Saline Lagoon Survey, Benacre NNR and Suffolk Coast NNR, 2012 1

Ecological Surveys of Saline

Lagoons on the Benacre NNR

and Suffolk Coast NNR

February 2012.

An ecological survey including floral and fauna

observations undertaken for Natural England by

Abrehart Ecology. Defra License number:------

abrehart ecology Carried out by Toby R. Abrehart FLS Dr Simon J. Forster Pound Farm Low Road Great Glemham Suffolk IP17 2DQ Tel: 01728 663282 - 07798 941555

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C O N T E N T S

Page

Summary 4

1. Introduction and background 8

2. Materials and methods 9

2.1 The field survey and sample collection 9

2.2 Laboratory procedures and analyses 11

3. Site-by-site results 12

3.1 Benacre Pit 12

3.2 Benacre Broad 15

3.3 Covehithe Broad 26

3.4 Easton Broad 28

3.5 Reedland Marsh 30

4. General discussion 59

4.1 Benacre Pit 59

4.2 Benacre Broad 60

4.3 Covehithe Broad 62

4.4 Easton Broad 63

4.5 Reedland Marsh 64

5. Acknowledgements 65

6. References cited in text 65

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Appendices:

Appendix A Taxonomic list for the macrofaunal species recorded in the sweep net samples collected during the Suffolk saline lagoon survey, February 2012.

Appendix B Site-by-site results for the macrofaunal species recorded in the sweep net samples collected during the Suffolk saline lagoon survey, February 2012.

Appendix C Location figures and photographs of the lagoons and sampling sites assessed during the Suffolk saline lagoon survey, February 2012.

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Summary

Background

 Abrehart Ecology was requested by Natural England to undertake an ecological assessment survey of selected saline lagoons on the Suffolk coast. Previous studies had been undertaken in 1996 (Bamber, 1997) and 1998 (Bamber, 1999).

 The aim of the survey was to provide an update as to the ecological status of the selected lagoons and to provide Natural England with relevant data to enable informed managerial decisions to be made in the future.

 The survey was undertaken between 16 - 18 February 2012.

The findings

Benacre Pit

 Benacre Pit supported the most diverse and abundant aquatic plant and animal communities recorded in the lagoons that were assessed during the February 2012 survey.

 A range of archetypal lagoon species were documented included the protected species Nematostella vectensis (Starlet Sea Anemone) and Gammarus insensibilis (Lagoon Sand Shrimp).

 To determine the full ecological and conservational value of Benacre Pit, it is recommended that a detailed survey of the N. vectensis and G. insensibilis population as well as the aquatic plants is undertaken at a more appropriate time of year (for example late summer 2012).

 The principal threat to the Benacre Pit saline lagoon habitat appeared to be associated with the encroachment and/or breaching of the shingle embankment on the eastern (seaward) side of the site.

Benacre Broad

 To mitigate coastal erosion, a number of the small pools were created in 1996 to provide additional lagoon habitat. Prior to November 2011, Benacre Broad Lagoon had been a stable, near freshwater system for four years. In November

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2011 the shingle bank at the eastern end of Benacre Broad was over-topped and this, ostensibly freshwater, lagoon was filled with sea water.

 The 2011 inundation event caused the main broad to briefly become fully saline, this was then diluted with freshwater inputs from the sluices at the western end of the broad. The previously shallow “lagoon” pools had been submerged under deep water and in-filled with fine sediment for over four years.

 Within the main body of water, the floral and faunal assemblages were poor. The estuarine amphipod Corophium volutator had become dominant and was recorded at very high densities at a number of sites. Conversely, the low salinity amphipod, Corophium multisetosum, previously recorded by Bamber (1999), was not observed.

 No Nematostella vectensis was recorded. It is considered that the habitat within the eastern section of the main broad is no longer suitable for this species.

 The western-most sampling sites were separated from the main broad by a clay bund. At the time of sampling, the conditions at these sites were freshwater.

 In the freshwater site there was evidence of eutrophication of the water, including the presence of large quantities of the cyanobacteria (blue-green algae) Nostoc species.

 It appears that nutrient-rich run-off from farmland may cause the apparent eutrophication and that this may represent an immediate threat to the water quality, and hence the ecological value, of the Benacre Broad aquatic system.

Covehithe Broad

 Over recent years, Covehithe Broad has been reduced in size due to coastal erosion and the encroachment of sand and gravel. Evidence indicated this process was continuing. This is a significant threat to the lagoon habitat.

 The flora and fauna of Covehithe Broad was very poor. No previous data was available for the invertebrates’ communities. However, a demonstrable decline of the aquatic floral community had occurred over the past decade.

 There were indications that the water was eutrophic. It appeared that a potential source of nutrient-rich waters was surface run-off from the

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adjacent free-range pig farms. Further investigations to determine the current water quality status of Covehithe lagoon and the source and pathway of any nutrient-rich materials entering the water body is recommended.

Easton Broad

 Easton Broad was a low salinity lagoon system, at the time of the survey the salinity was 0 ‰.

 The extent of the water body had been reduced by sand encroachment. This process was continuing.

 The flora and fauna at Easton Broad was generally poor in terms of abundance and number of species. There was also evidence of eutrophication.

 The endangered (RDB 1) snail, Mercuria (=Pseudamnicola) confusa, was recorded from the edge of the Phragmites bed at the south-eastern end of the lagoon.

 The continued existence of M. confusa is threatened by (i) the continued encroachment of the sand and (ii) the potential for persistent salinity increases due to regular over-topping of the sand dune coastal embankment.

 It is recommended that targeted assessment of M. confusa and suitable habitats within the local area is undertaken to enable appropriate mitigation and/or habitat enhancement measures to be undertaken.

Reedland Marshes

 The Reedland Marshes lagoons continue to support a relatively wide range of lagoon and estuarine invertebrates. A very similar array of species was recorded during the previous survey of this area during 1998.

 The species of particular conservational importance was the scheduled species Nematostella vectensis and Gammarus insensibilis.

 The occurrence and abundance of the Starlet Sea Anemone, Nematostella vectensis, was significantly reduced at the time of the February 2012 survey compared to the results of the previous 1998 survey. However, it is likely that this was due to the time of year at which the surveys were undertaken.

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 The encroachment of the shingle embankment had reduced the number and area of saline lagoons. This was particularly apparent at the northern end of the Reedland Marshes survey area.

 It was noted that encroaching shingle provided a suitable substrata for coastal vegetated shingle, a Biodiversity Action Plan priority habitat.

 Evidence of tidal variations in the water depth within the lagoons in the mid- and southern sections of the Reedland Marsh survey area was noted. At the time of the survey a number of sites had up to 90% of the lagoon substrate exposed. It was suggested that tidal conditions would diminish the potential of the sites to support specialist lagoon floral and fauna species.

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1. Introduction and background

Abrehart Ecology was requested by Adam Burrows (Senior Reserves Manager, Suffolk Coast National Nature Reserves) of Natural England to undertake an ecological assessment survey of selected saline lagoons on the Suffolk coast. Previous studies had been undertaken in 1996 (Bamber, 1997) and 1998 (Bamber, 1999).

The saline lagoons of the Suffolk coast are, in the absence of expensive coastal defence measures, threatened by coastal erosion and the relentless encroachment of the sand and shingle into the marshland environment. In addition, inundation events, such as breaches in, and over-topping of, the coastal defence embankments and have caused dramatic, rapid changes in the physical conditions of coastal water bodies.

The objectives of the 2012 saline lagoon survey were:

 to provide an indication of the diversity and species structure of the invertebrate and plant communities that currently exist in the selected saline lagoons,

 to determine and document any changes in the conditions of the lagoon and their associated floral and faunal communities since the previous survey was undertaken,

 to provide baseline information against which (i) any future changes in the lagoon conditions could be compared and (ii) the success of any mitigation and/or habitat enhancement measure could be evaluated, and

 to provide Natural England with valuable information to enable informed decisions regarding the future management of the coastal lagoon systems to be made.

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2. Materials and methods

2.1 The field survey and sample collection

 The saline lagoon survey was undertaken by Abrehart Ecology between 16 - 18 February 2012. The surveyors were Toby Abrehart and Dr Simon Forster.

 Written descriptions of the each water body and habitat types were prepared and sketch maps were made to document the shape and general appearance of the lagoons and their associated habitats. Photographs of all sites were taken to further document the site conditions and to enable direct comparisons of the sampling sites during any subsequent monitoring surveys.

 A significant influencing factor on the community of invertebrates that colonise saline lagoons is the salinity of the water. Therefore, in order to aid the interpretation of the aquatic invertebrate results, measurements of the salinities at a selection of locations within each of the lagoons were assessed. This was achieved by using a hand-held ATC refractometer which provided salinity measurement as part per thousand (‰) within the range 0 ‰ to 100 ‰.

Note: It is appreciated that the salt content of the water in the water bodies can fluctuate throughout the season and the salinity measured at the time of the aquatic invertebrate sampling may not be representative of the salinity extremes to which the invertebrate communities may be exposed.

 The centre of each lagoon was determined using a hand-held GPS and recorded as a ten figure grid reference co-ordinate. GPS waypoints were also recorded at representative locations around the periphery of each water body to enable subsequent accurate assessment of the current area of each lagoon and to enable direct comparisons with past and future assessments.

 The vegetation of the habitat in the immediate vicinity of each water body was assessed and the main plant species identified. Wherever possible, the plant assemblages observed were classified in terms of their National Vegetation Classification (NVC) categories (Rodwell 1995, 1998a, 1998b, 1998c and 2000). In the majority of cases during botanical surveys, identical species composition criteria to given NVC community descriptions are not met. Where this occurs it is widely accepted that the most appropriate NVC category should be allocated, taking into account both the species present and their habitat requirements. This approach to NVC allocation was adopted for the present survey.

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Important note: It should be noted that, due to the time of year at which the survey was undertaken (February 2012), it was highly likely that there were established plants within these survey areas that were not visible during the site visits. Consequently, the present survey cannot be considered a comprehensive botanical survey of these sites. If detailed botanical information is required for these sites by Natural England, an appropriate survey should be undertaken during the optimum season.

 The presence of aquatic plants and their relative abundance within the water bodies was documented. At sites with deep water, a standard botanist’s grapnel was deployed to sample the submerged vegetation.

 Within each of the water bodies, representative sampling sites were selected for the assessment of the macro invertebrate communities. At each sampling site a single invertebrate sample was collected using a standard International Standards Organisation (ISO) “ecologist’s” hand-net. A “figure-of-eight” sweep technique was employed for a total of two minutes per site. All materials retained in the net were transferred to 5 litre, sealable plastic sample buckets and returned to the laboratory for subsequent processing.

 Where aquatic plants occurred, samples were collected to enable the assessment of the invertebrate assemblages associated with submerged vegetation. These samples were transferred to 5 litre, sealable plastic sample buckets and returned to the laboratory for subsequent processing.

 A single 150 ml sediment sample was collected in a Nalgene sample pot for subsequent meiofauna analysis1, if required. The samples were fixed in formaldehyde (final concentration 5 - 7%) and returned to the Abrehart Ecology laboratory for storage. These samples will be available for analyses if required.

1 Meiofauna are the small, highly abundant invertebrate animals, typically ranging between 0.1mm and 1 mm in size, that live in the sediments of aquatic systems. Due to their high diversity, abundance and extreme range of sensitivities, meiofauna communities are particularly valuable biosensors (bioindicators) for changes in environmental conditions and can be used to monitor environmental recovery following pollution incidents as well to document ecological changes associated with natural events (see Trett et al. 2009).

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2.2 Laboratory procedures and analyses

2.2.1 Invertebrate sweep net and vegetation sample analyses

All invertebrates were separated from the retained sediment, detritus and vegetation under 40 - 80x stereo, binocular microscopes. These were then further separated into the major taxonomic groups, preserved in alcohol (70% IMS) and referred to the appropriate taxonomist for identification.

Where possible, all specimens were identified to species level. Exceptions to this were groups that require specialist, time-consuming preparatory techniques such as head capsule dissection for chironomid larvae and prolonged clearing procedures for oligochaetes species. Such procedures were beyond the remit of the present study. In these cases, specimens were allocated to observed taxonomic units (OTUs).

Given that (i) the objectives of the survey were to characterise the invertebrate community of the aquatic habitats and not undertake an extensive, fully quantitative survey and (ii) the sampling methods appropriate to sampling still-water habitats are considered semi-quantitative, directly comparable quantitative units (e.g. number per metre2) could not be used to provide rigorous quantitative descriptions of invertebrate abundance. Consequently, the data for the invertebrate taxa and assemblages are presented as “numbers per species per sample”.

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3. Site-by-site results

The following sections describe the physical and biological conditions that were recorded at each of the water bodies surveyed. A full, combined taxonomic species list of the plants, macro invertebrates and fish recorded in the surveys is presented in Appendix A. A combined site-by-site results table is presented in Appendix B.

Throughout this section, reference should be made to the site location figures and the photographs presented in Appendix C. For each water body, an aerial view of the site is presented with a red line boundary indicating of the edge of the water body as at the date of the survey (between 16 - 18 February 2012). Representative photographs of each site are also presented.

3.1 Benacre Pit

SITE NAME: Benacre Pit LOCATION: Benacre, Suffolk GRID REFERNCE: TM 53503 84160 TYPE/CLASSIFICATION: Percolation DESIGNATION: SSSI, NNR, SAC, and SPA AREA: 1.12 hectares MAX DEPTH (m): 1.0 SALINITY (‰): 29-31 ‰ ADJACENT HABITATS: SM18 Juncus maritima, S21 Bolboscheonus maritima, S4 Phragmites australis, and SD6 mobile dune communities. SURVEY DATE: 17 February 2012

LAGOON DESCRIPTION:

Benacre Pit was created during the Second World War by the extraction of gravel that was used to construct nearby runways. There were originally four ‘pits’ here, although only one now survives. The remaining Benacre Pit is a narrow water body extending from north to south being approximately 55m wide and 240m long. It was separated from the North Sea by a sand and gravel embankment. Until 1989, Benacre Pit was an isolated water body and was not affected by seawater overtopping the embankment. However, during 1989 the embankment was overtopped for the first time. The embankment was overtopped again in 1997 and since 2006, this has occurred annually. The sand embankment protecting the lagoon is currently very narrow. Adjacent to the centre of the lagoon, the embankment has been breached and, at the time of the 2012 survey, a “tongue” of gravel extended into the lagoon from the eastern side (see Figure C1.1 and Photograph C1.1).

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The substrate within Benacre Pit varied markedly throughout the lagoon. Mud over gravel predominated at the north-eastern side with fine mud with plant detritus at the north-west. The south-eastern section of the lagoon was shingle while sand substrate occurred at the south-western side. The salinity of Benacre Pit was slightly below full marine, ranging between 29 ‰ and 31 ‰.

There was a rich aquatic flora at this lagoon with Myriophyllum, Ruppia, Chaetomorpha, Cladophora and Enteromorpha being recorded. The most abundant stands of aquatic vegetation occurred on the western side of the lagoon.

