Patterns In Macroinvertebrate Assemblages Research Articles

Variation in macroinvertebrate assemblages and water quality as a test for different levels of ecological impairment across an Ethiopian highland river system

ABSTRACT The Ethiopian highlands is an area under high anthropogenic pressure. Despite being a hotspot for freshwater biodiversity, the ecological status of local rivers is not monitored. Physicochemical and nutrient water quality parameters and macroinvertebrate assemblages were sampled monthly from the Megech River and its tributaries from January to March 2021. Sampling locations were designated as either upstream or downstream of the Gondar City urban area. We tested for temporal (monthly) and spatial (location, river) variation in water quality and spatial (location, river) variation in macroinvertebrate assemblage structure to examine which water quality parameters were most associated with patterns in macroinvertebrate assemblages. Water quality varied significantly between locations and months but not between rivers. Water quality differences were particularly driven by higher nutrient, salinity, dissolved solids, and conductivity levels downstream, and higher pH and dissolved oxygen levels upstream. Despite the more abundant and diverse macroinvertebrate assemblages downstream, biotic index scores generally indicated slightly increased ecological impairment downstream. A clear spatial pattern emerged in macroinvertebrate assemblages between locations; we detected a significant difference between rivers, with pairwise differences between sampling locations, particularly due to high dissimilarity between the upstream and downstream locations of the Angereb, Shinta, and Qeha rivers. BIO-ENV Pearson correlations indicated that variation in macroinvertebrate assemblages were mostly explained by dissolved oxygen, salinity, and nutrient parameters including nitrate, ammonium, and sulphate. Our findings confirm the need for more rigorous monitoring of Ethiopian highland rivers and improved management of nutrient inputs.

Influence of habitat structure and environmental regime on spatial distribution patterns of macroinvertebrate assemblages associated with seagrass beds in a southern Gulf of Mexico coastal lagoon

Seagrass meadows are important for their ecological functions and ecosystem services, including habitat and shelter for a high diversity of species. The present study aims to assess the spatial distribution patterns of macroinvertebrate assemblages associated with Thalassia testudinum beds in a tropical coastal lagoon of the southern Gulf of Mexico. Environmental variables and core samples were taken from three shallow beds with different degrees of exposure to wind-driven waves: protected, exposed and semi-exposed. A total of 40 benthic macroinvertebrate species were recorded, molluscs being the most important group in terms of diversity and abundance. The highest species richness was recorded at the semi-exposed site (31 species), while the highest abundance was at the exposed site (5207 ind. m−2). Despite inter-site variations in environmental variables and physical descriptors of seagrass (seagrass biomass, shoot density, leaf length), the species richness and abundance of macroinvertebrates correlated only with seagrass biomass. Multivariate analyses showed a clear separation of macroinvertebrate assemblages into two main groups according to the degree of exposure of the sites as exposed/semi-exposed or protected. It was also determined that seagrass biomass, hydrodynamism, sedimentation/resuspension rates and the proportion of coarse particles in the sediment appear to be the variables that best explain the differences between sites. These findings support the importance of including sites with different degrees of exposure in assessing the biodiversity of seagrass beds at the landscape scale, because species composition, species richness and the abundance of associated fauna may vary considerably between sites within the same coastal region according to a combination of biotic and abiotic factors.

Seasonal and spatial patterns of macroinvertebrate assemblages and environmental conditions in Mediterranean temporary ponds in Greece

Mediterranean temporary ponds in Greece have been neglected, and only recently has attention been drawn to their protection and conservation. In this study, the macroinvertebrate fauna of the Mediterranean temporary ponds of western Crete was examined for the first time. In particular, the seasonal and spatial patterns of macroinvertebrate communities were assessed along with the spatio-temporal variation of their environmental conditions and hydroperiod variation. Benthic fauna and abiotic (physicochemical, hydroperiod) data were monitored for 3 years (2006–2008). A total of 63 macroinvertebrate taxa belonging to 33 families were recorded, with Plea minutissima, Berosus affinis, Pericoma sp., Culex sp., Chironomidae and Cyprididae being the most abundant. Nutrient pollution was significant in the ponds situated near agricultural areas and could thus explain the poor species richness. NMDS showed a clear spatial and temporal distinction between lowland and upland sites. Heteroptera species were exclusively encountered in spring, while Coleoptera larvae and adults were present in all seasons, with adults being more abundant during winter. Ordination analysis revealed significant seasonal and inter-annual differences in macroinvertebrate assemblage structure, as confirmed by ANOSIM (R = 0.965, p = 0.001). Species richness was relatively lower compared to temporary ponds from other regions because of their isolated character, unpredictable hydroperiod and degraded water quality. This study highlights that these fragile ecosystems sustain a unique invertebrate fauna able to endure pond drying by several survival traits and therefore their conservation and protection is necessary.

