Now showing items 21-40 of 274

    • Sensitivity of Seychelles Coastal Areas to Possible Significant Sea-Level Changes.

      Chang-Ko, L.A. (1991)
      Because of the nature of the coastlines, small islands like the Seychelles, are the most vulnerable to any significant change in sea-level. A gradual rise in Mean Sea-Level (MSL) of about 1 meter over a period of one century. will not be a critical issue. There is enough time for human adaptation. What we should be most concerned about is the overall impact of Climate Change on the Seychelles Islands. As a result of global warming, it is expected that there will be an increase in the frequency and severity of tropical cyclones within Seychelles Exclusive Economic Zone (EEZ). Furthermore, there is the likelihood of the occurrences of intense tropical cyclones even within the granitic group of islands, which is hardly affected today, because of close proximity to the equator. The worst scenario would be the simultaneous occurrence of a flash flood and an abnormal high tide. Surges in sea-level can be due to both meteorological or geological phenomena.
    • A Review of the Impacts of Sea Level Rise to Coral Assemblages of the Kenyan Reefs.

      Mutere, J. (1991)
      The Kenyan coastline is characterized by a fringing reef, which varies in width from a few meters to almost 2 kilometers. Due to the elevated nature of the reef, large areas of it are over-exposed at low tide and their upper surfaces are covered by bare rock, sand patches, scattered coral, seagrasses and algae. Sea level rise will cause changes in the coral reef community structure itself. This will be mainly in the back reef region where there will be increased wave energy and less exposure during the low tides. More of this continental shelf area will be available for colonization, resulting in an increased width of active back reef area. The typical pocilloporid and poritid assemblages will give way to new species assemblages which will be either of mixed or monospecific stands. These would lead to increased habitat diversity. It would also increase and stabilize the rate of sedimentation and encourage the development of soft substrate associated and burrowing organisms.
    • The effects of Relative Mean Sea Level changes on Aquaculture Practices and Development in Kenya.

      Radull, J. (1991)
      This paper will therefore, discuss the effects of Relative Mean Sea Level (RMSL) changes on these environments in relation to aquaculture practice and development. Possible causes of Relative Mean Sea Level changes and their possible effects on estuarine and coastal flatlands of the Kenya coast.
    • Effects of Sea Level Changes on Coastal Human Settlement Examples from Tanzania.

      Wembah-Rashid, J.A.R. (1991)
      There are several reasons that may contribute to the emergence and growth of settlements as well as their decay and disappearance. In this presentation I am suggesting that one of the principal reasons for the emergence and prosperity or decay and disappearance of settlements along the coast of mainland Tanzania is the changes in sea level in the area. For, such changes positively or adversely affect the security, economic viability and continued smooth contact with external people, among other things. To make my suggestions more concrete I want to focus on four major sections of the Tanzania mainland coast, namely Bagamoyo, Dar-es-Salaam, Kilwa and Mikindani. This choice is deliberate because it is from there that we have sources that point to the issues addressed by this workshop.
    • Implications of Sea Level Rise on Rocky Cliff and Mangrove Macroalgae In Kenya.

