Maciej Zalewski

Ecohydrology—the use of ecological and hydrological processes for sustainable management of water resources / Ecohydrologie—la prise en compte de processus écologiques et hydrologiques pour la gestion durable des ressources en eau

Abstract The increasing human population and degradation of biological integrity of ecosystems has been expressed, to a great extent, as a decline in water resources, the most critical factor to achieve sustainable development. This is because overexploitation and degradation of the biotic structure alters ecosystem processes to the point at which the ecosystem ability to provide desired resources is seriously diminished. The progress in ecology during recent years has created a background for integration of ecology and hydrology. UNESCO, under the International Hydrological Programme IHP-V, has initiated and provided a framework for such an interdisciplinary effort. During the programme, the conceptual background and principles of the surficial processes of ecohydrology were defined: first, by integration and quantification of biological and hydrological processes at the basin scale; second, by the enhancement of basin ecosystem absorbing capacity against human impact; and third, by using ecosystem properties as a management tool. Those principles are targeted, not only to eliminate threats, but also to amplify the opportunities for sustainable development as far as the control and regulation of nutrients and water cycling at the basin scale become possible. According to Poppers philosophy, the predictive planning of the future cannot be generated by extrapolating from recently used solutions. The integration of environmental sciences should create not only new scientific disciplines, but also a new solution which can face new challenges-sustainable management of the biogeosphere.

The dependence of fish community structure and dynamics on floodplain and riparian ecotone zone in Parana River, Brazil

Flood intensity was a main factor determining access to the riparian/floodplain ecotonal resources of the upper Parana River, Brazil, and in consequence determining yield of the dominant trophic groups, which are fish feeding on flooded grasslands and on riparian fruits and leaves. Prey and predator density both declined in years of low floods, and predators did not recover until the next year of high flood, more slowly than in the case prey fish, most probably due to differences in life cycle length. The life cycle of one of the most important species, Curimba (Prochilodus lineatus — Characidae) depends on access to the floodplain lagoons and return to the reservoir after maturation for intensive growth. The riparian/floodplain habitat complexity and connectivity has great significance for fish community dynamics and fisheries yield, and may serve a reason to create a national park in the last floodplain section of the upper Parana River.

Notes on ecotone attributes and functions

We attempt to identify general properties of ecotones. Earlier attempts to do so encountered difficulties resulting from contradictory conceptions of ecotones. Thus, we begin with and center our discussion on a definition of ecotone. The definition is complex. It includes scaling, structural, and functional aspects. Based on this complex definition, we offer a brief review of what is an ecotone, what attributes it has, and how it influences other habitats of interest. We identify feedback as a possibly important but ignored function of ecotones. This discussion is presented in general terms which apply to a variety of ecological situations. We point out that results of an evaluation of ecotone attributes largely depends on the spatial and temporal scale at which ecotone is conceptualized and data are collected. We suggest that some of ecotone determinants scale naturally in a repeatable fashion among various aquatic systems. Finally, we point to the concentration of dynamic properties of ecotones as applied to land/water interface.

Effects of catchment properties on hydrochemistry, habitat complexity and invertebrate community structure in a lowland river

