Stable carbon isotopes as pelagic food web tracers in adjacent shelf and slope regions off British Columbia, Canada

1999 ◽  
Vol 56 (12) ◽  
pp. 2477-2486 ◽  
Author(s):  
R Ian Perry ◽  
Peter A Thompson ◽  
David L Mackas ◽  
Paul J Harrison ◽  
Douglas R Yelland
Keyword(s):  
British Columbia ◽  
Food Web ◽  
Food Webs ◽  
Stable Carbon Isotopes ◽  
Water Mass ◽  
Larval Fish ◽  
Deep Ocean ◽  
Food Web Interactions ◽  
Deep Ocean Water ◽  
Pelagic Food Webs

Surveys were conducted in spring 1992 to examine the use of 13C/12C ratios to differentiate pelagic food webs and to trace food web interactions between adjacent continental shelf and slope/deep ocean environments off southwestern British Columbia, Canada. Salinity was used to define shelf or slope/deep ocean water masses and their productivity conditions because eddies and meanders at the shelf break were observed to draw water off the shelf. The 13C/12C ratio of plankton was related to the mean upper layer (0-50 m) salinity. 13C abundance was enriched (relative to 12C) in the shelf water mass compared with the slope water mass. This enrichment persisted up the food web from particulate organic matter through three size-classes of zooplankton to larval fish. The cross-shelf spatial scale separating these food webs, as determined from spatial semivariograms of 13C/12C and the upper layer mean salinity, was 40-45 km, similar to the Rossby radius for eddies at this location (50 km). Larval fish may provide a means to monitor exchanges of plankton between geographically adjacent food webs if time scales for incorporation of new isotope signatures from diets into tissues are determined.

Effect of Somatic Growth and Reproduction on Biomass Transfer up Pelagic Food Webs as Calculated from Particle-Size-Conversion Efficiency

1983 ◽  
Vol 40 (11) ◽  
pp. 2010-2018 ◽  
Author(s):  
Uwe Borgmann
Keyword(s):  
Particle Size ◽  
Food Web ◽  
Food Webs ◽  
Conversion Efficiency ◽  
Somatic Growth ◽  
Mysis Relicta ◽  
Biomass Transfer ◽  
Pelagic Food Webs ◽  
Simple Equations ◽  
Growth And Reproduction

Biomass or energy transfer up pelagic food webs to larger sized organisms is a function of (1) direct trophic level transfer through predation, (2) somatic growth, a process that augments biomass transfer through predation, and (3) reproduction, which impedes biomass transfer by moving biomass down the food web to smaller sizes. By assuming that particle-size-conversion efficiency (log (food consumed/biomass produced)/log (predator–prey size ratio)) is relatively constant, I derive simple equations to calculate the effect of somatic growth and reproduction on biomass transfer up the food web. This defines the conditions under which somatic growth and reproduction can be ignored and biomass flow can be calculated from predation alone, using a previously developed model. When these conditions are not met, the effect of somatic growth and reproduction can be calculated from data on cohort growth and mortality rates. It is not necessary to identify the food of any species. This eliminates one of the problems often encountered when modeling food webs. I have applied these equations to production of Mysis relicta. If the estimates of Mysis abundance and growth rates are correct, then size-corrected production is about 25% greater for this species when somatic growth is accounted for in the calculations. This is because mortality of young Mysis appears to be low and most production occurs during somatic growth and not during reproduction.

scholarly journals Medium-sized exotic prey create novel food webs: the case of predators and scavengers consuming lagomorphs

PeerJ ◽  
2016 ◽  
Vol 4 ◽  
pp. e2273 ◽  
Author(s):  
Facundo Barbar ◽  
Fernando Hiraldo ◽  
Sergio A. Lambertucci
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Apparent Competition ◽  
Ecological Processes ◽  
Novel Food ◽  
Food Web Interactions ◽  
Conservation Actions ◽  
Upper Level ◽  
Native Diversity ◽  
Analytical Tools