      Oyieke, H.A. (1991)
      This study was carried out in order to establish the species of macroalgae that would be most vulnerable to the effects of sea IeveI rise. The zonation of on-encrusting macroaIgae on rocky cliffs and mangroves was determined. In the zonation 21 species which frequently appeared in specific zones are described. Adapting the shore terminology of Lewis (1964) and Hartnoll (1976) the patterns of zonation of the species were as follows: (a) Littoral fringe - Bostrychia binderi,B. tenella (Rhodophyta) and Chaetomorpha brachygonia (Chlorophyta). (b) Upper eulittoral zone - Catanella caespitosa, Caulacanthus ustulatus, Centroceras elavulatum (c. Ag.) Montagne Ceramium camouii, Lophosiphonia reptabunda, Murayella periclados (Rhodophyta) Caulerpa fastigiata, Cladophora patetentirameae, Cladophoropsis sundanensisi, Enteromorpha kylinii E. ramuulosa (Chlorophyta). (c) Lower eulittoral zone - Acrocystis nana, Gracilaria salicornia (Rhodophyta) Rhizoclonium grande and Ulva pertusa (Chlorophyta). Similarity in species composition appeared between the cliff and mangrove specimens apart from Bostrychia radicans, Platysiphonia minita and Valonia aegagropila which appeared more commonly among the mangrove specimens. The composition of species among the mangroves in a muddy habitat was richer than in the mangroves in a sandy habitat. The implications of sea level rise on the distribution of these macroalgae is discussed.
    • Eroding Kenyan Shorelines: the Need for Geological Input Into Shoreline Management, Decisions and Strategy.

      Odada, E. (1991)
      This paper examines the consequences of responding to rising sea level by stabilization (halting of shoreline retreat by engineering means). Totally new ideas and approaches to shoreline management that incorporate the very significant advances in geological understanding of shoreline processes are also explored. Most of stabilization along the Kenya shores has been done and is being carried out without consideration or understanding of fundamental principles of shoreline processes. Failure to consider scientific principles often leads to severe degradation or total loss of our valuable natural resource, the open ocean beach.
    • Rates and Causes of Coastal Erosion on the Zanzibar Island.

      Nyandwi, N.; Muzuka, A.N.N. (1991)
      Studies on coastal erosion on the Zanzibar Island were made through field measurements, aerial photoanalysis and interviews with the old section of the village communities around the eroded areas. Alarming rates of coastal erosion over the past four decades were deduced. Whereas estimates of erosion rates obtained from interviews in the north where the problem is much more serious gave figures of more then 150m in a period of 5 to 6 years, aerial photoanalysis indicate higher average annual rates of more than 40m between 1947 and 1977. Recent field measurements at Maruhubi, north of Zanzibar township gave annual coastal erosion rate of 3m. The high rates of coastal erosion were found to be caused by the high wave activity during some periods of the monsoons amplified by a high tidal range. Destruction of the protective mangrove forests adding to the problem. The unconsolidated rock formations and tectonic activity on the western coast were found to be the causes of comparatively intensive erosion than on the east coast.
    • Effects of Sea Level Fluctuations on Groundwater Quality along the Kenyan Coast.

      Mailu, G.M.; Muturi, H.R. (1991)
      The effects of sea level fluctuations on groundwater quality along the Kenyan coast have been studied with particular reference to the south coast. The study area lies between Mombasa Island to the north and Kenya-Tanzania border to the south. The western extent of the area from the Indian Ocean is marked by the area underlain by Maji-ya-Chumvi Beds. It is bounded by latitudes 4~’00' and 4~’45' south and longitudes 39~’00' and 39~’45 east. The area has experienced a number of sea level fluctuations between Triassic and Quaternary Periods. The fluctuations have occasioned deposition of various sedimentary rocks which have significant influence on groundwater quality. The results of data analysis of water samples from boreholes, wells and springs in the study area have indicated that unconsolidated sands have the best water quality and the shales have the poorest water quality. Water of intermediate quality is tapped in sandstones and limestones. Detailed investigations on the least understood aspects have been recommended. These include sea water intrusion into groundwater, mode of occurrence of springs at low tide along the beach, fresh water in sand dunes along the coast line and the potential of Lagoonal Sands as a source of water supply along the coast.
    • Implications of Rising Sea Level to Low Lying Land Masses such as Lamu.

      Kabubo, C.K. (1991)
      Inorder to have an understanding of various options available, this paper attempts to discuss causes of sea erosion in general and the various methods that can be, used to protect against erosion in various circumstances. An over-view at the end gives an indication of what may eventually be used for Lamu and similar low-lying masses.
    • The Effect of Sea Level Changes on Geomorphological Processes Along the Coast.

