Regional controls on geomorphology, hydrology, and ecosystem integrity in the Orinoco Delta, Venezuela

Abstract

Interacting river discharge, tidal oscillation, and tropical rainfall across the 22,000 km 2 Orinoco delta plain support diverse fresh and brackish water ecosystems. To develop environmental baseline information for this largely unpopulated region, we evaluate major coastal plain, shallow marine, and river systems of northeastern South America, which serves to identify principal sources and controls of water and sediment flow into, through, and out of the Orinoco Delta. The regional analysis includes a summary of the geology, hydrodynamics, sediment dynamics, and geomorphic characteristics of the Orinoco drainage basin, river, and delta system. Because the Amazon River is a major source of sediment deposited along the Orinoco coast, we summarize Amazon water and sediment input to the northeastern South American littoral zone. We investigate sediment dynamics and geomorphology of the Guiana coast, where marine processes and Holocene history are similar to the Orinoco coast. Major factors controlling Orinoco Delta water and sediment dynamics include the pronounced annual flood discharge; the uneven distribution of water and sediment discharge across the delta plain; discharge of large volumes of water with low sediment concentrations through the Río Grande and Araguao distributaries; water and sediment dynamics associated with the Guayana littoral current along the northeastern South American coast; inflow of large volumes of Amazon sediment to the Orinoco coast; development of a fresh water plume seaward of Boca Grande; disruption of the Guayana Current by Trinidad, Boca de Serpientes, and Gulf of Paria; and the constriction at Boca de Serpientes. D

Performance Evaluation of CRW Reef-Scale and Broad-Scale SST-Based Coral Monitoring Products in Fringing Reef Systems of Tobago

“…The island is located at approximately 11˝11 1 N, 60˝39 1 W and is in close proximity to the South American continent ( Figure 1). These reefs are exposed to extreme environmental conditions related to movement of the Inter-Tropical Convergence Zone (ITCZ) [27]; upwelling along the north coast of Venezuela [27]; and run-off from the Orinoco River delta,~250 km south of Tobago [28]. Tobago's fringing reefs are typically exposed to temperatures in the range 25-29˝C and annually experience sediment loading [29].…”

Sand Distribution along Shelf-Edge Deltaic Systems: A Case Study from Eastern Offshore Trinidad

“…The Orinoco basin covers about 1.1 x10 6 Km 2 of northern South America (Warne et al, 2002), drains about 35% of the Guayana Shield, 15% of the Andes and Coastal mountain ranges, and 50% of the Llanos region (percentages refer to drained surface area in these regions) (Warne et al, 2002). The annual Orinoco Delta sediment discharge is close to 150 x 10 6 metric tons / year and the delta-plain has an approximately area of 22,000 Km 2 (Warne et al, 2002).…”

“…The Guiana Littoral Current also acts as an along shore mechanism that has the capacity to transport as much as 50% of the total Amazon annual sediment discharge to the eastern offshore area of Trinidad and Venezuela, as a consequence the Columbus Basin also receives sediments from fluvial systems located to the south (Amazon, Essequibo and minor fluvial systems) (Eisma et al, 1978in Warne et al, 2002. The…”

“…Amazon sedimentary input is mainly composed by fine-grained sediments that are transported as suspended sediment load traveling along the northeastern South American shelf and reaching areas as distant as the Lesser Antilles in the eastern Caribbean (Warne et al, 2002). Once the sediments that are transported from the south as suspended sediment load reach the Trinidad area, a substantial portion of the sediments is transported landward by waves and tides and deposited along the Orinoco coast and shelf (McClelland Engineers, 1979), an also volumetrically significant portion of sediments is transported through Boca de Serpientes into the Gulf of Paria (Fugro Gulf, 1979;INTEVEP, 1981) and a small portion is transported northeastward along the south coast of Trinidad and then northward along the eastern margin of Trinidad (Koldewijn, 1958in Warne et al, 2002.…”

Vegetation - soils relationships in a wetland area of the Orinoco delta plain (Venezuela)

“…The prevailing climate type is moist tropical with precipitations surpassing 1.800 mm year -1 . Peat/ mud and silt/sand substrate alternate in this landscape, and hydromorphic entisol and histosols whith bad drainage, acidic pH, and low base exchange capacity are common [14]. The study area is located in the lower Orinoco delta plain, fig.…”