Inventory of Eelgrass Beds in Hampshire and the Isle of Wight 2014

Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014

Section One: Report Version 6: May 2014

Zostera marina Paul Naylor

Hampshire and Isle of Wight Wildlife Trust would like to thank the following, who have provided funding, data, advice, support and time in the production of this report and coollection of data:

Natural England, Esmeé Fairbairn Founddation, Pig Shed Trust, Southern Inshore Fisheries Conservation Authority, Sussex Inshore Fisheries Conservation Authority, Hampshire County Council, Sita Trust, Ken Collins and Jenny Mallinson (University of Southhampton), Roger Herbert (University of Bournemouth), Anne Marston (Isle of Wight County Council)), Ian Ralphs (Hampshire Biodiversity Records Centre), The Wildlife Trusts, Jenni Tubbs, Chris Wood (Seasearch, Marine Conservation Society), Neil Garrick-Maidment (The Seahorse Trust), Colin Froud (Divercol), Val Gwynn (Country Wild Services), Lorraine Hooldstock, Torbay Coast and Countryside Trust, Dorset Environmental Records Centre, Solent Forum, Shelley Vince, Jessica Craig, Wanda Mills, Environment Agency, Ed Rowsell (Chichestter Harbour Conservancy), Iain Vincent, , Lucy Martin, Adam Johnson, Rebecca Oliver, Vicky Ashcroft, Rachel Fine, Martin Waareham, Steve Read, and Richard Unsworth, Ben Jones, Rosemary McCCloskey, and Jo Peters (Seagrass Ecosystem Research Group, University of Swansea).

Hampshire and Isle of Wight Wildlife Trust would also like to thank all of the volunteer surveyors who took part in both the scuba diving and intertidal surveys conducted to gather data for this project.

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshirre and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. i This document should be cited as:

Maps reproduced by Hampshire and Isle of Wight Wildlife Trust (Ordnance Survey licence no. 100015632) with the permission of Her Majesty's Stationery Office, Crown Copyright 2014. Unauthorised reproduction infringes Copyright and may lead to prosecution or civil proceedings.

Front cover by Paul Naylor.

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For information on how to obtain further copies of this document and accompanying data please contact Hampshire & Isle of Wight Wildlife Trust: [email protected].

Executive Summary

The aim of this inventory is to provide a baseline of knowledge on the current Zostera (eelgrass) populations along the coasts of Hampshire and the Isle of Wight. It is primarily aimed at conservation agencies and organisations, coastal and marine planners and anyone responsible for making decisions that could affect the coastal and near shore environments. It is designed to raise awareness of the importance of Zostera, assist in future survey, research and monitoring of Zostera populations and to contribute to conservation plans and development proposals. The inventory consists of a report section and a data section. The report section (Section One) summarises the biology and ecology of Zostera, current threats, conservation and management options, and survey and monitoring techniques. It also outlines the need for further work. The data section of the inventory (Section Two) comprises of site based maps and survey summary forms that provide further information on surveys carried out and basic site information. All maps should be used with reference to the survey summary forms to help prevent misinterpretation.

Contents

1. Report aims and objectives...... 1 2. An introduction to the Solent Seagrass Project……………………………………. 2 3. Site characterisation…………………………………………………………………….. 3 4. Biology of Zostera 4.1. Taxonomic status and morphology………………………………………………6 4.2. Growth and reproduction………………………………………………………… 8 4.2.1. Vegetative growth……………………………………………………………… 9 4.2.2. Sexual reproduction…………………………………………………………… 10 4.3. Environmental requirements 4.3.1. Light………………………………………………………………………………11 4.3.2. Substrate…………………………………………………………………………12 4.3.3. Exposure…………………………………………………………………………12 4.3.4. Salinity……………………………………………………………………………12 4.3.5. Temperature……………………………………………………………………. 13 4.3.6. Nutrients……………………………………………………………………….... 14 4.3.7. Zonation……………………………………………………………………….... 14 5. Ecological significance of seagrass 5.1. Sediment stabilisation…………………………………………………………….. 15 5.2. Productivity………………………………………………………………………… 15 5.3. Water quality and nutrient cycling……………………………………………….. 16 5.4. Carbon acquisition…………………………………………………………………. 16 5.5. Associated species…………………………………………………..……………. 17 5.5.1. Epiphytes and other algae…………………………………………………….. 18 5.5.2. Invertebrates……………………………………………………………………. 18 5.5.3. Fish………………………………………………………………………………. 18 5.5.4. Wildfowl………………………………………………………………………….. 19 5.6. “Biological guardians”……………………………………………………………... 19 5.7. Non-ecological and historical goods and services……………………………... 20 6. Threats to Zostera 6.1. Natural threats……………………………………………………………………....20 6.1.1. Weather…………………………………………………………………………..21

6.1.2. Grazing………………………………………………………………………….. 21 6.1.3. Wasting disease………………………………………………………………... 22 6.2. Anthropogenic threats…………………………………………………………….. 24 6.2.1. Coastal development…………………………………………………………... 24 6.2.2. Water quality and pollution……………………………………………………. 24 6.2.3. Physical damage……………………………………………………………….. 27 6.2.4. Competition from non–native species …………………………….………….. 28 6.2.5. Climate change…………………………………………………………………. 30 7. Distribution of seagrasses 7.1. Global distribution………………………………………………………………… 30 7.2. UK distribution…………………………………………………………………….. 31 7.3. Solent distribution 7.3.1. Historic distribution……………………………………………………………. 34 7.3.2. Current distribution……………………………………………………………. 36 8. Conservation status of Zostera 8.1. International conservation status 8.1.1. The Convention on the Conservation of European Wildlife and Natural Habitats (The Bern Convention)……………………………….. 41 8.1.2. The Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR)………………………….. 42 8.1.3. Convention on Wetlands (Ramsar)………………………………………….. 43 8.1.4. EC Directive on the conservation of wild birds (EC Birds Directive 79/409/EEC)…………………………………………………………. 43 8.1.5. EC Directive on the Conservation of natural habitats and of wild fauna and flora (EC Habitats Directive 92/43/EEC)………………….. 44 8.1.6. Solent European Marine Site………………………………………………… 47 8.2. National conservation status……………………………………………………. 47 8.2.1. Wildlife and Countryside Act 1981…………………………………………... 47 8.2.2. Biodiversity Action Plans (BAPs)…………………………………………….. 48 8.2.3. A UK Marine Act……………………………………………………………….. 51 9. Management options for Zostera beds……………………………………………... 52 9.1. Boat mooring management……………………………………………………... 53 9.2. Waste management for boats…………………………………………………... 53

9.3. Fishing activity management……………………………………………………. 48 9.3.1. Voluntary agreements…………………………………………………………. 54 9.3.2. Byelaws…………………………………………………………………………. 55 9.3.3. Artificial reefs…………………………………………………………………… 56 9.4. Restoration of Zostera beds……………………. ……………………………..... 56 10. Survey and monitoring techniques…………………………………………………… 58 11. Future survey, research and conservation recommendations………………….. 66 11.1 . Increased surveying and monitoring…………………………………………… 66 11.2 . Management and conservation……………………………………………….... 68 12. References……………………………………………………………………………….... 70 13. Appendix 1: Characteristics and morphology of Zostera species…………….... 86

1. Report aims and objectives

The principal aim of this report is to provide a baseline of knowledge on the current Zostera (eelgrass) populations along the coasts of Hampshire and the Isle of Wight. It is primarily aimed at conservation agencies and organisations, coastal and marine planners and anyone responsible for making decisions that could affect the coastal and nearshore environments. It is designed to raise awareness of the importance of Zostera, assist in future survey, research and monitoring of Zostera populations and to contribute to conservation plans and development proposals.

In order to achieve the above aim, this report has the following objectives:

 Provide an introduction to the biology and ecology of Zostera, detailing species taxonomy, habitat requirements, conservation importance and distribution.  Outline current threats and impacts faced by Zostera.  Detail current conservation status and relevant conservation designations.  Outline management options for Zostera beds.  Outline and review survey methodologies for Zostera data collection.  Make future survey, research and conservation recommendations.  Provide references and a bibliography of further useful reports.  Provide site maps of Zostera beds in Hampshire and the Isle of Wight with accompanying summary sheets detailing locations, surveys conducted and data gathered. These will include historic and current data.

In 2002, the Environmental Records Centre for Cornwall and the Isle of Scilly produced a report on the location and conservation of eelgrass beds in Cornwall and the Isles of Scilly. In 2004, the Devon Biodiversity Records Centre and Dorset Environmental Records Centre produced an inventory of eelgrass in Devon and Dorset. This report uses these previous reports as a framework and extends the coverage along the south coast of England.

This report (Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report) provides an overview on the available information regarding eelgrass, its biology, ecology, distribution, threats and impacts, and conservation and management options. It also outlines the need for further work. The information draws heavily on three previous reports, Davison and Hughes (1998), Tubbs (1999), and Black and Kochanowska (2004).

Section Two of the Inventory of eelgrass beds in Hampshire and the Isle of Wight holds the Zostera data amassed for the Solent. It includes site based maps of where Zostera has been found since the project started in 2006. Data pre-dating 2006, including historical and anecdotal data, has been removed in this version of the inventory maps for clarity but previous versions are available from the Hampshire and Isle of Wight Wildlife Trust. Each site is accompanied by a survey summary form that provides further site information and details the surveys carried out, and include information on pre-2006 surveys. All maps should be used with reference to the survey summary forms to help prevent misinterpretation.

2. An introduction to the Solent Seagrass Project

This Inventory of eelgrass beds in Hampshire and the Isle of Wight forms part of a wider project focusing on eelgrass beds in the area. The Solent Seagrass Project was initiated in 2006 with funding from the Sita Trust, Hampshire County Council and Environment Agency and aimed to:

1. Undertake survey work to improve knowledge of the distribution, extent, health and biodiversity of seagrass beds in the Solent, 2. Raise awareness of seagrass beds amongst stakeholders and the public, 3. Produce a seagrass inventory for Hampshire and Isle of Wight, based on published studies, past surveys, casual records and other sources of information, 4. Encourage reporting of seagrass occurrence in the Solent by the public, as a means of raising awareness and locating other possible seagrass sites.

In the years that the project has been running a series of awareness raising resources have been produced, including leaflets, recording forms, display panels and interpretation panels. A documentary DVD has also been produced, which highlights the importance of eelgrass, the threats it faces and the survey and conservation work being undertaken.

Widespread surveying has been conducted using a variety of methods including towed video, intertidal and diving surveys. Much of the surveying has been done with the aid of volunteers and specialist seagrass survey training courses have been developed and delivered to assist with this. The survey data gathered has been included within this inventory.

If further information is required on the Solent Seagrass Project, its aims and outputs, many of which are publicly available, please contact Hampshire and Isle of Wight Wildlife Trust.

3. Site characterisation

This report focuses on the Zostera beds off Hampshire and the Isle of Wight. The area encompassing the northern Isle of Wight and the mainland coast is known as the Solent, which includes Chichester Harbour, the eastern half of which is in West Sussex (Figure 1). As the Zostera in this area of Chichester Harbour forms an important part of the whole system, data on it is also included in this report. The area encompassing the southern Isle of Wight tends to be more exposed than the Solent and dominated by chalk reefs and cliffs. No confirmed records of Zostera exist from this area and so it is not discussed further.

The Solent is one of the few major sheltered channel systems in Europe and the whole area is unique in Europe in oceanographic terms (Fowler, 1995). It was formed during the melts of the last Ice Age, which drowned the Solent River system that once flowed east between what is now the Isle of Wight and mainland Hampshire and West Sussex (Tubbs, 1999). The flooding of this river valley resulted in a relatively shallow area of sea about 40 km long from east to west, with a width of about 4 km in the western Solent and about 10 km at the eastern end. Within the Solent, tidal streams in the main channel range from 2.5 kn in the east to 4 kn

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 3 in the west (Webber, 1980). The waters are characterised by high levels of turbidity reaching a maximum of 45 mg/L but typically containing ~18 mg/L of suspended solids. (EMU Ltd, 2005).

Figure 1. The Hampshire and Isle of Wight coasts with the Solent boundaries marked as a red dashed line. © Solent Forum.

Numerous estuaries and natural harbours were formed during the flooding of the river valley, the largest of which are Portsmouth, Langstone and Chichester. These harbours effectively operate as a single system, comprising of connected intertidal basins drained at low water by complex networks of channels and creeks. On the Isle of Wight, the most significant sheltered areas are Newtown Harbour and the estuaries of the Yar, Medina and Wootton Creek. The predominantly eastward longshore drift has lead to the formation of spits and bars at the entrance to many of the estuaries and harbours. The deposition of sediments in these sheltered areas has given rise to extensive mud and sand flats, with the mudflats being extremely soft and therefore making access difficult (Tubbs, 1999).

The complex shape of the Solent, its varying geology, many rivers, unusual tidal cycle and its location on the transition between the warm ‘Lusitanian’ waters of the western Channel and the cold ‘Boreal’ waters of the Eastern Channel have meant a great diversity of habitats and biodiversity (Jones et al., 2004). This has given rise to many features of international, national and regional conservation importance. Almost the entire coast on both the northern Wight and the Hampshire side is designated as either a Special Area of Conservation, Special Protection Area or Site of Special Scientific Interest. Under the Marine and Coastal Access Act 2009, 127 sites around England have been recommended for Marine Conservation Zone status with designation due in 2013-16. There are five recommended (MCZs) in the Solent area, all of which include seagrass habitat. Four of these, The Needles, Yarmouth to Cowes, Norris to Ryde, and Bembridge, are included in the tranche of sites to be publically consulted on in January 2015.

The Solent has attracted a great deal of economic development with shipping, sailing, fisheries and marine aggregate extraction all taking place. The land area surrounding the Solent is highly urbanised, and the river basins predominantly agricultural. All these activities have influenced the physical, chemical and biological state of the Solent. It is considered to have high levels of tri-butyl tin and some other metals and polycyclic aromatic hydrocarbons. Portsmouth, Langstone and Chichester Harbours have shown symptoms of eutrophication with excessive macroalgal growth on mudflats. These sites have been designated as Sensitive Areas under the Urban Waste Water Treatment Directive (Jones et al., 2004). Agricultural run–off and inputs from the wider Channel furthers nutrient loading.

The sheltered nature of much of the Solent and its harbours and estuaries, the deposition of soft sediments and the availability of nutrients can all benefit the growth of Zostera. However, the urbanisation, industry and water quality, notably in relation to turbidity, can limit its success.

4. Biology of Zostera

4.1. Taxonomic status and morphology

Seagrasses are a small group of angiosperms (flowering plants) found in the shallow waters of all continents except Antarctica. They are believed to be derived from terrestrial plants which returned to the sea through a series of gradual and progressive steps of acclimation to shallow freshwater, then brackish waters and finally fully saline conditions. They are a unique group in that they are the only flowering plants able to function and reproduce under conditions of permanent or cyclic submergence in saline water.

There are approximately 60 species of seagrasses occurring globally, with five occurring in the UK, two species of tassel weed (Ruppia spp.) and three species of eelgrass (Zostera spp.). This report deals only with UK species belonging to the Zostera genus.

