Isotopic variability of organic carbon in a phytoplankton-based, temperate estuary

Gearing, J. N.; Gearing, Patrick J.; Rudnick, David T.; Requejo, A.G.; Hutchins, M.J

doi:10.1016/0016-7037(84)90199-6

Cited by 315 publications

(182 citation statements)

References 62 publications

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“…The primary producer (seaweed) in the intertidal area also showed this nitrogen isotope ratio. This range of carbon isotope ratios is within that reported for plankton (Gearing andothers, 1984, andFry andSherr, 1984). However, examination of the methods reported in the literature for collecting phytoplankton or plankton samples for stable isotope analysis indicate that the/samples often represented particulate matter of a specific particle size, rather than pure phytoplankton samples.…”

Section: Stable Carbon and Nitrogen Isotope Ratiossupporting

confidence: 80%

Use of stable carbon and nitrogen isotopes to trace the larval striped bass food chain in the Sacramento-San Joaquin Estuary, California, April to September 1985

Rast¹,

Sutton²

1989

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Section: Stable Carbon and Nitrogen Isotope Ratiossupporting

confidence: 80%

Use of stable carbon and nitrogen isotopes to trace the larval striped bass food chain in the Sacramento-San Joaquin Estuary, California, April to September 1985

Rast¹,

Sutton²

1989

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“…The smaller plankton (e.g. copepods) were not acid-washed because carbonates have no observable effect on their δ 13 C values and this procedure may alter δ 15 N values (Gearing et al 1984, Pinnegar & Polunin 1999. However, carbonates may inflate δ 13 C values by about 0.4 ‰ in slightly larger organisms such as krill (Bunn et al 1995).…”

Section: Study Area -Estuary and Gulf Of St Lawrencementioning

confidence: 99%

“…Werner & Gilliam 1984, Huse & Toresen 1996, and from stable isotope analysis (e.g. Gearing et al 1984, Hobson & Welch 1995, France 1996. The δ 15 N values of yearling harp seals from the Estuary indicated that they feed at slightly lower trophic levels than older individuals from the same region.…”

Section: Patterns Of 15 N Signatures and Trophic Relationshipsmentioning

confidence: 99%

“…Hobson & Welch 1992, Ostrom et al 1993, Muir et al 1995. This method is based on the demonstration that stable isotope ratios in tissues of animals are correlated with those of their diet (Gearing et al 1984, Minagawa & Wada 1984. When nitrogen (N) is assimilated, 14 N is preferentially excreted and consumers become enriched in 15 N relative to their food (Minagawa & Wada 1984).…”

Section: Introductionmentioning

confidence: 99%

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Marine mammals and the community structure of the Estuary and Gulf of St Lawrence, Canada: evidence from stable isotope analysis

Lesage¹,

Hammill²,

Kovacs³

2001

Mar. Ecol. Prog. Ser.

158

131

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The trophic relationships of both the benthic and pelagic communities in the Estuary and Gulf of St Lawrence regions were examined, with a special focus on the trophic position (TP) and relationship(s) among harbour, grey, hooded and harp seals and beluga whales. A multiple stable isotope and multiple tissue approach, used in conjunction with conventional dietary information, suggested that marine mammals occupied the highest trophic positions in the food webs of both communities and that they overlapped with one another to some extent trophically. Harbour seals Phoca vitulina and hooded seals Cystophora cristata occupied the highest TP, grey seals Halichoerus grypus, Gulf harp seals Phoca groenlandica, and male beluga whales Delphinapterus leucas were intermediate, and Estuary harp seals and female beluga whales were at the lowest TP. A general pattern of increasing enrichment of 13 C or 15 N with age was observed in marine mammals (as well as fishes), although yearlings showed a decreased enrichment compared to both younger and older age classes. Sex also influenced δ 15 N values. Males were more 15 N-enriched than females, with the difference between the sexes increasing with age, and being most pronounced in species that are sexually dimorphic with respect to body size. Geographical location also influenced isotope abundance. Estuary organisms were generally 13 C-enriched relative to Gulf animals. δ 13 C values were on average lower in short-term diet integrators (blood serum) than in longer-term diet integrators (red blood cells) of harbour seals captured in April to June in the Estuary, which suggests that they probably did not move outside the Lower Estuary during the winter. Grey seals captured in the Lower Estuary did, however, show evidence of having been in the Gulf region some weeks or months before capture.

