Factors affecting water plant recovery - A. Overview and sediment influences author: J. Schutten' co-authors: A.J. Davy-,F.J.Madqwick-, H. COOpS3, W. Admiraal', E.H.R.R.Lammens3, G.L. Phillips> Project No LIFE92-3/UKl031 RIZA project EHS*WATERPLANT ISBN 0948119403 'University of Amsterdam, ARISE, Department of Aquatic Ecotoxicolgy, Kruislaan 320, 1098 SM, Amsterdam, The Netherlands 2University of East Anglia, School of Biological Sciences, NR4 7TJ, Norwich, UK 3RIZA (Institute for Inland Water Management and Waste Water Treatment), P.D. Box 17, 8200 AA, Lelystad, The Netherlands 4The Broads Authority, Thomas Harvey House, 18 Colegate, NR3 1BQ, Norwich, UK 5Environment Agency (former National Rivers Authority), Cobham Road, IP3 9JE, Ipswich, UK This report should be cited as: Schutten, J. Davy, A. J., Madgwick, F.J., Coops, H., Admiraal, W., Lammens, E.H.R.R., and Phillips, G.L. (1997) Factors affecting water plant recovery - overview and sediment influences. In Madgwick, F.J. & Phillips, G. L. (eds) 'Restoration of the Norfolk Broads - Final Report', (BARS14) Broads Authority and (P-89) Environment Agency, Norwich UK. Commissioning Organisations: Broads Authority, Thomas Harvey House, 18 Colegate, Norwich, Norfolk, NR3 1BQ, UK Tel: +44 (0) 1603610734 Fax: +44 (0) 1603765710 Environment Agency, Kingfisher House, Goldhay Way, Orton Goldhay, Peterborough, PE2 5ZR, UK Tel: +44 (0) 1733371811 Fax: +44 (0) 1733231840 ©European Commission, Broads Authority, RIZA and Environment Agency 1997. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise without the prior permission of European Commission, The Broads Authority, RIZA and the Environment Agency. Statement of Use: This project was commissioned to develop novel techniques to assist in the restoration of shallow lakes. This report provides results of the 'Water plant recovery' research project from 1993 until 1995. The 'Water plant recovery' project aims at finding causes for delayed recovery of aquatic plants in shallow biomanipulated lakes, and designing management answers. Research Partners: This document was produced by The Broads Authority, RIZA WSE, Environment Agency Broads Research Team, University of Amsterdam ARISE (Department of Aquatic Ecotoxicology), University of East Anglia School for Biological Sciences (Population Biology Sector). Funding Organisations: European Commission, Broads Authority, RIZA, National Rivers Authority (now Environment Agency). Project Leaders: The Broads Authority's Project Leader: Jane Madgwick RIZA's project Leader: Dr. Hugo Coops The Environment Agency's Project Leader: Dr. Geoff Phillips - Anglian Region Figure 1: Map of the Broads area, showing the position of the Broads monitored in 1993. ~ North o I mile I I o I kilometre f------ NORFOLK The Broads Great Yarmouth I Alderfen Broad 2 Belaugh Broad 3 Cocks hoot Broad 4 Cromes Broad 5 Hickling 6 Hoveton Great Broad 7 Martham Broad North 8 Ormesby Broad 9 Pound End Broad AI43 10 Upton AI46 SUFFOLK 4 Contents 6 Summary 6 1. Introduction 8 2. Environmental factors influencing submerged macrophyte distribution 8 2.1 Field survey in 1993 8 2.2 Field survey in 1995 17 3. Effects of sediment chemistry and physical properties on submerged macrophyte survival and growth 17 3.1 Experiments with transplanted sediments in a clear-water lake 18 3.2 Effects of sulphide on the survival and growth of 3 species of submerged macrophytes in a microcosm experiment 33 4. Effects of sediment chemistry and physical properties on susceptibility of submerged macrophytes to physical disturbance 33 4.1 Correlative survey in 20 shallow lakes in the Netherlands and the Broads 34 4.2. Effects of natural and artificial sediments on uprooting resistance and root and shoot growth in a microcosm experiment 35 5. Synthesis, management implications and future research requirements 43 6. References FACTORS AFFECTING WATER PLANT RECOVERY - A. Overview and sediment influences This project was jointly financed by the EC-LlFE- Summary fund and RIZA (Netherlands) with the co-operation Nutrient reduction and biomanipulation are of the University of Amsterdam, University of increasingly used as tools to re-create clear water East Anglia and the Environment Agency. in turbid, green, eutrophicated shallow lakes. The next step, stabilising the resulting aquatic community so that fish can be re-introduced, depends heavily on the recovery of the 1. Introduction submerged aquatic vegetation, as shown for Water managers in the Netherlands (Hosper, 1993) example in other reports in this LIFE-series.This and Great Britain (Broads Authority, 1993) aim to project has sought to discover the reasons for restore clear and diverse lakes in currently algal- the