Hydrological seasonality and benthic algal biomass in a Neotropical floodplain river

Abstract

Our study evaluated spatiotemporal variation of physicochemical parameters and benthic and sestonic algal biomass in littoral areas of the main channel and floodplain lakes of the Cinaruco River, a lowland tributary of the Orinoco River in Venezuela. The Cinaruco is characterized by a highly predictable annual flood pulse, high transparency, and extremely low conductivity and suspended sediment load. During 2002 and 2003, 10 sites in the main channel and floodplain lagoons were sampled on 12 occasions. Correspondence analysis based on water physicochemical variables and algal biomass showed that ;80% of the variation in the multivariate space among sites and sampling dates was explained by 2 axes. During the high-water periods, river and lagoon sites showed high similarity in water variables and algal biomass. Conductivity, SiO 3 , and chlorophyll a concentrations (both benthic and sestonic) were low during the highwater phase. On the other hand, water variables and algal biomass differed between river and lagoon sites during the low-water period. The absence of flow in lagoons and consistently low algal biomass (sestonic and benthic) in river sites were the most important features of the spatial variability between main channel and lagoon sites during low-water phases. Benthic chlorophyll a was highly uniform at small spatial scales and significantly heterogeneous at large spatial scales. The annual flood regime of the Cinaruco, which drives the concentrations of dissolved materials and affects material interchanges between aquatic and terrestrial systems, also appears to be responsible for creating strong patterns of seasonal and spatial variation in benthic algal crops.

Seasonal dynamics of the structure of epiphytic algal community on different substrates from a Neotropical floodplain

“…average similarity, Contrib.% contribution percentage, Cum.% cumulative percentage of contribution epiphyton community, and other factors like connectivity, presence or absence of natural substrates can also affect this community (Rodrigues and Bicudo 2001;Fonseca and Rodrigues 2005;Algarte et al 2006Algarte et al , 2009. Several researchers emphasize the hydrology as an important factor associated with other attributes for the establishment of algae in floodplain lakes (Montoya et al 2006;Algarte et al 2006Algarte et al , 2009Weilhoefer et al 2008;Murakami et al 2009;Rodriguéz et al 2011), corroborating the findings of this study. During flood periods in floodplains, the environments tend to become homogeneous (Thomaz et al 2007).…”

Comparative feeding ecology and habitats use of Crenicichla species (Perciformes: Cichlidae) in a Venezuelan floodplain river

“…The Cinaruco is characterized by a low-gradient, sandy oligotrophic substrates, and high fish diversity (> 280 fish species) that spans a wide range of ecological attributes and life history strategies Willis et al, 2005). The Cinaruco River has a strongly seasonal hydrology with a pronounced annual wet and dry season (Montoya et al, 2006). During the wet season (May to October), the riparian forest and surrounding savanna is flooded, and organisms disperse widely throughout the river floodplain.…”

Linking fish colonization rates and water level change in littoral habitats of a Venezuelan floodplain river

“…Blackwater rivers in this region are characterized by low nutrients (dissolved inorganic nitrogen 0.5-2.0 lM, soluble reactive phosphorus 0.2-0.35 lM, see Montoya et al 2006), low pH (ranging from 5 to 7), high fish diversity, sandy bottoms, and scattered floodplain lagoons. Río La Guardia has a strongly seasonal hydrology with pronounced wet and dry seasons.…”

“…At the landscape-scale, these events drive numerous critical ecological processes. For example, many organisms have evolved life history strategies in conjunction with the seasonal flood cycle Delong et al 2001;Montoya et al 2006;Winemiller 2004), and water level change is essential for nutrient cycling and energy flow from basal resource pools to secondary consumers (Lewis et al 2000). But considered at the patch scale, seasonal water level change is a discrete disturbance to which organisms must respond (Grigg 1996;Lake 2003).…”