Open Water Zone Research Articles

Spatial and Temporal Variance Analysis of Water Quality Purification in Linluo Artificial Wetland

This paper investigated whether differences exist in the surface water quality when the wetland was under the management of different organizations through factor analysis. Factor scores suggest that overall there is a regular reduction of nutrient sources BOD, COD, TKN, TN, NH3-N, NO2-N and fecal pollution in this wetland. The nutrient content is the highest at the water inlet and gradually decreases over densely planted zone I, the open water zone, densely planted zone II and the discharge orifice, reaching the minimum level at the outlet. The influence factors of suspended solids TB and SS exhibit irregular variation in the different water bodies. Cluster analysis is conducted based on water quality using data collected between 2008 and 2012. Results reveal that regardless of wet or dry seasons, similar water quality is observed in the open water zone and densely planted zone II. Water quality at the inlet resembles that in densely planted zone I.

The influence of aquatic macrophytes on distribution and feeding habit of two Asplanchna species (A. priodonta and A. herrickii) in shallow wetlands, South Korea

We tested the hypothesis that the spatial distribution and diet composition of Asplanchna species might be affected by the presence of aquatic macrophytes in 33 wetlands in South Korea. We estimated the densities of Asplanchna and other rotifer and crustacean, together with environmental parameters, in both vegetated and open water zones, from May to June 2011. In the present study, two species of Asplanchna, A. priodonta and A. herrickii, were observed and significantly more abundant in open water zones lacking macrophytes. In particular, the density of A. priodonta was higher than that of A. herrickii, and the density of A. priodonta was strongly positively correlated with the area of open water. In addition, gut content analysis was used to determine their dietary preferences, with the finding that there was apparent differentiation in food source utilisation between the two Asplanchna species; A. priodonta consumed some protozoa, phytoplankton, and exclusively pelagic rotifer, while A. herrickii consumed primarily Euglena. In particular, Keratella and Polyarthra were most commonly consumed by A. priodonta in open water. Macrophytes represent a suitable habitat for epiphytic rotifer but not for pelagic rotifer; this characteristic drives pelagic rotifer such as Asplanchna towards open water and may be responsible for the significant negative correlation that we observed between macrophyte and Asplanchna densities.

Zooplankton Community Distribution and Food Web Structure in Small Reservoirs: Influence of Land Uses around Reservoirs and Kittoral Aquatic Plant on Zooplankton.

We collected zooplankton from May to October, 2011, with the aim of understandingthe zooplankton community distribution and food web interaction between the openwater and littoral (aquatic plants) zones in two small reservoirs with different landcovers(Sobudang, Myeongdong). Small-sized reservoirs are more abundant in SouthKorea, and a total of 51 and 65 species of zooplankton were identified at the twosmall reservoir (Sobudang and Myeongdong), where zooplankton densities weremore abundant in the littoral zone than in the open water zone. Cladocerans andcopepods densities were also higher in the littoral zone, in contrast, rotifers showedhigher densities in the open water zone (t-test,

An Ecosystem Valuation Method for Small Water Bodies

Abstract The paper discusses the development of a valuation method for small water bodies in a landscape park of agricultural character, since for such an area small water bodies are of considerable importance, primarily hydrological and natural. Analyses were conducted in the Dezydery Chlapowski Landscape Park. The object of the study comprised 13 water bodies differing in terms of landscape, morphological parameters (depth, shape, surface area, shoreline development) as well as aquatic and marsh vegetation. Some of these water bodies are typical in-field hollows, some are located in built-up areas, while two are located in a forest complex. The aim of the presented investigations was to develop a valuation method for small water bodies based on inventoried aquatic and marsh vegetation and including modifications of nature analysis methods such as the phytosociological method by Braun-Blanquet and ecological indexes according to Zarzycki. Using environmental variables statistical models were developed, describing dependencies between individual species and analysed variables. Investigations were conducted in the years 2008-2009, in which phytosociological relevés were prepared during the vegetation season. Analyses concerned vegetation of the littoral zone and the limnetic (open water) zone. The ecological status of water bodies was calculated on the basis of data concerning aquatic and marsh vegetation and the measured surface area of a given water body. Results indicate the advisability of having small water bodies covered with legal protection measures. In turn, the water bodies which underwent severe degradation should be remediated using available measures (dredging, creation of biogeochemical barriers).