      Kapule, D.E. (1991)
      Geomorphological processes at work on the coastal landforms are influenced by a number of environmental factors. The coastal area is a scene of interaction between different spheres of the earth like hydrosphere, lithosphere, atmosphere, biosphere and technosphere. Each of these spheres has its own influence on the development of the coastal landforms. This paper tries to explain the effect of the sea level change on geomorphological processes taking into account the influence imparted by each of the attributes of the above mentioned spheres. The understanding of these processes will enable the effects of various human interferences to be predicted and are important in coastal land management and conservation of coastal natural resources.
    • Possible Effects of a 20-140 cm Sea Water Rise on the East African Coast.

      Kudoja, W.M. (1991)
      A rise of between twenty and one hundred and forty centimetres of sea level will obviously bring about effects on the marine organisms, human structures and settlements on the E.A. Coast. The sea level rise will affect survival and distribution of marine organisms and destruction of some human settlements and structures e.g. hotels. Perhaps the hardest hit organisms will be benthic rocky shore organisms i.e. cirripeds (barnacles), bivalves (Crassostrea spp.) and gastropods (Littorina spp). Intertidal organisms e.g. crabs Uca spp., Dotilla spp. worms, polychaetes, Arenicola spp. Echiurids and Sipinculids will have to die due to permanent submergence. The swimming crabs on the other hand will not be affected e.g. Portunus pelagicus, Scylla serrata and Thalamita spp. due to their ability to emigrate. Due to the permanent submergence of the intertidal area, the marine birds will have to emigrate as their food will be inaccessible. Coral reefs that are in the deeper parts of the ocean will die eventually due to the decrease in light intensity which is essential for survival of the zooxanthellae. Sea grass beds will move shorewards with the presence of water, the fishery for octopi and Anadara spp. will never be possible due to the permanent presence of sea-water. The mangrove species found in the upper littoral zone i.e. Lumnitzera racemosa and Avicenia marina might die as they are not used to permanent submergence in sea water. Aquaculture will not be as affected as salt-works which will take longer to evaporate the sea water. Coastal hotels and the harbour will be flooded by this sea level rise. The solution to this at the moment will be to start building dykes around coastal structures. For the future all coastal structures will have to be built at least three metres above sea level.
    • Weight-Length Relationships for Certain Scombroid Fishes from the Equatorial Western Indian Ocean.

      Merrett, N.R. (1968)
      East African Agricultural and Forestry Journal
      The East African Marine Fisheries Research Organization (E.A.M.F.R.O.) is at present conducting a tuna longline survey in the equatorial western Indian Ocean. During this survey, which began in September 1964. The weights and lengths of all specimens of scombroid species caught have been recorded. Sufficient data have now been collected from three species of tuna and two species of billfish to enable the calculation of reliable weight-length relationships. The species of tuna considered are the yellowfin, Thunnus albacares (Bonnaterre), albacore. Thunnus alalunga (Bonnaterre) and skipjack, Euthynnus pelamis (Linnaeus). The billfish examined were the striped marlin. Tetrapterus audax Phillipi and the sailfish, Istiophorus gladius (Bloch).
    • Community-Level Marine Resource Management and the Spirit Realm in Coastal Kenya.

