Characteristics, Dynamics and Importance of Aggregates in Rivers - An Invited Review

Zimmermann-Timm, Heike

doi:10.1002/1522-2632(200205)87:2/3<197::aid-iroh197>3.0.co;2-7

Cited by 76 publications

(67 citation statements)

References 145 publications

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“…Aggregates and their associated organisms have been documented as an important food source for Eurytemora sp. (Zimmermann-Timm 2002). Because of the high d 13 C of the primary and secondary consumers of the ETZ relative to the freshwater algae, estuarine phytoplankton is likely to be a more important carbon source for the food web.…”

Section: Discussionmentioning

confidence: 99%

Trophic position of zebra mussel veligers and their use of dissolved organic carbon

et al. 2006

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We evaluated by stable isotope analysis the trophic structure of an estuarine transition zone (ETZ) food web and the role of an invasive species, the veliger stage of the zebra mussel Dreissena polymorpha. In the St. Lawrence ETZ, where zebra mussel veligers are now the dominant zooplankton in summer, d 13 C ranged from 231.2% (seston) to 216.1% (adult fish) and d 15 N ranged from 2.6% to 17.4%. Isotopic analysis of samples indicated that the overall food web was largely supported by autochthonous phytoplankton rather than by allochthonous terrestrial carbon. Large differences among the isotopic signals of veligers, cladocerans, and copepods suggested the use of different proportions of food items, and the isotopic values of fish larvae indicated no significant assimilation of veligers. The d 13 C signature of the veligers was in a range consistent with feeding on free-living bacteria and dissolved organic carbon (DOC) or both, and freshwater algae incubated in situ. To investigate the possibility of DOC uptake by the veligers, we incubated veligers on 14 C-labelled algal lysates. There was rapid uptake of DOC and incorporation into biomass, equivalent to 6% of the soft tissue dry weight per hour. Zebra mussel veligers are likely using autochthonous DOC as an alternate food source, and they occupy an exotic trophic position in which there is little direct interaction with other major components of the ETZ food web.

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Section: Discussionmentioning

confidence: 99%

Trophic position of zebra mussel veligers and their use of dissolved organic carbon

et al. 2006

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“…Another aspect related to this definition is that flowing water sustains different services depending on its current velocity. For example, turbulent and tranquil river reaches foster different kinds of ecological communities (Nilsson et al 2002) and possess different roles in oxygen and carbon cycling (Zimmermann-Timm 2002). Irrespective of the specific nature of pristine spatial and temporal variation in water quality and quantity at different places, river biota have evolved to cope with this variation.…”

Section: Introductionmentioning

confidence: 99%

Linking Flow Regime and Water Quality in Rivers: a Challenge to Adaptive Catchment Management

Nilsson¹,

Renöfält²

2008

E&S

160

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ABSTRACT. Water quality describes the physicochemical characteristics of the water body. These vary naturally with the weather and with the spatiotemporal variation of the water flow, i.e., the flow regime. Worldwide, biota have adapted to the variation in these variables. River channels and their riparian zones contain a rich selection of adapted species and have been able to offer goods and services for sustaining human civilizations. Many human impacts on natural riverine environments have been destructive and present opportunities for rehabilitation. It is a big challenge to satisfy the needs of both humans and nature, without sacrificing one or the other. New ways of thinking, new policies, and institutional commitment are needed to make improvements, both in the ways water flow is modified in rivers by dam operations and direct extractions, and in the ways runoff from adjacent land is affected by land-use practices. Originally, prescribed flows were relatively static, but precepts have been developed to encompass variation, specifically on how water could be shared over the year to become most useful to ecosystems and humans. A key aspect is how allocations of water interact with physicochemical variation of water. An important applied question is how waste releases and discharge can be managed to reduce ecological and sanitary problems that might arise from inappropriate combinations of flow variation and physicochemical characteristics of water. We review knowledge in this field, provide examples on how the flow regime and the water quality can impact ecosystem processes, and conclude that most problems are associated with low-flow conditions. Given that reduced flows represent an escalating problem in an increasing number of rivers worldwide, managers are facing enormous challenges.

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“…Temperature as a major selective factor can trigger and control many biological processes in the water column (Wetzel 2001), which indirectly influence the development of OABC. An increase in temperature is followed by an increase in the amount of plankton, and these living and dead organisms are a valuable substrate for the generation of aggregates (Wö rner et al 2002;Zimmermann-Timm 2002).…”

Section: Discussionmentioning

confidence: 99%

“…For example, the substrate quality and the size of aggregates strongly affected the colonization of heterotrophic organisms. Grazing on aggregate-attached organisms by pelagic or attached metazoans can change the community of particleassociated bacteria (Crump and Baross 1996;Wö rner et al 2002;Zimmermann-Timm 2002). In addition, the aggregate microbial community is known to influence interactions between the aggregates and the surrounding water (Zimmermann-Timm 2002).…”

Section: Discussionmentioning

confidence: 99%

Untitled

2010

Limnology & Oceanography

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To investigate the spatial and temporal variations of organic-aggregate-associated bacterial communities (OABC), a 25-month observation was conducted at two contrasting sites (Meiliang Bay and the lake center) in Lake Taihu, China. The structures and dynamics of the OABC were determined by partially sequencing cloned 16S rRNA genes, and by terminal restriction fragment length polymorphism (T-RFLP) analysis. One hundred ninety-two T-RFs were detected from the two sites, but only 17 T-RFs were dominant, suggesting that specific microbial populations were adapted to the unique niche provided by the organic aggregates (OA). Phylogenetically, Beta-and Alphaproteobacteria constituted the numerically most important heterotrophic bacterial group. Analysis of similarity revealed significant intra-lake heterogeneity, and significant temporal shifts in OABC. Canonical correspondence analysis demonstrated that site-specific differences in sediment resuspension and nutrient enrichment (namely nitrate and total phosphorus) were the forces driving the intra-lake differences in OABC. Water temperature and dissolved oxygen were related to the seasonal dynamics of OABC. The annual succession in OABC was significant in Meiliang Bay, but not in the lake center. In addition, nearly 35% of the bacterial sequences from OA related to bacteria from soils, activated sludge, sediments, and other habitats, indicating the potential importance of allochthonous bacteria in OABC.

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Characteristics, Dynamics and Importance of Aggregates in Rivers - An Invited Review

Cited by 76 publications

References 145 publications

Trophic position of zebra mussel veligers and their use of dissolved organic carbon

Trophic position of zebra mussel veligers and their use of dissolved organic carbon

Linking Flow Regime and Water Quality in Rivers: a Challenge to Adaptive Catchment Management

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