The Ecosystem of Thingvallavatn: A Synthesis

Jónasson, Pétur M.

doi:10.2307/3545062

Cited by 31 publications

(14 citation statements)

References 61 publications

(31 reference statements)

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“…(Payne, 1986;Lewis, 1996). Thus, the small number of benthic taxa is attributed to the anoxia of the profundal zone (Jónasson, 1992;Kajak, 1977;Moore, 1981;Ohtaka et al, 2006). Overcoming anoxia is difficult for most metazoans (Babler et al, 2008), with the exception of a few species that are capable of tolerating anoxic conditions (Brodersen et al, 2004;Hamburger et al, 2000;Cleto-Filho and Arcifa, 2006).…”

Section: Species Richness and Densitymentioning

confidence: 99%

Profundal benthic invertebrates in an oligotrophic tropical lake: different strategies for coping with anoxia

et al. 2014

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Section: Species Richness and Densitymentioning

confidence: 99%

Profundal benthic invertebrates in an oligotrophic tropical lake: different strategies for coping with anoxia

et al. 2014

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“…No oxygen depletion was recorded in the water immediately above the profundal sediment. A detailed description of Thingvallavatn is given by Jbnasson (1992). The annual gross production of phytoplankton averages 95 g C m - .…”

Section: The Study Sitementioning

confidence: 99%

The role of zoobenthos in energy flow in deep, oligotrophic Lake Thingvallavatn, Iceland

Lindegaard

1992

Hydrobiologia

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Macrozoobenthos in Thingvallavatn is dominated by 42 taxa. The vertical distribution delimits 5 communities: (1) the surf zone community from 0-2 m, (2) the upper stony littoral community from 2-6 m,(3) the lower stony littoral community from 6-10 m, (4) the Nitella zone community from 10-20 m, and (5) the profundal zone community from 20-1 14 m. Total mean lakewide production was 78 kJ m -* yr -'.Herbivores, detritivores, and carnivores contributed 59 % , 38 % and 3 % , respectively. Respiration and ingestion were estimated according to the literature. Net production efficiency averaged 0.50. Ingestion was dominated by herbivores in the littoral zones (46-81 %), while detritivores made up 93 % in the profundal zone. Total zoobenthic production averaged 6% of estimated available food with a range from 10-11 % in the three upper littoral zones to only 2 % in the Nitella zone. The profundal fauna converted 6% of the estimated sedimentation of organic matter to secondary production. On a lakewide basis the zoobenthos utilized one third of the estimated potential food resources. Zoobenthic production made up 32% of total secondary production.

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“…The trophic efficiencies calculated in this study cannot be easily compared with those of other studies which either considered fewer groups of producers and consumers (Jonasson, 1992;Lindegaard, 1994;Vander Zanden et al, 2006), or used artificially assembled communities (Rowland et al, 2015). The pelagic efficiencies in both our study lakes were lower than in other studies (Gaedke & Straile, 1994) due to low crustacean biomasses (Lischke et al, 2016).…”

Section: Discussionmentioning

confidence: 58%

Benthic carbon is inefficiently transferred in the food webs of two eutrophic shallow lakes

et al. 2017

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The sum of benthic autotrophic and bacterial production often exceeds the sum of pelagic autotrophic and bacterial production, and hence may contribute substantially to whole‐lake carbon fluxes, especially in shallow lakes. Furthermore, both benthic and pelagic autotrophic and bacterial production are highly edible and of sufficient nutritional quality for animal consumers. We thus hypothesised that pelagic and benthic transfer efficiencies (ratios of production at adjacent trophic levels) in shallow lakes should be similar. We performed whole ecosystem studies in two shallow lakes (3.5 ha, mean depth 2 m), one with and one without submerged macrophytes, and quantified pelagic and benthic biomass, production and transfer efficiencies for bacteria, phytoplankton, epipelon, epiphyton, macrophytes, zooplankton, macrozoobenthos and fish. We expected higher transfer efficiencies in the lake with macrophytes, because these provide shelter and food for macrozoobenthos and may thus enable a more efficient conversion of basal production to consumer production. In both lakes, the majority of the whole‐lake autotrophic and bacterial production was provided by benthic organisms, but whole‐lake primary consumer production mostly relied on pelagic autotrophic and bacterial production. Consequently, transfer efficiency of benthic autotrophic and bacterial production to macrozoobenthos production was an order of magnitude lower than the transfer efficiency of pelagic autotrophic and bacterial production to rotifer and crustacean production. Between‐lake differences in transfer efficiencies were minor. We discuss several aspects potentially causing the unexpectedly low benthic transfer efficiencies, such as the food quality of producers, pelagic–benthic links, oxygen concentrations in the deeper lake areas and additional unaccounted consumer production by pelagic and benthic protozoa and meiobenthos at intermediate or top trophic levels. None of these processes convincingly explain the large differences between benthic and pelagic transfer efficiencies. Our data indicate that shallow eutrophic lakes, even with a major share of autotrophic and bacterial production in the benthic zone, can function as pelagic systems with respect to primary consumer production. We suggest that the benthic autotrophic production was mostly transferred to benthic bacterial production, which remained in the sediments, potentially cycling internally in a similar way to what has previously been described for the microbial loop in pelagic habitats. Understanding the energetics of whole‐lake food webs, including the fate of the substantial benthic bacterial production, which is either mineralised at the sediment surface or permanently buried, has important implications for regional and global carbon cycling.

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The Ecosystem of Thingvallavatn: A Synthesis

Cited by 31 publications

References 61 publications

Profundal benthic invertebrates in an oligotrophic tropical lake: different strategies for coping with anoxia

Profundal benthic invertebrates in an oligotrophic tropical lake: different strategies for coping with anoxia

The role of zoobenthos in energy flow in deep, oligotrophic Lake Thingvallavatn, Iceland

Benthic carbon is inefficiently transferred in the food webs of two eutrophic shallow lakes

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