scholarly journals Nekton community dynamics within active and inactive deltas in a major river estuary: potential implications for altered hydrology regimes

2021 ◽  
Author(s):  
CB Taylor ◽  
JA Nyman ◽  
MK La Peyre
Keyword(s):  
Community Dynamics ◽  
River Estuary ◽  
Altered Hydrology ◽  
Nekton Community ◽  
Major River

scholarly journals Response of the Snowy River Estuary to two environmental flows

2015 ◽  
Vol 127 (2) ◽  
pp. 28
Author(s):  
Errol J. McLean ◽  
Jon B. Hinwood
Keyword(s):  
Fresh Water ◽  
Peak Flow ◽  
Environmental Flows ◽  
River Estuary ◽  
Environmental Flow ◽  
River Channel ◽  
Salinity Gradients ◽  
Tasman Sea ◽  
Eastern Australia ◽  
Major River

The Snowy River is a major river in south-eastern Australia, discharging to the Tasman Sea via a barrier estuary, with its entrance constricted by marine sands. Since the construction of the Snowy Mountains Scheme, river flows have not been sufficient to maintain the river channel. A program of environmental flow releases (EFR) is returning water to the river to restore the fluvial reaches and is now trialling flow regimes that may also benefit the estuarine reaches. This paper documents the response of the estuarine segments of the Snowy River to two EFRs; the release in 2010 was designed to scour the upper reaches of the Snowy River while the larger 2011 release was intended to extend the scouring downstream. For each release, the effects on the entrance morphology, tides and salinity through the flow peak and recovery are described. Each EFR caused minor increases in depth and very minor longshore movement of the entrance channel, although each EFR had been preceded by a larger fresh flow that would have scoured the channels. The small increase in fresh water inflow in the 2010 EFR pushed salinity contours seawards and steepened vertical salinity gradients. The larger inflow in the 2011 EFR purged the upper estuary of saltwater. After the peak flow, salinity recovery was rapid in the principal estuarine channels but took weeks where poorly connected wetlands could store fresh flood waters. Critical flows for scouring the entrance and purging salinity are estimated.

scholarly journals Biotic vs. abiotic forcing on plankton assemblages varies with season and size class in a large temperate estuary

2020 ◽  
Vol 42 (2) ◽  
pp. 221-237 ◽  
Author(s):  
Gretchen Rollwagen-Bollens ◽  
Stephen Bollens ◽  
Eric Dexter ◽  
Jeffery Cordell
Keyword(s):  
Community Dynamics ◽  
Abiotic Factors ◽  
River Estuary ◽  
Multiple Time Scales ◽  
Nutrient Concentrations ◽  
Winter Period ◽  
Zooplankton Abundance ◽  
Multiple Time ◽  
P Availability ◽  
Lower Estuary

Abstract Large river estuaries experience multiple anthropogenic stressors. Understanding plankton community dynamics in these estuaries provides insights into the patterns of natural variability and effects of human activity. We undertook a 2-year study in the Columbia River Estuary to assess the potential impacts of abiotic and biotic factors on planktonic community structure over multiple time scales. We measured microplankton and zooplankton abundance, biomass and composition monthly, concurrent with measurements of chlorophyll a, nutrient concentrations, temperature and salinity, from a dock in the lower estuary. We then statistically assessed the associations among the abundances of planktonic groups and environmental and biological factors. During the late spring high flow period of both years, the lower estuary was dominated by freshwater and low salinity-adapted planktonic taxa, and zooplankton grazers were more strongly associated with the autotroph-dominated microplankton assemblage than abiotic factors. During the early winter period of higher salinity and lower flow, nutrient (P) availability exerted a strong influence on microplankton taxa, while only temperature and upwelling strength were associated with the zooplankton assemblage. Our results indicate that the relative influence of biotic (grazers) and abiotic (salinity, flow, nutrients and upwelling) factors varies seasonally and inter-annually, and among different size classes in the estuarine food web.

