Small Aquatic Ecosystems Research Articles

Water-filled leaf axils in teasel plants: A study of often overlooked aquatic habitats

Teasels (Dipsacus spp.) are among the few European plant species that can create small aquatic ecosystems, known as phytotelmata, in their leaf axils. However, these unique environments have received little research attention. We performed the first detailed study of phytotelmata in teasels, aiming to describe the physical habitat and macroinvertebrate communities across different leaf axil levels. We explored 64 phytotelmata on 20 teasel plants in Slovakia (Central Europe). These small aquatic ecosystems contained less than 100 ml of water, exhibited a pH ranging from slightly acidic to neutral, had very low oxygen content, and showed highly variable conductivity. We collected more than 1000 larvae of Diptera, representing at least ten aquatic invertebrate taxa. The dominant species found in these communities were the chironomid Metriocnemus eurynotus (Holmgren, 1883), followed by ceratopogonids of the genus Dasyhelea. The oldest, bottom-situated phytotelmata showed the highest invertebrate density and species richness, suggesting an important role of ecosystem age and the probability of colonization in the community assembly process. These highly replicated ecosystems with simple communities may serve as useful models for studying various ecological phenomena such as metacommunity dynamics, succession, community assembly, biodiversity-ecosystem functioning or mutualistic interactions.

Unsupervised Machine Learning and Data Mining Procedures Reveal Short Term, Climate Driven Patterns Linking Physico-Chemical Features and Zooplankton Diversity in Small Ponds

Machine Learning (ML) is an increasingly accessible discipline in computer science that develops dynamic algorithms capable of data-driven decisions and whose use in ecology is growing. Fuzzy sets are suitable descriptors of ecological communities as compared to other standard algorithms and allow the description of decisions that include elements of uncertainty and vagueness. However, fuzzy sets are scarcely applied in ecology. In this work, an unsupervised machine learning algorithm, fuzzy c-means and association rules mining were applied to assess the factors influencing the assemblage composition and distribution patterns of 12 zooplankton taxa in 24 shallow ponds in northern Italy. The fuzzy c-means algorithm was implemented to classify the ponds in terms of taxa they support, and to identify the influence of chemical and physical environmental features on the assemblage patterns. Data retrieved during 2014 and 2015 were compared, taking into account that 2014 late spring and summer air temperatures were much lower than historical records, whereas 2015 mean monthly air temperatures were much warmer than historical averages. In both years, fuzzy c-means show a strong clustering of ponds in two groups, contrasting sites characterized by different physico-chemical and biological features. Climatic anomalies, affecting the temperature regime, together with the main water supply to shallow ponds (e.g., surface runoff vs. groundwater) represent disturbance factors producing large interannual differences in the chemistry, biology and short-term dynamic of small aquatic ecosystems. Unsupervised machine learning algorithms and fuzzy sets may help in catching such apparently erratic differences.

Methane and nitrous oxide have separated production zones and distinct emission pathways in freshwater aquaculture ponds

Aquaculture systems receive intensive carbon (C) and nitrogen (N) loadings, and are therefore recognized as major anthropogenic sources of methane (CH4) and nitrous oxide (N2O) emissions. However, the extensively managed aquaculture ponds were identified as a hotspot of CH4 emission but just a weak N2O source. Here, we investigate annual CH4 and N2O fluxes from three earthen ponds used for crab culture, of different sizes, in southeast China. Our purposes are to identify the spatiotemporal variations of CH4 and N2O emissions and their components among ponds and to evaluate the zone for CH4 and N2O production. Static chamber-measured CH4 flux ranged from 0.03 to 64.7 mg CH4 m‒2 h‒1 (average: 9.02‒14.3 mg CH4 m‒2 h‒1), and temperature, followed by dissolved organic C (DOC) concentration, and redox potential, were the primary drivers of seasonal CH4 flux patterns. Annual mean diffusive CH4 flux was 1.80‒2.34 mg CH4 m‒2 h‒1, and that by ebullition was up to 7.20‒12.0 mg CH4 m‒2 h‒1 (79.1‒83.5% of the total CH4 flux). Annual CH4 emission was positively correlated with sediment DOC concentration but negatively (P < 0.05) correlated with water depth across ponds, with the highest CH4 emission occurred in a pond with low water depth and high DOC concentration. The calculated diffusive N2O flux by the gas transfer velocity was 0.32‒0.60 times greater than the measured N2O emission, suggesting that N2O in water column can not only evade as water-air fluxes but diffuse downwards and to be consumed in anaerobic sediments. This also indicates that N2O was primarily produced in water column. The highly reduced condition and depletion of NO3‒-N in sediments, can limit N2O production from both nitrification and denitrification but favor N2O consumption, leading the ponds to become a weak source of N2O annually and even a sink of N2O in summer. Our results highlight that the current global CH4 budget for inland waters is probably underestimated due to a lack of data and underestimation of the contribution of ebullitive CH4 flux in small lentic waters. The downwards N2O diffusion from the water column into sediment also indicates that the extensively-used model approach based on gas transfer velocity potentially overestimates N2O fluxes, especially in small eutrophic aquatic ecosystems.

