Age model and pollen analysis from site GIK16867 in the northern Angola Basin

Sporomorphs and dinoflagellate cysts from site GIK16867 in the northern Angola Basin record the vegetation history of the West African forest during the last 700 ka in relation to changes in salinity and productivity of the eastern Gulf of Guinea. During most cool and cold periods, the Afromontane forest, rather than the open grass-rich dry forest, expanded to lower altitudes partly replacing the lowland rain forest of the borderlands east of the Gulf of Guinea. Except in Stage 3, when oceanic productivity was high during a period of decreased atmospheric circulation, high oceanic productivity is correlated to strong winds. The response of marine productivity in the course of a climatic cycle, however, is earlier than that of wind vigour and makes wind-stress-induced oceanic upwelling in the area less likely. Monsoon variation is well illustrated by the pollen record of increased lowland rain forest that is paired to the dinoflagellate cyst record of decreased salinity forced by increased precipitation and run-off.

Hydrological and meteorological investigations in a lake near Kangerlussuaq, west Greenland

Few hydrological studies have been made in Greenland, other than on glacial hydrology associated with the ice sheet. Understanding permafrost hydrology and hydroclimatic change and variability, however, provides key information for understanding climate change effects and feedbacks in the Arctic landscape. This paper presents a new extensive and detailed hydrological and meteorological open access dataset, with high temporal resolution from a 1.56 km**2 permafrost catchment with a lake underlain by a through talik close to the ice sheet in the Kangerlussuaq region, western Greenland. The paper describes the hydrological site investigations and utilized equipment, as well as the data collection and processing. The investigations were performed between 2010 and 2013. The high spatial resolution, within the investigated area, of the dataset makes it highly suitable for various detailed hydrological and ecological studies on catchment scale.

Pollen from 50 lake surface samples in Brandenburg, Germany, in 2009

Past changes in plant and landscape diversity can be evaluated through pollen analysis, however, pollen based diversity indexes are potentially biased by differential pollen production and deposition. Studies examining the relationship between pollen and landscape diversity are therefore needed. The aim of this study is to evaluate how different pollen based indexes capture aspects of landscape diversity. Pollen counts were obtained from surface samples of 50 small to medium sized lakes in Brandenburg (Northeast Germany) and compiled into two sets, with one containing all pollen counts from terrestrial plants and the second restricted to wind-pollinated taxa. Both sets were adjusted for the pollen production/dispersal bias using the REVEALS model. A high resolution biotope map was used to extract the density of total biotopes and different biotopes per area as parameters describing landscape diversity. In addition tree species diversity was obtained from forest inventory data. The Shannon index and the number of taxa in a sample of 10 pollen grains are highly correlated and provide a useful measure of pollen type diversity which corresponds best to landscape diversity within one km of the lake and the proportion of non-forested area within seven km. Adjustments of the pollen production/dispersal bias only slightly improve the relationships between pollen diversity and landscape diversity for the restricted dataset as well as for the forest inventory data and corresponding pollen types. Using rarefaction analysis, we propose the following convention: pollen type diversity is represented by the number of types in a small sample (low count e.g. 10), pollen type richness is the number of types in a large sample (high count e.g. 500) and pollen sample evenness is characterized by the ratio of the two. Synthesis. Pollen type diversity is a robust index that captures vegetation structure and landscape diversity. It is ideally suited for between site comparisons as it does not require high pollen counts. In concert with pollen type richness and evenness, it helps evaluating the effect of climate change and human land use on vegetation structure on long timescales.

