Invertebrate Taxonomic Richness Research Articles

Implementation of artificial substrates for Dendropoma cristatum (Biondi 1859) reef restoration: Testing different materials and topographic designs.

Vermetid reefs are intertidal key habitats that strongly increase the biological and ecological value of the coastal ecosystems, providing ecological goods and services. In some parts of the Mediterranean Sea, this habitat is experiencing an increasing decline, due to environmental and anthropogenic pressures and the lack of officially coordinated strategies promoting its conservation at the basin scale.Moreover, experimental data testing for vermetid reef restoration is presently scant. Here we tested the potential to achieve new vermetid colonies on engineered substrates, aiming for their further transplantation to depleted reefs for restoration purposes. We investigated in the field the settlement rate of the central-Mediterranean vermetid species Dendropoma cristatum on artificial tiles made of different concrete mixtures (geopolymer concrete, pozzolanic concrete mixed with fine sand, magnesian concrete, pozzolanic concrete mixed with magnesium and coarse sand) and one plastic material (expanded polyvinyl chloride), engineered with a range of interstice shapes and sizes (i.e., holes and crevices of 1 and 2 mm), obtaining on each tile four different topographic designs. Also, the benthic fauna colonization on these engineered tiles has been monitored.While the material typology had a relative effect on the settlement of D. cristatum, the presence of specific topographic designs played an important role, not only for the reef-builder species but also for the benthic fauna. A significantly higher vermetid density and invertebrate taxonomic richness and individual abundance were associated with the hole presence on the tiles, confirming to be the preferred interstice type among those texted. Furthermore, geopolymer concrete was the material that showed higher resistance to the intertidal conditions and durability after the experiment.The production of geopolymer tiles engineered with hole interstices may be a valid option for future studies aiming at the restoration of this intertidal key habitat. However, while our achievements correspond to a higher vermetid and benthic invertebrate settlement within a few weeks of field experiment, post-settlement processes need to be considered in the perspective to restore the functionality of a degraded reef.

On the efficacy of restoration in stream networks: comments, critiques, and prospective recommendations

Swan and Brown (2017) recently addressed the effects of restoration on stream communities under the meta-community framework. Using a combination of headwater and mainstem streams, Swan and Brown (2017) evaluated how position within a stream network affected the outcome of restoration on invertebrate communities. Ostensibly, their hypotheses were partially supported as restoration had stronger effects in headwater streams: invertebrate taxonomic richness was increased and temporal variability decreased in restored reaches; however, these results were not consistent upon closer scrutiny for both the original paper (Swan and Brown 2017) and the later erratum (Swan and Brown 2018). Here, I provide a secondary analysis of the data, with hypotheses and interpretations in the context of stream, meta-community, and restoration ecology. Swan and Brown (2017, 2018) evaluated the effect of restoration on sites receiving various combinations of in-channel manipulation and riparian reforestation treatments. Given the difference in the relative importance of environmental filtering and dispersal between headwaters and mainstems and the structure of river networks, I contend that different restoration treatments have differential effects between headwaters and mainstems. I hypothesized in-channel manipulations would have more consistent effects between headwaters and mainstems compared to riparian reforestation, and I used this hypothesis to guide site selection in the re-analysis. I then compared results from the re-analysis to those presented by Swan and Brown (2017, 2018). I did not find any effects of restoration on local diversity, spatial dissimilarity, or temporal variability, let alone differential effects of restoration between headwaters and mainstems; these results are contrary Swan and Brown (2017, 2018), who reported that restoration increased taxonomic richness, increased spatial dissimilarity, and decreased temporal variability in restored headwater streams. I demonstrate further that the statistical tests conducted by Swan and Brown (2017, 2018) were invalid and, therefore, recommend the use of the results presented here. More broadly, I suggest, in agreement with Swan and Brown (2017, 2018) and a growing body of research, that river and stream restoration will likely have greater success if a regional approach is taken to designing and implementing restoration projects.