Bombina variegata (Linnaeus, 1758) in rain pools in the Carpathian Mountains (Slovakia)

Abstract Rain pools (pluviotelmata or puddles) are common, small and non-permanent aquatic ecosystems. Data on the use of rain pools by amphibian taxa in the Carpathian Mountains, especially in Slovakia, are rare. In this study we describe the occurrence of Bombina variegata (Linnaeus, 1758), which may use these small aquatic ecosystems as part of their complex life cycle or where they spend their larval period. The most important hydroperiodic factors affecting the vertebrate fauna were the volume and area of the rain pools, the presence (respectively the absence) of shade, water temperature, biotope structure and the presence of several chemical compounds (NO− 3, GH, KH, pH). This study confirms that micro-habitats, such as rain pools, may play an important role for suitable reproduction sites of B. variegata, as stated by several authors from the different countries and regions of its large distributional range. At the same time, data on the presence or absence of different taxa with important conservation status in the monitored habitat aid in the detection of species.

Species richness and biodiversity significance of alpine micro-waterbody systems in Gaoligong Mountain, Northwest Yunnan, China

Water quality, size, connectivity and other physical properties of hydrological systems might have different functions in the formation and maintenance of biodiversity, but this remains mostly unclear due to the lack of undisturbed sites for experimental modelling. Alpine freshwater habitats such as micro-waterbodies (MWB) represent a kind of natural system suitable for biodiversity research. In order to assess potential linkages between environmental factors, connectivity of MWBs and aquatic species richness, we conducted a pilot study in two separated MWB systems located in Gaoligong Mountain, northwest Yunnan province, China. A total of 27 MWBs have been analyzed, including 22 connected and 5 isolated bodies. 13 conventional environmental factors were tested while all kinds of aquatic macro-organisms were collected and classified. Results showed a high environmental heterogeneity among MWBs and significant differences between the two systems but only a few environmental variables such as the depth of soil bottom, total Nitrogen and altitude were related to species richness and the formation of the community structure. As a benefit from the high environmental heterogeneity, the cascaded MWB systems provided divergent habitats able to support species richness at a higher level than the same number of randomly selected MWBs. This finding supports the idea that habitat connectivity matters also in extremely small aquatic ecosystems. Moreover, although still a preliminary result, a polarization effect within connected chains where edge MWBs host higher taxa and endemic taxa richness as well as larger populations, was detectable. This study gives interesting insights on the spatial processes driving community structure and a new prospective for biodiversity conservation. Since alpine MWBs have significant effects on the maintenance of watershed biodiversity, further research on such small and crucial ecosystems is encouraged.