n-alkane carbon isotope ratios in plants and recent lake sediments from Cameroon

Trees and shrubs in tropical Africa use the C3 cycle as a carbon fixation pathway during photosynthesis, while grasses and sedges mostly use the C4 cycle. Leaf-wax lipids from sedimentary archives such as the long-chain n-alkanes (e.g., n-C27 to n-C33) inherit carbon isotope ratios that are representative of the carbon fixation pathway. Therefore, n-alkane d13C values are often used to reconstruct past C3/C4 composition of vegetation, assuming that the relative proportions of C3 and C4 leaf waxes reflect the relative proportions of C3 and C4 plants. We have compared the d13C values of n-alkanes from modern C3 and C4 plants with previously published values from recent lake sediments and provide a framework for estimating the fractional contribution (areal-based) of C3 vegetation cover (fC3) represented by these sedimentary archives. Samples were collected in Cameroon, across a latitudinal transect that accommodates a wide range of climate zones and vegetation types, as reflected in the progressive northward replacement of C3-dominated rain forest by C4-dominated savanna. The C3 plants analysed were characterised by substantially higher abundances of n-C29 alkanes and by substantially lower abundances of n-C33 alkanes than the C4 plants. Furthermore, the sedimentary d13C values of n-C29 and n-C31 alkanes from recent lake sediments in Cameroon (-37.4 per mil to -26.5 per mil) were generally within the range of d13C values for C3 plants, even when from sites where C4 plants dominated the catchment vegetation. In such cases simple linear mixing models fail to accurately reconstruct the relative proportions of C3 and C4 vegetation cover when using the d13C values of sedimentary n-alkanes, overestimating the proportion of C3 vegetation, likely as a consequence of the differences in plant wax production, preservation, transport, and/or deposition between C3 and C4 plants. We therefore tested a set of non-linear binary mixing models using d13C values from both C3 and C4 vegetation as end-members. The non-linear models included a sigmoid function (sine-squared) that describes small variations in the fC3 values as the minimum and maximum d13C values are approached, and a hyperbolic function that takes into account the differences between C3 and C4 plants discussed above. Model fitting and the estimation of uncertainties were completed using the Monte Carlo algorithm and can be improved by future data addition. Models that provided the best fit with the observed d13C values of sedimentary n-alkanes were either hyperbolic functions or a combination of hyperbolic and sine-squared functions. Such non-linear models may be used to convert d13C measurements on sedimentary n-alkanes directly into reconstructions of C3 vegetation cover.

Granulometry, mineralogy and organic matter content of permafrost core 5011-3

The combination of permafrost history and dynamics, lake level changes and the tectonical framework is considered to play a crucial role for sediment delivery to El'gygytgyn Crater Lake, NE Russian Arctic. The purpose of this study is to propose a depositional framework based on analyses of the core strata from the lake margin and historical reconstructions from various studies at the site. A sedimentological program has been conducted using frozen core samples from the 141.5 m long El'gygytgyn 5011-3 permafrost well. The drill site is located in sedimentary permafrost west of the lake that partly fills the El'gygytgyn Crater. The total core sequence is interpreted as strata building up a progradational alluvial fan delta. Four macroscopically distinct sedimentary units are identified. Unit 1 (141.5-117.0 m) is comprised of ice-cemented, matrix-supported sandy gravel and intercalated sandy layers. Sandy layers represent sediments which rained out as particles in the deeper part of the water column under highly energetic conditions. Unit 2 (117.0-24.25 m) is dominated by ice-cemented, matrix-supported sandy gravel with individual gravel layers. Most of the Unit 2 diamicton is understood to result from alluvial wash and subsequent gravitational sliding of coarse-grained (sandy gravel) material on the basin slope. Unit 3 (24.25-8.5 m) has ice-cemented, matrix-supported sandy gravel that is interrupted by sand beds. These sandy beds are associated with flooding events and represent near-shore sandy shoals. Unit 4 (8.5-0.0 m) is ice-cemented, matrix-supported sandy gravel with varying ice content, mostly higher than below. It consists of slope material and creek fill deposits. The uppermost metre is the active layer (i.e. the top layer of soil with seasonal freeze and thaw) into which modern soil organic matter has been incorporated. The nature of the progradational sediment transport taking place from the western and northern crater margins may be related to the complementary occurrence of frequent turbiditic layers in the central lake basin, as is known from the lake sediment record. Slope processes such as gravitational sliding and sheet flooding occur especially during spring melt and promote mass wasting into the basin. Tectonics are inferred to have initiated the fan accumulation in the first place and possibly the off-centre displacement of the crater lake.

