Contrasting responses of two Caribbean mangroves to sea-level rise in the Guajira Peninsula (Colombian Caribbean)

Local geomorphology plays an important role in the response of mangrove communities to both sea-level rise and precipitation changes, mostly because it exerts an important control of the erosion-progradation balance. Here we present contrasting changes in the palynological records of two sediment cores retrieved from locations occupied by mangroves in the northeastern Caribbean coast of Colombia: Calancala and Navio Quebrado. Sediments were treated with standard procedures used in palynologycal analysis, and dated with AMS C-14 and Pb-210. Age-depth models of both cores were constructed by linear interpolation between dated samples. The main modern differences between the studied sites are fresh water availability and sediment supply throughout the year. While Calancala, located at the Rancheria River Delta, has direct fresh water influence throughout the year, coastal lagoon Navio Quebrado is only sporadically influenced by fresh water sources. According to our findings, two main factors contributed to mangrove establishment in the Colombian Caribbean: i) high and accelerated sea-level rise around 6000 cal yr BP originating coastal lagoons that favored Mangrove establishment, and ii) marine still stand and high precipitation around 3000 cal yr BP leading to a second wave of mangrove expansion. A drought between about 2850 and 2450 cal yr BP and the strengthening of easterly trade winds caused a change from Rhizaphora-dominated to Avicennia-dominated stands. Increased precipitation after 2500 cal yr BP and subsequent increase of fluvial sediment input promoted recovery of Rhizophora-dominated mangroves. Sea-level rise during the last 150 yr has caused landward mangrove expansions in deltas and progradation of coastal environments. However, the general pattern shows a net loss of mangrove vegetation as the result of coastal erosion. (c) 2012 Elsevier B.V. All rights reserved.