Freshwater Invertebrate Survey Great Fen Spider Pools Redgrave and Lopham Fen NNR, SAC. August 2013

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1 Freshwater Invertebrate Survey Great Fen Spider Pools Redgrave and Lopham Fen NNR, SAC August 2013 Great Fen: Spider Pool 1 with pool 2 just behind. A report prepared for Suffolk Wildlife Trust Adrian Chalkley Boxvalley AquaSurveys bas@boxvalley.co.uk 37 Brook Hall Road, Boxford Suffolk CO10 5HS bas@boxvalley.co.uk Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 1 of 33

2 Circulation List Richard Young Dorothy Casey Martin Sandford Dr Helen Smith SWT Valley Fens Warden. CDr copy with survey photos. Electronic copy for SWT records at Brooke House. Electronic copy for Suffolk Biological Records Centre. Electronic copy for information: Fen Raft Spider program. Summary This mosaic of 20 pools and a scrape created in November 2012 is still in the first or migration stage of the hydrosere 1. Aquatic macrophyte growth was just starting to develop and therefore limited the available habitat for invertebrates. The Natural England Methodology developed for use with their ISIS survey tool for Common Standards Monitoring was used for this survey. The present freshwater invertebrate community is very largely, though not exclusively, made up of water beetles and aquatic bugs. Redgrave and Lopham Fen has a rich water beetle fauna with 8 red data book, 18 nationally notable and numerous common species. This survey found that 6 red data, 5 nationally notable and several common species have already colonised the pools, along with one notable corixid bug. Use of the Community Conservation Index metric (CCI) developed by The Environment Agency and applied via the SAFIS 2 electronic analysis software developed by the author shows that many of the pools already have an invertebrate community which has a sufficiently high conservation value to reflect the protected status enjoyed by Redgrave and Lopham Fens as a whole. The overall CCI score when applied to the mosaic of small pools was with 58 species contributing to that score. Quoting from the original CCI research paper this equates to: A site of very high taxon richness and very high conservation value, potentially of national significance which may merit statutory protection. Overall water quality in the pools is good, though during the hot summer of 2013 water levels were relatively low. Physical characteristics (averaged over 6 samples) Water temperature ph Conductivity Total dissolved solids 23 o C µs 505 ppm 1 Succession specific to freshwater is known as a hydrosere. 2 SAFIS Site Analysis for Freshwater Invertebrate Surveying, usually available for download at or the author. Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 2 of 33

3 Contents Introduction... 4 Site Description and Weather Conditions... 4 Photographs of the Spider Pools on Great Fen... 5 Figure 1: Site Location Maps... 7 Methodology... 8 Figure 2: Map of the 6 pairs of pools sampled Species Determination Analysis of Results Biomonitoring Analysis Interpretation of the Calculations Results Table 1: Physical measurements Table 2: Analysis Results, BMWP & ASPT Table 3: Analysis Results, CCI Species Tables for all Six Pairs of Pools Surveyed Table 4: Spider Pools pair A Table 5: Spider Pools pair B Table 6: Spider Pools pair C Table 7: Spider Pools pair D Table 8: Spider Pools pair E Table 9: Spider Pools pair F Note: Snails from the Limnephilid caddis case found at site F Discussion Important Species Freshwater Beetles: Coleoptera Freshwater Bugs: Heteroptera Comparison of the Survey Results with other sites in Suffolk References Appendix 1 Complete Species Table for the whole site Appendix 2 An explanation of the analysis methods Appendix 3: National Status definitions Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 3 of 33

4 Introduction Redgrave and Lopham Fen is the largest remaining valley fen in England. Despite damage caused to the fen by water abstraction and land drainage prior to 1999, intensive restoration measures have caused the degraded habitats on site to settle into a more stable state. The fen has a very long list of rare invertebrates which have been recorded including the Fen Raft Spider, Dolomedes plantarius and many Red Data Book or Notable aquatic beetles and snails. In November 2012 a series of 20 shallow pools and a scape were excavated in compartment 1 of Great Fen with the expectation that they would, as they mature, extend the habitat available to the population of Fen Raft Spiders. This survey was commissioned in order to provide base line data of all freshwater invertebrate species which have begun to populate the new pools. It is planned to repeat the survey in years 2 or 3 and again in years 3 or 4 depending on the results detailed in this report. Site Description and Weather Conditions Compartment 1 of Great Fen is centred at Ordnance Survey grid reference TM The spider pools excavated in November 2012 are situated in a broad sweep between this point and the southern margin of the compartment at an average altitude of 24 metres above sea level. A first visit was made to the site on May 14 th in the company of Kerry Vaughan. After a long winter and a very wet spring the pools were large and deep; the surrounding fen was full of standing water, the ground underfoot very soft and comprised of deep, wet, peaty silt typical of the spring fed calcareous fen for which the site is known. Unfortunately due to unavoidable problems the contract for this survey was not finalised until the middle of July. It was therefore August before the survey could start and after many weeks of hot weather the ground water level on the fen had considerably reduced with the pools shrunken in size and depth, at least one pool had completely dried. The scrape had become a shallow depression with only a small number of puddles of standing water which were clearly not going to repay sampling effort as much as the pools themselves. It was therefore decided to restrict the survey to a representative selection of as many of the 20 pools as could be achieved in the time allocated. During preliminary conversations with Kerry Vaughan it was anticipated that a single day would be spent sampling four sites in Great Fen. However a heavy rainstorm on the day in question meant that only three sites were completed (it being impossible to accurately sample aquatic invertebrates whilst they are being washed into the grass from the plastic sheet specified in the methodology!) So in the end two slightly shorter days were used for the survey with three sites sampled per day giving results for six sites instead of four. Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 4 of 33

