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The Mayfly Newsletter

Influence of technical maintenance measures on ecological status of agricultural lowland rivers - Systematic review and implications for river management.

Water is an essential resource required for the sustainance of life. Water is utilized in all sector of any nation economy. Surface water is one of the major sources of water utilized by several communities in coastal region of Bayelsa state. Fishing - a source of livelihood for indigenous people of Bayelsa state is carried out in surface water. Surface water is also a route of transportation using engine boat and canoe. Some of the surface water are used for domestic purposes (such as washing, bathing, cooking) and even drinking. Several anthropogenic activities are carried out in the surface water including dredging, makeshift refinery and dumpsite for various classes of wastes (mainly from domestic and sewage). This paper reviews the impacts of anthropogenic activities in surface water resources in Bayelsa state, Nigeria. The study found that pH, temperature, conductivity, total suspended solid, total dissolved solid, total hardness, total alkalinity, turbidity, nitrite, nitrate, phosphate, sulphate, chloride, sodium, potassium, magnesium, calcium, zinc, copper, iron, lead, cadmium, chromium, lead, mercury and total hydrocarbon content are altered due to various anthropogenic activities. Off these, turbidity is significantly affected by all the activities and to lesser extent pH, total alkalinity, dissolved oxygen, nitrite, magnesium, total hydrocarbon content, iron and lead are also affected above permissible level recommended Standard Organization of Nigeria and the World Health Organization. The alteration of water quality parameters could alter the composition and abundance of biodiversity including fisheries and planktons, downstream application of the water and its potability. This study concludes by suggesting that factors leading to alteration in water quality should be checkmated by appropriate regulatory agencies.

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Review of Impact of Anthropogenic Activities in Surface Water Resources in the Niger Delta Region of Nigeria: A Case of Bayelsa State

Guide to Identification of Marine and Estuarine Invertebrates. Cape Hatteras to the Bay of Fundy.Kenneth L. Gosner

Using the example of a regulated stretch of the Krąpiel River (NW Poland), an analysis of the impact of dredging on the aquatic beetle (Coleoptera) fauna was made. After dredging the beetle fauna became markedly poorer quantitatively and had lower species diversity. Moreover, the qualitative composition and dominance structure were highly transformed. However, species number and diversity increased rapidly and were restored within just half a year. The structure of the restored fauna was most strongly influenced by vegetation, flow velocity and bottom sediment composition. The first to colonize the river were eurytopic beetles and species typical of small water bodies, which had significant refuges in the form of fish ponds bordering on the river; these species dominated the assemblage throughout the study period. Rheophiles with less dispersal power appeared later, and finally rheobionts, in low numbers but occupying an increasing number of sampling sites.

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The impact of dredging of a small lowland river on water beetle fauna (Coleoptera)

The macrobenthic invertebrates of a canal, created from a tributary of the Warri River in the mangrove swamp of the Niger Delta, Nigeria, were studied before and after dredging. In the canal dredging resulted in at least a 93% decrease in the benthic population while the Margalef's diversity index reduced from 3.8 to 1.4. Of the 15 species identified during the pre-dredging studies, only Nereis operta and Baetis sp. were recovered after dredging. The site 500m downstream of the canal was also slightly impacted, showing a 31% decrease in population. We conclude that the drastic reduction of benthic species is due to the direct destruction of benthic species, larvae and habitat, as well as settling turbidity plumes, reduction of sediment nutrients, physical disturbance and, physiological and toxic stress. To conserve biodiversity it is recommended that mitigation measures should be put in place by stakeholders involved in dredging and that long-term monitoring of dredged canals is carried out to ensure that...

MO Benka-Coker

Papers

The impact of dredging on macrobenthic invertebrates in a tributary of the Warri River, Niger delta