The effects of the non-native invertebrate predator Bythotrephes longimanus and declining aqueous calcium on crustacean zooplankton communities in Canadian Shield lakes

Over the last several decades, human activities have resulted in environmental changes that have increased the number of stressors that can act on a single environment. In Canadian Shield lakes, two recent stressors, the invasion of Bythotrephes longimanus and calcium decline, have been documented. Widespread acidification of hundreds of North American lakes has resulted in the precipitous decline of lake water calcium concentration. Crustacean zooplankton with high calcium demands are likely to be vulnerable to calcium decline, especially <1.5 mg Ca/L, where survival and reproduction rates are reduced. These taxa are also vulnerable to predation by Bythotrephes that has been implicated in the loss of pelagic biodiversity in soft water lakes. Despite laboratory and field studies aimed at understanding the independent impact of these stressors, it is unclear how their co-occurrence will influence community response. Using a combination of data from a large regional lake survey and field experiments, I examined the individual and joint effects of Bythotrephes and calcium decline on native zooplankton community structure. Results demonstrated that much is known about Bythotrephes and our findings of reduced total zooplankton and species richness, due to the loss of Cladocera, are consistent with field surveys and other experimental studies. While we did not detect strong evidence for an effect of calcium on zooplankton using the lowest calcium concentration among invaded lakes (1.2 mg Ca/L), there is evidence that, as lake water calcium concentrations fall <1 mg Ca/L, per capita growth rates of a broad variety of taxa are expected to decline. At the regional scale, negative effects of Bythotrephes and calcium on abundances of small cladocerans and Daphnia pulicaria, respectively, were in agreement with my experimental observations. We also observed significant interactions between Bythotrephes and calcium for a broad variety of taxa. As Bythotrephes continues to spread and invade lakes that are also declining in aqueous calcium, both stressors are likely to amplify negative effects on Cladocera that appear the most vulnerable. Loss of these important zooplankton in response to both Bythotrephes and calcium decline, is likely to lower zooplankton productivity, with potential effects on phytoplankton and higher trophic levels.

Adaptación del sector turístico al cambio climático en España. La importancia de las acciones a escala local y en empresas turísticas

El 5º Informe del IPCC (Panel Intergubernamental de Cambio Climático, 2014) señala que el turismo será una de las actividades económicas que mayores efectos negativos experimentará en las próximas décadas debido al calentamiento térmico del planeta. En España, el turismo es una fuente principal de ingresos y de creación de puestos de trabajo en su economía. De ahí que sea necesaria la puesta en marcha de medidas de adaptación a la nueva realidad climática que, en nuestro país, va a suponer cambios en el confort climático de los destinos e incremento de extremos atmosféricos. Frente a los planes de adaptación al cambio climático en la actividad turística, elaborados por los gobiernos estatal y regional, que apenas se han desarrollado en España, la escala local muestra interesantes ejemplos de acciones de adaptación al cambio climático, desarrolladas tanto por los municipios (energía, transporte, vivienda, planificación urbanística) como por la propia empresa turística (hoteles, campings, apartamentos). Medidas de ahorro de agua y luz, fomento del transporte público y de las energías limpias, creación de zonas verdes urbanas y adaptación a los extremos atmosféricos destacan como acciones de mitigación del cambio climático en los destinos turísticos principales de nuestro país.

Discovery of relict subglacial lakes and their geometry and mechanism of drainage

Recent proxy measurements reveal that subglacial lakes beneath modern ice sheets periodically store and release large volumes of water, providing an important but poorly understood influence on contemporary ice dynamics and mass balance. This is because direct observations of how lake drainage initiates and proceeds are lacking. Here we present physical evidence of the mechanism and geometry of lake drainage from the discovery of relict subglacial lakes formed during the last glaciation in Canada. These palaeo-subglacial lakes comprised shallow (<10 m) lenses of water perched behind ridges orientated transverse to ice flow. We show that lakes periodically drained through channels incised into bed substrate (canals). Canals sometimes trend into eskers that represent the depositional imprint of the last high-magnitude lake outburst. The subglacial lakes and channels are preserved on top of glacial lineations, indicating long-term re-organization of the subglacial drainage system and coupling to ice flow.

