Aquatic Insect Community Structure in Urban Ponds: Effects of Environmental Variables

Aquatic insect community structure in urban ponds: effects of environmental variables

Johan Andersson

Degree project in biology, Master of science (2 years), 2014 Examensarbete i biologi 45 hp till masterexamen, 2014 Biology Education Centre and Department of Ecology and Genetics, Uppsala University Supervisor: Frank Johansson Table of Contents 1. ABSTRACT ...... 2 2. INTRODUCTION ...... 2 3. METHODS ...... 4 3.1 STUDY SITES ...... 4 3.2 INSECT SAMPLING ...... 5 3.3 ENVIRONMENTAL VARIABLES ...... 6 3.4 VEGETATION COVER AND SHORELINE ...... 6 3.5 CHEMICAL ANALYSIS OF WATER SAMPLES ...... 7 3.6 LAND USE AND GIS ANALYSIS ...... 7 3.7 STATISTICAL ANALYSIS ...... 8 4. RESULTS ...... 8 4.1 PRINCIPAL COMPONENTS ON ENVIRONMENTAL VARIABLES ...... 8 4.2 INSECT RECORDS, ABUNDANCE AND DIVERSITY ...... 10 4.3 INSECT ASSEMBLAGES AND POND CHARACTERISTICS ...... 10 4.4 RICHNESS, ABUNDANCE AND DIVERSITY ...... 12 5. DISCUSSION ...... 13 5.1 THE EFFECT OF URBANIZATION ON AQUATIC INSECT COMMUNITY STRUCTURE ...... 13 5.2 ENVIRONMENTAL EFFECTS ON SPECIES RICHNESS, ABUNDANCE AND DIVERSITY ...... 14 5.3 SPECIES DETERMINATION – HIGHER TAXON APPROACH ...... 15 5.4 NEWT PRESENCE ...... 16 5.5. SPECIES OF CONSERVATION CONCERN ...... 16 5.6 FINAL CONCLUSION ...... 16 6. ACKNOWLEDGEMENTS ...... 17 7. REFERENCES ...... 17 8. APPENDICES ...... 21 8.1 APPENDIX 1 – SPECIES LIST, OCCURRENCE AND FREQUENCY ...... 21 8.2 APPENDIX 2 – INSECT ORDER SPECIFIC RDA BIPLOTS ...... 24 8.3 APPENDIX 3 – LAND USE DETAIL SPECIFICATIONS ...... 26 8.4 APPENDIX 4 – POND DESCRIPTIONS ...... 28

1. Abstract

I sampled aquatic insects in 26 ponds of varying types in the urban landscape of the city of Stockholm and related insect community structure to environmental variables. I also related environmental factors to species richness, diversity and abundance of the sampled aquatic insects. A Redundancy Analysis (RDA) showed that the most important variables in explaining insect community structure was the remoteness to developed area and the amount of emergent vegetation in the ponds. Species richness increased with distance from developed area, diversity was related to floating vegetation and abundance of insects increased with distance from developed area and with higher amount of forestation and vegetation. The results of my study shows that urbanization effects divide the insect community into clusters of species that are tolerant or intolerant to effects of urbanisation. One internationally red-listed species, the dragonfly Leucorrhinia pectoralis was found in five (19,2%) of the ponds. My result suggested two important factors that should be considered when planning urban ponds. First, it is important to re-create varying types of ponds and include green buffer areas and second, plant colonisation should be facilitated to better mimic the natural states of ponds.

2. Introduction

The urban landscape is continually expanding along with rising population levels. The proportion of people living in urban areas is forecasted to grow from 50% in 2008, to 69% globally in 2050 (United Nations Population Division 2011). In recent years the field of conservation biology has widened its trajectory from a view of preserving pristine ecosystems to also include areas highly influenced by human activities as important areas for nature and wildlife conservation (London Biodiversity Partnership 2001, Harrison & Davies 2002, Alvey 2006). Such areas could for example be green spaces within cities (Goddard et al. 2010), which is defined as an undeveloped open space at least partly covered with vegetation including community gardens, cemeteries and parks that often contain water (EPA 2013).

Studies indicate that urbanization degrades biodiversity through various processes including e.g. habitat fragmentation (Dickman 1987), land conversion (Moore 1990) and introduction of alien species (Kowarik 2008). The future projections on extinction rates are depressive and the risk of more species becoming red-listed is increasing with urban development (McDonald et al. 2008). However it has also been shown that suburban areas contain a large biodiversity of organisms, often higher than the rural outskirts and the central urban areas. This is due to a broad variety of different habitats (McKinney 2008). For example, the common frog (Rana temporaria) in Great Britain has declined in rural areas, but has increased its abundance in urban areas (Carrier & Beebee 2003).

Factors important for a stable population density of species in the urban landscape differ. For some species landscape barriers hinder migration and 2 dispersal (Blakely et al. 2006), whereas the major concern among other species is the habitat patch quality (Angold et al. 2006). These factors might be especially important in urban areas such as large cities because of the high fragmentation and the low habitat quality. Unfortunately they are not well studied in large cities and warrant more research focusing on the relationship between biodiversity and habitat quality in these areas.

Even though ponds are not green in colour they are an important part of green spaces (Fontanarosa et al. 2013). The proportion of green-space associated with water can be quite large in cities (see refs in Gledhill et al. 2008). Traditionally ponds and smaller waters were filled in cities, but nowadays many ponds are often restored and new ones created (Gledhill & James 2012). These newly created ponds are used for urban drainage, nature conservation, ornament features and more (Sutherland & Hill 1995), and studies have suggested that ponds are important for human quality of life (Lees & Evans 2003).

The biodiversity in ponds is affected by many abiotic and biotic factors. For example, it has been shown that size and connectedness of the ponds affect the species composition, with different species occurring in larger ponds than in a set of smaller ponds. Interestingly, a few smaller ponds can even harbour larger microfaunal diversity than one large pond (Oertli et al. 2002). Many life history traits of aquatic insects rely on interactions with plants. The relationships between species richness of insects and plants are quite well studied and some of the more important aspects of insect-plant interactions are: herbivory, oviposition, predator evasion and foraging (McGaha 1952). Numerous aquatic insects are susceptible to fish predation and presence of fish has been shown to play a key role in structuring aquatic insect communities (Bendell & McNicol 1987). Additionally the local water chemistry is affecting aquatic insect composition, where e.g. pH is a critical factor during the development of the larval stages with many species having problems coping with a too acidic environment (Bell 1971).

Biodiversity in city ponds is also affected by land use/land-cover and perhaps even more so than in rural areas because land-cover changes are extreme in cities. While we have some knowledge on how land-cover affects biodiversity for terrestrial systems in cities, we know very little on how city ponds are affected. For terrestrial systems Loss et al. (2009) showed that bird species richness was higher in urban cities with undeveloped patches and heterogeneous land-cover types. Interestingly, Tratalos et al. (2007) found that species richness of birds in British cities showed a humped shaped relationship with housing density, suggesting that land-cover variables do not necessarily have to show linear relationships with biodiversity variables. With regards to ponds in cities, less information is available and I am only aware of one study that focused on pond biodiversity and environmental land-cover variables. In that study, Goertzen & Suhling (2013) found that sealed area (buildings and roads) was negatively associated with pond biodiversity.