The fauna recorded within Benacre Pit comprised a classic saline lagoon assemblage of species. High densities of Nematostella vectensis and Corophium insidiosum were present. Other archetypal lagoon species recorded included Idotea chelipes, Gammarus insensibilis, Hydrobia neglecta and Cerastoderma glaucum.

Species present:-

Aquatic Plants Other Observations

Myriophyllum Most abundant on western Ruppia side Chaetomorpha Cladophora Enteromorpha

Invertebrates 1 2 3 i Veg

Nematostella vectensis 41 9 6 93 Nemertean indet. 8 12 7 Oligochaeta species 8 19 35 Common on east and south Arenicola marina 1 sides Pygospio elegans 1 1 Cirratulid 9 4 11 Idotea chelipes 2 5 6 2 Corophium insidiosum 386 391 263 68 Corophium volutator 4 Gammarus insensibilis 1 Chironomid larva 2 1 1 Retusa obtusa 2 Hydrobia neglecta 1 Mytilus edule Observed on eastern side

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Mya arenaria 1 Cerastoderma glaucum 1 2 Numerous shells observed

Gasterosteus aculeatus 1 Pomatoschistus microps 1

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3.2 Benacre Broad

SITE NAME: Benacre Broad 1 LOCATION: Benacre, Suffolk GRID REFERNCE: TM 52400 83124 TYPE/CLASSIFICATION: Isolated DESIGNATION: SSSI, NNR, SAC, and SPA AREA: N/A MAX DEPTH (m): 1.3 SALINITY (‰): 0 ‰ ADJACENT HABITATS: S4 Phragmites australis reedbeds. SURVEY DATE: 17 February 2012

LAGOON DESCRIPTION:

This pool, previously referred to as the “Bay of Biscay“, was separated from the main lagoon by a clay bund (see Figure C2.1). It was an area of essentially fresh water with extensive peripheral stands of Phragmites australis swamps (see photograph C2.1). The broad bed at this location comprised soft mud and vegetation debris over a firmer substrate. The freshwater input into this section of Benacre Broad emanates from drains running in from adjacent farmland to the west. There is no sluice in the clay bund that connects this section broad with the main lagoon.

At the time of the survey, the salinity at the sampling site was 0 ‰. However, given the array of invertebrate species recorded here, it is likely that this site is subject to slight temporal salinity variations; see below.

Apart from the peripheral Phragmites beds, no aquatic plants were recorded at this location.

A limited range of invertebrates were documented at this site. Despite the recorded freshwater conditions at the time of the survey, all of the invertebrates, with the possible exception of Callicorixa praeusta, are characteristic brackish water species. This observation indicates that this water body is subjected to periodic fluctuations in salinity that prevents a typical freshwater assemblage of invertebrates to establish. Callicorixa praeusta is an alate water boatman that is known to occur in brackish, as well as fresh, water.

Bamber (1999) also recorded brackish water species from this location during the September 1998 survey. At that time the salinity was reported as 2 ‰. Bamber also recorded the low salinity/freshwater amphipod, Corophium multisetosum, from this site. This species was not recorded during the 2012 survey. Instead, the brackish water species Corophium volutator, occurred.

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Species present:-

Aquatic Pants Other Observations

None observed

Invertebrates

Lekanosphaera rugicauda 5 Corophium volutator 3 Gammarus deubeni 6 Callicorixa praeusta 1 Hydrobia neglecta 23

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SITE NAME: Benacre Broad 2 and 3 LOCATION: Benacre, Suffolk GRID REFERNCE: Site 2 - TM 52426 83128 Site 3 - TM 52434 83023 TYPE/CLASSIFICATION: Inundated, via percolation DESIGNATION: SSSI, NNR, SAC, and SPA AREA: N/A MAX DEPTH (m): 0.5 SALINITY (‰): 22 ‰ ADJACENT HABITATS: Open water, with some S4 Reedbeds to the north and south. SURVEY DATE: 17 February 2012

LAGOON DESCRIPTION:

Sites 2 and 3 were originally a pair of interlinked small lagoons (see Bamber, 1999) which, since the natural sealing of the breach in March 2009, has become part of the main Benacre Broad lagoon (see photograph C2.2 and C2.3). The original lagoon features were discernible by an area of deeper soft muds as opposed to the shallow layer of soft mud adjacent to former lagoons.

The substrate at both sites comprised a deep layer of detritus-rich mud. The salinity was a uniform 22 ‰.

No submerged plants were found at site 2 but smaller quantities of Cladophora and very occasional Enteromorpha were recorded at Site 3

The invertebrate fauna comprised a range of brackish water species. Corophium volutator occurred at very high densities at site 2.

Species present:-

Aquatic Plants Other Observations

Cladophora Occasional at site 3 Enteromorpha Rare at site 3

Invertebrates 2 3 Neomysis integer 30 49 Lekanosphaera rugicauda 5 Corophium volutator 315 20 Gammarus zaddachi 40 17 Chironomid larva 105 36 Hydrobia neglecta 5

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SITE NAME: Benacre Broad 4 LOCATION: Benacre, Suffolk GRID REFERNCE: TM 52542 82860 TYPE/CLASSIFICATION: Inundated, via percolation DESIGNATION: SSSI, NNR, SAC, and SPA AREA: N/A MAX DEPTH (m): 0.6 SALINITY (‰): 22 ‰ ADJACENT HABITATS: S4 Phragmites australis swamp to the south. SURVEY DATE: 17 February 2012

LAGOON DESCRIPTION:

Site 4 was originally a small, low salinity (10 ‰) lagoon (see Bamber, 1999) which, since the natural sealing of the breach in March 2007, has become part of the main Benacre Broad lagoon. The original lagoon features were discernible by an area of deeper soft muds as opposed to the shallow layer of soft mud adjacent to former lagoons (see Photograph C2.4).

The substrate at the site comprised a deep layer of detritus-rich mud. The salinity was a uniform 22‰.

No submerged plants were found at this location.

Corophium volutator occurred at very high densities with Gammarus zaddachi and chironomid larvae also documented.

During the 1998 survey, Bamber recorded the scheduled Starlet Anemone, Nematostella vectensis. The conditions documented during the 2012 survey were no longer suitable for this shallow lagoon species and, consequently none were recorded.

Species present:-

Aquatic Plants Other Observations

None observed

Invertebrates

Corophium volutator 100 Gammarus zaddachi 2 Chironomid larva 52

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SITE NAME: Benacre Broad 5 LOCATION: Benacre, Suffolk GRID REFERNCE: TM 52363 82924 TYPE/CLASSIFICATION: Inundated, via percolation DESIGNATION: SSSI, NNR, SAC, and SPA AREA: N/A MAX DEPTH (m): 1.0 SALINITY (‰): 19 ‰ ADJACENT HABITATS: S4 Phragmites australis swamp. SURVEY DATE: 17 February 2012

LAGOON DESCRIPTION:

Site 5 was a narrow pool, described by Bamber (1999) as “more a wide ditch” at the western margin if the main Benacre Lagoon (see Photograph C2.5). At the time of the 2012 survey this section was confluent with the main Benacre lagoon.

The substrate was deep, detritus-rich sediment with large quantities of reed frass. The salinity here was slightly lower than that of the main Benacre lagoon, being 19 ‰ as opposed to 22 ‰ of the main water body.

Bamber (1999) reported extensive Ruppia at site 5, however, during the February 2012 survey, no aquatic macrophytes were recorded. Bamber also reported that this site was used for an experimental introduction of Chara prior to the 1998 survey. There was no evidence of this plant during the 2012 survey.

The fauna community comprised a poor range of brackish water species at low abundance.

Species present:-

Aquatic Plants Other Observations

None observed

Invertebrates

Oligochaeta species 2 Neomysis integer 2 Gammarus zaddachi 4 Chironomid larva 6

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SITE NAME: Benacre Broad 6 LOCATION: Benacre, Suffolk GRID REFERNCE: TM 52384 82845 TYPE/CLASSIFICATION: Inundated, via percolation DESIGNATION: SSSI, NNR, SAC, and SPA AREA: N/A MAX DEPTH (m): 0.5 SALINITY (‰): 22 ‰ ADJACENT HABITATS: S4 Phragmites australis swamp with small areas of SM18 Juncus maritima. SURVEY DATE: 17 February 2012

LAGOON DESCRIPTION:

Site 6 was originally an isolated, open, shallow pool (see Bamber, 1999) which, since the natural sealing of the breach in March 2007, has become part of the main Benacre Broad lagoon. The original lagoon features were discernible by an area of deeper soft muds as opposed to the shallow layer of soft mud adjacent to former lagoon (see Photograph C2.6).

The substrate at the site comprised a deep layer of detritus-rich mud. The salinity was a uniform 22 ‰.

No aquatic macrophytes were recorded at this site.

As reported for the previous sites within the main Benacre lagoon, the invertebrate fauna was represented by a poor range of brackish water species. Corophium volutator was present at reasonable densities.

Species present:-

Aquatic Plants Other Observations

None observed

Invertebrates

Neomysis integer 1 Corophium volutator 31 Gammarus zaddachi 3 Chironomid larva 39 Potamopyrgus antipodarum 2

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SITE NAME: Benacre Broad 7 LOCATION: Benacre, Suffolk GRID REFERNCE: TM 52306 82732 TYPE/CLASSIFICATION: Inundated, via percolation DESIGNATION: SSSI, NNR, SAC, and SPA AREA: 0.294 hectares MAX DEPTH (m): 0.2 SALINITY (‰): 18 ‰ ADJACENT HABITATS: S4 Phragmites australis swamp. SURVEY DATE: 17 February 2012

LAGOON DESCRIPTION:

Site 7 was located at the south-western corner of the main Benacre lagoon (see Figure C2.1). Bamber (1999) described this site as “a ditch draining down to the main lagoon, with freshwater input from pool 8 (see below)”. He reported the salinity ranging from 11 ‰ to 16 ‰. Since the natural sealing of the breach in March 2007, this area has become part of the main Benacre Broad lagoon (see Photograph C2.7). The substrate was characterised by deep, detritus-rich sediment over an apparent flat, uniform substrate.

The freshwater input from the adjacent Site 8 (see below) caused the salinity to be slightly depressed from that of the rest of the main lagoon with a measurement of 18 ‰.

No aquatic plants were found and the invertebrate fauna was consistent with that of other detritus-rich sites within the main lagoon. Chironomid larvae were the dominant taxa at this site.

Species present:-

Aquatic Plants Other Observations

None observed

Invertebrates 7 Neomysis integer 6 Lekanosphaera rugicauda 8 Corophium volutator 8 Gammarus zaddachi 6 Chironomid larva 50 Potamopyrgus antipodarum 4

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SITE NAME: Benacre Broad 8 LOCATION: Benacre, Suffolk GRID REFERNCE: TM 52269 82733 TYPE/CLASSIFICATION: Inundated, via percolation DESIGNATION: SSSI, NNR, SAC, and SPA AREA: 0.23 hectares MAX DEPTH (m): 1.5 SALINITY (‰): 0 ‰ ADJACENT HABITATS: S4 Phragmites australis swamp. SURVEY DATE: 17 February 2012

LAGOON DESCRIPTION:

Site 8 was located at the south-western edge of the Benacre Broad survey area. It was separated from Site 7 by an apparently impermeable clay bund (see Figure C2.1). The site comprised an area of freshwater reedbed and marshes, with an area of deep (c. 1.5 m) open water fringed with Phragmites australis, Typha latifolia and Bolboscheonus maritima (see Photograph C2.8). The substrate consisted of a deep layer of plant detritus and reed frass.

The salinity of this water body was 0‰ and, it is understood that it is fed by streams and run-off channels from the surrounding farmland to the south and west from.

No aquatic macrophytes were found at Site 8. However, the invertebrate sweep net sample collected large quantities of the cyanobacteria (blue-green algae) Nostoc species. This forms large “globules” on the substrate and is indicative of eutrophic conditions.

The invertebrate fauna demonstrated that this site had maintained freshwater conditions persistently prior to the survey. Whilst species such as Helobdella stagnalis, Callicorixa praeusta and Sigara dorsalis can tolerate low salinities, Gammarus lacustris, Acroloxus lacustris and Gyraulus crista are ostensibly freshwater species.

The single Gammarus specimen found in the sweep net sample conformed to G. lacustris. This species is more commonly found in the north of England and Scotland. However, it has been found in southern England in places such as a ditch in Rye Harbour Nature Reserve and ponds at Woodchurch in Kent (see Gledhill et al., 1993).

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Species present:-

Aquatic Plants Other Observations

None observed Large quantities of Nostoc

Invertebrates 5

Helobdella stagnalis 1 Asellus aquaticus 2 Gammarus lacustris 1 Chironomid larva 20 Callicorixa praeusta 2 Sigara dorsalis 2 Acroloxus lacustris 2 Gyraulus crista 1

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SITE NAME: Benacre Broad 9, 10 and 11 LOCATION: Benacre, Suffolk GRID REFERNCE: 9 - TM 52729 83054 10 - TM 52761 82967 11 - TM 52799 82750 TYPE/CLASSIFICATION: Inundated, via percolation DESIGNATION: SSSI, NNR, SAC, and SPA AREA: N/A MAX DEPTH (m): 0.5 SALINITY (‰): 22 ‰ ADJACENT HABITATS: Open water with S4 Phragmites australis swamp to the north and south. SURVEY DATE: 17 February 2012

LAGOON DESCRIPTION:

Benacre Broad sampling site 9, 10 and 11 were representative locations across the centre of the current Benacre Broad lagoon. These do not correspond with any of the sampling sites used in the previous 1998 survey (Bamber, 1999). The substrate here was soft mud overlying hard clay substrate. As with most of the sites within the main lagoon, the salinity was a constant 22 ‰ at each of these locations.

The invertebrate fauna sites 9 and 10 were dominated by the estuarine amphipod, C. volutator. This species occurred at very high densities at site 10, at the centre of the main lagoon.

Site 11, on the southern edge of the main lagoon revealed 7 invertebrate taxa. Amongst these was the bryozoan Conopeum seurati. This species is the most common encrusting bryozoan in the northwest European lagoons and can tolerate salinities down to 1 ‰ (Barnes, 1994). It is likely that the colony that occurred in the invertebrate sample from Benacre Broad site 11 had become detached from the stems of the adjacent Phragmites australis.