Stochastic processes and ecological connectivity drive stream invertebrate community responses to short-term drought.

Community responses to and recovery from disturbances depend on local (e.g. presence of refuges) and regional (connectivity to recolonization sources) factors. Droughts are becoming more frequent in boreal regions, and are likely to constitute a severe disturbance for boreal stream communities where organisms largely lack adaptations to such hydrological extremes. We conducted an experiment in 24 semi-natural stream flumes to assess the effects of local and regional factors on the responses of benthic invertebrate communities to a short-term drought. We manipulated flow (drought vs. constant-flow), spatial arrangement of leaf litter patches (aggregated vs. evenly distributed) and colonization from regional species pool (enhanced vs. ambient connectivity) to test the combined effects of disturbance, resource arrangement and connectivity on the structural and functional responses of benthic invertebrate communities. We found that a drought as short as 1week reduced invertebrate taxonomic richness and abundance, mainly through stochastic extinctions. Such changes in richness were not reflected in functional diversity. This suggests that communities were characterized by a high degree of functional redundancy, which allowed maintenance of functional diversity despite species losses. Feeding groups responded differently to drought, with organic matter decomposers responding more than scrapers and predators. Three weeks were insufficient for complete invertebrate community recovery from drought. However, recovery was greater in channels subjected to enhanced connectivity, which increased taxonomic diversity and abundance of certain taxa. Spatial configuration of resources explained the least variation in our response variables, having a significant effect only on invertebrate abundance and evenness (both sampling occasions) and taxonomic richness (end of recovery period). Even a short drought, if occurring late in the season, may not allow communities to recover before the onset of winter, thus having a potentially long-lasting effect on stream communities. For boreal headwaters, extreme dewatering poses a novel disturbance regime that may trigger substantial and potentially irreversible changes. An improved understanding of such changes is needed to underpin adaptive management strategies in these increasingly fragmented and disturbed ecosystems.

Fish and benthic invertebrate relationship and their association to environmental variables in tropical sandy beaches

Fish and benthic invertebrates are important groups that inhabit shallow coastal areas. Many studies use these two groups separately to answer questions related to environmental relationships, but few assess the correlation between these two groups. This study aimed to assess correlation between richness and composition of fish and benthic invertebrate assemblages and to evaluate their responses to environmental variables in sandy beaches in a tropical coastal area in south-eastern Brazil. We tested for a correlation between fish and benthic invertebrates and evaluated which environmental variables influenced each group. Fish and invertebrate taxonomic richness were not correlated across sites. In addition, the two groups were not significantly correlated, even after controlling the effects of the environmental variables. The taxonomic richness of the two groups were influenced by different set of environmental drivers: fish were influenced mainly by the physicochemical variables, being positively correlated with salinity and dissolved oxygen, and negatively with temperature, whereas invertebrates richness were related mainly to granulometric variables, decreasing in fine and very fine sediment. Fish and invertebrate showed similar patterns with more influence of environmental variables than biotic variables that had comparatively more effects on the invertebrate than on the fish assemblage. Spatial segregation in species distribution along the beaches were found with the Gerreid fish predominating in semi-exposed beaches whereas the sparid Diplodus argenteus, the haemulid Orthopristis ruber and the clupeids Harengula clupeola and Sardinella brasiliensis predominated in the exposed beaches. The Polychaetae families Syllidae and Dorvilleidae, and isopod of the family Cirolanidae predominated in semi-protect beaches, whereas polychaetas of the families Glyceridae and Saccocirridae predominated in the exposed beaches. In this study, we showed that fish and benthic invertebrates are influenced by different environmental variables in tropical sandy beaches and no significant correlation was found between these two taxonomic groups. Our findings are a step to a better understanding of the fish-benthic invertebrate relationship and a contribution to management policies aiming the conservation of tropical coastal areas.

