Trophic model of the outer continental shelf and upper slope demersal community of the southeastern Brazilian Bight (original) (raw)
Related papers
Trophic models of São Sebastião Channel and continental
2015
Abstract. Two trophic models of the São Sebastião ecosystems were built to evaluate differences in their size and organization. The study area is located on the southeastern coast of Brazil. The trophic groups of the systems were based on ecologically or taxonomically related species, considering their relative abundance and similarity of diets and habits. The models, based on the Ecopath software, consist of six fish groups, ten invertebrate groups, Bacterioplankton, Phytoplankton, Zooplankton, and Detritus. Biomass, production, and consumption were estimated for the Inner shelf and the Channel. Primary production was estimated as 2,436 g wet weight m-2 year-1 on the inner shelf and 1,441 g WW in the channel. Total benthic production was 215.8 and 418.1 g WW.m-2.yr-1 on the inner shelf and the channel, respectively. Total fish production plus Cephalopoda was 4.9 g WW.m-2.year-1 in the inner shelf and 11.5 g in the channel. Total system throughput was 8161 g WW.m-2.year-1 in the inn...
Large-scale patterns of benthic marine communities in the Brazilian Province
As marine ecosystems are influenced by global and regional processes, standardized information on community structure has become crucial for assessing broad-scale responses to natural and anthropogenic disturbances. Extensive biogeographic provinces, such as the Brazilian Province in the southwest Atlantic, present numerous theoretical and methodologi-cal challenges for understanding community patterns on a macroecological scale. In particular , the Brazilian Province is composed of a complex system of heterogeneous reefs and a few offshore islands, with contrasting histories and geophysical-chemical environments. Despite the large extent of the Brazilian Province (almost 8,000 kilometers), most studies of shallow benthic communities are qualitative surveys and/or have been geographically restricted. We quantified community structure of shallow reef habitats from 0˚to 27˚S latitude using a standard photographic quadrat technique. Percent cover data indicated that benthic communities of Brazilian reefs were dominated by algal turfs and frondose macroal-gae, with low percent cover of reef-building corals. Community composition differed significantly among localities, mostly because of their macroalgal abundance, despite reef type or geographic region, with no evident latitudinal pattern. Benthic diversity was lower in the tropics , contrary to the general latitudinal diversity gradient pattern. Richness peaked at mid-latitudes , between 20˚S to 23˚S, where it was ~3.5-fold higher than localities with the lowest richness. This study provides the first large-scale description of benthic communities along the southwestern Atlantic, providing a baseline for macroecological comparisons and evaluation of future impacts. Moreover, the new understanding of richness distribution along Brazilian reefs will contribute to conservation planning efforts, such as management strategies and the spatial prioritization for the creation of new marine protected areas.
Aquatic Conservation-marine and Freshwater Ecosystems, 2009
1.Mass balanced trophic models and dynamic simulations of two benthic ecological systems from La Rinconada Marine Reserve (Antofagasta Bay, SE Pacific) were constructed.2.The scallop Argopecten purpuratus is the most important benthic resource in La Rinconada Marine Reserve, followed by the carnivorous snail Thais chocolata, and the filter-feeder bivalves Tagelus dombeii and Transennella pannosa.3.Information on biomass, P/B ratios, catches, food spectrum, consumption, and dynamics of commercial and non-commercial species was obtained and examined using Ecopath with an Ecosim software package.4.The bivalves A. purpuratus and T. dombeii represented the most abundant compartments in the studied subsystems. Of the carnivores, the snail T. chocolata was dominant, followed by the crabs Cancer spp. and the functional group of large epifauna.5.The two subsystems presented similar values of system throughput. The mean trophic level of their fisheries also reached similar magnitudes (2.0), showing that the harvests in each system concentrated on secondary producers. Likewise, both subsystems presented similar A/C ratios (29.9 and 30.3), suggesting that they were immature.6.The results obtained using mixed trophic impact (MTI) and Ecosim (increasing the fishing mortality Fi by four times) showed that only four species propagated the highest direct and indirect effects. Coincidentally, these species are the most economically important and the changes produced by the scallop A. purpuratus are noteworthy.7.With regard to the system recovery time (SRT) estimates, only three species or functional groups presented the highest magnitudes, from highest to lowest: the sea star Luidia magallanica, the scallop A. purpuratus, and the crabs Cancer spp.8.The topological keystone indexes of Jordán and Libralato had divergent results. According to Jordán's index, the keystone species were L. magallanica, Cancer spp., and detritus; whereas Libralato's index showed phytoplankton to be the keystone species.9.Based on the results obtained, it is concluded that trophic mass balanced models and simulated management scenarios have considerable value for planning interventions and manipulations or for planning more sustainable management strategies in La Rinconada Marine Reserve. Copyright © 2009 John Wiley & Sons, Ltd.Mass balanced trophic models and dynamic simulations of two benthic ecological systems from La Rinconada Marine Reserve (Antofagasta Bay, SE Pacific) were constructed.The scallop Argopecten purpuratus is the most important benthic resource in La Rinconada Marine Reserve, followed by the carnivorous snail Thais chocolata, and the filter-feeder bivalves Tagelus dombeii and Transennella pannosa.Information on biomass, P/B ratios, catches, food spectrum, consumption, and dynamics of commercial and non-commercial species was obtained and examined using Ecopath with an Ecosim software package.The bivalves A. purpuratus and T. dombeii represented the most abundant compartments in the studied subsystems. Of the carnivores, the snail T. chocolata was dominant, followed by the crabs Cancer spp. and the functional group of large epifauna.The two subsystems presented similar values of system throughput. The mean trophic level of their fisheries also reached similar magnitudes (2.0), showing that the harvests in each system concentrated on secondary producers. Likewise, both subsystems presented similar A/C ratios (29.9 and 30.3), suggesting that they were immature.The results obtained using mixed trophic impact (MTI) and Ecosim (increasing the fishing mortality Fi by four times) showed that only four species propagated the highest direct and indirect effects. Coincidentally, these species are the most economically important and the changes produced by the scallop A. purpuratus are noteworthy.With regard to the system recovery time (SRT) estimates, only three species or functional groups presented the highest magnitudes, from highest to lowest: the sea star Luidia magallanica, the scallop A. purpuratus, and the crabs Cancer spp.The topological keystone indexes of Jordán and Libralato had divergent results. According to Jordán's index, the keystone species were L. magallanica, Cancer spp., and detritus; whereas Libralato's index showed phytoplankton to be the keystone species.Based on the results obtained, it is concluded that trophic mass balanced models and simulated management scenarios have considerable value for planning interventions and manipulations or for planning more sustainable management strategies in La Rinconada Marine Reserve. Copyright © 2009 John Wiley & Sons, Ltd.