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Species present:-

Aquatic Plants Other Observation

None observed

Invertebrates 9 10 11

Nereis diversicolor 1 Neomysis integer 6 40 7 Corophium volutator 53 345 26 Gammarus zaddachi 5 1 Chironomid larva 5 65 57 Hydrobia neglecta 2 Conopeum seurati 1

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3.3 Covehithe Broad

SITE NAME: Covehithe Broad LOCATION: Covehithe, Suffolk GRID REFERNCE: TM 52250 80968 TYPE/CLASSIFICATION: Percolation DESIGNATION: SSSI, NNR, SAC, and SPA AREA: 4.1607 hectares MAX DEPTH (m): 1.0 SALINITY (‰): 18-19 ‰ ADJACENT HABITATS: S4 Phragmites australis, bare shingle, some SM18 Juncus maritima with small areas of SM 13 Puccinellia maritima salt-marsh and SD6 mobile dunes. SURVEY DATE: 17 February 2012

LAGOON DESCRIPTION:

It is understood that this lagoon was created originally by a shallow valley being blocked by glacial moraine which formed a shingle ridge at the river outflow (see Figure C3.1). The lagoon has shrunk considerably in recent years. At the time of the survey, it was apparent that the sand dunes of the foreshore were encroaching upon the open water as there was a large amount of loose, unconsolidated sand at the eastern (seaward) side of the lagoon (see Photograph C3.2). The substrate at the southern and northern edges comprised a layer of fine, detritus-rich silt overlying a firm sand substrate (see Photograph C3.1). The salinity of the water was constant throughout the areas of the lagoon that were accessible from the eastern bank, being 18 ‰ to 19 ‰.

Very few aquatic macrophytes were observed. Ulva lactuca was rare across the site and fine brown algae mat, associated with eutrophic systems, was present.

The invertebrate fauna recorded within Covehithe lagoon was very poor. The sweep net samples from Site 1, at the south-eastern edge of the water body, contained only a single specimen of the mysid “shrimp”, Neomysis integer. The sample from Site 2, from the north-eastern section was little better. This contained N. integer, two oligochaetes worms, a beetle larva and a fragment of the bryozoan, Flustra foliacea. It is likely that the latter species was imported into the lagoon from the adjacent coastal waters as it generally occurs in active, sand-scoured marine habitats.

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Species present:-

Aquatic Plants Other Observations

Ulva lactuca Sporadic clumps noted - rare

Invertebrates 1 2

Oligochaeta species 2 Neomysis integer 1 21 Coleopteran larva indet. 1 Flustra foliacea 1

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3.4 Easton Broad

SITE NAME: Easton Broad LOCATION: Easton, Suffolk GRID REFERNCE: TM 51662 79345 TYPE/CLASSIFICATION: Percolation DESIGNATION: SSSI, NNR, SAC, and SPA AREA: 0.442hectares MAX DEPTH (m): 1.5 SALINITY (‰): 0 ‰ ADJACENT HABITATS: S4 Phragmites australis reedbeds and SD6 young mobile sand dunes. SURVEY DATE: 17 February 2012

LAGOON DESCRIPTION:

As described above for Covehithe lagoon, Easton Broad has shrunk considerably in recent years. This is demonstrated vividly by comparing the red line boundary of the lagoon edge as determined on 17th February 2012 with the water’s edge of the aerial image taken previously (see Figure C4.1). It was evident that the encroachment of the sand dunes was continuing and “young” mobile sand dunes of the foreshore were steadily encroaching upon the open water areas at the eastern edge of this lagoon (see Photograph C4.1).

The substrate of the area of lagoon accessible from the shore was largely sand. In the vicinity of the Phragmites beds layers of plant detritus occurred. At the time of the survey, the water was ostensibly fresh (0 ‰).

No true aquatic macrophytes were observed during the survey although a brown algal/diatom mat was observed on the sand in the shallow water at the northern end of the lagoon in the vicinity of Site 2 (see Figure C4.1). Such occurrences can indicate nutrient-rich (eutrophic) conditions.

The invertebrate fauna comprised a limited range of low salinity/brackish water species. Of considerable interest was the occurrence of the endangered (RDB 1) snail, Mercuria (=Pseudamnicola) confusa. This was recorded in the sweep sample from Site 1, collected from the edge of the Phragmites bed at the south-eastern end of the lagoon (see Photograph C4.1).

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Species present:-

Aquatic Plants Other Observations

None observed

Invertebrates 1 2

Oligochaeta species 19 Neomysis integer 4 Lekanosphaera rugicauda 1 14 Gammarus zaddachi 1 4 Gammarus deubeni 1 2 Chironomid larva 2 Dolichopodid larva 1 Tipulid larva 1 Bithynia tentaculata 1 Mercuria confusa 12 Radix (=Lymnaea) peregra 1

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3.5 Reedland Marshes

SITE NAME: Reedland Marshes Lagoon 1a, 1b and 1c LOCATION: Dunwich Suffolk GRID REFERNCE: 1a - TM 48769 73105 1b – TM 48711 73004 1c – N/A TYPE/CLASSIFICATION: Tidal Percolation DESIGNATION: SSSI, NNR, SAC, Ramsar and SPA AREA: 1a - 0.646 hectares 1b - 0.04 hectares 1c – N/A MAX DEPTH (m): 0.5 SALINITY (‰): 31 -32 ‰ ADJACENT HABITATS: Small remnants of SM10 Transitional low salt-marsh with areas of SM8 Annual Salicornia salt-marsh and SM14 Halimione portulacoides salt-marsh in the east with S4 Phragmites australis reedbeds small stands of SM6 Spartina anglica, SM28 Elytrigia repens salt and S21 Bolboscheonus maritima in the west. SURVEY DATE: 16 February 2012

LAGOON DESCRIPTION:-

Bamber (1999) described Site 1 as a group of three similar lagoons, each being less than 1 ha. Between 1998 and the present survey (February 2012) the water bodies have changed considerably in shape and expanse. The former lagoons 1a and 1b (Bamber, 1998) had merged to form a single water body, referred to as 1a in this report (see Figure C5.2). The former lagoon 1c has been covered by the ingression of shingle and no longer exists. A small triangular section of lagoon was present adjacent to, but separate from, lagoon 1a, and has been labelled 1b (see Figure C5.2 and Photograph C5.3).

The substrate at both 1a and 1b were soft mud over shingle. Both pools were connected directly to the river via narrow channels. The water level within the lagoons was maintained by percolation through the shingle embankment. The percolation occurred during high tides during which time the lagoon water overflowed into the Dunwich River via the connecting channels. It is likely that water flows from the river into the lagoon only during periods of high precipitation when river levels are elevated.

As a result of the regular percolation, the salinities within these two lagoons varied little and were close to full marine levels (average 31.5 ‰).

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Within lagoon 1a there were limited amounts of Ruppia, with Ulva, Enteromorpha and Chaetomorpha algae was also present.

Large areas of shingle incursion on the eastern side of the site supported established shingle flora (see Photograph C5.1). This indicated that the shingle had been stable for over two years.

The fauna of the water bodies were dominated by oligochaetes worms. Also present in reasonable numbers was Hydrobia neglecta occurring in both the sweep samples and the vegetation sample. A number of specimens of the small Littorinid, Lacuma parva were also found amongst the vegetation. The Starlet Anemone, Nematostella vectensis was observed in low densities during the field-based habitat search but did not occur in the sweep samples.

In contrast to the findings of Bamber (1999), an established colony of Lugworm, Arenicola marina, was present at the eastern (seaward) edge of lagoon 1a. This species was not recorded during the previous, 1998, survey. Conversely, neither Nereis diversicolor nor Corophium volutator were recorded during the present survey. These were recorded as abundant and/or super abundant by Bamber (1999).

Species present:-

Aquatic Plants Other Observations

Ruppia maritima Enteromorpha intestinalis Ulva lactuca Chaetomorpha

Invertebrates 1a Veg 1b

Nematostella vectensis 3 specimens observed in 1a Nemertean indet. 7 2 8 Oligochaeta species 1200 360 Abundant at southern edge of Arenicola marina 1a Praunus flexuosus 3 6 Idotea chelipes 3 Chironomid larva 2 11 Hydrobia neglecta 16 8 13 Hydrobia ulvae 1 Hydrobia ventrosa 2 4

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Lacuma parva 7 Littorinid ?Littorina neglecta 2 Abra tenuis 2 Pomatoschistus microps 1

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SITE NAME: Reedland Marshes Lagoon 2 LOCATION: Dunwich Suffolk GRID REFERNCE: TM 48695 72906 TYPE/CLASSIFICATION: N/A DESIGNATION: SSSI, NNR, SAC, Ramsar and SPA AREA: 0.0 hectares MAX DEPTH (m): 0.0 SALINITY (‰): N/A ADJACENT HABITATS: N/A SURVEY DATE: 16 February 2012

LAGOON DESCRIPTION:

At the time of the February 2012 survey, the lagoon referred to as Lagoon 2 by Bamber (1999) did not exist. This section of marsh had been covered by a large volume of shingle that extended from the shingle embankment on the eastern (seaward) side to the Dunwich river channel on the west and approximately 120 m north to south.

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SITE NAME: Reedland Marshes Lagoon 3 LOCATION: Dunwich Suffolk GRID REFERNCE: TM 48663 72829 TYPE/CLASSIFICATION: Tidal Percolation DESIGNATION: SSSI, NNR, SAC, Ramsar and SPA AREA: 0.248 hectares MAX DEPTH (m): 0.3 SALINITY (‰): 30-32.5 ‰ ADJACENT HABITATS: SM14 Halimione portulacoides salt-marsh in the north with stunted S4 Phragmites australis reedbeds and SM28 Elytrigia repens salt-marsh community on the higher land at the west. Small areas of SM10 Transitional low salt-marsh were to the north and south of the lagoon. SURVEY DATE: 16 February 2012

LAGOON DESCRIPTION:

Lagoon 3 is an open, shallow water body. The shingle encroachment has greatly reduced the size of this lagoon since Bamber undertook the 1998 survey (see Figure C5.3). Several shingle advances have taken place here creating resulting in a shingle substrate with overlying mud. At the time of the survey, there was abundant plant debris along the northern edge as a result of the recent flooding (see Photograph C5.3).

Since the previous Bamber 1998 survey, a direct connection between the lagoon and the adjacent river channel has established. The salinity within the lagoon ranged between 30 and 32.5 ‰. Previously hyperhaline conditions had been recorded here (36 ‰; Bamber, 1998). The apparent reduction in salinity may be due to the connection between the river and the lagoon that had occurred between the surveys.

During the survey, no aquatic plants were observed. A reasonable range of archetypal lagoon invertebrate species were recorded including Hydrobia ventrosa, H. neglecta, Abra tenuis and Cerastoderma glaucum. No Nematostella vectensis were observed during the habitat search; however, low densities were recorded in the sweep net sample. The abundant shell debris around this lagoon indicated that it was exploited extensively by feeding birds.

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Species present:-

Aquatic Plants Other Observations

None observed

Invertebrates

Nematostella vectensis 5 Nemertean indet. 16 Oligochaeta species 63 Arenicola marina Frequent Praunus flexuosus 2 Chironomid larva 34 Retusa obtusa 6 Hydrobia neglecta 64 Hydrobia ventrosa 9 Littorinid ?Littorina neglecta 1 Abra tenuis 70 Empty shells abundant Cerastoderma glaucum 3 Empty shells occasional

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SITE NAME: Reedland Marshes Lagoon 4 LOCATION: Dunwich Suffolk GRID REFERNCE: TM 48593 72752 TYPE/CLASSIFICATION: Tidal Percolation DESIGNATION: SSSI, NNR, SAC, Ramsar and SPA AREA: 0.1152 hectares MAX DEPTH (m): 0.2 SALINITY (‰): 10-30 ‰ ADJACENT HABITATS: SM14 Halimione portulacoides salt-marsh was dominant to the west of the lagoon with smaller areas of SM28 Elytrigia repens salt-marsh community on the higher land adjacent to the Dunwich River. SM10 Transitional low salt-marsh was to the south of the lagoon. SURVEY DATE: 16 February 2012

LAGOON DESCRIPTION:

The lagoon is connected to the Dunwich River by a wide channel (see Figure C5.4). The substrate was heterogeneous, with encroaching shingle occurring at the eastern side (see Photograph C5.4), sand at the main percolation flows into the lagoon and sandy-mud throughout the western side of the lagoon. At the time of the survey, there was visible percolation through most of the shingle. It is probable that the percolation rate varied with the tide.

The salinities across the lagoon varied considerably. The highest salinity of 31 ‰ occurred at the eastern (seaward) side near the main percolation points. A very localised pocket of reduced salinity (10 ‰) was recorded on the southern side while the overflow into the river was recorded as 28.5 ‰. From one small area that had a salinity of 10‰ (here there was considerable percolation through the shingle) to the rest of the site having salinities close to that of the North Sea.

The algae Enteromorpha and Chaetomorpha were sparse around the lagoon, open water was across most of the lagoon with smaller areas of tidal habitats. With the exception of the abundant Arenicola marina mounds, the invertebrate fauna was relatively poor within lagoon 4. Oligochaetes dominated the invertebrate community with the remaining fauna comprising low densities of Hydrobia neglecta, chironomid larvae, spionids and nemerteans.

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Species present:-

Aquatic Plants Other Observations

Enteromorpha intestinalis Chaetomorpha Brown algae

Invertebrates

Nemertean indet. 2 Oligochaeta species 175 Arenicola marina Common throughout site Pygospio elegans 3 Chironomid larva 2 Hydrobia neglecta 7 Cerastoderma glaucum Shell debris abundant

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SITE NAME: Reedland Marshes Lagoon 5 LOCATION: Dunwich Suffolk GRID REFERNCE: TM 48535 72655 TYPE/CLASSIFICATION: Tidal Percolation DESIGNATION: SSSI, NNR, SAC, Ramsar and SPA AREA: 0.4212 hectares MAX DEPTH (m): 0.2 SALINITY (‰): 30 – 34 ‰ ADJACENT HABITATS: Large areas of SM14 Halimione portulacoides salt-marsh were present to the south and west, with SM8 Annual Salicornia salt-marsh in the centre and east. With SM6 Spartina anglica and S4 Phragmites australis to the north and west of the lagoon. In the foreshore shingle were SD1 Rumex crispus-Glaucium flavum and SD2 Honkenya peploides shingle communities. SURVEY DATE: 16 February 2012

LAGOON DESCRIPTION:- As observed at all the previous sites, lagoon 5 displayed evidence of constriction due to the encroachment of shingle (see Figure C5.5 and Photograph C5.5). Throughout the water body the water was shallow (c. 0.2 m). With the exception of the encroaching shingle at the eastern edge, the substrate ranged from fine mud at the northern end to sandy mud at the southern edge. The salinity ranged from 30 to 34 ‰ with the highest salinity being at the south-western corner of the lagoon.

Salinities varied across the site with a substrate of shingle on the east of the lagoon with the rest of the site having sandy-mud.

There was a sparse algae flora with small areas of Chaetomorpha, Cladophora and Ulva lactuca. In the deeper water limited stands of Enteromorpha intestinalis occurred. Evidence of numerous Arenicola marina was observed during the fieldwork and the sweep samples revealed high mollusc densities. Hydrobia neglecta were most abundant with H. ventrosa, Abra tenuis and Cerastoderma glaucum also present. The opisthobranch mollusc, Retusa elongata, also occurred in the aquatic vegetation sample whilst Macoma balthica shells were observed on the lagoon bank. A single Nematostella vectensis was recorded in the sweep sample but none was observed during the habitat search.