5 The first survey day was on Friday August 9 th when the weather was overcast with sunny periods and that heavy thundery rainstorm in the early afternoon. The ground underfoot on Great Fen was firm though moist with the water level in the pools some 25 cms below maximum. The second sampling day took place on Friday August 23 rd when the weather was hot and sunny all day. Great Fen was even drier after two more weeks of continuous hot weather and the levels in all the pools had dropped approximately another 10 cms. Photographs of the Spider Pools on Great Fen A full set of detailed photos is included on the Redgrave report copy on CD, only a representative range of pools are shown below, with the date of photography. Spider pool 7, sample B August 23rd Spider pool 13, sample C August 23 rd. Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 5 of 33

6 Spider pool 14, sample F August 9 th. The scrape was almost totally dry. Only small amounts of aquatic vegetation have started to grow as yet. Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 6 of 33

7 Figure 1: Site Location Maps Map of Redgrave & Lopham showing the location of Great Fen within the reserve. The Spider Pools surveyed are located in compartment 1 of Great Fen, inset. Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 7 of 33

8 Methodology After discussion with the reserve manager, Kerry Vaughan, the methodology chosen was that specified for still waters by Natural England in their ISIS survey tool. Still-water faunas are usually dominated by adult beetles, bugs and molluscs, for which this method produces high yields. It was felt that this methodology would not only be the most appropriate for the site but is easily repeatable for future surveys. In addition to invertebrate sampling a range of physical measurements were taken at each sample site using an electronic meter. These were: water temperature, ph, conductivity and total dissolved solids. I use a slight deviation from the strict ISIS method in that, whenever open water is sampled, the water surface is first observed to establish the presence of surface dwelling invertebrates such as Pondskaters or Whirligigs. These have a habit of escaping out to open water as soon as the net enters the water; therefore when present they were caught prior to the ISIS methodology being employed. I also sample open water for Cladocera (Water Fleas) with a plankton net, though none were found during this survey. The standard ISIS methodology may be summarised thus: The sampling method standardises effort by bank-sorting three qualitative hauls for 10 minutes each, giving 30 minutes of sorting. The emphasis is on free-style netting of features (microhabitats) that are likely to be the most productive. Effort is deliberately not divided in proportion to the extent of features since species are not distributed in this fashion. The net used is the standard FBA design with a rectangular frame 25cm wide and 22cm long, the net bag 30cm deep with a 1mm mesh. While standing in or at the water margin, the vegetation is netted using short jabbing thrusts in any dense emergent and raft-forming plants, and using occasional longer strokes into submerged plants and over bare substrate in deeper water. This is repeated along the bank as netting proceeds, selecting patches of vegetation that exhibit the greatest small-scale mosaic structure since these patches yield more specimens. Netting ends when the net begins to fill to the point that it becomes more difficult to push, usually after about 1 to 3 minutes when it is usually about a third to a half full of plant material. When duckweed or similar small plants are abundant, the net will fill within seconds, so some careful manipulation is needed to slow the rate that it was caught while probing for more productive structures beneath. Bottom sediment is avoided since it clogs the net and contains almost no species that contribute to the analysis, though grazing strokes across the sediment top are used to put up invertebrates such as beetles and bugs which are then caught in the net. Once the net is full a digital timer is used to time the 10 minutes sorting time as the sample is tipped onto a white polythene sheet and spread out quickly into a thin layer. Fast-crawling beetles, bugs and dragonfly larvae are collected or identified (if recognisable) before they escape during the spreading-out process. Many invertebrates, such as flatworms and leeches react badly to the alcohol used as a sample preservative, others such as Water Scorpion or Stick Insect are instantly Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 8 of 33

9 identifiable. During sorting these are placed in a bucket or tray of water. They are then identified, noted and returned alive to the water at the end of the sorting time. The white sheet is then scanned for other animals as they recover from their shock. After a few minutes, the debris is turned over and poked about, when more animals are usually found. A pool of water forms in the centre of the sheet which allows weakly swimming animals a refuge and to be seen, these are collected towards the end of each 10 minute time period. Fine flexible forceps are used for picking up animals; a tea strainer and white plastic spoon are used to net animals in the pool in the middle of the sheet. However a wet finger is often the best tool to pick up really small beetles and bugs. All are immediately put into a wide mouthed bottle containing 70 % alcohol. During the last two minutes of the search some of the debris is put into a white tray with 1-2cm depth of water. Feeble animals which swim free are collected. Lastly all plant material is tipped into a bucket of water, larger pieces and most of the water are removed. The heavy residue is tipped into the white tray with about 1cm of water. Then by tipping the contents to and fro, the molluscs left stranded in a pile are collected. At each sample site this operation is repeated twice more at bank sections about 25m apart. Giving 30 minutes of invertebrate sorting per site. The ISIS protocol results in one tube of animals per sample site which was then identified back in the laboratory. As no large amounts of debris or plant material are collected the identification process is much easier and needs no pre-sorting which is very time consuming and costly. However this survey is the first since the spider pools were dug in 2012, some eight months before, and as yet almost no aquatic vegetation has grown and most of the substrate was bare, black peaty silt. With no stands of vegetation net sweeps around the pool sides and just scraping the substrate were mostly the only kind that could be used. Occasionally small amounts of reed debris, newly growing clumps of Chara sp. or small floating mats of algae could also be sampled. With ISIS each net usually results in a large pile of vegetation to sort through on the white sheet in the ten minutes allowed, however here the white sheet had little vegetation for invertebrates to hide in and just a reasonably small amount of silt to be sorted. For this reason the methodology above had to be adapted. Therefore, for the most part two 5 minute counting periods replaced each 10 minute one, thus still giving the standard 30 minutes sorting time. A fine flour sieve was also employed at each pool to double check the peaty substrate for any invertebrates missed by the process above. Another slight problem with the standard ISIS methodology is that it is written for larger sites than these small spider pools, most of which do not have a single 25 metre stretch of bank. Therefore since the whole site is a mosaic of varying shaped small pools, pairs of adjacent pools were chosen as shown in the map below and each of these pairs of pools provided for one 30 minute sort. The pairs of pools were chosen on the basis of potential invertebrate habitat provided by any developing aquatic macrophytes. Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 9 of 33