Since many of the urban ponds are relatively new the ecological value of these ponds are still unknown and research identifying important factors affecting the

3 biodiversity of these ponds are still lacking (Williams et al. 2008). There is certainly a need to pinpoint the definitive associations between biodiversity and environmental variables as well as structural landscape features. Such knowledge is important for city planners and the purpose of my study is to provide this knowledge.

I conducted my study in the conurbation of the Stockholm capital province. This is Sweden’s most heavily urbanized area consisting of an archipelago structure with a mosaic of islands and suburbs spreading in north-south direction from the city centre. The Swedish landscape has a long history of ditching and draining and the Stockholm area is no exception (Jakobsson 2013). Thus the landscape has been transformed and reduced of important wetland habitats. The present- day restorations of wetlands in Sweden are mainly conducted for financial benefits and reduction of agricultural nitrogen pollution (Byström 1998). It has also been recognized as a cost effective way to reduce nitrogen emissions in urban settings, including Stockholm, where wetlands function as a sink of reactive nitrogen reducing the loading and eutrophication of surrounding waters (Gren 1994). Both constructed and natural ponds and wetlands often contain a high biodiversity, today considered to provide important ecosystem services and amenity values in urban green spaces (Bolund & Hunhammar 1999). The importance of ponds for urban invertebrates has been emphasized along with the importance of the naturalness of green spaces (Moore 1990).

In this study I ask which environmental factors affect the biodiversity of aquatic insect species in urban city ponds. I will also give suggestions on what can be done in urban conservation planning to create a high biodiversity in these ponds.

3. Methods

3.1 Study sites The investigated ponds were located in the north central parts of Stockholm (59°19'N, 18°4'E). This is one of Sweden’s most highly urbanized areas and the ponds included in my studied were situated in the municipalities Järfälla, Sollentuna, Solna, Stockholm and Sundbyberg (SCB 2010).

Ponds that were included were in the size range of 2 m2 to 2 ha, using the definition of pond by Ponds Conservation (2002) and earlier used by Gledhill et al. (2008). To locate ponds, I contacted ecologist and official water administrators employed at the municipalities. In addition, I searched for ponds on digital overview maps. Twenty-six ponds were included which resulted in both natural and constructed, permanent and temporary, both old (>100 years) and new (one year) ponds (Fig. 1). Some of them were constructed as city park ponds for recreational values whereas others had been built as stormwater ponds to collect surface runoff and prolong turnover from surrounding water bodies and decrease high nutrient and waste/pollutant loading. No golf course

4 ponds were included among the selected ponds. The invertebrate fauna of golf course ponds in the area has previously been studied by Colding et al. (2009).

Fig. 1. Pond locations in the Stockholm area. Grey areas represent in falling intensity; developed land, forest, other open area. Water area is represented by white. Black striped lines depict municipality borders and ponds locations are symbolised by white circles with black outline. See Appendix 4 for numbering and pond characteristics. Terrängkartan™ © Lantmäteriet 2010: Permission I 2010/0058.

3.2 Insect sampling Aquatic insects were sampled between May 15th and June 7th 2013. I restricted my sampling to four insect orders that are easily distinguishable from each other on site: Coleoptera, Hemiptera, Odonata and Trichoptera. Sampling of these orders covered species with different roles in the food web, both herbivores and predators from various functional groups. This approach has the advantage of simplifying species determination and is conventionally used in comparative studies (see Simberloff & Dayan 1991). I sampled the aquatic life stages of the selected insects orders which are inhabiting the pond and thus are exposed to the local environmental factors for an extended period of time in contrast to visiting insects i.e. larvae in Odonata and Trichoptera and larvae and adults in Coleoptera and Hemiptera. All ponds were only sampled on the day of the visits. For collecting insects I used a bottom scoop net with a diameter of 20 cm and a 5 mesh size of 1,5 mm. Six samples were taken in each pond at a depth of 2-3 dm. The net was swept along the bottom in opposite directions (left to right) eight times on a 1 m stretch, which constituted one sample. By using six samples I managed to cover all types of representative microhabitats along the shoreline: e.g. soft bottom, hard bottom with and without vegetation. The sampling strategy was derived from the guidelines by the SEPA (2006). All insects were determined to order at the pond site and insects from the four orders included in the study were preserved in 70% ethanol, stored in labelled plastic tubes and brought back to the laboratory for species determination. All other species were released back to their respective ponds.

Species determination of Coleoptera was carried out by Johannes Bergsten (Swedish Museum of Natural History). Trichoptera was species determined by Ulf Bjelke (Swedish Species Information Centre) and I determined Hemiptera and Odonata. Specimens that could not be determined to species level were still included in the final analysis and set to family or genus-level and hence regarded as separate taxa. In most cases these specimens were early instar larvae. Larvae of Coenagrion pulchella and C. pulchellum are not distinguishable and were therefore regarded as same species in my analysis. The same applies to three cases among the Trichoptera were larvae could not be distinguished between two species. These were i) Limnephilus affinis and L. incisus, ii) Limnephilus luridus and L. ignavus and iii) Oligotricha stricta and O. lapponica. These three species were recorded in only one pond each.

3.3 Environmental variables Most environmental variables were collected on the same date that I sampled the insects. Geographic coordinates in RT90 2,5 GON V were collected for each pond with a Garmin Dakota 20 handheld GPS with an accuracy of 5 meters and loaded with Friluftskartan™ Pro v3. After the insect sampling I measured maximum depth of each pond with a carpenter’s rule by wading out in the deepest part of the pond. A water sample for chemical analysis was collected with a 250ml plastic bottle from the middle of the pond, approximately 30 cm beneath the water surface. pH was estimated on site with a portable EcoSense® pH10 pH/temperature pen submerged in the water sampled for chemical analysis. During the visits and sampling at each pond I also noted presence of fish, Great Crested Newt (Triturus cristatus) and Common Newt (Lissotriton vulgaris) in the pond by means of visual observations and catches during the insect sampling. For an overview of the recorded environmental variables refer to table 1.

3.4 Vegetation cover and shoreline Between August 28th and August 30th 2013 I revisited the ponds in order to estimate vegetation characteristics. Vegetation cover of the ponds was estimated visually in measures of tenths, ranging from no vegetation at all (0/10) to full cover (10/10). In addition, vegetation cover was recorded into three separate categories; floating leaved vegetation, submerged vegetation and emergent vegetation. I also estimated the percentage of barren shoreline (hard surface without vegetation e.g. stones, gravel) and bush vegetated shoreline (vegetation of a height of 1 meter or above within 2 meters of the shoreline). This was done 6 by walking around the ponds measuring total steps and steps with any of the two shoreline types.