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Species present:-

Aquatic Plants Other Observations

Chaetomorpha sp. Cladophora sp. Ulva lactuca Enteromorpha intestinalis

Invertebrates 5 i 5 veg

Nematostella vectensis 1 Nemertean indet. 8 Oligochaeta species 8 23 Arenicola marina Common within the site Praunus flexuosus 5 Crangon crangon 1 Corophium volutator 1 Chironomid larva 6 12 Ephydrid larva 1 Retusa elongata 6 Hydrobia neglecta 590 6 Hydrobia ventrosa 30 Abra tenuis 19 8 Empty shells observed Macoma balthica Empty shells observed Cerastoderma glaucum 1 Empty shells observed

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SITE NAME: Reedland Marshes Lagoon 6 LOCATION: Dunwich Suffolk GRID REFERNCE: TM 48450 72559 TYPE/CLASSIFICATION: Tidal Percolation DESIGNATION: SSSI, NNR, SAC, Ramsar and SPA AREA: 6a - 0.2662 hectares 6b 0.0798 hectares MAX DEPTH (m): 6a - 0.2 6b – 0.15 SALINITY (‰): 6a - 6-13 ‰ 6b - 30-31 ‰ ADJACENT HABITATS: Large areas of SM14 Halimione portulacoides salt-marsh were present across these lagoons, with smaller areas of SM8 Annual Salicornia salt-marsh, SM6 Spartina anglica. Stunted S4 Phragmites australis was to the north and west of the lagoon. Smaller areas of SM28 Elytrigia repens salt- marsh community were on the higher ridges and adjacent to the Dunwich River. In the foreshore were SD1 Rumex crispus-Glaucium flavum and SD2 Honkenya peploides shingle communities. SURVEY DATE: 16 February 2012

LAGOON DESCRIPTION:

Lagoon 6 comprised a pair of adjacent tidal lagoons, the larger, 6a, being located beside the Dunwich River with 6b being beside the coastal shingle embankment (see Figure C5.6).

The substrate of both water bodies was similar with sand adjacent to the saltmarsh periphery with soft mud soft mud overlying sand away from the edges (see Photographs C5.6 and C5.7). The salinity at 6a was low, ranging from 6 ‰ at the northern end to 13 ‰ at the southern end. By contrast, 6b was close to full marine salinity throughout, ranging from 30 to 31.5 ‰. During the 1998 survey, Bamber recorded 30 ‰ in 6a and hyperhaline conditions (40 ‰) in 6b. Without further monitoring of water conditions, it is not possible to determine whether the reductions in the salinities of these pools is a permanent feature or is a seasonal variation associated with the time of year at which the surveys were undertaken (February 2012 compared to September 1998).

There were small areas of Cladophora across the two lagoons with Enteromorpha in the deeper waters and scattered patches of Chaetomorpha.

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The fauna within lagoon 6a represented a reasonably diverse assemblage and included the various typical lagoon species at relatively high densities. These included Nematostella vectensis, Corophium insidiosum, Idotea chelipes, Hydrobia neglecta and Abra tenuis. This was the only site at which Nematostella vectensis were observed in significant numbers during the habitat searches and were restricted to a small area on the eastern edge of 6a. It is worthy of note that lagoon 6a was the most northerly occurrence of the scheduled lagoon specialist, Gammarus insensibilis (Lagoon Sand-shrimp).

The fauna of lagoon 6b differed from that of 6a in that the polychaete Arenicola marina and the gastropod molluscs occurred in higher density while the crustacea were less abundant. High densities of Hydrobia neglecta were recorded and H. ventrosa and Retusa obtusa also occurred in reasonable abundance. By contrast, the abundance of Corophium insidiosum, C. volutator and Idotea chelipes was markedly lower that in 6a.

The array of species and their relative abundances recorded in lagoon 6a during the 2012 survey was similar to those recorded by Bamber in 1998. Site 6b supported a significantly more diverse and abundant fauna during the 2012 survey than that recorded in 1998 when a total of only 5 taxa were observed, 4 of which were recorded as “rare”.

Species present:

Aquatic Plants Other Observations

Cladophora Enteromorpha Chaetomorpha

Invertebrates 6a 6a veg 6b 6b veg

Observed in field (frequent) at Nematostella vectensis 13 1 6 6a Nemertean indet. 2 Oligochaeta species 42 4 13 14 Arenicola marina Common at Site 6b Spionid 3 Idotea chelipes 8 28 1 Corophium insidiosum 13 5 1 Corophium volutator 27 17 1 1 Gammarus insensibilis 1 Gammarus zaddachi 1

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Chironomid larva 3 2 13 Retusa obtusa 4 6 Hydrobia neglecta 2 29 41 Hydrobia ulvae 4 1 2 Hydrobia ventrosa 1 12 5 Abra tenuis 64 10 24 2

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SITE NAME: Reedland Marshes Lagoon 7 LOCATION: Dunwich Suffolk GRID REFERNCE: TM 48403 72475 TYPE/CLASSIFICATION: Percolation DESIGNATION: SSSI, NNR, SAC, Ramsar and SPA AREA: 0.0476 hectares MAX DEPTH (m): 0.25 SALINITY (‰): 27 ‰ ADJACENT HABITATS: Large areas of SM14 Halimione portulacoides salt-marsh were present across this lagoon, with smaller areas stunted S4 Phragmites australis to the east. SURVEY DATE: 16 February 2012

LAGOON DESCRIPTION:

This pool was the most northerly percolation lagoon within the Reedland Marshes that did not appear to be influenced tidally (see Photograph C5.7). It was isolated within saltmarsh and was not connected to the Dunwich River (see Figure C5.7). The substrate was sandy-mud and the salinity was 27 ‰ throughout.

Small patches of Chaetomorpha and Cladophora occurred here with Ulva lactuca occurring rarely. The algae were restricted to the margins of the water body.

The sweep net sample revealed good numbers of the estuarine mud shrimp, Corophium volutator, while high densities of Hydrobia (H. neglecta, H. ventrosa and H. ulvae) and Idotea chelipes were recorded in the representative vegetation samples.

Unique to this site was the high numbers of a small anemone, believed to be juvenile Sagartia troglodytes, attached to the fronds in one of the aquatic vegetation samples. These were attached by gripping the fronds with their basal suckers. Adult Sagartia troglodytes usually occur attached to rock, stones or shell debris below the surface and extend up through the sediment to feed. Bamber recorded Sagartia troglodytes at lagoon 16, 19 and 21 (all “rare”) but did not discuss their occurrence in the text.

Species present:-

Aquatic Plants Other Observations

Chaetomorpha Cladophora Ulva lactuca

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Invertebrates 7 7 veg 7 veg

Sagartia species 33 Nemertean indet. Oligochaeta species 4 4 21 Arenicola marina Nereis diversicolor 3 Praunus flexuosus 1 2 Palaemonetes varians 1 1 Idotea chelipes 1 17 72 Lekanosphaera rugicauda 2 Corophium insidiosum 2 Corophium volutator 23 1 6 Gammarus insensibilis 1 16 Chironomid larva 21 Hydrobia neglecta 13 122 3 Hydrobia ulvae 20 Hydrobia ventrosa 4 26 Littorina saxatile 1 Abra tenuis 15

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SITE NAME: Reedland Marshes Lagoon 8 LOCATION: Dunwich Suffolk GRID REFERNCE: TM 48415 72371 TYPE/CLASSIFICATION: Tidal Percolation DESIGNATION: SSSI, NNR, SAC, Ramsar and SPA AREA: 0.504 hectares MAX DEPTH (m): 0.05 SALINITY (‰): 32 ‰ ADJACENT HABITATS: Large areas of SM14 Halimione portulacoides salt-marsh were present, with smaller areas of SM8 Annual Salicornia salt-marsh scattered across the lagoon margin. Areas of SM28 Elytrigia repens salt-marsh community were on the higher ridges to the south. On the foreshore was the SD1 Rumex crispus-Glaucium flavum shingle community. SURVEY DATE: 16 February 2012

LAGOON DESCRIPTION:- Site 8 was a large tidal lagoon, of which 80% was exposed mud at the time of this survey (see photograph C5.8). There was a small area of standing water at the western end of the lagoon. The substrate was muddy-sand at the east, mud in the centre with sandy–mud at the western side. The lagoon drained into the Dunwich River through a channel at the north-western side of the site (see Figure C5.8). The salinity of the retained water ranged between 30 and 32 ‰.

Abundant Ulva lactuca occurred here with Enteromorpha (occasional) and Chaetomorpha (rare) also present. Compared to other lagoon sites, the fauna was poor. Only 3 invertebrate taxa were recorded in the sweep net sample, the most abundant being Corophium volutator. The habitat search documented Arenicola marina throughout the site.

Species present:-

Aquatic Plants Other Observations

Ulva lactuca Enteromorpha Chaetomorpha

Invertebrates Arenicola marina Frequent throughout site Corophium volutator 13 Hydrobia neglecta 2 Abra tenuis 1

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SITE NAME: Reedland Marshes Lagoon 9 LOCATION: Dunwich Suffolk GRID REFERNCE: TM 48354 72294 TYPE/CLASSIFICATION: Salt-marsh pool DESIGNATION: SSSI, NNR, SAC, Ramsar and SPA AREA: 0.104 hectares MAX DEPTH (m): 0.2 SALINITY (‰): 27-30 ‰ ADJACENT HABITATS: Dominated by SM14 Halimione portulacoides salt-marsh, with areas of SM8 Annual Salicornia salt-marsh, there were smaller areas of SM28 Elytrigia repens salt-marsh and SM18 Juncus maritima salt-marsh communities. SURVEY DATE: 16 February 2012

LAGOON DESCRIPTION: Lagoon 9 had a very steep edge beyond which was a flat substrate of mud over gravel with a maximum depth of approximately 0.2 m (see Photograph C5.9). It was isolated from other pools and from the Dunwich River (see Figure C5.9). The salinity ranged from 27 to 30 ‰ with the lowest salinity at the eastern (seaward) edge.

The aquatic floral was restricted to growths of Chaetomorpha at the pool margins. The fauna was dominated by annelids with spionid polychaetes and oligochaetes being abundant. Chironomid larvae and the bivalve Abra tenuis also occurred in significant numbers. Only four live specimens of Cerastoderma glaucum were recorded in the sweep net sample but numerous empty shells were observed in the vicinity of the lagoon.

Specimens of the small Sagartia, described above for lagoon 7, were recorded in the sweep net sample. These, presumably, had become dislodged from the Chaetomorpha during the sampling and separation process.

Species present:

Aquatic Plants Other Observations

Chaetomorpha

Invertebrates

Sagartia species 12 Oligochaeta species 100 Arenicola marina 1 Observed occasionally during

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search Spionid 120 Neomysis integer 4 Praunus flexuosus 4 Palaemonetes varians 4 Observed during habitat Corophium species search Chironomid larva 52 Ovatella myosotis 4 Abra tenuis 60 Numerous empty shells Cerastoderma glaucum 4 observed

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SITE NAME: Reedland Marshes Lagoon 10-14 LOCATION: Dunwich Suffolk GRID REFERNCE: TM 48301 72108 TYPE/CLASSIFICATION: Tidal Percolation DESIGNATION: SSSI, NNR, SAC, Ramsar and SPA AREA: 10 - 0.1395hectares, 11 - 0.2296 hectares, 12 – 0.0348 hectares, 13 – 0.0738 hectares; and 14 – 0.036 hectares. MAX DEPTH (m): 0.05 SALINITY (‰): 29-32 ‰ ADJACENT HABITATS: Dominated by SM14 Halimione portulacoides salt-marsh, with areas of SM8 Annual Salicornia salt-marsh and SM10 Transitional low-marsh salt-marsh. There were smaller areas of SM28 Elytrigia repens salt-marsh. SURVEY DATE: 16 February 2012

LAGOON DESCRIPTION:- This area comprised a matrix of five lagoons that are intricately linked (see Figure C5.10). All drain ultimately into the Dunwich River and all are tidal – percolation lagoons. At the time of this survey several were rapidly draining into the river. Lagoons 10, 12 and 13 were largely drained of water during the site visit with the exposed mud comprising 90 %, 70 % and 70 % of the area of the lagoon, respectively. Lagoon 11, which formed a channel-like water body through the middle of the system and lagoon 14 had standing water throughout the majority of their areas.

Lagoons 10-13 (see Photographs C5.10, C5.11, C5.12 and C5.13) had a substrate of soft mud over firmer stable mud (possibly clay). Lagoon 14 (see Photograph C5.14) differed in that its substrate comprised fine mud overlying shingle.

Throughout this system, large areas of the tidally exposed substrate were covered in a matrix of Chaetomorpha, Enteromorpha and Cladophora. The flora of lagoon 14 comprised abundant Cladophora with occasional Chaetomorpha and Ulva lactuca.

The invertebrate sweep net samples from the free-draining sites (lagoons 10, 12 and 13) revealed high densities of Corophium volutator. This species, unlike most other species of Corophium, occur commonly in intertidal muds.

In the previous, 1998, survey Nematostella vectensis, was described as being “particularly common in these lagoons” (Bamber 1998). During the present survey, a single Nematostella vectensis specimen was found in the lagoon 12 sweep net sample and the only Nematostella vectensis that were observed during the habitat search were

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located in the outflow channel of lagoon 10 which retained water throughout the tidal cycle. Bamber reported the maximum depths of this group of water bodies as ranging from 0.1 m to 0.25 m. He did not indicate that the lagoons were tidal. It is, therefore, likely that the reduction in the distribution and density of Nematostella vectensis in this system is due to the loss of the lagoon water retention integrity and the diurnal draining of the majority of the water bodies.

Species present:-

Aquatic Plants Other Observations

Enteromorpha Cladophora Ulva lactuca Chaetomorpha

12 Invertebrates 10 11 12 veg 13 14

Observed in outflow Nematostella vectensis 1 channel of 10 Sagartia species 1 Nemertean indet. 1 Oligochaeta species 14 46 1 1 24 Arenicola marina 2 Occasional at 12 and 14 Nereis diversicolor 1 2 11 1 Capitella capitata 20 4 43 Spionid 6 3 Loxoconchid ?Hirshmannia viridis 3 Praunus flexuosus 1 Palaemonetes varians 2 Idotea chelipes 1 10 Lekanosphaera rugicauda 1 Corophium insidiosum 2 Corophium volutator 21 6 42 43 82 Chironomid larva 5 Retusa obtusa 1 Hydrobia neglecta 1 1 8 Hydrobia ulvae 2 Hydrobia ventrosa 1 1 8 Abra tenuis 1 3 15 3 Cerastoderma glaucum Empty shells frequent

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SITE NAME: Reedland Marshes Lagoon 15 LOCATION: Dunwich Suffolk GRID REFERNCE: TM 48214 71982 TYPE/CLASSIFICATION: Tidal Percolation DESIGNATION: SSSI, NNR, SAC, Ramsar and SPA AREA: 0.0576 hectares MAX DEPTH (m): 0.15 SALINITY (‰): 29 ‰ ADJACENT HABITATS: Dominated by SM14 Halimione portulacoides salt-marsh adjacent to the Dunwich River with large areas of SM8 Annual Salicornia and SM10 Transitional low-marsh salt- marsh, there were smaller areas of SM6 Spartina anglica and SM18 Juncus maritima salt-marsh. SURVEY DATE: 16 February 2012

LAGOON DESCRIPTION:

Lagoon 15 was formerly an isolated hyperhaline water body (see Bamber 1998). During the February 2012 survey, this lagoon was connected directly with the Dunwich River (see Figure C5.11). The salinity in September 1998 was 40 ‰ whilst, during the present survey, it was 29 ‰. The substrate comprised a layer of fine mud overlying shingle on the eastern side with deeper fine mud to the west (see Photograph C5.15).