Biological Impacts and Uses of Black Bass Competitive Fishing Tournaments on Large Lake Systems

Recreational fisheries in North America are valued between $47.3 billion and $56.8 billion. Fisheries managers must make strategic decisions based on sound science and knowledge of population ecology, to effectively conserve populations. Competitive fishing, in the form of tournaments, has become an important part of recreational fisheries, and is common on large waterbodies including the Great Lakes. Black Bass, Micropterus spp., are top predators and among the most sought after species in competitive catch-and-release tournaments. This study investigated catch-and-release tournaments as an assessment tool through mark-recapture for Largemouth Bass (>305mm) populations in the Tri Lakes, and Bay of Quinte, part of the eastern basin of Lake Ontario. The population in the Tri Lakes (1999-2002) was estimated to be stable between 21,928-29,780, and the population in the Bay of Quinte (2012-2015) was estimated to be between 31,825-54,029 fish. Survival in the Tri Lakes varied throughout the study period, from 31%-54%; while survival in the Bay of Quinte remained stable at 63%. Differences in survival may be due to differences in fishing pressure, as 34-46% of the Largemouth Bass population on the Tri Lakes is harvested annually and only 19% of catch was attributed to tournament angling. Many biological issues still surround catch-and-release tournaments, particularly concerning displacement from initial capture sites. In the past, the majority of studies have focused on small inland lakes and coastal areas, displacing bass relatively short distances. My study displaced Largemouth and Smallmouth Bass up to 100km, and found very low rates of return; only 1 of 18 Largemouth Bass returned 15 km and 1 of 18 Smallmouth Bass returned 135 km. Both species remained near the release sites for an average of approximately 2 weeks prior to dispersing. Tournament organizers should consider the use of satellite release locations to facilitate dispersal and prevent stockpiling at the release site. Catch-and-release tournaments proved to be a valuable tool in assessing population variables and the effects of long distance displacement through the use of mark recapture and acoustic telemetry on large lake systems.

GIS technologies and spatial organization patterns among hunter-gatherers: an archaeological case study from Southern Patagonia (southern South America)

This paper discusses some aspects of hunter-gatherer spatial organization in southern South Patagonia, in later times to 10,000 cal yr BP. Various methods of spatial analysis, elaborated with a Geographic Information System (GIS) were applied to the distributional pattern of archaeological sites with radiocarbon dates. The shift in the distributional pattern of chronological information was assessed in conjunction with other lines of evidence within a biogeographic framework. Accordingly, the varying degrees of occupation and integration of coastal and interior spaces in human spatial organization are explained in association with the adaptive strategies hunter-gatherers have used over time. Both are part of the same human response to changes in risk and uncertainty variability in the region in terms of resource availability and environmental dynamics.

Lake LaVerne Watershed Project Progress Report: Project Number 1415-007, Final Report, June 30, 2016

This application targets a critical need for low maintenance and inexpensive treatment solutions to encourage landowners and resource managers to enhance the water quality of small ponds and lakes. Many rural and urban small ponds and lakes across Iowa and the region have eutrophic conditions with high levels of nutrients and low levels of oxygen. Story SWCD teamed with Iowa State University (ISU) researchers propose to address this need through the construction and monitoring of a vegetated floating island (VFI) system on ISU's iconic Lake LaVerne. VFI's are hydroponically-vegetated islands that reduce nutrient loading directly from pond and lake water (rather than from soil adjacent to the pond). Urban watershed assessment on the ISU campus has already led to reductions in stormwater runoff to the lake but eutrophic conditions persist and are well documented. The VFI will function as a public art attraction for the entire 2015 growing season during which time monitoring will occur to quantify nitrogen, phosphorus and carbon changes in the lake. Tens of thousands of visitors to the ISU campus and Lake LaVerne will interact with this installation using promotional signage on site, public events and interactive social media throughout the project. Water quality and vegetation analysis will quantify nutrient uptake by the island vegetation and thus determine its effectiveness for use in other similar water bodies in Iowa.

Aspects of migration, size structure and mortality of juvenile Nile perch in the Mwanza Gulf of Lake Victoria

A detailed study of the early life of fishes forms one of the very important aspects with respect to recruitment mechanism and proper uneterstanding of the dynamics leading to sustainance of fish populations. It should be the central theme of the fisheries biologist and managers to extract the bilogical information relevant to the proper understanding of this part of the population. A number of studies in the Mwanza gulf and Lake Victoria have emphasized the need to monitor the fishery by conducting observations of stock size, migration, catch effort data and growth of big specimen (Acere 1981, Goudsward et al 1984, Asila. Ogari 1988 and Okemwa 1984). The present paper discusses the preliminary information on the size structure, mortality and migration of juvenile Nile perch. The long term objectives of the programme is aimed at describing the size structure, growth, mortality, recruitment pattern and population dynamics of the Nile perch up to 30 cm total length in the, Mwanza Gulf.

