Abstract
The objective of this study was to determine the effects of land-use patterns on both diatom community composition and water quality in tropical streams during the dry season. Benthic diatom collections and water quality sampling were done 4 times at 10 sites. A suite of environmental variables that varied with human land-use pattern was assessed to find the combination of variables that best explained patterns of diatom community composition. Canonical Correspondence Analysis (CCA) was used to determine environmental gradients along which species were distributed. A clear relationship between both benthic diatom communities and water quality and land-use pattern was observed with species richness, diversity and evenness, decreasing significantly from the agricultural and forest area to the urban area. Upstream, forested, agricultural sites, with good water quality (BOD5 = 0.9 to 2.6 mg∙l-1, DO = 6.8 to 8.2 mg∙l-1, phosphate = >2 to 4.7 μg∙l-1), were characterised by Thalassiosira weissflogii, Orthoseira dentroteres, Meridion anceps, Melosira varians, Diatoma spp, Diadesmis contenta, Eunotia papillo, E. bilunaris, E. intermedia, E. sudetica, Aulacoseira alpigena, A. ambigua, Cymbopleura naviculiformis and Stauroneis phoenicenteron . Urban sites, with medium to bad water quality (BOD5 = ~7 mg∙l-1, DO = ~7 mg∙l-1, phosphate = 12.6 to 83.1 μg∙l-1), were characterised by Diadesmis dissimilis, Frustulia rhomboids, Nitzschia scalaris, Nitzschia linearis, Cyclotella pseudostelligera Neidium ampliatum, N. affine, Encyonema silesiacum, E. neomesianum, Aulacoseira granulata, Navicula cryptotenella, Pinnularia legumen, P. gibba, P. divergens, Surirella linearis, S. robusta, and Achnanthidium minutissimum. Downstream urban sites, with very bad water quality (BOD5 = 19.5 to 26.2 mg∙l-1, DO = 0.4 to 1.9 mg∙l-1, phosphate = 142.5 to 248.7 μg∙l-1), were characterised by Gomphonema parvulum, G. accuminatum, Nitzschia palea, Nupela praecipua, Sellaphora pupula, Planotidium lanceolata, Fallacia monoculata and Pinnularia subcapitata. Diatom communities demonstrated potential for acting as indicators of changes in water quality due to changes in catchment land-use patterns. Keywords: land-use, benthic diatoms, environmental gradient, agricultural, forests, urban
Highlights
Land-use – a function of cultural and settlement patterns, economic factors and environmental characteristics (Robbins et al, 1983; Black et al, 1998) – and water resources are unequivocally linked
Diatom community structure showed a clear relationship with changes in water quality associated with changes in land-use pattern
Species richness, diversity and evenness decreased along a forest and agricultural to urban land-use gradient
Summary
Land-use – a function of cultural and settlement patterns, economic factors and environmental characteristics (Robbins et al, 1983; Black et al, 1998) – and water resources ( biotic communities supported by these water resources) are unequivocally linked. Showed that land-use had a distinct overall and seasonal effect on water quality (Osborne and Wiley, 1988). Studies in Pinelands of New Jersey showed substantial land-use effects on natural water quality because of agricultural development, urban densities, and domestic wastewater flow (Zampella, 1994). Phosphorus, increases with urban development due to stormwater runoff (Osborne and Willey, 1988; Welch et al, 1998). Increase in nutrient concentration is a result of other catchment activities, such as runoff from agriculture or sewage treatment plants. Changes in water quality of lotic systems because of surrounding land-use patterns affects the resulting biotic communities, as the patterns of this biota are responsive to the nature of the prevailing physical and chemical conditions
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
