scholarly journals Peer Review #1 of "The density and biomass of mesozooplankton and ichthyoplankton in the Negro and the Amazon Rivers during the rainy season: the ecological importance of the confluence boundary (v0.2)"

2017 ◽  
Keyword(s):  
Peer Review ◽  
Rainy Season ◽  
Ecological Importance ◽  
Density And Biomass

scholarly journals The density and biomass of mesozooplankton and ichthyoplankton in the Negro and the Amazon Rivers during the rainy season: the ecological importance of the confluence boundary

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3308 ◽  
Author(s):  
Ryota Nakajima ◽  
Elvis V. Rimachi ◽  
Edinaldo N. Santos-Silva ◽  
Laura S.F. Calixto ◽  
Rosseval G. Leite ◽  
...  
Keyword(s):  
Rainy Season ◽  
Fish Larvae ◽  
Amazon River ◽  
Black And White ◽  
Black Water ◽  
Negro River ◽  
Feeding Habitat ◽  
White Water ◽  
Ecological Importance ◽  
Density And Biomass

The boundary zone between two different hydrological regimes is often a biologically enriched environment with distinct planktonic communities. In the center of the Amazon River basin, muddy white water of the Amazon River meets with black water of the Negro River, creating a conspicuous visible boundary spanning over 10 km along the Amazon River. Here, we tested the hypothesis that the confluence boundary between the white and black water rivers concentrates prey and is used as a feeding habitat for consumers by investigating the density, biomass and distribution of mesozooplankton and ichthyoplankton communities across the two rivers during the rainy season. Our results show that mean mesozooplankton density (2,730 inds. m−3) and biomass (4.8 mg m−3) were higher in the black-water river compared to the white-water river (959 inds. m−3; 2.4 mg m−3); however an exceptionally high mesozooplankton density was not observed in the confluence boundary. Nonetheless we found the highest density of ichthyoplankton in the confluence boundary (9.7 inds. m−3), being up to 9-fold higher than in adjacent rivers. The confluence between white and black waters is sandwiched by both environments with low (white water) and high (black water) zooplankton concentrations and by both environments with low (white water) and high (black water) predation pressures for fish larvae, and may function as a boundary layer that offers benefits of both high prey concentrations and low predation risk. This forms a plausible explanation for the high density of ichthyoplankton in the confluence zone of black and white water rivers.

scholarly journals Soil bulk density and biomass partitioning of Brachiaria decumbens in a silvopastoral system

2010 ◽  
Vol 67 (5) ◽  
pp. 598-603 ◽  
Author(s):  
Domingos Sávio Campos Paciullo ◽  
Carlos Renato Tavares de Castro ◽  
Carlos Augusto de Miranda Gomide ◽  
Priscila Beligoli Fernandes ◽  
Wadson Sebastião Duarte da Rocha ◽  
...  
Keyword(s):  
Bulk Density ◽  
Rainy Season ◽  
Block Design ◽  
Eucalyptus Grandis ◽  
Acacia Mangium ◽  
Soil Bulk Density ◽  
Tree Canopy ◽  
Brachiaria Decumbens ◽  
Allocation Pattern ◽  
Density And Biomass

Shade in silvopastoral systems improves the thermal comfort of animals, but it may also affect the pasture productivity and can contribute to soil compaction in the shaded areas due to the increase in the number of animals looking for comfort. The effect of grazing at various distances from tree rows (under the tree canopy, at 6 and at 12 m away from the trees) on the soil bulk density and on the aerial and root biomass of Brachiaria decumbens was evaluated in both the dry and the rainy seasons. The study was carried out on an Orthic Ferralsol in a randomized block design with two replications. Tree rows were composed of Eucalyptus grandis and Acacia mangium species, and the paddocks were submitted to a rotational stocking management, using Holstein (Bos taurus) × Zebu (Bos indicus) heifers. The shade intensity in the pasture decreased with an increasing distance from the tree row. Soil bulk density did not vary with the distance from the tree row, but varied seasonally, being greater in the rainy season (1.47 g cm-3) than in the dry season (1.28 g cm-3). Green forage and root mass, expressed as dry matter, were lower under the tree canopy and were greater in the rainy season. There were decreases of 22.3 and 41.4% in the aerial and root biomasses, respectively, in the tree rows. The greatest shoot/root ratio for B. decumbens under moderate and intensive shading indicates a modification in the forage biomass allocation pattern that favours the aerial development in detriment of the root system.

Fish use of stage-specific fluvial habitats as refuge patches during a flood in a low-gradient Illinois stream

2005 ◽  
Vol 62 (7) ◽  
pp. 1540-1552 ◽  
Author(s):  
John S Schwartz ◽  
Edwin E Herricks
Keyword(s):  
Fish Habitat ◽  
Three Dimensional ◽  
Fish Density ◽  
Low Velocity ◽  
Habitat Classification ◽  
Point Bars ◽  
Ecological Importance ◽  
The One ◽  
Density And Biomass ◽  
Flow Stage

A stage-specific habitat classification scheme was developed emphasizing the ecological importance of habitat space as flow refugia for fish. Habitat units were based on planform and channel morphology and the resulting three-dimensional hydraulic patterns that form during floods. Fish were sampled in specific habitat patches using prepositioned areal electrofishing devices at two high-flow stages, near bankfull flow and one-half bankfull flow, during a flood. Fish were also sampled at baseflow immediately following the flood to compare changes in habitat use related to flow stage. During the bankfull stage, fish were found to use floodplain habitat units identified as vegetated point bars and concave-bank benches. During the one-half bank-full stage, fish density and biomass were greater in low-velocity habitat units identified as deflection eddies and expansion eddies than in the high-velocity habitat unit identified as the channel thalweg. Once flow returned to baseflow, fish density and biomass were greater in the main channel habitat units (pools, riffles, and glides) than in lateral habitat units identified as submerged point bars and lateral backwaters. This study provided a framework to quantify flow refugia in low-gradient streams, which is especially important in the restoration of anthropogenically disturbed watersheds that have lost habitat connectivity.

