, to equal or exceed those of natural beds at 2–4 years of age (Bell et al 1993). Therefore, enhanced prey densities for upper trophic levels and potential for detrital and nutrient cycling by burrowers seem to occur quickly.…”

A Surrogate Approach to Studying the Chemical Reactivity of Burrow Mucous Linings in Marine Sediments

“…At any given time the density of burrows present may range from less than a few hundred per m 2 made by such large animals as lobsters, crabs, and shrimp (e.g., Webb and Eyre, 2004), to as high as several thousand individuals per m 22 in sediments inhabited by such smaller animals as marine annelids (e.g., Bell et al, 1993) and arthropods (e.g., amphipods; Pearson and Gingras, 2006). Burrowing activities increase the area of the sediment-water interface by as much as ten-fold: the amount of area increase depends on the burrow architecture and the population density (Koretsky et al, 2002).…”

Ecosystem structure in disturbed and restored subtropical seagrass meadows

“…Analyses conducted to date on functional performance other than primary production in restored seagrass sites, have focused on infauna (Bell et al 1993;Sheridan et al 2003;Sheridan 2004b) or epibenthic invertebrates (Fonseca et al 1990(Fonseca et al , 1996. These studies have been limited to restoration sites where seagrass has been transplanted.…”