A stronger statistical test of stream restoration experiments

Swan and Brown (2017) recently addressed the effects of restoration on stream communities under the meta-community framework. Using a combination of headwater and mainstem streams, Swan and Brown (2017) evaluated how position within a stream network affected the outcome of restoration on invertebrate communities. Ostensibly, their hypotheses were partially supported as restoration had stronger effects in headwater streams: invertebrate taxonomic richness was increased and temporal variability decreased in restored reaches; however, these results were not consistent upon closer scrutiny for both the original paper (Swan and Brown 2017) and the later erratum (Swan and Brown 2018). Here, I provide a secondary analysis of the data, with hypotheses and interpretations in the context of stream, meta-community, and restoration ecology. Swan and Brown (2017, 2018) evaluated the effect of restoration on sites receiving various combinations of in-channel manipulation and riparian reforestation treatments. Given the difference in the relative importance of environmental filtering and dispersal between headwaters and mainstems and the structure of river networks, I contend that different restoration treatments have differential effects between headwaters and mainstems. I hypothesized in-channel manipulations would have more consistent effects between headwaters and mainstems compared to riparian reforestation, and I used this hypothesis to guide site selection in the re-analysis. I then compared results from the re-analysis to those presented by Swan and Brown (2017, 2018). I did not find any effects of restoration on local diversity, spatial dissimilarity, or temporal variability, let alone differential effects of restoration between headwaters and mainstems; these results are contrary Swan and Brown (2017, 2018), who reported that restoration increased taxonomic richness, increased spatial dissimilarity, and decreased temporal variability in restored headwater streams. I demonstrate further that the statistical tests conducted by Swan and Brown (2017, 2018) were invalid and, therefore, recommend the use of the results presented here. More broadly, I suggest, in agreement with Swan and Brown (2017, 2018) and a growing body of research, that river and stream restoration will likely have greater success if a regional approach is taken to designing and implementing restoration projects.

Stream invertebrate communities are primarily shaped by hydrological factors and ultimately fine-tuned by local habitat conditions

The environmental factors that determine species richness and community structure in running waters have long been studied, but how these factors hierarchically and/or interactively influence benthic communities remains unclear. To address this research gap, we identified the principal abiotic factors that determine the taxonomic composition and functionality of stream macroinvertebrate communities and explored possible hierarchical and/or interactive patterns. We analyzed a large dataset from Greek rivers, and compared multiple macroinvertebrate metrics and traits between perennial and intermittent watercourses during wet and dry periods. We found that macroinvertebrates were primarily influenced by two ecological gradients: (i) aquatic vegetation-conductivity; and (ii) water temperature-canopy cover. Macroinvertebrates in perennial rivers were mainly influenced by the first gradient, whereas in intermittent rivers both gradients were important. Taxonomic richness and diversity were higher and temporally stable within years in perennial rivers, whereas in intermittent rivers, these metrics peaked during early summer, before the onset of streambed desiccation. The two environmental gradients determined the taxonomic richness and diversity in both spring and summer; however, a clear influence of hydrological factors (wetted width, water depth, flow velocity and discharge) was observed only in the intermittent samples. We conclude that the benthic invertebrate taxonomic richness and diversity in highly variable environments is primarily determined by hydrological variation and ultimately fine-tuned by local habitat factors. As climate change scenarios predict severe modification of hydrological and local habitat factors, this study concludes that in river management, hydrological restoration should be prioritized over other local habitat factors by maintaining natural hydrological variability, to ensure aquatic community richness and diversity.