Drivers of ecosystem metabolism in restored and natural prairie wetlands

Elucidating drivers of aquatic ecosystem metabolism is key to forecasting how inland waters will respond to anthropogenic changes. We quantified gross primary production (GPP), respiration (ER), and net ecosystem production (NEP) in a natural and two restored prairie wetlands (one “older” and one “recently” restored) and identified drivers of temporal variation. GPP and ER were highest in the older restored wetland, followed by the natural and recently restored sites. The natural wetland was the only net autotrophic site. Metabolic differences could not be definitively tied to restoration history, but were consistent with previous studies of restored wetlands. Wetlands showed similar metabolic responses to abiotic variables (photosynthetically active radiation, wind speed, temperature), but differed in the direct and interactive influences of biotic factors (submersed aquatic vegetation, phytoplankton). Drivers and patterns of metabolism suggested the importance of light over nutrient limitation and the dominance of autochthonous production. Such similarity in ecosystem metabolism between prairie wetlands and shallow lakes highlights the need for a unifying metabolic theory for small and productive aquatic ecosystems.

Driving factors of temporary and permanent shallow lakes in and around Hwange National Park, Zimbabwe

Small aquatic ecosystems in semi-arid environments are characterised by strong seasonal water level fluctuations. In addition, land use as well as artificial pumping of groundwater to maintain water resources throughout the dry season may affect the functioning of aquatic ecosystems. In this study, we investigated pans situated in and around Hwange National Park, Zimbabwe, where certain waterholes are artificially maintained during the dry season for conservation purposes. We monitored 30 temporary and permanent waterholes for 7 months across the wet and dry seasons in 2013, and analysed them for standard parameters to investigate seasonal variations, assess the effects of land use and pumping on lake functioning, and determine the driving factors of these aquatic systems. Results show an increase in conductivity, hardness, and turbidity when temporary pans dry up and permanent ones are filled with groundwater. Prominent parameters explaining the diversity of aquatic ecosystems are water hardness, conductivity, turbidity, and the presence of vegetation. Seasonality differences in certain parameters suggest the influence of water level fluctuations associated with rainfall, evaporation, and pumping activities. Further, the distinction between turbid pans and those with clear water and vegetation suggests the alternative functioning of pans. Land use had no significant effects, while the effects of pumping are discussed. In times of water scarcity, animals gather around artificially maintained waterholes and foul water with faeces and urine, thus inducing water eutrophication.

Daphnia diversity in water bodies of the Po River Basin

&lt;p&gt;Shallow water bodies dominate the areal extent of continental waters and host a proportion of biodiversity higher than the percentage of Earth’s surface they cover. &lt;em&gt;Daphnia&lt;/em&gt; is a key component of small aquatic ecosystems food webs. Here we present the result of a survey in 24 ponds located in the core of Po river Basin, to assess the actual spreading of &lt;em&gt;Daphnia&lt;/em&gt; species in one of the most productive areas of the Northern hemisphere. By using diagnostic genetic markers (&lt;em&gt;12S rRNA &lt;/em&gt;and &lt;em&gt;ND5 &lt;/em&gt;genes) we identified five &lt;em&gt;Daphnia&lt;/em&gt; species: &lt;em&gt;D. ambigua&lt;/em&gt;, &lt;em&gt;D. curvirostris&lt;/em&gt;, &lt;em&gt;D. longispina&lt;/em&gt;, &lt;em&gt;D. obtusa&lt;/em&gt; and &lt;em&gt;D. pulex &lt;/em&gt;in fourteen ponds. Additional analyses of two nuclear genes (&lt;em&gt;LdhA&lt;/em&gt; and &lt;em&gt;Rab4&lt;/em&gt;) revealed that &lt;em&gt;D. pulex&lt;/em&gt; in the study area is native European strain. In opposite, &lt;em&gt;D. ambigua&lt;/em&gt; shared haplotype with the North-Eastern American lineage that was introduced to Europe by long-distance dispersal. In the Po river Basin we identified a highly divergent lineage of &lt;em&gt;D. longispina &lt;/em&gt;group that formed a clade with individuals from northern European Russia and might represent a new &lt;em&gt;Daphnia &lt;/em&gt;species. &lt;em&gt;Daphnia&lt;/em&gt; species in the Cremona province have European origin, except for &lt;em&gt;D. ambigua&lt;/em&gt; which is a North American species spreading across Europe. Future attention will require monitoring of invasive species, particularly &lt;em&gt;D. ambigua&lt;/em&gt; and the North American invasive clone of &lt;em&gt;D. pulex &lt;/em&gt;that is already present in Northern Italy. &lt;/p&gt;