Descriptions of Water Quality Parameters for Lakes in the Ambient Lake Monitoring Program

This fact sheet summarizes the water quality data collected as part of the Iowa Department of Natural Resources ambient lake monitoring program.

Macroinvertebrate Community Composition and Diversity in Ephemeral and Perennial Ponds on Unregulated Floodplain Meadows in the UK

Ponds are common and abundant landscape features in temperate environments, particularly on floodplains where lateral connectivity with riverine systems persists. Despite their widespread occurrence and importance to regional diversity, research on the ecology and hydrology of temperate ephemeral and perennial floodplain ponds lags behind that of other shallow waterbodies. This study examines the aquatic macroinvertebrate diversity of 34 ponds (20 perennial and 14 ephemeral) on two unregulated riverine floodplain meadows in Leicestershire, UK. Perennial ponds supported nearly twice the diversity of ephemeral ponds. Despite frequent inundation of floodwater and connectivity with other floodplain waterbodies, ephemeral ponds supported distinct invertebrate communities when compared to perennial ponds. When the relative importance of physical and chemical, biological and spatial characteristics was examined, physical and chemical characteristics were found to account for more variation in community composition than biological or spatial variables. The results suggest that niche characteristics rather than neutral colonisation processes dominate the structure of invertebrate communities of floodplain ponds. The maintenance of pond networks with varying hydroperiod lengths and environmental characteristics should be encouraged as part of conservation management strategies to provide heterogeneous environmental conditions to support and enhance aquatic biodiversity at a landscape scale.

Sediment Budget for Cane Land on the Lower Herbert River Floodplain, North Queensland, Australia

Land use in the river catchments of tropical North Queensland appears to have increased the export of sediment and nutrients to the coast. Although evidence of harmful effect of sediment on coastal and riverine ecosystems is limited, there is a growing concern about its possible negative impacts. Sugarcane cultivation on the floodplains of the tropical North Queensland river catchments is thought to be an important source of excess sediment in the river drainage systems. Minimum-tillage, trash blanket harvesting has been shown to reduce erosion from sloping sugarcane fields, but in the strongly modified floodplain landscape other elements (e.g. drains, water furrows and headlands) could still be important sediment sources. The main objectives of this thesis are to quantify the amount of sediment coming from low-lying cane land and identify the important sediment sources in the landscape. The results of this thesis enable sugarcane farmers to take targeted measures for further reduction of the export of sediment and nutrients. Sediment budgets provide a useful approach to identify and quantify potential sediment sources. For this study a sediment budget is calculated for a part of the Ripple Creek catchment, which is a sub-catchment of the Lower Herbert River. The input of sediment from all potential sources in cane land and the storage of sediment within the catchment have been quantified and compared with the output of sediment from the catchment. Input from, and storage on headlands, main drains, minor drains and water furrows, was estimated from erosion pin and surface profile measurements. Input from forested upland, input from fields and the output at the outlet of the catchment was estimated with discharge data from gauged streams and flumes. Data for the sediment budget were collected during two ‘wet’-seasons: 1999-2000 and 2000-2001. The results of the sediment budget indicate that this tropical floodplain area is a net source of sediment. Plant cane fields, which do not have a protective trash cover, were the largest net source of sediment during the 1999-2000 season. Sediment input from water furrows was higher, but there was also considerable storage of sediment in this landscape element. Headlands tend to act as sinks. The source or sink function of drains is less clear, but seems to depend on their shape and vegetation cover. An important problem in this study is the high uncertainty in the estimates of the sediment budget components and is, for example, likely to be the cause of the imbalance in the sediment budget. High uncertainties have particularly affected the results from the 20002001 season. The main source of uncertainty is spatial variation in the erosion and deposition processes. Uncertainty has to be taken into consideration when interpreting the budget results. The observation of a floodplain as sediment source contradicts the general understanding that floodplains are areas of sediment storage within river catchments. A second objective of this thesis was therefore to provide an answer to the question: how can floodplains in the tropical North Queensland catchments can be a source of sediment? In geomorphic literature various factors have been pointed out, that could control floodplain erosion processes. However, their importance is not 'uniquely identified'. Among the most apparent factors are the stream power of the floodwater and the resistance of the floodplain surface both through its sedimentary composition and the vegetation cover. If the cultivated floodplains of the North Queensland catchments are considered in the light of these factors, there is a justified reason to expect them to be a sediment source. Cultivation has lowered the resistance of their surface; increased drainage has increased the drainage velocity and flood control structures have altered flooding patterns. For the Ripple Creek floodplain four qualitative scenarios have been developed that describe erosion and deposition under different flow conditions. Two of these scenarios were experienced during the budget study, involving runoff from local hillslopes and heavy rainfall, which caused floodplain erosion. In the longer term larger flood events, involving floodwater from the Herbert River, may lead to different erosion and deposition processes. The present study has shown that the tropical floodplain of the Herbert River catchment can be a source of sediment under particular flow conditions. It has also shown which elements in the sugarcane landscape are the most important sediment sources under these conditions. This understanding will enable sugarcane farmers to further reduce sediment export from cane land and prevent the negative impact this may have on the North Queensland coastal ecosystems.