No aquatic plants species were recorded and the invertebrate fauna was poor, the dominant species being the polychaete Capitella capitata with Corophium volutator sub-dominant.

Species present:-

Aquatic Plants

None observed

Invertebrates Other Observations

Nemertean indet. 1 Capitella capitata 33 Arenicola marina Observed during search (rare) Spionid 9 Cirratulid 5 Corophium volutator 16 Hydrobia neglecta 4

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SITE NAME: Reedland Marshes Lagoon 16 LOCATION: Dunwich Suffolk GRID REFERNCE: TM 48290 71946 TYPE/CLASSIFICATION: Percolation DESIGNATION: SSSI, NNR, SAC, Ramsar and SPA AREA: 0.0144 hectares MAX DEPTH (m): 0.2 SALINITY (‰): 28 ‰ ADJACENT HABITATS: This lagoon was dominated by SM14 Halimione portulacoides salt-marsh adjacent to the open water with large areas of SM18 Juncus maritima salt-marsh and SM10 Transitional low-marsh salt-marsh. On the higher land was the SM28 Elytrigia repens salt-marsh community. The water held areas of SM2 Ruppia maritima. SURVEY DATE: 16 February 2012

LAGOON DESCRIPTION:

This was an isolated, deeper linear lagoon (see Figure C5.12 and Photograph C5.16). The salinity was reduced from full marine levels to 28 ‰ throughout the water body. The substrate comprised mud overlying shingle.

There was abundant Ruppia within this lagoon and very little algae present. The fauna was reasonably diverse and was dominated by Hydrobia neglecta. Also present in good numbers were Capitella capitata, Palaemonetes varians and chironomid larvae.

The lagoon conditions were very similar to those described by Bamber (1999). However, he reported Idotea chelipes and Gammarus insensibilis being common amongst the Ruppia. Although these species were present, they did not occur in abundance during the 2012 survey. Bamber (1999) also reported Nematostella vectensis as being frequent along the northern edge of the lagoon. None were observed or recorded in the sweep net samples during the present survey.

Species present:-

Aquatic Plants

Ruppia

16 16 Invertebrates 16 veg veg Other Observations

Oligochaeta species 23

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Capitella capitata 16 9 Praunus flexuosus 2 Palaemonetes varians 12 Idotea chelipes 6 2 Lekanosphaera rugicauda 8 Gammarus insensibilis 2 Chironomid larva 48 13 Coleopteran larva indet. 1 Hydrobia neglecta 50 36 60 Hydrobia ventrosa 1 6 Ovatella myosotis 1 1 Cerastoderma glaucum 1 1 Gasterosteus aculeatus 2

SITE NAME: Reedland Marshes Shingle Bank Lagoon LOCATION: Dunwich Suffolk GRID REFERNCE: TM 48305 71936 TYPE/CLASSIFICATION: N/A DESIGNATION: SSSI, NNR, SAC, Ramsar and SPA AREA: N/A MAX DEPTH (m): N/A SALINITY (‰): N/A ADJACENT HABITATS: N/A SURVEY DATE: 16 February 2012

LAGOON DESCRIPTION:

The shingle bank lagoon described by Bamber (1999) was not present during the 2012 survey. It is presumed that it had been covered by the encroaching shingle embankment during the intervening period.

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SITE NAME: Reedland Marshes Lagoon 17 LOCATION: Dunwich Suffolk GRID REFERNCE: TM 48166 71662 TYPE/CLASSIFICATION: Percolation DESIGNATION: SSSI, NNR, SAC, Ramsar and SPA AREA: 0.042hectares MAX DEPTH (m): 0.3 SALINITY (‰): 26.5 ‰ ADJACENT HABITATS: These lagoons were dominated by SM18 Juncus maritima salt-marsh, S4 Phragmites australis and SM10 Transitional low-marsh salt-marsh, with areas of SM14 Halimione portulacoides salt-marsh. On the higher land was SM28 Elytrigia repens salt-marsh community. SURVEY DATE: 18 February 2012

LAGOON DESCRIPTION:

A small lagoon with a salinity of 26.5 ‰. The substrate consisted of shingle at the margins with fine mud over shingle throughout the rest of the lagoon (see Photograph C5.17).

The aquatic flora was limited with small amounts of Ruppia with Cladophora at the edges of the water (occasional) and Ulva lactuca (rare)

An established, mature colony of Corophium volutator dominated the fauna. This site also supported the highest density of the estuarine polychaete, Nereis diversicolor, which was recorded during the present Reedland Marshes survey.

Species present:-

Aquatic Plants Other Observations

Ruppia Cladophora Ulva lactuca

Invertebrates

Nereis diversicolor 14 Corophium volutator 65 Gammarus insensibilis 1 Hydrobia neglecta 3

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SITE NAME: Reedland Marshes Lagoon 18 LOCATION: Dunwich Suffolk GRID REFERNCE: TM 48117 71583 TYPE/CLASSIFICATION: Tidal Percolation DESIGNATION: SSSI, NNR, SAC, Ramsar and SPA AREA: 0.02 hectares MAX DEPTH (m): 0.05 SALINITY (‰): 28‰ ADJACENT HABITATS: This lagoon was dominated by SM18 Juncus maritima salt- marsh and SM10 Transitional low-marsh salt-marsh, with small areas of SM14 Halimione portulacoides salt- marsh. On the higher land was SM28 Elytrigia repens salt- marsh community. SURVEY DATE: 18 February 2012

LAGOON DESCRIPTION:-

Lagoon 18 was a very small, shallow lagoon (see Figure C5.13 and Photograph C5.17). The maximum depth was approximately 0.05 m. There was a thin layer of very fine silt overlying a solid substrate.

Emergent vegetation covered most of the lagoon, Juncus maritima being dominant. There was only a very small area of open water on the eastern side of the pool. Within the water, small amounts of Cladophora were present. The fauna was very poor. Only juvenile specimens of a Gammarus species were recorded in the sweep net sample.

The finding of the faunal analysis contrasts markedly with those of Bamber during the 1998 survey. He recorded 7 invertebrate species here and 3 aquatic plants, with Hydrobia neglecta being “abundant” and Arenicola marina, chironomid larvae and Chaetomorpha linum being common. It is likely that the shallow depth of the water body and the consequential encroachment of the Juncus maritima is the cause of the apparent denudation of the aquatic assemblages.

Species present:-

Aquatic Plants Other Observations

Cladophora

Invertebrates

Gammarus juveniles indet 12

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SITE NAME: Reedland Marshes Lagoon 19 LOCATION: Dunwich Suffolk GRID REFERNCE: TM 48012 71432 TYPE/CLASSIFICATION: Tidal Percolation DESIGNATION: SSSI, NNR, SAC, Ramsar and SPA AREA: 0.3528 hectares MAX DEPTH (m): 0.4 SALINITY (‰): 26 ‰ ADJACENT HABITATS: Dominated with SM8 Annual Salicornia salt-marsh, with margins of S4 Phragmites australis and SM14 Halimione portulacoides. On the higher land was the SM28 Elytrigia repens salt-marsh community. SURVEY DATE: 18 February 2012

LAGOON DESCRIPTION:

Lagoon 19 was a relatively large, complex lagoon comprising a narrow “channel” section leading to an open pool (see Figure C5.14). The pool section was connected to the Dunwich River via a channel on the south-eastern side. The substrate throughout was of soft mud overlying a stable substrate, probably clay.

The vegetation both within and in the immediate vicinity of the pool indicated that the area of open water was in the process of expanding (see Photograph C5.18 and C5.19). The SM8 Annual Salicornia salt-marsh was encroaching into the SM28 Elytrigia repens salt-marsh community, the latter visibly dying back (see Photograph C5.18). It is most likely that this successional pattern observed in the salt-marsh plant communities was caused by an increase in the regularity of the saline inundation of the peripheral vegetation.

Within the channel section of the water body Ruppia was present. No other aquatic plants were observed at this location. The invertebrate fauna was dominated by oilgichaetes and chironomid larvae with low densities of Corophium volutator, C. insidiosum, Nereis diversicolor and Arenicola marina. The only mollusc observed was a single specimen of Hydrobia ventrosa.

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Species present:-

Aquatic Plants Other Observations

Ruppia Observed in the channel section

Invertebrates

Nemertean indet. 4 Oligochaeta species 152 Arenicola marina Occasional throughout site Nereis diversicolor 4 Corophium insidiosum 4 Corophium volutator 8 Chironomid larva 24 Hydrobia ventrosa 1

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SITE NAME: Reedland Marshes Lagoon 20 and 21 LOCATION: Dunwich Suffolk GRID REFERNCE: 20 - TM 47926 71021 21 - TM 47900 70957 TYPE/CLASSIFICATION: Tidal Percolation DESIGNATION: SSSI, NNR, SAC, Ramsar and SPA AREA: 20 - 0.4092 hectares 21 - 0.2065 hectares MAX DEPTH (m): 20 - 0.5 21 – 0.1 SALINITY (‰): 22 ‰ ADJACENT HABITATS: Dominated with SM10 Transitional low marsh, with margins of S4 Phragmites australis, SM18 Juncus maritima and SM14 Halimione portulacoides. On the higher land was SM28 Elytrigia repens salt-marsh community. SURVEY DATE: 18 February 2012

LAGOON DESCRIPTION:

Lagoons 20 and 21 comprised a large complex area of inter-connecting tidally determined percolation lagoons (see Figure C5.15). The system ultimately drained into the Dunwich River. The substrate of these water bodies was deep fine mud overlying a stable substrate, probably clay. The salinity of the water within this system was a constant 22 ‰. It is probable that the input of reduced salinity river water from the “upstream” end of the adjacent Dunwich River caused the salinity to be markedly lower than full marine salinity (see Photographs C5.20 and C5.21).

These water bodies supported a reasonable range of invertebrate fauna including the key lagoon specialist species Nematostella vectensis and Gammarus insensibilis. During the previous, 1998, survey, Bamber recorded Nematostella vectensis as abundant. Such densities were not recorded during the recent 2012 survey.

Species present:-

Aquatic Plants Other Observations

None observed

Invertebrates 20 21

Nematostella vectensis 2 11 Oligochaeta species 12

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Nereis diversicolor 1 Capitella capitata 22 Lekanosphaera rugicauda 1 Palaemonetes varians 4 Idotea chelipes 4 Corophium insidiosum 13 1 Corophium volutator 2 Gammarus insensibilis 7 Gammarus deubeni 1 Gammarus juveniles indet 1 Chironomid larva 3

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4. Discussion

4.1 Benacre Pit

The most northerly of the lagoons surveyed during the February 2012 survey was Benacre Pit. This lagoon was created during the Second World War and is the last remaining of a series of pits formed by the extraction of gravel needed for the war effort. Benacre Pit had little freshwater input and was maintained by the percolation and over-topping of the shingle embankment by saline, North Sea water. Consequently, it had a relatively high salinity of 29 ‰ to 31 ‰.

Benacre Pit supported 18 faunal and 5 floral taxa. This represented the most diverse and abundant aquatic plant and animal communities recorded in the lagoons that were assessed during the February 2012 survey. Amongst the species present were archetypal lagoon species such as included the “sea slater”, Idotea chelipes, the Lagoonal Mud Snail, Hydrobia neglecta, the Lagoon Cockle Cerastoderma glaucum, the mudshrimp Corophium insidiosum, the Starlet Sea Anemone Nematostella vectensis and the Lagoon Sand Shrimp, Gammarus insensibilis.

Given the range of plant and animals recorded here, Benacre Pit currently represents an excellent example of a saline lagoon habitat with associated fauna/flora communities. It also has a high conservation value due to the presence of protected species, namely Nematostella vectensis2 and Gammarus insensibilis3. The high numbers of N. vectensis recorded during the February 2012 survey indicated that Benacre Pit is an important site for this species. Populations of N. vectensis are known to exhibit seasonal fluctuations in abundance, with low densities being recorded in late-winter and spring with populations increasing markedly later in the year (Sheader et al., 1997). The present survey was undertaken at the “worst” time of year for N. vectensis densities. It is, therefore, reasonable to assume that the densities of these species will be considerably higher during late summer than those that were recorded during the recent February survey.

To determine the maximum population densities of Nematostella vectensis and Gammarus insensibilis at this site it is recommended that a specific, targeted survey of Benacre Pit be undertaken in early autumn 2012. Such a survey will serve to (i) establish baseline data for these scheduled species at Benacre Pit against which

2 Nematostella vectensis: Wildlife and Countryside Act 1981, Schedule 5,Sections 9.1, 9.2, 9.4a and b, 9.5a and b; Global Red List – vulnerable; UK Biodiversity Action Plan List – Priority Species. 3 Gammarus insenibilis: Wildlife and Countryside Act 1981, Schedule 5,Sections 9.1, 9.2, 9.4a and b, 9.5a and b; Red Data Book of Invertebrates – Rare; UK Biodiversity Action Plan List – Priority Species.

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future changes in habitat conditions and consequential effect on the fauna can be compared and documented and (ii) provide valuable information to enable fully informed management and/or mitigation decisions to be made in the future.

Amongst the aquatic plants documented was a species of Tasselweed, Ruppia. At the time of the survey, it was not possible to determine with confidence the number or identities of these plants due to the requirement for flowering and/or seed head structures to be examined. The Spiral Tasselweed, Ruppia cirrhosa, is considered “nationally scarce”4 and it is possible that this species occurs here. It would be of considerable value to undertake a comprehensive botanical survey of Benacre Pit at the optimum time of year to determine the true abundance and distribution of these plants within the lagoon.

The principal threat to the Benacre Pit saline lagoon habitat appeared to be associated with the encroachment and/or breaching of the shingle embankment on the eastern (seaward) side of the site. It is understood that inundation of the North Sea coastal water by over-topping of the embankment occurs on an annual basis. Such an event had never occurred prior to 1989. At the time of the survey, a “tongue” of sand and shingle protruded into the main body of the lagoon, providing evidence of active encroachment into the water body.

There was no evidence of degradation of the water quality by contamination from other sources. Unlike other sites surveyed during the February 2012 survey (see sections 4.2, 4.3 and 4.4 below), there was no indication of eutrophication due to run- off from adjacent land.

