Temporal and spatial variation in zooplankton populations in the River Great Ouse: an ephemeral food resource for larval and juvenile fish

This study used stratified random sampling to examine the spatial and temporal distribution of zooplankton communities in a large floodplain river (Mississippi River, USA). Potential mechanisms controlling zooplankton abundance and community structure were considered. Main channel and backwater habitats included in this study differed between a turbid upper pool reach where aquatic macrophytes were sparse and a lower pool reach which was considerably less turbid and had extensive aquatic macrophyte coverage. Samples were collected monthly during the summer over a 2-year period and multivariate analysis was used to examine the spatial and temporal distribution of zooplankton. Significant differences were found in zooplankton density and community composition among habitats and reaches within the pool. Rotifers were the dominant taxa and seasonality was pronounced, with peak densities often occurring in late-spring.Community structure varied by habitat and reach, which suggests that water quality, physical habitat characteristics, presence of aquatic macrophytes, and zooplankton sources can all influence the zooplankton communities of the Upper Mississippi River. Characterization of the zooplankton communities provides a basis for understanding changes in the river ecosystem and examination of zooplankton communities among habitats provides insight into the mechanisms affecting zooplankton dynamics.

Section: Comparisons To Other Riverssupporting

confidence: 67%

Seasonal zooplankton dynamics in main channel and backwater habitats of the Upper Mississippi River

Burdis

Hoxmeier

2011

“…In the natural and created flow treatments, the proportion of microcrustaceans in the community was reduced to less than 30%, whereas in the natural and created slackwater treatments the proportion of microcrustaceans was often greater than 60%. Changes in discharge are known to influence microfaunal community structure and biomass, with larger animals such as microcrustaceans being unable to persist in waters with high discharge (Bass et al, 1997).…”

Section: Discussionmentioning

confidence: 99%

“…On most sampling occasions, more taxa were recorded from the benthos of slackwaters, but over the four sampling events, the majority of taxa were recorded from all four habitats. Increasing discharge flushes biota from the river channel (Pace et al, 1992), but the slackwater habitats provide a refuge (Bass et al, 1997). Further increases in discharge scour slackwaters with a subsequent loss of biota and these communities come to resemble those typically found in flowing habitats (Saunders & Lewis, 1988).…”

Section: Discussionmentioning

confidence: 99%

The response of epibenthic rotifers and microcrustacean communities to flow manipulations in lowland rivers

Nielsen

Watson

2007

Non-flowing, slackwater habitats in lowland rivers support diverse and abundant benthic microfaunal communities; however, there is little information on how these communities respond to changes in hydrology. In this study, we tested two hypotheses: (1) microfaunal richness and density will be higher in slackwater habitats compared to flowing habitats; (2) altering the hydrology of a habitat will result in changes in the richness and density of microfauna over time so that communities will become similar to those found in a habitat with the same flow characteristics. Flowing and slackwater habitats were manipulated by constructing barriers to redirect flows, either away from flowing habitats and creating slackwater habitats, or towards a slackwater creating a flowing habitat. The resultant epibenthic microfaunal communities were compared to those in unmodified slackwaters and flowing habitats. Over a 4-month period, epibenthic microfaunal samples were collected from the four experimental treatments. Analysis of variance indicates that there was no difference in rotifer richness or abundance between habitat types, but significant differences in the richness and abundance of microcrustacean occurred with higher richness and densities occurring in the slackwater habitats compared to flowing habitats. Within four weeks of the treatments being applied, there was little difference in the microfaunal communities between the natural and created flowing habitats or between the natural and created slackwater habitats. As the hydrology of a river varies, slackwater habitats will be scoured and new habitats created. The microfauna populations associated with these habitats appear to have strategies that enable them to cope with the disturbance and to recolonise newly created slackwater areas.

“…The significant positive relationship between rotifer and crustacean abundance in the main channel underlines the abiotic control of both groups mainly due to advection. Nevertheless over 60% of the variation remains unexplained so that additional factors such as selective predation, for example by planktivorous fish (Bass et al, 1997;Spaink et al, 1998;Jack & Thorp, 2002), and overall food availability have to be taken into consideration. However, the importance of these backwaters as an inoculum for the zooplankton community of the main channel has a rather qualitative than quantitative character, because exchange between water bodies is limited due to the singular connection to main channel.…”

Section: Lateral Influencesmentioning

confidence: 99%

Spatial dynamics of rotifers in a large lowland river, the Elbe, Germany: How important are retentive shoreline habitats for the plankton community?

Zimmermann-Timm

Holst²,

Kausch³

2007

The longitudinal dynamics of Rotifers in the Potamal region of the River Elbe between Dresden, km 46, and Geesthacht, km 583, was investigated on a Lagrangian survey in 2000 which included transversal sampling (left bank, main channel, right bank) and sampling of five major tributaries and backwaters to evaluate lateral impacts on the zooplankton community. A simple model of longitudinal development for the dominant species Trichocerca pusilla was calculated, based on the results of an in situ incubation in Dresden and on literature data and compared with the dynamics observed on the Lagrangian survey. To characterize the influence of groyne fields on the main channel zooplankton community, an additional lateral sampling was conducted in August 2000 at Havelberg, km 423. Zooplankton community was clearly dominated by rotifers. A distinct downstream-directed increase of rotifers was observed. Longitudinal development of rotifers could be explained predominantly by reproduction during downstream transport.