Disturbance and Food Chain Length in Rivers

Power, Mary E.; Parker, Michael S.; Wootton, J. Timothy

doi:10.1007/978-1-4615-7007-3_28

Cited by 85 publications

(90 citation statements)

References 51 publications

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“…Factors constraining food chain length are controversial. Food chains may remain short due to the progressive depletion of energy transferred to higher trophic levels, or because long food chains may suffer population fluctuations so severe as to impair the persistence of top predators (reviewed in Pimm 1982, DeAngelis 1995, Power et al 1996. Recent hypotheses that have not yet been fully explored involve dimensionality of habitats, i.e.…”

Section: Patterns Of 15 N Signatures and Trophic Relationshipsmentioning

confidence: 99%

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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Section: Patterns Of 15 N Signatures and Trophic Relationshipsmentioning

confidence: 99%

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

View full text Add to dashboard Cite

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“…19-23) and of physical disturbance in general (e.g., refs. [24][25][26][27][28]. In the present study, a late-season hurricane wiped out two populations of lizards that an earlier hurricane failed to exterminate even though the earlier hurricane was stronger.…”

Section: Discussionmentioning

confidence: 83%

Variable ecological effects of hurricanes: The importance of seasonal timing for survival of lizards on Bahamian islands

Schoener

Spiller

Losos

2003

Proc. Natl. Acad. Sci. U.S.A.

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Two recent hurricanes passed directly over the northern Bahamas 2 years apart, allowing a comparison of their effects on lizard populations inhabiting exactly the same islands. The hurricanes differed in two ways: one struck during the reproductive season and was relatively severe; the other struck after most reproduction had taken place and was milder. The late-season hurricane produced a significant relation between population reduction and lowness of the island that lasted at least through two seasons; the earlier hurricane produced no such relationship. The late-season hurricane wiped out populations of lizards on two islands (two of the three lowest) that the earlier hurricane failed to exterminate even though it was stronger. We relate these effects to the fact that the study lizards regenerated from the earlier hurricane only via the egg stage, whereas eggs were unavailable when the later storm struck and regeneration was via hatched lizards. We discriminate and illustrate four kinds of hurricanes, cross-classified by two contrasts: earlier vs. later and stronger vs. weaker. A later, stronger hurricane completely exterminated lizard populations at a second Bahamian site, whereas an earlier, weaker hurricane had no detectable effect at a third Bahamian site. We suggest that, in addition to severity, the timing of a hurricane as it coincides with reproductive scheduling or other phenological aspects may determine the magnitude of its effect on a variety of organisms.

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“…In the South Fork of the Eel River in northern California, field experiments demonstrated four-level trophic control during two of five years during which fish were manipulated in large stream enclosures (Power, 1990b;Power et al, 1996). Similar experiments revealed three levels of trophic control during a third year, and two levels (fish proving functionally irrelevant to algal persistence) during the remaining two years.…”

Section: When Is a Pool A Pool?mentioning

confidence: 85%

“…Other algivores are protected from predators by a sessile life style, living under a silken retreat, often reinforced with detritus, algae or sediments (Hershey, 1987). Alternatively, mobile grazers can be defended by heavy armor, for example, armored catfish in Neotropical streams (Power, 1983), or armored caddisflies in temperate streams (Li and Gregory, 1989;Power et al, 1996). Grazers with either defense, if abundant, can be 'trophic cul de sacs', effectively truncating energy flow and top-down control to two functional levels thereby limiting attached algal biomass.…”

Section: Intermediate Consumers: Links Between Producers and Predatormentioning

confidence: 99%

Environmental controls on food web regimes: A fluvial perspective

Power

2006

Progress in Oceanography

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Because food web regimes control the biomass of primary producers (e.g., plants or algae), intermediate consumers (e.g., invertebrates), and large top predators (tuna, killer whales), they are of societal as well as academic interest. Some controls over food web regimes may be internal, but many are mediated by conditions or fluxes over large spatial scales. To understand locally observed changes in food webs, we must learn more about how environmental gradients and boundaries affect the fluxes of energy, materials, or organisms through landscapes or seascapes that influence local species interactions. Marine biologists and oceanographers have overcome formidable challenges of fieldwork on the high seas to make remarkable progress towards this goal. In river drainage networks, we have opportunities to address similar questions at smaller spatial scales, in ecosystems with clear physical structure and organization. Despite these advantages, we still have much to learn about linkages between fluxes from watershed landscapes and local food webs in river networks. Longitudinal (downstream) gradients in productivity, disturbance regimes, and habitat structure exert strong effects on the organisms and energy sources of river food webs, but their effects on species interactions are just beginning to be explored. In fluid ecosystems with less obvious physical structure, like the open ocean, discerning features that control the movement of organisms and affect food web dynamics is even more challenging. In both habitats, new sensing, tracing and mapping technologies have revealed how landscape or seascape features (e.g., watershed divides, ocean fronts or circulation cells) channel, contain or concentrate organisms, energy and materials. Field experiments and direct in situ observations of basic natural history, however, remain as vital as ever in interpreting the responses of biota to these features. We need field data that quantify the many spatial and temporal scales of functional relationships that link environments, fluxes and food web interactions to understand how they will respond to intensifying anthropogenic forcing over the coming decades.

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Disturbance and Food Chain Length in Rivers

Cited by 85 publications

References 51 publications

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

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

Variable ecological effects of hurricanes: The importance of seasonal timing for survival of lizards on Bahamian islands

Environmental controls on food web regimes: A fluvial perspective

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