Top-down control of invertebrates by Ninespine Stickleback in Arctic ponds

AbstractDespite their widespread presence in northern-latitude ecosystems, the ecological role of Ninespine Stickleback Pungitius pungitius is not well understood. Ninespine Stickleback can occupy both top and intermediate trophic levels in freshwater ecosystems, so their role in food webs as a predator on invertebrates and as a forage fish for upper level consumers probably is substantial. We introduced Ninespine Sticklebacks to fishless ponds to elucidate their potential effects as a predator on invertebrate communities in Arctic lentic freshwaters. We hypothesized that Ninespine Stickleback would affect freshwater invertebrate communities in a top-down manner. We predicted that the addition of Ninespine Sticklebacks to fishless ponds would: 1) reduce invertebrate taxonomic richness, 2) decrease overall invertebrate abundance, 3) reduce invertebrate biomass, and 4) decrease average invertebrate body size. We tested our hypothesis at 2 locations by adding Ninespine Stickleback to isolated ponds and compa...

Elevational Shifts of Freshwater Communities Cannot Catch up Climate Warming in the Himalaya

Climate warming threatens biodiversity at global, regional and local levels by causing irreversible changes to species populations and biological communities. The Himalayan region is highly vulnerable to climate warming. This calls for efficient environmental management strategies because biodiversity monitoring is costly, particularly for the developing countries of the Himalaya. Species distribution modeling (SDM) represents a tool that can be used to identify vulnerable areas where biodiversity monitoring and conservation are required most urgently and can be prioritized. Here, we investigated the potential present-day community compositions of river invertebrates in the central and eastern Himalayas and predicted changes in community compositions in future decades using SDMs. We then quantified the climate-induced range shifts of benthic invertebrates along the elevational gradient and tested whether the predicted community shift is fast enough to fully compensate for the projected climate warming. Our model predicts future increases in benthic invertebrate taxonomic richness. Further, projected community shifts are characterized by the movement of warm-dwellers to higher elevations and losses in cold-dwellers. The predicted model shows that benthic invertebrate communities would not be able to compensate climate warming through uphill migration and thus would accumulate climatic debts. Our findings suggest that the ongoing warming effect would cause continued elevational range shifts of mountain river communities.

Declines and extinctions of mountain yellow‐legged frogs have small effects on benthic macroinvertebrate communities

AbstractSpecies extinctions have the potential to dramatically reshape ecological communities. In the Sierra Nevada mountains of California, the emergence of a lethal amphibian pathogen (Batrachochytrium dendrobatidis) drives mountain yellow‐legged frog (Rana muscosa and Rana sierrae) populations to local extinction. Prior to population declines, these frogs and their tadpoles were abundant, high‐level predators and grazers with high trophic connectance. To quantify how these low diversity aquatic macroinvertebrate communities respond to nonrandom single‐species local extinctions, we quantified aquatic macroinvertebrate communities using two approaches: a natural experiment (“Resurveys”) and a large‐scale synoptic observational study (“Snapshot” surveys). In the Resurveys, we compared benthic macroinvertebrate communities in 22 Sierra Nevada alpine lakes that we categorized as either having extant frog populations, experiencing ongoing disease‐driven frog declines, or having previously experienced local disease‐driven frog extirpation. In the Resurveys, taxonomic richness was about one taxa (17%) higher in lakes where frogs were declining or extinct, compared to lakes where frogs were extant. However, multivariate analyses revealed no strong dissimilarities among Resurvey communities, and there were no differences in the abundances of individual taxa between lakes in the frogs extant, declining, or extinct categories. In the Snapshot surveys, we reanalyzed previously collected data from a large‐scale survey of 157 lakes with and without frogs. In the Snapshot survey, invertebrate taxonomic richness was less than one taxa (9%) lower in lakes without frogs, and multivariate analyses again indicated only small differences between lakes with and without frogs. Overall, disease‐driven mountain yellow‐legged frog extinctions had small effects on lake benthic macroinvertebrate communities, with no large changes in invertebrate abundance, richness or evenness, no clear secondary extinctions or invasions, and few taxa showing distinct responses to frog extinctions. Our study highlights how even for conspicuous, highly connected, omnivorous taxa that are experiencing large, rapid, and widespread declines and extinctions, the ecological effects of extinctions will sometimes be small and subtle.