Effect of water chemistry on the planktonic communities and relationships among food web components across a freshwater ecotone

Most ecological research on the food web has been focused more on the pelagic zone than on the transitional zone - ecotones between lentic and lotic habitats. The specific goals of this study were to determine whether the contact zone of waters differs in hydrochemical and biological terms from the waters of the canal and the open water zone, and to evaluate the influence of particular macro-habitats on the interactions between components of the planktonic food web. The distribution of samples in ordination space led us to conclude that the studied habitats are distributed along the rising gradient of total organic carbon and nutrients. Assemblages of all investigated groups showed a strong compositional gradient correlated with conductivity and total phosphorus, while a second strong gradient in species composition was explained by nitrate nitrogen and/or phosphate concentrations. The analysis of trophic relationships in the system bacteriaciliates- crustaceans reveals a clear differentiation and strength of mutual relations between the analyzed zones. The highest number of significant correlations was determined in the contact zone. It can also be a place of very efficient matter and energy flow in freshwater ecosystems.

Effects of predation pressure and resource use on morphological divergence in omnivorous prey fish

BackgroundBody shape is one of the most variable traits of organisms and responds to a broad array of local selective forces. In freshwater fish, divergent body shapes within single species have been repeatedly observed along the littoral-pelagic axes of lakes, where the structural complexity of near shore habitats provides a more diverse set of resources compared to the open-water zones. It remains poorly understood whether similar resource-driven polymorphism occurs among lakes that vary in structural complexity and predation pressure, and whether this variation is heritable. Here, we analyzed body shape in four populations of omnivorous roach (Rutilus rutilus) inhabiting shallow lakes. We tested the relationship between body shape, gradients of resources, predation pressure, and, in a subset of two lakes, diet composition. We used genome scans of 331 polymorphic AFLP markers to test whether there was a heritable component to the observed morphological diversification.ResultsBody shape differed among lakes and was significantly correlated to differences in predation pressure. Roach from the lake with highest predation pressure were most divergent from the average body shape of all populations, characterized by a more streamlined body and caudally inserted dorsal fins; features that facilitate predator escape. Surprisingly, diet composition was not associated with morphology. AFLP analysis revealed weak genetic differentiation among lakes and no isolation by distance (IBD). Outlier analysis detected three loci under positive selection with differing frequencies in the four populations. General linear models did not support an association of lake-specific genotypes with morphological variation.ConclusionBody shape was divergent among lakes, suggesting that processes previously reported from within single lakes may also be operating at the scale of whole lakes. We found no evidence for body shape being heritable, although sample size was small in these natural populations. Rather than habitat structure and diet, we conclude that predation had a stronger effect on the prevalence of local morphotypes. A variable morphotype facilitating the efficient uptake of a variety of spatially and temporarily scattered resources seems to be favored in these small aquatic systems.

Use of single versus multiple biotic communities as indicators of biological integrity in northern prairie wetlands