Zostera, although considered to be temperate, is very widespread and also occurs in tropical climates (Hemminga and Duarte, 2000). Its taxonomy under the Angiosperm Phylogeny Group system (APG, 1998) is as follows:

Clade – Monocots Order – Alismatales Family – Zosteraceae (eelgrass family) Genera – Zostera (eelgrass)

The three Zostera species occurring in the UK are:

i. Zostera marina (common eelgrass) ii. Zostera angustifolia (narrow leaved eelgrass) iii. Zostera noltii (dwarf eelgrass, syn. Z. noltei, Z. nana)

There is some confusion with regard to the taxonomy of this group, particularly surrounding Z. angustifolia. Recent DNA sequencing research supports the hypothesis that Z. marina and Z. angustifolia are in fact variants of a single species. Information from Dr Fred Rumsey of the Department of Botany, Natural History Museum, detailed in Black and Kochanowska (2004) states:

‘Following molecular and some morphological work completed as an unpublished NHM/Imperial College M.Sc. project, my belief is that Z. angustifolia should not be regarded as a good species but should be considered an ecotype of Z. marina. There is no discontinuity in leaf width and from limited flowering material seen, no correlation with stigma:style length. Stace, in his 2nd edition, leans towards the recognition of Z. angustifolia as a variety. Z. angustifolia is now best treated as Z. marina L. var. angustifolia Hornem. That means that two currently accepted infraspecific taxa in Zostera marina are Z. marina var. marina and Z. marina var. angustifolia.’

Zostera angustifolia can also be difficult to identify accurately when surveying as it can be confused with the other two species. It has traditionally been distinguished from Z. noltii and Z. marina by differences in morphology, reproductive strategy and habitat use. However, these characteristics are known to vary depending on habitat and season. Finer leaved forms of Z. angustifolia have been confused with Z. noltii and vice versa, and wider leaved forms confused with Z. marina and vice versa (Robinson, 2003).

Despite this confusion and difficulty with identification, Z. angustifolia is regarded as a distinct species in this report, as it is still currently referred to as such in most British and Irish texts, and is recorded as a distinct entity locally.

In terms of morphology, all seagrass plants, regardless of species, are structurally similar in that they all consist of ramets (units) comprised of a bundle of leaves attached to a root- rhizome matrix. All three Zostera species have the same broad characteristics:

 Vertical, strap-like blades with either no cutinous layer or a very thin one.  Single chlorophyllous cell layer (the epidermis).  A thick and colourless aerenchyma layer below the epidermal layer, with large air canals running the blade length, making leaves buoyant.  Rhizomes, 2 to 5 mm in diameter, that grow within the sediment with numerous roots attached. Rhizomes produce leaf nodes spaced 1 to 3.5 cm from which leaves sprout. Rhizomes often serve as a storage area for starch.  Roots sprouting from rhizomes that include a continuation of the air canals with root hairs allowing uptake of nutrients from the sediments.  Produce flowering shoots, generally shorter than sterile shoots.

For a more detailed description of the three species with their key identification characteristics and morphology see Appendix 1 and Stace (1997).

4.2. Growth and reproduction

The root-rhizome system of a seagrass plant grows colonially, resulting in the lateral expansion of patches. Zostera growth is seasonal in temperate regions, occurring during the spring and summer, concurrently with increasing irradiance and water temperature (Hemminga and Duarte 2000). In Britain, growth generally occurs during the spring and summer, from April to September. Under particularly suitable conditions, Zostera plants can form extensive and dense stands, often being referred to as meadows or beds. Zostera marina (common eelgrass) is the largest plant of the genera. It is able to form dense beds with trailing leaves sometimes in excess of 1 m long. Zostera noltii (dwarf eelgrass) is a much smaller species, producing narrower leaves up to 20 cm long (OSPAR, 2005).

Flowering is also dictated by increases in irradiance and water temperate and so generally occurs in late spring (Hemminga and Duarte 2000). However, sexual reproduction is thought to make only a minor contribution to bed extension, with the majority accomplished by vegetative growth. Z. marina can have an annual or perennial life cycle. Once again water temperature is thought to be a major determining factor in which phenotype is present, with

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 8 subtidal plants usually displaying a perennial life cycle, and many intertidal populations displaying annual life cycle (Kuo and den Hartog 2006).

The following summary of eelgrass growth is adapted from Davison and Hughes (1998).

4.2.1. Vegetative growth

Zostera invests a large proportion of its resources in the maintenance of rhizomes and roots. The underground mat of horizontal rhizomes branches during growth, producing vertical leaf shoots, which are responsible for the lateral expansion of patches. Short pieces of rhizome that break off the parent plant and are carried away by currents may generate new plants if deposited on a suitable substratum (Olesen and Sand-Jensen, 1994). Eelgrass populations can therefore expand either by the vegetative growth of shooting rhizomes that have survived the winter, or sexually, by production of seed (see Section 4.2.2).

Subtidal Z. marina beds in the UK are perennial and are believed to persist almost completely as a result of vegetative growth rather than by seed production. In intertidal populations of Z. noltii and Z. angustifolia, new leaves appear in spring and the eelgrass meadows develop over the intertidal flats during the summer. Leaf growth ceases around September or October (Brown, 1990), and leaf cover begins to decline during the autumn and over the winter. Intertidal plants may experience a complete loss of foliage, dying back to the buried rhizomes. Natural leaf-fall, grazing by wildfowl and a few specialized invertebrates and removal by wave action are the major factors contributing to this seasonal disappearance of the leaves. In perennial populations, the rhizomes survive the winter to produce new leaves the following spring, while in annual populations, both the leaves and rhizomes die. In contrast to the two intertidal species, sublittoral Z. marina beds can remain green throughout the year, as summer leaves that are shed in the autumn are generally replaced with smaller winter leaves.

4.2.2. Sexual reproduction

Flowering is a rare event for most seagrass species, where typically < 10 % of the shoots flower each year (Marbà et al., 2004). In all three species, flowers and seeds are generally produced in summer (May to July) and early autumn (September) (Brown, 1990; Tubbs and Tubbs, 1983). Zostera flowers are highly adapted to optimize pollination efficiency in an aquatic environment (Ackerman, 1983). The male flowers release long filamentous strands of pollen into the water. The density of these pollen filaments enables them to remain at the depth at which they were released for periods of up to several days, so increasing the likelihood of the pollen filaments encountering receptive stigmas. After fertilization, the seed develops within a green membranous wall which photosynthesises, producing a small bubble of oxygen that is trapped inside the seed capsule. Eventually this forces the capsule wall to rupture, releasing the mature seed. The seeds generally sink and are dispersed by currents, waves and, possibly over short distances, on the feet of birds. However, Churchill et al. (1985) found that the bubble can adhere to the seed’s coat, increasing its buoyancy and consequently its likelihood of dispersal.

Relatively high temperatures (above 15 oC) appear to be required for flowering and seed germination, suggesting that sexual reproduction does not play a major role in the life history of Z. marina in northern latitudes. In comparison, the Z. angustifolia and Z. noltii intertidal beds in the UK rely on a combination of vegetative growth and seed set. Z. angustifolia appears to rely more on seed set while Z. noltii appears to rely more on vegetative growth (Cleator, 1993; Rae, 1979; van Lent and Vershuure, 1994a, b).

4.3. Environmental requirements

4.3.1. Light

All seagrasses rely on light for photosynthesis and therefore the amount of light available will govern where the plants are found. Compared to many species of seaweed, seagrasses need high light levels and are therefore found in relatively shallow conditions where light levels will be greatest. A minimum light requirement for seagrass has been identified by Duarte (1991) as 10-20 % of surface light. Ability to tolerate low light levels is species specific and related to their ability to store carbohydrates in the rhizomes. This suggests that species such as Z. noltii, which has smaller rhizomes than Z. marina, will have limited capacity to tolerate low light levels (Tomasko and Dawes, 1989), and thus this will be a contributing factor to zonation of the species.

In the UK, eelgrass most commonly occurs at depths less than 4 m (Davison and Hughes, 1998). Beyond this depth, reduced light leads to inhibited photosynthesis and therefore reduced growth, making plants smaller and beds sparser until ultimately the plants can no longer survive. Depth distribution of seagrass is site specific and will vary depending on the water clarity at that site. In the very clear waters of Ventry Bay, south-west Ireland, Z. marina occurs in a continuous bed from 0.5 m to 10 m, and in patches to a maximum depth of 13 m (Whelan and Cullinane, 1985), probably the deepest-growing Zostera in north-west Europe. Off the north-west American coast, the maximum depth at which eelgrass has been recorded growing is 6.5 m. However, in the extremely clear water off the Californian coast, eelgrass has been found growing at depths of more than 30 m (Teal, 1980).

The Solent is considered to have high turbidity levels reaching a maximum of 45 mg/L but typically containing ~18 mg/L of suspended solids. (EMU Ltd., 2005). As a result, eelgrass will not reach the depths it may do in areas characterised by greater water clarity. Zostera depth in relation to attenuation of light in the Solent was investigated by Vince (2007), who found a compensation depth of 2 m. Plants living at or above this 2 m point would be subject to water

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 11 depths significantly greater than 2 m depending on the stage of the tidal cycle, with depths of > 4.5 m above Chart Datum being experienced at high tide.

4.3.2. Substrate

Zostera species are rooting plants and so require soft sediment. They are found in areas dominated by mud, sand and gravely sand. The Solent, with its many estuaries, harbours and sandy shores on the north coast of the Isle of Wight, has a substantial resource of soft sediments and therefore has an abundance of potentially suitable Zostera habitat.

4.3.3. Exposure

Zostera plants require a degree of shelter from strong currents, tidal flows and large waves. High exposure leads to sediments being mobilised, increasing turbidity, and plants being uprooted. Few studies have been conducted to assess the maximum current speed Zostera marina plants are able to tolerate. However, de Boer (2007) reported water current speeds of < 0.25 m s-1 are required for beds to achieve 50 % coverage, and Kopp (1999, referenced within Koch et al., 2006) noted that loss of Z. marina was to be expected if water currents exceeded 4 m s-1. Flows above this velocity cause too much physical stress on the plant and inhibit its capability to grow. Also, limited water movement can result in the accretion of soft sediment and therefore lead to a favorable substrate for Zostera. As a result, Zostera is most common in harbours, estuaries, saline lagoons and open shores sheltered from the prevailing winds. However, some water movement will increase leaf biomass, width and canopy height as a result of supplying fresh nutrients.

4.3.4. Salinity

Zostera species are considered euryhaline as they occur in a wide variety of salinities. This accounts for their frequent occurrence in estuaries. Z. marina is one of the most eurybiont seagrass species. It is able to tolerate salinities ranging from freshwater to 42 psu under laboratory conditions (Phillips and Meñez, 1988), and has been found in waters with salinities

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 12 ranging from 10 to 42 psu (Biebl and McRoy, 1971). The effects of salinity on subtidal populations of Z. marina is summarised in Davison and Hughes (1998). Z. marina populations that are not subjected to lowered salinity produce few or no reproductive shoots (Giesen et al., 1990), and laboratory studies indicate that maximum germination in Z. marina occurs at 1 psu salinity (Hootsmans et al., 1987). This low salinity figure is surprising as Z. marina occurs almost exclusively in fully saline conditions, despite it being able to tolerate near freshwater conditions. However, field studies indicate that germination in Z. marina occurs over a range of salinities and temperatures (Churchill, 1983; Hootsmans et al., 1987).

4.3.5. Temperature

In contrast to its independence with regard to salinity, Z. marina is considered stenothermic. Its optimum temperatures are 10-20 C, and outside this range there is no activity and growth, despite the plant itself being able to tolerate water conditions of -6 C and substratum temperatures of 40.5 C under laboratory conditions (Phillips and Meñez, 1988). Z. marina flowering is greatest at 15-20 C (Rasmussen, 1977).

Zostera angustifolia and Z. noltii are more adapted to intertidal conditions than Z. marina and can tolerate a broader temperature range. Their upper shore habitat renders them more exposed to extremes of cold or heat when exposed at low tide or in very shallow bays. Den Hartog (1987) suggested that cold winters can result in significant losses. Critchley (1980) reported that intertidal Zostera beds at Bembridge, Isle of Wight were damaged by frost.

With regard to desiccation, Z. noltii is typically found on areas of intertidal sediments that drain well, suggesting has a tolerance to desiccation, while Z. angustifolia dominates areas where water is retained (Duncan, 1991; Fox et al., 1986). Zostera marina grows mainly in the shallow sublittoral, and is less resistant to desiccation.

4.3.6. Nutrients

Nutrient uptake by Zostera from the water column occurs through the leaves and from the interstitial water via the rhizomes (Davison and Hughes 1998). Laboratory experiments have suggested that moderate nutrient enrichment of the sediments can stimulate the growth of Z. marina shoots (Roberts et al., 1984). In the field, Tubbs and Tubbs (1982) observed that an increase in Zostera beds paralleled an increase in the nutrient input to the Solent.

However, excessive nutrient enrichment, causing eutrophication, has been cited as a factor in the decline of Zostera beds in many parts of the world (Shepherd et al., 1989). Increased nutrient loading can lead to a proliferation of Ulva spp. (recently reclassified from Enteromorpha spp.) and den Hartog (1994) reported that at Langstone Harbour, the growth of a dense blanket of Enteromorpha radiata in 1991 resulted in the loss of 10 ha of Z. marina and Z. noltii, and that by the summer of 1992, Zostera was entirely absent.

Nutrient enrichment can also lead to phytoplankton blooms which in turn can result in an increase in turbidity. This has been implicated in the loss of seagrass beds in Australia (Shepherd et al., 1989).

4.3.7. Zonation

Due to differences in tolerance to temperature, desiccation, salinity and other factors, zonation between Zostera species is often apparent. Zostera marina has the least tolerance to temperature and desiccation and is therefore most commonly found in subtidal conditions, although on low spring tides it can still experience exposure. Zostera noltii and Z. angustifolia are both found in the intertidal zone due to their increased tolerance to variable salinities and temperatures. However, Z. angustifolia appears to prefer to have its base in standing water and is therefore more commonly seen in depressions on the shore where water is retained when the tide recedes. Zostera noltii can commonly be found on raised mounds that dry out at low tide.

5. Ecological significance of seagrass

5.1. Sediment stabilisation

The structure of seagrass plants helps to stabilise sediment and prevent erosion. Seagrass canopy provides a barrier that reduces wave and current velocity, thus increasing rates of sedimentation and reducing re-suspension. The root and rhizome network further aids the prevention of re-suspension of sediment particles by binding the sediment together and stabilising it. Their effectiveness in stabilising sediment and reducing erosion was demonstrated during the 1930s, when significant declines of Zostera led to the erosion of approximately 1 m of mud from areas in Langstone Harbour (Tubbs, 1999). As well as providing stability, the penetration of seagrass roots into the sediment allows oxygen to penetrate into otherwise impermeable sediment, thus providing an aerated, stable habitat favourable to burrowing animal communities.

5.2. Productivity

Seagrass meadows are the most productive of shallow sedimentary environments. Production figures of 20 g C m-2 per day have been recorded for some species, comparable to terrestrial crops (Barnes and Hughes, 1995). More commonly, production rates average at 0.5–2 g C m-2 day-1 (Duarte & Chiscano, 1999). This high primary productivity rate allows the development of a rich associated fauna as it provides a vital food source for fauna that feed directly on the plant or their epiphytic colonies. Seagrass canopy also provides a larger surface area for epiphyte and epifaunal community establishment, thus aiding secondary production. Seagrass leaves are slow to decay, and upon senescence and uprooting by storms they can be deposited on the shore as dense drifts, or carried by currents to supply food webs geographically removed from the coastal zone (den Hartog, 1987). For example, leaves have been found at depths of up to 8000 m where they provide nutrients for bacteria and can help support the deep-sea ecosystems (Barnes and Hughes, 1995).

5.3. Water quality and nutrient cycling

Seagrasses are known to positively influence water quality. In areas where dense beds exist they can utilise excess nutrients, releasing them back into the system slowly when the seagrass tissue decomposes. This effectively filters the water and maintains the balance of nutrients, thus reducing the possibility of eutrophication and phytoplankton blooms (Spalding et al., 2003). The plants also increase sedimentation and reduce turbidity, as particles are trapped amongst the leaves and settle to the seabed, helping to improve water clarity. Moore (2004) found that in areas of Chesapeake Bay where Zostera occurred, inorganic nitrogen levels were reduced by 73 % when compared to areas where no Zostera was present. In this study, reduced levels of suspended particles were also noted within beds. An unvegetated site that previously supported Zostera demonstrated little capacity to reduce measurable levels of suspended particles or nutrients, and re-suspension of bottom sediments contributed to higher levels of suspended particle concentrations and turbidity.