scholarly journals Factores ambientales que influyen en la ictiofauna de la laguna La Mancha, sitio Ramsar, Golfo de México

2017 ◽  
Vol 66 (1) ◽  
pp. 246 ◽  
Author(s):  
Silvia Díaz ◽  
Arturo Aguirre-León ◽  
Erika Mendoza-Sánchez ◽  
Ana Laura Lara-Domínguez
Keyword(s):  
Rainy Season ◽  
Fish Community ◽  
Life Cycles ◽  
Spatial And Temporal Variation ◽  
Fish Diversity ◽  
Average Weight ◽  
Importance Value Index ◽  
Coastal System ◽  
La Mancha ◽  
Density And Biomass

La Mancha lagoon in the Gulf of Mexico, is a coastal system with Ramsar category because of its high biodiversity, many species of fish depend on it to complete their life cycles. In this study we analyzed the spatial and temporal variation of fish diversity, abundance and associations, and its relationship with physicochemical factors. Between April 2005 and January 2008, 95 daytime samplings were carried out at seven sites, where water characteristics and the composition of fish community were recorded. The system presented spatial-temporal variations of the physicochemical parameters, defining contrasting environments according to the local gradients. A total of 5 974 fish individuals, belonging to 50 species, 39 genera and 25 families were collected; four species were new records for the system. The diversity and richness of species were high in the brackish environment and low in freshwaters areas. In September (rainy season) and November (“nortes” season), diversity (H' = 1.52) and richness (D = 1.99) were highest. Fish abundance was greater towards the mouth connecting with the sea. The density and biomass (1.17 ind/m2, 4.33 g/m2) was higher in April (dry season) and the average weight (30.82 g/ind) in July (rainy season). The Importance Value Index (IVI) defined four dominant species representing 75 % of the numerical abundance and 46 % of the total catch in weight. The Canonical Correspondence Analysis (CCA) showed that the fish-habitat relationship was explained in 57 % of the total variance for the first two axes, where the variations in temperature, salinity, dissolved oxygen and depth were the environmental factors that determined the composition, distribution, community components and trophic categories of the fish community. This study provides information on the relationship between the environment and the structure of the fish community in La Mancha, and represents a basis for ecological monitoring to increase the knowledge needed about the ecosystem and fish populations, in order to boost management strategies for the fishery resources conservation in Veracruz.

scholarly journals Halophila baillonis Ascherson: first population dynamics data for the Southern Hemisphere

2015 ◽  
Vol 87 (2) ◽  
pp. 861-865 ◽  
Author(s):  
Karine M. Magalhães ◽  
João C.G. Borges ◽  
Maria E. Pitanga
Keyword(s):  
Population Dynamics ◽  
Southern Hemisphere ◽  
Aboveground Biomass ◽  
Protected Area ◽  
Rainy Season ◽  
Population Data ◽  
Shoot Density ◽  
Brazilian Coast ◽  
Oriented Parallel ◽  
Density And Biomass

The present paper presents the first population data for the Southern Hemisphere of the rare seagrass Halophila baillonis. The population studied is located in a calm, reef-protected area at depths ≤ 5 m, covering 12,000 m2 (400 m long by 30 m wide, oriented parallel to the coastline). The population generally demonstrated low shoot density and biomass during the rainy season, with significant differences between seasons, being found only for aboveground biomass. Despite the identification of this new population, the species continues to be considered rare along the Brazilian coast.

scholarly journals Population structure of Gobiidae in a tropical urban estuary

2020 ◽  
Vol 5 (4) ◽  
pp. 381-390
Author(s):  
André Luiz Ramos Holanda de Andrade ◽  
Susmara Silva Campos ◽  
Simone Ferreira Teixeira
Keyword(s):  
Population Structure ◽  
Rainy Season ◽  
Abundant Species ◽  
Northeastern Brazil ◽  
Sampling Station ◽  
Length Relationship ◽  
Representative Species ◽  
Significant Difference ◽  
Density And Biomass ◽  
Relationship Of

As spatiotemporal variations in estuaries affect the population structure of species, the study aimed to analyze the distribution of species of the family Gobiidae in the Capibaribe River's estuary city of Recife (northeastern Brazil). Sampling was performed bi-monthly from February 2009 to December 2012 at two sampling stations. The weight-length relationship of the species was determined using potential regression analysis. Density and biomass values were determined for each species per sampling station and season. The Mann-Whitney test was used to compare spatial and seasonal differences in abundance. A non-metric multidimensional scaling ordination was used to assess changes in species composition. Seven hundred eighty-eight individuals were caught. The most representative species of Gobiidae was Ctenogobius boleosoma, followed by Evorthodus lyricus and Gobionellus oceanicus. The relationship between total weight (TW) and standard length (SL) was potential and significant for both C. boleosoma (TW = 0.04SL2.1815) and E. lyricus (TW = 0.0272SL2.795), and both exhibited negative allometric growth. The analysis of the main species' spatial variation demonstrated a significant difference in the number of individuals for C. boleosoma (U = 528; p = 0.000005) and E. lyricus (U = 312; p = 0.000000). No significant difference in abundance was found between the dry and rainy season for either C. boleosoma (U = 1052.2; p = 0.4659) or E. lyricus (U = 1054; p = 0.4726). The two most abundant species have similar habits and customarily inhabit stressful environments. Ctenogobius boleosoma and E. lyricus are residents of the Capibaribe River's estuary, and both move to regions near the outfall of the river in the rainy season.

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