3.5 Chemical analysis of water samples The water samples collected were analysed for total phosphorus, total nitrogen and total organic carbon.

Total phosphorus was analysed using the method described by Menzel & Corwin (1965). In brief, organically bound phosphorus was transferred to orthophosphate through oxidative hydrolysis with potassium persulfate and thereafter hydrolysis was performed in a vaguely acidic environment at high pressure and temperature using an autoclave. Afterwards the dissolved phosphate was measured using the Molybdate Reactive Phosphorus method where a spectrophotometer was used to measure the amount of phosphomolybdenum complex to which the amount of phosphorus is proportional.

Total nitrogen was measured using the method described by Rand et al. (1976) in which all nitrogen in the sample was transformed to nitrate in the presence of a strong oxidizing agent. The nitrate was then analysed using a spectrophotometer.

Total organic carbon was analysed using a Shimadzu TOC-L carbon analyser in which the sample is first freed from inorganic carbon, and oxidized under high temperature after which the resulting CO2 is measured with a non-dispersive IR gas analyser (Shimadzu brochure, Sugimura & Suzuki 1988).

3.6 Land use and GIS analysis Terrain and land use around the ponds was estimated with the software ArcGIS 9 and the Terrängkartan™ map from Lantmäteriet. Land use was estimated in a 200-meter radius buffer zone along the shoreline of the ponds and excluded the pond area from the water surface land use category. Smaller ponds were not marked on the map and therefore I determined the centre of the pond (estimated from GPS coordinates) and drew a 200-meter radius circular buffer zone around the centre. The difference in total area between these two approaches differed by less than 5%, and therefore I concluded these measures to be comparable for estimating land use.

The following land use categories were estimated within the buffer zones: coniferous and mixed forest, other open land, low-rise buildings, high-rise buildings, water surface, arable land, leisure homes, industrial land and precincts. In addition I estimated the distance from the ponds to nearest developed area, and for each pond the distance to nearest inventoried pond. See appendix 3 for definitions of each land use category.

3.7 Statistical analysis I explored and explained insect community structure and environmental variables using a multivariate ordination analysis. Since some of the environmental variables are likely to be correlated I used a Principal Component Analysis (PCA) to reduce the 26 recorded environmental variables to uncorrelated principal components (PCs). For explanation of the PC axes I considered the environmental variables with a factor loading of at least ±0,7 to be highly explanatory and included variables with a loading of at least ±0,5 for interpretation (Goertzen & Suhling 2013). These PCs were interpreted as meaningful ecological variables depending on their loading on each respective environmental variable. The PCs are listed depending on their explanatory value with PC1 axis projecting most of the variance, PC2 explaining the second most variance uncorrelated with the previous axis etc.

The relationship between insect community composition and environmental variables (the principal components) was explored by a constrained gradient analysis, redundancy analysis (RDA) using the statistical software R (R Core Team 2013). The insect abundance i.e. the total number of specimens per species and pond were used as variables.

In order to assess the insect diversity of the ponds I used the following metrics; i) species richness, ii) Shannon-Wiener diversity index and iii) insect abundance (total number of specimens found). I correlated these measures with the PCs using a backwards stepwise multiple regression to evaluate whether or not they were influenced by the PCs.

4. Results

4.1 Principal components on environmental variables Nine PCs had eigenvalues ≥ 1, and together they explained 82,8% of the total variance (table 1). PC1 explained 19,4% of the variance and had a high loading on pond circumference, pond area and distance to closest pond as well as high pH but had high negative loading on nitrogen, phosphorous and carbon. PC1 is therefore associated with pond size and primary production. PC2 had high loadings on surrounding forest, submerged vegetation, bushy shoreline and newt presence and a negative loading on open area suggesting that PC2 is interpretable as woodland and vegetation. The high loading on distance to built area for PC3 imply that it represents remoteness from urban areas. It also has a high loading for emergent vegetation. PC4 had a high loading on adjacent waters (water surface) and is therefore associated with nearby water (excluding the ponds themselves). It also got a negative loading on adjacent low-rise buildings, roughly proposing a contrasting obstructive effect to water surfaces as semi- suitable habitat corridors maybe facilitating connection between ponds. Interpretation of the remaining 5 PCs are less straightforward since none of them have positive or negative factor loadings equal to or above 0,7 and in addition they explain less than 7 % of the variance each. PC5s highest factor

loading was floating leaved vegetation and represent the different species of vegetation with leaves on the water surface. PC6s highest loadings were on arable land and emergent vegetation. PC7 and PC8 had no variables that loaded more than 0,5. The relatively high loading of industry land on PC9 should be interpreted with care because there was a low absolute abundance of industry area in the dataset.

Table 1. Results of PCA on environmental variables at ponds.

Environmental Variables Factor Loadings and Interpretation PC1 PC2 PC3 PC4 PC5 PC6 PC7 PC8 PC9 Size & Forestat- Remo- Other Floating Field Industry primary ion and teness water vegetation vegetati- product- vegetati- areas on ion on Pond Circumference 0,797 -0,084 -0,369 -0,072 0,165 -0,029 0,174 0,166 -0,006 Pond Area 0,779 0,105 -0,290 0,052 0,114 -0,048 0,031 0,321 0,171 pH 0,744 0,038 0,378 0,358 -0,094 0,153 -0,077 -0,105 -0,032 Total Nitrogen -0,713 -0,376 -0,194 0,001 -0,339 -0,039 0,220 0,116 0,032 Forest -0,082 0,791 0,036 0,348 0,021 -0,099 0,355 0,018 0,005 Other open land 0,368 -0,721 0,426 0,017 0,129 -0,156 0,232 0,052 -0,097 Distance to Built Area 0,222 -0,158 0,736 0,116 -0,169 -0,167 0,379 0,134 0,016 Floating Vegetation -0,677 0,044 -0,042 0,125 0,539 0,148 0,069 -0,093 -0,200 Distance to Closest Pond 0,647 0,045 -0,337 -0,240 0,222 -0,283 0,211 0,144 -0,118 Total Organic Carbon -0,632 0,016 -0,427 0,044 -0,358 -0,201 0,278 0,279 0,003 Total Phosphorous -0,533 -0,287 0,223 0,039 0,007 0,025 0,391 0,080 0,407 Common Newt presence -0,065 0,696 0,447 0,088 0,095 -0,138 -0,174 0,148 -0,131 Submerged Vegetation 0,134 0,671 0,192 -0,088 0,152 -0,091 0,089 -0,235 0,313 Bushy Shoreline -0,151 0,556 -0,397 0,441 -0,033 -0,029 0,326 0,091 0,145 Low-rise buildings -0,135 0,537 -0,387 -0,583 -0,246 0,072 -0,215 -0,070 -0,094 Crested Newt presence -0,049 0,524 0,414 -0,456 0,074 -0,102 0,046 -0,135 0,326 Emergent Vegetation 0,275 -0,003 0,506 -0,083 -0,290 0,532 -0,021 0,465 -0,031 Water surface 0,073 0,143 0,200 0,571 -0,151 -0,490 -0,347 -0,123 0,030 Arable land 0,184 -0,037 -0,051 0,122 -0,368 0,610 0,183 -0,403 -0,039 Industry -0,002 -0,407 -0,197 -0,040 0,461 0,169 -0,176 0,168 0,561 Depth 0,279 0,272 -0,338 0,040 0,293 0,183 0,397 0,040 -0,342 Fish Presence 0,440 -0,126 -0,407 0,276 -0,075 0,209 0,119 -0,481 0,248 Total vegetation -0,399 0,396 0,414 0,017 0,405 0,468 0,100 0,109 -0,051 Barren Shoreline -0,197 -0,447 0,264 -0,214 0,296 -0,254 0,274 -0,429 -0,188 High-rise buildings -0,386 -0,248 -0,206 0,489 0,312 0,131 -0,344 0,136 -0,074

