Aquatic vascular plants in nitrate-rich calcareous lowland streams

223 Pages·2013·11.19 MB·English

Aquatic vascular plants in nitrate-rich
calcareous lowland streams: do they respond to
phosphorus enrichment and control?
Thesis submitted for the degree of
Doctor of Philosophy
at the University of Leicester
by
Benoit Olivier Laurent DEMARS
BTS (Ahun, France) - MST (Corte, Corsica) - DEA (Orsay, Paris XI)
Department of Biology, University of Leicester
February 2002
UMI Number: U601369
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Tout a commence a la petite ferme de Sauvigny en 1975: la-bas, je suis tombe
amoureux de la terre et de la nature.
A Claude et Jacqueline, mes parents.
Aquatic vascular plants in nitrate-rich calcareous lowland streams: do they
respond to phosphorus enrichment and control?
Benoit O.L. D emars
Department of Biology, University of Leicester, Leicester LEI 7RH
The problems of eutrophication in the lowland rivers of Britain have been exacerbated in the
past 13 years by the droughts of 1989-92 and 1995-96. Large growths of filamentous algae
have smothered aquatic vascular plants (major primary producers) in lowland calcareous
streams and phosphorus enrichment has been blamed for a shift in submerged plant species
composition and community structure.
This study investigated the impact of phosphorus removal from two sewage treatment
works (STWs) situated in the River Wensum catchment area, Norfolk, UK. The mesology of
aquatic vascular plants was investigated through a survey at 62 sites spread over four river
basins: Wensum, Nar, Bure, Wissey. The landscape is predominantly rural (crops and pasture)
not rising above 90 metres (OD).
The average background concentrations of phosphorus from diffuse sources were:
soluble reactive phosphorus (SRP) 13 pg/L, total dissolved phosphorus 24 pg/L and total
phosphorus (TP) 53 pg/L. Before phosphorus stripping (1990-1999), the background
contributed about 12% of the TP loads (0.08-0.10 kg/ha/year of TP); and after (2000-2001) it
was about 34% for two reasons, the phosphorus stripping plus effects due to higher rainfall
(0.13-0.18 kg/ha/year of TP).
The level of bioavailable phosphorus from the river-bed sediment was highest at sites
impacted by both the effluents and weirs associated with mills.
Phosphorus removal effectively reduced the TP load contribution of the two STWs
from 42% to 18% of the effluents in the whole catchment. However the predicted levels of
SRP at mean flow (140-273 pg/L) and 95% exceedance discharge (415-1039 pg/L)
dowstream from the STWs, remained very high.
An isozyme technique was developed to identify the eight British species of
Callitriche L. (water-starworts). This allowed the chorology of Callitriche in the rivers of
Norfolk to be determined.
Aquatic vascular plant composition, species Natural Combination of Attributes (NCAs
- life history trade-offs) and community structure did not respond to the gradient of nutrients
(SRP 11-3600 pg/L, nitrate 6.4-12.9 mg/L, ionised ammonia 16-434 pg/L).
Species composition did respond, however, to the biogeographical units and distance
of the site from the source (surrogate for species probability of colonisation) and channel
depth/substrata (species environmental requirements).
Even the most obvious geomorphological factors were only weak predictors of the
NCAs. Moreover, the NCAs were linked, although only marginally, to the spatial structure of
the river network, a surrogate for species probability of dispersal. Therefore the idea of using
the species’ attribute approach as currently applied to aquatic vascular plants seems falsely
optimistic.
The lack of dominance within plant communities suggested that demographic
processes as well as inter-species competition might have occurred at the local scale as
predicted by the patch dynamics concept. However, the different probabilities of colonisation
of the sites as well as the regional species pool may dictate the local processes of plant
community structure and composition in a directional river network.
This study indicates the need for a unification of the niche and demography theories at
multiple spatial and temporal scales. The species’ demographic dynamics, the catchment-
based habitat heterogeneity and the regional species pool should therefore always be taken
into account for conservation and management purposes. Wetlands should be preserved and
restored as much as possible to maintain the regional species pool which will ensure the
persistence of the riverine flora.
Contents
1. Introduction 1
2. Human impacts on the spatial heterogeneity of phosphorus and sediment
characteristics in a lowland calcareous river basin 21
Ecohydrology & Hydrobiology, submitted
3. The impact of treated sewage effluents on the in-stream phosphorus dynamics
of a calcareous lowland river basin 50
The Science of the Total Environment, submitted
4. Phosphorus control: impact assessment problems at the catchment scale of a
calcareous lowland stream 79
In manuscript.
5. Identification of British Callitriche species by means of isozymes 113
Watsonia, submitted
6. Linking aquatic vascular plants with their riverine environment 129
Journal of Ecology, submitted
7. Community structure of aquatic vascular plants in the calcareous lowland
rivers of Norfolk 178
In manuscript.
8. Concluding remarks 207
Acknowledgements
I am indebted to the scientific committee of the MSc Natural Resource Development in
Corsica for taking me when all the others had turned down my candidature. In UK, most of
the scientists took the time to respond to my letters when I was looking for some practical
experiences. Many offered to me the opportunity to work abroad, doing research. This is how
I started to work with David Harper in 1996 and where I met Nigel Holmes for a wonderful
‘macrophyte day’.