The Impact of Landscape Complexity on Invertebrate Diversity in Edges and Fields in an Agricultural Area.

Invertebrate diversity is important for a multitude of ecosystem services and as a component of the larger ecological food web. A better understanding of the factors influencing invertebrate taxonomic richness and diversity at both local and landscape scales is important for conserving biodiversity within the agricultural landscape. The aim of this study was to determine if invertebrate richness and diversity in agricultural field interiors and edges in central Illinois, USA, were related to the complexity of the surrounding landscape. Our results show taxonomic richness and diversity in field edges is positively related to large scale landscape complexity, but the relationship is negative for field interiors. These unexpected results need further study.

Enhancing the Biodiversity of Ditches in Intensively Managed UK Farmland.

Drainage ditches, either seasonally flooded or permanent, are commonly found on intensively managed lowland farmland in the UK. They are potentially important for wetland biodiversity but, despite their ubiquity, information on their biodiversity and management in the wider countryside is scarce. We surveyed 175 ditches for their physical and chemical characteristics, spatial connectivity, plant communities and aquatic invertebrates in an area of intensively managed farmland in Oxfordshire, UK and collected information on ditch management from farmer interviews. Water depth and shade had a small impact on the diversity of plant and invertebrate communities in ditches. Increased shade over the ditch channel resulted in reduced taxonomic richness of both channel vegetation and aquatic invertebrates and channel vegetation cover was lower at shaded sites. Invertebrate taxonomic richness was higher when water was deeper. Spatial connectivity had no detectable impact on the aquatic invertebrate or plant communities found in ditches. The number of families within the orders Ephemeroptera, Plecoptera and Trichoptera (EPT), which contain many pollution-sensitive species, declined with decreasing pH of ditch water. As time since dredging increased, the number of EPT families increased in permanent ditches but decreased in temporary ditches. Whether or not a ditch was in an agri-environment scheme had little impact on the reported management regime or biodiversity value of the ditch. Measures for increasing the amount of water in ditches, by increasing the water depth or promoting retention of water in ditches, could increase the biodiversity value of ditches in agricultural land. Some temporary ditches for specialised species should be retained. Reducing the amount of shade over narrow ditches by managing adjacent hedgerows is also likely to increase the species diversity of plant and invertebrate communities within the ditch. We recommend that to preserve or enhance the biodiversity value of ditches, and improve their ecosystem service delivery, management prescriptions for hedgerows adjacent to ditches should differ from those aimed at hedgerows only.

Earthquakes, catastrophic sediment additions and the response of urban stream communities

Disturbance events can regularly impact stream ecosystems; however, large-scale catastrophic disturbances are rare. From September 2010 to September 2011 Christchurch City experienced over 8500 earthquakes including a magnitude 7.1. One consequence was catastrophic additions of silt and sand into waterways throughout the city. Of 161 km of permanent waterways, 102 km (63%) were affected by earthquake siltation. Benthic invertebrates and fish communities were compared across 16 streams with differing siltation. Invertebrate taxonomic richness decreased significantly (mean 17 taxa reduced to 10 taxa) and EPT taxa (Ephemeroptera, Plecoptera and Trichoptera) were removed entirely from streams receiving heavy siltation. Fish richness and density decreased significantly, with fish absent from some heavily silted streams. Many of these urban streams are sourced from springs and their stable flows and low gradient limit their ability to flush sediment. We predict that without human intervention there will be a long-term sediment legacy and it may take many years for these streams to recover from this catastrophic disturbance.

Weak concordance between fish and macroinvertebrates in Mediterranean streams.