Eigenvalue Magnitude 4,856 3,919 3,089 1,818 1,672 1,578 1,442 1,267 1,051 Variance Proportion 0,194 0,157 0,124 0,073 0,067 0,063 0,058 0,051 0,042 Bold: High factor loading ≥ 0,7; bold and italic: moderate factor loading ≥ 0,5.

4.2 Insect records, abundance and diversity I recorded 65 autochthonous species; 18 species of Trichoptera with 3 groups of small larvae only determined to genus, 7 species of Odonata with 4 groups of small larvae only determined to genus, 12 species of Hemiptera with 4 groups of small larvae only determined to family level and 28 species of Coleoptera with 7 groups of small larvae determined to genus level. 29 of the total species only occurred in one pond (see table in Appendix 1). Species richness for the ponds varied between 1 and 20 species. The mean number of species per pond was 9,64 ± 6,11. The most commonly occurring species within respective order were: Trichoptera; Limnephilus flavicornis (11 ponds), Odonata; Coenagrion puella/pulchellum (11 ponds), Hemiptera; Notonecta glauca (5 ponds), Coleoptera; Haliplus ruficollis (12 ponds) and Hygrotus inaequalis (8 ponds).

4.3 Insect assemblages and pond characteristics The 9 RDA axes explained 43,7% of the total variance. The RDA found that species composition was significantly affected by PC3 (Remoteness) (p = 0,001) and PC6 (Field vegetation) (p = 0,035) and almost significant on PC2 (Forestation and vegetation) (p = 0,058) and PC4 (Other water areas) (p = 0,052). Hence the aquatic insect community was associated with remoteness to buildings, emergent vegetation (PC3), degree of surrounding arable land (PC6) and to some extent degree of surrounding forest and pond vegetation (PC2), as well as degree of low buildings and nearby water surface (Fig 2 & Fig 3).

A closer look at the RDA 1 and 2 showed that the response to any of the environmental variables is not uniform among any of the insect orders, but separate taxa respond differently. A few dragonfly species such as the Coenagrion genus, Libellula quadrimaculata, Leucorrhinia pectoralis and Aeshna grandis seem to correspond well to PC1 and PC2 indicating the importance of pond size, nutrient levels, pond connectedness, vegetation and forest surroundings. Lestes sponsa and undefined Aeshna and Lestes species seem to be affected by PC4, surrounding water surface and low-rise buildings (Appendix 2, Fig. A3).

Most Coleoptera species are clustered in the centre of the biplot indicating no or very weak responses to our tested environmental variables but some are scattered, responding to certain PCs. Haliplus ruficollis is associated with PC4, Rhantus sp. with PC3, Hygrotus inaequalis with PC1 and PC2, Hyphydrus ovatus with PC8 and Haliplus immaculatus with PC7 (Appendix 2, Fig. A1).

Among the Hemiptera there were only a few examples of insects showing responses to the environmental variables, those included; Notonecta glauca which was weakly associated with PC2, and Ilyocaris cimicoides which was weakly associated with PC4 (Appendix 2, Fig. A2).

Many of the Trichoptera did not seem to associate with any of the PCs. Limnephilus centralis might have a weak association to PC1, pond size and nutrient status (Appendix 2, Fig. A4).

Fig. 2. RDA ordination biplot of insect species and PCs, zoomed in to increase resolution. See appendix 2 for biplots for specific insect orders. Insect species are abbreviated with first letter of genus and first three letters of species name. Groups are abbreviated with first three letters of genus followed by sp. For interpretation of PCs, see table 1.

Fig. 3. RDA ordination biplot of insect species and PCs. See appendix 2 for biplots for specific insect orders. Insect species are abbreviated with first letter of genus and first three letters of species name. Groups are abbreviated with first three letters of genus followed by sp. For interpretation of PCs, see table 1.

4.4 Richness, abundance and diversity Species richness was affected by PC3, PC7 and PC8. Hence more species rich ponds were further away from developed areas (Fig. 4) and had more emergent vegetation (Fig. 5) as well as a low influence from PC7 and PC8, which is variation not explained by our tested environment variables. Abundance was affected by PC2 and PC3 and thus vegetation surrounding, bordering and in the pond positively affected the total abundance of insects. Presence of both species of newts is also positively affecting the total number of insects. There was a significant increase in both abundance of insects (t(25)abun= 3,25 p= 0,003) and species richness (t(25)sr= 2,22 p= 0,035) between ponds with no newts (Mabun= 28,9 SD= ±35,4; Msr= 7,3 SD= ±5,6) and ponds with one or both species of newts (Mabun= 116,2 SD= ±98,2; Msr= 12,4 SD= ±5,8). Adjacent low-rise buildings are also included into PC2 and have a small positive effect on insect abundance but increasing distance to built area is also positively correlated with abundance and the two may seemingly stand in contradiction to each other. Diversity was affected by PC5 which is correlated to the amount of floating vegetation in the ponds including water lilies and duckweed (Table 2).

Table 2. Results of backward stepwise multiple regression. Dimension Variables Unstandardized Coefficients Standardized Coefficients p-value Adjusted R2 Beta Standard Error Beta t

Richness Constant 9,269 0,683 0,000 13,570 0,000 0,674 PC1 0,547 0,310 0,202 1,765 0,093

PC2 0,664 0,345 0,220 1,925 0,069

PC3 2,055 0,389 0,604 5,287 0,000***

PC7 1,472 0,569 0,296 2,588 0,018*

PC8 2,359 0,607 0,444 3,889 0,001***

Abundance Constant 62,500 11,978 0,000 5,218 0,000 0,388 PC1 8,897 5,436 0,256 1,637 0,117 PC2 13,003 6,050 0,336 2,149 0,043* PC3 21,849 6,815 0,501 3,206 0,004** PC7 -15,110 9,975 -0,237 -1,515 0,145

Shannon Index Constant 1,466 0,107 0,000 13,709 0,000 0,385 PC2 0,094 0,054 0,272 1,733 0,099 PC3 0,095 0,061 0,244 1,557 0,136 PC4 0,121 0,079 0,240 1,529 0,143 PC5 0,207 0,083 0,392 2,500 0,022* PC6 0,167 0,085 0,307 1,959 0,065 PC7 0,173 0,089 0,305 1,941 0,067

25 R² = 0,31132 20

5 Species Richness (n)

0 0,0 50,0 100,0 150,0 200,0 250,0 300,0 350,0 400,0 Distance to developed area (m)

Fig. 4. Species richness plotted against distance to developed area. Species richness of aquatic insects increases with distance from ponds to developed areas.