10 The location of each pair of pools is given on the following map where each is labelled A to F. A full species list for each is given in the results section later in this report. Figure 2: Map of the 6 pairs of pools sampled Map courtesy of Google Earth, plotted by direct input of waypoints from a GPS receiver. Ordnance Survey Co-ordinates: A B C D E F TM TM TM TM TM TM Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 10 of 33

11 Species Determination. After specimen collection in 70% alcohol and on return to the lab the catch from each pair of pools was sorted into groups. Identification was completed using standard and up to date keys. Wherever required for accurate species determination the genitalia of males was dissected out, provided of course that males were taken. In a couple of cases where there was still some uncertainty microphotographs of the genitalia were ed to Professor Garth Foster for confirmation. Specimens are now stored in preservative in the collection of the author. Analysis of Results Biomonitoring Analysis For each pair of pools three standard measurements or metrics have been calculated, these are: The Biological Monitoring Working Party Score (BMWP Score) The Average Score Per Taxon (ASPT) The Community Conservation Index (CCI) The new spider pools form a relatively dense mosaic in a small area of Great Fen but are still developing. In future surveys it may not be possible or advisable to re-survey the same pairs of pools and so it was felt that it may also be useful to do an overall calculation of these metrics as a whole using the total species list. This gives a general value for the freshwater invertebrate community of Great Fen which should be directly comparable with any future surveys. Interpretation of the Calculations A full explanation of these three methods is given in Appendix 2 but in order to interpret the results in the table below the following may be a useful summary. BMWP is a measure of the water conditions, of oxygenation and cleanliness. As a guide the following may be used: Score < 25 = poor water conditions, = moderate, = good, = very good, more than 150 = exceptional. ASPT is based on the BMWP score and so also measures water quality. It is useful in showing year to year changes and trends in the invertebrate population supported by the water body. Being an average score, the higher its value the more ecologically valuable the population should be. Any value greater than 4 generally indicates good water quality but productive water bodies with large and varied populations will usually have an ASPT value between 4.5 and 5.0. Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 11 of 33

12 CCI is based on the rarity of the individual invertebrates living in the water. It gives a numerical value to the conservation importance of the aquatic community. The higher the CCI value the greater the conservation interest. CCI values can range from less than 5 for a site with little or no conservation value to a score greater than 20 for sites with very high conservation interest. This latter CCI value often indicates a site that is of national importance and may be of potential SSSI status. Results Table 1: Physical measurements Survey Site (see map) Water Temperature o C ph Electrical Conductivity 3 µ Siemens Total Dissolved Solids A B C D E F Table 2: Analysis Results, BMWP & ASPT BMWP No. of families contributing ASPT Score to BMWP / ASPT Water Quality Pools A Good Pools B Moderate Pools C Moderate Pools D Moderate Pools E Moderate Pools F Good Complete species list Great Fen Good 3 Conductivity measured in micro Siemens per metre referenced to a standard temperature of 25 o C Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 12 of 33

13 Table 3: Analysis Results, CCI CCI Score No. of species contributing to CCI Pools A Pools B Pools C Pools D Pools E Pools F Aquatic invertebrate community conservation value A community of very high taxon richness and very high conservation value, including species of national importance A community of high taxon richness and high conservation value, including uncommon or rare species. A community of very high taxon richness and very high conservation value, including species of national importance A community of very high taxon richness and very high conservation value, including species of national importance A community of very high taxon richness and very high conservation value, including species of national importance A community of very high taxon richness and very high conservation value, including species of national importance Complete species list Great Fen A community of very high taxon richness and very high conservation value, supporting several rarities including species of national importance. Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 13 of 33