5.4. Carbon acquisition

The turnover time of seagrass leaf and root biomass is between two weeks and five years, with rhizomes sometimes persisting for millennia before being broken down (Kennedy and Björk, 2009). Seagrass detritus is bound to the sediment within the seagrass habitat or transported to deeper ocean habitats, thus providing a major carbon sink - long-term carbon burial equates to 83 g C m-2 yr-1 and this translates to global storage rates of between 27 and 40 x 1012 g C yr-1 (Kennedy and Björk, 2009). Fourqurean et al. (2012, as cited in Slezak 2012) estimated seagrass to capture 27.4 million tonnes of carbon each year (27.4 x 1012 g C yr-1 ) which could result in up to 19.9 billion tonnes of carbon (19 x 1015 g) currently being stored within seagrass plants and the top meter of sediment beneath them. The slow break down of seagrass material makes the role of seagrasses in the oceanic carbon budget proportionally more significant than expected from their relatively low areal cover of 0.3 million km2 globally. They represent only ~ 1 % of total ocean production, and yet provide ~ 15 % of total ocean carbon storage (Duarte and Cebrián, 1996; Hemminga and Duarte, 2000;

Kennedy and Björk, 2009; Mateo et al., 2006). Seagrasses also act as a carbon sink by utilising it during the photosynthetic process.

Seagrasses are considered to be a more efficient carbon sink than forests as unlike forests, which release their stored carbon after approximately 60 years, seagrass ecosystems have been capturing and storing carbon since the last ice age (Fourqurean et al., 2012, as cited in Slezak 2012). This makes the global seagrass habitat loss over the last century, which has been estimated at 29 % (a rate of ~ 1.5 % yr-1), more worrying as the loss has resulted in an estimated 299 million tonnes (299 x 1012 g yr-1) of carbon being released back into the environment each year (Fourqurean et al., 2012, as cited in Slezak 2012).

5.5. Associated species

Seagrass plants alter their habitat from a relatively homogenous soft sediment to a sheltered habitat with high structural complexity, rich food supply, and protection from predators. Seagrass habitats are therefore able to support a more biologically diverse assemblage of species in comparison to unvegetated areas. High species diversity associated with seagrasses, compared to surrounding habitats, is well documented and some of these species are of commercial or conservational value (Larkum et al., 1989; Spalding et al. 2003).

A combination of factors will determine the community composition of an eelgrass bed; eelgrass species, substratum, salinity, water currents and location will all have an influence. The three Zostera species are found on similar substrata but in different tidal zones. Species diversity tends to be highest in populations of Z. marina as conditions are most stable, being predominantly subtidal and perennial. Biodiversity tends to be lower in beds of Z. angustifolia and Z. noltii as conditions fluctuate with tides, freshwater input, exposure and dieback. (Jacobs and Huisman, 1982).

5.5.1. Epiphytes and other algae

Zostera beds are generally rich in epiphytes, which take advantage of eelgrass leaves as a suitable substratum for attachment. Conversely, eelgrass beds tend to be poor in associated macroalgae due to shading effects, but if these beds are more patchy and sparse, brown and red macroalgae is common. As stated previously, beds of Z. angustifolia and Z. noltii are often associated with sea lettuce (Ulva spp.), especially in areas of nutrient enrichment.

5.5.2. Invertebrates

Due to the presence of epiphytes, grazers are abundant in eelgrass beds, notably small gastropods such as Hydrobia species and Rissoa membranacea. High productivity attracts filter feeders and cockles, mussels and scallops can all be found around the base of the plants and anemones attached to leaves, notably snacklocks anemones (Anemonia viridis). Worms including the sand mason (Lanice conchilega), the lugworm Arenicola marina and the fan worm Myxicola infundibulum are found in the sediments.

Crustaceans are common and eelgrass beds in the Solent have traditionally been productive and important shrimping and prawning grounds (Tubbs, 1999). Other crustaceans commonly found include crab species such as European spider crabs (Maja squinado), the spindly spider crabs Macropodia and Inachus species, masked crabs (Corystes cassivelaunus), green shore crabs (Carcinus maenas), common hermit crab (Pagurus bernhardus) and velvet swimming crabs (Necora puber).

Other invertebrates associated with eelgrass beds include cuttlefish Sepia officinalis and Sepiola atlantica, which often lay their eggs on the leaves, and several species of sea slug.

5.5.3. Fish

Previous studies have examined fish community structures in seagrass meadows and found high abundances and diversities, with as much as 30 % of species found to be of commercial

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 18 value (Burchmore et al., 1984). A high proportion of fish encountered are juveniles, confirming the accepted belief that meadows are used as nursery grounds due to productivity and the protection from currents and predators afforded by dense canopy (Adams, 1976). Fish commonly found include bass (Dicentrarchus labrax), pollack (Pollachius pollachius), bib (Triopterus luscus), wrasses (Labridae spp.), gobies (Gobiidae spp.), fifteen-spined sticklebacks (Spinachia spinachia), various pipefish species (Syngnathidae spp.), and the native seahorses Hippocampus hippocampus and Hippocampus guttulatus.

5.5.4. Wildfowl

Although few species graze directly on eelgrass in the UK, it is an important food source for several species of wildfowl, including the Brent goose (Branta bernicla bernicla), wigeon (Anas Penelope), and teal (Anas crecca), which feed on the intertidal beds when the tide is out. The importance of eelgrass in the diet of these wildfowl was apparent when eelgrass populations declined in the 1930s due to wasting disease and a concomitant decline in these wildfowl was also noted (Tubbs and Tubbs, 1983). Ogilvie and Matthews (1969) reported that in Europe, the decline of the population of Brent geese (to approximately 25 % of its pre- 1930s level) strongly paralleled the decline in Zostera following the wasting disease epidemic.

In some areas it appeared that intertidal Zostera species were not as severely affected by the wasting disease as Z. marina (see Section 6.1.3), and it was suggested that Brent geese were forced to switch their feeding to intertidal beds of Z. angustifolia and Z. noltii. However, in the Solent, Z. angustifolia and Z. noltii underwent a serious decline along with Z. marina (Tubbs, 1999) and as a result Brent geese diversified their feeding habits to include saltmarsh, cereals and grasses on pasture and amenity land such as parks. These areas remain of great importance for feeding (Wicks, 2001).

5.6. “Biological guardians”

Fluctuations in seagrass distribution, both by reductions in maximum depth limits and localised cover, and by widespread regional loss, can be used as indicators of degrading

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 19 water quality. Unlike other environmentally sensitive habitats, such as coral reefs and mangroves, they are not limited to narrow geographical regions (tropics) but are found worldwide and so lend themselves well to both small-scale and large-scale trends (Orth et al., 2006).

5.7. Non-ecological and historical goods and services

Socio-economic uses of seagrasses include material for mat and basket making, insulation, stuffing in mattresses and upholstery, packing and thatch, as well as fertilizer, and fodder and bedding for livestock. From medieval times to the 19th Century, Z. marina was used in the production of glass, soap, and alum (a colourless, soluble double sulphate of potassium or aluminium used in the manufacture of pigments), and in the production of salt (e.g. in The Netherlands once intertidal peat deposits had been exhausted) (Hemming and Duarte, 2000; van Geel and Borger, 2005). Zostera marina is now used by the cosmetics industry in skin cleansing products.

6. Threats to Zostera

6.1. Natural threats

Zostera beds are subject to natural change, both on a seasonal and interannual basis. These fluctuations may be precipitated by sediment transport regimes, grazing and weather events. Zostera beds are known to be spatially dynamic; they are capable of causing rapid sediment accretion but are also subject to periodic erosion and movement. Beds change constantly in shape and area in response to local variations in patterns of sediment erosion and accretion, which they themselves may initiate by altering water velocity and sediment mobility at their margins (Tubbs, 1999). This can lead to constantly advancing and receding leading edges. Naturally occurring changes can take place at a range of scales, with effects ranging from small alterations to Zostera coverage or density, to destruction of entire beds over large geographic areas (Davison and Hughes, 1998).

6.1.1. Weather

Severe weather events can damage eelgrass populations. They can be easily uprooted, for example by powerful waves during storms. This is often evidenced on the strandline when mats of uprooted eelgrass can be seen after storm events. Storms can also mobilise the sediments which can increase sedimentation and water turbidity, resulting in reduced water quality and light penetration. Photosynthetic efficiency is therefore reduced and smothering of shoots by sediment is more likely.

Extremes of temperature may also damage intertidal Zostera when exposed, especially if cold conditions cause freezing of the sediments and frost damage to foliage. Critchley (1980) observed frost damage to Zostera on the Isle of Wight. Rasmussen (1977) suggested that at temperatures above 20 C there is little growth or flowering in Z. marina, so high temperatures may limit viability.

6.1.2. Grazing

Eelgrass populations may fluctuate as a result of grazing pressure. Although few animals feed directly on Zostera, some wildfowl will, notably Brent geese, teal and wigeon. The grazing pressure they exert will depend on their numbers, which can fluctuate year to year. Wigeon nip off the blades of eelgrass whereas Brent geese tear up parts of the plant and the material they do not consume floats away on the surface. Both leaves and below ground rhizomes may be targeted (Davison and Hughes, 1998).

Grazing wildfowl can consume a high proportion of the available standing stock of Zostera. Portig et al. (1994) found that in Strangford Lough, 65 % of the estimated biomass of Zostera was consumed but that up to 80 % was disturbed by their feeding activity. Tubbs and Tubbs (1983) reported that Brent geese grazing resulted in the cover of Z. marina and Z. noltii being reduced from 60 - 100 %. Zostera is able to withstand typical grazing pressure, however, if another stress is added, the combination may be sufficient to substantially damage the long-

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 21 term viability of beds (Tubbs and Tubbs, 1982). Den Hartog (1994) found that Brent geese may have removed the few remaining healthy Z. marina and Z. angustifolia plants that survived in Langstone Harbour after they had been overwhelmed by growth of Ulva spp.

6.1.3. Wasting disease

Perhaps the single largest natural threat to Zostera populations has been the periodic outbreak of an infection known as wasting disease. This disease, which destroyed leaf and rhizome tissue, eventually leading to death (Rasmussen, 1977), wiped out extensive areas of Z. marina in the North Atlantic in the early 1930s. It was first recorded on the coast of North America in 1930, and by 1932 it had been reported at Roscoff, Brittany, the Netherlands and the UK (Tubbs, 1999). The first symptoms of wasting disease are brown spots occurring on the leaves, which darken and spread, leaving the leaf blackened when it would eventually die and be shed. The rhizomes were similarly affected.

The ecological effects of wasting disease in the 1930s were very damaging. Stauffer (1937) recorded a disappearance of one third of invertebrates present before the decline in Washington, and Rasmussen (1977) compiled evidence from previous studies in Danish fjords that suggested a similar trend. In a review of seagrass community studies, Pollard (1984) stated that during the deterioration of Z. marina many species of fish declined in areas affected by wasting disease and Tubbs and Tubbs (1983) wrote of the reduction in numbers of wildfowl, which feed directly on eelgrass. The declines in biodiversity as a result of a loss of Zostera demonstrates how ecologically important these beds are.

It was originally thought that the fungus Labyrinthula macrocystis was responsible for wasting disease (Renn, 1937). However, as L. macrocystis normally occurs at low levels in association with Zostera plants, it was subsequently suggested that the fungus was just a symptomatic feature of some other stress, leading to a proliferation of the fungus, or limiting the ability of Zostera to cope with its potential effects. Possible stressors suggested include pollution (Short et al., 1988), and abnormal temperature and salinity fluctuations (Ralph and Short, 2002). However, the slime mound Labyrinthula zosterae has now been identified as the

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 22 primary causal agent of wasting disease in Z. marina (Short et al., 1987), and not, as previously thought, simply an opportunistic fungus that infects already deteriorating plants and accelerates their decay (Ralph and Short, 2002). It should be noted that blackened leaves are not necessarily indicative of wasting disease and there can be other causes, such as toxins or annual dieback.

The wasting disease epidemic of the 1930s seemed to predominantly affect Z. marina beds, with Z. noltii appearing to be relatively unaffected (Rasmussen, 1977), even though L. zosterae is known to infect Z. noltii, and possibly other seagrass species (Hemminga and Duarte, 2000). Muehlstein et al. (1988, 1991) showed that Labyrinthula does not generally cause disease in low salinities, and this may explain why the intertidal Zostera species, Z. angustifolia and Z. noltii, appear to be relatively unaffected by wasting disease. This said, Tubbs (1999) gathered evidence that suggested that populations of Z. noltii and Z. angustifolia in the Solent did significantly decline in numbers during the 1930s, thus suggesting that these species are not immune.

The recovery of Zostera beds was slow and did not begin until the mid-1930s. In the Solent recovery was likely to have been later, with beds in Langstone Harbour not beginning to increase in size until around 1960. Beds in Chichester and Portsmouth Harbours may not have begun recovering until even later (Tubbs, 1999). Recovery of eelgrass beds after disturbance is often slow, as once removed, the sediment is often mobilised, increasing turbidity and decreasing suitability for recolonisation. Recovery may have been further slowed by new, smaller scale outbreaks of wasting disease in the 1980s and 1990s. Early in the 1980s, wasting disease reappeared on the east coast of North America and between 1987 and 1992 symptoms appeared in Europe, including Chichester, Langstone and Portsmouth Harbours (Tubbs, 1999). Even today, many Zostera populations in the North Atlantic have still not fully recovered from the wasting disease of the 1930s, possibly due to anthropogenic impacts.

6.2. Anthropogenic threats

As well as showing many natural fluctuations, Zostera populations are also heavily influenced by human activities. Seagrasses require shallow sheltered environments and this often puts them in direct competition with humans, who also favour these areas for coastal development, access and industry.

6.2.1. Coastal development

Coastal development, which may include land reclamation for building, coastal defence works, port, harbour and marina development, maintenance and capital dredge schemes and cables and pipelines, can all have serious impacts on Zostera beds. Impacts can result from either the direct removal of plants and suitable habitat, such as from dredging through beds or building directly on to them, or through interference with the normal sediment and water movement processes, which can lead to unsuitable growing conditions through increased turbidity, currents or nutrient and/or toxin input (see Section 6.2.2). Other impacts can result from physical damage caused by some fishing practices, including bait digging, mooring and anchoring of boats.

6.2.2. Water quality and pollution

Water quality has significant impacts on Zostera beds. Impacts may be acute, such as an oil spill leading to sudden loss of Zostera, or chronic, such as long term exposure to low levels of toxins that reduce plant functioning and growth.

Oil Oil pollution may damage Zostera beds, both by sticking to it and smothering it, preventing it from getting enough light, and also due to its toxic nature. Davison and Hughes (1998) summarised the research conducted in to effects of oil pollution on Zostera. Jacobs (1980) reported blackening of Z. marina leaves for 1 - 2 weeks after the Amoco Cadiz spill but observed that the growth, production and reproduction of the plants were not affected. Some

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 24 of the treatments for oil spills, such as dispersant, are even more toxic than oil. Holden & Baker (1980) conducted studies in Milford Haven, Wales and found that a single application of oil, dispersant or oil / dispersant mix, could reduce growth of intertidal Zostera. Howard (1986) found that Zostera exposed to oil and dispersant mixes showed rapid death of the leaves and a significant decline in cover one week after application. By eight weeks, cover had been reduced from 55 % to 15 %. The main findings of the Milford Haven research are generally similar to the conclusions reached by other researchers, namely that pre-mixed oil and dispersants have the greatest potential for killing seagrasses, whereas contact with oil alone may reduce or halt growth. Howard et al. (1989) concluded that if oil cannot be prevented from covering eelgrass beds, then dispersant treatments must be avoided in order to minimise the risk of a partly dispersed oil mixture affecting the eelgrass. It was advised that oil coverage on eelgrass beds should be left untreated and the oil layer allowed to disperse by tidal action.