As much as 70% of prairie wetlands in Canada have been lost. Although further degradation of natural wetlands is considered to be somewhat offset by wetland construction and restoration, Canada lacks bioassessment tools that can track ecosystem health in prairie wetlands. Indices of biological integrity (IBIs) use one or more biotic communities to compare the biological condition of a particular site to conditions found in least-impacted reference sites. Using the IBI approach, we evaluated the potential of 5 biotic communities to assess wetland health in northern prairie wetlands in Canada. Vegetation in the wet meadow, emergent and open-water zones as well as wetland-dependent songbirds and waterbirds were sampled at 81 semi-permanent/permanent natural and compensation wetlands spanning an environmental stress gradient. Metrics with strong linear relationships to the stress gradient (R2>0.2) were combined into an IBI for each biotic community and were subsequently validated at a suite of test sites. After validation, the entire data set was combined and each IBI was evaluated based on its linear relationship to environmental stress. Wet meadow zone vegetation was a strong indicator of environmental stress (R2=0.68, p<0.001), as was the wetland-dependent songbird community (R2=0.59, p<0.001). The emergent zone vegetation community was a relatively weak and inconsistent indicator of environmental stress, while the open-water zone vegetation and waterbird communities were poor indicators. To evaluate whether monitoring more than one biotic community provided additional information about a site's biological and environmental condition, we produced a two-taxon IBI that combined wet meadow zone vegetation and wetland-dependent songbird metrics. The two-taxon IBI had a marginally stronger linear relationship to the stress gradient (R2=0.72, p<0.001) than any single biotic community alone, although we argue that this added information would not warrant the extra cost, effort, and logistical barriers of sampling both plants and birds. The wet meadow zone vegetation and wetland-dependent songbird IBIs were strong surrogates of one another (R2=0.57), suggesting that wet meadow zone vegetation can be used to predict the health of wetland-dependent songbirds, and visa versa. Our results suggest that habitat for healthy wet meadow zone vegetation and wetland-dependent songbird communities is being degraded as compensation sites are replacing their natural analogs.

Sediments, not plants, offer the preferred refuge for Daphnia against fish predation in Mediterranean shallow lakes: an experimental demonstration

Summary1. Different behavioural responses of planktonic animals to their main predators, fish, have been reported from shallow lakes. In north temperate lakes, large‐bodied zooplankton may seek refuge from predation among macrophytes, whereas in subtropical lakes, avoidance of macrophytes has been observed. The prevalent behaviour probably depends on the characteristics of the fish community, which in Mediterranean lakes is typically dispersed in both the open water zone and in the littoral, as in temperate lakes, and is dominated by small size classes, as in subtropical lakes.2. We performed ‘habitat choice’ experiments to test the response of Daphnia magna to predation cues at both the horizontal and vertical level by mimicking a ‘shallow littoral’ zone with plants and a ‘deeper pelagic’ zone with sediments.3. Initial separate response experiments showed that natural plants, artificial plants and predation cues all repelled D. magna in the absence of other stimuli, while sediments alone did not trigger any significant response by D. magna.4. The habitat choice experiments showed that, in the presence of predation cues and absence of plants, Daphnia moved towards areas with sediment. In the presence of both plants and sediments, Daphnia moved away from the plants towards the sediments under both shallow and deep water treatment conditions.5. Based on these results, we suggest that Daphnia in Mediterranean shallow lakes avoid submerged macrophytes and instead prefer to hide near the sediment when exposed to predation risk, as also observed in subtropical shallow lakes. This pattern is not likely to change with water level alterations, a common feature of lakes in the region, even if the effectiveness of the refuge may be reduced.

Sulfur stable isotope signature identifies the source of reduced sulfur in benthic communities in macrophyte zones of Lake Biwa, Japan

Carbon, nitrogen and sulfur stable isotope ratios (δ13C, δ15N and δ34S) were measured from water column sulfate, sediments, particulate organic matter (POM), macrophytes, periphyton, macroinvertebrates and fish, sampled from the littoral, open water and macrophyte zones of Lake Biwa. In most of the littoral zones, the δ13C and δ15N values of organisms indicated that POM and periphyton support the consumers. However, in the dysoxic interior macrophyte (IM) zone, the δ13C values of Sinotaia quadrata histrica, Propsilocerus akamusi and Anodonta woodiana were lower than that of all resources. The δ15N values of S. quadrata histrica were lower than those of P. akamusi and A. woodiana. δ13C and δ15N values thus failed to distinguish the foods of these consumers. The δ34S values of sediment and S. quadrata histrica were lower than those of water column sulfate, suggesting that this consumer incorporated reduced sulfur derived from sulfate reduction in the sediment by ingesting detritus. In contrast, the δ34S values of P. akamusi and A. woodiana were higher than that of S. quadrata histrica, suggesting that they incorporated sulfur derived from water column sulfate by ingesting POM. Consequently, δ13C, δ15N and δ34S signatures provide complementary estimates of foods for consumers in this freshwater lake.

