scholarly journals Employing multivariate analysis to determine the drivers of productivity on the North Kenya Bank and in Kenyan territorial waters

2021 ◽  
pp. 33-41
Author(s):  
Joseph Kamau ◽  
Oliver Ochola ◽  
Boaz Ohowa ◽  
Charles Mitto ◽  
Charles Magori ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
Marine Ecosystem ◽  
Interdisciplinary Studies ◽  
Coastal Current ◽  
East African ◽  
African Region ◽  
Natural Processes ◽  
The North ◽  
The Difference ◽  
Monsoon Winds

A complex mix of natural processes exist in nearshore and offshore waters which influence coastal and marine ecosystem productivity. An understanding of the biogeochemical processes involved is a key element in interdisciplinary studies of primary production, oceanic flux and storage of carbon dioxide. Water circulation in the East African region is influenced by coastal currents driven by monsoon winds. There are four oceanic currents influencing Kenya’s coastal waters; namely the East African Coastal Current, the Somali Current, the Southern Equatorial Current and the Equatorial Counter Current. The Kenyan fishing industry is slowly embracing offshore fishing grounds, and the North Kenya Bank is emerging as the next fishery frontier. This study aims to provide insight on the processes driving the productivity of Kenya’s territorial waters. The variable Si* (the difference between available silicate [Si(OH)4] and nitrate [NO3-]) was employed as a proxy of upwelling. It was highly positively correlated to chlorophyll-a, indicating that upwelling is a major phenomenon driving productivity in Kenyan territorial waters. Particulate Organic Carbon (POC) and Dissolved Oxygen (DO) exhibited a lesser positive correlation with chlorophyll-a, implying that remineralization also has some influence in the productivity of the area.

scholarly journals Factors influencing spatial patterns in primary productivity in Kenyan territorial waters

2021 ◽  
pp. 9-18
Author(s):  
Joseph Kamau ◽  
Noah Ngisiange ◽  
Oliver Ochola ◽  
James Kilionzi ◽  
Amon Kimeli ◽  
...  
Keyword(s):  
Chlorophyll A ◽  
Coastal Waters ◽  
Pelagic Fish ◽  
Coastal Current ◽  
East African ◽  
The North ◽  
Factors Influencing ◽  
Mangrove System ◽  
Low Levels ◽  
Upwelling Event

This study was formulated to investigate productivity systems within Kenyan territorial waters. The interaction of processes on the margins of the marine waters, particularly the influx of fresh water loaded with sediments and nutrients, influences productivity of coastal waters. These deposited sediments, rich in nutrients, create a topographic barrier to the northerly flowing East African Coastal Current (EACC). Phosphate and nitrate peaks observed around the North Kenya Bank area provide evidence of an upwelling event. The contribution of sediments from the Lamu archipelago mangrove system is evident from the high observed particulate organic carbon (POC) input around the area. The system around the Lamu archipelago did not however show high chlorophyll-a levels despite the high POC influx. This may be due to the low levels of limiting phosphate in the surrounding waters, contrary to the observation further north in the region where high chlorophyll-a levels and corresponding higher phosphate levels were apparent. Productivity was largely supported by upwelling and organic matter mineralization. High levels of chlorophyll corresponded to high pelagic fish densities in the south (around 4.5°S) and north of the study area (around 2.5°S).

Seminar on Social Research in the North-East African Region

1967 ◽  
Vol 5 (2) ◽  
pp. 279-279
Author(s):  
I. M. Lewis
Keyword(s):  
Social Research ◽  
Field Work ◽  
Social Organisation ◽  
East African ◽  
African Region ◽  
Attitudes And Practices ◽  
North East ◽  
The North ◽  
The Social ◽  
University College London

This seminar was held at the Institute of Ethiopian Studies, under the general chairmanship of Dr I. M. Lewis of University College, London. It was organised by Dr Richard Pankhurst and ProfessorJ. Comhaire, with financial assistance from the British Ministry of Overseas Development. The seminar was attended by anthropologists currently engaged in field-work and by members of the Haile Selassie I University's Faculties of Arts, Law, Medicine, Business Administration, and the Institute of Ethiopian Studies, as well as staff of the Ministry of Community Development and Public Health. A number of visiting scholars, including Professor V. L. Grottanelli, participated in the meeting. Reports were received on field-work in Somalia and the Sudan as well as in Ethiopia: and the following papers were given: Dr D. Hecht on ‘Sacred Kingship in Africa’Fekadu Gedamu on ‘The Social Organisation of the Kistane Gurage’; J. Stauder on ‘The Social Organisation of the Mahangir’Dr. M. Lewis on ‘Possession Cults in Northern Somalia’A. Orent on ‘The Doce Cult in Kaffa’Virginia Luling on ‘Spirit-possession Cults in Mogadiscio’Terefe Walde Tsadik on ‘The Muyat Cult in Shoa’R. Hallpike on ‘Status of Craftsmen among the Konso’M. Cittadini on ‘Kunama Marriage’and J. Lisowski on ‘Biometrics of N.E. African Migrations’. Development papers were given by P. Sand on ‘Law as a Factor of Social Change’G. Savard on ‘Social Factors in Development’M. de Young on ‘Markets in Ethiopia’S. Messing on ‘Medical Attitudes and Practices in Ethiopia’and R. Bahar on ‘Rural Housing in Ethiopia’.