Herbicides Herbicides in the marine environment can result from agricultural run-off or antifouling paints used on pontoons, pilings and boat hulls to prevent algal growth. Herbicides commonly found in coastal waters include Diuron and Irgarol. Haynes et al. (2000) assessed the toxicity of Diuron to the tropical seagrasses Halophila ovalis and Zostera capricorna in Australia and found environmentally occurring levels significantly limited photosynthesis. The toxicity of Irgarol towards Z. marina in the UK has been assessed by Scarlett et al. (1999) who found that reduced photosynthesis and growth occurred at concentrations that have been documented to occur in coastal waters (Chesworth et al., 2004). Chesworth et al. (2004) demonstrated that Diuron and Irgarol can interact and reduce the concentrations necessary to limit photosynthesis and growth in Z. marina. As a result of the threats posed to seagrasses and marine algae, both Irgarol and Diuron are banned from use in antifouling paints. However, paints containing these compounds can still be applied abroad on ships that visit the UK.

Nutrient enrichment All plants, including Zostera, require a certain concentration of nutrients for optimal growth. In some areas a lack of nutrients may limit growth and in the Solent, Tubbs and Tubbs (1983) found that rapid increases in the extent of Zostera beds paralleled increased volumes of sewage entering the local areas. However, it was concluded that there was no direct evidence of a causal relationship. If excessive nutrient loading occurs, such as from sewage outfalls or agricultural run-off then eutrophication, the excessive proliferation of planktonic or benthic algae, may result. This is most common in partially enclosed areas, such as harbours and estuaries, where dilution and flushing is least. Many studies have correlated seagrass loss with increased growth of epiphytic, blanketing or floating algae, often as a result of eutrophication (e.g. Borum, 1985; Burkholder et al., 1992; Orth and Moore, 1983; Shepherd et al., 1989; Wetzel & Neckles, 1986). An increase in planktonic algae will increase turbidity and decrease the amount of light available for eelgrass plants. Increases in epiphytic and benthic algae can effectively smoother eelgrass plants. Den Hartog (1994) reported that at Langstone Harbour, the growth of a dense blanket of Enteromorpha radiata in 1991 resulted in the loss of 10 ha of Z. marina and Z. noltii, and that by the summer of 1992, Zostera was entirely absent. Anecdotal evidence of smothering of Zostera by green algae was found by Hampshire and Isle of Wight Wildlife Trust during surveys at Portsmouth Harbour in 2009. Some intertidal Z. marina patches had blackened leaves beneath a mat of green algae, possibly as a result of deoxygenation caused by the overlying algal mat.

As well as the effects of eutrophication, the nutrients themselves may damage eelgrass plants. Burkholder et al. (1992) found that nitrate enrichment could cause death or decline in Z. marina and it was suggested that high internal nitrogen concentrations caused a metabolic imbalance. Nutrient enrichment may also increase vulnerability to wasting disease. Buchsbaum et al. (1990) found that the levels of phenolic compounds were lowered under conditions of nutrient enrichment and these compounds play an important role in providing Zostera with defence against infection, including wasting disease. Burkholder et al. (1992) found that plants from enriched mesocosms succumbed to infection by Labyrinthula macrocystis, while plants in the control mesocosm remained healthy.

6.2.3. Physical damage

Eelgrass plants are vulnerable to physical damage as they are not robust and their root- rhizome system is usually situated within the top 20 cm of the sediment (Fonseca, 1992) and so can be easily disturbed by a range of activities. If beds are disturbed, this can lead to increased patchiness and sediment erosion, precipitating further plant loss. Physical damage can result from a variety of activities.

Coastal development Damage resulting from coastal development activities is discussed in Section 6.2.1.

Trampling Trampling may be caused by recreational activities such as walking, horse-riding and off-road driving. It may also result from coastal construction or clean–up works. After the Sea Empress oil spill, near Milford Haven in Wales, damage to Zostera appeared to be limited to those plants living on areas of shore traversed by clean-up vehicles (SEEEC, 1996).

Fishing A range of fishing activities have resulted in damage to eelgrass beds in the UK. In 2004, the pump–scoop cockle dredging fleet, which uses a water injection system to remove cockles from the sediments, was banned from operating in the Solent European Marine Sites (see Section 8.1.5) due to damage observed in the eelgrass bed at Ryde on the Isle of Wight. In the Solway Firth, the introduction of mechanical dredges to gather scallops led to wide scale losses of Zostera and the practice was outlawed in 1994 due to concerns it may totally eradicate the beds (Solway Firth Partnership, 1996). Dredging for scallops and clams has also led to the damage of Zostera beds. In 2006 scallop dredgers were seen operating in eelgrass beds in Tor Bay, Devon and evidence of damage to the beds was documented (Flint, 2006). Clam dredging activity has frequently been seen in Cams Bay and in other areas in Portsmouth Harbour, such as east of Pewit Island and at Wicor. Dredge tracks have subsequently been seen through eelgrass beds, mudflats and salt marsh. Furthermore, saltmarsh and eelgrass plants have been found covered in a layer of silt, possibly as a result

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 27 of dredging activity destabilising and mobilising sediment (Pers. obs.). Bait digging can also damage eelgrass beds. The soft sediments where eelgrass grows are also areas of high polychaete abundance and so potentially attractive for bait diggers. Bait digging in eelgrass beds will uproot plants and if the spoil is not replaced but heaped up, it may smoother plants and when the tide returns the sediment will be mobilised and increase turbidity.

Recreational boating Recreational boating can lead to physical damage in eelgrass beds. Moorings in eelgrass beds damages plants when chains drag and swing on the seabed at low tide. Anchoring can also result in the same kind of damage and if the anchor drags, it can uproot plants. Rhodes et al. (2006) found evidence that swing moorings not only lead to losses of seagrass, creating bare sand patches, but also have a significant effect on the infaunal macroinvertebrate communities present in Z. marina beds, causing polychaete assemblage composition to differ to that found in natural sand patches within seagrass beds. Wash from powerboats, jet skis and other waterborne craft can also lead to physical damage. The hovercraft that runs between Portsmouth and Ryde on the Isle of Wight has created a scar through the eelgrass bed (Pers. obs.).

6.2.4. Competition from non-native species

Non–native, or alien, species often arrive attached to ships hulls or in ballast water, or are imported for some reason and escape in to the natural environment. In the Mediterranean the introduction of the green algae Caulerpa taxifolia from the Caribbean has led to extensive loss of seagrass. In the UK there are two species which are considered to pose some degree of threat to Zostera due to competition for space.

Spartina anglica Spartina anglica, a cord grass commonly found in saltmarsh, is a fertile hybrid resulting from inter–breeding of the non–native Spartina alterniflora and the native, S. maritima. Spartina alterniflora is thought to have arrived in the UK at Southampton Water via ships ballast water in the late 1800s. The hybrid Spartina anglica is fast growing and has high fecundity, its rapid

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 28 spread was accelerated further by planting in an effort to stabilise coastal sediments (Davison and Hughes, 1998). Percival et al. (1997) reported a reduction in Zostera coverage at Lindisfarne, Northumberland, due a combination of change in sedimentation pattern and encroachment by S. anglica.

Sargassum muticum The invasive brown algae Sargassum muticum (commonly known as wireweed or Japanese weed) is often found within and in close proximity to Z. marina beds. This seaweed, naturally occurring in Japanese waters, is thought to have been introduced to European waters with commercial introductions of oysters in Northern France. Its natural dispersal mechanisms led to its arrival in the UK and it was first found attached in the Solent at Bembridge in 1971 (Farnham et al., 1973). It is now widespread along the south coast, up to Suffolk on the East Coast and Strangford Lough, Northern Ireland on the west. Sargassum muticum can have both positive and negative implications on the habitats in which it becomes established. The hypothesis that S. muticum actively completes with Z. marina for space (e.g. Tubbs (1999) reported that in the Solent, S. muticum and Z. angustifolia compete for space in lower shore lagoons) is generally no longer thought to be the case. This is supported by Fowler (1995) who observed that despite the shading caused by the extensive S. muticum canopies in the Solent and Isle of Wight area, there did not appear to be any associated declines in Zostera. However, the presence of S. muticum can be detrimental as it can prevent regeneration of a eelgrass bed after a disturbance by colonizing areas from which Z. marina has retreated before it can re-establish (Critchley, 1980; Farnham et al., 1981; den Hartog, 1987). This has been demonstrated within the Solent at the Bembridge lagoons, Isle of Wight, where S. muticum spoorlings colonised newly exposed substratum only after the frost-induced die-back of Z. marina (Fletcher and Fletcher, 1975). Furthermore, it has been suggested that Z. marina aids the establishment of S. muticum by trapping drifting fragments and allowing them to settle, thus providing an opportunity for them to anchor (Tweedley et al., 2008).

6.2.5. Climate change

Climate change poses significant threats to Zostera populations. A warming of air and sea temperatures, a rise in sea level and an increase in storm events have occurred in the UK over the last decades. Jenkins et al. (2007) state that air temperature over central England has risen by 1 ºC since the 1970s. Sea surface temperatures have risen by 0.7 ºC during the same period, with warming occurring at a faster rate in the English Channel and southern North Sea than within Scottish continental shelf waters. Sea level has risen by 1 mm per year and there has been an increase in storm events over the last few decades, with this trend predicted to continue. The long-term effects that climate change is likely to have on seagrass habitats were reviewed by Short and Neckles (1999). There are several potential impacts resulting from climate change. Increases in temperature may lead to waters exceeding the preferred temperature range. As stated previously, at temperatures above 20 C there is no activity and growth in Z. marina (see Section 4.3.5) (Rasmussen, 1977), so increased sea temperature will affect the plants ability to grow and reproduce. Increases in extreme weather events, such as hurricanes, will increase physical damage such as uprooting beds, and cause a decline in water quality (see Section 6.1.1). Sea level rise may reduce the amount of habitat available for Zostera, as light penetration decreases with depth reduces and so previously suitable habitats may become too deep to allow adequate photosynthesis. Suitable habitat loss is likely to be compounded by ‘coastal squeeze’ (the coastline is unable to retreat as a result of costal developments and defenses).

7. Distribution of seagrasses

7.1. Global distribution

Seagrasses have a broad global distribution with species growing in shallow waters of all continents except Antarctica. The United Nations Environment Programme’s World Conservation Monitoring Centre (www.unep-wcmc.org) has produced a comprehensive global

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 30 seagrass atlas (Green and Short, 2003) which should be consulted for detailed information on global distribution.

The genus Zostera has the largest latitudinal range of any of the seagrass genera, extending from the Equator to the sub-Antarctic and to the Arctic. The global distribution of the Zostera species discussed in this report are summarised in Davison and Hughes (1998):

 Zostera marina is confined to the northern hemisphere but is widespread throughout the Atlantic and Pacific, extending northwards to approximately 60 oN and southwards to approximately 35 oN. In the eastern Atlantic it extends from the Arctic Circle (it is the only seagrass species to extend this far north) to Gibraltar, including the Mediterranean Sea.  Zostera angustifolia has only been recorded around the British Isles, Denmark and Sweden. This apparently limited distribution is a reflection of the disputed taxonomic status of this form (see Section 4.1).  Zostera noltii does not extend as far north as Z. marina and is restricted to the Atlantic, including the Mediterranean Sea. It extends from southern Norway to the tropic of Cancer.

7.2. UK distribution

Populations of seagrass occur on all UK coasts with concentrations in south and west of England, eastern England and Scotland. All three UK species of Zostera are considered Nationally Scarce (it is only present in 16 - 100 of the UK’s ten km square units) and distribution has not recovered from the outbreak of wasting disease in the 1930s. The extent of recovery of Zostera populations in the UK is confused. Butcher (1941a, b) reported that recovery of the beds had begun by 1933 and was quite rapid, with some beds fully recovered within a few years of the 1930s epidemic. However, Tubbs (1999) suggested that the disease continued to affect Zostera populations until the mid-1940s and that recovery did not really begin until the 1950s. He reported that Z. marina has not fully recolonised the estuaries in southern and eastern England where it was once abundant, but that there are numerous

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 31 small beds on the Channel coast from the Isles of Scilly to the Isle of Wight, concluding that only 20 of Britain’s 155 estuaries have eelgrass meadows more than 1 hectare in extent.

Davison and Hughes (1998) summarised UK distribution up to that time. It was suggested that prior to the outbreak of wasting disease in the 1920s, the majority of shallow and intertidal mudflats were dominated by eelgrass (Tubbs, 1999). Butcher (1934) conducted the first comprehensive survey of eelgrass beds in the South and East coasts of England for the Government in response to the wasting disease declines. He concluded that since 1917 Z. marina had become scarce and restricted to sheltered sites such as lagoons. Zostera angustifolia appeared to have become the most common Zostera species from this time. The distribution of Z. noltii remained stable, although this was still a relatively uncommon species.

The current UK distribution is summarised in Table 1, adapted and updated from Davison and Hughes (1998), who state there is still a need for additional accurate estimates of extent, obtaining this information is a high priority in the development of a conservation plan for Zostera biotopes in the UK.

Table 1. Summary of Zostera distribution in the UK, adapted from Davison and Hughes, 1998.

SITE NAME ZOSTERA SPECIES Z. marina Z. angustifolia Z. noltii Zostera spp. Scotland Sound of Arisaig  Loch Maddy  Moray Firth*  Cross Boarder sites between Scotland and England Solway Firth  Berwickshire & North Northumberland Coast  England Morcambe Bay  Humber Estuary  The Wash and North Norfolk Coast  Essex Estuaries  Maplin Sands, North Thames Estuary  Solent and Isle of Wight Lagoons: Langstone Harbour  Chichester Harbour  Portsmouth Harbour  Calshot  Beaulieu  Isle of Wight, NW and NE Coasts  Poole Harbour  Studland Bay  Chesil & Fleet  Weymouth  Exe Estuary  Tor Bay  Plymouth Sound and Estuaries  Fal & Helford  Isles of Scilly Complex  Cross Boarder Site England & Wales Severn Estuary  Wales Pembrokeshire: Skomer  Milford Haven  Lleyn Peninsula & the Sarnau  Northern Ireland Strangford Lough  Dundrum Bay  Carlingford Lough  Lough Foyle  * The Cromarty Firth is considered to have the largest Zostera population in Britain.

7.3. Solent distribution

7.3.1. Historic distribution

The Solent populations of Zostera are some of the best recorded in the country, largely as a result of the work of Colin and Jenni Tubbs, who have gathered historic survey and sightings data and conducted extensive surveying during 1970s and 1980s. Much of the information summarised here comes from Tubbs (1999). Solent Zostera populations reflect the national fluctuations, seeing significant decreases in once extensive meadows as a result of wasting disease in the early 1930s, with subsequent partial recovery and further mortality from more recent outbreaks of disease and anthropogenic impacts.

In the Solent, historically, Zostera was found as extensive beds up the Lymington River and Southampton Water, as well as in the harbours of Portsmouth, Langstone and Chichester. Some of the earliest records from the Solent are from Gilpin (1791), who described the Lymington River as having “banks clothed with seagrass that gives them the air of meadows when the tide retires”, going on to label seagrass beds as the “savannahs of the shore”. Butcher (1934) wrote that before the outbreak of wasting disease, in Southampton Water, eelgrass was formerly very large and abundant from Southampton up the River Hamble to Bursledon; along the opposite side from Eling south-eastwards and the Beaulieu and Lymington Rivers. Anecdotal evidence collected by Tubbs (1999) suggests prolific subtidal and intertidal Zostera beds in Portsmouth, Langstone and Chichester Harbours. The situation was similar on the Isle of Wight, with significant meadows recorded on the north east and north-west coasts.