Plant community, environment, and land-use data from oil sands reclamation and reference wetlands, Alberta, 2007–2009

Our goal was to evaluate the success of wetland reclamation efforts on oil sands mining company lease-holdings in Alberta, Canada. Already, 60 200 ha of land have been disturbed by mining, and an additional 419 800 ha will be mined in the future. Wetland reclamation efforts have been underway for 35 years, and current mine closure plans call for the construction of 15 840 ha of wetland habitat. There are, however, no accepted criteria by which the Alberta Government can evaluate constructed wetlands. We employed the reference condition approach, comparing reclamation wetlands to appropriate natural analogues with plants as bioindicators of wetland condition. The data set includes 74 wetlands, spanning a range in salinity, nutrient levels, size, and degree of human disturbance. Reclamation wetlands include those contaminated with oil sands tailings (oil sands process affected, OSPA, n = 13) and those free from tailings (oil sands reference, OSREF, n = 12). In contrast, some natural wetlands are exposed to agricultural impacts (AG, n = 12), but the majority represent our least-disturbed condition (reference wetlands, REF, n = 37). The data set includes species relative abundance from plant communities in the wet meadow, emergent, and open-water vegetation zones. In addition, we measured water and sediment chemistry variables and physical variables to quantify local environmental conditions. We also quantified land use surrounding 45 of the wetlands in a series of nested buffers ranging from 300 m to 2000 m from the edge of each wetland's open-water zone. This data set represents the most comprehensive, publicly available data on reclamation wetlands from the lease areas of the two largest oil sands mining companies. It may be used to investigate changes in wetland plant community composition along both natural and human-caused environmental gradients, including contamination by oil sands mine tails. The data could also inform studies into the effects of surrounding land use on wetland plants and local-level environmental conditions. Information about reclamation wetlands could serve as a basis for tracking reclamation trajectories over time, whereas information about reference wetlands could be used to characterize natural variability in plant communities in shallow open-water wetlands from the Boreal Plains ecoregion.

Assessing constructed wetland functional success using diel changes in dissolved oxygen, pH, and temperature in submerged, emergent, and open-water habitats in the Beaver Creek Wetlands Complex, Kentucky (USA)

We assessed the functional success of restored wetlands by determining if the patterns in dissolved oxygen (DO), temperature, and pH were similar to those conditions observed in natural wetlands. The Beaver Creek Wetlands Complex consists of dozens of marshes and ponds built in a former Licking River floodplain, in the hills of east Kentucky, USA. In natural wetland ecosystems, aquatic primary production is highest in emergent and submerged vegetations zones; where daybreak dissolved oxygen (DO) is often near zero, and DO may rise to well over 100% saturation past mid-day. Open-water areas, dominated by phytoplankton, have less dramatic diel DO fluctuations—often without pre-dawn anoxia. Compared to open water, temperatures fluctuate less dramatically in vascular vegetation, due to shading and suppression of wind and waves. Measurements of ecosystem metabolism (diel changes in DO and pH) in three aquatic habitats of the constructed wetlands (emergent vegetation, submerged vegetation, open water) were compared to these natural ideals. In Beaver Creek Wetlands, water temperature patterns were not as dramatic as in natural habitats, nor did they did follow a similar trend. Waters in emergent vegetation (29.5 °C) were warmest; submerged vegetation coolest (26.5 °C); open-water intermediate (27.4 °C). Diel DO and pH patterns were not similar to natural habitats. Highest net primary production (NPP) and gross primary production (GPP) were measured in emergent vegetation waters (mean GPP = 7.58 g m −2 d −1); lowest in submerged vegetation (mean GPP = 5.48 g m −2 d −1); and intermediate in open-water (mean GPP = 6.95 g m −2d −1). Diel pH changes were greatest in the highly productive emergent waters (median maximum daily difference of 0.36), and not as pronounced in submerged vegetation and open-water (median maximum change = 0.16 and 0.22, respectively). Water-column respiration was generally about double NPP. Like natural ecosystems, near anoxic DO concentrations were consistently measured in emergent and submerged plants before dawn; whereas open-water zones were generally >4 mg l −1. These restored wetland systems may need more time to be functionally equivalent to natural marshes.