Food web interactions are key to community structure. The introduction of species can be seen as an uncontrolled experiment of the addition of species. Introduced species lead to multiple changes, frequently threatening the native biodiversity. However, little is known about their direct effect on the upper level of the food web. In this study we review empirical data on the predator–prey relationship between the introduced lagomorphs and their consumers, and use meta-analytical tools to quantify the strength of their interactions. We expect that exotic lagomorphs will destabilize food webs, affect ecological processes and compromise the conservation of the invaded regions. We found 156 studies on the diet of 43 species of predators that consume lagomorphs as exotic preys in South America and Oceania. We found an average exotic lagomorphs-predator link of 20% which indicates a strong interaction, given that the average for the strongest links with native prey (when lagomorphs are not included in the predator diet) is about 24%. Additionally, this last link decreases to 17% when lagomorphs are present. When lagomorphs arrive in a new environment they may become the most important resource for predators, producing an unstable equilibrium in the novel food web. Any disruption of this interaction could have catastrophic consequences for the native diversity by directly impacting predators or indirectly impacting native preys by apparent competition. Eradication or any change in their abundances should be carefully considered in conservation actions since those will have great impacts on predator populations and ultimately in the whole communities.

Food web interactions between larval bluegill (Lepomis macrochirus) and exotic zebra mussels (Dreissena polymorpha)

2004 ◽  
Vol 61 (3) ◽  
pp. 497-504 ◽  
Author(s):  
David F Raikow
Keyword(s):  
Food Web ◽  
Dreissena Polymorpha ◽  
Larval Fish ◽  
Lepomis Macrochirus ◽  
Zooplankton Community ◽  
Zebra Mussels ◽  
Structured Populations ◽  
Zooplankton Abundance ◽  
Differential Growth ◽  
Food Web Interactions

Food web interactions between native larval bluegill (Lepomis macrochirus), exotic invasive zebra mussels (Dreissena polymorpha), and zooplankton were examined with a mesocosm experiment. Hatchling larval bluegill collected from nests were reared in the presence of size-structured populations of zebra mussels in 1500-L limnocorrals suspended in an artificial pond for 2 weeks. Chlorophyll a, other limnological variables, and zooplankton abundance and biomass (including copepod nauplii and rotifers) were monitored over time. During their first 2 weeks of life, larval fish reared in the presence of mussels grew 24% more slowly than fish reared alone. Differential growth rates can be explained by competition between mussels and bluegill for food in the form of microzooplankton. Also likely was an indirect competition via starvation of the zooplankton community as zebra mussels consumed phytoplankton. Either direct or indirect trophic competition between zebra mussels and obligate planktivores may result in ecological harm as zebra mussels spread throughout inland lakes of North America.

Effects of Ocean Acidification on Pelagic Organisms and Ecosystems

2011 ◽  
Author(s):  
Ulf Riebesell ◽  
Philippe D. Tortell
Keyword(s):  
Ocean Acidification ◽  
Food Web ◽  
Food Webs ◽  
Spatial Scales ◽  
Scale Up ◽  
Carbonate System ◽  
Marine Food Web ◽  
Pelagic Food Webs ◽  
Carbon Pump ◽  
Marine Food

Over the past decade there has been rapidly growing interest in the potential effects of ocean acidification and perturbations of the carbonate system on marine organisms. While early studies focused on a handful of phytoplankton and calcifying invertebrates, an increasing number of investigators have begun to examine the sensitivity to ocean acidification of various planktonic and benthic organisms across the marine food web. Several excellent review articles have recently summarized the rapidly expanding literature on this topic (Fabry et al. 2008; Doney et al. 2009 ; Joint et al. 2011). The focus of this chapter is on the potential ecosystem-level effects of ocean acidification. Starting with a brief review of the basic physical, chemical, and biological processes which structure pelagic marine ecosystems, the chapter explores how organismal responses to perturbations of the carbonate system could scale up in both time and space to affect ecosystem functions and biogeochemical processes. As with many chapters in this volume, and indeed much of the ocean acidification literature at present, our review raises more questions than it answers. It is hoped that these questions will prove useful for articulating and addressing key areas of future research. Complexity in marine pelagic food webs results from the interactions of multiple trophic levels across a range of temporal and spatial scales. The traditional view of marine food webs (Steele 1974) involved a relatively short trophic system in which large phytoplankton (e.g. net plankton such as diatoms) were grazed by a variety of mesozooplankton (e.g. copepods), which were in turn consumed by second-level predators, including many economically important fish and invertebrate species. This ‘classic’ marine food web is typical of high-productivity regions such as coastal upwelling regimes (Lassiter et al. 2006). A characteristic feature of these systems is a strong decoupling between primary production and grazing, which results from the different metabolic rates of consumers and producers and, in many cases, ontogenetic and seasonal delays in the emergence of feeding predators. The uncoupling between phytoplankton and their consumers leads to significant export of organic material out of the euphotic zone, the so-called biological carbon pump (discussed further below).