25 R² = 0,37385 20

5 Species Richness (n) 0 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 Emergent vegetation (frac)

Fig. 5. Species richness plotted against emergent pond vegetation. Species richness of aquatic insects increases with the relative amount of emergent vegetation.

5. Discussion

5.1 The effect of urbanization on aquatic insect community structure Distance from ponds to buildings and the amount of emergent vegetation where the two environmental variables that explained the majority of the variation in insect community structure in urban ponds. It emphasizes the importance of naturalness of the pond for many insect species and shows that urbanization can divide the insect community by supporting urban tolerant species and pushing away other species. This may imply that the urban landscape is negatively affecting the naturalness of the ponds and may actually reduce the pond quality. Hence, the further away from developed area, the more suitable habitat are available for many aquatic insects. Booth & Jackson (1997) showed that urbanization degrades aquatic systems and that areas with just 10% of impervious soils (hard impermeable surface layers more common in urban

13 areas) can have irreversible effects for the downstream aquatic ecosystem functions. However, the majority of the ponds in my study had a quite rich insect fauna despite being urban ponds. Biggs et al. (2001) found that most aquatic habitats are inhabited by insects regardless of naturalness, but also suggested that large alterations can have negative effects. For example, changing temporary ponds into permanent ponds will most likely degrade the local insect fauna (Biggs et al. 2001). Interestingly, constructed urban ponds could have a similar fauna to natural urban ponds. Such a pattern was found when comparing constructed ponds for wastewater treatment and natural ponds (Becerra Jurado et al. 2009). They found that the different type of ponds housed approximately the same number of species and had a lot of species in common but could have distinctively different community structure, depending on factors such as pH, depth and pollutant loading (Becerra Jurado et al. 2009).

The nearly significant negative association between insect communities and low- rise buildings and a positive association to other water surfaces (excluding the ponds) suggest that nearby water areas (within a 200 meter radius of the ponds) can play an important role since more than half of total developed area within some of these buffer zones belonged to the low-rise building category which in turn is associated with impervious soil. Even though distance from the sampled ponds to the closest sampled pond was not found important in my analysis, other studies have found connectivity between ponds to be an important determinant of insect community structure (Becerra Jurado et al. 2009). The nearly significant association between insect community structure and water surface suggest that these waters may serve an analogous function to vegetation corridors between rural and urban terrestrial habitats, which can maintain or enhance the urban biodiversity (Flink & Searns 1993). I found that some taxa such as Aeshna and Lestes were associated with nearby water surface, which implies that dispersal events rather than pond suitability might be a good predictor for parts of the insect community structure. This result might have implications for planning of waterways in urban areas because it is important to determine what factors limit the migration and dispersal of aquatic insects, since potential barriers such as culverts and roads can be key structures for recolonization of restored habitats, including ponds, that are often connected through small creeks (Blakely et al. 2006). Just restoring the physical habitats may be ineffective if the ponds are unreachable for the insects.

5.2 Environmental effects on species richness, abundance and diversity Species richness was found to increase with distance from developed area and with amount of emergent vegetation, and this was true for the abundance of insects as well, yet again stating the importance of naturalness. Other studies from both terrestrial and aquatic habitats have found that natural areas deprived of human disturbance have a higher species richness of insects (Wang et al. 1997, Martikainen et al. 2000). Interesting to note is that the three ponds close to built area that still had a relatively high species richness (Fig. 4) had some forest surrounding them and more than half of the pond’s surfaces were covered with vegetation. I did not find any evidence that species richness increased with pond size. It is commonly believed that a larger area usually contain more habitats and

14 thus a higher biodiversity, but other pond studies show that smaller ponds usually contain a large biodiversity due to having more submerged vegetation and a higher likelihood of being devoid of fish communities, making them more suitable for small invertebrates (Scheffer et al. 2006). This could be a factor reducing the differences in insect diversity between ponds of different sizes in my study. Another explanation for the absence of such a pattern could be that the range of ponds was rather small or that larger ponds are more managed than smaller ponds, something that would be interesting to look further into. More importantly Oertli et al. (2002) showed that a set of smaller sized ponds could together harbour a larger insect diversity than single large ponds stressing the importance of connectivity among ponds in urban areas. PC7 and PC8 did also affect species richness, but together they described less than 10% of the total variation. However, the PCA analysis did not reveal any significant interactions with my collected environmental data for these PCs, making further interpretation difficult.

One of the most obvious patterns in this study is that the amount of vegetation both in and surrounding the ponds greatly determines the abundance of aquatic insects in them. Similar conclusions have been found in man-made limnic systems where the biomass of submerged vegetation positively affected the abundance of benthic fauna (Machena & Kautsky 1988). Earlier studies have also shown that plant richness positively affects both abundance and diversity of insects in terrestrial habitat (Knops et al. 1999, Haddad et al. 2001). This pattern has been shown to be especially evident in herbivore and predator species plausibly due to particular interactions between certain plant and insect species (Haddad et al. 2001). A common misconception in pond management according to Biggs et al. (1994), is that dredging and removal of aquatic and surrounding vegetation to create more open water is beneficial for biodiversity. My findings indicate that different kinds of vegetation is beneficial for aquatic insect communities and the fact that species differed in their association to the environmental variables more likely suggest that not a single pond stereotype will house the greatest biodiversity of benthic fauna. Instead different insect species utilize distinctive pond habitats. For example, many species only occurred in one single pond and the ponds themselves were of distinctly varying types.

Diversity was also significantly correlated with floating leaved vegetation. Biggs et al. (1994) also emphasize the importance of floating vegetation for benthic communities where many insects rely on floating vegetation for egg laying, herbivory and algae grazing as well as building material for Trichoptera larvae.

5.3 Species determination – higher taxon approach In some cases specimens could not be determined to species level. Had these been excluded from the analysis some ponds would have no species richness, obviously giving a false picture. Counting these specimens in a higher taxonomic group such as genus and family did for example in one pond account for at least five species making this a more suitable approach. Studies have shown that higher taxon surrogates perform well in communities where a few common

15 species are most abundant, and worse in communities with many equally abundant species (Neeson et al. 2013). Since my ponds were of different types with varying communities, the approach I used, (including them as higher taxonomic groups rather than excluding them) may have been more suitable for some ponds than others. However, the importance of keeping a uniform methodology kept me using this approach in the analysis since the information added was judged more valuable than the information lost if they had been excluded.