scholarly journals North and East African mitochondrial genetic variation needs further characterization towards precision medicine

2021 ◽  
Author(s):  
Anke Fähnrich ◽  
Isabel Stephan ◽  
Misa Hirose ◽  
Mosab Ali Awadelkareem ◽  
Saleh Ibrahim ◽  
...  
Keyword(s):  
Mitochondrial Genomes ◽  
Human Populations ◽  
East African ◽  
African Region ◽  
Cell Organelles ◽  
High Coverage ◽  
The North ◽  
Health And Disease ◽  
East African Region ◽  
Mitochondrial Sequences

Mitochondria are maternally inherited cell organelles with their own genome, and perform various functions in eukaryotic cells such as energy production and cellular homeostasis. Due to their inheritance and manifold biological roles in health and disease, mitochondrial genetics serves a dual purpose of tracing the history as well as disease susceptibility of human populations across the globe. This requires a comprehensive catalogue of commonly observed genetic variations in the mitochondria for all regions throughout the world. So far, however, certain regions, such as North and East Africa have been understudied. Towards this, we have created the most comprehensive quality-controlled North and East African mitochondrial dataset to date by compiling 11 published cohorts with novel data of mitochondrial genomes from 159 Sudanese individuals. We combined these 641 mitochondrial sequences with sequences from the 1000 Genomes (n=2,504) and the Human Genome Diversity Project (n=828) and used the tool haplocheck for extensive quality control and detection of in-sample contamination. Using a subset of high-coverage mitochondrial sequences we predict 15 potentially novel haplogroups in North and East African subjects and observe likely phylogenetic deviations from the established PhyloTree reference for haplogroups L0a1 and L2a1. This demonstrates common hitherto unexplored variants in mitochondrial genomes of the North and East African region that lead to novel phylogenetic relationships, calling for further in-depth population genetic studies in that region.

The Response of the Surface Circulation of the Arabian Sea to Monsoonal Forcing

2013 ◽  
Vol 43 (9) ◽  
pp. 2008-2022 ◽  
Author(s):  
L. M. Beal ◽  
V. Hormann ◽  
R. Lumpkin ◽  
G. R. Foltz
Keyword(s):  
Arabian Sea ◽  
Southwest Monsoon ◽  
Western Boundary ◽  
Coastal Current ◽  
Ekman Pumping ◽  
East African ◽  
Wind Stress Curl ◽  
Surface Circulation ◽  
Monsoon Winds ◽  
Counter Current

Abstract Two decades of drifter and satellite data allow the authors to describe the seasonal evolution of the surface circulation of the Arabian Sea, which reverses annually with the Indian monsoon winds. This study finds several features that advance current understanding. Most significantly, northward flow appears along the length of the western boundary, together with a weak anticyclone at 6°N (a precursor to the Great Whirl) as early as March or April, one or two months before the southwest monsoon winds. This circulation is driven by planetary waves, which are initiated by wind curl forcing during the previous southwest monsoon, leading the authors to speculate that there is an oceanic mechanism through which one monsoon may precondition the next. Second, the authors find that the eastward South Equatorial Counter Current (SECC) is present year-round, fed by the northward East African Coastal Current (EACC). During the southwest monsoon the EACC overshoots the equator and splits, feeding both northward into the Somali Current and eastward into the SECC by looping back across the equator. This retroflection of the EACC is what was previously known as the southern gyre. At the surface, this circulation is obscured by strong, locally wind-driven, cross-equatorial transport. The semiannual variability of the SECC is governed by Ekman pumping over the equatorial gyre. Finally, there is broad, strong eastward flow at the mouth of the Gulf of Aden throughout the southwest monsoon, coincident with alongshore winds and a switch in sign of the wind stress curl along the axis of the atmospheric monsoon jet.

