This study investigated the relationship between in-channel physical conditions and the diversity and distribution of macroinvertebrate habitats, known as 'functional habitats'. The Welland, Nene, Ouse and Deben catchments, in the English lowlands, were studied during the summer months of 1995 and 1996. The physical conditions, in terms of depth, velocity and Froude number, associated with each of the functional habitats were identified. The relationship between functional habitat diversity and the in-stream physical environment was examined at two levels: the cross-section and the 50 m reach. Habitat diversity in a cross-section was highest in 'riffle-like' as opposed to 'pool-like' conditions. Cross sections with a high coefficient of Froude number variation were also associated with high habitat diversity. No strong seasonal trends were observed, from early to late summer, in either physical variables, functional habitat diversity or habitat abundance (except for a small change in velocity). Habitat diversity in a reach was highest when the river was found to have a 'natural' channel width and was reduced if the river deviated greatly from its 'natural' (predicted) width. Two types of physical channel degradation led to the river being wider that predicted. These were 'over-widening' and 'ponding'. Sites with these conditions contained a characteristic functional habitat frequently; over-widened reaches were dominated by 'silt' and 'emergent macrophytes' while ponded reaches were dominated by 'floating-leaved macrophytes' and 'macroalgae'. Functional habitat diversity was positively related to spatial heterogeneity at the reach scale. It was highest where 65% of the reach was less than 40 cm deep, and lowest when the reach was uniformly shallow or deep.

This study uses Lake Naivasha, Kenya as an example of a shallow tropical freshwater lake. In common with many tropical lakes it experiences fluctuating water-levels which influence its area and productivity, and is currently considered moderately eutrophic. The light regime experienced by phytoplankton in Lake Naivasha dominates other controls as it determines the potential level of primary production. Photoinhibition reduces productivity by 25% at the surface with maximum productivity at a depth of approximately 0.5m. Light attenuation reduces productivity by 50% at 1m depth with zero productivity at 5m depth. Self-shading causes a 17% loss of productivity under conditions of below average productivity, but a 46% loss when productivity is above average. Hydrological factors form a primary control as the mixing regime determines the light regime. Lake Naivasha is generally well mixed, but where temporary stratification occurs there is nutrient resupply due to sediment anoxia. Without mixing, there is a 75% loss of productivity by cell sedimentation. Low sinking rates, tropical conditions and high nutrient availability favour low Surface Area:Volume species such as Aulacoseira which is the dominant genus. Changing conditions such as increased water-column stability could favour cyanobacteria. Bottom-up controls were the most important in Lake Naivasha, reducing potential productivity by 50%. Nitrogen was found to be more limiting than phosphorus with an algal preference for ammonium over nitrate. Minor nutrients were not limiting. The main source of allochthonous nutrients was from river inflow with underflow and circulations around the lake. Top-down control by grazing imposes a 15% reduction in productivity with zooplankton preferring large 'production' cells over small 'standing-stock' cells.

Measuring energy expenditure using respirometery, heart rate and accelerometry can enable hitherto unknown aspects of a species’ energetic ecology to be uncovered. Due to the increased use of these methods, rigour is required to improve the accuracy of the results. As they can only feed in the sea, King penguins (Aptenodytes patagonicus) need to manage their onshore energetic budget well. During fasting periods, which can last up to one month, heavy individuals need to walk several kilometres to reach their zone of attachment, where they incubate and take care of the egg 24 hours a day. They then need to have sufficient energy reserves to return to sea, swim to the polar front and efficiently fish for prey. Consequently, knowing the energy expenditure of king penguins while onshore is key for understanding their future survival. By investigating the onshore energy expenditure of king penguins, this thesis generates new insights not only into their physiological stress response and the biomechanics of pedestrian locomotion, but also into proxy-based methods of measuring energy expenditure. The cardio-respiratory stress response was defined for this species, with some surprising findings, and the energetic cost of the stress response was demonstrated. Implications for the confounding effect of stressed states on energy proxy calibrations were considered and a standard protocol to alleviate this issue in future studies of king penguin energetics is proposed. The biomechanics and energetics of the pedestrian locomotion were investigated to enhance the understanding of the mechanisms developed to optimise king penguin gait in relation to their body mass. Following investigation of differences in walking between heavy and light penguins, no conclusive explanations were established, though future investigations are suggested to enhance this learning. Finally, using the data collected throughout the thesis, the energy expenditure of early and late breeders was investigated, enabling a better understanding of their energy budgets which can be fed into conservation projects for king penguins.