5.4 Newt presence Presence of newts indicated a higher abundance and species richness than ponds without newts. This is interesting since evidence shows that some insect species are less likely to choose habitats with breeding amphibians. For example the small dragonfly Sympetrum danae is reluctant to oviposit where frogs are present due to the high risk of being preyed upon while ovipositing (Michiels & Dhondt 1990). The interactions between insects and amphibians are not one sided. The insect orders included in my study, are included in the diet of the newts even if they are not the main prey (Fasola & Canova 1992). On the other hand large aquatic insects feed on amphibian eggs and larvae while some species compete with newt larvae for periphyton (Formanowicz Jr 1986, Morin 1989). I therefore conclude newt presence is an indication of suitable habitat for a large variety of insect species and that predation and competition by newts seem to be of minor importance for a rich insect community in urban ponds.

5.5. Species of conservation concern I only found one red-listed insect species in my survey, but it should be noted that I only focused on four orders of insects and some other red-listed species might therefore occur in the ponds. The large white-faced darter dragonfly (Leucorrhinia pectoralis) is internationally red-listed and classified as “near threathened” in appendix 2 of the Bern Convention, and was found in five ponds in the studied area. It has previously been found in golf course ponds in the Stockholm area (Colding et al. 2009). My study shows that it is quite common in other types of ponds as well in the urban area of Stockholm. It was found in both natural and constructed stormwater ponds, but only in ponds with dense vegetation.

5.6 Final conclusion My results have some implications for biodiversity in urban ponds and what can be done in urban planning, and I suggest the following; 1) The highest association for the insect community with any environmental factors was the remoteness from developed area and a high abundance of emergent vegetation. This suggests that a natural state of ponds is beneficial for a part of the insect community. Hence, large green areas around ponds and ponds with a high density of vegetation and located as far as possible from developed area would be important for many aquatic insects that otherwise get excluded by urbanization processes. I also suggest that connection to other water bodies is important for a diverse insect community. 2) Species richness and abundance of 16 insects also correlate well with remoteness from developed areas and emergent vegetation while diversity is linked to floating leaved vegetation. Therefore I suggest that urban ponds should have some vegetation in and close to the ponds.

When creating and restoring ponds in urban areas it is important to either construct the area with the vegetation in and around the ponds in mind by either manually planting or facilitate natural plant colonisation. Finally I suggest that since there is no single pond type that had all or a majority of the species present, different types of ponds near each other would be preferable. But with limited efforts the emphasis should be on creating or restoring ponds further away from buildings and developed areas and with a lot of vegetation to match the natural ponds derived from the historical landscape.

6. Acknowledgements

I would like to thank my supervisor Frank Johansson for all the support and help during the length of the entire project as well as contributing with many great ideas on the execution of the study. I thank Jan Johansson for help and support with the chemical analyses of the water samples and Örjan Östman for his aid with the statistical analyses. I thank Johannes Bergsten and Ulf Bjelke for their work with species determination, saving me valuable time during the project. Last, I would also like to thank all the administrators on the respective municipalities for all their help on locating the ponds.

7. References

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8. Appendices

8.1 Appendix 1 – Species list, occurrence and frequency

Larval insect species records in urban ponds in northern municipalities of Stockholm, Sweden.

Species Name Abundance (n) Number of ponds Frequency at ponds (%) Trichoptera

Agrypnia varia 2 2 1,1 Athripsodes cinereus 2 1 4,1 Glyphotaelius pellucidus 1 1 2,6 Holocentropus dubius 5 3 1,3 Limnephilus affinis/incisus 2 1 3,5 Limnephilus binotatus 12 2 26,3 Limnephilus centralis 20 1 34,5 Limnephilus decipiens 2 2 1,1 Limnephilus flavicornis 69 11 13,7 Limnephilus fuscinervis 1 1 1,7 Limnephilus luridus/ignavus 1 1 2,0 Limnephilus nigriceps 5 1 8,8 Limnephilus politus 2 1 3,5 Limnephilus rhombicus 1 1 20,0 Mystacides azurea 8 2 24,3 Oligotricha stricta/lapponica 1 1 2,6 Trichostegia minor 2 2 2,7 Trieanodes bicolor 139 3 21,2 Leptoceridae sp. 1 1 14,3 Limnephilidae sp. 8 4 4,1 Pyralidae sp. 3 2 17,3 Odonata

Aeshna grandis 11 5 2,8 Coenagrion hastulatum 16 3 6,0 Coenagrion puella/pulchellum 127 11 15,2 Lestes sponsa 94 3 19,3 Leucorrhinia pectoralis 32 5 7,2 Libellula quadrimaculata 11 2 3,4 Somatochlora metallica 3 1 5,3 Aeshna sp. 15 5 6,5 Coenagrion sp. 14 4 10,7 Lestes sp. 430 7 34,1 Libellulidae sp. 4 1 1,5 Hemiptera

Callicorixa praeusta 1 1 1,7 Callicorixa wollastoni 1 1 1,7 21

Corixa panzeri 4 2 1,7 Cymatia bonsdorffii 4 2 4,3 Cymatia coleoptrata 4 2 4,7 Hesperocorixa castanea 2 2 1,2 Hesperocorixa linnaeii 1 1 1,8 Hesperocorixa sahlbergi 2 2 13,8 Ilyocoris cimicoides 3 1 3,2 Nepa cinerea 1 1 0,4 Notonecta glauca 10 5 5,4 Sigara semistriata 1 1 2,9 Corixidae sp. 99 10 10,6 Hesperocorixa sp. 1 1 20,0 Notonectidae sp. 86 8 13,1 Sigara sp. 1 1 1,8 Coleoptera

Acilius canaliculatus 18 6 28,1 Anacaena lutescens 1 1 5,6 Graptodytes pictus 1 1 0,4 Haliplus immaculatus 18 2 13,8 Haliplus confinis 1 1 0,8 Haliplus fulvus 2 1 33,3 Haliplus heydeni 34 6 24,8 Haliplus ruficollis 49 12 14,8 Helophorus strigifrons 1 1 7,1 Hydaticus seminiger 1 1 1,1 Hydrobius fuscipes 6 2 2,9 Hydrochara caraboides 3 3 7,2 Hydroporus dorsalis 5 1 14,3 Hydroporus erythrocephalus 6 1 17,1 Hydroporus figuratus 8 5 5,5 Hydroporus incognitus 10 5 31,8 Hydroporus palustris 6 5 7,2 Hydroporus planus 1 1 1,2 Hydroporus striola 2 2 12,2 Hygrotus inaequalis 51 8 13,2 Hyphydrus ovatus 23 7 5,3 Laccobius minutus 3 2 2,1 Laccophilus minutus 1 1 0,4 Noterus clavicornis 2 1 3,5 Noterus crassicornis 6 3 2,2 Porhydrus lineatus 12 5 6,4 Rhantus exsoletus 1 1 1,2 Rhantus frontalis 4 2 2,4 Agabus sp. 10 5 6,4 Colymbetes sp. 1 1 0,4 Dytiscus sp. 10 6 3,4 22

Graphoderus sp. 5 1 8,6 Hydaticus sp. 1 1 1,2 Hydroporus sp. 7 1 5,1 Rhantus sp. 50 7 5,3 Species Total (sum) 65 (18*) * Taxonomic groups only defined to family or genus level.