Spatiotemporal evolution of the chlorophyll a trend in the North Atlantic Ocean

2018 ◽  
Vol 612 ◽  
pp. 1141-1148 ◽  
Author(s):  
Min Zhang ◽  
Yuanling Zhang ◽  
Qi Shu ◽  
Chang Zhao ◽  
Gang Wang ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Chlorophyll A ◽  
North Atlantic ◽  
North Atlantic Ocean ◽  
Spatiotemporal Evolution ◽  
The North ◽  
The North Atlantic

scholarly journals Detecting Climate Driven Changes in Chlorophyll-a in Deep Subalpine Lakes Using Long Term Satellite Data

Water ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 866
Author(s):  
Gary Free ◽  
Mariano Bresciani ◽  
Monica Pinardi ◽  
Nicola Ghirardi ◽  
Giulia Luciani ◽  
...  
Keyword(s):  
Climate Change ◽  
Chlorophyll A ◽  
Nutrient Dynamics ◽  
Cascading Effects ◽  
The North ◽  
Subalpine Lakes ◽  
Winter Temperatures ◽  
Decadal Climate ◽  
The North Atlantic Oscillation ◽  
Traditional Pattern

Climate change has increased the temperature and altered the mixing regime of high-value lakes in the subalpine region of Northern Italy. Remote sensing of chlorophyll-a can help provide a time series to allow an assessment of the ecological implications of this. Non-parametric multiplicative regression (NPMR) was used to visualize and understand the changes that have occurred between 2003–2018 in Lakes Garda, Como, Iseo, and Maggiore. In all four deep subalpine lakes, there has been a disruption from a traditional pattern of a significant spring chlorophyll-a peak followed by a clear water phase and summer/autumn peaks. This was replaced after 2010–2012, with lower spring peaks and a tendency for annual maxima to occur in summer. There was a tendency for this switch to be interspersed by a two-year period of low chlorophyll-a. Variables that were significant in NPMR included time, air temperature, total phosphorus, winter temperature, and winter values for the North Atlantic Oscillation. The change from spring to summer chlorophyll-a maxima, relatively sudden in an ecological context, could be interpreted as a regime shift. The cause was probably cascading effects from increased winter temperatures, reduced winter mixing, and altered nutrient dynamics. Future trends will depend on climate change and inter-decadal climate drivers.

scholarly journals Crustal variability along the rifted/sheared East African margin: a review

2021 ◽  
Vol 41 (2) ◽  
Author(s):  
Maren Vormann ◽  
Wilfried Jokat
Keyword(s):  
East Africa ◽  
Shear Zone ◽  
Structural Changes ◽  
The South ◽  
East African ◽  
The North ◽  
Rifted Margins ◽  
Continental Block ◽  
Seismic Lines ◽  
Southeastern Madagascar

AbstractThe East African margin between the Somali Basin in the north and the Natal Basin in the south formed as a result of the Jurassic/Cretaceous dispersal of Gondwana. While the initial movements between East and West Gondwana left (oblique) rifted margins behind, the subsequent southward drift of East Gondwana from 157 Ma onwards created a major shear zone, the Davie Fracture Zone (DFZ), along East Africa. To document the structural variability of the DFZ, several deep seismic lines were acquired off northern Mozambique. The profiles clearly indicate the structural changes along the shear zone from an elevated continental block in the south (14°–20°S) to non-elevated basement covered by up to 6-km-thick sediments in the north (9°–13°S). Here, we compile the geological/geophysical knowledge of five profiles along East Africa and interpret them in the context of one of the latest kinematic reconstructions. A pre-rift position of the detached continental sliver of the Davie Ridge between Tanzania/Kenya and southeastern Madagascar fits to this kinematic reconstruction without general changes of the rotation poles.

scholarly journals On the robustness of an eastern boundary upwelling ecosystem exposed to multiple stressors

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ndague Diogoul ◽  
Patrice Brehmer ◽  
Hervé Demarcq ◽  
Salaheddine El Ayoubi ◽  
Abou Thiam ◽  
...  
Keyword(s):  
Multiple Stressors ◽  
Marine Ecosystem ◽  
Trophic Levels ◽  
Sea Surface ◽  
Relative Index ◽  
Upwelling System ◽  
The North ◽  
Latitudinal Shift ◽  
Large Marine Ecosystem ◽  
North And South

AbstractThe resistance of an east border upwelling system was investigated using relative index of marine pelagic biomass estimates under a changing environment spanning 20-years in the strongly exploited southern Canary Current Large marine Ecosystem (sCCLME). We divided the sCCLME in two parts (north and south of Cap Blanc), based on oceanographic regimes. We delineated two size-based groups (“plankton” and “pelagic fish”) corresponding to lower and higher trophic levels, respectively. Over the 20-year period, all spatial remote sensing environmental variables increased significantly, except in the area south of Cap Blanc where sea surface Chlorophyll-a concentrations declined and the upwelling favorable wind was stable. Relative index of marine pelagic abundance was higher in the south area compared to the north area of Cap Blanc. No significant latitudinal shift to the mass center was detected, regardless of trophic level. Relative pelagic abundance did not change, suggesting sCCLME pelagic organisms were able to adapt to changing environmental conditions. Despite strong annual variability and the presence of major stressors (overfishing, climate change), the marine pelagic ressources, mainly fish and plankton remained relatively stable over the two decades, advancing our understanding on the resistance of this east border upwelling system.

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