Rare unclassified 16S rRNA operational taxonomic units from the uncharted Engaño Bay (Argentinean Patagonia)

2018 ◽  
Vol 64 (1) ◽  
pp. 91-96
Author(s):  
Andrea Y. Calvo ◽  
Julieta M. Manrique ◽  
Leandro R. Jones
Keyword(s):  
16S Rrna ◽  
Community Dynamics ◽  
Sequence Data ◽  
River Estuary ◽  
Fragmented Habitats ◽  
Operational Taxonomic Units ◽  
Microbial Community Dynamics ◽  
Argentinean Patagonia ◽  
Culture Independent ◽  
Taxonomic Assignments

Rare microbes make up most of the diversity of marine microbiomes, and recent works have highlighted their importance for microbial community dynamics and in fragmented habitats. Rare taxa have been infrequently studied in comparison with abundant groups, and rare unclassified sequences are common in culture-independent studies. Here, we describe a detailed analysis of nonclassifiable sequences from the Chubut river estuary at the Argentinean Patagonia. Standard taxonomic assignments of environmental 16S rRNA sequences resulted in about 13% unclassified operational taxonomic units (OTUs). The potential affiliations of these OTUs could be narrowed by mapping the classification software assignments on a phylogeny obtained directly from our environmental sequence data. Customized BLAST analyses were remarkably consistent with these phylogenetic assignments, especially when the unclassified OTUs were blasted against sequences from cultured and type microorganisms. In addition, our BLAST analyses revealed significant similarities between several unclassified OTUs and a plethora of unclassified sequences from around the world. Further phylogenetic comparisons with 6194 carefully selected reference sequences showed that these unclassified sequences may correspond to 5 unnamed groups, possibly encompassing ranks from subclass to family inside the Alphaproteobacteria, and to an unknown Gracilibacteria lineage. Overall, these results demonstrate the value of straight phylogenetic analysis, customized BLAST searches, and comparisons with sequences from type material, for the systematic study of rare unclassified sequences.

Community dynamics and activity of nirS-harboring denitrifiers in sediments of the Indus River Estuary

2020 ◽  
Vol 153 ◽  
pp. 110971 ◽  
Author(s):  
Fozia ◽  
Yanling Zheng ◽  
Lijun Hou ◽  
Zongxiao Zhang ◽  
Dengzhou Gao ◽  
...  
Keyword(s):  
Community Dynamics ◽  
River Estuary ◽  
Indus River

Fitzroy River, Queensland, Australia. II. Identification of Sources of Estuary Bottom Sediments

2006 ◽  
Vol 3 (5) ◽  
pp. 377 ◽  
Author(s):  
G. B. Douglas ◽  
P. W. Ford ◽  
M. Palmer ◽  
R. M. Noble ◽  
R. Packett
Keyword(s):  
River Basin ◽  
Management Practices ◽  
Regional Scale ◽  
River Estuary ◽  
Companion Paper ◽  
Sediment Flux ◽  
Longitudinal Variation ◽  
Sediment Sources ◽  
Major River ◽  
Fitzroy River

Environmental Context. The Fitzroy River Basin constitutes a major source of suspended sediment and nutrient fluxes to the southern Great Barrier Reef. Improved land management practices to ameliorate these catchment loads require an understanding of the sediment sources and dynamics. This multidisciplinary geochemical and modelling study provides for the first time a quantitative estimate of sediment sources delivered to, and their degree of retention in, the Fitzroy River Estuary. Abstract. Sources of sediment deposited in the Fitzroy River Estuary (FRE) have been identified and quantified using an integrated geochemical, modelling and reconnaissance soil sampling approach. A companion paper (this volume) identifies the major sources of sediments in impoundments on the major river systems and sediment sampled from flood events in the Fitzroy River Basin (FRB). Sediment within the FRE may display distinct longitudinal variation with little basaltic material retained. Sediments derived from the Bowen Basin, which occupies the greatest portion of the FRB, and from the Surat Basin display the greatest longitudinal variation. All FRB soils have a similar total phosphorus (P) concentration. Thus, in considering P export from the catchment it is the total sediment flux which is of major importance, rather than the relative proportions of individual catchment soils. This research provides crucial new regional scale information on the sediment sources deposited within the FRE.

Picophytoplankton community dynamics in a tropical river estuary and adjacent semi-enclosed water body

2021 ◽  
Vol 83 (4) ◽  
Author(s):  
Smita Mitbavkar ◽  
Aseem R. Rath ◽  
Arga Chandrashekar Anil
Keyword(s):  
Water Body ◽  
Community Dynamics ◽  
River Estuary ◽  
Tropical River
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