Stable Carbon Isotope Studies on the Pecks Cove Mudflat Ecosystem in the Cumberland Basin, Bay of Fundy

Abstract

Ratios of stable carbon isotopes (δ 13C) have been measured in components of an intertidal mudflat ecosystem located near the head of the Bay of Fundy. Special attention was given to the isolation and analysis of carbon source materials including phytoplankton, benthic algae, marsh grass (Spartina alterniflora), size-fractionated detritus, and "mineral" sediment. Bulk sediment and suspended matter were also analyzed. For most of the year the two major primary producers, Spartina and benthic diatoms (dominated by Gyrosigma spp.), had similar δ 13C values (−13 to −14‰). Some Spartina detritus, presumably "fresh" material, also had similar δ 13C values. It was therefore imposible to estimate the relative importance of carbon from these sources to the nutrition of consumer organisms. Zooplankton, benthic-feeding fish, and benthic fauna had δ 13C values mostly in the range of −12 to −15‰, suggesting that live Spartina, "fresh" detritus, and benthic diatoms could be major carbon sources. Phytoplankton and other isotopically light carbon sources including "aged" detritus, bulk and "mineral" sediment, do not appear to be major carbon sources for mudflat organisms. We found Spartina detritus to be abundant both in sediments and suspended matter outside the salt marshes, but the δ 13C values of most of the detritus were much lighter (−17 to −20‰) than those of live Spartina. The mechanism of this isotopic alteration is not known and we were not able to demonstrate it clearly in laboratory experiments. Although the δ 13C method has helped to assess the relative importance of some isotopically distinct carbon sources, we were unable to detect any 13C enrichment in various trophic levels of mudflat organisms and benthic-feeding fish.Key words: stable carbon isotope ratio, detritus, decomposition, mudflat ecosystem, Pecks Cove, Bay of Fundy

Use of stable carbon isotope ratios to compare plant material and potential consumers in a seagrass bed and a kelp bed in Nova Scotia, Canada

“…It has been shown for kelp beds near Cape Town, S. Africa, that mussels ingest and effectively utilize kelp detritus (Seiderer et al 1982, Stuart 1982) but in our case it seems more probable that the mussels in both sites were obtaining most of their carbon from a common source, namely the phytoplankton, which has a value about -19 % (Schwinghamer et al 1983). While the ranges of L. longicruris and phytoplankton isotope ratios overlap, particulate matter from L. longicruris would be expected to have an isotopic composition with a smaller range around the value of homogenized tissues ( -15.5 Yw).…”

“…The sediments in each area had values considerably more negative than those of the macrophytes in the same area (Fig. l ) , again suggesting a major input of phytoplankton, which often has a value between -18 and -25 %O (Fry & Sherr 1984) and has been measured in Nova Scotia waters to be -18.7 to -19.6 YW (Schwinghamer et al 1983).…”

Trophic importance of benthic microalgae to macrozoobenthos in coastal bay systems in Korea: dual stable C and N isotope analyses

“…In this respect, much attention has been paid to the role of benthic microalgae for food webs of coastal embayments, where a high standing crop of benthic microalgae occurs in the surface sediments (Schwinghamer et al 1983, Riera & Richard 1996, Herman et al 2000. Since resuspended benthic microalgal biomass can often exceed that of phytoplankton in the tidal flat ecosystems (Cadée 1971, Baillie & Welsh 1980, de Jonge & van Beusekom 1992, Prou et al 1994, it is hypothesized that organic matter from benthic microalgae along with phytoplankton may support both benthic and pelagic food webs in the intertidal and adjacent subtidal areas of shallow bay systems.…”

Influence of Spartina detritus enrichment on exchange of nutrients between sediment and water in an intertidal area of Bay of Fundy

“…Observations in the Bay of Fundy have shown that detritus originating from Spartina may be buried in the sediment at the location of growth or may be transported from the salt marshes by tidal currents and deposited elsewhere (Roberts 1982, Hargrave et al Permanent address: Institute of Biology, Odense University. Campusvej 55, DK-5230 Odense M, Denmark 1983, Schwinghamer et al 1983. In a study on epibenthic algal production and benthic respiration on intertidal mudflats in the Bay of Fundy, Hargrave et al (1983) found a negative net production indicating a n import of organic matter which may be supplied by Spartina detritus.…”