Although anthropogenic degradation of riverine systems stimulated a multi-taxon bioassessment of their ecological integrity in EU countries, specific responses of different taxonomic groups to human pressure are poorly investigated in Mediterranean rivers. Here, we assess if richness and composition of macroinvertebrate and fish assemblages show concordant variation along a gradient of anthropogenic pressure in 31 reaches across 13 wadeable streams in central Italy. Fish and invertebrate taxonomic richness was not correlated across sites. However, Mantel test showed that the two groups were significantly, albeit weakly, correlated even after statistically controlling for the effect of environmental variables and site proximity. Variance partitioning with partial Canonical Correspondence Analysis showed that the assemblages of the two groups were influenced by different set of environmental drivers: invertebrates were influenced by water organic content, channel and substratum features, while fish were related to stream temperature (mirroring elevation) and local land-use. Variance partitioning revealed the importance of biotic interactions between the two groups as a possible mechanisms determining concordance. Although significant, the congruence between the groups was weak, indicating that they should not be used as surrogate of each other for environmental assessments in these Mediterranean catchments. Indeed, both richness and patterns in nestedness (i.e. where depauperate locations host only a subset of taxa found in richer locations) appeared influenced by different environmental drivers suggesting that the observed concordance did not result from a co-loss of taxa along similar environmental gradients. As fish and macroinvertebrates appeared sensitive to different environmental factors, we argue that monitoring programmes should consider a multi-assemblage assessment, as also required by the Water Framework Directive.

Invertebrates and sestonic matter in an advancing wetted front travelling down a dry river bed (Albarine, France)

Temporary rivers are shifting mosaics of aquatic and terrestrial habitat driven by hydrologic variability. Advancing wetted fronts (AWFs) that rewet dry river beds are unpredictable events, and knowledge about their composition and role in habitat mosaics is scarce. We collected dead and living terrestrial invertebrates, aquatic invertebrates, and sestonic matter (i.e., suspended sediments and organic matter) entrained by flow in an AWF travelling downstream over a 7-km-long dry reach. We collected samples at 12 sites along the rewetting reach and at 3 sites in the upstream perennial reach of the Albarine River, France. Invertebrates in the AWF were mainly of terrestrial origin and organic matter was essentially coarse (>5 mm). Terrestrial invertebrate density and taxonomic richness and sestonic matter concentration were several orders of magnitude higher in the AWF than in the perennial reach. However, only terrestrial invertebrate taxonomic richness increased longitudinally. At least ⅓ of terrestrial taxa could have survived submersion, and the density and taxonomic richness of these taxa decreased downstream. These results indicate that terrestrially derived material is stored downstream during rewetting where it could greatly stimulate in-stream aquatic productivity and succession in terrestrial invertebrates along the riparian zone. In contrast, entrained aquatic taxa represented ∼15% of the benthic taxa collected 1 mo after rewetting, indicating a low contribution of AWFs to benthic invertebrate succession. In the context of global change and increasing appropriation of water resources by humans, our results suggest that conceptual models of invertebrate dynamic and organic matter processing in rivers should account for dry phases and transitional periods from dry to wet conditions.

Do productivity and disturbance interact to modulate macroinvertebrate diversity in streams?

Although disturbance and productivity are clearly strong influences on lotic diversity, rarely have their interactive effects been studied in running water systems. We hypothesised that the presence or absence of canopy cover in streams would alter productivity- disturbance-diversity relationships due to differential effects on the food base, and tested this hypothesis in 47 mountain streams in the central North Island of New Zealand. Canopy cover had no influence on algal biomass in these streams, but a link between distur- bance and productivity was found in open canopy streams where taxonomic richness of invertebrates increased log-linearly with increasing algal biomass and peaked at intermediate levels of disturbance. Community evenness declined with disturbance, but only at closed canopy sites where both invertebrate taxonomic richness and Simpson's diversity index were higher. Although there was a peak in richness at intermediate rates of disturbance, our results do not directly match predictions of the dynamic equilibrium model which predicts that the level of disturbance maximising diversity interacts with habitat productiv- ity. Rather, we suggest the combined effects of productivity and disturbance are additive rather than multiplicative such that productivity simply sets the upper limit to richness in streams.

