Nektonic invertebrate abundance and distribution at the emergent vegetation-open water interface in the Delta Marsh, Manitoba, Canada

Wetlands ◽  
1992 ◽  
Vol 12 (1) ◽  
pp. 45-52 ◽  
Author(s):  
E. J. Murkin ◽  
H. R. Murkin ◽  
R. D. Titman
Keyword(s):  
Open Water ◽  
Emergent Vegetation ◽  
Water Interface ◽  
Delta Marsh ◽  
Invertebrate Abundance ◽  
Abundance And Distribution

The introduced aquatic macrophyte, Myriophyllum spicatum, as habitat for fish and their invertebrate prey

1984 ◽  
Vol 62 (7) ◽  
pp. 1289-1303 ◽  
Author(s):  
Allen Keast
Keyword(s):  
Aquatic Macrophyte ◽  
Myriophyllum Spicatum ◽  
Late Summer ◽  
Open Water ◽  
Depth Zone ◽  
Invertebrate Abundance ◽  
Golden Shiner ◽  
Before And After ◽  
The Rich ◽  
Abundance And Distribution

The exotic macrophyte Myriophyllum spicatum spread widely in Lake Opinicon, Ontario, after 1974, dominating the 2.0- to 3.5-m depth zone which had previously been largely open water. In the shallows it formed beds within the species-rich native Potamogeton–Vallisneria community. This paper compares fish and prey-invertebrate abundance and distribution (i) before and after the milfoil invasion for a series of depth zones (1972 relative to 1979–1980), and (ii) in communities of M. spicatum relative to native macrophytes in the littoral zone shallows in the summer of 1980. At a depth of 2.0–3.5 m (major M. spicatum zone), there were significantly fewer bluegill but more black crappie and golden shiner in 1979–1980 compared with 1972, and significantly fewer isopods, chironomid and trichopteran larvae, and ephemeropteran nymphs. Differences were greatest in late summer. Inshore and offshore from the M. spicatum zone, differences were minor, suggesting that the invader, not time, was responsible. At a 1.0- to 1.3-m depth in the summer of 1980, three to four times as many fish occurred during the daytime feeding period in the Potamogeton–Vallisneria community than in the M. spicatum area. In the benthos, beneath the native beds, five major taxa of prey invertebrates were three to seven times more abundant. The foliage of Potamogeton plus Vallisneria supported twice as many invertebrates per square metre in late summer than did M. spicatum. Insect emergences over the summer (May–September) were twice as high. Up to the present, the net impact of the habitat change on the fish populations of Lake Opinicon has not been great. If in the future M. spicatum were to replace the rich native macrophyte beds in the shallows, this would be cause for concern.

scholarly journals High net CO<sub>2</sub> and CH<sub>4</sub> release at a eutrophic shallow lake on a formerly drained fen

2016 ◽  
Vol 13 (10) ◽  
pp. 3051-3070 ◽  
Author(s):  
Daniela Franz ◽  
Franziska Koebsch ◽  
Eric Larmanou ◽  
Jürgen Augustin ◽  
Torsten Sachs
Keyword(s):  
Global Warming ◽  
Shallow Lake ◽  
Typha Latifolia ◽  
Open Water ◽  
Emergent Vegetation ◽  
Lake Ecosystem ◽  
Co2 Uptake ◽  
Mild Winter ◽  
Ch4 Emissions ◽  
Northeastern Germany