&lt;p class="HeadingRunIn"&gt;&lt;strong&gt;Distribution and abundance of adult caddisflies (Trichoptera) in the vicinity of food and pharmaceutical factories&lt;/strong&gt;&lt;/p&gt;

We investigated the abundance of adult caddisflies in the precincts of food and pharmaceutical factories. The objective of this study is to clarify the abundance of adult caddisflies from the cooling tower and catch basin by a light trap in the vicinity of food and pharmaceutical factories. In addition, to clarify the role of vegetation near factories for adult caddisflies, an investigation of the number of insects using vegetation was conducted with light traps. The light traps were operated in mid May−early June, end July−mid August, and mid−end October 2009. At St. 1, the highest number of hydroptilid adults was collected in cherry trees (64 individuals), followed by the cooling tower (38 individuals), and the catch basin (only one individual). On the other hand, the highest number of hydroptilid adults at St. 2 was collected in the catch basin (15 individuals), followed by cherry trees (7 individuals), and cooling tower (6 individuals). No hydroptilid adults were collected in the cooling tower and vegetation at St. 3. These results suggest that factories may be exposed to periodic invasions of adults from not only natural aquatic ecosystems, rivers and lakes, but also small man-made aquatic ecosystems, cooling towers and catch basins, in the vicinity of factories.

Small Boreal Lake Ecosystem Evolution under the Influence of Natural and Anthropogenic Factors: Results of Multidisciplinary Long-Term Study

Small aquatic ecosystems of the boreal zone are known to be most sensitive indicators of on-going environmental change as well as local anthropogenic pressure, while being highly vulnerable to external impacts. Compared to rather detailed knowledge of the evolution of large and small lakes in Scandinavia and Canada, and large lakes in Eurasia, highly abundant small boreal lakes of northwest Russia have received very little attention, although they may become important centers of attraction of growing rural population in the near future. Here we present the results of a multidisciplinary, multi-annual study of a small boreal humic lake of NW Russia. A shallow (3 m) and a deep (16 m) site of this lake were regularly sampled for a range of chemical and biological parameters. Average multi-daily, summer-time values of the epilimnion (upper oxygenated) layer of the lake provided indications of possible trends in temperature, nutrients, and bacterio-plankton concentration that revealed the local pollution impact in the shallow zone and overall environmental trend in the deep sampling point of the lake. Organic phosphorus, nitrate, and lead were found to be most efficient tracers of local anthropogenic pollution, especially visible in the surface layer of the shallow site of the lake. Cycling of trace elements between the epilimnion and hypolimnion is tightly linked to dissolved organic matter speciation and size fractionation due to the dominance of organic and organo-ferric colloids. The capacity of lake self-purification depends on the ratio of primary productivity to mineralization of organic matter. This ratio remained &gt;1 both during winter and summer periods, which suggests a high potential of lake recovery from the input of allochthonous dissolved organic matter and local anthropogenic pollution.

Effect of agricultural landscape characteristics on the\xa0hydrobiota structure in small water bodies

Understanding the influence of environmental factors on the hydrobiota structure of small aquatic ecosystems is essential for effective landscape management. In this study of 165 small water bodies situated in the lowland high-productive agricultural landscape of western Poland we evaluate the effect of catchment, buffer zone, water body and water quality parameters on macrophyte functional groups (nymphaeids, elodeids, pleustophytes, helophytes) and zooplankton diversity. The potential pressure of the catchment on ponds was high (mean Ohle index 140). For macrophytes, shore length and depth of pond were highly significant and, subsequently the type of catchment and buffer, while for zooplankton, apart from water depth, trophic features of the habitat were decisive. Cluster analysis was used to identify functional types of water bodies on the basis of catchment and buffer zone attributes. Regardless of physico-geographical macroregion, water bodies of arable catchments with herbage buffer prevailed in a landscape. For protection and prevention of ecological deterioration of ponds and stability of trophic conditions the optimal situation is a buffer which is created by shrubs and trees around the pond.

Resilience of Freshwater Communities of Small Microbial Eukaryotes Undergoing Severe Drought Events.