Large-scale macroinvertebrate assemblage patterns from least-disturbed wadeable stream sites across the 48 contiguous US states

We quantified the patterns in macroinvertebrate assemblages and their associated environmental gradients from 457 least-disturbed wadeable stream sites across the 48 contiguous United States sampled as part of US EPA’s National Wadeable Stream Assessment. The majority of the variation in assemblage composition at the finest taxonomic resolution was related to substrate size, %fastwater habitat, water chemistry, as well as east-west geographic position and elevation. Sites were classified into 5 groups with cluster analysis, and group membership was predicted from environmental data using classification tree analysis (CTA). CTA correctly classified 69.1% of test sites and indicated that groups were distinguished by east-west location, and by factors distinguishing mountain streams from lowland/plains streams. Eastern and western groups that had similar environmental characteristics had very similar coarse scale taxa composition and convergent taxa traits. Ordinations confirmed that composition patterns using coarse level taxa resolution and taxa traits no longer reflected geographic distinctions, but were only related to non-geographic environmental factors. However, composition patterns based on traits, coarse taxa, and macroinvertebrates identified to the finest practical level were all correlated with the same dominant non-geographic environmental gradients.

Spatial patterns in macroinvertebrate assemblages in surface-flowing waters of a glacially-influenced floodplain

We examined the spatial structure of macroinvertebrate assemblages in surface-flowing waters of a glacially-influenced floodplain. The floodplain main-channel responded longitudinally to changes in hydrology with evident coarse-scale zones of upwelling and downwelling; the lower floodplain main channel fell dry in late winter. Physico-chemical attributes differed among tributaries and the main channel. The main channel had lower values of conductivity, alkalinity and nitrate–N than tributaries, with right-side (east-facing) tributaries having the highest values. Left-side (west-facing) tributaries flowing over an exposed rock-face had warmer water temperatures than the main channel and right-side tributaries. The biomass of benthic organic matter and periphyton was highest in right-side tributaries, followed by main channel sites then left-side tributaries. Similarly, macroinvertebrate density and richness were higher in right-side tributaries, intermediate in main channel sites, and lowest in left-side tributaries. Macroinvertebrate assemblages clearly differed between main channel sites, right-side tributaries, and left side tributaries based on an NMDS analysis. Minor differences were observed among main channel sites, although most upstream sites showed some structural differences from downstream sites. Ephemeropterans and plecopterans were most common in main channel sites and right-side tributaries, whereas chironomids and trichopterans also were common in right-side tributaries. Although the main channel changed longitudinally in physico-chemical characteristics, no real patterns of zonation were evident in macroinvertebrate assemblages. Coarse spatial patterns in macroinvertebrate assemblages in the floodplain were reflected in the physico-chemical differences between the main channel and tributaries, and between left-side and right-side tributaries. We conclude that coarse-scale floodplain properties enhance the overall diversity of lotic macroinvertebrates. Consequently, floodplain alterations that reduce surface water heterogeneity/connectivity limits the potential macroinvertebrate diversity of floodplains.

Patterns in macroinvertebrate assemblages at different spatial scales. Implications of hydrological connectivity in a large floodplain river

The habitat heterogeneity generated and sustained by the connectivity of floodplain habitats, the seasonal flood pulse, and the variability of the physical structures typically found in floodplains of large rivers results in a variable space–time mosaic of water sources that results in a high biodiversity of the river-floodplain system. In order to assess the implications of natural connectivity and the heterogeneity on the patterns of macroinvertebrate assemblages at different spatial scales, monthly samplings in six different mesohabitats (lakes with different hydrological connection and secondary channels with permanently and intermittent flow) of the Parana River floodplain were performed from April 2005 to March 2006. The mesohabitats had different granulometry and detritus composition of their bottom sediments. They also had different conductivity, transparency, and depth in relation to the different connectivity degrees. Mesohabitats differed in the abundance of macroinvertebrates of different taxonomic groups and diversity. The environmental variables were correlated to the patterns of macroinvertebrate abundance, with dominance of different species of annelids and mollusks at the patch, mesohabitats, and island scales. An alpha diversity gradient from the isolated lake (65 taxonomic units) to the secondary channels (25 taxonomic units) was obtained. The analyzed mesohabitats showed a high taxa turnover, with high values not only among the mesohabitats located in the different islands, but also among the mesohabitats in relation to different connectivity degrees. The mesohabitats showed negative co-occurrence of macroinvertebrate assemblages. The spatial heterogeneity, sustained by the connectivity degree, played a key role in structuring benthic assemblages at different scales, positively influencing the regional diversity.

