This study was carried out to evaluate species composition and distributions of phytoplanktonin relation to changes in some physicochemical characteristics of water in Dadinkowa Dam, Gombe State, Nigeria. Samples were collected using plankton net by hauling for five meters. Samples were kept in plastic containers and preserved in 4% formalin and logols iodine solution. 1 ml of sub-sample was observed under microscope. Physico-chemical parameters recorded include water temperature which ranged between 28 O C and 31.9°C, pH ranged from 7.1 to 8.9, Transperancy ranged from 0.06m to 0.16m, Dissolved oxygen range from 1.7 to 3.9mg/l and Conductivity ranged from 81 to 100µs/cm. 22 species of phytoplanktons were recorded and the maximum mean density was 92,105 cell/L and minimum was 44,317 cell/L. The dominant phytoplankton was Bacillariophyceae38.1%, followed by order Chlorophyceae 35.4%, Myxophyceae25.3% and Chrysophyceae 1.22%.(The phytoplankton varied significantly with months of sampling.

This study examined the integration of Remote Sensing and Geographic Information System (RS/GIS) for analyzing land use and land cover dynamics in Gombe Metropolitan, the Gombe State capital for the period 1976 to 2016. Land sat (TM) images of 1976, 1996and 2016 were used. The study employed supervised digital image classification method using Erdas Imagine 9.2 and Arc GIS 10.5 software and classified the land use into undisturbed vegetation, sparse vegetation, Settlements, Farmlands, Rock outcrops, Bare surfaces. The images were analyzed via georeferencing, image enhancement, image resampling and classification. The results obtained show an increasing settlements (from 0.36% - 4.01%) and farmlands (from 24.8% - 51.2%), over a decreasing of other LULC classes (bare surfaces, undisturbed and sparse vegetation, and rocky outcrops) for the time period of 1976 to 2016. These results could help city planners and policy makers to attain and sustain future urban development. It is therefore recommended that encouragement should be given to people to build towards the outskirts, like New mile 3 and Tumfure, etc through the provision of incentives and forces of attraction that is available at the city center in these areas to avoid the problem of overcrowdings.

No abstract

Benthic invertebrate communities have been shown to respond to habitat  degradation as a result of land use changes. Although these changes have been well documented in temperate regions, their effects in the tropics have been poorly documented particularly where land use activities differ markedly (e.g., tea, maize and plantations). A survey 55 1st and 2nd order highland tropical streams, across four land use categories, ranging from continuous tropical montane rain forest to intensive crops and pasture. Streams were sampled in the tropical dry season (October–March) for physico-chemical parameters and components of the biological community, (i.e., fine particulate organic matter [FPOM], coarse particulate organic matter [CPOM], algae and benthic invertebrates). Catchment riparian conditions and human water use activities were used to generate a multivariate land use intensity gradient score. Temperatures in pasture streams were warmer than forest streams (up to 25oC) and dissolved oxygen levels frequently low (15–79%). However, physico-chemical conditions did not show any clear patterns across land uses categories. In contrast, benthic invertebrate communities showed strong response with the highest taxonomic diversity in continuous forest streams (mean 20 taxa) and the lowest in streams with intensive crops (e.g., cabbage crops, mean 8 taxa). Marked changes were found in invertebrate communities with several taxa occurring primarily in forested streams (e.g., the mayflies Heptageniidae and Oligoneuriidae and brachyuran crabs). Tropical land use farming (e.g., tea, maize, cabbage) have significant impacts on the benthic invertebrate assemblages of highland streams in Nigeria. However, not all crop and plantation streams had highly impacted communities because some have wider riparian buffer zones. This study further highlight the importance of conservation and management of montane forest fragments in these regionsKeywords: Tropical, Nigeria, highland, benthic invertebrates, land use, degradation

The structure and properties of tropical stream food webs were investigated in nine second and third order streams, three in continuous sub-montane forest, three in tea plantations and three in maize fields. All were located on the Mambilla Plateau, north-east Nigeria. Components of all trophic levels (e.g., fine particulate organic matter [FPOM], coarse particulate organic matter [CPOM], algae, benthic invertebrates and fish) were sampled, and analysed by examination of gut contents and using stable isotopes techniques. Gut contents of key invertebrate species were categorised into eight types of food items: filamentous algae, diatoms, fungi, CPOM ≥ 1 mm (usually leaf litter and wood fragments), FPOM 1 mm (often amorphous detritus) and animal parts. Several food web properties were calculated and a basic food web was constructed using density data. Invertebrate species richness and density were higher in forest than in tea plantations and maize fields. Community and dietary analyses revealed that streams in the tea plantation and maize fields had simpler food webs incorporating fewer species and shorter food chains than those in continuous forest. However, potamonautid crabs (macroconsumers) and fish were present in all streams. Significant differences occured in three food web parameters calculated for streams in catchments differing in land uses: web size (ANOVA F2, 6 = 15.509, P = 0.004), predator prey ratio (ANOVA F2, 6 = 17.337, P = 0.003), standing biomass of invertebrates (AFDM); CPOM mass (ANOVA F2, 6 = 8.727, P = 0.016) and algal (ANOVA F2, 6 = 37.599, P = 0.001). Stable isotope analysis revealed that primary consumers assimilated a mixture of autochthonous and allochthonous carbon resources (CPOM and algae) in all streams.