4.2 Benacre Broad

During the previous survey of the Suffolk coast saline lagoons undertaken in 1989, Benacre Broad lagoon system comprised the main broad and a series of small water bodies (see Bamber, 1999). A number of the small pools had been created in 1996 to provide additional lagoon habitat in order to mitigate the loss of habitat caused by coastal erosion. The main water body of Benacre Broad was approximately 5 ha and had a salinity ranging between 16 ‰ and 20 ‰.

Prior to November 2011, salinity of the Benacre Broad had been gradually reduced due to the inflow of freshwater from the adjacent land and freshwater marshes. For a period of approximately four years, the conditions within the main broad had been ostensibly freshwater (Adam Burrows, Natural England, pers. comm.). During November 2011, the single bank at the eastern end of Benacre Broad was over-

4 Ruppia cirrhosa: Vascular Plant Red Data List for Great Britain; Rare and scarce species (not based on IUCN criteria) – nationally scarce

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topped and the freshwater system rapidly became saline. This included the small, artificial saline lagoons surveyed by Bamber in 1998. At the time of the February 2012 survey, this entire area was still submerged. The only areas of water that were not affected directly by the 2011 inundation were the sections protected by the clay bund at the western end of the survey areas (sites 1 and 5; see Figure C2.2, Appendix C). As a consequence of the inundation of seawater, the area of the main broad had increased to approximately 43 ha and the salinity of the water had risen to 22 ‰. The average depth of water within the eastern half of the main water body was approximately 0.5 m. This contrasts with the shallow water conditions described by Bamber at the small lagoons during the 1998 survey.

The sites of the small lagoons surveyed by Bamber in 1998 were identified by a slight increase in depth. The depression in the water body bed had apparently been in-filled by fine silt and plant detritus and the substrate at these sites appeared very soft and flocculent.

Such rapid and extreme changes in habitat conditions will inevitably lead to an initial drop in diversity of the habitat as the established, colonised flora and fauna is displaced. If the “new” conditions persist, it can be expected that an alternative flora and fauna will establish. Despite the short period of time between the November 2011 inundation event and the February 2012 survey, there was evidence that exploitation of the deeper, saline conditions was occurring. At the sites within the main body of water, the diversity was generally quite low. However, the estuarine amphipod Corophium volutator was ubiquitous at the sites with a salinity of 22 ‰ and was extremely abundant at a number of locations (see, for example, Benacre Broad site 10). Conversely, the low salinity amphipod, Corophium multisetosum, that was previously recorded as “frequent” at site 2 (Bamber, 1999) was not observed during the recent 2012 survey.

During the 1998 survey, Bamber recorded the scheduled Starlet Anemone, Nematostella vectensis, at a single site (site 10, see Bamber 1999). None were observed during the 2012 survey. The conditions documented during the 2012 survey were no longer suitable for N. vectensis, as this species requires shallow water with stable substrates.

Two locations within the 2012 survey were, at the time of the survey, freshwater. These were sites 1 and 8 (see figure C2.1, Appendix C). These sites were separated from the main water body by a clay bund. The faunal community at site 1 indicated that the location is subjected to periodic elevations in the salinity as the fauna was characterised by brackish water species. Site 8, however, had a more typical “freshwater” assemblage.

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It is understood that the freshwater run-off from the adjacent land maintains the low salinity conditions at these sites. At site 8, there was evidence of eutrophication of the water. This evidence included the presence of large quantities of the cyanobacteria (blue-green algae) Nostoc species. Nutrient-rich run-off from farmland represents an immediate threat to the water quality, and hence the ecological value, of the Benacre Broad aquatic system. It is recommended that further investigations are conducted to determine the water quality status of the broad and the inflow/run- off waters from adjacent land.

4.3 Covehithe Broad

Over recent years, Covehithe Broad has been reduced in size due to coastal erosion and the encroachment of the seaward sand and gravel. This was apparent at the time of the survey as there was a large amount of loose, unconsolidated sand at the eastern (seaward) side of the lagoon (see Photograph C3.2).

The flora and fauna of Covehithe Broad was very poor. Only one algal species was observed and the sweep net samples revealed very few invertebrates. Whilst the authors have no previous data on the invertebrates of Covehithe Broad, the floral community recorded during the survey represents a considerable decline over the past decade. Covehithe lagoon formerly had a rich aquatic flora. Ten species of aquatic macrophyte were recorded here in 2001 including the “nationally scarce” Spiral Tassleweed, Ruppia cirrhosa, (Abrehart, 2001). Whilst it is appreciated that the 2012 survey was not undertaken at the optimum time of year for a botanical survey, the presence of aquatic plants would have been noted if the habitat supported significant floral communities.

Whilst the encroachment of the sand dunes into the lagoon is a significant threat to the Covehithe saline lagoon habitat, the field observations in conjunction with the depauperate flora and fauna assemblages recorded indicated that this water body had become eutrophic. Consequently, the ecological and conservational value of the lagoon has been significantly reduced.

Assessment of the water quality in terms of nutrient content, chemical and biological oxygen demand etc., for the lagoon and any feeder streams was beyond the remit of the current survey; therefore it was not possible to determine the cause source or pathway of the apparent eutrophication. It was, however, noted that free-range pig farming was being practiced on the land immediately to the west of the lagoon. It is possible that nutrient-rich surface run-off from this site is entering the lagoon, contributing to the eutrophic conditions. This is, at present, speculation and further investigations are required to determine (i) the water quality status of Covehithe lagoon and (ii) the source and pathway of any nutrient-rich materials entering the water body. Only upon completion of these investigations can a mitigation strategy

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be devised and implemented with the aim to restore the Covehithe lagoon to previously existing conditions and to enhance it ecological and conservational value.

4.4 Easton Broad

At the time of the 2012 survey, the salinity of Easton Broad was 0 ‰. It is likely that the salinity at the eastern end of this system elevates sporadically due to over- topping of the sand/shingle embankment by North Sea waters. Evidence from the faunal species documented indicates that elevated salinity conditions had not persisted at this location.

As described above for Covehithe lagoon, Easton Broad has shrunk considerably in recent years. This is demonstrated vividly by comparing the red line boundary of the lagoon edge as determined on 17 February 2012 with the water’s edge of the aerial image taken previously (see figure C4.1). It was evident that the encroachment of the sand dunes was continuing and “young” mobile sand dunes of the foreshore were steadily encroaching upon the open water areas at the eastern edge of this lagoon (see Photograph C4.1).

The flora and fauna at Easton Broad was generally poor in terms of abundance and number of species. As previously described for Covehithe, there was evidence of eutrophication of the water. It is recommended that further investigations into the water quality of this broad and its tributaries are undertaken. If necessary, mitigation measures may need to be adopted to prevent the ecological deterioration of the remaining habitats occurring as a result of uncontrolled nutrient enrichment from adjacent land.

Of considerable interest was the occurrence of the endangered (RDB 1) snail, Mercuria (=Pseudamnicola) confusa. This was recorded in the sweep sample from site 1, collected from the edge of the Phragmites bed at the south-eastern end of the lagoon (see Photograph C4.1).

Mercuria confusa is restricted to waters of very low salinity, usually ranging between 1 ‰ and 5 ‰ and, as in this case, is commonly associated with emergent plants such as Phragmites and Carex. According to Kerney (1999) the largest surviving population in the UK is probably found in Oulton Broad, approximately 13 km north of Easton Broad. It had been found previously at Blythburgh, three km to the south-west of Easton Broad, in 1908 (Killeen, 1992) although no further specimens have been found in the area.

There are two imminent threats to the Mercuria confusa population of Easton Broad. Firstly, the continued encroachment of the sand dunes into the broad will reduce directly the area of potential habitat for this species. Secondly, and possibly more

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importantly, is the potential for the salinity of the broad to increase due to regular over-topping of the sand dune embankment that currently separates the broad from the coastal waters. A persistent elevation of the salinity of the broad will eradicate Mercuria confusa from this site.

Due to the limited remit of the present survey, the extent and abundance of Mercuria confusa at Easton Broad was not determined and, hence, the conservational value of the Easton Broad population of this species is not known. It is recommended that targeted assessment of Mercuria confusa and suitable habitat within the local area is undertaken to enable appropriate mitigation and, if necessary, habitat enhancement measures to be undertaken to maintain this potentially valuable population.

4.5 Reedland Marshes

The saline lagoon at Reedland Marshes was located within a thin strip of marshland located between the Dunwich River and the shore that extends approximately 2.5 km north of Dunwich beach car park (see figure C2.1, Appendix C). A total of 21 pools were surveyed corresponding to those surveyed previously in 1998 (see Bamber, 1999).

The Reedland Marshes lagoons supported a relatively wide range of invertebrates, a total of 39 taxa being recorded during the present survey. The taxa recorded corresponded closely with the findings of Bamber (1999). Archetypical lagoon species represented within the Reedland Marshes saline lagoon system included the Spire Snail of Hydrobia ventrosa, the Lagoonal Mud Snail, Hydrobia neglecta, the Lagoon Cockle Cerastoderma glaucum, “sea slater”, Idotea chelipes, the mudshrimp Corophium insidiosum, the Starlet Anemone Nematostella vectensis and the Lagoon Sand Shrimp, Gammarus insensibilis.

The species of significant conservational importance, the scheduled species Nematostella vectensis and Gammarus insensibilis (see section 4.1 for details), varied in distribution and abundance across the marsh system. Gammarus insensibilis occurred only within the southern half of the marsh, the most northerly occurrence being at site 6. A similar distribution pattern was documented by Bamber (1999) when the majority of the G. insensibilis population occurred within lagoons 7 to 21.

The recorded occurrence and abundance of the Starlet Sea Anemone, Nematostella vectensis, was significantly reduced at the time of the February 2012 survey compared to the results of the previous 1998 survey (1999). Bamber documented N. vectensis at 14 of the 21 water bodies with “abundant” or “super-abundant” population being recorded. This species was only documented in seven water bodies during the 2012 survey and only at sites 6 and 21 were significant numbers recorded (see section 3.5). However, these results may be misleading. As discussed previously

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for Benacre Pit (see Section 4.1), populations of N. vectensis are known to exhibit seasonal fluctuations in abundance with low densities being recorded in late-winter and spring with populations increasing markedly later in the year. Populations have been observed to vary from less than 120 individuals/m2 to 2700 individuals/m2 (Sheader et al., 1997), representing a 22 fold increase in abundance. The survey reported by Bamber (1999) was undertaken in late September 1998, the optimum time for N. vectensis abundance, whilst the 2012 survey was undertaken in February, probably the most sub-optimal period for N. vectensis abundance. Consequently, it is highly likely that the 2012 study has significant unrepresented both the distribution of this species in this area and the potential N. vectensis holding capacity of the lagoons surveyed. To achieve comparable data to that of Bamber (1999) an assessment of N. vectensis with this system would need to be undertaken during late summer 2012.

There were two distinct physical changes in the Reedland Marshes lagoon system that were noted when compared with the description provided by Bamber (1999). Firstly, the encroachment of the shingle embankment throughout the northern half of the survey area was markedly reducing the area of lagoon habitat available. The artificial maintenance of the shingle bank (described by Bamber (1999) as “maintenance of which is essential to the lagoons longer term existence”) has ceased and, consequently, the inland migration of the shingle embankment has continued unabated. At the northern end of the areas, the pools labelled by Bamber as Sites 1b, 1c and 2, no longer existed and had been replaced by areas of dry shingle, some of which had become colonised with halophytic plants.

It is worthy of note that coastal vegetated shingle is a Biodiversity Action Plan priority habitat. It is likely that, if the shingle on the landward side of the current coastal embankment remains stable, an SD1 Rumex crispus-Glaucum flavum shingle community (as noted at sites 5, 6 and 8; see Section 3.5) will develop. This in itself will be of conservation interest.

The second notable difference between the lagoons conditions described by Bamber (1999) and the observations made during the 2012 survey of evidence of tidal variation in the water depth in the lagoons in the mid and southern sections of the Reedland Marsh survey area. Sites 8 to 21 all displayed evidence of tidal influence. This was most apparent at sites 8, 10, 11 and 12 where 80 %, 90 %, 70 % and 70 %, respectively, of the lagoons’ substrate were exposed at the time of the survey. By definition, lagoons are supposed to have permanent water. If these areas become fully tidal, the potential to support specialist lagoon floral and fauna species will, obviously, be diminished.

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5. Acknowledgements Abrehart Ecology would like to thank Adam Burrows for commissioning this survey and with his help on accessing the sites. Thanks also to the RSPB and SWT for permission to access Reedland Marshes.

6. References cited in text

This report to be cited as:

Abrehart Ecology (2012). Ecological Surveys of Saline Lagoons on the Benacre NNR and Suffolk Coast NNR; February 2012. Invertebrate and botanical survey undertaken for Natural England by Abrehart Ecology. Report Date: 11 March 2012.

Abrehart, T.R. (2001). Shingle and Lagoon Survey on Benacre NNR 2001. Botanical survey undertaken for Natural England by Toby Abrehart.

Bamber, R.N. (1999). Survey of selected saline lagoon, Suffolk coast, September 1998). English Nature Research Report Number 300.

Barnes, R.S.K. (1994). The brackish-water fauna of north-western Europe. Cambridge University Press, Cambridge, UK. pp 287.

Gledhill, T., Sutcliffe D.W. and Williams, W.D. (1993). British Freshwater Crustacea – Malacostraca: A key with Ecological Notes. Freshwater Biological Association, Ambleside, UK.

Kerney, M. (1999). Atlas of the land and freshwater molluscs of Britain and Ireland. Harley Books, Colchester, UK. pp 264.

Killeen, I.J. (1992). The land and freshwater molluscs of Suffolk. Suffolk Naturalists Society, Ipswich, UK. pp 171.

Rodwell, J.S. (1998a). British Plant Communities. Volume 1: Woodlands and Scrub. Cambridge University Press.

Rodwell, J.S. (1998). British Plant Communities. Volume 2: Mires and Heaths. Cambridge University Press.

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Rodwell, J.S. (1998). British Plant Communities. Volume 3: Grasslands and Montane Communities. Cambridge University Press.

Rodwell, J.S. (1995). British Plant Communities. Volume 4: Aquatic Communities, Swamps and Tall-Herb Fens. Cambridge University Press.

Rodwell, J.S. (2000). British Plant Communities. Volume 5: Maritime Communities and Vegetation of Open Habitats. Cambridge University Press.

Sheader, M., Suwailem, A.M. and Rowe, G.A. (1997). The anemone, Nematostella vectensis, in Britain: considerations for conservation management. Aquatic Conservation: Marine and Freshwater Ecosystems, 7, 13-25.

Trett, M.W., Calvo Urbano, B., Forster, S.J. and Trett, S.P. (2009). Commercial Aspects of the use of Nematodes as Bioindicators. In Nematodes as Environmental Indicators. Eds. Wilson, M.J. and Kakouli-Duarte, M. Pages 275 – 326. CAB International, Cambridge and Wallingford.