Stakeholder-led science: engaging resource managers to identify science needs for long-term management of floodplain conservation lands

Floodplains pose challenges to managers of conservation lands because of constantly changing interactions with their rivers. Although scientific knowledge and understanding of the dynamics and drivers of river-floodplain systems can provide guidance to floodplain managers, the scientific process often occurs in isolation from management. Further, communication barriers between scientists and managers can be obstacles to appropriate application of scientific knowledge. With the coproduction of science in mind, our objectives were the following: (1) to document management priorities of floodplain conservation lands, and (2) identify science needs required to better manage the identified management priorities under nonstationary conditions, i.e., climate change, through stakeholder queries and interactions. We conducted an online survey with 80 resource managers of floodplain conservation lands along the Upper and Middle Mississippi River and Lower Missouri River, USA, to evaluate management priority, management intensity, and available scientific information for management objectives and conservation targets. Management objectives with the least information available relative to priority included controlling invasive species, maintaining respectful relationships with neighbors, and managing native, nongame species. Conservation targets with the least information available to manage relative to management priority included pollinators, marsh birds, reptiles, and shore birds. A follow-up workshop and survey focused on clarifying science needs to achieve management objectives under nonstationary conditions. Managers agreed that metrics of inundation, including depth and extent of inundation, and frequency, duration, and timing of inundation would be the most useful metrics for management of floodplain conservation lands with multiple objectives. This assessment provides guidance for developing relevant and accessible science products to inform management of highly dynamic floodplain environments. Although the problems facing managers of these lands are complex, products focused on a small suite of inundation metrics were determined to be the most useful to guide the decision making process.

Socio-economic aspects of the fisheries of Nabugabo lakes and implications for management