varying performance of macrophytes in dominated systems.Water clarification by nutrient different lakes, and to translate the findings into reduction alone takes a long time becauseof management advice. feedback processeswhich stabilise the turbid state (Hosper et al., 1992, Scheffer et el., 1993; Moss, Experience in The Netherlands and the United 1990). In order to speed the recovery process, Kingdom (Norfolk Broads) has indicated that dredging and manipulation of the fish population lakes with a firm and mineral sediment usually have been used (Broads Authority, 1993; Hosper & have a successful recolonisation of aquatic Meijer, 1993). Macrophytes themselves seem to macrophytes, in contrast to the slow and erratic play an important part in the recovery processand recovery in lakes with a soft and organic in the stabilisation of the final clear water stage sediment. An initial survey in 1993 suggested (Blindow et al., 1993; Carpenter & Lodge, 1986; that light, nutrients and propagule availability Scheffer et al., 1993). were not the main limitations. Hence we have focused on the sediment as a limiting factor for Beds of submerged and floating macrophytes macrophyte recolonisation. A combination of provide structure to the water layer and field and glasshouse experiments showed that separate it into different habitats (Den Hartog & the sediment was not inimical to the introduced Van der Velde, 1988; Lillie & Budd, 1992), so propagules, but that high sulphide providing attachment surfaces for sessile concentrations in the sediment seem to impair zooplankton, macro-invertebrates root extension. A 20-lake survey in 1995 showed (Lewandowski, 1983) and periphyton (Carpenter that wind exposure and sediment cohesion were & Lodge, 1986; Den Hartog & Van der Velde, the main factors determining the abundance 1988; Pandit 1989; Rabe & Gibson, 1983). The and diversity of the aquatic community. Fertility macrophyte zone is also a refuge habitat with and alkalinity of both sediment and water were lower predation risk (Lubbers et al., 1990; Rozas of less importance. & Odum, 1988) for different animal groups such as Cladocera (Savino, 1982; Perrow et el., 1997), macro-invertebrates (Beckett et aI., 1992; Heck & The aquatic plant community in lakes with a firm Timothy, 1981), fish fry and young of the year sediment consisted of a combination of firmly fish (Chapman & Mackay, 1984; Grimm, 1991; rooted perennials and annuals whereas in lakes Holland & Huston, 1984). Macrophytes can with a soft sediment in the Broads, the plant indirectly improve the water quality by community consisted of only functional annuals competing for nutrients with limnetic algae that were nearly all easily uprooted. This implies (Blindow et al., 1993; Jorga & Weise, 1979), and that plants in a soft sediment lake are very restricting water-flow so suspended material can vulnerable to physical disturbance such as from settle (Gregg & Rose, 1982; Kemp et al., 1984). wind-induced currents, or bird or fish grazing, The macrophyte roots can improve sediment because of the combination of the reduced root characteristics by preventing erosion and system and the soft sediment. Once dislodged, detoxifying the sediment through oxygen release the whole plant is lost from the aquatic (Blindow et al., 1993).,1naddition macrophytes can community. Plants in lakes with a firm and be a food source for macro-invertebrates, fish cohesive sediment break before being uprooted, (Carpenter & Lodge, 1986) and birds (Carpenter & which leaves a rootstock for the plants to Lodge, 1986; Jupp & Spence, 1977; Kiorboe, 1980; regrow from. In the next stage of this project we Perrow et ai, 1996b; Schutten et al. 1994) plan to investigate how to overcome, in a practical way, the unsupportive nature of some Recent biomanipulation work in European sediments, and how to predict in a given lake shallow lakes shows that the recovery of the probable stability of its recovering vegetation in terms of abundance and species macrophyte community. diversity appears to be rather unpredictable, this is particularly so in the Norfolk Broads. That is why this 'Macrophyte Recovery Project' was 6 developed as a part of the LIFE programme growth or winter-survival. Root length may 'Restoration of the Norfolk Broads' and RIZA's increas with nutrient depletion in the sediment 'EHS-waterplant'. It is a research project that (Mantai & Newton, 1982; McFarland et el., 1992). aims to gain knowledge of the main factors High nutrient availability increases shoot/root controlling macrophyte recovery after or during ratios in Phragmites australis (Boar et el., 1989) large-scale management of shallow eutrophic and arable crops (Salisbury & Ross,1985).