Lake Nabugabo: a potential reservoir for mukene (Rastrineobola argentea)

"Mukene"Rastrineobola argentea occurs in lakes Victoria, Kyoga, Nabugabo and the Victoria Nile. On lakes Victoria and Kyoga the commercial fishery is well developed. While some fishing occurs at isolated places on the Victoria Nile, the species is yet to be exploited on lake Nabugabo although the potential exists. Experimental fishing (light fishing and beach seining) was conducted on Lake Nabugabo based at the Lake Nabugabo Holiday and Conference Center. Specimens obtained were analyzed for biological and fisheries parameters. Mukene on Lake Nabugabo still grows to a large adult size compared to the Lake Victoria populations. Size at first maturity at 42mmSL is close to that observed on Lake Victoria. Peak breeding occurred between August and January. Unlike on Lake Victoria, R.argentea in Lake Nabugabo is not infested by the cestode Ligula intestinalis that is common in these fishes. Catch rates of 9.8 kg/lamp/hr by the lampara net on this lake compare favorably with many parts of Lake Victoria and on Lake Kyoga where a commercial fishery exists. The amount of by-catch species in the catches however is high and does not therefore favour the establishment of the fishery on this lake. Human exploitation of mukene on Lake Nabugabo would also affect the Nile perch fishery which depends on the species as a source of food.

Fisheries ecology in the interface zone of Lake Nabugabo

This study was carried out in the interface zone of Lake Nabugabo, which is situated to the west of Lake Victoria. Four study sites were chosen from the south-western to the eastern ends of the euhydrophyte-dominated interface zone, which was about 10 km long, 10 to 50 m wide, 2 m deep and characterized by a thick layer of peat at the bottom. Nymphaea caerulea was the most dominant and widespread euhydrophyte species except in the eastern tip of the lake where it was replaced by Nymphaea lotus. Interspersed among these lilies was Ceratophyllum demersum in certain bays which were thought to be either water inlets or out-flows; Utricularia and Nymphoides indica were associated with monospecific stand of N. caerulea in the south- western end of the zone. The microinvertebrates were dominated by Copepoda (represented mainly by Cyclopoida), and Rotifera, with Cladocera occurring sporadically, while the macroinvertebrates were represented by Mollusca, Acarina, and seven insect orders of which Diptera (represented by Chironomidae) was the most dominant and widespread. Snails were found to have increased in abundance and distribution since the early 1960's. Nymphaea-Ceratophyllum mixed habitats had far more larval fishes and macroinvertebrates than monospecific stands of N. caerulea. Generally, the eastern end of the interface zone had more macroinvertebrates and larval fishes than the south-western end. Food habits of larval fishes were dominated by chironomid larvae; others consumed included detritus, aufwuchs and, periodically, cladocerans.

The effect of hook size on the catch rate and size of the Nile perch Lates niloticus (Linne) fishery in the Napoleon Gulf, Lake Victoria, Uganda

This study was undertaken in Napoleon gulf, Lake Victoria Uganda from July – December 2009. It was conducted in four landing sites; Bukaya (0.41103N, 33.19133E), Bugungu (0.40216N, 33.2028E), Busana (0.39062N, 33.25228E) and Kikondo (0.3995N, 33.21848E) all from Buikwe district (Formerly part of Mukono district). The main aim was to determine the effect of both hook size and bait type on the catch rate (mean weight) and size composition of Nile perch (Lates niloticus) (LINNE) fishery in the Napoleon Gulf, Lake Victoria. The main hook sizes investigated during the experiment were 7, 8, 9, 10, 11 and 12 that were dominantly used in harvesting Nile perch in Napoleon Gulf, Lake Victoria. In this study length, weight and bait type data were collected on site from each boat at that particular fishing spot; since most fishermen in the Napoleon Gulf could sell their fish immediately the catch is caught there and then. The results indicated a total of 873 Nile perch fish samples collected during the study. Statistical tests, descriptive statistics, regression and correlation were all carried out using the Statistical Package for the Social Sciences (SPSS) in addition to Microsoft excel. The bait types in the Gulf ranged from 5-10 cm Total length (TL) haplochromine, 24.5-27 cm TL Mormyrus kannume and 9-24 cm TL Clarias species. The bait types had a significant effect on the catch rate and also on the size composition the fish harvested measured as Total length (ANCOVA F=8.231; P<0.05) despite the fact that bait type had no influence on mean weight of fish captured (ANCOVA F=2.898; P>0.05). Hook sizes used by the fishers had a significant effect on the both the size (TL) composition (ANCOVA F=3.847; P<0.05) and the mean weight (ANCOVA F=4.599; P<0.005) of the Nile perch captured. Investigations indicated hook sizes seven (7) and eight (8) were the ones that harvested the Nile perch above the slot size of 50 cm total length. In general hook sizes indicated to be the main drive in the harvesting of the Nile perch though bait type also contributed toward that. Generally there is need for management to put a law in place on the minimum hook size to be used on the harvesting of the Nile perch and also monitored by the Fisheries Management as a regulatory measure. In addition to that aquaculture should be encouraged to farm the fish for bait at a higher scale in the region in order to avoid depleting the wild stocks already in danger of extinction. Through this kind of venture, both biodiversity conservation and environmental sustainability will be observed in the Lake Victoria basin.