8.2 Appendix 2 – Insect order specific RDA biplots

Insect order specific biplots from our RDA analysis with other insects removed for increased visibility.

Fig. A1. RDA ordination biplot including all Coleoptera species and the PCs.

Fig. A2. RDA ordination biplot including all Hemiptera species and the PCs.

Fig. A3. RDA ordination biplot including all Odonata species and the PCs.

Fig. A4. RDA ordination biplot including all Trichoptera species and the PCs.

8.3 Appendix 3 – Land use detail specifications

High-rise buildings Surface for high-rise buildings with block of apartments with at least three stories or more. Lower buildings can occur. All related land such as roads, parking spaces and office buildings are included.

Low-rise buildings Area for dense low-rise buildings, constituting systematic block structures with detached one or two family houses, terrace-houses, linked houses, or tenement buildings with at most two stories. Occasional higher buildings can be included. All related land such as roads, parking spaces and office buildings are included.

Leisure homes Area for development with buildings mainly intended for recreational use (secondary residences, cabin villages) with related buildings for business and service purposes and allotment area with habitable dwellings (i.e. at least 20m2).

Precincts Area for closed coherent district buildings with several stories. Lower buildings can be included. The development can in some places be open to permit transports to and from the inner parts of the district. Three sides of the district should be more or less closed. All related land such as roads, parking spaces and office buildings are included.

Coniferous and mixed forest Area of coniferous or mixed coniferous and deciduous forest including arboreous park land where also fellings (clear-cut areas) are included. All types of trees and bushes can be included.

Industrial area Area on which mainly industrial activities are practised. Included are e.g. mining areas, port structures, fishing harbours and ferry quays. All related land such as roads, parking spaces, storage spaces and office buildings are included.

Other open land Area for other open land where the height of the vegetation is lower than 1,5 m. Included are; previous arable land that is becoming overgrown or has been planted, seed orchards, low productivity pasture and grazing, natural meadows and grassland, land set aside for building and gardens of open characters outside aggregated development, non-built allotment areas, heath acide and sand beaches. Land allotted for particular operations e.g. slalom slopes, shooting ranges and quarries.

Water surface Area for sea, lake, ponds or watercourses.

Arable land Area ploughed for cultivation of cereals, ley farming, oil plants, root vegetables and crops excluding fruits and berries grown on trees. Included are grazings tilled for cropping, field-like pastures in rotation and land used for cultivation of energy forest. Hayfields and gardens in connection to dwellings are not included. Arable land in tread is included under this category.

8.4 Appendix 4 – Pond descriptions

Short notes and description of sampled ponds. The number preceding the name corresponds to locations on Fig. 1. All unaccredited photos have been taken by me.

1. Beckombergadammen Is situated in a small park in front of the former Beckomberga Hospital. It is a small flat rock pond supposedly artificially made for amphibians to spawn in. The pond was completely covered in common duckweed (Lemna minor) both at the sampling in spring and the revisit at the end of the summer. Apart from the insects found, there were also frog tadpoles present.

2. Beckombergapölen Is located in an uphill forest area in Beckomberga and had very brown humic water. Most likely a natural pond, located not to far away from an apartment complex. The most notable vegetation apart from the large Scots pines (Pinus sylvestris) includes mosses and a lot of common duckweed. Dead trees have fallen over the pond.

3. Brotorpsdammen This pond lies next to a relatively new residential area but is surrounded by high fencing. The area is mostly woodland and it is difficult to reach due to all the shrub vegetation along the shore constituting of mostly alder and Salix-species. The pond houses both submerged vegetation in the middle of the pond and emergent vegetation along the shore. Some notable species include white water lily (Nymphaea alba), swamp cinquefoil (Potentilla palustris) and common reeds (Phragmites australis). Some small fishes were visible at the sampling time.

4. Hjulsta vattenpark Is a city park pond with two pools divided by a cross-over in between and it is part of the Spånga creek. The pond is situated just downhill a large apartment complex and is mostly bordered by grasses but parts of the shoreline is eroded due to all the waterfowl in the pond. There are dense stands of common bulrush (Typha latifolia) and yellow flag (Iris pseudacorus). A small patch of yellow water lilies (Nuphar lutea) covers a part of one of the pools and the water is very turbid. I caught some small fish fry during sampling.

5. Ikea-dammen The pond is situated on a field and cut off from the nearby road by a mound with a thick bush layer. The pond was flooded at the time of sampling, drastically increasing the surface area. Due to this the most of the vegetation is situated near the middle of the pond and includes different types of emergent vegetation, mostly bulrush (T. latifolia). The submerged vegetation is to a large part flooded grass and mosses.

6. Johanneslundsdammen Is one of a couple of ponds along the Nälsta trench. The pond is bordered by a lot of vegetation including shrubs, grasses and sedges. A continuous band of common reed (P. australis) emerges from the ditch into the pond and there are small stands of bulrush (T. latifolia). A small pier is covering a part of the pond from which a shoal of nine-spined sticklebacks (Pungitius pungitius) was visible at the time of sampling.

7. Judardammen A small pond next to the lake Judarn in a small nature reserve. It is about 200 m to the nearest residence. The area is surrounded by forest but the pond lies in an open area and is frequently visited by people, e.g. there were two preschool classes there two days in a row scooping insects when I was planning to do my sampling. There were a lot of submerged vegetation, mostly pondweed (Elodea canadensis), some bulrush (T. latifolia) and small bushes of black alder (Alnus glutinosa) along the shore. Both Common Newt (Lissotriton vulgaris) and Great Crested Newt (Triturus cristatus) was found in the pond. At the revisit in August a fence had been put up to follow the recruitment of the Great Crested Newt.

8. Kallhällsdammen A city park pond in a recreational area next to a school. The pond is bordered by trees and bushes hanging out over the water. There is a fountain in the middle of the pond and the water is turbid and no submerged vegetation could be seen during the visits. There were lots of waterfowl and parts of the shoreline have eroded. There are two sections of common reed (P. australis) and one with yellow iris (I. pseudacorus) and other emergent vegetation. Both small fishes and large carps (Cyprinus carpio), common and ornamental Koi was visible.

9. Kymlingedammen A small pond between a residential area and Kymlingelänken, a heavily trafficked road connecting the northern Stockholm area in an east-westerly direction. The area surrounding the pond is mainly field and the dominating vegetation around the pond is mostly bulrush. The submerged vegetation is to a large extent broad-leaved pondweed (Potamogeton natans). There are also some Salix bushes and sedges around the pond.