At the appearance of wasting disease the beds rapidly disappeared. In Southampton Water, the once extensive beds were reduced to a few very small and isolated patches around Bursledon and Netley, with none remaining in the Lymington River (Butcher 1934). In Chichester Harbour only two small beds were reported by Butcher (1934), one south of Thorney Island and one at West Wittering. Beds on the Isle of Wight appeared to have faired a little better with both intertidal and subtidal populations surviving from Bembridge on the east to Yarmouth in the west, but beds in the Yar and Medina estuaries had gone. Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 34

In some locations around the UK, Zostera had reportedly recovered in the mid to late 1930s, but this doesn’t appear to have been the case in the Solent. By the late 1930s, Wadham (1940) stated that the Zostera beds on the Isle of Wight had disappeared. In the 1950s, the only Zostera beds known to remain on mudflats in the Solent were two small beds of Z. angustifolia and Z. noltii in Langstone Harbour, with one small patch of Z. marina on shingle, also within the Langstone. There were local reports that the Z. marina bed at Calshot Spit survived. On the Isle of Wight, sparse scattered beds of Z. noltii were reported and Z. marina was found around Foreland.

Recovery appeared to accelerate in the early 1960s. The two small intertidal beds in Langstone Harbour expanded. By 1979 they were estimated to be at 280 ha and by 1987 they had expanded further to 340 ha (Tubbs, 1999). In Chichester Harbour, Tittensor (1973) found no Zostera in 1972, but in 1979, Tubbs and Tubbs (1983) estimated Zostera at 130 ha. These beds were mapped again in 1987 and estimated at 220 ha (Tubbs, 1999). Zostera was also reported in Portsmouth Harbour by 1979. Following surveys in 1979, Tubbs and Tubbs (1983) estimated total areas of Zostera in the Solent (Table 2). Estimations of intertidal populations are likely to have been quiet accurate. The total area covered by deeper Z. marina populations may have been underestimated as surveys were carried out from the shore, so access to deeper beds would not be available and so could not have been accurately surveyed.

Table 2. Estimated areas of Zostera in the Solent in 1979, from Tubbs and Tubbs (1983).

SPECIES SUBSTRATE AREA (ha) Z. marina Firm sand or gravelly sand 54 Z. angustifolia and Z. noltii Soft mud 430-450 Z. noltii Firm sand or gravelly sand 19

In the late 1980s and early 1990s, Solent distribution again changed as a result of a new outbreak of wasting disease, with beds in Portsmouth, Langstone and Chichester Harbours being affected. By 1993, the formally extensive meadows at Nutbourne Inlet and the east side

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 35 of the Emsworth Channel in Chichester Harbour and those in Langstone Harbour to the east side of the main Channel were reduced to a few scattered and sparse residual patches (Tubbs, 1999). The Z. marina bed at Calshot was reported to have disappeared some time in the 1980s.

7.3.2. Current distribution

Seagrass remains absent in Lymington River, and beds present in Southampton Water are still vastly reduced and thought to now only occur only around Chilling. The Hamble has been recently and extensively surveyed and no seagrass was recorded. The beds in Langstone and Chichester Harbours continue to exist but may have been impacted by further outbreaks of wasting disease. Other significant populations occur at Portsmouth Harbour, Beaulieu and Calshot off Hampshire, Totland and Yarmouth on the north-west coast of the Isle of Wight and large beds extending down the north east coast of the Isle of Wight from Cowes to Bembridge.

Section Two of this inventory should be consulted for current distribution of Zostera in the Solent. Gaps in data from the early 1980s to the current day make meaningful comparisons of Zostera populations over the last 20-30 years difficult. Despite this, it does appear that Zostera populations in the Solent are steady or possibly increasing in some areas. The Calshot bed reported to have disappeared in the 1980s is once again present and possibly expanding. Zostera marina has been found in the Beaulieu Estuary where it was not recorded previously, although this may be because of difficulties of access requiring the use of underwater survey equipment which may not have been available to previous surveyors. At Chilling Beach, Southampton Water, a patchy but large bed of Z. noltii has also been surveyed by Hampshire and Isle of Wight Wildlife Trust in 2009 and 2010.

However, elsewhere there seems to be a declining trend. There are still Zostera beds in Langstone Harbour but, interestingly, some appear to have disappeared since the 1980s as beds off North Binness, Long and South Islands documented by Tubbs and Tubbs (1983) were not apparent in a 2004 survey by Ralphs (2004). In Chichester Harbour, wide-scale

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 36 losses, particularly in the eastern side, appear to have occurred (Pers. com. Rowsell, E., Chichester Harbour Conservancy). This said, surveys carried out by Hampshire and Isle of Wight Wildlife Trust in 2009, 2010 and 2013 of some locations within Chichester Harbour reported to have Zostera beds between 1995-2005 confirmed these are still present. Hampshire and Isle of Wight Wildlife Trust also surveyed large areas of Portsmouth Harbour in 2009 to 2013 as an effort to build on the very limited Zostera records for this area. It is unclear if the lack of verifiable records for Portsmouth Harbour up until 2009 indicates a disappearance of beds or a lack of survey effort. The 2010-2013 surveys for Portsmouth Harbour revisited several large Zostera beds recorded in 2009, as well as identifying new Zostera beds not previously recorded, and areas impacted by damaging fishing practices. In 2009, one Zostera bed in Cams Bay reduced in size from 3.1 ha to 2.5 ha (0.6 ha loss) on its seaward side, where there was also significant evidence of clam dredging activity. This data led to the introduction of an emergency byelaw in the area to protect the eelgrass beds against further damage. Evidence of other seagrass beds in the region being damaged by fishing activity resulted in ongoing discussions to decide if a similar byelaw encompassing a larger area should be implemented. However, this process was superseded by the introduction of three byelaws brought in to protect seagrass within the Solent European Marine Site (EMS) as part of our obligation to protect the key component sub-features and attributes of the Solent Maritime EMS, of which seagrass habitat is one (see Section 9.3.2).

On the Isle of Wight, where historic data is less complete than from the Hampshire coast, Zostera beds are extensive in some areas, notably Bembridge, Ryde, Wootton, Osborne Bay, Cowes, Bouldnor, Yarmouth and Totland. However, although Zostera was recorded at Newtown Bay in the 1970s and 1980s (Frazer, 1973; Tubbs and Tubbs, 1983), none was found in surveys carried out by the Hampshire and Isle of Wight Wildlife Trust in 2010.

In 2008, Zostera species coverage in the east and west Solent was conservatively estimated at ~ 200 ha (Collins, 2008). This estimate is much lower than Tubbs and Tubbs (1983) collective estimate of 503 - 523 ha (Table 2), although it is worth bearing in mind that Collin’s estimate does not include any Hampshire Zostera beds with the exception of those at Beaulieu and Calshot. Current total Zostera species coverage in the Solent is conservatively

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 37 estimated at 673.97 ha (Table 3). This is based on the largest estimates of Zostera coverage within the Solent using surveys carried out by Hampshire and Isle of Wight Wildlife Trust, the Environment Agency and Collins since 2006. This figure is assumed to be an underestimation of total area of seagrass in the Solent as it only includes beds surveyed since 2006 (as older records are no longer considered reliable for coverage estimates), and so there are likely to be some beds not included in this estimate. Furthermore, subtidal beds in particular are likely to have been underestimated due to the difficulties in accurately establishing seaward bed extent.

Many of the known beds need further survey to estimate area and bed boundary extent. Furthermore, some locations that are thought to host Zostera have had little or no survey work conducted there to confirm presence and extent. Therefore, current knowledge of the distribution of Zostera in the Solent is incomplete and this should be born in mind when consulting the data in the inventory, as the absence of seagrass records in an area does not necessarily mean it is not present.

Table 3. Estimated areas of Zostera in the Solent based on survey conducted by Hampshire and Isle of Wight Wildlife Trust, Collins (National Oceanographic Centre), and the Environment Agency since 2006.

LOCATION EELGRASS SURVEY AREA ESTIMATES (HA) HAMPSHIRE Southampton Water 28.84 Calshot & Stanswood Bay 42.58 Beaulieu 21.24 Langstone Harbour 103.71 Portsmouth Harbour 85.63 Chichester Harbour 116.08 ISLE OF WIGHT Cowes 27.1a Osborne & Wootton Bays 117.56 Ryde 84.56b Bembridge 2 Seagrove Bay, St. Helens & Priory Bay 10.26 Fort Victoria, Norton Spit & Yarmouth 18.24 Bouldnor 31.52 Colwell Bay 3.35 Totland Bay 8.4 Thorness Bay no estimate available Solent conservative estimated total: 673.97 ha a Collins, 2008. b partnership survey with Hampshire & Isle of Wight Wildlife Trust and Environment Agency.

8. Conservation status of Zostera

The ecological significance of Zostera means that it is of high conservation importance. It is included in many international and national conservation designations (both statutory and voluntary), not just as a habitat in its own right but also as a habitat that supports other conservationally important species such as wildfowl and seahorses.

The conservation designations of most relevance to Solent populations include Special Areas of Conservation (SACs), where it is considered an important feature, and Special Protection Areas (SPAs) where it provides an important source of food for Brent geese (see Section 8.1.5). They are also a key component sub-feature for the designation of the Solent Maritime European Marine Site (see Section 8.1.6). Seagrass is a Priority Habitat in the non–statutory Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 39

Biodiversity Action Planning Process, where maintaining the extent and distribution of seagrass beds in the UK is an overall objective (see Section 8.2.2), and also a habitat Feature of Conservation Importance (FOCI) under the Marine and Coastal Access Act 2009 which must designate an ecologically coherent network of Marine Conservation Zones (MCZs) (see Section 8.2.3).

It is beyond the scope of this report to provide a detailed critique of all of these conservation treaties and designations and their effectiveness in relation to Zostera conservation and as a result only the most important are discussed briefly in Sections 8.1 (international) and 8.2 (national). Their impact on Zostera has been discussed in more detail by Hocking and Tompsett (2002) and further information on them is readily available from sources such as the Joint Nature Conservation Committee.

As well as protection through conservation designation processes, various other management options are available. These may include boat mooring and anchoring restrictions, either statutory or through voluntary codes of conduct, agreements with local fishermen and bait diggers, improved awareness raising campaigns and restoration of degraded Zostera beds. One example is Studland Bay, Dorset, where Z. marina beds provide habitat for breeding populations of seahorses (both Hippocampus hippocampus and Hippocampus guttulatus). A voluntary No Anchor Zone was implemented between October 2009 and October 2011 as part of a study commissioned by The Crown Estate and Natural England to assess the effects of boat anchoring and moorings on the health of seagrass and associated marine life in the Bay. The study found that the difference in seagrass health between the volunteer no anchoring area and control area increased during the project and recommended further monitoring but the project was not continued (Seastar Survey Ltd, 2012).

Restoration through transplantation of plants has had varying levels of success depending on the methods adopted. Transplanting plants rather than attempting to re-seed areas seems to be the most successful but may only work with subtidal populations. Ensuring conditions in the site to be restored are suitable for Zostera growth is problematic but vital.

8.1. International conservation status

8.1.1. The Convention on the Conservation of European Wildlife and Natural Habitats (The Bern Convention)

The Bern Convention, more formally known as The Convention on the Conservation of European Wildlife and Natural Habitats was adopted in Bern, Switzerland in 1979, with the UK ratifiying it in 1982. The principal aims of the Convention are to ensure conservation and protection of wild plant and animal species and their natural. To this end the Convention imposes legal obligations on contracting parties, protecting over 500 wild plant species and more than 1000 wild animal species.

Annex I of the Bern Convention lists Zostera marina as a Strictly Protected Flora Species. With regard to Z. marina, this requires:

 Requisite measures to maintain the population.  The promotion of national policies for its conservation.  Planning and development policies to have regard to its conservation.  Appropriate and necessary legislative and administrative measures to ensure its conservation.  Appropriate and necessary legislative and administrative measures to ensure the special protection of Zostera marina. Deliberate picking, collecting, cutting or uprooting of such plants shall be prohibited.

To implement the Bern Convention in Europe, the European Community adopted Council Directive 79/409/EEC on the Conservation of Wild Birds (the EC Birds Directive) in 1979 (see Section 8.1.4), and Council Directive 92/43/EEC on the Conservation of Natural Habitats and of Wild Fauna and Flora (the EC Habitats Directive) in 1992 (see Section 8.1.5).

The Convention was implemented in UK law by the Wildlife and Countryside Act (1981 and as amended). As the inspiration for the EC Birds and Habitats Directives, the Convention had an

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 41 influence on the Conservation (Natural Habitats &c.) Regulations 1994, and the Conservation (Natural Habitats &c.) Regulations (Northern Ireland) 1995, which were introduced to implement those parts of the Habitats Directive not already covered in national legislation.

The Bern Convention also lists both species of seahorse known to occur in the UK, Hippocampus hippocampus and Hippocampus guttulatus. These species, notably H. guttulatus are thought to be strongly associated with eelgrass beds. The Bern Convention states that the deliberate damage to or destruction of breeding or resting sites is prohibited.

8.1.2. The Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR)

The Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR) was adopted in Paris, France in September 1992 and entered into force in March 1998. OSPAR replaced both the Oslo and Paris Conventions, with the intention of providing a comprehensive and simplified approach to addressing marine pollution other matters relating to the protection of the marine environment. The UK ratified OSPAR in 1998. Implementation in the UK is coordinated by the Department for Environment Food and Rural Affairs (Defra) Marine and Waterways Division, with contributions to OSPAR Committees by a variety of government departments.

Five strategies for directing the work have been adopted. Measures and programmes within the Biodiversity Strategy include the development of lists of species and habitats in need of protection, identification and selection of marine protected areas, and the prevention and control of adverse impacts from human activities.

OSPAR’s List of Threatened and/or Declining Habitats and Species includes Z. marina and Z. noltii, designated as Priority Habitats. Zostera angustifolia is not distinguished. As a priority habitat, assessments of Zostera will be carried out under the Joint Assessment and Monitoring Programme (JAMP). On the basis of these assessments, appropriate measures

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 42 will be adopted for its protection, or the attention of the competent authorities will be drawn to the need for such measures.

The Biodiversity Committee agreed a programme to map the distribution of Priority Habitats, in the UK, the JNCC have been helping with this and collating records of Zostera. However, for the Solent at least, these records are incomplete and are in need of updating with more recent survey data and new surveys conducted.

8.1.3. Convention on Wetlands (Ramsar)

The Convention on Wetlands, commonly known as Ramsar after the city it was agreed in, designates wetland sites of international importance. The Ramsar Convention has 164 contracting parties, including the UK which designated with first Ramsar sites in 1976. The emphasis for selection of sites is placed on importance to waterbirds and consequently many Ramsar sites are also Special Protection Areas (SPAs) classified under the Birds Directive (See Section 8.1.4). The UK now has 146 sites covering a total surface area of 1,276,852 ha. Zostera is mentioned as a noteworthy and nationally important species in these Ramsar sites.

In the Solent area there are three Ramsar sites known to support Zostera:

 Solent and Southampton Water.  Portsmouth Harbour.  Chichester and Langstone Harbours.

8.1.4. EC Directive on the Conservation of Wild Birds (EC Birds Directive 79/409/EEC)

In 1979, the European Community adopted Council Directive 79/409/EEC on the Conservation of Wild Birds, commonly referred to as the 'Birds Directive', in response to its obligations as a signatory of The Bern Convention (see Section 8.1.1). It has led to the designation of Special Protection Areas (SPAs), strictly protected sites that are classified for rare and vulnerable birds and for regularly occurring migratory species.

SPAs have been designated for species that feed on Zostera, including Brent geese, teal and widgeon, so as a result the Zostera beds benefit from a level of protection. SPAs in the Solent containing Zostera include:

 Solent and Southampton Water.  Portsmouth Harbour.  Chichester and Langstone Harbours.