Small and shallow aquatic ecosystems such as ponds and streams constitute a significant proportion of continental surface waters, especially in temperate zones. In comparison with bigger lakes and rivers, they harbor higher biodiversity but they also exhibit reduced buffering capacity face to environmental shifts, such that climate global change can affect them in a more drastic way. For instance, many temperate areas are predicted to undergo droughts with increasing frequency in the near future, which may lead to the temporal desiccation of streams and ponds. In this work, we monitored temporal dynamics of planktonic communities of microbial eukaryotes (cell size range: 0.2–5 μm) in one brook and one pond that experienced recurrent droughts from 1 to 5 consecutive months during a temporal survey carried out monthly for 2 years based on high-throughput 18S rDNA metabarcoding. During drought-induced desiccation events, protist communities present in the remaining dry sediment, though highly diverse, differed radically from their planktonic counterparts. However, after water refill, the aquatic protist assemblages recovered their original structure within a month. This rapid recovery indicates that these eukaryotic communities are resilient to droughts, most likely via the entrance in dormancy. This property is essential for the long-term survival and functional stability of small freshwater ecosystems.

The effects of entombment on water chemistry and bacterial assemblages in closed cryoconite holes on Antarctic glaciers.

Closed cryoconite holes (CCHs) are small aquatic ecosystems enclosed in glacier surface ice, and they collectively contribute substantial aquatic habitat to inland Antarctica. We examined the morphology, geochemistry and bacterial diversity of 57 CCHs, spread over seven sites, located on five glaciers, covering a range of latitudes, elevations and distance from open seawater. Isotopes confirmed glacial ice as the initial water source, with water chemistry evolving through freeze concentration and photosynthetic processes to have conductivities ranging from <0.005 to >4 mS cm(-1) and pH from <5 to >11. Nitrate concentrations were more elevated in inland, higher altitude sites. Bacterial communities were characterized by Automated Ribosomal Intergenic Spacer Analysis and high-throughput sequencing. The dominant phyla were Cyanobacteria, Bacteroides, Proteobacteria and Actinobacteria. CCH bacterial communities predominantly grouped by geographic location, suggesting initial wind-borne inocula from local and regional sources play a role in structuring assemblages. However, multivariate multiple regression analysis indicated that internal CCH conditions also influenced community structure, particularly the ion content and pH of the liquid water. This highlights the importance of founder bacterial populations, isolation and water chemistry in the evolution of CCH bacterial communities.

Bottom-up thinking—Identifying socio-cultural values of ecosystem services in local blue–green infrastructure planning in Helsinki, Finland

Sustainable urban storm-water management is a key policy of the European Union. Increasing populations, densification and global climate change cause major challenges for the management of urban run-off waters. Small urban aquatic ecosystems (ponds, brooks, wetlands) are important, because they support human health and well-being through water regulation, mitigating urban run-off waters and providing recreational benefits. Ecosystem functions, which arise from interactions between biotic and abiotic processes and which benefit society, are called ecosystem services. The ecosystem service concept can be useful in estimating the impacts of land-use and resource management on ecosystem functions, and to support decision-making. However, many researchers claim that measuring or valuing ecosystem services in land-use planning may fail to recognize intangible or non-monetary values. We studied a local environmental conflict related to a storm-water management plan in Helsinki, Finland. By using integrated value mapping of ecosystem services, we assigned socio-cultural values of local blue-green infrastructure, and evaluated how these values could be taken into account at the early stage in green area planning. Stakeholders (locals, managers and politicians) expressed a total of 47 perceived values related to the urban brook and the public park. We divided these values into four types: (1) use and experience, (2) existence, (3) symbolic, and (4) bequest and moral. We show great differences between the meanings and values of locals, managers and politicians. Managers expressed negative values towards the park, while locals more commonly expressed symbolic values. Exhaustive value mapping could help to identify mutual values and understand disagreements between stakeholders. We introduced a model for a transdisciplinary adaptive planning by using integrated value mapping within ecosystem service concept. Often local protests towards development projects or the management of green areas are seen in a negative light by considering them as NIMBY. Instead of dismissing plurality of meanings and values that emerge from strong place identity, we call for the sustainable management of place-attached values as part of a techno-economic planning strategy of urban ecosystems.