Abstract. Drained peatlands often act as carbon dioxide (CO2) hotspots. Raising the groundwater table is expected to reduce their CO2 contribution to the atmosphere and revitalise their function as carbon (C) sink in the long term. Without strict water management rewetting often results in partial flooding and the formation of spatially heterogeneous, nutrient-rich shallow lakes. Uncertainties remain as to when the intended effect of rewetting is achieved, as this specific ecosystem type has hardly been investigated in terms of greenhouse gas (GHG) exchange. In most cases of rewetting, methane (CH4) emissions increase under anoxic conditions due to a higher water table and in terms of global warming potential (GWP) outperform the shift towards CO2 uptake, at least in the short term.Based on eddy covariance measurements we studied the ecosystem–atmosphere exchange of CH4 and CO2 at a shallow lake situated on a former fen grassland in northeastern Germany. The lake evolved shortly after flooding, 9 years previous to our investigation period. The ecosystem consists of two main surface types: open water (inhabited by submerged and floating vegetation) and emergent vegetation (particularly including the eulittoral zone of the lake, dominated by Typha latifolia). To determine the individual contribution of the two main surface types to the net CO2 and CH4 exchange of the whole lake ecosystem, we combined footprint analysis with CH4 modelling and net ecosystem exchange partitioning.The CH4 and CO2 dynamics were strikingly different between open water and emergent vegetation. Net CH4 emissions from the open water area were around 4-fold higher than from emergent vegetation stands, accounting for 53 and 13 g CH4 m−2 a−1 respectively. In addition, both surface types were net CO2 sources with 158 and 750 g CO2 m−2 a−1 respectively. Unusual meteorological conditions in terms of a warm and dry summer and a mild winter might have facilitated high respiration rates. In sum, even after 9 years of rewetting the lake ecosystem exhibited a considerable C loss and global warming impact, the latter mainly driven by high CH4 emissions. We assume the eutrophic conditions in combination with permanent high inundation as major reasons for the unfavourable GHG balance.

scholarly journals The Relative Importance of Agricultural and Wetland Habitats to Waterbirds in the Sacramento–San Joaquin River Delta of California

2019 ◽  
Vol 17 (1) ◽  
Author(s):  
W. David Shuford ◽  
Matthew Reiter ◽  
Kristin Sesser ◽  
Catherine Hickey ◽  
Gregory Golet
Keyword(s):  
Central Valley ◽  
Positive Association ◽  
Open Water ◽  
Biodiversity Loss ◽  
Habitat Associations ◽  
Conservation Strategies ◽  
San Joaquin River ◽  
Conservation Actions ◽  
Surrounding Landscape ◽  
Abundance And Distribution

Biodiversity loss from agricultural intensification underscores the urgent need for science-based conservation strategies to enhance the value of agro-ecosystems for birds and other wildlife. California’s Central Valley, which has lost over 90% of its historical wetlands and currently is dominated by agriculture, still supports waterbird populations of continental importance. A better understanding of how waterbirds use available habitat is particularly needed in the Sacramento–San Joaquin Delta, an ecosystem under threat. From 2013 to 2015, we studied waterbird habitat associations in the Delta during fall migration and winter by conducting diurnal counts at random locations in key waterbird habitats throughout the Delta. Waterbird use of cover types (agricultural crops and managed wetlands) varied substantially among waterbird groups, by season, and among geographic sub-regions of the Delta. Overall, wetlands were particularly important to waterbirds in fall. In winter, wetlands and flooded rice and corn were important to many waterbird groups, and non-flooded corn and irrigated pasture to geese and cranes. The factors that influenced waterbird abundance and distribution also varied substantially among groups and differed at various geographic scales. In both seasons, most groups had a positive association at the field level with flooded ground and open water, and a negative association with vegetation. Given the great uncertainty in the future extent and pace of habitat loss and degradation in the Delta, prioritizing the conservation actions needed to maintain robust waterbird populations in this region is urgent. For the Delta to retain its importance to waterbirds, a mosaic of wetlands and wildlife-friendly crops that accounts for the value of the surrounding landscape must be maintained. This includes restoring additional wetlands and maintaining corn, rice, alfalfa, and irrigated pasture, and ensuring that a substantial portion of corn and rice is flooded in winter.

The nature and significance of microatolls

1978 ◽  
Vol 284 (999) ◽  
pp. 99-122 ◽  
Keyword(s):  
Open Water ◽  
High Water ◽  
Growth Direction ◽  
Tidal Range ◽  
Water Interface ◽  
Maximum Elevation ◽  
Two Factors ◽  
Upward Growth ◽  
Daily Water ◽  
Water Springs

Microatolls, those coral colonies with dead, flat tops and living perimeters, result from a restriction of upward growth by the air/water interface. The principal growth direction is horizontal and is recorded in the internal structure, though fluctuations in water depth can influence the surface morphology producing a terraced effect. The morphology of the basal surface of the colony is controlled by the sand/water interface such that the thickness of the coral records the depth of water in which it lived. In open water at the margin of reefs in the Northern Province of the Great Barrier Reef, tall-sided uneven-topped microatolls live, whereas, on the reef flats in rampart-bounded moats and ponds, thin flat-topped and terraced microatolls are abundant. Because water in moats can be ponded to levels as high as high water neaps (1.6 m above datum at Cairns) and still have daily water replenishment, microatolls on reef flats can grow to levels 1.1 m higher than open-water microatolls (which grow up to a maximum elevation of low water springs, i.e. 0.5 m above datum). This imposes a major constraint on the use of microatolls in establishing sea level history. The two factors controlling pond height during one sea stand (relative to the reef) are tidal range (which governs the height of high water neaps) and wave energy (which governs the height of ramparts which enclose moats). Dating and levelling fossil microatolls exposed on the reefs show that 4000 years (a) B.P., high water neaps was at least 0.7 m higher than it is at present.