Fisheries are very important to Uganda's economy. The sector provides a vital source of food, recreation, trade and socioeconomic well being for the people and community globally. The fisheries of small lakes are important for producing fish for local populations who are not near the large lakes. These satellite lakes support important fisheries and other economic activities like fishing, water for domestic purposes and tourism, besides socio-cultural values. A number-of fish;- species, some of which were found only in Lake Victoria have been depleted through over-exploitation, introduction of exotics especiaily Nile perch and environmental degradation. Some of these fishes have been observed to survive in satellite lakes in the Victoria and Kyoga Lake basins. The Nabugabo satellite lakes (Manywa, Kayugi and Kayanja) contain endemic Cichlid fish species acting as reservoirs and therefore very important for conservation of fish biodiversity. Despite the socio-economic importance and uniqueness of these satellite lakes little research on socio-economic studies has been carried out. The sustainability of the lake is being threatened by increasing human activities. The fish stocks and species diversity are declining and this poses a threat to the livelihood of the people who depend on fish for food and income. Arising from this need a study was carried out to establish the socio-economic aspects of Nabugabo fisheries and implications for management, on which basis resource users would be made aware of the impacts of their activities. It was hoped that this would go further to ensure wise use and management of the resources by the users. The specific objectives were identifying activities around the lake, establishing socioeconomic values attached to the lake, identifying problems of the lake and resource users and examining existing local based management institutions. Results show that the activities taking place around the lakes include fishing, farming, watering of animals, deforestation and charcoal burning, brick making, resort beach development and food and refreshment. The major problem facing the lake was found to be encroachment of Hippo grass (Vossia) on the lake, which is decreasing the size of the lake, and limiting open waters for fishing (this only applied to Lake Nabugabo). Other important problems include use of illegal fishing methods, declining fish stocks and loss of cultural identity. The resource users are most pressed by the low incomes resulting from poor fish catches, theft of gears and lack of market. On examining the resource base for the lakes, it was only Lake Nabugabo that had a Landing Management Committee. The other three lakes did not have leadership institutions in place except the local councils for the respective villages. This was probably due to observed limited fisheries activities. Majority of the respondents agreed that Government and other service providers should work jointly to supplement local beach management committees in the management of the lakes resources. This is a good gesture because with increase in fishing effort and rampant use of illegal fishing methods, there is need to strengthen management institutions present on the lake. This would require Government, local community and other service providers to work together in a participatory way to control environment-degrading activities and stop the use of illegal fishing methods. Burning of vegetation on the lake should be stopped since it enhances growth of this grass. Finally, traditional taboos; which are present on some of the Nabugabo lakes, should be enhanced, as away of preserving them.

Some biological and ecological considerations for research in the management of the fisheries of Lakes Victoria and Kyoga

There is little doubt that the exploitation of the current fisheries of Lakes Victoria and Kyoga requires close monitoring with a view to enforce adherence to prudent management practices. Many indigenous fishes have gradually disappeared from the commercial fishery of both lakes. In the Uganda portion of Lake Victoria for instance Okaronon and Wadanya (in press) have shown that:- 1. The once preponderant haplochromiine taxon ceased to feature in the commercial catches in 1979. 2. The lung-fish (Protopterus aethiopicus) which formerly contributed significantly to the commercial landings had declined to minor species status by the mid 1980s. 3. The catfishes Clarias mossambicus and Bagrus docmac, formerly major fish species, contributed insignificant quantities to the commercial fishery since the early and mid 1980s, respectively. Similar trend have been "reported in the Kenya and Tanzania portions of Lake Victoria (Bwathondi, 1985; Mainga, 1985, Witte and Goudswaard, 1985). On the other hand since their establishment all round the lake in the early to mid 1980s some introduced fishes namely Nile perch (Lates niloticus) and Nile tilapia (Oreochromis niloticus) built up impressive stocks in Lake Victoria (Ssentongo and Welcomme, 1985, Okaronon et al. 1985; Okaronon and Wadanya, in press). Togetther with the native pelagic cyprinid Rastrineobola argentea or Dagaa/Mukene the introduced fishes have contributed unprecidented catches, stimulating vibrant commercial fisheries which have yielded significant social economic benefits to the peoples of the three states riparian to the Lake (Reynolds and Greboval, 1988; Kudhongania et al in press). The impressive landings particularly of the Nile perch and Nile tilapia have also led to rapid industrialisation of fish processing in East Africa mainly for the export market. Fish export has now the potential of a major foreign exchange enterprise in the region.