14 Species Tables for all Six Pairs of Pools Surveyed A simple list of species for each sample pair of pools is given on a separate page for ease of comparison. More detailed data is presented in Appendix 1 which shows the complete species list for the whole of the Great Fen Spider Pools complex. Species with a shaded background do not contribute to the site analysis as will be explained in the discussion. 1 Table 4: Spider Pools pair A Species Name Description Status Amphipoda ~ freshwater shrimps or scuds Crangonyx A Freshwater Shrimp pseudogracilis Coleoptera ~ Water Beetles Locally common 2 Acilius sulcatus A Diving Beetle Common 3 Anacaena limbata A Water Scavenger Beetle Very common 4 Colymbetes fuscus A Diving Beetle Very common 5 Dryops anglicanus A long toed water beetle RDB3 6 Dytiscus semisulcatus A Great Diving Beetle Local 7 Enochrus coarctatus A Water Scavenger Beetle 8 Hydaticus seminiger A Diving Beetle Nb 9 Hydrobius fuscipes A Water Scavenger Beetle Local Very common 10 Ilybius ater A Diving Beetle Common 11 Liopterus haemorrhoidalis A Lesser Diving Beetle Local 12 Ochthebius minimus A Water Beetle Very common Diptera ~ true flies, not identified to species & don't contribute to CCI scores) 13 Chironomidae sp. Non Biting Midge larva Hemiptera ~ Aquatic bugs 14 Gerris lacustris The Common Pond Skater Very common 15 Gerris thoracicus A Pond Skater Occasional 16 Hesperocorixa moesta A Lesser Water Boatman Nb 17 Hesperocorixa sahlbergi A Lesser Water Boatman Common 18 Nepa cinerea Water Scorpion Frequent 19 Notonecta glauca Common Water Boatman Very common 20 Sigara falleni A Lesser Water Boatman Very common Isopoda ~ Water Slaters or Hog Lice 21 Asellus aquaticus Water Slater / Hog Louse Common Mollusca. Gastropoda ~ Univalve Snails 22 Anisus leucostoma Button Ramshorn.. Dead Occasional 23 Aplexa hypnorum Moss Bladder Snail Local 24 Bithynia tentaculata Common Bithynia Very common 25 Planorbarius corneus Great Ramshorn Frequent 26 Radix balthica Wandering Snail Very common Odonata ~ Dragonflies & Damselflies (larvae or exuviae) 27 Brachytron pratense The Hairy Dragonfly Occasional - increasing Pisces ~ freshwater fish (not invertebrates but as predators may affect them ) 28 Pungitius pungitius 9 Spined stickleback Common Trichoptera ~ caddis flies 29 Limnephilidae sp. A cased caddis fly Empty cases only Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 14 of 33

15 Table 5: Spider Pools pair B Species Name Description Status Coleoptera ~ Water Beetles 1 Acilius sulcatus A Diving Beetle Common 2 Agabus bipustulatus A Diving Beetle Very common 3 Agabus sturmii A Diving Beetle Very common 4 Colymbetes fuscus A Diving Beetle Very common 5 Cymbiodyta marginellus A Water Scavenger beetle Local 6 Dryops ernesti A long toed water beetle Local 7 Dytiscus marginalis A Great Diving Beetle Very common 8 Dytiscus semisulcatus A Great Diving Beetle Local 9 Haliplus ruficollis A crawling water beetle Very common 10 Hydrobius fuscipes A Water Scavenger Beetle Very common 11 Hydrochus angustatus A Water Beetle Nb 12 Liopterus haemorrhoidalis A Lesser Diving Beetle Local 13 Paracymus scutellaris A Water Scavenger Beetle Nb Mollusca. Bivalvia ~ Bivalves (Mussels & Cockles) 21 Pisidium sp. Pea Shell Mussel dead Mollusca. Gastropoda ~ Univalve Snails 22 Bithynia tentaculata Common Bithynia Very common 23 Radix balthica Wandering Snail Very common 24 Anisus vortex Whirlpool Ramshorn Very common 25 Planorbarius corneus Great Ramshorn.. dead Frequent Pisces ~ freshwater fish (not invertebrates but as predators may affect them) 26 Pungitius pungitius 9 Spined stickleback Common 14 Suphrodytes dorsalis A Diving Beetle Local Ephemeroptera ~ Mayflies or Up-winged flies 15 Cloeon dipterum The Pond Olive Very Common Hemiptera ~ Aquatic bugs 16 Gerris lacustris The Common Pond Skater Very common 17 Gerris thoracicus A Pond Skater Occasional 18 Hesperocorixa moesta A Lesser Water Boatman Nb 19 Hesperocorixa sahlbergi A Lesser Water Boatman Common 20 Notonecta glauca Common Water Boatman Very common Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 15 of 33

16 Table 6: Spider Pools pair C Species Name Description Status Amphipoda ~ freshwater shrimps or scuds 1 Crangonyx pseudogracilis A Freshwater Shrimp Locally common Coleoptera ~ Water Beetles 2 Acilius sulcatus A Diving Beetle Common 3 Agabus bipustulatus A Diving Beetle Very common 4 Colymbetes fuscus A Diving Beetle Very common 5 Helophorus longitarsis A Mud Beetle RDB3 6 Hydaticus seminiger A Diving Beetle Nb 7 Hydroporus angustatus A Lesser Diving Beetle Common 8 Hydroporus palustris A Lesser Diving Beetle Very common 9 Scarodytes halensis A Lesser Diving Beetle Nb Diptera ~ true flies, not identified to species & don't contribute to CCI scores) 10 Chironomidae sp. Non Biting Midge larva Ephemeroptera ~ Mayflies or Up-winged flies Isopoda ~ Water Slaters or Hog Lice 17 Asellus aquaticus Water Slater / Hog Louse Common Mollusca. Bivalvia ~ Bivalves (Mussels & Cockles) 18 Pisidium sp. Pea Shell Mussel dead Mollusca. Gastropoda ~ Univalve Snails 19 Aplexa hypnorum Moss Bladder Snail.. dead Local 20 Bathyomphalus contortus Contorted Ramshorn dead Common 21 Bithynia leachii Leach's Bithynia dead Local 22 Bithynia tentaculata Common Bithynia.. dead Very common 23 Planorbis carinatus Keeled Ramshorn.. Dead Very common 24 Radix balthica Wandering Snail.. Dead Very common Pisces ~ freshwater fish (not invertebrates but as predators may affect them) 25 Pungitius pungitius 9 Spined stickleback Common 11 Cloeon dipterum The Pond Olive Very Common Hemiptera ~ Aquatic bugs 12 Gerris lacustris The Common Pond Skater Very common 13 Gerris thoracicus A Pond Skater Occasional 14 Hesperocorixa moesta A Lesser Water Boatman Nb 15 Hesperocorixa sahlbergi A Lesser Water Boatman Common 16 Notonecta viridis A Water Boatman Local Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 16 of 33