Spatio-temporal nested patterns in macroinvertebrate assemblages across a pond network with a wide hydroperiod range

Nestedness has been widely used to measure the structure of biological communities and occurs when species-poor sites contain subsets of species-rich ones. Here, we examine nested patterns across the macroinvertebrate assemblages of 91 ponds in Doñana National Park, Spain, and explore temporal variation of nestedness and species richness in 19 temporary ponds over 2 years with differing rainfall. Macroinvertebrate assemblages were significantly nested; both pond spatial arrangement and environmental variation being important in driving nested patterns. Despite the nested structure observed, a number of taxa and ponds deviate from this pattern (termed idiosyncratic), by occurring more frequently than expected in species-poor sites, or having assemblages dominated by species largely absent from species-rich sites. Aquatic adults of winged insects, capable of dispersal, were more highly nested than non-dispersing taxa and life-history stages. Idiosyncratic taxa were found in ponds spanning a wide range of hydroperiods, although nestedness was higher in more permanent waterbodies. Monthly sampling demonstrated a gradual increase of species richness and nestedness from pond filling to April-May, when the most temporary ponds started to dry. Although the degree of nestedness of individual pond assemblages varied from month to month, the overall degree of nestedness in the two study years was practically identical despite marked differences in hydroperiod. Our results suggest that differential colonization and environmental variation are key processes driving the nested structure of Doñana ponds, that macroinvertebrate assemblages change in a predictable manner each year in response to cycles of pond wetting and drying, and that connectivity and environmental variability maintain biodiversity in pond networks.

Does sampling method or microhabitat type determine patterns of macroinvertebrate assemblage structure detected across spatial scales in rivers?

Patterns in macroinvertebrate assemblage structure detected across spatial scales in rivers vary among studies, and it is not clear whether methodological differences in sampling methods or differences between rivers are responsible. We aimed to separate the roles of microhabitats and sampling methods in determining patterns in macroinvertebrate assemblages across spatial scales in the Johanna River, south-eastern Australia. We hypothesised that less sample-to-sample variability in the structure of macroinvertebrate assemblages would be detected using a Sürber sampler than by scrubbing stones. However, Sürber samples were more variable than individual stones, although invertebrate abundance did not differ. To examine the effect of habitat and substratum, we hypothesised that taxa richness, invertebrate abundance and sample variability would differ among leaf packs and stones. Variation among samples in taxa richness and abundance was higher among leaf packs than among cobbles, whereas variability in taxon composition was much higher among stones. Leaf packs in runs had four times as many taxa as did stones in riffles, and more individuals. Leaf packs may therefore provide a more representative sample of the assemblage than do stones. Sürber samplers may randomly subsample riffle assemblages, inflating the sample-to-sample variability detected.

Patterns of macroinvertebrate assemblages in a long‐term watershed‐scale study to address the effects of pulp and paper mill discharges in four us receiving streams

Changes in macroinvertebrate communities exposed to pulp and paper mill effluent (PPME) have been seen in mesocosm and short-term field studies. However, long-term patterns of macroinvertebrates in PPME receiving streams have not been examined. We conducted a study of 4 PPME receiving streams (Codorus Creek, PA; the Leaf River, MS; and the McKenzie and Willamette rivers, OR) over 9 y to assess temporal patterns in macroinvertebrate community structure and metrics related to PPME discharge. Study streams represented different ecoregions, warm-/cold-water systems, gradients of PPME concentration (<1%-33%), and mill process types. Bray-Curtis similarity and nonmetric multidimensional scaling showed significant community differences across sites in Codorus Creek, but differences were related to stream temperature patterns and not PPME. In the other study streams, seasonal community differences across years were greater than differences across sites. General linear models were used to examine spatial and temporal variation in macroinvertebrate metric response (% dominant taxa, density, richness, Hilsenhoff Biotic Index [HBI], Simpson's Index, and ash-free dry mass). Mean HBI scores indicated that the macroinvertebrate community reflected fair to very good water quality conditions, with water quality typically classified as "good" at most sites. Significant site differences in macroinvertebrate metric response were uncommon in the Leaf, McKenzie, and Willamette rivers but were seen in all metrics in Codorus Creek, where metric response was spatially variable. In the McKenzie River, there was an increase in mean HBI scores at sites downstream of the mill relative to 1 of the 2 upstream sites. However, significant differences were seen only between 1 upstream and downstream site, and HBI scores at all downstream sites consistently reflected "good" water quality. Significant annual differences in metric response were typical in all rivers. Water quality (pH, conductivity, total nitrogen) and habitat (velocity, depth, substrate composition) variables explained community structure patterns in the Leaf and McKenzie rivers, but macroinvertebrate-environment relationships were weak in the other 2 streams. The results of this study indicate that macroinvertebrate community structure is temporally variable and reiterate the importance of long-term studies for accurate determination of the effects of point sources such as PPME on receiving systems.