Under-ice seiches

A closed, ice-covered water body containing water with homogeneous density distribution is considered. No-slip conditions are specified for flow velocity at the lower ice boundary and on the bed. Two variants of boundary conditions are considered on the side boundary: the boundary is either a solid vertical wall with a finite liquid depth or the liquid wedges out to zero depth values. Ice either is attached fast to the shore or is separated from it by an open-water zone. A basic fourth order equation is derived for the amplitude of ice oscillations. The introduction of friction results in the appearance of reduced depth. Eigenvalue problem is considered for evaluating seiche periods. For the case when the liquid wedges out at the shore, the basic equation becomes singular at water body boundaries. A lake with a longitudinal depth profile, which can be approximated by a parabola, is considered. The solution is found by the method of matched asymptotic expansions. In the inner domain, beyond the boundary layers, the equation is reduced to Legendre equation, which yields a new relationship for the spectrum of seiche oscillations both in the presence of ice and in an open lake with varying depth. Boundary layers appear at the margins of the lake, where the liquid wedges out; a solution is found for these layers.

Evaluation of a polynya flux model by means of thermal infrared satellite estimates

AbstractWe test the ability of a two-dimensional flux model to simulate polynya events with narrow open-water zones by comparing model results to ice-thickness and ice-production estimates derived from thermal infrared Moderate Resolution Imaging Spectroradiometer (MODIS) observations in conjunction with an atmospheric dataset. Given a polynya boundary and an atmospheric dataset, the model correctly reproduces the shape of an 11 day long event, using only a few simple conservation laws. Ice production is slightly overestimated by the model, owing to an underestimated ice thickness. We achieved best model results with the consolidation thickness parameterization developed by Biggs and others (2000). Observed regional discrepancies between model and satellite estimates might be a consequence of the missing representation of the dynamic of the thin-ice thickening (e.g. rafting). We conclude that this simplified polynya model is a valuable tool for studying polynya dynamics and estimating associated fluxes of single polynya events.

The influence of emergent and submerged macrophyte beds on ciliate communities in a shallow lake

Abstract Relationships between ciliates and the presence of emergent and submerged vegetation were studied in a shallow lake in eastern Poland. Samples were collected in zones of Phragmites, Typha, Batrachium, Elodea, Stratiotes and from the open water zone. The abundance and biomass of ciliates were significantly higher at sites with structurally most complex plants than in the open water or sparsely vegetated sites. The redundancy analysis indicated that bacterial abundance and total organic carbon were the most influential variables that determine the distribution of ciliates. However, chlorophyll a and Ptot have a lesser influence on the distribution of these microorganisms. Based on differences in macrophyte structure, two groups of habitats with similar patterns of size-related ciliate distribution were distinguished. The first group consisted of three vegetation zones of sparse stem structure and the open water zone, the second group comprised submerged macrophyte species, which were more complex.