8.1.5. EC Directive on the Conservation of Natural Habitats and of Wild Fauna and Flora (EC Habitats Directive 92/43/EEC)

In 1992 the European Community adopted Council Directive 92/43/EEC on the Conservation of Natural Habitats and of Wild Fauna and Flora, commonly referred to as the ‘Habitats Directive’, in response to its obligations as a signatory of The Bern Convention (see Section 8.1.1). The provisions of the Directive require Member States to introduce a range of measures including the protection of species listed in the Annexes; to undertake surveillance of habitats and species and produce a report every six years on the implementation of the Directive. The 189 habitats listed in Annex I of the Directive and the 788 species listed in Annex II, are to be protected by means of a network of sites. Each Member State is required to prepare and propose a national list of sites for evaluation in order to form a European network of Sites of Community Importance (SCIs). Once adopted, these are designated by Member States as Special Areas of Conservation (SACs), and along with Special Protection Areas (SPAs) classified under the EC Birds Directive, form a network of protected areas known as Natura 2000.

The Habitats Directive introduced for the first time for protected areas, the precautionary principle that projects can only be permitted having ascertained no adverse effect on the integrity of the site. Projects may still be permitted if there are no alternatives, and there are imperative reasons of overriding public interest. In such cases compensation measures will be necessary to ensure the overall integrity of network of sites. As a consequence of

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 44 amendments to the Birds Directive these measures are also to be applied to SPAs. Member States shall also endeavour to encourage the management of features of the landscape to support the Natura 2000 network.

In the UK the Directive has been transposed into national laws by means of the Conservation (Natural Habitats, &c.) Regulations 1994, commonly known as 'the Habitats Regulations’. Most SACs on land, freshwater areas and coastal areas (to mean low water) are underpinned by notification as Sites of Special Scientific Interest (SSSIs).

The Annex I coastal and marine habitats that are relevant to Zostera populations are:

 Sandbanks which are slightly covered by sea water all the time, of which Z. marina beds are classified as a subtype.  Estuaries.  Mudflats and sandflats not covered by seawater at low tide.  Coastal lagoons.  Large shallow inlets and bays.

Zostera beds are all considered to be important features of these habitat types. In the Solent there are three SAC’s that contain Zostera:

 Solent Maritime.  South Wight Maritime.  Solent and Isle of Wight Lagoons.

Where a SPA or a SAC incorporates subtidal and/or intertidal areas, they are referred to as an European Marine Site (EMS). The Solent European Marine Site (SEMS) comprises of:

 Solent Maritime Special Area of Conservation.  Solent and Southampton Water Special Protection Area & Ramsar Site.  Chichester and Langstone Harbours Special Protection Area & Ramsar Site.

 Portsmouth Harbour Special Protection Area & Ramsar Site.

Natural England provides advice on EMSs to other relevant authorities on the conservation objectives of the site and on operations which may cause deterioration of the natural habitats. Table 4 illustrates an extract from the advice given for the Solent EMS, used to measure favourable condition.

Table 4. Extract from Natural England’s advice given under Regulation 33(2) of the Conservation (Natural Habitats &c.) Regulations 1994 for the Solent European Marine Site.

ATTRIBUTE MEASURE TARGET COMMENT Extent of Extent (m2) of the No descrease in The extent of Zostera (eelgrass) beds is a Zostera beds. Zostera beds extent from an key structural component of the sediments measured suring the established and provides a long term integrated measure peak growth period baseline subject of environmental conditions across the (May to August) to natural change. deature, and is also particularly important in every three years being an internationally scarce and declining during the reporting habitat. The eelgrass beds provide a rich cycle. source of food for wintering wildlfowl and provide an important nursary area for fish. The extent and distribution of seagrass beds provides a long-term integrated measure of environmental conditions.

In November 2011 Southern Inshore Fisheries Conservation Authority (Southern IFCA) set up a Seagrass Working Group to aid the development of a management strategy to protect seagrass in the SEMS, and also potentially in the wider district, from detrimental impacts of the exploitation of sea fisheries resources, in particular, demersal mobile fishing gear (see Section 9.3 for more information).

8.1.6. Solent European Marine Site

Through designation and management of SACs and SPAs, the Solent EMS must protect wildlife habitats and species of European importance that are covered by tidal waters. These sites contain some of England’s most vulnerable marine wildlife and habitats. In August 2012, Defra announced a new approach to manage fishing activities with European Marine Sites (EMSs) to bring fisheries in line with other activities. The change in approach will promote sustainable fisheries while conserving the marine environment and resources, securing a sustainable future for both (see Section 9.3 for more information).

8.2. National conservation status

As well as international conventions that benefit Zostera, there are several national designations that can influence it conservation.

8.2.1. Wildlife and Countryside Act 1981

The Wildlife and Countryside act includes the provision for the designation of Sites of Special Scientific Interest (SSSI’s) with the objective of ensuring the national heritage of wild flora and fauna remains as large and diverse as possible. Designation is based upon criteria including size, diversity, rarity, fragility and naturalness. They extend to Mean Low Water and so are relevant only to intertidal populations of Zostera. Zostera is classified as nationally scarce and so is a notable feature in the designation of SSSIs. Most SSSIs in the Solent that contain Zostera are also designated as SPAs or SACs.

The Wildlife and Countryside Act also includes provision for the designation of Marine Nature Reserves (MNRs). The purpose of MNRs is to conserve marine flora and fauna and geological features of special interest, while providing opportunities for study of marine systems. They are the mechanism for the protection of nationally important marine areas. MNRs differ from SSSIs in that they can be designated below low water. Their designation Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 47 requires the agreement of statutory and voluntary bodies and interest groups. There are three designated MNRs in the UK: Lundy Island (England), Skomer Island (Wales) and Strangford Lough (Northern Ireland), there are none in the Solent. Skomer and Strangford Lough MNRs have Zostera populations within them.

Elsewhere, a number of voluntary Marine Nature Reserves (vMNRs) have been established by agreement between non-governmental organisations, stakeholders and user groups. These have no statutory basis and rely on education, awareness raising and voluntary agreements for management.

In April 2008 both species of UK seahorse, Hippocampus hippocampus and Hippocampus guttulatus, were added to the list of species protected under the Wildlife and Countryside Act. This means that not only is it now a criminal offence to purposefully harm or damage these fish, it is also an offence to damage their habitat. If the seahorses are found within a Zostera bed, the Zostera will receive a degree of protection by proxy. This may lead to planned coastal developments now being required to conduct surveys to ensure there are no seahorses present before the development can progress.

8.2.2. UK Biodiversity Action Plan (UK BAP)

The UK Biodiversity Action Plan (UK BAP) was a non–statutory process initiated by the UK Government in response to the Convention on Biological Diversity (CBD), signed in 1992 at the Rio Earth Summit. BAPs for Priority Species and Priority Habitats, that is those considered to be the most threatened and in need of conservation, were written to aid recovery, with national reports produced every 3 – 5 years to show how the UK BAP was contributing to the UK’s progress towards the significant reduction of biodiversity loss called for by the CBD. BAPs exist at a number of levels, with the overarching UK BAP linking to regional and local BAPs that work to achieve the overall goals. The UK had 1150 Priority Species and 65 Priority Habitats, with marine habitats numbering 25.

The UK Post-2010 Biodiversity Framework has now succeeded the UK BAP, which no longer operates. Much of the work previously carried out under the UK BAP is now focused at a country level with the new framework highlighting international priorities to support the CBS’s Strategic Plan for Biodiversity 2011-2020 and the new EU Biodiversity Strategy (EUBS). The UK BAP list of Priority Species and Priority Habitats remain relevant and valuable reference sources (JNCC, 2012).

All three species of Zostera are listed together as a Priority Habitat and have a dedicated Habitat Action Plan (HAP), the overall objectives of which are to:

 Maintain extent and distribution of seagrass beds in UK waters.  Assess feasibility of restoration of damaged or degraded seagrass beds. Until surveys assess the extent of the seagrass resource, it will not be possible to assess whether restoration is necessary, or to specify a final target.

As well as the UK HAP, Zostera features in regional, county and local level BAPs relevant to the Solent area. The plans relevant to Zostera, and their actions, are listed in Table 5.

Table 5. Biodiversity Action Plans relating to Zostera in the Solent area. LEVEL BIODIVERSITY ACTION PLAN OBJECTIVES AND TARGETS REFERNCE Regional Regional Action for Seagrass beds · Determine current extent of seagrass in the region. South East England Biodiversity in South · Maintain current extent. Biodiversity Forum East England · Assess feasibility of restoration of damaged or degraded seagrass beds by 2010. (2000) County Biodiversity Action Coastal Habitat Action Plan – · Seek to introduce fisheries legislation or port and Harbour regulations to protect Hampshire Plan for Hampshire Mudflats and eelgrass beds · Ensure that development schemes, dredging operations and fishing activities do not Biodiversity affect sediment flats or eelgrass beds (including subtidal beds). Partnership (2003) · Develop a strategy to sustainably manage bait digging, thereby limiting its · Control nutrient loading of water in the eastern harbours, where this may · Review the distribution and quality/health of Zostera marina, Z. marina var. · Identify potential sites for restoration of eelgrass beds and draw up a strategy to · Develop and use standardised procedure for long-term monitoring of eelgrass beds in Hampshire (extent, health, associated communities). · Research the natural and anthropogenic factors which influence the recruitment, establishment, persistence and loss of eelgrasses. · Provide advice on minimising the impacts of developments, bait digging, and other activities on eelgrass beds and sediment flats. · Promote awareness among coastal users of the importance of eelgrass beds and how to avoid damage to these habitats. County Biodiversity Action Solent Coastal Habitat Action · Seek to safeguard all estuarine habitats from development through forward planning Cox (2004) Plan for the Isle of Plan · Take opportunities to work with developers to promote habitat restoration and Wight · Develop and incorporate management requirements for priority estuarine habitats and/or species and incorporate them when developing, revising and/or updating · Develop sustainable dredging strategies for the estuaries including approaches to · Work with Southern Water Plc. and others to reduce the impact of waste water discharges to estuaries in particular the impact of nutrients. · Produce a survey strategy for estuarine habitats to complement actions within this · Set up a working group to assess impact of recreational activities on estuarine County Biodiversity Action Estuaries Habitat Action Plan ·hbitt Protect, maintain d i and where possible improve the quality of estuarine habitats. Sussex Biodiversity Plan for Sussex including sub–habitats of · Create/restore 5 ha of seagrass beds. Partnership (2004) mudflats, seagrass beds and saltmarsh Local Chichester Harbour Seagrass beds · Research completed showing accurate extent of decline, and supposed main reasons Chichester Harbour Biodiversity Action · Recovery plan prepared if appropriate. Conservancy (1999) Plan

8.2.3. A UK Marine Act

The Marine Bill received Royal Assent and became the Marine and Coastal Access Act on 12th November 2009. This new piece of legislation will:

 Introduce Marine Spatial Planning to resolve conflict between a range of activities in our seas by zonation and forward planning, it will incorporate areas of nature conservation interest.  Modernise sea fisheries legislation through the creation of Inshore Fisheries and Conservation Authorities, which will provide a much clearer focus on managing inshore fishing activities to protect important marine habitats and biodiversity.  Set up a Marine Management Organisation that will regulate marine activities and help enforce laws to protect the marine environment.  Introduce a network of Marine Conservation Zones to provide a mechanism to protect nationally important species and habitats.

Marine Conservation Zones (MCZs) are a new form of marine protected area and a key part of the marine protected area network (which will include other protected area sites including SACs). They will replace Marine Nature Reserves and should allow the protection of habitats and species that are considered of national importance more effectively. Management of MCZs is likely to restrict some activities, depending on the activity and the likely impact of the feature for which the site is protected. Some MCZs may be designated as Reference Areas, which are likely to see a greater level of restriction on activities.

Defra and the statutory nature conservation bodies have produced a list of habitats and species that require protection through MCZs. Eelgrass is listed as a Habitat Feature of Conservation Interest and as a result MCZs must be designated to protect a selection of eelgrass beds, between 3-5 examples per region. In addition, at least one example was to be

Marine Conservation Zones were discussed around the coast of England through regional stakeholders groups. These groups used available data to recommend sites for designation and management options. A suite of 127 recommended Marine Conservation Zones (rMCZs), which together should form an ecological coherent network of marine protected area, was subsequently presented to the government in September 2012 for discussion. The first public consultation considered just 31 of these rMCZs, none of which were areas in the Hampshire and Isle of Wight area. The consultation took place between 13th December 2012 and 31st March 2013 and resulted in 27 MCZs being designated. At the time of writing, 37 rMCZ sites have been announced to form the second tranche of potential designations. Six of these sites are within Hampshire and the Isle of Wight, and of these, four include seagrass as a Feature of Conservation Interest (Norris to Ryde rMCZ, Bembridge rMCZ, The Needles rMCZ, and Yarmouth to Cowes rMCZ). The second public consultation is due to take place in January 2015.. No deadline or further commitment is currently in place for consultation and subsequent designation of the remaining rMCZs, but seven of the original 127have already been dropped from the process.

9. Management options for Zostera beds

There are a number of measures that can be employed help protect Zostera beds and to manage activities that may otherwise damage them. Some of these are outlined below.

1 Reference Areas (RAs), are effectively highly protected MCZs where no extraction, deposition or other damaging activities are allowed. They will be managed so that the protected features within it will eventually acquire an unimpacted “reference” condition as close to a natural state as possible. Conditions within MCZs can then be compared to these sites, helping to show how well the protection measures within MCZs are working.

9.1. Boat mooring management

Mooring and anchoring in Zostera beds can cause significant damage from chains and anchors dragging. There are several options available to manage these impacts. Where permanent moorings are used, rather than employ the traditional chain moorings, those that use an elasticated rubber hawser, such as the Seaflex system (www.seaflex.net), may be more suitable. The rubber hawser is designed to stretch as the tide comes in, when the tide is out the rubber contracts and therefore does not drag on the seabed and cause physical damage. Trials of these systems have taken place in Mylor, Cornwall, as part of the Cycleau Project. However, it has been suggested that such systems are not suitable for the shallow areas that Zostera inhabits as dragging can still occur when the tide is out.

Another option is to restrict mooring in Zostera areas by not placing permanent moorings within the beds. This would bring the greatest benefit to Zostera, however, it has economic implications, reducing the amount of space available for moorings and therefore the number of moorings.

To reduce the damage caused by anchors, Zostera beds can be marked by buoys, advising boat users to anchor outside of the area. Buoys could also advise boat users to maintain a slow speed to avoid propeller damage to beds. However, unless local byelaws can be introduced, ‘no anchor’ and ‘go slow’ areas must be voluntary. They are therefore best accompanied by a programme of awareness raising and education to ensure the cooperation of boat users. To help achieve this, codes of conduct could be produced, which may include information about the ecological importance of Zostera and highlight the management measures in place, encouraging boat users to adhere to them. Working with stakeholders to produce codes of conduct would be vital to ensure buy in.

9.2. Waste management for boats

In busy harbours and estuaries waste from high concentrations of boats can accumulate. To reduce the environmental impacts of boating, the British Marine Federation and the Royal

Yachting Association instigated the Green Blue Project. Publications have been produced providing information on managing waste and disposing of it responsibly and the use of antifouling paints. They also advise marina owners on how to reduce their environmental impact.

9.3. Fishing activity management

9.3.1 Voluntary agreements

Various fishing activities can impact on Zostera beds. As with no anchoring areas, it is preferable to manage fishing activity that impacts Zostera beds through voluntary means and so education and awareness is crucial. The Torbay Coast and Countryside Trust, with Devon Sea Fisheries Committee, was able to secure a voluntary agreement with scallop fishermen in the area to avoid scalloping in Zostera beds, where they had been previously operating.