After the MSc, the road towards the PhD has been long and tortuous. I particularly thank
Bernard Saugier (Paris XI), Kevin Murphy (Glasgow) and Serge Muller (Metz) for their help.
David Harper gave me the opportunity to start this ambitious PhD project. He has been my
main supervisor, has provided an excellent support throughout the building up of my PhD and
did an outstanding editorial work, not only to make my thesis sound like good English but
also by his pertinent comments and suggestions!
Richard Gomall has introduced me to the world of molecular ecology and supervised my
work on isozymes. It is the shame that I only managed to finish one chapter. We explored the
possibility of studying the phylogeny of some European species of Callitriche, the gene flow
of Callitriche and Potamogeton along the River Wensum. However, there has been no time to
fully investigate these molecular challenges.
Nigel Willby and Richard Lansdown have spent time to share their botanical knowledge and
have provided many ideas that have improved the three manuscripts on plants, although they
may not agree with all the issues.
Three partners have funded this project and the research benefitted from discussions at our
meetings: Jo-Anne Pitt, Geoff Phillips, Julia Stansfield, Carolyn Penney and Mark White
(Environment Agency); Richard Slaughter (Anglian Water); and Chris Newbold, Richard
Leishman and Stewart Clarke (English Nature). They all agreed that the project should be
extended by six months at our first meeting in September 1998 to allow me to sample three
consecutive years.
As a fieldworker, you are supposed to have your driving licence ... I tried three times but
failed to pass my driving test. Gaynor Evans, Joanna Kemp and Steve Ison came to the rescue
and drove me around Norfolk. Gaynor, Joanna and Federica Fiamingo assisted brillantly in
the field and did not complain when doing fieldwork meant sleeping in a tent or staying under
the rain and taking notes while I was snorkelling.
I enjoyed walking, cycling and hitch-hiking along the road of Norfolk to collect my samples.
The landowners have always allowed me to carry out my survey, even during the foot-and-
mouth outbreak with a stringent field protocol. Many helped, the day I was frozen to death on
my bike, the day we were stuck in the entrance of a field with the van, or telling me stories
about the olden days. It was nice to feel welcome in the local pubs.
Finally, Brian Moss and Colin Ferris accepted to be my examiners.
To all, thank you!
ACRONYMS
AAT Aspartate Amino Transferase
AWS Anglian Water Servives pic
ASIN Arcsine transformation
BAP Bio-available Phosphorus
BACI Before and After Control Impact
BOD5 5-day Biochemical Oxygen Demand
BUR River Bure
CATCH Catchment area
Cl Confidence Interval
CL Confidence Limit
DIST Distance of the site from the source of the river
DoE Department of the Environment
EA Environment Agency
EAWEN EA monitoring sites of the Wensum catchment area
ECAP Eutrophication Control Action Plan
EPC() zero Equilibrium Phosphate Concentration
F Filtered
FBA Fructose-biphosphate Aldolase
GOF Goodness of Fit
GPI Glucose-6-Phosphate Isomerase
IDH Isocitrate Dehydrogenase
LEAP Local Environment Agency Plan
LOG Logarithmic transformation
LOIS Land Ocean Interaction Study
LTR University of Leicester Herbarium
MAFF Ministry of Agriculture, Fisheries and Food
MC8 Morpholine Citrate
MDH Malate Dehydrogenase
ME Malic Enzyme
MF long term mean flow (Q50)
MTR Mean Trophic Rank
NAR River Nar
NCA Natural Combination of Attributes
NF Not Filtered
NGR National Grid Reference
nh4 Ionised Ammonia
NRA National Rivers Authority
NSA Nitrate Sensitive Area
OM Organic Matter
OSPAR Oslo and Paris Conventions
PCA Principal Components Analysis
p.e. Population equivalent
PGD Phosphogluconate Dehydrogenase
PGM Phosphoglucomutase
PSS Phosphorus content of the Suspended Solids
PP Particulate Phosphorus
Q Discharge
Q10 high flow (10 % exceedance discharge)
Q95 low flow (95 % exceedance discharge)
R&D Research and Development
RDA Redundancy Analysis
SAC Special Area of Conservation
SA(E) Sensitive Area (Eutrophic)
SD Standard Deviation
SIMCAT stochastic computer modelling developed by WRc
SPA PCA axis derived from the contiguity matrix
SRP Soluble Reactive Phosphorus
ss Suspended Solids
SSD Silty Sediment Deposit
SSSI Sites of Specific Scientific Interest
STW Sewage Treatment Work
SUP Soluble Unreactive Phosphorus
TBE T ris-Borate-EDT A
TCa Total Calcium (sediment)
TDCa Total Dissolved Calcium of the column water
TDP Total Dissolved Phosphorus (filtered water samples)
TFe Total Iron (sediment)
TON Total Oxidised Nitrogen
TP Total Phosphorus
TPSED Total Phosphorus content of the Sediment
TPWAT Total Phosphorus concentration of the column Water
TSP Total Dissolved Phosphorus (unfiltered water samples)
UGS Unvegetated Gravel/Sand
USGS United States Geological Survey
USEPA United States Environmental Protection Agency
UWWTD Urban Waste Water Treatment Directives
VRP Vegetated Riparian Plants
VSP Vegetated Submerged Plants
WEB Wendling Beck
WEN River Wensum
WIS River Wissey
WRc Water Research Council
1 - Introduction
Eutrophication in streams
Eutrophication describes the biological effects of nutrient enrichment (e.g.