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“…Studies of seasonality of isotopic signatures in aquatic systems are still relatively rare, especially in freshwater (e.g., Gearing et al 1984;Zohary et al 1994;Yoshii et al 1999), but they are crucial when considering organisms of small size with the potential to turn over assimilated isotopes quickly and thus exhibit differing isotopic signatures over a relatively short temporal scale (Grey in press). The aims of the current study were therefore (1) to assess seasonal variability in the isotopic signatures of the two putative food sources in Loch Ness to ensure that each remained distinct from the other; (2) to assess the relative importance of allochthonous material to zooplankton body carbon over an annual cycle and thus estimate the reliance of the pelagic food web on terrestrial organic matter imported from the catchment; and (3) to examine interspecific differences in dependence on allochthonous material related to different life history and feeding strategies among the zooplankton species in Loch Ness.…”

mentioning

confidence: 99%

Seasonal changes in the importance of the source of organic matter to the diet of zooplankton in Loch Ness, as indicated by stable isotope analysis

Grey

Jones

Sleep³

2001

Limnology & Oceanography

298

303

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Seasonal variations in the stable isotope composition (␦ 13 C and ␦ 15 N) of crustacean zooplankton and their putative food sources in oligotrophic Loch Ness were recorded during 1998. Bulk particulate organic matter (POM) showed ␦ 13 C values consistent with a terrestrial plant origin from the catchment and exhibited little seasonal variation, whereas POM ␦ 15 N was more variable, probably due to associated microbial action. In contrast, phytoplankton ␦ 13 C was relatively light and showed some seasonal variation, but ␦ 15 N values were more constant. The isotopic signatures of both POM and phytoplankton remained sufficiently distinct from each other throughout the period of study to allow their relative contributions to zooplankton diet to be assessed. Zooplankton isotopic signatures shifted seasonally, reflecting a dietary switch from a reliance on allochthonous carbon derived from POM during winter and early spring to heavy dependence on algal production during summer. Annually, crustacean zooplankton in Loch Ness derive approximately 40% of their body carbon from allochthonous sources, likely mediated via microbial links. Separate determination of isotope ratios for the main zooplankton species allowed a more detailed trophic investigation. The most abundant zooplankton species in the loch, Eudiaptomus gracilis, incorporated appreciable allochthonous carbon even during the peak of phytoplankton productivity. By contrast, Daphnia hyalina grew mainly in late summer and autumn and derived almost 100% body carbon from algal sources. This study is the first to quantify such a seasonal switch in zooplankton dependence between allochthonous and autochthonous sources of organic matter in a large lake.The ecological importance of terrestrially derived material to lake food webs is receiving increasing attention. Much of the impetus for this has come from studies of the dark stained waters of small, boreal forest lakes of Scandinavia resulting from humic matter originating in the catchment (Meili 1992). The staining restricts light penetration into the water column and presents an unfavorable environment for photosynthetic fixation of carbon in situ by autotrophic phytoplankton (Jones 1992). Thus, in these systems, autochthonous production is usually very low. Humic material is capable of supporting bacterial metabolism (Hessen 1992) and associated heterotrophic organisms in the microbial loop (Tranvik 1992); consequently, a significant contribution to the humic lake food web may be derived from allochthonous matter via detritus-driven food chains. Jones (1992) hypothesized that the relative importance of allochthonous organic matter to the pelagic food web of lakes should increase with decreasing lake trophy, and a survey of the balance between planktonic production : respiration ratios lent support to this hypothesis (del Giorgio andPeters 1993, 1994). In oligotrophic lakes where community respiration equals or exceeds phytoplankton production (del Giorgio et al. 1997), the heterotrophic plankton must recei...

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Isotopic variability of organic carbon in a phytoplankton-based, temperate estuary

Cited by 315 publications

References 62 publications

Use of stable carbon and nitrogen isotopes to trace the larval striped bass food chain in the Sacramento-San Joaquin Estuary, California, April to September 1985

Use of stable carbon and nitrogen isotopes to trace the larval striped bass food chain in the Sacramento-San Joaquin Estuary, California, April to September 1985

Marine mammals and the community structure of the Estuary and Gulf of St Lawrence, Canada: evidence from stable isotope analysis

Seasonal changes in the importance of the source of organic matter to the diet of zooplankton in Loch Ness, as indicated by stable isotope analysis

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