Rutland Water in Leicestershire, UK, has been dosed with ferric sulphate for eutrophication control through phosphorus inactivation, since 1990. Iron concentrations between 1990 and 1994 were generally <0.5mg Fe 1-1 (maximum 17.5mg Fe 1-1 recorded). Examination of the long-term data (collected since 1980) showed that phophorus has declined in the water column since 1990. Iron and phosphorus have accumulated in the sediments around the pumped inlet through which iron was added. Algal biomass (measured by chlorophyll a) has declined since 1990 although cyanobacterial blooms have still occurred. Laboratory studies established that growth of the Chlorophyte Chlorella vulgaris was inhibited at concentrations >50mg Fe 1-1 and cellular aggregation occurred at concentrations >150mg Fe 1-1. When the Cladoceran Daphnia longispina was exposed to concentrations >11mg Fe 1-1 over 48 hours, significant deaths occurred. 30 second exposure to concentrations >0.5mg Fe 1-1 caused a reduction in feeding rate. Exposure to >3mg Fe 1-1 over 21 days resulted in a reduction in population growth rate. Over this time-span the filtering area of daphnid thoracic limbs increased significantly in concentrations of iron >9mg Fe 1-1. A safe limit of 1.69mg Fe 1-1 was determined from toxicity tests, below which field populations would suffer no harmful effects. There was no evidence of any impact of ferric dosing on daphnid numbers in the reservoir. However, the filtering area of the third thoracic limb in daphnids from around the inlet were significantly greater than in daphnids elsewhere in the reservoir, which may have been a consequence of long-term exposure to sub-lethal concentrations of iron. The observed decline in the size of daphnids in the reservoir since 1980, suggests predation by fish has been a significant force in the reservoir. The success and implications of ferric dosing for eutrophication control in Rutland water, and elsewhere are discussed, and future strategies considered.

Some ecological effects of two herbicides, dichlobenil and diquat on pond ecosystems Two ponds 5.0 metres in diameter were treated with herbicide dichlobenil two were treated with the herbicide diquat, two were left untreated as controls. The effects of herbicide treatment was assessed on the macro-phytes, the algae and zooplankton. Dichlobenil killed all rooted macrophytes within the ponds namely Typha latifolia, Agrostis stolonifera, Ranunculus trichophyllus, Potamogeton gramincus and Chara delicatula. Diquat killed T.latifolia, trichophyllus, P.gramineus and Polygonum amphibium. C.delicatula was partially controlled. The death of the macrophytes lowered the diel amplitude of oxygen in both treatments, but deoxygenation did not occur. This was due primarily to the low macrophyte biomass at the time of spraying and the growth on non susceptible algae which restored the oxygen balance. The production (P) of the algae was related to the biomass or standing crop as g OrgC/mean m2 and differences between the two were due to losses through sedimentation, grazing and parasitism. These losses were determined by sedimentation vessels, an assessment of the grazing pressure by zooplankton on the algae and an assessment of parasitism. The grazing pressure by zooplankton on algae was extremely high and the results indicated that the production of the algae was underestimated by as much as 340%. The ability of zooplankton to control algal production relates not only to the suitability of the algae as a food source but also to the degree of predation on the zooplankton by other secondary producers. Predation on one species of zooplankton Simocephalus vetulus increased when its macrophyte habitat was destroyed. The macrophytes were clearly acting as a refuge. This in turn affected the grazing pressure on the algae. The ponds had a variable recovery time according not only to the type of herbicide but to slight differences in the species composition of the macrophytes in the "replicate" ponds prior to treatment. These differences proved to be of great importance.

The ecological stability of Lake Naivasha is unpredictable, as it lies in an endorrheic basin situated in an intensive agricultural region with diversified climatic conditions. The situation is getting worse as increase in agricultural activities and hence human population continues, consequently resulting in an increase in water demand and abstraction. An investigation in phosphorus dynamics, interactions and possible sources was carried out both in the inflowing waters and the lake. During the "El Nino" rains approximately 9 times more TP was transported into the lake from the catchment mainly in particulate form (PP). The river Malewa transported almost 30 times more total phosphorus (TP) than the other two rivers. Most of the TP input arose from the middle course of the river, mainly in PP form bound in suspended solids. Watering of the livestock in the river was found to elevate the concentration of TP, PP and total suspended solids (TSS), although its influence downstream depended on discharge, intensity and frequency of disturbance. The phosphorus lake loading to the lake varied significantly between the two hydrological phases encountered with 1.41 and 0.21 g m-2 yr-1 for the "extremely" wet and "normal" wet years respectively classifying the lake as eutrophic. However the overall quotient between the mean in-lake phosphorus (P) and the inflow phosphorus (Pi) concentration from the river Malewa portrayed an equilibrium state with an overall P/Pi ratio of 0.62. The Naivasha sediments are poorly sorted with inorganic phosphorus dominance. The lake sediment has low phosphorus buffering capacity as portrayed by a low phosphorus sorption index (PSI), indicating a phosphorus source rather than sink.

