Estimation of the non-seasonal production of Spartina maritima (Curtis) Fernald in a South African Estuary

Net aerial production of Spartina maritima (Curtis) Fernald, in a warm temperature estuary in Algoa Bay, South Africa, occurring possibly as an exotic, was estimated as 523–680 g dry weight m −2 year −1. The method of production measurement designed here used community structure data and accounted for the species' extremely slow shoot production (3.1–6.7 dry g m −2 year −1) and continuous leaf turnover (516–676 dry g m −2 year −1). Standard methods of production measurement for other Spartina species failed by not accounting for the non-seasonal growth of S. maritima. N, C, organic and energy content of live and dead shoots remained constant through the seasons. The P : B ratio is 1.1, which is lower than for other Spartina species, but agrees with the low vigour shown by negligible regrowth a year after clipping. Decomposition rates were 90 mg g −1 month −1 in winter and 305 mg g −1 month −1 in summer. Monthly decomposition values showed significant correlation with air temperature ( r = 0.86; P < 0.01), and water temperature ( r = 0.80; P < 0.01), suggesting that monthly litterbag losses are a valid means of determining decomposition rate.