17 Table 7: Spider Pools pair D Species Name Description Status Coleoptera ~ Water Beetles 1 Agabus bipustulatus A Diving Beetle Very common 2 Colymbetes fuscus A Diving Beetle Very common 3 Hydroporus palustris A Lesser Diving Beetle Very common 4 Hygrotus inaequalis A Lesser Diving Beetle Common 5 Scarodytes halensis A Lesser Diving Beetle Nb Ephemeroptera ~ Mayflies or Up-winged flies 6 Cloeon dipterum The Pond Olive Very Common Hemiptera ~ Aquatic bugs 7 Callicorixa praeusta 8 Corixa dentipes 9 Corixa panzeri A Lesser Water Boatman A Lesser Water Boatman A Lesser Water Boatman Frequent Local Local 10 Gerris thoracicus A Pond Skater Occasional 11 Hesperocorixa moesta 12 Hesperocorixa sahlbergi A Lesser Water Boatman A Lesser Water Boatman Nb Common 13 Nepa cinerea Water Scorpion Frequent 14 Notonecta glauca Common Water Boatman Very common 15 Notonecta viridis A Water Boatman Local Mollusca. Gastropoda ~ Univalve Snails 16 Bithynia tentaculata Common Bithynia.. dead Very common 17 Planorbis carinatus Keeled Ramshorn Very common Trichoptera ~ caddis flies 18 Leptoceridae sp. Empty case Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 17 of 33

18 Table 8: Spider Pools pair E Species Name Description Status Amphipoda ~ freshwater shrimps or scuds 1 Crangonyx pseudogracilis A Freshwater Shrimp Locally common Coleoptera ~ Water Beetles 2 Acilius sulcatus A Diving Beetle Common 3 Anacaena limbata A Water Scavenger Beetle Very common 4 Colymbetes fuscus A Diving Beetle Very common 5 Cymbiodyta marginella A Water Scavenger beetle Local 6 Dytiscus marginalis A Great Diving Beetle Very common 7 Hydrobius fuscipes A Water Scavenger Beetle Very common 8 Hydrochus elongatus A Water Beetle RDB3 9 Hydroporus angustatus A Lesser Diving Beetle Common 10 Hydroporus sp. Female A Lesser Diving Beetle Male needed for ID 11 Laccobius bipunctatus A Water Scavenger Beetle Very common 12 Limnebius aluta A Water Beetle RDB3 13 Scarodytes halensis A Lesser Diving Beetle Nb Diptera ~ true flies, not identified to species & don't contribute to CCI scores) 14 Chironomidae sp. Non Biting Midge larva 15 Stratiomys sp. Soldier fly larva Hemiptera ~ Aquatic bugs 16 Callicorixa praeusta A Lesser Water Boatman Frequent 17 Hesperocorixa linnaei A Lesser Water Boatman Occasional 18 Hesperocorixa moesta A Lesser Water Boatman Nb 19 Hesperocorixa sahlbergi A Lesser Water Boatman Common 20 Notonecta glauca Common Water Boatman Very common Isopoda ~ Water Slaters or Hog Lice 21 Asellus aquaticus Water Slater / Hog Louse Common Mollusca. Bivalvia ~ Bivalves (Mussels & Cockles) 22 Pisidium sp. Pea Shell Mussel dead Mollusca. Gastropoda ~ Univalve Snails 23 Bithynia tentaculata Common Bithynia Very common 24 Lymnaea fusca Marsh Snail Common 25 Planorbis carinatus Keeled Ramshorn.. Dead Very common 26 Valvata cristata Flat valve snail.. Dead Common Odonata ~ Dragonflies & Damselflies (larvae or exuviae) 27 Aeshnidae sp. Possibly Anax imperator.. Early instar 28 Coenagriidae sp. Early instar, no id 29 Ischnura elegans The Blue-tailed Damselfly Very common 30 Libellulidae sp. Early instar, no id Ostracoda ~ ostracods or 'seed shrimps' 31 Ostracoda sp. Mussel Shrimp Pisces ~ freshwater fish (not invertebrates but as predators may affect them) 32 Pungitius pungitius 9 Spined stickleback Common Trichoptera ~ caddis flies 33 Limnephilidae sp. 2 Empty cases Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 18 of 33

