Jacques Haury

Relationships between macrophytic vegetation and physical features of river habitats: the need for a morphological approach

The aim of this paper is to study the relationships between the physical features of rivers and the distribution of macrophyte vegetation. Field work was undertaken at 207 stations along the Scorff River and its tributaries, a salmon river system in southern Brittany (western France). The physical features were considered using a principal component analysis (PCA). Stepwise multiple regression models made it possible to assess their relationships with the botanical data. The first five axes of the physical PCA (used as explicative variables) were initially linked to the most frequently surveyed species, then to their eco-morphological types, and, finally to Arber’s (1920. Water Plants. A Study of Aquatic Angiosperms. Cambridge Univ. Press, Cambridge, 414 pp) morphological classification. It was concluded that plant morphology was closely related to these environmental factors. This could contribute to the development of predictive models for plant distribution and could increase the knowledge of reference vegetation related to bioindication systems.

Ecological assessment of French Atlantic lakes based on phytoplankton, phytobenthos and macrophytes

Biological elements, including phytoplankton, phytobenthos, macrophytes, benthic invertebrates and fish, are employed by the EU Water Framework Directive (WFD) 2000/60/EC as ecological indicators for the assessment of surface waters. The use of primary producers (phytoplankton, phytobenthos and macrophytes) for water quality assessment has a long history, and several methods have been developed worldwide. In this study, we used these three communities to assess the ecological status of five natural lakes located in the Aquitaine region (southwest France). Several biological indices used in lakes from other European countries or in French rivers were employed and compared among the three communities. Each primary producer provided complementary information about the ecological status of the lakes, including the invasiveness of exotic taxa. Regardless of the producer community used, the response to the environment, as reflected by the indices (adequate for each community), was similar: Lakes Cazaux, Lacanau and Hourtin showed the best ecological status and Parentis and Soustons the worst. Phytoplankton diagnosis reflected and integrated unambiguously the water quality of the lakes, as demonstrated by the strong relationships between the phytoplankton index and the trophic status criteria. This community appeared as the best indicator, especially when macrophytes were absent. The methods applied here represent a potential tool for the assessment of the ecological status in the context of WFD, but they need to be refined. We propose modifications for phytobenthos index initially tailored for running waters for adequate use in lentic ecosystems. Indices for the three primary producers should be modified to incorporate exotic species which may provide information on potential biodiversity losses.

Assessing functional typology involving water quality, physical features and macrophytes in a Normandy river

To carry out a functional typology of a Normandy watercourse, three compartments (water quality, physical features and macrophytes) were studied in 74 stations. The data were analysed with multidimensional methods: Principal Component Analysis (P.C.A.), Hierarchical Cluster Analysis (H.C.A.) and Multiple Factor Analysis (M.F.A.). P.C.A. analysis of the 3 compartments ordered significant variables as following: – stream order, water velocity and light, – conductivity, pollution parameters as opposited to mineralisation ones, – upstream/downstream, sciaphilous/heliophilous, rheophilous, ditch species.

Comparison of water, sediment, and plants for the monitoring of antibiotics: A case study on a river dedicated to fish farming

Oxolinic acid, flumequine, oxytetracycline, and florfenicol are antibiotics commonly used in farming. Because an important percentage of these antibiotics given to fish and cattle ends up, directly or indirectly, in the freshwater environment, suitable tools for the monitoring of these antibiotics are needed. A French river was chosen because of the location of four fish farms and a sewage plant on its main course. First, a passive monitoring program involving water, sediment, and autochthonous bryophytes was performed at 25 sampling sites tested once every three months for one year. Second, an active monitoring method was performed using moss bags for a one-month exposure period, both upstream and downstream of each potential source of antibiotics. Sediment and bryophyte samples, but not water samples, were found to be useful for monitoring environmental contamination by oxolinic acid, flumequine, oxytetracycline, and florfenicol. Sediments and bryophytes also appeared to be complementary media for dating the rivers contamination by antibiotics. Data collected by both active and passive monitoring methods confirmed contamination of the river, mainly by flumequine and oxytetracycline, attributable to fish farming but also to terrestrial animal farming and perhaps human pharmaceuticals.

Local distribution of macrophytes and consequences for sampling methods in large rivers

During the years 2003 and 2004, the distribution of macrophytes was studied at eight sites in two large rivers in the southwest of France (the Dordogne and Garonne). Using a pinpoint method, we obtained 7,083 observations and recorded physical parameters such as depth, distance from bank, water velocity, and substrate type. By using logistic regressions, we showed that a combination of these factors significantly influences the distribution of macrophytes. This enabled us to highlight transversal distribution patterns. Helophyte spermatophytes, free-floating taxa, and most of the nonanchored algae were characteristic of the shallow areas located near the banks. The deepest areas were characterized by a reduced number of species with a majority of submerged spermatophytes which are resistant to high velocity, anchored algae, and bryophytes. These results can be used to implement the Macrophyte Biological Index for Rivers (IBMR) for large rivers.

The ability of aquatic macrophytes to assess fish farm pollution in two salmon rivers

The wastewater from freshwater fish farming is responsible for important water quality modifications in receiving ecosystems. These point source pollution cause local problems for the management of the freshwater environment, especially in salmon rivers. The aim of this paper is to study the relationship between plant communities and environmental factors in two rivers basins on which seven fish farms are located and to assess the relative part of water pollution compared to other environmental factors involved in water plant distribution. The disturbance due to fish farming wastewater increased both richness and diversity of aquatic plant communities and modified the distribution of 11 aquatic macrophytes. Nevertheless, the main factors involved in the aquatic plant distribution in the whole data set were not the location upstream or downstream from one point source pollution but the belonging to one river system and the habitat physical features. Relevant prediction of macrophytic communities is a useful tool for bioindication purposes but several groups of variables that manifest themselves at different spatial levels must be considered.