Changes in the Distribution of Aquatic Plants in a Tropical Swamp

1983 ◽  
Vol 10 (4) ◽  
pp. 323-329 ◽  
Author(s):  
Patrick L. Osborne ◽  
Gregory J. Leach
Keyword(s):  
Papua New Guinea ◽  
Environmental Changes ◽  
Open Water ◽  
Emergent Vegetation ◽  
Aerial Photographs ◽  
Sewage Effluent ◽  
Tropical Wetlands ◽  
Ecological Importance ◽  
Port Moresby ◽  
Very High

Tropical wetlands are of great ecological importance and are worthy of widespread and vigorous conservation efforts. They are, however, very susceptible to environmental changes which often result from human activities. Waigani swamp near Port Moresby, Papua New Guinea, comprises a number of small, shallow lakes, the largest of which, Waigani Lake, has a surface area of 120 ha. This Lake now has nutrient-rich water with very high phytoplankton populations owing to sewage effluent disposal.Changes in the macrophyte flora and vegetation of Waigani Lake are documented in aerial photographs taken between 1942 and 1981. From 1942 to 1956 the Lake was dominated by emergent vegetation, and there was very little open water. Between 1956 and 1966 this emergent vegetation was replaced by dense stands of nymphaeids. In 1965, sewage disposal into Waigani Lake began and by 1974 only a few small stands of nymphaeids remained. By 1978 no nymphaeids could be found in Waigani Lake. The decline in the nymphaeid cover of Waigani Lake was accompanied by a regression of the surrounding reed-swamp. Two other lakes near Port Moresby are nutrient-poor and have a dominant and diverse macrophyte flora, being probably more comparable with Waigani Lake prior to its enrichment—apart from a recent takeover by a pestiferous free-floating water-fern.

scholarly journals Beyond a single patch: local and regional processes explain diversity patterns in a seagrass epifaunal metacommunity

2018 ◽  
Author(s):  
Keila A Stark ◽  
Patrick L Thompson ◽  
Jennifer Yakimishyn ◽  
Lynn Lee ◽  
Emily M Adamczyk ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Spatial Scales ◽  
Interspecific Interactions ◽  
Ecosystem Functions ◽  
Seagrass Meadows ◽  
High Dispersal ◽  
Invertebrate Abundance ◽  
Local And Regional Processes ◽  
Abundance And Distribution ◽  
Regional Processes

AbstractEcological communities are jointly structured by dispersal, density-independent responses to environmental conditions and density-dependent biotic interactions. Metacommunity ecology provides a framework for understanding how these processes combine to determine community composition among local sites that are regionally connected through dispersal. In 17 temperate seagrass meadows along the British Columbia coast, we tested the hypothesis that eelgrass (Zostera marinaL.) epifaunal invertebrate assemblages are influenced by local environmental conditions, but that high dispersal rates at larger spatial scales dampen effects of environmental differences. We used hierarchical joint species distribution modelling to understand the contribution of environmental conditions, spatial distance between meadows, and species co-occurrences to epifaunal invertebrate abundance and distribution across the region. We found that patterns of taxonomic compositional similarity among meadows were inconsistent with dispersal limitation and meadows in the same region were often no more similar to each other than meadows over 1000 km away. Abiotic environmental conditions (temperature, dissolved oxygen) explained a small fraction of variation in taxonomic abundances patterns across the region. We found novel co-occurrence patterns among taxa that could not be explained by shared responses to environmental gradients, suggesting the possibility that interspecific interactions influence seagrass invertebrate abundance and distribution. Our results add to mounting evidence that suggests that the biodiversity and ecosystem functions provided by seagrass meadows reflect ecological processes occurring both within meadows and across seascapes, and suggest that management of eelgrass habitat for biodiversity may be most effective when both local and regional processes are considered.

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