19 Table 9: Spider Pools pair F Species Name Description Status / notes Amphipoda ~ freshwater shrimps or scuds 1 Crangonyx pseudogracilis A Freshwater Shrimp Locally common Coleoptera ~ Water Beetles 2 Acilius sulcatus A Diving Beetle Common 3 Agabus bipustulatus A Diving Beetle Very common 4 Anacaena limbata A Water Scavenger Beetle Very common 5 Coelostoma orbiculare A Water Scavenger beetle Common 6 Colymbetes fuscus A Diving Beetle Very common 7 Cymbiodyta marginella A Water Scavenger beetle Local 8 Dytiscus marginalis A Great Diving Beetle Very common 9 Enochrus coarctatus A Water Scavenger Beetle Local 10 Enochrus isotae A Water Scavenger Beetle RDB3 11 Haliplus ruficollis A crawling water beetle Very common 12 Hydaticus seminiger A Diving Beetle Nb 13 Hydraena riparia / britteni ** A Water Beetle (female) (male needed) Local 14 Hydrobius fuscipes A Water Scavenger Beetle Very common 15 Hydrochus carinatus A Water Beetle RDB3 16 Hydrochus elongatus A Water Beetle RDB3 17 Hydroporus angustatus A Lesser Diving Beetle Common 18 Hydroporus palustris A Lesser Diving Beetle Very common 19 Limnebius aluta A Water Beetle RDB3 20 Noterus clavicornis The larger Noterus Local 21 Rhantus grapii A Diving Beetle Nb ** See species accounts Diptera ~ true flies, not identified to species & don't contribute to CCI scores) 22 Chironomidae sp. Non Biting Midge larva 23 Stratiomys sp. Soldier fly larva Ephemeroptera ~ Mayflies or Up-winged flies 24 Cloeon dipterum The Pond Olive Very Common Hemiptera ~ Aquatic bugs 25 Corixa punctata A Lesser Water Boatman Very common 26 Gerris lacustris The Common Pond Skater Very common 27 Hesperocorixa moesta A Lesser Water Boatman Nb 28 Hesperocorixa sahlbergi A Lesser Water Boatman Common 29 Nepa cinerea Water Scorpion Frequent 30 Notonecta glauca Common Water Boatman Very common Isopoda ~ Water Slaters or Hog Lice 31 Asellus aquaticus Water Slater / Hog Louse Common Mollusca. Gastropoda ~ Univalve Snails 32 Bithynia tentaculata Common Bithynia Very common 33 Lymnaea fusca Marsh Snail - Dead shells Common 34 Planorbarius corneus Great Ramshorn.. Dead Frequent 35 Radix balthica Wandering Snail Very common Oligochaeta ~ True Worms 36 Enchytraeidae sp. True Worms Odonata ~ Dragonflies & Damselflies (larvae or exuviae) 37 Ischnura elegans The Blue-tailed Damselfly Very common 38 Libellulidae sp. Early instar, no id Trichoptera ~ caddis flies 39 Limnephilidae sp. Empty case made of snail shells Tricladida ~ free living flatworms 40 Dugesia sp. Hatched cocoons Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 19 of 33

20 Note: Snails from the Limnephilid caddis case found at site F Bithynia tentaculata, Hippeutis complanatus, Planorbis carinatus, Bithynia leachii, Radix balthica and Lymnaea fusca. All these species were found elsewhere on site either alive or as dead shells except for Hippeutis complanatus. It is highly probable then that this caddis case was constructed in the ditches bordering the fen and washed in during the winter. Discussion The new Spider Pools in Great Fen were only dug some eight months before the present survey and have therefore had only a limited time to develop any aquatic vegetation which would provide habitat cover and feeding opportunities for invertebrates. In many pools some small amounts of stoneworts, Chara sp. had begun to appear and there were also some clumps of reed debris and float grass which provided sampling possibilities. Otherwise the water was clear, albeit with a pale straw colouration, allowing the peaty silt substratum to be clearly visible at least before the net entered. Despite the recent sunny weather the number of pools with any amount of visible patches of floating or submerged algae was surprisingly small. Elsewhere even newly excavated ponds will often quickly develop extensive algal blooms and this may reflect low nutrient levels in the water of these spider pools on Great Fen. Dr Helen Smith also visited the site for a short time on the first survey day and agreed that at this stage in the maturity of the pools they are not suitable as yet for the Fen Raft spider to colonise but hopefully this situation will change as time progresses. As may be expected the invertebrate community at present is largely composed of water beetles and aquatic bugs which can fly in to exploit new habitats. Redgrave as a whole has a rich water beetle fauna with 8 red data book, 18 nationally notable and numerous common species. The survey found that 6 red data, 5 nationally notable and several common species had already colonised the pools, along with one notable corixid bug. One species which was easily found in two thirds of the pools sampled was the Nine Spined Stickleback, Pungitius pungitius. These fish will have moved out of the surrounding dykes during the flooding of the site in the winter and may have some effect on the invertebrate numbers during the early development of the pools whilst macrophyte cover is largely unavailable. Small invertebrates such as aquatic fly larvae and water fleas would probably be most affected though small water beetles may also be taken. No water fleas were in fact found during the survey, though it may be expected that the soil of the fen would have contained resting eggs, ephippia, from earlier periods when suitable aquatic habitat was present. Ephippia may remain viable for hundreds of years in dry mud and hatch when conditions are again favourable. Of course after a long winter numbers hatching could be very low and therefore the stickleback may have depleted any population present. During the survey many early instars of both dragonflies and damselflies were found. These will have hatched from eggs laid in 2013 as the weather warmed up after the early spring. Unfortunately these were almost all too immature for a full identification to take Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 20 of 33