Phytoplankton richness is related to nutrient availability, not to pool size, in a subarctic rock pool system

In small aquatic ecosystems, communities are strongly affected by environmental filtering such as disturbances and fine-scale heterogeneity of physicochemical properties. Aim of this study was to examine the effects of abiotic variables on phytoplankton richness in 30 subarctic rock pools in Finnish Lapland and further to test species–area and productivity–diversity relationships. We used Moran’s correlograms to examine if phytoplankton richness and explanatory variables show spatial autocorrelation. We then related phytoplankton richness to physical, chemical and spatial variables (derived from Principal Coordinates of Neighbor Matrices based on either overland or water course distances) using generalized linear model (GLM). Correlograms did not indicate clear gradient-like spatial structures in the data. According to the best-approximating GLM, phytoplankton richness showed a highly significant positive relationship with total P concentrations, which differed by one magnitude among the pools, and showed also a marginally significant negative relationship with conductivity. Richness scaled nonsignificantly with pool volume. We conclude that rock pools with higher nutrient availability are capable of supporting more phytoplankton species in this low-energy ecosystem. We did not find any support for the species–area relationship across the pools possibly because the pools were similarly affected by random disturbances irrespective of their volume.

Thermal stratification patterns in urban ponds and their relationships with vertical nutrient gradients

Ponds that collect and process stormwater have become a prominent feature of urban landscapes, especially in areas recently converted to residential land use in North America. Given their increasing number and their tight hydrological connection to residential catchments, these small aquatic ecosystems could play an important role in urban biogeochemistry. However, some physicochemical aspects of urban ponds remain poorly studied. Here we assessed the frequency and strength of water column stratification, using measurements of vertical water temperature profiles at high spatial and temporal frequency, in 10 shallow urban stormwater management ponds in southern Ontario, Canada. Many of the ponds were well stratified during much of the summer of 2010 as indicated by relatively high estimates of thermal resistance to mixing (RTRM) indices. Patterns of stratification reflected local weather conditions but also varied among ponds depending on their morphometric characteristics such as maximum water depth and surface area to perimeter ratio. We found greater vertical nutrient gradients and more phosphorus accumulation in bottom waters in ponds with strong and persistent stratification, which likely results from limited particle resuspension and more dissolved phosphorus (P) release from sediments. However, subsequent mixing events in the fall diminished vertical P gradients and possibly accelerated internal loading from the sediment–water interface. Our results demonstrate that stormwater ponds can experience unexpectedly long and strong thermal stratification despite their small size and shallow water depth. Strong thermal stratification and episodic mixing in ponds likely alter the quantity and timing of internal nutrient loading, and hence affect water quality and aquatic communities in downstream receiving waters.

The Ecological Restoration of the Tarquinia Salterns drives the temporal changes in the benthic community structure

1 - Although wetland ecosystems are able to sustain high degree of biological diversity and provide social and economic value, they are also the most impacted and degraded of all ecological systems. 2 - Natural and human-based alterations are particularly evident in small aquatic ecosystems, where the recovery time can be greatly reduced because of the geological and geomorphological characteristics of the sites. 3 - Although seldom used in lentic environment, benthic communities may represent a suitable tool to measure the recovery effects in aquatic ecosystems, due to several characteristics that make them useful as bioindicator. 4 - Here we study the response of benthic communities to the recovery of the Tarquinia Salterns after their abandon and consequent habitat degradation. The increased deposition of organic and inorganic sediments entailed shallow ponds and laminar circulation, causing eutrophication. The ecological restoration of the site allowed reinstating the water depth and flow and returned environmental parameters (mainly dissolved oxygen) to their typical values. 5 - We measured several characteristics of species assemblage in three different sites of the Tarquinia Salterns, covering a period of ten years spanning from pre-recovery to post-recovery phases. 6 - Our results are twofold: i) they show the feasibility of monitoring wetland restoration activities by investigating the pattern of species assemblage in benthic ecological communities and, ii) show the importance of regional and local processes in the composition and response of benthic communities to perturbations.