Carbon sink to source: longitudinal gradients of planktonic P:R ratios in subtropical reservoirs

Spatial patterns of planktonic production and respiration in the surface mixed layer were examined in eight Texas, USA reservoirs to test the hypothesis that P:R ratios are lowest in upreservoir inflow zones and highest in downreservoir open-water zones, as predicted by the heuristic reservoir zonation model. We measured summer planktonic metabolism with light–dark bottles and physical–chemical conditions in epilimnetic water at 85 sites distributed among sixteen longitudinal transects within the eight reservoirs (2 transects per reservoir). Volumetric production and plankton biomass were lowest in the open-water zones and increased upreservoir; however, that pattern was reversed for areal production due to greater photic depths at open-water sites. Volumetric respiration was similar in the three zones; however, corresponding planktonic P:R ratios in the surface mixed layer were significantly lower at open-water sites, which is opposite than hypothesized. Based on linear regressions of production and respiration rates on chlorophyll a, open-water sites were net heterotrophic during the summer regardless of trophic state; whereas inflow and mid-reservoir zone sites were heterotrophic when chlorophyll concentrations were respectively less than 9.5 and 35 mg m−3. Although variation among reservoirs was high, five of the eight reservoirs had inflow zones that were net carbon sinks while seven had open-water zones that were carbon sources. Mean (±standard error) carbon flux rates of inflow, mid-reservoir, and open-water zones were −0.22 ± 0.12 (C sink), 0.39 ± 0.44 (moderate C source), and 1.33 ± 0.50 (strong C source) g C m−2 day−1 respectively. Inflow and mid-reservoir zones comprised approximately 45% of the total reservoir area studied. Therefore, omitting their contribution as often done when a single open-water site is sampled may substantially overestimate reservoir carbon flux.

Hierarchical multi-scale classification of nearshore aquatic habitats of the Great Lakes: Western Lake Erie

Classification is a valuable conservation tool for examining natural resource status and problems and is being developed for coastal aquatic habitats. We present an objective, multi-scale hydrospatial framework for nearshore areas of the Great Lakes. The hydrospatial framework consists of spatial units at eight hierarchical scales from the North American Continent to the individual 270-m spatial cell. Characterization of spatial units based on fish abundance and diversity provides a fish-guided classification of aquatic areas at each spatial scale and demonstrates how classifications may be generated from that framework. Those classification units then provide information about habitat, as well as biotic conditions, which can be compared, contrasted, and hierarchically related spatially. Examples within several representative coastal or open water zones of the Western Lake Erie pilot area highlight potential application of this classification system to management problems. This classification system can assist natural resource managers with planning and establishing priorities for aquatic habitat protection, developing rehabilitation strategies, or identifying special management actions.

Microhabitat–zooplankton relationship in extensive macrophyte vegetations of eutrophic clear-water ponds

The influence of different macrophyte taxa or growth forms on biological and environmental variables is often analysed in one-lake studies. However, the unique combination of non-vegetational characteristics of a waterbody, i.e. its site identity, can be an influential factor in itself, shaping the measured parameters irrespective of the presence or absence of certain macrophyte species. In this situation, the relative strengths of all factors can be determined best in a study that explicitly accounts for differences in the identity of the waterbodies. Several functional macrophyte groups are known to provide a potent microinvertebrate refuge or permanent habitat. The objective of this study was to detect patterns in the zooplankton assemblages associated with different extensive habitats of macrophyte species and to relate these patterns to three major factors: the microhabitat, the pond identity and the seasonality in the warmer months of the year. Five ponds located in the Woluwe catchment of the Brussels-Capital Region (Belgium) were studied monthly for macrophyte and zooplankton characteristics from July until October 2005. The vegetation in the clear ponds was characterized by extensive monospecific stands (Ceratophyllum, Chara, Nitella, Potamogeton, Nuphar and filamentous algae). Zooplankton could be analysed in seven different vegetation types and in the open water zones and contained a total of 17 cladoceran and 27 rotifer genera. Principal components analysis (PCA) ordination of zooplankton communities showed a seasonal gradient and a tendency to group within-pond habitats, although they differed in macrophyte species and habitat structure. Despite the absence of clustering of similar microhabitats across ponds, percent volume infested (PVI), vegetation biomass density and Daphnia length (used as a proxy for fish predation pressure) contributed significantly positive to the Shannon zooplankton biodiversity indices. Moreover, densities of most zooplankton subgroups and of total zooplankton were significantly and positively related to PVI. It is assumed that in eutrophic ponds, extensive, often monospecific macrophyte vegetations provide an ecological environment suitable for both macrophyte-associated species and migrating pelagic zooplankton, thereby maintaining a high microinvertebrate biodiversity.