The effect of Lampara net on the catch rates and size of the fishing harvest of Rastrineobola argentae (mukene) in selected parts of Lake Victoria, Uganda

This study was undertaken in Napoleon gulf, and part of the off shore area of Lake Victoria Uganda in the landing site of Lufu in Buvuma district in the month of October 2015 for three days of sampling. It was conducted in four landing sites; Busana, Kikondo from Buikwe district and Lufu landing site from Buvuma district. The main aim was to determine the effect of Lampara net on the catch rate and size of the Rastrineobola argentae (mukene) harvested on Lake Victoria using various mesh sizes. The study focused on the 5mm and 10 mm mesh sizes of the Lampara net. A total of 109 boats were sampled; from the 5 mm mesh sizes indicated catch rates of 78-200 kg/boat/day and yet for 10 mm mesh size was at 248 kg/boat day. Statistical tests were carried out on the these two mesh sizes using One way Anova and indicated in catches was (Anova F=7.476; P<0.05) and for the price values was (Anova F=5.488 ; P<0.05). This is an indication that despite the fact that the mukene fishery is on the increase, a time will come when it also be depleted so a need to use the rightful fishing gear of 10mm mesh size is advisable for the biodiversity conservation.

Investigation into the meteorological aspects of the variations in the level of Lake Victoria

The level of Lake Victoria has, since 1961, reached a height which caused serious flood damage. Already the financial implications are considerable for Kenya, Tanzania and Uganda. If further rises can be anticipated, expenditure on flood control measures to the tune of several million pounds sterling must be envisaged. If such rises should lead to uncontrolled discharge at the Owen Falls Dam site because of overshooting, downstream districts of Uganda and the Sudan may be seriously flooded. All this merits a thorough study, and any indication of the future behaviour of lake levels, even when associated with a low probability, must be taken into account. In these circumstances the Water Development Department of Kenya approached the East African Meteorological Department in November, 1964, on behalf of all parties concerned with the request to study the meteorological background of the Iake level variation, with a view to forecasting future behaviour.

Fishing effort and fish yield over a 15 year period on Lake Victoria, Uganda: management implications

The National Fisheries Resources Research Institute (NaFIRRI), the Directorate of Fisheries Resources (DiFR), the Local Government fisheries staff and those from the Beach Management Units (BMUs) of the riparian districts to Lake Victoria regularly and jointly conduct Frame and Catch Assessment Surveys. The information obtained is used to guide fisheries management and development. We reveal the trends in the commercial fish catch landings and fishing effort on the Uganda side of Lake Victoria, over a 15 year period (2000-2015) and provide the underlying factors to the observed changes. The contribution of the high value large size species (Nile perch and Tilapia) to the commercial catch of Lake Victoria has significantly reduced while that of the low value small size species, Mukene has increased over a ten year (2005-2015)period. The information is intended to update and sensitize the key stakeholders on the status of the Lake Victoria fisheries. In addition, the information provided is expected to guide policy formulation and management planning by the fisheries managers at all levels including the BMUs and Landing Site Management Committees (LSMCs), the Local government fisheries staff and the Directorate of Fisheries Resources. The information is anticipated to create awareness among the lakeside fisher communities to reverse the current trend in fish declines.