Multispatial-scale variation in benthic and snag-surface macroinvertebrate assemblages in mid-continent US great rivers

We sampled macroinvertebrate assemblages in the littoral benthos and on the surface of snags in the Upper Mississippi, Missouri, and Ohio rivers. Snag assemblages differed from benthic assemblages. Tubificids, Caenis, Tanytarsus, Cryptochironomus, Limnodrilus, and Chironomini were consistently more abundant in the benthos; Nais, Cricotopus/Orthocladius, Nematoda, and Rheotanytarsus were consistently more abundant on snags. Filterers were more abundant and gatherers were less abundant on snags than in the benthos. Snag assemblages differed among rivers and among reaches within rivers. Variation among reaches was the result of direct and indirect effects of high-dam reservoir impoundments (upper vs lower Missouri River) and low-dam impoundment for navigation (impounded vs free-flowing Upper Mississippi River). The maximum relative abundance of filterers in the lower Missouri River, which was the only long unregulated reach we studied, was related to particulate organic C and sestonic chlorophyll a concentration, which increased with distance downriver from the lowest main-stem dam. Snag diameter, snag-surface characteristics, and water depth did not affect the composition of snag assemblages, but the dominant taxa on snags in fast-velocity locations were different from the dominant taxa on snags in slow-velocity locations. Relatively few taxa showed strong longitudinal patterns in relative abundance within a reach, and only on the Missouri River. We hypothesize that the many navigation dams on the Ohio and Upper Mississippi rivers suppress the development of environmental gradients and inhibit the formation of longitudinal patterns in macroinvertebrate assemblages. Snag assemblages were dominated by a few taxa (genus-level and higher), a characteristic that might constrain the sensitivity of the assemblages to some human impacts. Sampling snag assemblages has potential for great-river bioassessment, but further research is necessary on sampling methods and sensitivity of assemblages to stressors.

The effect of biotope-specific sampling for aquatic macroinvertebrates on reference site classification and the identification of environmental predictors in Mpumalanga, South Africa

The classification of reference sites based on macroinvertebrate assemblages sampled in different aquatic biotopes in Mpumalanga, South Africa, was examined. Environmental variables that best predicted group membership for each of four classifications (stones, vegetation, sand and these three biotopes combined) were identified. Variables at several scales, including catchment, site and habitat, contributed to observed spatial patterns in macroinvertebrate assemblages. Altitude and longitude were important for combined, stones, and vegetation classifications, reflecting the importance of longitudinal zonation and geographic location, respectively. The characteristics of the substratum, including type (bedrock rapid versus cobble riffle), depth, and quality (deposition of silt on stones), were important at habitat scale. Canopy cover was identified as an important predictor in the stones classification. Geological type, which affects overall water chemistry, was important in the stones and combined classification, and temperature was important in the combined classification. Whilst this study is based on correlative data only, it demonstrates that the structure of macroinvertebrate assemblages is a function of both large-scale variables measured at catchment scale and smaller-scale variables measured at site and habitat scale. The study highlights the importance of measuring environmental variables within bioassessment programmes, especially when classifying and assessing reference sites.

Taxonomic Resolution and Quantification of Freshwater Macroinvertebrate Samples from an Australian Dryland River: The Benefits and Costs of Using Species Abundance Data