Fishing gear selectivity for Lates niloticus L., Oreochromis niloticus L. and Rastrineobola argentea P. in Lakes Victoria, Kyoga and Nabugabo

Catch effort data on which fisheries management regulations are sometimes based are not available for most lakes in Uganda. However, failure to regulate fishing gears and methods has been a major cause of collapse of fisheries in the country. Fisheries have been damaged by destructive and non-selective fishing gears and methods such as trawling and beach seining, by use of gill nets of mesh size which crop immature fish and by introduction of mechanised fishing. Selectivity of gears used to crop Lates niloticus L.(Nile perch), Oreochromis niloticus L. (Nile tilapia) and Rastrineobola argentea Pellegrin (Mukene) which are currently the most important commercial species in Uganda were examined in order to recommend the most suitable types, sizes and methods that should be used in exploiting these fisheries. Gill nets of less than 127 mm mainly cropped immature Nile tilapia and Nile perch. To protect these fisheries, the minimum mesh size of gill nets should be set at 127 mm. Seine nets of 5 mm caught high proportions in immature Mukene while those of 10 mm caught mainly mature Mukene. When operated inshore, both sizes caught immature Nile perch and Nile tilapia as by-catch. To protect the Mukene fishery and avoid catching immature bye-catch, a minimum mesh size of the Mukene net should be 10 mm operated as Lampara type net offshore, but since most fishermen have been using 5 mm seine nets for over five years the minimum size should not be allowed to drop below 5 mm pending further thorough investigations. Beach seining and trawling are destructive to fisheries and should be prohibited until data that may justify their use is available.

Some causes of unreliability of fishery statistics on the African great lakes and possible ways of bettering the statistics

This paper is based on a two year's intensive statistical data collection survey on Lake Kyoga, observations made on Lake Victoria over the last decade occasional visits on Lake Albert (Mobutu) and Lake Malawi. World over, scientists have kept doubting the fisheries statistical figures presented by various African countries. Some countries fail to present any figures. This paper, therefore, narrates most of the causes and possible solutions to those problems.

Past and recent trends in the exploitation of the great lakes fisheries of Uganda

Uganda's fish production has shown a substantial increase from a level of 61,500 tonnes in 1961 to a total of 214,302 tonnes in 1988. During this period significant changes also occurred in species composition, fishing factors, and patterns of utilisation. This paper briefly summarises the fisheries of Uganda's great lakes and reviews past and present trends in their exploitation, as reflected in available catch and effort data collected through the Fisheries Department statistical reporting system.

On dangers to rational exploitation and development of the resources of the great lakes of Africa

The major dangers facing the resources of the Great Lakes of Africa include over exploitation, falling species diversity, accumulating pollution, and a probable decline in fishery productivity. These dangers may be viewed as accentuated by: i) Inadequate scientific knowledge on the exploited resources ii) Reluctance to apply even the limited scientific information available, by fishery administrators iii) Constant increase in the demand for fish and other aquatic resources. iv) Lack of commitment to active collaboration and co-operation by riparian states regarding development and management of the shared resources. This paper discusses the above factors in relation to the dangerous trends facing the resources of the Great Lakes of Africa. The discussion is intended to contribute to the promotion of rational and sustainable utilisation of the aquatic resources of these lakes.

The exploitation of small pelagic fishes of the great lakes of Africa with reference to the mukene (Rastrineobola argentea) fishery of the northern waters of Lake Victoria

Small pelagic fish species have ultimately become important on most of the Great Lakes of Africa, especially after the depletion of the larger, initially preferred fish species. In Lake Victoria, the small pelagic cyprinid Rastrineobola argentea is now the only abundant native species supporting a fast growing light fishery. In Pilkington Bay, off Lingira Island the artisanal light fishery is well established and in the last two years this bay has witnessed a sharp increase in the fishing effort. This has been followed by a modification of fishing method and a reduction in the mesh size of nets used. R. argentea now caught from this bay consist of mainly juveniles and this could result into localized recruitment overfishing. Drawing examples from what is happening to the fishery in Pilkington Bay, it is necessary to carry out research on the stocks, gear and suitable fishing crafts before light fishing spreads to most parts of the lake.