      Glaesel, Heidi (2000)
      Women in Natural Resources (WiNR)
      Regulations are set by fishing community leaders in coastal Kenya to maintain social control and access to critical community resources through mediation with the spirit world. Although fishing regulations set by these leaders (elders) may result in conservation effect, indigenous conservation originated in practices that focused on satisfying human needs and reducing anxieties about society. It did not originate from altruistic concern for the environment (Western and Wright 1994). Concern for conserving plants. animals. and habitats stemmed from beliefs that each could house spirits whose placation was crucial to the well being of society. As catches have declined, temporarily and over the longer term, younger Kenyans' faith in their elders' ability to combine with sea spirits has waned and elders' authority has been challenged, leading to inter-generational conflicts (Photo 1). In addition, traditional beliefs have gradually been eroded in the face of pressures to adopt conventional Islamic practices. Fo~ example, in -recent decades, increasing literacy among younger generations of Muslims, their distress over low and declining catches, and elders' seeming inability to correct the situation has led to efforts, especially by youths, to separate practices concerning the spirit realm into those clearly acceptable in Islam as described in the Koran, and those of more ”pagan” origins (Parkin 1968). These inter-generational conflicts have fractured local fishing communities. and decreased their ability to deter non-locals and users of environmentally destructive fishing techniques from entering the fishery.
    • Notes on Kenya Acetabularia lamouroux, (Chlorophyta).

      Moorjani, Shakuntala A. (1970)
      Journal of East African Natural History Society
      In this paper three species of Acetabularia are reported for the Kenya coast. The first of these Acetabularla was recorded in April, 1968. A piece of old coral on which Udotea orientalis A. & E. S. Gepp, were growing was collected on the coral reef at Diani Beach and brought to Nairobi to make further observations on this species. On this piece of old coral there appeared an Acerabularia which was identified as A. moebii Solms-Laubach by Prof. Wm. E. Isaac.
    • Kasa News: a newsletter of the Kenya Sea Turtle Conservation Committee (KESCOM) 8th Edition, 2003.

      Kenya Sea Turtle Conservation Committee (KESCOM) (Kenya Sea Turtle Conservation Committee (KESCOM), 2003)
      The newsletter describes various news articles, events, activities and information of relevance to the Kenya Sea Turtle Conservation Committee (KESCOM).
    • A cost effective light trap for sampling tropical fish and crustacean larvae.

      Mwaluma, J.M.; Kaunda-Arara, B.; Osore, M.K.; Rasowo, J. (2009)
      Western Indian Ocean Journal of Marine Science
      A simple and relatively cheap locally-assembled light trap was used to sample pre-settlement fish larvae in the Malindi Marine Park, Kenya, for two years. The trap was assembled locally using a water dispenser bottle, plastic bottle necks, buckets, 12V rechargeable alkaline batteries and a diver’s dry box. The light unit consisted of a 12 V rechargeable alkaline Jacob’s battery that powered a 12 volt energy saving fluorescent bulb of 11Watts. The catch potential and composition of fish larvae sampled using the trap is presented. The technical and functional problems encountered during the construction and operation of the light traps are presented, and improvements suggested. We compare the performance, costs and efficiency of this trap with light-traps used elsewhere in the world. In addition to fish larvae, the traps have potential use in qualitative sampling of crustacean larvae and ornamental fishes for the aquarium trade.
    • Zooxanthellae Densities are Highest in Summer Months in Equatorial Corals in Kenya.

      Mwaura, J.; Grimsditch, G.; Kilonzo, J.; Amiyo, N.; Obura, D. (2009)
      Western Indian Ocean Journal of Marine Science
      Coral bleaching (loss of zooxathellae) is an increasing problem for the health and persistence of corals, but the phenomenon can not be fully comprehended without understanding seasonal fluctuations in the field. Seasonal dynamics of coral zooxanthellae (population density and mitotic indices) of eleven scleractinian coral species (Acropora sp., Echinopora gemmacea, Favia sp., Galaxea fascicularis, Hydnophora microconos, Montipora aequituberculata, Pavona decussata, Pocillopora damicornis, Pocillopora eydouxi, Porites cylindrica and Porites lutea) were monitored in Mombasa Marine Park from 1998 to 2006. Direct tracking of mapped corals provided evidence that zooxanthellae densities were highest during the North-East Monsoon (NEM) season and displayed highest mitotic indices during transition periods directly preceding this season. The higher densities found during the northeast monsoon (when temperatures and light radiation levels are higher) are surprising as they are contrary to trends found at higher latitudes. It is possible that at higher latitudes seasonal variability of temperatures and light is so great that it dictates zooxanthellae density dynamics, while corals closer to the Equator are less influenced and other factors may have greater influence on zooxanthellae dynamics. The present study highlights the degree of variability of zooxanthellae dynamics that may exist among coral species and compares sites from widely different geographic locations.
    • The breeding pattern and variations in timing and reproductive output of the commercial sea cucumber Holothuria fuscogilva in Kenya.