Modeling Water-Mass Distributions in the Modern and LGM Ocean: Circulation Change and Isopycnal and Diapycnal Mixing

2021 ◽  
Vol 51 (5) ◽  
pp. 1523-1538
Author(s):  
C. S. Jones ◽  
Ryan P. Abernathey
Keyword(s):  
Ocean Circulation ◽  
Water Mass ◽  
Vertical Mixing ◽  
Deep Ocean ◽  
Atlantic Water ◽  
Ocean Water ◽  
Mass Distributions ◽  
Mixing Coefficient ◽  
Deep Ocean Water ◽  
Isopycnal Mixing

AbstractPaleoproxy observations suggest that deep-ocean water-mass distributions were different at the Last Glacial Maximum than they are today. However, even modern deep-ocean water-mass distributions are not completely explained by observations of the modern ocean circulation. This paper investigates two processes that influence deep-ocean water-mass distributions: 1) interior downwelling caused by vertical mixing that increases in the downward direction and 2) isopycnal mixing. Passive tracers are used to assess how changes in the circulation and in the isopycnal-mixing coefficient impact deep-ocean water-mass distributions in an idealized two-basin model. We compare two circulations, one in which the upper cell of the overturning reaches to 4000-m depth and one in which it shoals to 2500-m depth. Previous work suggests that in the latter case the upper cell and the abyssal cell of the overturning are separate structures. Nonetheless, high concentrations of North Atlantic Water (NAW) are found in our model’s abyssal cell: these tracers are advected into the abyssal cell by interior downwelling caused by our vertical mixing profile, which increases in the downward direction. Further experiments suggest that the NAW concentration in the deep South Atlantic Ocean and in the deep Pacific Ocean is influenced by the isopycnal-mixing coefficient in the top 2000 m of the Southern Ocean. Both the strength and the vertical profile of isopycnal mixing are important for setting deep-ocean tracer concentrations. A 1D advection–diffusion model elucidates how NAW concentration depends on advective and diffusive processes.

Changes in the δ13C of pelagic food webs: the influence of lake area and trophic status on the isotopic signature of whitefish (Coregonus lavaretus)

2004 ◽  
Vol 61 (8) ◽  
pp. 1485-1492 ◽  
Author(s):  
Marie-Elodie Perga ◽  
Daniel Gerdeaux
Keyword(s):  
Food Web ◽  
Food Webs ◽  
Trophic Status ◽  
Dissolved Inorganic Carbon ◽  
Alpine Lakes ◽  
Coregonus Lavaretus ◽  
Lake Area ◽  
Pelagic Food Web ◽  
Pelagic Food Webs ◽  
Lake Size

We investigated the relationships between the pattern of variation of δ13C in pelagic food webs and various morphologic and trophic characteristics of peri-alpine lakes. We used the δ13C of whitefish (Coregonus lavaretus), a long-lived zooplanktivorous fish, to assess the isotope ratio of dissolved inorganic carbon (DIC) at the origin of the pelagic food web. The δ13C of DIC depends on its origin, which may be the atmosphere or the mineralization of organic matter. A synchronic study of 22 peri-alpine lakes shows that the surface area of the lake accounts for much of the variability of the δ13C in pelagic food webs (r2 = 0.76). The δ13C increases with lake size, which suggests that the origin of the DIC integrated into the pelagic food web depends on lake size. To differentiate the influence of trophic status from morphological effects, a diachronic study was performed on the δ13C of fish scales collected over the 20-year re-oligotrophication of Lake Geneva. The δ13C of whitefish increased with phosphorus concentration (r2 = 0.71). This pattern is related to the growing demand for atmospheric DIC as primary production increases.

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