The influence of fish farming intensification on taxonomic richness and biomass density of macrophyte-dwelling invertebrates in French fishponds

Key-words: macroinvertebrates, taxonomic richness, biomass density, macrophytes, fish farming Fishponds are man-made ecosystems where fish farming may strongly interfere with biodiversity. Intensified practices could be suspected to have a negative impact on animal and plant communities. We investigated the hypothesis that, in French fishponds, taxonomic richness and biomass density of macrophyte-dwelling macro-invertebrates could be influenced by fish stock density and pond fertilization. With a sample of 95 water bodies from three of the most important fishpond regions, studied in 2000, 2001 or 2002, we compared a series of models in which macrophyte cover (in three classes), emergent shore vegetation (in % of pond area) and invertebrate biomass in pond sediment were also considered. Among explanatory variables, macrophyte and helophyte abundance were included in the best models explaining variation in invertebrate taxonomic richness and in biomass density. Taxonomic richness was lower when abundance of both macrophytes and emergent shore vegetation was low (< 10% and < 7.5%, respectively). Biomass density was higher when macrophyte cover was 10% provided that emergent vegetation was abundant ( 7.5%). We conclude that fish farming intensification in French fishponds may affect aquatic invertebrate communities, mainly through its impact on the development of aquatic vegetation.

Habitat and Biodiversity of On-Farm Water Storages: A Case Study in Southeast Queensland, Australia

On-farm water storages (locally known as farm dams or farm ponds) are an important part of many agricultural landscapes, as they provide a reliable source of water for irrigation and stock. Although these waterbodies are artificially constructed and morphologically simple, there is increasing interest in their potential role as habitat for native flora and fauna. In this article, we present results from a case study which examined the habitat characteristics (such as water physical and chemical parameters, benthic metabolism, and macrophyte cover) and the macrophyte and macroinvertebrate biodiversity of eight farm ponds on four properties in the Stanley Catchment, Southeast Queensland, Australia. Each landowner was interviewed to allow a comparison of the management of the ponds with measured habitat and biodiversity characteristics, and to understand landowners' motivations in making farm pond management decisions.The physical and chemical water characteristics of the study ponds were comparable to the limited number of Australian farm ponds described in published literature. Littoral zones supported forty-five macroinvertebrate families, with most belonging to the orders Hemiptera, Coleoptera, Odonata, and Diptera. Invertebrate community composition was strongly influenced by littoral zone macrophyte structure, with significant differences between ponds with high macrophyte cover compared to those with bare littoral zones. The importance of littoral zone macrophytes was also suggested by a significant positive relationship between invertebrate taxonomic richness and macrophyte cover.The landowners in this study demonstrated sound ecological knowledge of their farm ponds, but many had not previously acknowledged them as having high habitat value for native flora and fauna. If managed for aquatic organisms as well as reliable water sources, these artificial habitats may help to maintain regional biodiversity, particularly given the large number of farm ponds across the landscape.

Physico‐chemical parameters and invertebrate faunas of three lake inflows and outlets in Westland, New Zealand

Abstract Selected physico‐chemical factors and the composition of faunas in inflow and outlet streams of three South Westland lakes (Kaniere, Mapourika, and Wahapo) were investigated from December 1988 to January 1990. Three sampling sites were used in each river system, the first 1 km above the inlet, another immediately below the lake, and the third 1–5 km further downstream. Dissolved organic carbon concentrations, alkalinity, and conductivity were only slightly influenced by the presence of a lake. Summer and winter water temperatures were elevated at lake outlets, but generally declined again downstream. Substrate size, stability, and homogeneity were also greater at artificial lake outlets. Invertebrate taxonomic richness was lowest at lake outlets, intermediate in inlets streams, and greatest at downstream sites. Inflow stream faunas were dominated by Deleatidium (Ephemeroptera: Leptophlebiidae), whereas lake outlets were dominated by Hydropsychidae, Simuliidae, and Mollusca; downstream Simuliidae,...