      Muthiga, N.A.; Kawaka, J.A. (2009)
      Western Indian Ocean Journal of Marine Science
      The sea cucumber Holothuria fuscogilva is currently one of the most commercially valuable species of sea cucumber worldwide. This study investigated reproduction of this species in order to characterize the reproductive pattern and evaluate the relationship with temperature, light and lunar periodicity. Individuals were collected monthly, between 1998 and 2007, at Shimoni, Kenya and processed using standard gonad index methods and macroscopic and microscopic observations of the gonads. Gametogenesis commenced from May and spawning occurred from December to April of each year and there was close synchrony between the sexes, contrary to the hypothesis that breeding patterns on the equator will be continuous and less synchronized between sexes. Peak spawning occurred during the last quarter of the moon. The gonad index of individuals correlated significantly with gonad tubule length and fecundity indicating that it was a good predictor of sexual maturity and reproductive output. The gonad index showed a significant correlation with temperature but not light, suggesting that temperature may play a role in controlling reproduction. The life history strategy of this sea cucumber included a higher energetic investment in the reproductive output of females and spawning at a time favorable for larval development. There was a shift in sex ratio from unity to significantly more males over the sampling period, as well as a significant reduction in mean sizes (body wall weight) and reproductive output (gonad index) suggesting that the reproductive success of this species was potentially negatively affected by fishing.
    • The Status of the Dugong (Dugong dugon Muller); Kenya, 1961.

      Jarman, P.J. (1966)
      East African Wildlife Journal
      The scarcity of dugong (Dugong dugon Muller) throughout their former range and lack of knowledge of the species' ecology justifies this record of the opinions of the fishermen in the Lamu district of Kenya, where the species is still plentiful. The area and the programme of questioning are described. The social life, reproduction, movements and predators of the dugong are recorded as reported by the fishermen. The present distribution is contrasted with the past. My observations on the food plants and their distribution are given, as well as the fishermen's estimation of the part each plays in the dugong's diet. The need for calm water over feeding grounds, afforded by depth of water or shelter from winds, seems to be a controlling factor in the distribution of dugong. Man appears to be the main predator.
    • Estimate of Water Residence Times in Tudor Creek, Kenya Based on Sea Surface Heat Fluxes and Observations of the Horizontal Temperature Gradient During Different Seasons.

      Nguli, M.M.; Rydberg, L.; Francis, J. (2006)
      Western Indian Ocean Journal of Marine Science
      Salinity and temperature measurements were carried out in Tudor Creek, Kenya from 1995-98 in order to determine water exchange between the creek and the adjacent Indian Ocean. Data from the Kenya Meteorological Department including gauging data from two smalI rivers were employed to estimate long-term rainfalL evaporation and river runoff. However, even though the observed salinity gradient in the creek appeared consistent with dry and rain periods, estimates of river runoffs were not good enough to calculate water exchange, based on salt conservation. Runoff in general was also too small to give reliable rating curves (correlation between rainfalI and river runoff). For this reason, heat conservation was used for the calculation of water exchange. Although estimates of sea surface heat fluxes were based on coarse global climatology data with large seasonal variations in the net heat flux (from 50- 150 Wm-2), the result was surprisingly consistent, with similar water exchange during all different seasons. Residence times for the creek waters in relation to the ocean water are between 3-5 days, 5 days for the waters inside the deep inlet. During spring tides, the exchange is about twice as large as during neap tides.