21 place but indicate a good future population of these invertebrates. Though the Odonata have obviously started to use the pools already no early instar caddis larvae were found. Whilst many caddis are relatively weak fliers others do fly well so it might be expected that early instars would also have appeared. This remains somewhat unexplained though unhatched eggs from the early summer would not have been seen. Since many species of caddis are thought to have a summer diapause which would carry them over any dry period it may well be that a caddis population will appear later in However several mature caddis cases were present though these were empty, so either the larvae had been extracted and eaten or the pupae had hatched and flown. It is very likely that empty cases could have washed in during any winter inundation or indeed that cases containing larvae or pupae had arrived in the same way and completed their life cycle this year. The other major group which may be expected to prominently figure in survey results is the Mollusca since Redgrave as a whole is well known to be excellent for this taxon. Whilst there were many snail shells found, which have been identified to species, they have not been included in the analysis unless that species was found alive. Empty shells that were found were either long dead, and therefore stained black by the fen soil, or had relatively recently died and possibly floated in during the winter. Some living snails will have also arrived in this way. There is some evidence that on average one mollusc species arrives at new water bodies every nine years where that water body is more isolated. At Great Fen it is likely that the pools will attain a mollusc community relatively quickly because of their proximity to established ditches. Most of the snails and dragonflies and all caddis fly species could not therefore be used for site analysis and appear with shaded backgrounds in the species tables. Important Species The ecology, status and distribution of any rare or scarce species found during the survey, from a national and / or county perspective, is briefly covered here. Status values given are firstly those used for the calculation of CCI (Chadd & Extence, 2004), in the analysis of results followed by any update of the IUCN status (in brackets) from the JNCC Review of the scarce and threatened Coleoptera (Foster, 2010) Species with no status in brackets have no IUCN designation. Freshwater Beetles: Coleoptera Note: ** (See species list above) From pool pair F a female Hydraena beetle was collected. This could only be identified to one of three species without a male from which the genitalia could be extracted. The three species could be Hydraena rufipes, H. riparia or H. britteni. However H. rufipes is a Lotic species of rivers or streams, which leaves the other two Lentic species, both of which have the status of Local and both of which occur in East Anglia. However H. riparia is possibly the most likely candidate since it has been recorded in both Little Fen and Middle Fen in 1965 and 1966 (Pope, ). Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 21 of 33

22 Dryops anglicanus Dryopidae RDB3 (Near Threatened) D. anglicanus is a northern and central European species extending to the Adriatic and the central Russian steppe. In the British Isles it is something of an East Anglian speciality and the recorded sites are exclusively relict and natural in origin, e.g. the Broadland fens of East and West Norfolk; Wicken Fen, Cambridgeshire and here at Redgrave and Lopham Fen. The only other records since 1980 are from a fen in Berwickshire, Scotland. The Suffolk database for freshwater invertebrates lists 2 other records for D. anglicanus from Redgrave & Lopham Fen, one in 2000 and one from Otherwise it has only been recorded from the nearby Lopham Little Fen in 1989, 2004 & These fens must therefore be viewed as a priority habitat for the species within Suffolk. This species is confined to wet vegetation at the edge of relict, lowland fen and fen carr, often in association with tussocks. Its larvae have been found under bark of wet, rotting tree debris. Adults occur throughout the year and larvae have been found in winter. Threats Drainage and pollution of natural fenland sites must result in localised extinction of this species. Redgrave and Lopham Fens were identified in 1996 as being at high risk of damage from excessive abstraction of water for public supply. It has therefore been important to monitor the continued presence of the species in Management and conservation The association with rotting wood indicates a possible need to maintain this feature within fen habitats but maintenance of a tussocky fen may be just as important. Enochrus isotae Hydrophilidae RDB3 (Vulnerable) Friday, 1988 gives this species to occur only rarely in the west and east of the British Isles. Records on the National Biodiversity Network are spread in the main across East Anglia with scattered sites to the west. There are old records from the Balfour Browne Club (water beetles) of records in the area of Redgrave Fen but this is the first record on the Suffolk database. The species is considered to be important as an indicator of undisturbed fens. Helophorus longitarsis Helophoridae RDB3 (Nationally Scarce) H. longitarsus is another beetle which is rarely recorded in Suffolk and there is only one record in the county database, at Great Glemham in The NBN shows a very scattered distribution mainly in temporary waters and ponds with a silty substratum. Hydaticus seminiger Dytiscidae Notable B (Nationally Scarce) This species has a scattered distribution across Ireland and in Britain occurs in the South East, North East Wales and Cheshire, as well as across East Anglia, in a broad sweep from Luton to the Norfolk Broads. The Suffolk database lists 13 other records for H. seminiger ranging from 1966 to of those records are from Redgrave, including the both the first and last. As a species it is associated with permanent standing waters, usually amongst dense vegetation or debris. Here at Redgrave it was collected in very low numbers amongst reed debris and should do better once vegetation establishes. In many sites it is associated with peat cuttings, floating bogs and small pools as here, mostly it is considered a species of shady waters so the spider pools on Great Fen are rather untypical in this respect. Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 22 of 33

23 Hydrochus angustatus Hydrochidae Notable B (Nationally Scarce) H. angustatus has a scattered distribution across much of England and Wales with a rather denser patch of records from the South East and another in East Anglia. The Suffolk Database has only three records from the turn of the century by Morley and Chitty, one of which was from Brandon at a site also on the Little Ouse. Hydrochus carinatus Hydrochidae RDB3 H. carinatus has been recorded 5 times before from Redgrave and Lopham on dates ranging from 1985 to 2005; there are also records from Market Weston Fen further along the Little Ouse to the west. Otherwise in Suffolk there is one 1955 record from cattle troughs at Flatford Mill. It has a distribution in Britain which is mainly centred to the south of the Wash; in Cambridgeshire, North Suffolk and West Norfolk. Like most of the other species in these accounts it is associated with lowland fen habitats and will require the same management criteria. Hydrochus elongatus Hydrochidae RDB3 (Near Threatened) H. elongatus is mainly a central European species, ranging over Britain, Denmark, Sweden, east Siberia, Italy, the former Yugoslavia and Turkey. In the British Isles there are records in the last 30 years from several East Anglian counties as well as in the South West, Derbyshire and Yorkshire. This species occurs in shallow, well vegetated, still water, often in reedbeds and other areas with rich emergent vegetation over clay, in low-lying areas. Although Hydrochus species are aquatic as adults and larvae, they do not swim. They are slow in their movements, and feign death when disturbed. Adults feed on algae according to Archangelsky (1998) but the larval diet is unknown. There are records for 38 hectads in England from 1980 onwards. The species has contracted in range, owing to loss of sites in Scotland, north-east England, the London area, south-west England, and possibly Wales. The only recent records for East Anglia are from the Halvergate Marshes and Redgrave and Lopham Fens, but not from the Norfolk Broads. Threats Loss of fenland habitats, particularly reedbeds, will be detrimental to this species. Management and conservation Restoration of fenland ditches and ponds should take into account the need to retain reedbeds. However this species can colonise manmade ponds once they are well established. It is probable that the main population on Great Fen is in the well vegetated waters bordering the site but that it may do well in the new pools once vegetation establishes. Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 23 of 33

