Total flows in ecosystems

A detailed energy flow model consisting of 56 living and 3 non-living compartments was assembled for the intertidal area of the Sylt-Rømø Bight. The model depicts the biomass of each compartment, carbon flow between the components, imports and exports, as well as an energy budget for each. The food web was analysed by means of network analysis which showed that about 17% of the total daily flow through the system is recycled through a complex cycling structure consisting of 1197 cycles. The cycling network indicated that about 99% of the recycling involves 2 to 3 compartments, with sediment bacteria and particulate organic carbon (POC) participating in most instances. Input/output analyses indicated that phytoplankton production in the Bight does not satisfy the demands of filter-feeders on an annual average basis so that about 160 mg C m -2 d -1 of phytoplankton have to be imported. We compared several dimensionless system level indices, such as internalised and normalised A/DC (ascendancy/development capacity) ratios, calculated for the Bight with those of other marine and estuarine ecosystems on a global basis. These comparisons showed that energy is rather inefficiently transferred within the Bight at a mean trophic efficiency index of 2.61%, and that most of the system level indices are lower than those of other coastal ecosystems. However, higher values were obtained for flow diversity and food web connectance compared to other systems. This study has revealed the Bight to be a highly complex system whose energy pathways appear to be sensitive to external perturbations.

Section: Methodsmentioning

confidence: 99%

Section: Trophic Structure and Input/output Analysismentioning

confidence: 99%

Energy flow of a boreal intertidal ecosystem, the Sylt-Rømø Bight

Baird¹,

Asmus

Asmus³

2004

“…Input-output analysis measures the importance of the direct or indirect effect of any particular transformation or flow on any other compartment (or species) (Hannon 1973, Szyrmer & Ulanowicz 1987). This analysis includes a routine called IMPACTS that quantifies the relative direct or indirect impact (or effect) that any one compartment can have on any other in the flow network (Ulanowicz & Puccia 1990).…”

Section: Ecological Network Analysismentioning

confidence: 99%

Effect of invasive species on the structure and function of the Sylt-Rømø Bight ecosystem, northern Wadden Sea, over three time periods

Baird¹,

Asmus²,

Asmus³

2012

, respectively, in 2010. Reasons for the increases in oysters and A. modestus are related to climate change which favored strong recruitment of the invasive species during unseasonably warm summers, and the subsequent decline to weak recruitment of the invasive species and an unseasonably cold 2009/2010 winter. We used ecological network analysis (ENA) to quantify ecosystem structure and function through analyses of energy (or carbon) transfer between living and non-living compartments in each of the 3 network models. Results from ENA show an increase in most of the system attributes, but a decline in number of cycles, the trophic efficiency, the ascendency ratios, and relative redundancy from 1995 to 2007; these are ascribed to the impact of the invasive species on system organization and function. Following the dramatic decline of the invasive species from 2007 to 2010 most of the system attributes decreased. The variance in the biomass and associated flows of other compartments in addition to that of the invasive species has also played a role in the changes in system attributes and function.

“…Fish production is a food web output. Based on estimated food web flows, we estimated the (direct plus indirect) dependency of fish on lower trophic levels (Szyrmer & Ulanowicz 1987) and the efficiency (sensu Rand & Stewart 1998) of fish production in both food web structures. Differences in food web efficiency or in dependencies between both food web structures are discussed based on differences in estimated carbon budgets.…”

Section: Resale or Republication Not Permitted Without Written Consenmentioning

confidence: 99%

Carbon transfer in a herbivore- and microbial loop-dominated pelagic food webs in the southern Barents Sea during spring and summer

Laender¹,

Oevelen²,

Soetaert³

et al. 2010

We compared carbon budgets between a herbivore-dominated and a microbial loopdominated food web and examined the implications of food web structure for fish production. We used the southern Barents Sea as a case study and inverse modelling as an analysis method. In spring, when the system was dominated by the herbivorous web, the diet of protozoa consisted of similar amounts of bacteria and phytoplankton. Copepods showed no clear preference for protozoa. Cod Gadus morhua, a predatory fish preying on copepods and on copepod-feeding capelin Mallotus villosus in spring, moderately depended on the microbial loop in spring, as only 20 to 60% of its food passed through the microbial loop. In summer, when the food web was dominated by the microbial loop, protozoa ingested 4 times more bacteria than phytoplankton and protozoa formed 80 to 90% of the copepod diet. Because of this strong link between the microbial loop and copepods (the young cod's main prey item) young cod (< 3 yr) depended more on the microbial loop than on any other food web compartment, as > 60% of its food passed through the microbial loop in summer. Adult cod (≤3 yr) relied far less on the microbial loop than young cod as it preyed on strictly herbivorous krill in summer. Food web efficiency for fish production was comparable between seasons (~5 × 10 -4 ) and 2 times higher in summer (5 × 10 -2 ) than in spring for copepod production. KEY WORDS: Food web · Microbial loop · Protozoa · Copepods · Gadus morhua Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 398: [93][94][95][96][97][98][99][100][101][102][103][104][105][106][107] 2010 (PAL-LTER) Program (Ross et al. 1996). Apart from abiotic quantities (e.g. nutrient levels), sampling campaigns typically include measurements of primary and bacterial (secondary) production and of standing stocks of the main phytoplankton species, bacteria and mesozooplankton. Because of the focus on the microbial components of the pelagic food web, mesozooplankton are often the highest trophic level considered. Relationships between (bacterial and/or primary) production and consumption (by [proto]zooplankton) tend to be estimated by grazing experiments (as in Vargas et al. 2007) or by numerical modelling (Fasham et al. 1999).Whereas the microbial components of the pelagic food web play a crucial role in biogeochemical cycles (Sabine et al. 2004), they also provide the necessary resources for higher trophic levels such as fish, marine mammals and humans. The differences between phytoplankton food webs and microbial food webs in terms of the efficiency of elemental cycling may thus lead to differences in terms of production rates of higher trophic levels. This concern is being included in emerging end-to-end approaches that amalgamate the food web's different trophic levels next to physical drivers to investigate the effect of environmental perturbations on marine ecosystems (e.g. Cury et al. 2008, Pedersen et al. 2008. Although relationships between lower and h...