Seven different ttypes of colonisation substrata samplers were compared with two direct sampling methods for sampling quantatitvely benthic macroinvertebrates of riffles and pools in the River Tean, Staffordshire. Differences were found in the species composition of the catches; in riffles the largest number of species was collected by cylinder sampling. In pools , colonisation substrata samplers were effective in collecting the most taxonomic groups.

Agriculture is important for maintaining human well-being, but intensive agricultural production can have adverse environmental impacts. Freshwater ecosystems are particularly vulnerable to chemical and physical stressors resulting from agricultural land use, but few studies have compared the effects of different types of agricultural practices on the ecology of small water bodies. In agricultural catchments, the two major land uses, arable and pastoral, differ in their management (e.g. ploughing, fertilizer and pesticide inputs) and therefore in their potential effect on freshwater communities. The aim of this study was to investigate the effects of two types of agricultural land use (arable and pastoral) on the community structure and functioning of ponds and streams. Twenty four sites (6 arable ponds, 6 arable streams, 6 pastoral ponds and 6 pastoral streams) were studied in Leicestershire, UK. Arable streams had lower macroinvertebrate abundance and taxonomic richness than pastoral streams and arable ponds had lower diatom species richness, diversity and evenness than pastoral ponds. Leaf litter decomposition was also higher in arable than pastoral ponds. Feeding by macroinvertebrate shredders (e.g. Gammarus pulex) was a significant contributor to leaf breakdown in streams but not in ponds. The feeding rates of G. pulex and Asellus aquaticus were significantly affected by temperature and intraspecific interactions (i.e. density). Increasing density resulted in greater per capita leaf mass loss of A. aquaticus and lower survival rate of G. pulex. At higher temperature, the per capita leaf mass loss and feeding rates for both species were greater whereas the survival rates were lower. Agricultural land use can adversely affect the structure and functioning of aquatic communities. Consequently, it may have a considerable potential impact on ecosystem services provided by freshwater habitats. Understanding the possible effects of agricultural land use on the structure and functioning of freshwater ecosystems is extremely important and should help in identifying the best land use management to maintain sustainable agricultural production and protect freshwater habitats.

Floodplains in the United Kingdom have evolved from natural landscapes to artificially modified ecosystems through managing lateral and vertical floodplain connectivity leading to synergy or trade-offs in ecosystem service delivery. Research methods have been limited in understanding the processes by which ecosystem service values are formed and the data required to support ecosystem service assessment. Developing a methodology while complex and challenging is necessary in order to take the ecosystem approach forward to support decision making for policy makers, planners and stakeholders. The aim of this research was to develop a method to assess the delivery of ecosystem services in response to changes in floodplain connectivity and evaluate the performance. A case study floodplain was selected at Tempsford, downstream of the River Ivel in Bedfordshire, United Kingdom as an example for opportunities to deliver multiple ecosystem services. A sequential integrated modelling system was applied utilising a linked ISIS 1D-2D hydrodynamic model and WaSim, a 1D soil water balance model to simulate changes in floodplain connectivity and generate model data to improve estimates of ecosystem services indicators. A non- monetary multi-criteria analysis methodology was applied to further develop indicators for ecosystem services assessment and to assess the impacts of the model scenarios on ecosystem services delivery. The integration of the WaSim model was unsuccessful as the model performed poorly in the calibration and validation process and was not fit for its intended purpose. It was deduced that potential groundwater seepage in the regional aquifer occurs outside of the field study site, which cannot be modelled in WaSim. To demonstrate the impact of lateral connectivity controls on the water table position, an empirical method was developed using the mean observed water table position to represent a ‘no drainage system’ vertical connectivity scenario. The results showed that in low frequency/high magnitude flood events, increasing the lateral connectivity by lowering embankments provides synergy and benefits to flood alleviation, water supply and freshwater fish habitat and trade-offs and disbenefits to flood damage, agricultural productivity, terrestrial habitat and recreation. In high frequency/low magnitude flood events, decreasing the lateral connectivity by raising embankments still provides the same synergy and trade-offs yet lower benefits and disbenefits. Marginally decreasing the lateral connectivity creates a higher level of benefits and a lower level of disbenefits to promote multi-functional land use in the floodplain. Managing the control of floodplain connectivity needs to be carefully planned to enable multifunctional land use in a floodplain.

No description available.