24 Limnebius aluta Hydraenidae RDB3 (Near Threatened) L. aluta is known from central Europe, Scandinavia, Poland, Hungary, and the central Russian steppe. British records since 1980 are for Somerset, West Suffolk, Norfolk, Cambs, North-east Yorks, and Anglesey. It is known from 21 hectads in England and Wales from 1980 onwards. The species is confined to relict lowland fen areas, living in the edges of pools and slow running ditches in association with mud, wet moss and litter beneath rich, emergent vegetation. Landin (1980) indicated that this was a species in which flight had rarely been observed, and one that did not engage in flight in the spring. Threats Loss of rich fenland habitats in relict areas constitutes the main threat. Management and conservation L. aluta is largely confined to areas subject to statutory protection. No special management prescription is possible other than to warn against injudicious wholesale pond or ditch cleaning. Paracymus scutellaris Hydrophilidae Notable B (Nationally Scarce) P. scutellaris has a distribution of scattered clusters of sites along the south coast, the south-west and across Wales. Elsewhere records are even more thinly spread through Ireland and the north-west of Scotland. However one of those sites outside the main clusters is Hopton Fen to the west of Redgrave along the Little Ouse valley. There are no other records in the county database. Rhantus grapii Dytiscidae Notable B (IUCN status unclassified) R. grapii has been recorded in 35 counties, across 128 hectads since 1980, but it is still far from common. Its distribution follows old fenland in the south-west, the New Forest and across East Anglia with a scattered pattern of records elsewhere. A typical habitat is shallow pools amongst vegetation and dead leaves or mosses. The Suffolk database has only 12 other records dating from 1899 to 2004, the majority of these are centred on the Waveney and Little Ouse with Redgrave and Lopham Fens providing most of the recent finds. An important Suffolk species therefore which is locally rare in the county if not vulnerable. Scarodytes halensis Dytiscidae Notable B (Nationally Scarce) There are only 11, mostly imprecise, records for S. halensis in the Suffolk database all dated between 1855 and The nearest record to Redgrave is at Red Lodge from S. halensis has a habitat preference for base rich sparsely vegetated pools or ditches. The NBN lists 195 sites with the majority of them in an unusually U shaped cluster the two arms of which wrap around the Wash. There is some association with silty deposits on the substratum but this appears not to be particularly a fen species though obviously it is rare within Suffolk and this is a very useful new record. Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 24 of 33

25 Freshwater Bugs: Heteroptera Corixa dentipes Corixidae Local C. dentipes is one of a group of 5 lesser water boatmen which are somewhat larger than the rest of the Corixidae. It occurs in a wide range of still and slow flowing waters but generally in small numbers and often with the common C. punctata or even, as here at Redgrave with C. panzeri. Nationally it is widely but sparsely distributed hence its Local status. This is only the 4 th site in the Suffolk database for this species with the 3 previous records scattered across the county dating from1990 to In contrast C. punctata manages 106 records even though few people identify corixid bugs. Corixa panzeri Corixidae Local C. panzeri is also much less common than C. punctata and has a scattered distribution which slightly more concentrated in the Midlands and in parts of southern and eastern England. More common than C. dentipes it has 22 records in the Suffolk database spread across the county. It is able to utilise a wide range of habitats so long as the water is clear and neutral to alkaline, though it is unusual to find it in pools without extensive weed growth as here on Great Fen. The most likely scenario being a small population flying away and dispersing from the more established Redgrave wetland habitats. Hesperocorixa moesta Corixidae Notable B H. moesta is a very small corixid bug which nationally has a scattered, widespread distribution with records roughly south of a line from Liverpool to the Wash. Within that range there are slightly more records in the east but it is nowhere common. The NBN lists only 305 records with the greatest concentration to the north of London. Here in Suffolk we have only 9 other records, 4 of which are also from Redgrave & Lopham Fen; in 2001, 2002 and The other 5 records are from a few farm ponds, the Lark and the Stour. The last two are not typical of the habitat preference for this species which is for small ponds with neutral to alkaline water. The spider pools therefore make an ideal habitat extension for this rarely found Suffolk species. Notonecta viridis Notonectidae Local A southern species which seems to be extending its range northwards, N. viridis is much less often recorded than the common species N. glauca which is found throughout Britain. This is obviously an adaptable species as it was once described as being found chiefly in brackish pools. However in recent decades it has been found more and more in non-brackish locations even though it is still the species to expect in those habitats. At inland locations such as the Great Fen pools it is associated with non-organic silt bottomed waters. The Suffolk database contains 26 other locations for this species, being roughly a tenth of total Notonecta records. Suffolk Wildlife Trust / Boxvalley AquaSurveys Page 25 of 33