Downstream Effects of a Hydroelectric Reservoir on Aquatic Plant Assemblages

Macrophytes were studied downstream of the Rophémel hydroelectric dam on the River Rance (Côtes d’Armor Department, western France) to assess the effects of hydroelectric functioning on river macrophyte communities. We studied ten representative sections of the hydro-peaking channel on five occasions in 1995 and 1996, on a 15-km stretch of river. Floristic surveys were carried out on sections 50 m in length, and genera of macroalgae, species of bryophyta, hydrophytes, and emergent rhizophytes were identified. For the aquatic bryophytes and spermatophytes section of our study, we compared our results with 19th century floristic surveys, before the dam was built. During the vegetative growth period, the hydro-peaking frequency was low. The plant richness was highest near the dam. The macrophyte communities were highly modified according to the distance to the dam. The frequency and magnitude of hydro-peaking was related to the aquatic macrophyte richness in an Intermediate Disturbance Hypothesis position. However, the results of the eco-historical comparison with 19th century floristic surveys point to the original nature of the flora found at the site. Some floral patterns, seen during both periods and at an interval of 133 years, were indicative of the ubiquity of the aquatic flora and of the plants’ adaptability. This demonstrates the importance of taking river basin history into account in such biological surveys.

Which adaptations of some invasive Ludwigia spp. (Rosidae, Onagraceae) populations occur in contrasting hydrological conditions in Western France?

Biological invasions in wetlands by Water Primroses (Ludwigia grandiflora ssp. hexapetala and L. peploides ssp. montevidensis) are an increasing problem especially in wet meadows. The aim of this paper is to quantify differences between species and the adaptation of these amphibious plants in order to establish the consequences for site managers. The hypotheses were: (i) that these species differ in biomass and morphology, and (ii) that terrestrial habitats determine particular adaptations such as reduced biomass, more roots and a bushy form. Biomasses from five sites were collected, following seasonal changes and biological traits were measured on selected plants. Comparing species in aquatic habitats, L. peploides produced less biomass than L. grandiflora. Comparing habitats for L. grandiflora, the biomass in meadows was almost twice that in dykes, particularly due to old stems, the converse of the hypothesis. Terrestrial forms were characterized by a bushy morphology, with shorter internodes and stems, as well as more secondary ramifications, while in aquatic habitats the plant architecture was simpler. Models were built linking morphology to species, sites and water conditions. Adaptations to terrestrial habitats of a particularly resistant form with a significant potential biomass are practical constraints for farmers and managers.

Relationships between channelization structures, environmental characteristics, and plant communities in four French streams in the Seine–Normandy catchment

Abstract We examined the relationships between channelization, environmental characteristics, and plant communities in 4 streams (Betz, Cléry, Lunain, and Ecole Rivers) southeast of Paris, France, with the goal of assessing stream health. Seventeen 100-m-long reaches, each divided into a pool/riffle sequence, were monitored in 2006. Each reach had 0 to 3 channelization structures (i.e., embanking, resectioning, and other man-made structures). Redundancy analysis and mean-comparison tests done at 2 spatial scales (reach scale and pool/riffle sequence scale) indicated that channelization significantly affected flow velocity, depth, substrate type, and number of pools/riffles (4 of 24 variables considered). Physical characteristics of the streams were significantly more affected by channelization than were chemical characteristics. Moreover, different channelization structures affected the streams differently. Resectioning and embanking reduced flow velocity and the number of riffles and increased the number of pools. However, man-made structures either accelerated (downstream) or reduced flow velocity (upstream). Channelization strongly affected floristic richness on the basis of biological type (vascular plants, bryophytes, macroalgae) and ecomorphological type (hydrophytes, helophytes) at the pool/riffle sequence scale. Channelization led to taxonomic shifts and loss of biodiversity. Vascular plant taxa such as Helosciadium nodiflorum and Berula erecta were replaced by opportunist taxa such as Potamogeton crispus in channelized reaches. Combinations of channelization structures affected the stream plant assemblages less than did individual structures, a result that suggested compensatory effects. Our study supports the idea that channelization must be accompanied by measures that preserve the initial physical conditions of streams and the natural plant community composition.

Effects of fish farm pollution on phytocenoses in an acidic river (the River Scorff, South Brittany, France)

Summary Effects of fish farm pollution were assessed by comparing upstream and downstream vegetation from three fish farms on the Scorff River system (Southern Brittany). Changes in the occurrence of several species including vascular plants and bryophytes (Myriophyllum alterniflorum, Octodice- ras fontanum), as well as overall variations of species abundance (increase in cover for Amblystegium riparium, Callitriche hamulata, C. obtusangula and decrease in cover for Scapania undulata, Chiloscyphus polyanthos, Ranunculus penicillatus) were observed. Principal Component Analysis showed the importance of physical features in governing distribution and cover of macrophytes for such a disturbance. The ecological response of the vegetation was greater in swifter and shallower reaches (or stretches) than in lower and deeper ones. A particular study of seven species led to the analysis of the respective impact of physical features and pollution on the distribution of species.