Development of a dynamic model for estimating the food web transfer of chemicals in small aquatic ecosystems

A dynamic combined fate and food web model was developed to estimate the food web transfer of chemicals in small aquatic ecosystems (i.e. ponds). A novel feature of the modeling approach is that aquatic macrophytes (submerged aquatic vegetation) were included in the fate model and were also a food item in the food web model. The paper aims to investigate whether macrophytes are effective at mitigating chemical exposure and to compare the modeling approach developed here with previous modeling approaches recommended in the European Union (EU) guideline for risk assessment of pesticides. The model was used to estimate bioaccumulation of three hypothetical chemicals of varying hydrophobicity in a pond food web comprising 11 species. Three different macrophyte biomass densities were simulated in the model experiments to determine the influence of macrophytes on fate and bioaccumulation. Macrophytes were shown to have a significant effect on the fate and food web transfer of highly hydrophobic compounds with log KOW>=5. Modeled peak concentrations in biota were highest for the scenarios with the lowest macrophyte biomass density. The distribution and food web transfer of the hypothetical compound with the lowest hydrophobicity (log KOW=3) was not affected by the inclusion of aquatic macrophytes in the pond environment. For the three different hypothetical chemicals and at all macrophyte biomass densities, the maximum predicted concentrations in the top predator in the food web model were at least one order of magnitude lower than the values estimated using methods suggested in EU guidelines. The EU guideline thus provides a highly conservative estimate of risk. In our opinion, and subject to further model evaluation, a realistic assessment of dynamic food web transfer and risk can be obtained using the model presented here.

Emerging global role of small lakes and ponds: little things mean a lot

Emerging global role of small lakes and ponds: little things mean a lot Until recently, small continental waters have been completely ignored in virtually all global processes and cycles. This has resulted from the neglect of these systems and processes by ecologists and the assumption that ecosystems with a small areal extent cannot play a major role in global processes. Recent inventories based on modern geographical and mathematical approaches have shown that continental waters occupy nearly twice as much area as was previously believed. Further, these inventories have shown that small lakes and ponds dominate the areal extent of continental waters, correcting a century- long misconception that large lakes are most important. The global importance of any ecosystem type in a process or cycle is the product of the areal extent and the intensity of the process in those ecosystems. Several analyses have shown the disproportionately great intensity of many processes in small aquatic ecosystems, indicating that they play an unexpectedly major role in global cycles. Assessments of the global carbon cycle underscore the need for aquatic scientists to view their work on a global scale in order to respond to the Earth's most pressing environmental problems.

Modifying living space: an experimental study of the influences of vegetation on aquatic invertebrate community structure

In temporary freshwater systems, the type of vegetation within a system can influence community structure. Vegetation not only provides physical structure, but can also contribute to changes in abundance and quality of food and in water quality through decomposition. An experiment was undertaken using natural and artificial vegetation in small mesocosms to examine the influence of the physical structure of vegetation on invertebrate community structure in terms of water quality, food abundance, and physical structure. It was predicted that invertebrate community structure would be identical in natural and artificial treatments if the effect of vegetative decomposition was negligible. Furthermore, invertebrate community structure in bare ground treatments would be identical to those with vegetation if the physical structure of vegetation has no significant effect. Five treatments were used: a bare ground control, artificial vegetation (×2), and natural vegetation treatments (grass, eucalypt leaf litter). Water quality, food abundance, and invertebrate abundance were examined after six weeks of inundation. All treatments had high water temperatures (34–40°C), and natural vegetation treatments had slightly higher conductivity (208–316 mS cm−1) and lower turbidity (40–231 NTU) than other treatments (47–156 mS cm−1 and 55–400 NTU, respectively). The physical structure of artificial vegetation did not significantly influence invertebrate community structure compared to the bare ground treatment, whereas treatments with decomposing natural vegetation had relatively low abundances of microcrustaceans (0–96 individuals/mesocosm) and relatively high abundances of chironomids (192–1576 individuals/mesocosm) compared to other treatments (>100 microcrustaceans/mesocosm if present, and <370 chironomids/mesocosm, respectively). This suggests that food availability had greater importance than physical structure in determining community structure in these small aquatic ecosystems.