The main objective of this study was to quantify the relationship between taxonomic and functional parameters of macroinvertebrate assemblages and reach/landscape attributes of agricultural catchment. We aimed to analyse the relation between landscape patchiness and land-water ecotone structure, and their influence on benthic fauna composition, biomass and functional organization. A variety of catchment characteristics: land use patterns, surface geology (e. g. type of soils), elevation, hydrology database were incorporated into a geographical information system (GIS) to evaluate anthropogenic impact on landscape properties. The scenarios of potential transfer of nitrogen load along the gradient of the river valley were elaborated. The assessment of nutrient export focused on identifying the most effective nutrient barriers across spatial scales. The analysis of landscape and reach units demonstrated significant, negative correlations between the rate of nutrient transfer to surface/groundwaters and (i) the length of riparian ecotones, (ii) river width, and (iii) the areas of wetland and forested patches in the catchment. The trophic base (primary producers; CPOM; FPOM) in the stream channel was analysed as a factor modifying the structural and functional organization of macrobenthos. Canopy cover, and the consequent amount of solar input reaching the stream bed, significantly influenced food-related variables: leaf input and algal biomass. The factor that significantly affected food availability, retention and transport of benthic paniculate organic matter (BPOM) and amount of chlorophyll a was stream discharge. Higher discharge contributed to low retention of BPOM. To obtain more information about environmental variability (56 variables) and macroinvertebrate functional organization, the entire data matrix was analysed using Principal Component Analysis. A significant correlation was shown in the case of shredder abundance (i) in the low-order station S1. (ii) high canopy cover complexity, and (iii) retention of benthic organic matter. Filtering collectors were significantly associated with the presence of suspended organic matter. Other faunal assemblages, highly related to stream hydraulics factors, were alternative gathering collectors/scrapers, much retained at fourth-order station S3. Stream discharge, depth and chlorophyll a significantly affected the presence of these organisms. This indicated the crucial role of habitat heterogeneity, which was attributable to local conditions (detrital inputs, hydraulics, morphological characteristics), and significantly influenced the trophic structure of biocommunities. In the regulated section of the river (S2) without overhanging vegetation, the abundance of scrapers was significantly correlated with open canopy. Domestic and agricultural impact, evidenced by high nutrient concentrations, significantly reduced species richness (stations S4/S4a). Macroinvertebrate communities were used to detect environmental stress in the river system. Assessment of water quality with biological indices directly revealed human-induced alterations (e. g. land use, lack of riparian vegetation, channelization).

Effect of hydrological patterns of tributaries on biotic processes in a lowland reservoir - consequences for restoration.

Relationships between river hydrology and chemistry were considered as the key point of ecohydrological approach for a shallow, eutrophic reservoir (2500 ha) restoration. By comparison of data from the two main tributaries of the reservoir it was demonstrated that nutrient concentrations and consequently load supplying the reservoir are significantly positively correlated with hydrological characteristics of the spring spate of the rivers and depends on theirs catchment characteristics. Concentrations of total phosphorus (TP), which is the main factor responsible for reservoir eutrophication, are positively correlated with spring spate dynamics (Pilica River, r=0.619; P=0.05; Luciaza River, r=0.443; P=0.05) but not with discharge. The above findings also indicate that a high nutrient load has been entering the reservoir in relatively small water volume. As biota react with the nutrient load, a statistically significant correlation was found (r=0.769; P<0.05) between hydrological characteristics of the tributaries’ spring spates and biomass of diatoms in the reservoir. The understanding of temporal variability of nutrient supply in relation to the hydrology of tributaries indicates that a fundamental first step of reservoir restoration should be the reduction of the external nutrient load transported into the reservoir by rivers at the raising hydrograph limb. This may be achieved by converting part of the natural river floodplain in the upper part of the reservoir into constructed wetlands. On the basis of the data obtained, maps and area photographs, the necessary area of treatment wetlands has been estimated. For a reduction of 20% of the TP load of an average spring flood, up to 5 km of the Pilica River valley has to be converted into constructed wetlands (area, 150 ha; depth, 1 m). However, for a reduction of 25% of the load, a re-construction of up to 25 km (area, 500 ha; depth, 1.5 m) of the river is necessary.

The potential for biomanipulation using fry communities in a lowland reservoir: concordance between water quality and optimal recruitment

The fry community in a temperate lowland reservoir was monitored for seven years. The variation in reproductive success of the dominant perch and cyprinids was correlated with the variation of the water level. During summer the main food of perch wasDaphnia. In the year with the highest density of perch, a decline in the density of cladocerans and in the percentage ofDaphnia eaten was observed. This resulted in low stomach fullness and poor fry growth. Simultaneously, the amount of phytoplankton increased. An optimal recruitment curve was found for maintaining water quality with optimal recruitment of fish stocks, assuming that a high rate of fry growth is essential for high survival during winter. Regulation of fry densities can be achieved by the manipulation of water levels during the reproductive and early ontogeny period.

Land/Inland water ecotones : intermediate habitats critical for conservation and management

In the 20th century the utilisation of natural resources, the emission of pollutants and the degradation of landscape has increased beyond a critical level. Only during the last two decades has the predictive ability of environmental sciences gained strength and become the basis for modern conservation and environmental management procedures. This is especially true for aquatic ecology, where a series of new concepts and theories arose (e.g. the biomanipulation concept Shapiro et. al. (1975); role of land/water ecotones — Naiman et al. (1988); river continuum concept — Van-note et al. (1980); flood pulse concept — Junk et al. (1989)).