10. Lilla Frösunda dagvattendamm A small city park pond. The water is turbid and there is lots of vegetation in and around it including bulrush (T. latifolia), sedges and common reed (P. australis) as well as some shrubs. The pond is located 10 meters from a heavily trafficked road and about 750 meters northwest lies the large Friends Arena.

11. Lilla Vibydammen Stormwater pond from 2007. The surrounding landscape is mostly field with some small alder shrubs at the shoreline. There is plenty of bulrush (T. latifolia) growing along the shoreline and some common duckweed (L. minor) in the bend of the boomerang-shaped pond. There were lots of algae near the outlet of the pond and I saw signs of what could have been fish. Photo: WRS Uppsala AB

12. Linneaholms dagvattendamm A small pitched stormwater pond next to the E4-road surrounded by trees, bushes and an adjacent bike path. There were some bulrush and rush growing in stands in the pond and the surrounding vegetation cast some shadow over the pond. There were also sludgy algae in the pond and many Common Newt larvae were caught during sampling.

13. Lötsjödammen The outlet of lake Lötsjön flows directly to this small pond situated in a city park area in Sundbyberg. The water was turbid and no submerged vegetation was visible, but the pond had much shoreline vegetation including large reeds. A few large mirror carps (Cyprinus carpio) surfaced now and then. The pond had a small ditch-like outlet. A few trees and shrubs of Salix were also present around the pond.

14. Mälarvägsdammen A quite new stormwater pond next to heavily trafficked roads in north and east direction. There is only sparse vegetation around the shoreline, including some kingcup (Caltha palustris) and planted yellow iris (I. pseudacorus). The shoreline consists of mostly gravel and stones and there is a thick sludgy layer of algae covering parts of the pond.

15. Näckrosparksdammen A park pond situated next to Råsunda church. There were some bulrush and both yellow and white water-lilies growing in the pond. Water horsetail (Equisetum fluviatile), sedges, ferns and common butterbur (Petasites hybridus) grow along the shoreline. The pond is located in a relatively rocky high elevation area and one of the bordering sides consists of a stone slab sloping down into the pond. Common Newt was found in the pond.

16. Olovslundsdammen A shallow artificially made city park pond with a cloth underneath. There was plenty of emergent and submerged vegetation. The type of vegetation bordering the pond includes common reed (P. australis), sedges, water-horsetail (E. fluviatile) and arrowhead (Sagittaria sagittifolia). There were also larger trees around the pond and a playing area for children with a concrete paddling pool. Both Common Newt and Great Crested Newt were found.

17. Polhemsdammen A small pond in a forest area next to a road and some residential homes. The surrounding trees are mostly Scots pine (P. sylvestris) and some small bushes. There was some yellow iris (I. pseudacorus) and bulrush (T. latifolia) and some bogbean (Menyanthes trifoliata) in one of the corners. Both Common Newt and Great Crested Newt was found during sampling. The pond was completely dried out in August at the revisit and the bottom was covered with water lilies.

18. Råckstadammen A small pond of a few square meters, almost like a pit in the vegetation just next to Råcksta lake. The pond is bordered by vegetation in all directions and a large bush is covering almost half of the pond’s total area. Common reed, bulrush, meadowsweet (Filipendula ulmaria) and water lobelia (Lobelia dortmanna) are some of the notable species of the surrounding vegetation. Common Newt was seen emerging to the surface.

19. Solparksdammen A very small city park pond apparently built in the 1920s according to a woman on site who was there for the opening ceremony of the pond when she was about 10 years old. Today not much is left but a shallow puddle and some small stones and some surrounding grass vegetation. The pond lies in a small park area in-between apartment blocks and sided by paved roads in all directions. Rebuilt in 2005 to include the current water course.

20. Stora Frösunda gårds damm An old private owned pond supposedly on maps from the 18th century. There were some bush vegetation and trees growing around the pond and a stone wall hedged in the southern part. There had apparently been three grass carps (Ctenopharyngodon idellus) in the pond that may not have survived the winter. A small fountain let out oxygenated water in the middle and there were some duckweed covering parts of the pond. Lots of large butterbur (Petasites hybridus) was growing along one of the edges.

21. Vegadammen A pond between residences in a small woodland area. Is surprisingly secluded despite being close to buildings. The northern shore is dominated by common reed and the southern part has mostly bulrush. The west part is mainly a marshy area beneath a bush layer with short-leaved emergent vegetation. Forest in the east and west and a scrubby field in the north surround the pond. There were some waterfowl in the pond and Common Newt was found during sampling. There have been fish introduced by kids according to some passerby’s but there were no signs of fish at the time of sampling or at the revisit.

22. Vibydammen An artificially made pond with unfinished concrete structures on site, which gives it an abandoned look. The pond is situated next to a residential area and a small nature reserve. Bulrush, common reed, yellow iris and sedges constitute most of the surrounding vegetation. The submerged vegetation is completely dominated by water soldier (Stratiotes aloides) and part of the floating vegetation was star duckweed (Lemna trisulca). There is a small island in the pond with small trees. There were lots of Common Newts in the pond and many swimming grass snakes (Natrix natrix).

23. Vällingbyrondellens dagvattendamm A stormwater pond next to the Vällingby roundabout. There is two major pools divided by a small neck filled with a dense stand of bulrush. Sedges, common reed and yellow flag can be found along the shoreline. Paved roads on three sides surround the pond and there are a few Norway maples (Acer platanoides) and small-leaved limes (Tilia cordata) next to it.

24. Ålstensskogen A small humic forest pond on a rocky hill. The standing water is located on a flat rock and is surrounded by mostly Scots pine (Pinus sylvestris) but also some birch (Betula pendula) and alder (Alnus glutinosa). The pond is bordered by grasses and bogbean (M. trifoliata) but there is no visible vegetation in the pond.

25. Överjärva branddamm A small pond formerly used as a fire dam and situated next to a golf course. The shore is mostly hard stone surfaces except in one end that is managed lawn. The pond was mostly covered by bulrush and duckweed. Some large trees; maples (A. platanoides), bird cherry (Prunus padus) and elm (Ulmus glabra) grow around the pond. Both Common Newt and Great Crested Newt was found in the pond.

26. Överjärva dagvattendamm E4 A stormwater pond next to a bike path and the E4-road, on the other side there is a small nature reserve with deciduous old-growth forest. There is bulrush around the pond and some other emergent vegetation including arrowhead (S. sagittifolia) and rush. Several Common Newts were visible in the pond.

Word Dictionary (Swedish – English) Damm-en – Pond Pöl-en – Puddle/Pool Dagvattendamm-en – Stormwater pond Branddamm-en – Fire dam/Fire brigade reservoir Lilla – Small Stora – Big Vattenpark-en – Water Park Rondell-en – Roundabout