nitrogen, phosphorus) on aquatic ecosystems, (Harper 1992). Nutrient enrichment can
affect any type of aquatic ecosystems such as streams (Peterson et al. 1985, 1993;
Harvey et al. 1998) and their floodplains (Tremolieres et al. 1998; Leps 1999), lakes
(Edmondson 1970; Schindler 1974), estuaries (Nedwell & Rafaelli 1999), coastal
waters (Livingston 2000) and the ocean (Tyrrell 1999).
Nutrient enrichment in streams can increase the in-stream algal primary
production and productivity (e.g. Mulholland et al. 2001). However, other factors
interact with nutrients: current velocity (Homer & Welsh 1981; Samir & Benson-Evans
1982); frequency of bed movement and/or high-velocity perturbation (Biggs et al. 1998,
1999); days of accrual after spate flows (Lohman et al. 1991; Biggs 2000); substrata
heterogeneity (Samir & Benson-Evans 1982; Pringle et al. 1988, Pringle 1990);
catchment geology and land use (Biggs 1995); light availability, e.g canopy cover
(Feminella et al. 1989; Hill et al. 2001) and seasonality (Stockner & Shortreed 1978;
Rosemond et al. 2000; Mulholland et al. 2001).
Leaf decomposition rate, fungal biomass and fungal sporulation were also found
to increase with nutrient enrichment (Elwood et al. 1981; Meyer & Johnson 1983;
Suberkropp & Chauvet 1995; Grattan & Suberkropp 2001), although only at low levels
of nutrients (Newbold et al. 1983; Grattan & Suberkropp 2001; Royer & Minshall
2001). Controlled observations were crucial in demonstrating the role of nutrients
because many other factors (e.g. lignin content of the leaves, pH, alkalinity, detritivors)
affect the rate of leaf decomposition (Webster & Benfield 1986; Suberkropp & Klug
1980; Suberkropp & Chauvet 1995; Suberkropp 2001).
The development of benthic algal biomass can be controlled not only by the
nutrients but also by the grazing pressure of the consumers (Elwood et al. 1981; Hart &
Robinson 1990; Mundie et al. 1991; Hill et al. 1992). In a food web based on
allochtonous input of organic matter and enriched with phosphorus, complex
interactions were unravelled and the bottom-up influence of phosphorus has been
detected on the biomass of detritivors (Rosemond et al 2001).
1
Manipulation of nutrient levels and grazer density in flow-through channel and
field experiments showed that neither top-down (herbivore) nor bottom-up effects
(nutrient) had an overriding control, but rather that it was the interaction between these
factors that ultimately determined the periphyton biomass and productivity (Rosemond
et al. 1993). The bottom-up effect on periphyton biomass was also found to depend on
the specific traits of the predators and consumers of the food web (Biggs et al. 2000).
The interaction of these factors leads to shifts in the composition and, in addition, the
structure of the producer community, as a consequence of the range of life history
characteristics (e.g. reproductive vs. growth trade-offs) found within this community
(Stockner & Shortreed 1978; Rosemond et al. 1993; Biggs 1995; Leroy Poff & Ward
1995; Miltner & Rankin 1998; Rosemond et al. 2000). Changes are also observed in
the population dynamics of the consumers (Hart & Robinson 1990).
Study area
The natural landscape of the temperate climate of the County of Norfolk (UK),
since the post-glacial recolonisation of Quercus robur circa 8000 BP in East Anglia
would essentially be a mixed oak forest (West 1970; Godwin 1975; Ferris et al. 1995)
although Mesolithic people might have already interacted with the natural succession of
vegetation using fire (Smith 1970).
Forest clearance happened with the introduction of farming activities in the
Neolithic (circa 4000 BP in northwest Europe). The pollen diagram from Old
Buckenham Mere (Norfolk) illustrates the development of agricultural practices from
Neolithic to Norman times in the lowlands of East Anglia: cereals were cultivated since
the bronze age (circa 1000 BP) and a shift from pastoral to arable farming occurred
with the Anglo-Saxon period (circa 400 AD; Turner 1970).
At present the rural landscape is dominated by arable land, although pasture in
the floodplain and scattered woodlands still remain (Boar et al. 1994). The rich soils of
the area allow highly productive arable farming and an intensive program of land
drainage started in the 1940s to expand cultivation in response to the increased demand
for home-produced food during the Second World War. National (Agriculture Act of
1947) and European incentives have further encouraged arable farming (European
Union Common Agricultural Policy) - Beckett & Bull 1999.
2