9.3.2 Byelaws

Where voluntary means are not appropriate or have proved unsuccessful, local byelaws can be introduced to mitigate against damage caused by fishing activity. This happened in the Portsmouth Harbour SPA. On the 17th January 2011, in response to a breached voluntary agreement, a Marine Management Organisation (MMO) emergency byelaw was put in place under the Marine and Coastal Access Act 2009 (see Section 8.2.3) to protect the eelgrass beds against destructive activities. This emergency byelaw was replaced by a permanent Southern IFCA byelaw on 17th January 2012. Through the Southern IFCA Seagrass Working Group2, a similar voluntary code of conduct was introduced across the Southern IFCA district (Hampshire, Isle of Wight and Dorset coastline to 6nm) in response to further impacts outside the Portsmouth Harbour byelaw area, in particular in Langstone Harbour. This voluntary code

2 In November 2011 Southern IFCA set up a Seagrass Working Group to aid the development of a management strategy to protect seagrass in the SEMS and the wider district from detrimental impacts of the exploitation of sea fisheries resources, using both volunteer and legislative approaches

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 54 of conduct was breached in a number of locations prompting the Southern IFCA to consider a new legislative approach.

However, in August 2012, Defra announced a new approach to manage fishing activities with all EMSs to bring fisheries in line with other activities. The change in approach will promote sustainable fisheries while conserving the marine environment and resources, securing a sustainable future for both. The new approach is being introduced to current fishing activities on a risk-prioritised basis. Under this new approach some fishing practices, including towed demsersal gear (nets, trawls and dredgers), and intertidal hand work (hand gathering and bait digging3) are considered to be highly damaging (red risk) to seagrass habitats and will be restricted. Some other fishing practices, including static gear and non-demersal seine netting are considered to be of medium risk (orange risk) to seagrass habitats. For these, appropriate assessment to determine the level of impact will be carried out to decide appropriate management measures on a site by site basis (MMO, 2013).

At the time of writing, the assessment of all highly damaging (red risk) fishing activities has been completed and byelaws brought in to prevent their use in vulnerable areas. Byelaws relevant to the protection of seagrass habitat within the Solent EMS are:

 Chichester Harbour European Marine Site (Specified Areas) Prohibition of Fishing Method Byelaw (Sussex IFCA, in force 26th November 2013).

 Bottom Towed Fishing Gear Byelaw (Southern IFCA, in force from 27th January 2014)

 Prohibition of Gathering of Sea Fisheries Resources in Seagrass Beds Byelaw (Southern IFCA, in force from 27th January 2014)

3 The severe damage that can be caused by bait digging within Zostera beds had been recognized prior to the new approach in fishing activities management being brought in through publication of a bait diggers Code of Conduct for recreational fishing advising bait diggers not to dig within Zostera beds.

9.3.3. Artificial reefs

Another management option to prevent trawl damage to Zostera beds is the use of artificial reefs, which essentially means placing physical obstructions to trawling, such as concrete blocks, around and in the beds. In the Mediterranean Sea, artificial reefs have been placed is seagrass beds to prevent trawls from operating within them, where they have proved to be effective in preventing damage (Sanchez-Jerez et al., 2002).

9.4. Restoration of Zostera beds

Restoration is another management option for Zostera beds, potentially offering the chance to increase Zostera extent in areas where it has been degraded, re-establish it in areas it once existed prior to wasting disease or possibly act as mitigation where development proposals impact on existing beds.

The UK HAP4 had an objective to ‘assess feasibility of restoration of damaged or degraded seagrass beds’. Similarly, the SE regional and County level BAPs included targets for restoration. However, restoration is not straightforward and previous trials have had mixed results.

There are four broad options for restoration:

 Seeding.  Transplanting seagrass shoots with sediment intact (known as plugs or cores).  Transplant shoots with bare roots.  Improving habitat conditions to encourage natural regeneration and colonisation.

4 Although the UK BAP no longer operates, its list of Priority Species and Priority Habitats remain relevant and valuable reference sources and continue to form the basis of much biodiversity work now carried out under the UK Post-2010 Biodiversity Framework (JNCC, 2012). See Section 8.2.2 for further details.

Seeds can be collected by taking reproductive shoots from natural beds. This method has the advantage that seeds can be sown relatively quickly and cheaply over large areas. The disadvantages are that it can take a long time to gather the seeds and currents and bioturbation can transport the seeds outside of favorable germination areas. In 1993 Z. marina seeding was carried out in the Dutch Wadden Sea and it failed partly due to seeds being taken out of suitable conditions by currents (van Katwijk, 2003). These issues can be minimised by the use of bags. Seeds are put in fine mesh bags which are fixed to the seabed, preventing seeds from being removed. This has been trialed by Harwell and Orth (1999), who found germination increased from 15 % when seeds were broadcast, to up to 56 % when they were sown using bags.

Transplanting cores or plugs has been recommended as a transplanting method (Phillips, 1990). Various tools for taking cores have been used including PVC pipes, metal cans and spades. It has the advantage that well developed roots and rhizomes can be transplanted along with the natural sediment nutrient pool. However, it has been described as being prohibitively expensive and it creates holes in the donor bed that can lead to erosion and significant damage (Davis and Short, 1997).

The bare root method involves removing seagrass shoots along with a small length of rhizome from a donor site and planting it at the transplantation site, singly or in groups, with or without an anchor. Davis and Short (1997) trialed a horizontal rhizome method, consisting of anchoring two bare, mature Z. marina shoots with the rhizomes pointing in opposite directions and being pressed horizontally in to the sediment.

There are relatively few examples of transplanting Z. noltii. Transplantation can be achieved relatively easily at low tide, and laboratory experiments suggest germination can occur at a high rate but subsequent survival is poor (Christensen et al., 2004).

Transplantation success is governed by several factors, notably the method chosen and the site chosen. Locations should have supported Zostera in the past and should have water quality of a high enough standard for Zostera to survive. Variations in nutrients, turbidity,

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 57 salinity, temperature, exposure to air, tides, waves and anthropogenic physical disturbance will all influence transplantation success. Depth may also have an influence and subtidal transplantations seem to have been more successful than intertidal, as the effects of the tidal action and exposure can reduce survival in intertidal areas. Davis and Short (1997) found subtidal survival rates of up to 99 % but only 15 % in intertidal sites. However, van Katwijk (2003), found zero survival of seedlings at depths 0.2 m below Mean Low Water Springs, with light not thought to be limiting at this depth.

Transplantation could be a viable management option, however careful thought needs to be paid to the donor bed, to ensure it is not damaged if plants are removed for transplantation, and to the transplantation site, to ensure conditions are suitable for colonisation. Transplantation success is highly variable and the conditions required for Zostera growth are not well understood, making site selection problematic.

In the UK, large-scale transplantation trials have taken place in a number of locations around the south coast of England. All trials had limited early success but in the longer term, the plants either disappeared altogether or the transplanted areas did not expand (Davison and Hughes, 1998). In the Solent, it may be that if conditions were suitable for Zostera growth, it would already be growing there and the fact that it is not present in a particular location may indicate conditions would not be suitable and transplantation may fail.

Instead of transplantation, efforts could be focused on protecting current Zostera beds and improving the potential Zostera habitat to make it more suitable for natural recolonisation. This may mean improving water quality and preventing physical disturbance.

10. Survey and monitoring techniques

Survey and monitoring of Zostera beds is a requirement for many of the conservation initiatives. Key attributes to assess include location, bed extent and shoot density. Ancillary information such as associated species and plant health is also considered useful. There are

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 58 various factors governing which techniques are most suitable for surveying and monitoring Zostera, including the attributes to be measured, environmental conditions, budget and resources and the scale of the survey area.

Remote sensing techniques, using aerial photography or spectrographic sensors and underwater techniques such as acoustic sensors and towed and drop down videos, are useful to cover large areas at a relatively coarse resolution. For detailed survey of localised beds, field observations, either on the shore or using scuba divers in deeper water, can generate the highest resolution data. Standardised approaches are best to make long term data sets comparable.

Surveying and monitoring Zostera is an action in many of the relevant BAPs, SAC and SPA management plans and the Water Framework Directive. Monitoring Zostera over time can also illustrate changes in water quality as they are considered an indicator species, with declines in Zostera sometimes indicating declines in water quality.

There are various factors governing which techniques are most suitable for surveying and monitoring Zostera. Some methods are best suited to coarse scale surveys over wide areas, whereas others are best suited to high resolution surveys in localised areas. Some techniques require specialist equipment and expertise to operate it, others are basic and require little equipment or expertise, making them useful for volunteer based surveys (Krause- Jensen et al., 2004). The first stage in choosing the most suitable method is to determine the objectives of the study, the location and the resources available.

There are several basic considerations when determining the best approach for surveying:

 Zostera species to be surveyed: Shoot counts may not be practical for Z. noltii as may number several thousand per square meter, percentage coverage may be more useful.  Habitat on which Zostera is growing: Soft mud can require a different approach to firm sand as access can be restricted.

 Extent of area to be surveyed: Is the survey to focus in a small area or will it seek to identify presence/absence of Zostera in large estuaries or along lengths of coast.  Depth at which Zostera is growing: Can it be accessed from the shore or is it in deeper water.  Water clarity: Can it be seen from above the water’s surface.  Budget and/or access to specialist equipment: Are boats, scuba equipment and cameras available.  Time of year: Winter will give low estimates of biomass due to die back.  Expertise of surveyors: Will professional surveyors or volunteers be used to carry out the survey.  The information being sought: Is the survey simply looking to confirm presence and absence or is more detailed information required.

In regard to this latter point of considering the information being sought, there are several measurable features of Zostera beds including:

 Bed location and extent.  Biomass.  Bed density (shoot density) or percentage coverage.  Plant condition (leaf length, evidence of disease, photosynthetic activity).  Sexual status and reproductive success.  Associated flora and fauna.  Environmental conditions including water quality, hydrodynamic regimes, climatic changes.

Survey techniques can be split into three broad categories:

1. Aerial remote sensing: a) Aerial photography. b) Satellite imagery. c) Compact Airborne Spectrographic Imager (CASI). Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 60

2. Subtidal remote sensing: a) Acoustic Ground Discrimination Systems (AGDS) e.g. RoxAnn, Side– Scan Sonar, Echosounders, Biosonics DT4000. b) Underwater video e.g. Remotely Operated Vehicles (ROVs), towed video and drop down video. 3. Physical sampling: a) Grabs and cores. b) Intertidal field observation. c) Scuba diver field observation.

There have been a great many reports and manuals written on the methodologies used when employing these techniques. It is beyond the scope of this report to go in to these detailed methodologies, however, Table 6a-d, adapted from Black and Kochanowska (2004) provides a brief overview of the techniques available and their advantages and disadvantages. Further information and more detailed methodologies can be gained from the references given.

As well as options for measuring the physical state of Zostera beds, there are also options for measuring the physiological state, which can indicate plant health and environmental stressors. The most commonly used technique to indicate plant stress and health is to assess photosynthetic activity, which is often reduced when the plant suffers from environmental stress, such as poor water quality. Photosynthetic activity can be measured using the Fv/Fm fluorescence kinetics parameter, which measures the efficiency of the light harvesting aspect of photosynthesis. This has successfully been used to investigate the effects of the antifouling herbicides Irgarol and Diuron on Z. marina. (Scarlett et al., 1999; Chesworth et al., 2004) The measurements can be taken in the field using non-invasive apparatus making it ideal for repeat surveys.

Table 6a. Overview of techniques available for the surveying and monitoring of Zostera beds.

1. AERIAL REMOTE SENSING SURVEY METHOD ADVANTAGES DISADVANTAGES REFERENCES Aerial photography - A vertically mounted camera on a light · Large coverage in short space of time. · Expensive. · Orth and Moore, 1983 aircraft takes high resolution, large format, digital natural colour · Complete coverage of Zostera bed so can · Requires ground–truthing as image · Mumby et al ., 1997 transparencies, in transects across the site. Using infra-red, the indicate extent. interpretation difficult when distinguishing methodology is the same, but this format allows better between Zostera and algae eg. Ulva spp. differentiation between intertidal algae and Zostera . · High spatial resolution. · Sparse Zostera not easily detected. · Irving et al ., 1998 · Can be cost effective due to large coverage. · Data requires geo-rectification to correct for · Jackson, 2003 aircraft roll, camera aspect, refraction. · Infra–red options allow for better · Poor penetration below sea level, especially in · Jackson et al. , 2006 a,b discrimination between Zostera and algae. areas of high turbidity, only really suitable for shallow areas with good water clarity. · Suited for coarse resolution mapping of bed · Limited by weather – not suitable in low cloud. location and extent. · Not suited for detailed mapping of densities, associated flora and fauna, sexual status etc. Satellite imagery · Large areas may be mapped at any one time. · Older satellites less accurate than aerial · Mumby et al ., 1997 photography. · Older imagery e.g. Landsat Thematic Mapper · Different habitats may not be distinguished. (TM) and SPOT less expensive than aerial photography and CASI. · More modern high resolution e.g. IKONOS · More modern methods as expensive as aerial produces 1 m panchromatic and 4 m multi- photography. spectral data. · Direct observations produced with continuous · Limited by weather conditions, light levels and detailed coverage. operating constraints - restricted to shallow or · Suited to coarse scale mapping in tropical · Unpredictable weather and poor water clarity climes. mean less reliable for UK use. Compact Airborne Spectrographic Imager (CASI) - is a digital · Most accurate, particularly for small scale · Very expensive. · Mumby et al ., 1997 airborne sensor mounted on a light aircraft and providing high studies with high spatial and spectral resolution spectral and spatial resolution. It has been used for a number of for comparing absorbance characteristics of mapping applications, principally on tropical reefs and seagrass macrophytes. beds. · Large areas may be mapped at any one time. · Requires ground-truthing as sometimes difficulty in distinguishing between Zostera and algal species. · Provides an estimate of standing crop biomass. · Limited by weather conditions.

· Data is easily geo-referenced. · Suitable only for intertidal or very shallow Zostera beds. · Multispectral image is more appropriate than aerial photo for atmospheric and water column correction modeling. Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 62

Table 6b. Overview of techniques available for the surveying and monitoring of Zostera beds.

2. SUBTIDAL REMOTE SENSING SURVEY METHOD ADVANTAGES DISADVANTAGES REFERENCES Acoustic Ground Discrimination Systems Sidescan sonar · Useful in areas of poor water clarity. · Insensitive to sparse patches · Munro and Nunny, 1998 · Demarcates dense Zostera strands with eroding · May not be able to differentiate between Zostera · Jackson, 2003 margins. and macroalgae. · Large areas covered relatively quickly. · Insensitive to features which define biotopes. · Easily geo-referenced. · Requires extensive ground-truthing. · Can indicate attributes including leaf height and bed · Requires 8-10 m boat which can restrict movement density. in shallow areas. · Rough seas may affect accuracy of data. · In shallow water, swath width is restricted and therefore larger numbers of transects needed to maintain full spatial coverage. RoxAnn · Useful in areas of poor water clarity. · May not be able to differentiate between Zostera · Munro and Nunny, 1998 and macroalgae. · Relatively cost efficient. · Insensitive to features which define biotopes. · Jackson, 2003 · Large areas mapped relatively quickly. · Requires ground-truthing. · Broad scale maps will display habitat lifeforms and · Requires 8-10 m boat which can restrict movement some biotopes. in shallow areas. · Easily geo-referenced. · Rough seas may affect accuracy of data. · In shallow water, swath width is restricted and therefore larger numbers of transects needed to maintain full spatial coverage. Biosonics · Accurate and quantitative measures of seagrass · Narrow beam width 6 degrees compared with other · Jackson, 2003 DT4000 attributes such as canopy height (to an accuracy of 10 systems gives poor spatial coverage and requires mm), cover, depth range and extent obtained all geo- large number of transects. referenced in realtime. · Easily analysed. · Limited to slack tide. · Jackson et al ., 2006 a,b · Differentiates between macroalgae and seagrass. · Initial equipment cost expensive. · Easy to deploy and maneuver. · Requires extensive ground-truthing. Echosounders · Transects general quick and easy to carry out. · Not all echosounders are able to pick up seagrass.