In studies using macroinvertebrates as indicators for monitoring rivers and streams, species level identifications in comparison with lower resolution identifications can have greater information content and result in more reliable site classifications and better capacity to discriminate between sites, yet many such programmes identify specimens to the resolution of family rather than species. This is often because it is cheaper to obtain family level data than species level data. Choice of appropriate taxonomic resolution is a compromise between the cost of obtaining data at high taxonomic resolutions and the loss of information at lower resolutions. Optimum taxonomic resolution should be determined by the information required to address programme objectives. Costs saved in identifying macroinvertebrates to family level may not be justified if family level data can not give the answers required and expending the extra cost to obtain species level data may not be warranted if cheaper family level data retains sufficient information to meet objectives. We investigated the influence of taxonomic resolution and sample quantification (abundance vs. presence/absence) on the representation of aquatic macroinvertebrate species assemblage patterns and species richness estimates. The study was conducted in a physically harsh dryland river system (Condamine-Balonne River system, located in south-western Queensland, Australia), characterised by low macroinvertebrate diversity. Our 29 study sites covered a wide geographic range and a diversity of lotic conditions and this was reflected by differences between sites in macroinvertebrate assemblage composition and richness. The usefulness of expending the extra cost necessary to identify macroinvertebrates to species was quantified via the benefits this higher resolution data offered in its capacity to discriminate between sites and give accurate estimates of site species richness. We found that very little information (<6%) was lost by identifying taxa to family (or genus), as opposed to species, and that quantifying the abundance of taxa provided greater resolution for pattern interpretation than simply noting their presence/absence. Species richness was very well represented by genus, family and order richness, so that each of these could be used as surrogates of species richness if, for example, surveying to identify diversity hot-spots. It is suggested that sharing of common ecological responses among species within higher taxonomic units is the most plausible mechanism for the results. Based on a cost/benefit analysis, family level abundance data is recommended as the best resolution for resolving patterns in macroinvertebrate assemblages in this system. The relevance of these findings are discussed in the context of other low diversity, harsh, dryland river systems.

Correspondence between regional delineations and spatial patterns in macroinvertebrate assemblages of boreal headwater streams

Geographical stratification may provide a useful framework for stream management programs, yet most studies testing the utility of such stratifications have been conducted in temperate regions. We studied the correspondence between regional delineations (5 ecoregions, 11 subecoregions), environmental characteristics, and benthic macroinvertebrate assemblages in 156 boreal headwater streams in Finland, using a combination of principal components analysis, nonmetric multidimensional scaling, and discriminant function analysis (DFA). Both stream characteristics and macroinvertebrate assemblage structure showed a closer correspondence to ecoregions than to subecoregions, a pattern partly attributable to the smaller number of classes at the ecoregion level. Based on environmental variables, DFA classified correctly 84.0% of the streams by ecoregion and 74.4% by subecoregion. For macroinvertebrate assemblages, 64.7% of the streams were correctly classified at the ecoregion, and 51.9% at the subecoregion level. Arctic-alpine and north boreal ecoregions supported the most distinct benthic assemblages. There were significant differences among ecoregions in mean species number, with lowest species richness in the middle boreal and highest in the south boreal streams. However, no clear latitudinal gradients in local species richness were detected. Relative abundances of functional-feeding groups also exhibited regional differences. Shredders dominated the middle boreal brown-water streams, whereas scrapers attained their highest abundances in the arctic-alpine and north boreal clear-water streams. Despite some congruence among ecoregions and macroinvertebrate assemblages, regional delineations alone do not provide a suitable background for stream biomonitoring programs. A combination of regional delineations and local characteristics probably provides a better framework for the classification of boreal headwater streams, and for the prediction of their benthic fauna.

The relationship of macroinvertebrate assemblages to water chemistry in a polluted Colorado plains stream

Macroinvertebrate assemblages and 27 water chemistry variables were investigated at 8 sampling sites over a 4-year period (1992-1995) in the plains section of the Cache la Poudre River, north central Colorado, influenced by urbanization and agricultural activities. Relationships between macroinvertebrate assemblages and water chemistry variables were examined along a longitudinal chemical gradient using ordination techniques (principal component analysis (PCA), redundancy analysis (RDA), and detrended canonical correspondence analysis (DCCA)). PCA ordination diagrams provide a reasonable two-dimensional representation of both the macroinvertebrate and environmental data. Concentrations of cations (e.g. Ca, Mg, Na, and K ions) exhibited the strongest relationship with macroinvertebrate assemblages along the river section. The inorganic nutrients (e.g. ammonia, total Kjeldahl nitrogen, and total phosphorus), suspended solids, and turbidity were also associated with macroinvertebrate assemblage structure. Temporal trends of macroinvertebrate assemblages, investigated using DCCA, showed that interannual and seasonal variations of macroinvertebrate assemblages were related to increases in concentrations of heavy metals and to decreases in concentrations of inorganic nutrients, suspended solids, and turbidity. Interannual variations were less important than seasonal changes in explaining temporal patterns of macroinvertebrate assemblages. The highest species turnover and the highest interannual and lowest seasonal variation of macroinvertebrate assemblages were found at the reference site.