The body size distribution of Filinia longiseta (Ehrenberg) in different types of small water bodies in the Wielkoposka region

The body size distribution of Filinia longiseta (Ehrenberg) in different types of small water bodies in the Wielkoposka region Small water bodies are often characterised by specic macrophyte species composition and different levels of predation. This may also have an effect on the body size and shape of rotifer specimens. The aim of the study was to determine the relation of the size of rotifer Filinia longiseta (body and appendages length), with respect to three specic kinds of pond (mid-forest, pastoral and anthropogenically changed) and to three kinds of hydromacrophytes (nymphaeids, elodeids and helophytes) as well as comparatively to the open water zone. The examined water bodies also differed insh presence or absence. Morphometric analysis of specimens of F. longiseta showed that both factors -the type of water body relating to different land-use in the catchment area as well as the microhabitat type- were signicant predictors, inuencing their body size and spine length. Filinia longiseta specimens were signicantly smaller in ponds situated within the pastoral catchment area. The largest specimens were found among stands of nymphaeids, while the smallest were found within the open water zone, which may indicate both the ecological requirements of this species as well as the marked inuence ofsh in the unvegetated area.

Modelling of Riparian-Imitated Constructed Wetland for Fish Habitat

This paper presents a hydrodynamic-based investigation of constructed wetland suitability for fish habitat. A constructed wetland adjacent to river is manoeuvred to imitate riparian fish habitat by means of computer modelling. Flow-velocity conditions, water depths and effects of macrophytes to resistance of flow in constructed wetland are modelled and steered towards creating a favourable ground for natural substrate spawning of native fish species. The model suggests combination of two zones, which are a macrophyte zone for typical functions of a wetland and an open water zone with gravel bed to support fish reproductive cycles.

Macroinvertebrate Assemblages in Iowa Prairie Pothole Wetlands and Relation to Environmental Features

Macroinvertebrate assemblage characteristics and other biophysical features were measured in the open-water zone of 17 semipermanent/permanent prairie pothole wetlands in Iowa. Relations among variables were used to identify likely determinants of invertebrate abundance and diversity, and useful indicators of wetland condition (i.e., health). Abundant invertebrates included physid and planorbid snails, oligochaetes, leeches, caenid mayflies, corixid bugs, chironomid midges, and amphipods. Abundant taxa were distributed across multiple functional feeding and habit groups. Invertebrate densities and taxonomic diversity were positively associated with plant/coarse particulate organic matter (plant/CPOM) abundance, and negatively related to turbidity, water-column concentrations of nitrogen and phosphorus, and presence of large-bodied fishes. Results supported hypotheses that plant/CPOM was an important invertebrate resource, and that plant/CPOM abundance was reduced in turbid, hypereutrophic wetlands. Fish likely reduced invertebrate abundance and diversity through predation and/or cascading effects on plants, turbidity, and nutrients. Wetlands with high invertebrate abundance and diversity, abundant plant/CPOM, low turbidity and nutrient concentrations, presence of tiger salamanders (Ambystoma tigrinum), and absence of large-bodied fishes appeared to be in the best condition. These features should be routinely measured to effectively assess condition of Iowa prairie pothole wetlands. Additionally, eliminating non-native fish populations may be critical to improving condition of these wetlands.