· Requires minimal post processing. · May not be able to differentiate between Zostera and macroalgae. · Relatively inexpensive. · Insensitive to features which define biotopes · Easy to geo-reference. · Requires extensive ground-truthing.

Table 6c. Overview of techniques available for the surveying and monitoring of Zostera beds. 2. SUBTIDAL REMOTE SENSING (cont.) SURVEY METHOD ADVANTAGES DISADVANTAGES REFERENCES Optical systems Remote Operated · No time limits, assuming good power source. · High cost and requires specialist operators. Vehicles (ROVs) · Highly maneuverable in 3D and can remain · May require hard boat to operate which can restrict stationary for detailed inspection. access to shallow areas. · Can survey large areas of seabed. · Difficult to fly in straight transects. · Can provide both overview and high resolution data · Data analysis of video is time consuming. including density and associated species. · Can provide continuous data transects. · Field of view varies and can lead to inaccuracies of density estimates. · Easy deployment. · Can ground-truth acoustic and aerial surveys. · Can record permanent digital films for visual comparisons over time easy dissemination. Towed video · No depth time limits depending on power source. · May require hard boat to operate which can restrict · McDonald et al., 2005 access to shallow areas. · Towed video at a known speed may provide · Requires maintenance of slow towing speed so · Collins, 2008 information on the extent of bed faster than ROV. dependent on tidal conditions and means straight lines not easy. · Easy deployment. · Speed and direction difficult to control so can not maintain position for close inspection. · Can provide both overview and high resolution data · Data analysis of video is time consuming. including density and associated species. · Can ground-truth acoustic and aerial surveys. · Field of view varies and can lead to inaccuracies of density estimates. · Can record permanent digital films for visual · Towed videos often utilise a metal sledge and comparisons over time easy dissemination. stabilising chains which can damage Zostera beds. · Cheaper than ROV. Dropdown video · Low cost – cheaper than ROV. · Image quality can be less than ROV and towed · Flint, 2006 systems depending on equipment used. · Can be very portable, lightweight, easily deployed · Estimating field of view can be difficult. · McDonald et al ., 2006 and simple to use so minimum expertise required. · Many drops can be completed in a day. · Can ground-truth remote sensing surveys. · Can be used from small dinghies allowing shallow access. · Some versions can be used while underway so capable of giving continuous transect data and making them maneuverable in 3D. · Can provide overview and/or detailed data. · Easy to geo-reference. · Can record permanent digital films for visual comparisons over time and easy dissemination. Table 6d. Overview of techniques available for the surveying and monitoring of Zostera beds. Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 64

3. Physical sampling Grabs and cores · Provides physical samples for subsequent analysis. · Destructive sampling, a form of physical damage to which Zostera beds are particularly vulnerable. · The sampling and analysis techniques are well- · Only provides point data rather than continuous established. data. · Can measure a number of Zostera attributes in each sample. · Can provide information on sediment. Intertidal field observation · The most flexible survey / sampling technique for · Time limited due to tides. · McKenzie, 2003 monitoring intertidal Zostera species. · Allows quantitative observation of intertidal · Only suitable for intertidal populations. · McKenzie et al ., 2003 Zostera species attributes such as density, shoot length, associated species and photosynthetic activity. · Good geo-referencing if GPS used. · Full extent can be difficult to ascertain if bed · Short et al ., 2006 extends below low water. · Several intertidal Zostera species attributes can be · Can only cover small areas during each site visit. monitored on one visit. · Allows repeatable fixed point monitoring. · Time consuming if repeat visits required due to tidal window. · Can ground-truth remotely sensed data. · Access can be problematic on very soft sediments.

· Low cost simple equipment required. · Simple methods can be devised to allow relatively unskilled volunteers to be used, reducing costs (volunteer training courses have been established by Hampshire and Isle of Wight Wildlife Trust). Scuba diver observation · The most flexible survey / sampling technique for · Potentially high cost. · Collins, 2008 monitoring Z. marina. · Allows quantitative observation of Z . marina · Time and weather limited. · Lock et al ., 2006 species attributes such as density, shoot length, associated species. · Several Z. marina attributes can be monitored in · Can only cover small areas during each dive. · Cornwall Wildlife Trust, one dive. 2005 · Volunteer divers can be trained to carry out surveys · Can be difficult to accurately geo-reference survey · Irving et al ., 1998 (diver training courses have been established by stations and map bed extent. Hampshire and Isle of Wight Wildlife Trust).

11. Future survey, research and conservation recommendations

During the production of this report gaps in knowledge have become apparent and allowed the identification of recommendations for future work:

 Continue to survey Zostera beds.  Ensure total bed area is a key objective of further surveys to allow the significance of individual bed to be put in to wider context.  Incorporate techniques to better assess the health of Zostera plants.  Investigate the effects of Zostera beds on local fisheries.  Investigate options for managing Zostera on a landscape scale rather than a site based approach.  Increase awareness raising efforts, targeting stakeholders that potentially pose a threat to Zostera populations.

The work carried out during the Solent Seagrass Project and through the researching and writing of this inventory has highlighted the potential and importance of furthering various aspects of the Zostera survey and conservation programme.

11.1. Increased surveying and monitoring

This edition of the Solent Seagrass Project Inventory includes locations for the vast majority of eelgrass habitat in the Hampshire and Isle of Wight area. However, there are still gaps in our current knowledge for which further survey effort is required. Seaward bed extent has not been established for many beds and current data for some areas, such as Bembridge, and Colwell, Totland and Thorness Bays on the Isle of Wight, are coarse. On the Hampshire coast more survey work is required in the Harbours, with Langstone and Chichester Harbours in particular need of further surveying to assess current bed extents, especially in light of the recent voluntary code of conduct introduced to the Southern IFCA district (see Section 9.3.2). Portsmouth Harbour also requires continued assessment to monitor the effect of the recently established emergency byelaw on Zostera beds in the area, including the recovery of beds in

Cams Bay. Finally, there are still some sites where we only have historic and anecdotal evidence of seagrass. This data is no longer included in the inventory maps for clarity but is included in previous versions which are available on request from Hampshire and Isle of Wight Wildlife Trust. Areas where we only have historic and anecdotal evidence of seagrass need to be revisited and surveyed, in particular to establish seaward extents.

Future surveys should focus on giving accurate data on bed extent, in particular seaward bed boundaries. Extent is one of the most useful attributes to assess declines and increases over time and should be considered a priority in future surveys.

Wide and coarse scale mapping to improve our understanding of the total Zostera resource in the Solent would be particularly useful to coastal planners and conservation organisations, as proposed developments that may impact on a Zostera bed can be put in to context in terms of the likely damage to the Zostera population throughout the whole system. As and when new coastal developments are proposed in or adjacent to Zostera beds, detailed surveys should be carried out.

As well as the physical attributes, physiological monitoring would prove useful to determine any deleterious environmental impacts. In areas such as Langstone Harbour, where Zostera appears to be declining, measuring photosynthetic activity could indicate if this was due to environmental conditions such as water quality. Measuring photosynthetic activity in selected sites around the Solent would provide useful information as to the health of the Zostera population. Allied to this, greater use of existing environmental data, such as that gathered routinely by the Environment Agency, could be made to better understand changes in Zostera populations and potential threats and impacts.

As well as increased survey and monitoring of Zostera, further efforts need to be made to better understand the ecological importance of Zostera to the functioning of the wider ecosystem, including its importance to local fisheries. Following the addition of seahorses to the list of species protected under the Wildlife and Countryside Act, it would be useful to make

Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 67 a more concerted effort to survey for them, as strong associations between seahorses and Zostera will have major implications for the management and conservation of Zostera beds.

During the research conducted for this report it has become clear that a large number of methodologies have been used to survey Zostera beds, both at a local scale and national scale. This means that the comparison of data to assess various attributes, such as density, and trends, such as change over time, is more problematic. Devising and implementing a standardised survey and monitoring strategy for the Solent’s Zostera beds would be very helpful for future assessment and subsequent management.

11.2. Management and conservation

Moving away from site based management and conservation to a more landscape scale approach has been advocated in terrestrial environments for some time by conservation organisations. This approach is also being investigated for marine management and conservation due to the naturally dynamic nature of marine ecosystems meaning migration and transport and potential threats and impacts can be widespread. It would be a particularly suitable approach to managing Zostera beds due to their natural population fluctuations and bed heterogeneity, the proximity of beds to each meaning mobile species can move between different beds, and the fact that development pressures and subsequent conservation decisions are increasingly more likely to be a choice between different beds rather than areas within an individual bed.

Landscape scale management of the beds within the Eastern English Chanel needs further investigation. This means that the survey, monitoring and management aspects of the Solent Seagrass Project would need to be expanded out of the Solent to cover the whole regional sea.

To aid with the management of Zostera beds in Devon, a seagrass working group has been set up. It acts as a forum to enable the exchange of information, advice and ideas to support those involved in Zostera survey, monitoring and management. A similar arrangement is in Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 68 place in Hampshire and the Isle of Wight with the Southern IFCA Seagrass Working Group which has contributed to seagrass protection in the district through the development of a Seagrass Management Strategy that employs both volunteer and legislative approaches to seagrass protection (see Section 9.3).

As many of the management options for Zostera are voluntary, continuing to increase awareness of its importance amongst coastal planners and other stakeholder groups such as boaters and bait diggers is vital to improve its conservation. A programme of awareness focusing on the sailing fraternity would help to relieve pressure on seagrass in areas of high boating activity, such as the Solent.

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Appendix 1. Characteristics and morphology of Zostera species. Adapted from Davison and Hughes (1998).

Zostera marina

Named by: Linnaeus, 1758. Synonyms: None Varieties: - Zostera marina var. angustifolia (Hornem). - Zostera marina var. stenophylla (Ascherson and Graebner). The only difference from var. angustifolia is related to leaf vein number and location. Common names: -Common eelgrass, wigeon grass, broad-leaved grass wrack, marlee, sedge, Slitch. Zone: - In the British Isles, it is considered to be fully marine and subtidal. - Occurs in the shallow sublittoral, typically from below the Mean Low Water mark to 5 m. - Elsewhere, in northern Europe and North America, Z. marina is recorded growing intertidally (mid-shore) as well as subtidally but these records may refer to Z. marina var. angustifolia = Z. angustifolia. Habitat: - Primarily muddy-sand or mud habitats. Colour: - Dark green, with leathery texture. Abundance: - This species appears to have been the most seriously affected by wasting Disease. - Prior to these outbreaks, it was probably the most common species in Britain. - Populations do not appear to have returned to their original levels. Sterile shoots: - The leaves are alternately arranged and flattened. - The sheaths at the base are fused into a tube around the stem. Leaf length: - Maximum 1 m, but typically between 20-50 cm. Leaf width: - 4-10 mm wide. Leaf tip: - Narrow, rounded tips, tips may have a sharp point (mucronate). Leaf veins: - Approximately 5-11 parallel veins that may be regularly spaced. Flowering shoots - Branched. Length: - Are generally shorter than the sterile shoots, with a maximum length of 60 cm. Width: - Are narrower than the sterile shoots. Stigma : style ratio: - 2:1 - the stigma is twice as long as the style. Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 85

Flowering period: - Mid to late summer. Seeds: - Ribbed, brown seeds, up to 3.5 mm long, excluding the style. Rhizomes: - High root-rhizome biomass. - In transverse section, clumps of strengthening fibres are present in the outer cortex (Butcher, 1941b). Main method of - Generally perennial, beds expand by vegetative growth. reproduction: - Annual populations of Z. marina have been recorded in northern Europe and North America. However, these may be populations of what is considered to be Z. angustifolia within the British Isles. Seasonal leaf cover: - Can remain green throughout the year. Summer leaves shed in the autumn, are generally replaced by smaller winter leaves. Longevity: - Unknown.

Zostera angustifolia

Named by: (Hornem) Reichenb. Synonyms: Z. hornemanniana (Tutin). Z. marina var. angustifolia (Hornem). Common names: - Narrow-leaved eelgrass. Zone: - It is commonly intertidal, ranging from the mid-shore down to Low Water Springs. - It is considered to be just as susceptible to desiccation as Z. marina but survives intertidally where mudflats or depressions in substrate provide damp conditions. - It may occasionally be found in deeper water, to a maximum depth of 4 m. However, these may be populations of what is considered to be Z. marina. Habitat: - It is common in estuarine conditions. - It often occurs in mixed beds with Z. noltii, where it predominates in waterlogged depressions between the free- draining hummocks dominated by Z. noltii. Colour: - Light, yellow-green. Abundance: - In Britain, it may have replaced Z. marina as the most common Zostera species. Sterile shoots: - The leaves are alternately arranged and flattened. - The sheaths at the base are fused into a tube around the stem. Leaf length: - Between 15-30 cm. Leaf width: - Typically around 2 (1.5-3) mm. Leaf tip: - Are initially rounded but as the plant matures, they become notched (emarginate). Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 86

Leaf veins: - Approximately 3-5 veins. Flowering shoots: - Branched. Length: - Are generally shorter than the sterile shoots, between 10-30 cm. Width: - Are slightly narrower than the sterile shoots, around 1 mm. Stigma : style ratio: - 1:1- the stigma is the same length as the style. Flowering period: - From early to late summer. Seeds: - Ribbed, brown seeds, 2.5-3.0 mm long, excluding the style. Rhizomes: - 1-2 mm thick and have slightly swollen nodes (Wyer et al, 1977); - In transverse section, the fibre bundles occur in the outer layer of the cortex (Butcher, 1941b; Wyer et al, 1977). Main method of - It appears to rely more upon annual seed set than Z. marina. reproduction: Seasonal leaf cover: - Begin loosing leaves from late September and beds may be bare of leaves by mid-winter (Wyer et al, 1977). Longevity: - Unknown, but some populations may be annual.

Zostera noltii

Named by: Hornemann. Synonyms: Z. noltei (Hornem) Z. nana (Roth). Common names: - Dwarf eelgrass. Zone: - It is intertidal, forming a definite belt between Mean High Water and Mean Low Water Neap. - It is the most tolerant of desiccation and is found highest up the shore. - It is rarely found below the low water mark (Stace, 1997). Habitat: - Like Z. angustifolia, it is common in estuarine conditions. - It often occurs with Z. angustifolia, with Z. noltii predominating on free-draining hummocks whilst Z. angustifolia predominates in the water-logged depressions. Colour: - Grass-green. Abundance: - In Britain, it the least common of the three Zostera species. Sterile shoots: - The leaves are alternately arranged and flattened. - The sheath at the base clasps the stem but is not fused into a tube. Leaf length: - Maximum length 22 cm. Leaf width: - 0.5-1.5 mm. Leaf tip: - The leaves of Z. noltii are initially rounded but as the plant matures, they become notched (emarginate). Marsden, A. L. and Chesworth, J. C. 2014. Inventory of eelgrass beds in Hampshire and the Isle of Wight 2014, Section One: Report. Version 6: May 2014. Hampshire and Isle of Wight Wildlife Trust, Hampshire. 87

Leaf veins: - Approximately 3 irregularly spaced veins. Flowering shoots: - Un-branched or with a few branches near the base. Length: - Are generally shorter than the sterile shoots. Width: - Are generally narrower than the sterile shoots. Flowering period: - From mid to late summer. Seeds: - Smooth, white seeds, 1.5-2.0 mm long, excluding the style. - Seed production is high, however, vegetative growth appears to be of equal or greater importance. Rhizomes: - In transverse section, the strengthening fibre bundles occur in the in the inner part of the cortical layer (Butcher, 1941b; Wyer et al, 1977). Main method of - Vegetative growth through root-rhizome growth appears to reproduction: be main method of bed expansion. Seasonal leaf cover: - Retains its leaves well into the winter (Wyer et al, 1977). Longevity: - Unknown.