Cannibalism as a regulatory force of pikeperch, Stizostedion lucioperca (L.), population dynamics in the lowland Sulejow reservoir (Central Poland)

Investigations of fish community dynamics in the pelagic and littoral zone of the lowland Sulejow reservoir (Central Poland) have revealed an occurrence of strong inter- and intra-cohort cannibalism in the population of the key predator: pikeperch, Stizostedion lucioperca (L.). In early summer the number of young-of-the-year, YOY, pikeperch in stomach contents of older conspecifics positively correlated with density of juveniles in the pelagic zone. In two years (1994, 1997), when high density of YOY pikeperch (0.6 and 0.8 individual per m3, respectively) was observed, more than seven juvenile pikeperch per stomach of older conspecifics were found. In years of low reproductive success of pikeperch (0.05 YOY per m3), the average number of juvenile pikeperch in stomachs of predatory conspecifics was below 1. The strong density-dependent predation resulted in a sharp decline of YOY pikeperch toward late summer. Cannibalistic pressure was also observed among YOY pikeperch. In the reservoir, juvenile cohorts displayed a bimodal size distribution in early summer. Small (zooplanktivorous) individuals served as a food for bigger (piscivorous) pikeperch. During shortages of alternative food (perch, cyprinids), cannibalism by YOY from the upper modal group may enhance their recruitment, at the cost of small juveniles (low winter survival). As an effect of this cannibalistic self-regulation, long-term stabilisation of pikeperch year-class strength has been observed.

The importance of the riparian ecotone and river hydraulics for sustainable basin-scale restoration scenarios

1. The effect of riparian ecotone functional complexity and stream hydraulics on an upland river ecosystem has been analysed. 2. The amount of nutrients retained by bottom sediment was lowest on a sandy substrate (range: 26–104 mg m−2 P-PO4) and highest in wetland bays (range: 558–5368 mg m−2 P-PO4). A stream bed covered by Berula erecta had about three times higher retentive nutrient capacity ( x = 584 mg m−2 day−1) than did a sandy substrate( x = 205 mg m−2 day−1). 3. The amount of allochthonous organic matter (CPOM) deposited on the stream bed decreased with current velocity. The trophic potential of CPOM, measured as total protein, was significantly correlated with the amount of deposited CPOM (r = 0.863; p<0.00001) and depended on stream order. 4. Both invertebrate and fish biomass in the upland river were significantly correlated with calcium/bicarbonate (benthos: r = 0.858; p<0.006; fish: r = 0.918; p<0.001). 5. Fish biomass, diversity and species richness were highest in pools, lower in riffles and lowest in the run/transition zone. 6. Macroinvertebrate biomass was highest at an intermediate riparian ecotone complexity with an adequate supply of organic matter and incident light. Fish biomass followed the same trend, being lowest in heavily shaded areas and in open channels without riparian vegetation (range: 1–4.5 g m−2), but highest in ecotones of intermediate complexity (range: 1.6–92.8 g m−2). The ‘cascading effect’ of invertebrate density depletion, which was inversely related to fish biomass, was observed seasonally. 7. The above results indicate that riparian ecotone structure and the heterogeneity of the stream channel may regulate biodiversity, productivity and nutrient retention in the fluvial corridor. These quantitative data help to create alternative scenarios for sustainable river basin management.

Ecohydrology for compensation of Global Change

Water in the XXI century has become the primary factor for sustainable development, eradication of poverty and reversal of ecosystem degradation. Increasing water demand for agriculture and urbanisation, combined with pollution, eutrophication and amplification of the stochastic character of climatic processes, increases water limitations for ecosystems and societies. The transdisciplinary science of Ecohydrology, which has been developed in the framework of the International Hydrological Programme of UNESCO, provides a systemic approach, to regulate hydrology-ecosystem-society interplay towards: 1) slowing down the transfer of water from the atmosphere to the sea, still considered as a priority to reduce the severity of floods and droughts impact; 2) reducing input and regulating the allocation of excess nutrients and pollutants to aquatic ecosystems, toward reversing ecosystems degradation and improvement of human well being; and 3) harmonisation of ecosystem potential with societal needs within the framework of IWRM.