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Appendices:

Appendix A:

Taxonomic list for the macrofaunal species recorded in the sweep net samples collected and observations during the Suffolk saline lagoon survey, February 2012.

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Table A1. Full taxonomic list for the species recorded by Abrehart Ecology in the survey carried out for Natural England of aquatic and terrestrial habitats at 45 sampling stations on the north Suffolk Saline Lagoons, between 16 - 18 February 2012. Botanical taxonomy conforms to Stace (1997).

Kingdom Plantae

Plant records presented here were all field observations confirmed where necessary by collection of samples of materials (e.g. seed heads, leaves and stems).

Class Ulvophyceae; Sub-class Ulvophyliidae

Order Cladophorales

Family Cladophoraceae Cladophora sp

Order Ulvales Family Ulvaceae Ulva intestinalis Ulva lactuca

Class Chlorophyceae; Sub-class Chlorophytidae

Order Chaetophorales

Family Chaetophoraceae Chaetophora elegans

Class Magnoliopsida; Subclass Magnoliidae (Dicotyledons) Superorder Magnoliiflorae; Order Ranuculales

Family Ceratophyllaceae Ceratophyllum submersum Soft Hornwort

Family Ranunculaceae Ranunculus sceratus Celery-leaved Buttercup

Superorder Hamameliflorae; Order Urticales

Family Urticaceae Urtica dioica Common Stinging Nettle

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Superorder Caryophylliflorae; Order Caryophyllales

Family Chenopodaceae Atriplex patula Common Orache Atriplex prostrata Spear-leaved Orache Halimione portulacoides Sea Purslane Salicornia species Glasswort Sueda maritima Annual Sea-blite Chenopodium rubrum Red Goosefoot

Family Caryophyllaceae Cerastium fontana Common Mouse-ear Silene uniflora Sea Campion Spergularia media Greater Sea-spurrey

Order Polygonales

Family Polygonaceae Rumex crispus Curled Dock

Superorder Dilleniiflorae; Order Malvales

Family Malvaceae Malva sylvestris Common Mallow

Order Salicales

Family Salicaceae Salix caprea Goat Willow

Order Capparales

Family Brasicaceae (“Cruciferaceae”) Beta vulgaris ssp maritima Sea Beet Sisymbrium officinalis Hedge Mustard

Superorder Rosiflorae; Order Rosales

Family Primulaceae Glaux maritima Sea-milkwort

Family Rosaceae Rosa canina Dog Rose Rubus ulmifolius Bramble

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Order Fabales

Family Fabaceae Lotus corniculatus Bird’s-foot Trefoil Vicia sativa segatalis Common Vetch Lathyrus japonicus Sea Pea

Order Myrtales

Family Onagraceae Chamerion angustifolium Rose Bay Willowherb

Order Geraniales

Family Geraniaceae Geranium pusillum Small-flowered Crane’s-bill

Order Apiales

Family Apiaceae Chaerophyllum temulentum Rough Chervil Conium maculatum Hemlock

Superorder Asteriflorae; Order Solanales

Family Solanaceae Solanum dulcranum Bitter sweet

Order Lamiales

Family Boraginaceae Myosotis arvensis Field Forget-me-not

Family Lamiaceae Ballota nigra Black Horehound Mentha aquatica Water Mint

Order Plantaginales

Family Plantaginaceae Plantago lanceolata Lanceolate Plantain Plantago maritima Sea Plantain

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Order Rubiales

Family Rubiaceae Gallium aparine Cleavers

Order Asterales

Family Asteraceae Cirsium arvensis Creeping Thistle Cirsium vulgare Spear Thistle Sonchus asper Prickly Sow-thistle Sonchus oleraceus Smooth Sow-thistle Sonchus arvensis Corn Sow-thistle Senecio jacobea Common Ragwort Taraxicum sp Dandelion Aster tripolium Sea Aster Matricaria recutita Scentless Mayweed Centurea nigra Common Knapweed Lactuca serrola Prickly Lettuce Picris echiloides Prickly Ox-tongue

Subclass Liliidae (Monocotyledons)

Superorder Alismatiflorae; Order Najadales

Family Ruppiaceae Ruppia maritima Beaked Tassel-weed

Superorder Areciflorae; Order Arales

Family Lemnaceae Lemna minor Common Duckweed

Superorder Commeliniflorae; Order Juncales

Family Juncaceae Juncus effusus Soft Rush Juncus maritimus Sea Rush Juncus gerardii Salt-marsh Rush

Order Cyperales

Family Poaceae Festuca rubra Red Fescue Dactylis glomerata Cock’s-foot Lolium perenne Perennial Rye-grass Arrehenatherum elatius False Oat-grass

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Poa annua Annual Meadow-grass Holcus mollis Creeping Soft-grass Agrostis stolonifera Creeping Bent Bromus hordaceus Soft Broome Anisantha sterilis Sterile Brome Elytrigia repens Common Couch Phragmites australis Common Reed

Order Sparganiales

Family Sparganiaceae Sparganium erectum Branched Bur-reed

Order Typhales

Family Typhaceae Typha latifolia Common Reedmace

Superorder Liliiflorae; Order Araceales

Order Liliales

Family Iridaceae Iris pseudacorus Yellow Flag

Kingdom Animalia

Phylum Cnidaria

Class Hexacorallia

Order: Actiniaria

Family: Edwardsiidae Nematostella vectensis

Family: Sagartiidae Sagartia species ?S. troglodytes

Phylum Nemertea

Nemertean indet.

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Phylum Annelida

Class Oligochaeta

Oligochaeta species

Class Hirudinea

Order: Rhynchobdellida Family: Glossiphoniidae Helobdella stagnalis

Class Polychaeta

Order Capitellida;

Family Arenicolidae Arenicola marina Heteromastus filiformis

Order Phyllodocida;

Family Nereididae Nereis diversicolor

Phylum Biramia (= “Crustacea”)

Class Ostracoda;

Order Podocopida;

Family Loxoconchidae Loxoconchid ? Hirshmannia viridis

Class Malacostraca;

Order Mysida;

Family Mysidae Neomysis integer Praunus flexuosus

Order Decapoda;

Family Palaemonidae Palaemonetes varians

Family Crangonidae Crangon crangon

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Order Isopoda;

Family Idoteidae Idotea chelipes

Family Asellidae Asellus aquaticus (subspecies not determined)

Family Sphaeromatidae Lekanosphaera rugicauda

Order Amphipoda;

Family Corophiidae Corophium insidiosum Corophium volutator

Family Gammaridae Gammarus insensibilis Gammarus lacustris Gammarus zaddachi Gammarus deubeni

Class Insecta;

Order Diptera;

Family Chironomidae; Chironomid larva

Family Dolichopodidae; Dolychopodid larva

Family Ephidridae; Ephidrid larva

Family Tipulidae; Tipulid larva

Order Heteroptera;

Family Corixidae; Callicorixa praeusta Sigara dorsalis

Order Coleoptera;

Coleopteran larva indet.

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Phylum Mollusca

Class Gastropoda

Order Cephalaspidea

Family Retusidae Retusa obtuse Retusa elongata

Order Mesogastropoda

Family Bithyniidae Bithynia tentaculata

Family Hydrobiidae; Hydrobia neglecta Hydrobia ulvae Hydrobia ventrosa Mercuria confusa Potamopyrgus antipodarum (= P. jenkinsi)

Order Basommatophora

Family Acroloxidae Acroloxus lacustris

Family Lymnaeidae Radix (=Lymnaea) peregra

Family Planorbidae Gyraulus crista

Order Littorinimorpha

Family Littorinidae Lacuma parva Littorina saxatile Littorinid ?Littorina neglecta

Order Pulmonata

Family Ellobiidae Ovatella myosotis

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Class Bilvalvia

Order Myoidea

Family Myidae Mya arenaria

Order Veneroidea

Family Semelidae Abra tenuis

Family Cardiidae Cerastoderma glaucum

Phylum Bryozoa;

Class Gymnolaemata;

Order Cheilostomata

Family Membraniporidae Conopeum seurati

Family Flustridae Flustra foliacea

Phylum Chordata; Subphylum Vertebrata

Class Osteichythes;

Order Gasterosteiformes

Family Gasterosteidae Gasterosteus aculeatus

Order Perciformes

Family Gobiidae Pomatoschistus microps

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Appendix B:

Site-by-site results for the macrofaunal species recorded in the sweep net samples collected during the Suffolk saline lagoon survey, February 2012.

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Table B1: Site-by-site list for the species recorded by Abrehart Ecology in the survey carried out for Natural England of aquatic and terrestrial habitats at 45 sampling stations on the north Suffolk Saline Lagoons between 16 -18 February 2012.

Benacre Pit Benacre Broad Site 1 2 3i 3ii 1 2 3 4 5 6 7 Salinity ‰ 29 30 31 30 0 22 22 22 0 18 22 Nematostella vectensis 41 9 6 93 Sagartia species Nemertean indet. 8 12 7 Oligochaeta species 8 19 35 2 Arenicola marina 1 Nereis diversicolor Pygospio elegans 1 1 Heteromastus filiformis Spionid Cirratulid 9 4 11 Helobdella stagnalis Loxoconchid ?Hirshmannia viridis Neomysis integer 30 49 2 1 6 Praunus flexuosus Palaemonetes varians Crangon crangon Idotea chelipes 2 5 6 2 Asellus aquaticus Lekanosphaera rugicauda 5 5 8 Corophium insidiosum 386 391 263 68 Corophium volutator 4 3 315 20 100 31 8 Gammarus insensibilis 1 Gammarus lacustris Gammarus zaddachi 40 17 2 4 3 6 Gammarus deubeni 6 Gammarus juveniles indet Chironomid larva 2 1 1 105 36 52 6 39 50 Dolichopodid larva Tipulid larva Ephydrid larva Callicorixa praeusta 1 Sigara dorsalis Coleopteran larva indet. Retusa obtusa 2 Retusa elongata Bithynia tentaculata Hydrobia neglecta 1 23 5 Hydrobia ulvae Hydrobia ventrosa Mercuria confusa Potamopyrgus antipodarum 2 4 Acroloxus lacustris

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Benacre Pit continued Benacre Broad continued Site 1 2 3i 3ii 1 2 3 4 5 6 7 Salinity ‰ 29 30 31 30 0 22 22 22 0 18 22 Gyraulus crista Lacuma parva Littorina saxatile Littorinid ?Littorina neglecta Ovatella myosotis Mya arenaria 1 Abra tenuis Cerastoderma glaucum 1 2 Conopeum seurati Flustra foliacea Gasterosteus aculeatus 1 Pomatoschistus microps 1

Easton Broad Covehithe Broad Site 1 2 1 3 Salinity ‰ 0 0 19 18 Nematostella vectensis Sagartia species Nemertean indet. Oligochaeta species 19 2 Arenicola marina Nereis diversicolor Pygospio elegans Heteromastus filiformis Spionid Cirratulid Helobdella stagnalis Loxoconchid ?Hirshmannia viridis Neomysis integer 4 1 21 Praunus flexuosus Palaemonetes varians Crangon crangon Idotea chelipes Asellus aquaticus Lekanosphaera rugicauda 1 14 Corophium insidiosum Corophium volutator Gammarus insensibilis Gammarus lacustris Gammarus zaddachi 1 4 Gammarus deubeni 1 2 Gammarus juveniles indet Chironomid larva 2 Dolichopodid larva 1 Tipulid larva 1 Ephydrid larva Callicorixa praeusta

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Easton Broad continued Covehithe Broad continued Site 1 2 1 3 Salinity ‰ 0 0 19 18 Sigara dorsalis Coleopteran larva indet. 1 Retusa obtusa Retusa elongata Bithynia tentaculata 1 Hydrobia neglecta Hydrobia ulvae Hydrobia ventrosa Mercuria confusa 12 Potamopyrgus antipodarum Acroloxus lacustris Radix (=Lymnaea) peregra 1 Gyraulus crista Lacuma parva Littorina saxatile Littorinid ?Littorina neglecta Ovatella myosotis Mya arenaria Abra tenuis Cerastoderma glaucum Conopeum seurati Flustra foliacea 1 Gasterosteus aculeatus Pomatoschistus microps

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Reedland Marsh Site 1a 1a 1b 3 4 5 i 5 ii 6a i 6a ii 6b i 6b veg ii Salinity ‰ 31 31 32 32 10-32 30 34 13 6 31 31 Nematostella vectensis 3* 5 1 13 1 6 Sagartia species Nemertean indet. 7 2 8 16 2 8 2 Oligochaeta species 1200 360 63 175 8 23 42 4 13 14 Arenicola marina Nereis diversicolor Pygospio elegans 3 Heteromastus filiformis Spionid 3 Cirratulid Helobdella stagnalis Loxoconchid ?Hirshmannia viridis Neomysis integer Praunus flexuosus 3 6 2 5 Palaemonetes varians Crangon crangon 1 Idotea chelipes 3 8 28 1 Asellus aquaticus Lekanosphaera rugicauda Corophium insidiosum 13 5 1 Corophium volutator 1 27 17 1 1 Gammarus insensibilis 1 Gammarus lacustris Gammarus zaddachi 1 Gammarus deubeni Gammarus juveniles indet Chironomid larva 2 11 34 2 6 12 3 2 13 Dolichopodid larva Tipulid larva Ephydrid larva 1 Callicorixa praeusta Sigara dorsalis Coleopteran larva indet. Retusa obtusa 6 4 6 Retusa elongata 6 Bithynia tentaculata Hydrobia neglecta 16 8 13 64 7 590 6 2 29 41 Hydrobia ulvae 1 4 1 2 Hydrobia ventrosa 2 4 9 30 1 12 5 Mercuria confusa Potamopyrgus antipodarum Acroloxus lacustris Radix (=Lymnaea) peregra

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Reedland Marsh continued Site 1a 1a 1b 3 4 5 i 5 ii 6a i 6a ii 6b i 6b veg ii Salinity 31 31 32 32 10-32 30 34 13 6 31 31 Radix (=Lymnaea) peregra Gyraulus crista Lacuma parva 7 Littorina saxatile Littorinid ?Littorina 2 1 neglecta Ovatella myosotis Mya arenaria Abra tenuis 2 70 19 8 64 10 24 2 Cerastoderma glaucum 3 1 Conopeum seurati Flustra foliacea Gasterosteus aculeatus Pomatoschistus microps 1

Reedland marsh Site 7 i 7 ii 7 iii 8 9 10 11 12 i 12 ii 13 14 Salinity ‰ 27 27 27 31 30 32 30 31 31 29 30 Nematostella vectensis 1 Sagartia species 33 12 1 Nemertean indet. 1 Oligochaeta species 4 21 4 100 14 1 46 1 24 Arenicola marina 1 2 Nereis diversicolor 3 2 1 11 1 Pygospio elegans Heteromastus filiformis 20 4 43 Spionid 120 6 3 Cirratulid Helobdella stagnalis Loxoconchid ?Hirshmannia 3 viridis Neomysis integer 4 Praunus flexuosus 2 1 4 1 Palaemonetes varians 1 1 4 2 Crangon crangon Idotea chelipes 17 72 1 1 10 Asellus aquaticus Lekanosphaera rugicauda 2 1 Corophium insidiosum 2 2 Corophium volutator 1 6 23 13 21 6 43 42 82 Gammarus insensibilis 1 16 Gammarus lacustris Gammarus zaddachi

