Modeling temporal variations of Gracilaria Greville and Hypnea J.V. Lamouroux (Rhodophyta) assemblages on a midlittoral reef platform at Piedade Beach, Pernambuco State, Brazil

Abstract

-(Modeling temporal variations of Gracilaria Greville and Hypnea J.V. Lamouroux (Rhodophyta) assemblages on a midlittoral reef platform at Piedade Beach, Pernambuco State, Brazil). The diversity of algal banks composed of species out the genera Gracilaria Greville and Hypnea J.V. Lamouroux have been impacted by commercial exploitation and coastal eutrophication. The present study sought to construct dynamic models based on algal physiology to simulate seasonal variations in the biomasses of Gracilaria and Hypnea an intertidal reef at Piedade Beach in Jaboatão dos Guararapes, Pernambuco State, Brazil. Five 20 × 20 cm plots in a reef pool on a midlittoral reef platform were randomly sampled during April, June, August, October, and December/2009 and in January and March/2010. Water temperature, pH, irradiance, oxygen and salinity levels as well as the concentrations of ammonia, nitrate and phosphate were measured at the sampling site. Forcing functions were employed in the model to represent abiotic factors, and algal decay was simulated with a dispersal function. Algal growth was modeled using a logistic function and was found to be sensitive to temperature and salinity. Maximum absorption rates of ammonia and phosphate were higher in Hypnea than in Gracilaria, indicating that the former takes up nutrients more effi ciently at higher concentrations. Gracilaria biomass peaked at approximately 120 g (dry weight m -2 ) in March/2010 and was signifi cantly lower in August/2009; Hypnea biomasses, on the other hand, did not show any signifi cant variations among the different months, indicating that resource competition may infl uence the productivity of these algae.

Temporal and Spatial Variation of Benthic Intertidal Community of a Sandstone Reef in Pernambuco Brazil as a Tool to Evaluate Bioinvasion

“…The coastal reefs of the urban Pernambuco regions suffer with algal overgrowth that in intertidal regions compete mainly with mollusks and crustaceans. These algae grow attached to the substrate or as drift in reef pools [1][2][3]. The increase in biomass and cover of substrate is related to the increment in nutrients and available light after the rainy season, with predictable nutrient accumulation in the algal thallus.…”

“…The increase in biomass and cover of substrate is related to the increment in nutrients and available light after the rainy season, with predictable nutrient accumulation in the algal thallus. Algae, specially the perennial, are affected by the waves action, which cause algal drift on the coast that can happen also with the filamentous green algae [3]. The sedimentation and species' invasion are other harmful factors that affect the reefs.…”