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Reedland marsh continued Site 7 i 7 ii 7 iii 8 9 10 11 12 i 12 ii 13 14 Salinity ‰ 27 27 27 31 30 32 30 31 31 29 30 Gammarus deubeni Gammarus juveniles indet Chironomid larva 21 52 5 Dolichopodid larva Tipulid larva Ephydrid larva Callicorixa praeusta Sigara dorsalis Coleopteran larva indet. Retusa obtusa 1 Retusa elongata Bithynia tentaculata Hydrobia neglecta 122 3 13 2 1 1 8 Hydrobia ulvae 20 2 Hydrobia ventrosa 26 4 1 1 8 Mercuria confusa Potamopyrgus antipodarum Acroloxus lacustris Radix (=Lymnaea) peregra Gyraulus crista Lacuma parva Littorina saxatile 1 Littorinid ?Littorina neglecta Ovatella myosotis 4 Mya arenaria Abra tenuis 15 1 60 1 15 3 3 Cerastoderma glaucum 4 Conopeum seurati Flustra foliacea Gasterosteus aculeatus Pomatoschistus microps

Reedland Marsh Site 15 16 i 16 ii 16 iii 17 18 19 20 21 Salinity ‰ 29 28 28 28 26.5 28 26 22 22 Nematostella vectensis 2 11 Sagartia species Nemertean indet. 1 4 Oligochaeta species 23 152 12 Arenicola marina Nereis diversicolor 14 4 1 Pygospio elegans Heteromastus filiformis 33 16 9 22 Spionid 9 Cirratulid 5 Helobdella stagnalis Loxoconchid ?Hirshmannia viridis

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Reedland Marsh continued Site 15 16 i 16 ii 16 iii 17 18 19 20 21 Salinity ‰ 29 28 28 28 26.5 28 26 22 22 Neomysis integer Praunus flexuosus 2 Palaemonetes varians 12 4 Crangon crangon Idotea chelipes 6 2 4 Asellus aquaticus Lekanosphaera rugicauda 8 1 Corophium insidiosum 4 13 1 Corophium volutator 16 65 8 2 Gammarus insensibilis 2 1 7 Gammarus lacustris Gammarus zaddachi Gammarus deubeni 1 Gammarus juveniles indet 12 1 Chironomid larva 48 13 24 3 Dolichopodid larva Tipulid larva Ephydrid larva Callicorixa praeusta Sigara dorsalis Coleopteran larva indet. 1 Retusa obtusa Retusa elongata Bithynia tentaculata Hydrobia neglecta 4 50 36 60 3 Hydrobia ulvae Hydrobia ventrosa 1 6 1 Mercuria confusa Potamopyrgus antipodarum Acroloxus lacustris Radix (=Lymnaea) peregra Gyraulus crista Lacuma parva Littorina saxatile Littorinid ?Littorina neglecta Ovatella myosotis 1 1 Mya arenaria Abra tenuis Cerastoderma glaucum 1 1 Conopeum seurati Flustra foliacea Gasterosteus aculeatus 2 Pomatoschistus microps

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Appendix C:

Location figures and photographs of the lagoons and sampling sites assessed during the Suffolk saline lagoon survey, February 2012.

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Figure C1.1: Low resolution aerial view of the locations of the sample sites at Benacre Pits surveyed by Site 2 Site 1 Abrehart Ecology during the survey undertaken on 17 February 2012. The edge of the lagoon, as recorded during the February 2012 survey, is indicated by the red line.

Site 2

Site 3 Site 1

Photograph C1.1: Benacre Pits, looking north to south. In the left of the image the encroaching shingle can be seen clearly. Photograph taken on 17 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England.

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Figure C2.1: Low resolution aerial view Site 1 Site 2 of the locations of the

sample sites at

Benacre Broad Site 3 Site 9 surveyed by Abrehart Site 5 Ecology during the survey undertaken on Site 8 Site 10 17 February 2012.

The edge of the lagoon, as recorded during the February 2012 survey, is

indicated by the red line. Site 6 Site 4

Site 7 Site 11

Photograph C2.1: Benacre Broad Site 1. Photograph taken on 17th February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England.

Photograph C2.2: Benacre Broad Photograph C2.3: Benacre Broad

Site 2. Photograph taken on 17 Site 3. Photograph taken on 17

February 2012 during the saline February 2012 during the saline lagoon survey undertaken by lagoon survey undertaken by

Abrehart Ecology for Natural Abrehart Ecology for Natural

England. England.

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Photograph C2.4: Benacre Photograph C2.5: Benacre Broad Broad Site 4. Photograph taken Site 5. Photograph taken on 17 on 17 February 2012 during the February 2012 during the saline saline lagoon survey lagoon survey undertaken by undertaken by Abrehart Abrehart Ecology for Natural Ecology for Natural England. England.

Photograph C2.6: Benacre Photograph C2.7: Benacre Broad Site 6. Photograph taken Broad Site 7. Photograph taken on 17 February 2012 during the on 17 February 2012 during the saline lagoon survey saline lagoon survey undertaken by Abrehart undertaken by Abrehart Ecology for Natural England. Ecology for Natural England.

th Photograph C2.8: Benacre Broad Site 8. Photograph taken on 17 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England.

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Photograph C2.9: Benacre Broad Site 9 looking south to north. Photograph taken on 17 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England.

Photograph C2.10: Benacre Photograph C2.11: Benacre Broad Site 10. Photograph taken Broad Site 11. Photograph taken on 17 February 2012 during the on 17 February 2012 during the saline lagoon survey undertaken saline lagoon survey by Abrehart Ecology for Natural undertaken by Abrehart England. Ecology for Natural England.

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Figure C3.1: Low resolution aerial view of the locations of the sample sites at Covehithe Broad surveyed by Abrehart Ecology during the survey undertaken on 17 February 2012. The edge of the lagoon, as

recorded during the February 2012 survey, is indicated by the red line. Site 3

Site 1

Photograph C3.1: Covehithe Broad Site 1. Photograph taken on 17 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England.

Photograph C3.2: Covehithe Broad Site 3. Photograph taken on 17 February 2012 during the saline lagoon

survey undertaken by Abrehart Ecology for Natural England.

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Figure C4.1: Low resolution aerial view of the locations of the sample sites at Easton Broad surveyed by Abrehart Ecology during the survey

undertaken on 17 February 2012. The edge of the lagoon, as recorded Site 2 during the February 2012 survey, is indicated by the red line.

Site 1

Blocked sluice

Photograph C4.1: Easton Broad Site 1, showing incursion of wind-blown sand into the lagoon. Photograph taken on 17 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England.

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Figure C5.1: Low resolution plan of the

1a locations of the 1b Reedland Marsh lagoons surveyed by Abrehart Ecology during the survey undertaken between 16 - 18 February 2012.

3

17

18 4

19

5

6a

6b

7

8

9

20

21

10 11 12 13 14

15

16

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Dunwich Figure C5.2: Aerial view of River Sluice Lagoons 1a and 1b at Reedland Marshes, Dunwich. The edge of the lagoons, as recorded during the February 2012 survey, is indicated by the red line

Lagoon 1a Dunwich River

Lagoon 1b

Photograph C5.1: Reedland Marsh lagoon 1a, looking north-west. In the foreground the shingle incursion can be seen clearly. Similar encroachment of shingle occurred at numerous sites. Photograph taken on 16 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England.

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Photograph C5.2: Reedland Marsh lagoon 1b, looking west showing shingle encroachment and high percolation water level. Photograph taken on 16 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England. Full site descriptions are presented in Section 3, Part 5 of the main text.

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Figure C5.3: Aerial view of Lagoon 3 at Reedland Marshes, Dunwich. The edge of the lagoons, as recorded during the February 2012 survey, is indicated by the red line.

Lagoon 3

Photograph C5.3: Reedland Marsh lagoon 3, looking west, showing shingle ridge and large volume of frass from recent inundation. Photograph taken on 16 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England. Full site descriptions are presented in Section 3, Part 5 of the main text.

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Figure C5.4: Aerial view of Lagoon 4 at Reedland Marshes, Dunwich. The

edge of the lagoons, as recorded during the February 2012 survey, is indicated by the red line.

Lagoon 4

Photograph C5.4: Reedland Marsh lagoon 4, looking west showing large amount of shingle encroaching on the site. Photograph taken on 16 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England. Full site descriptions are presented in Section 3, Part 5 of the main text.

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Figure C5.5: Aerial Dunwich River view of Lagoon 5 at Reedland Marshes,

Dunwich. The edge of the lagoons, as recorded during the February 2012 survey, is indicated by the red line.

Lagoon 5

Photograph C5.5: Reedland Marsh lagoon 5, looking west, showing encroachment of shingle on three sides of the lagoon. Photograph taken on 16 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England. Full site descriptions are presented in Section 3, Part 5 of the main text.

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Figure C5.6: Aerial view of Lagoon 6a and 6b at Reedland Marshes, Dunwich. The edge of the lagoons, as recorded during

the February 2012 survey, is indicated by the red line. Lagoon 6a

Lagoon 6b

Photograph C5.6: Reedland Marsh lagoon and 6b looking west showing large amount of shingle encroaching on the south and east of the site. Photograph taken on 16 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England. Full site descriptions are presented in Section 3, Part 5 of the main text.

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Figure C5.7: Aerial view of Dunwich River Lagoon 7 at Reedland Marshes, Dunwich. The edge of the lagoons, as recorded during the February 2012 survey, is indicated by the red line.

Lagoon 7

Photograph C5.7: Reedland Marsh lagoon 7, looking west showing high water level.. Photograph taken on 16 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England. Full site descriptions are presented in Section 3, Part 5 of the main text.

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Figure C5.8: Aerial view of Lagoon 8 at Reedland Marshes, Dunwich. The edge

of the lagoons, as recorded during the February 2012 survey, is indicated by the red line. Lagoon 8

Photograph C5.8: Reedland Marsh lagoon 8, looking south and west showing shingle encroachment and low percolation water level. Photograph taken on 16 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England. Full site descriptions are presented in Section 3, Part 5 of the main text.

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Figure C5.9: Aerial view of Lagoon 9 at Reedland Marshes, Dunwich. The edge of the lagoons, as

recorded during the February 2012 survey, is indicated by the red line. Lagoon 9

Photograph C5.9: Reedland Marsh lagoon 9, looking west showing high percolation water level. Photograph taken on 16 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England. Full site descriptions are presented in Section 3, Part 5 of the main text.

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Figure C5.10: Aerial view Lagoon 10 of Lagoons 10-14 at Reedland Marshes, Dunwich. The edge of the lagoons, as recorded during the February 2012

survey, is indicated by the red line.

Lagoon 13

Lagoon 14

Photograph C5.10: Reedland Marsh lagoon 10, looking west showing exposed mud. Photograph taken on 16

February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England. Full site descriptions are presented in Section 3, Part 5 of the main text.

Photograph C5.11: Reedland Marsh lagoon 11, looking west showing low water level and exposed mud. Photograph taken on 16 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England. Full site descriptions are presented in Section 3, Part 5 of the main text.

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Photograph C5.12: Reedland Marsh lagoon 12, looking west showing shingle encroachment and high percolation water level.

Photograph taken on 16 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England. Full site descriptions are presented in Section 3, Part 5 of the main text.

Photograph C5.13: Reedland Marsh lagoon 13, looking west showing low water level and exposed mud. Photograph taken on 16 February 2012 during the saline lagoon survey undertaken

by Abrehart Ecology for Natural England. Full site descriptions are presented in Section 3, Part 5 of the main text.

Photograph C5.14: Reedland Marsh lagoon 14, looking west showing low water level and exposed mud. Photograph taken on 16 February 2012 during the saline lagoon survey

undertaken by Abrehart Ecology for Natural England. Full site descriptions are presented in Section 3, Part 5 of the main text.

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Figure C5.11: Aerial view of Lagoon 15 at Reedland Marshes, Dunwich. The edge of the lagoons, as recorded Lagoon 15 during the February 2012 survey, is indicated by the red line.

Photograph C5.15: Reedland Marsh lagoon 15, looking west showing expanding lagoon and salt marshes. Photograph taken on 16 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England. Full site descriptions are presented in Section 3, Part 5 of the main text.

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Figure C5.12: Aerial view of Lagoon 16 at Reedland Marshes, Dunwich. The edge of the lagoons, as recorded during the February Lagoon 16 2012 survey, is indicated by the red line.

Photograph C5.16: Reedland Marsh lagoon 16, looking south to north showing high water level. Photograph taken on 16 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England. Full site descriptions are presented in Section 3, Part 5 of the main text.

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Figure C5.13: Aerial view

of Lagoons 17 and 18 at Reedland Marshes, Dunwich. The edge of the lagoons, as recorded during the February 2012 survey, is indicated by the

red line.

Lagoon 18

Photograph C5.17 : Reedland Marsh lagoon 17 (above) and lagoon 18 (to right), looking west showing low water level and exposed mud. Photograph taken on 18 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England. Full site descriptions are presented in Section 3, Part 5 of the main text.

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Figure C5.14: Aerial view of Lagoon 19 at Reedland Marshes, Dunwich. The edge of the lagoons, as recorded during the February 2012 survey, is indicated by the red line.

Lagoon 19

Photograph C5.18: Reedland Marsh lagoon 19, looking north showing high water level and expanding area of open wate r. Photograph taken on 18 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England. Full site descriptions are presented in Section 3, Part 5 of the main text.

Photograph C5.19: Reedland Marsh lagoon 19, looking south showing expanding area of open water. Photograph taken on 18 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England. Full site descriptions are presented in Section 3, Part 5 of the main text.

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Figure C5.15: Aerial view of Lagoons 20 and 21 at Reedland Marshes, Dunwich. The edge of the lagoons, as recorded during the February 2012 survey, is indicated by the red line.

Lagoon 20

Lagoon 21

Photograph C5.20: Reedland Marsh lagoon 20, looking south showing expanding area of open

water. Photograph taken on 18 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England. Full site descriptions are presented in Section 3, Part 5 of the main text.

Photograph C5.21: Reedland Marsh lagoon 21, looking south showing expanding area of open water. Photograph taken on 18 February 2012 during the saline lagoon survey undertaken by Abrehart Ecology for Natural England. Full site descriptions are presented in Section 3, Part 5 of the main text.

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Saline lagoon survey

Benacre NNR and

Suffolk Coast NNR,

February 2012.

Survey carried out by Toby R. Abrehart FLS

Dr Simon J. Forster abrehart ecology Pound Farm Low Road Great Glemham Suffolk IP17 2DQ Tel: 01728 663282 - 07798 941555 e-mail: [email protected]

Abrehart Ecology Natural England