Population dynamics and reproductive strategy of Scolelepis goodbodyi (Polychaeta: Spionidae) in a subtropical atlantic beach

The population dynamics and reproductive strategy of the polychaete Scolelepis goodbodyi (Jones, 1962), were investigated between June 2009 and May 2010 at Manguinhos beach, southeastern, Brazil. A total of 9,242 individuals were collected. The density did not differ significantly from one month to another. The estimated values of the growth, recruitment, and mortality rates were studied using the width of the third setiger and the growth curves for the populations were adjusted by the Bhattacharya method (L'= 1.23, K = 1.2, mortality = 0.73). Two annual cohorts were identified in the period. Significant differences between males and females were observed in the population (x² = 71.6, p 0.01) and between sexually defined and sexually indeterminate individuals (x² = 158.4, p 0.01). Five stages of gonadal development were identified. The coexistence of recruits and mature individuals throughout the study period suggests that this population presented continuous reproduction.

Population dynamics and reproductive strategy of Scolelepis goodbodyi (Polychaeta: Spionidae) in a subtropical atlantic beach

The population dynamics and reproductive strategy of the polychaete Scolelepis goodbodyi (Jones, 1962), were investigated between June 2009 and May 2010 at Manguinhos beach, southeastern, Brazil. A total of 9,242 individuals were collected. The density did not differ significantly from one month to another. The estimated values of the growth, recruitment, and mortality rates were studied using the width of the third setiger and the growth curves for the populations were adjusted by the Bhattacharya method (L'= 1.23, K = 1.2, mortality = 0.73). Two annual cohorts were identified in the period. Significant differences between males and females were observed in the population (x² = 71.6, p 0.01) and between sexually defined and sexually indeterminate individuals (x² = 158.4, p 0.01). Five stages of gonadal development were identified. The coexistence of recruits and mature individuals throughout the study period suggests that this population presented continuous reproduction.

Population dynamics and reproductive strategy of Scolelepis goodbodyi (Polychaeta: Spionidae) in a subtropical atlantic beach

The population dynamics and reproductive strategy of the polychaete Scolelepis goodbodyi (Jones, 1962), were investigated between June 2009 and May 2010 at Manguinhos beach, southeastern, Brazil. A total of 9,242 individuals were collected. The density did not differ significantly from one month to another. The estimated values of the growth, recruitment, and mortality rates were studied using the width of the third setiger and the growth curves for the populations were adjusted by the Bhattacharya method (L'= 1.23, K = 1.2, mortality = 0.73). Two annual cohorts were identified in the period. Significant differences between males and females were observed in the population (x² = 71.6, p 0.01) and between sexually defined and sexually indeterminate individuals (x² = 158.4, p 0.01). Five stages of gonadal development were identified. The coexistence of recruits and mature individuals throughout the study period suggests that this population presented continuous reproduction.

Macrobenthic community structure in a Brazilian chocked lagoon system under environmental stress

Saquarema-Jaconé lagoonal system (SJLS) comprises a sequence of five interconnected shallow brackish lagoons with access to the sea by a single permanent tidal channel. It is a eutrophic system, receiving constant input of organic load from its urbanized catchments. The relationship between several environmental variables and the spatial-temporal distribution of the benthic macrofauna was assessed during four seasonal samplings (dry and wet periods of 2007-2009). Sediment replicates were sampled at seven sites for biological identification and analyzes of organic matter, carbonates, phytopigments, grain size and heavy metals. Salinity, dissolved oxygen and redox potential were measured in situ. SJLS was characterized by sandy bottoms with very reducing conditions. Redox potential significantly discriminated between the dry and wet periods and anoxic conditions were observed in the latter. No significant seasonal differences were observed in the macrofauna. A total of 37 taxa were identified, of which Capitella sp, oligochaetes and Laeonereis culveri (Webster, 1880) were the dominant, representing the early stage of community recovery following dystrophic crises. The faunistic pattern seems to be determined by complex combinations of silt+clay with salinity, organic matter and redox potential. On the other hand, the low concentrations of heavy metals found did not seem to influence the structure and distribution of the biota. SJLS is undergoing persistent environmental stress, dominated by first-order opportunistic species linked to organically enriched sediments.

Macrobenthic community structure in a Brazilian chocked lagoon system under environmental stress

Saquarema-Jaconé lagoonal system (SJLS) comprises a sequence of five interconnected shallow brackish lagoons with access to the sea by a single permanent tidal channel. It is a eutrophic system, receiving constant input of organic load from its urbanized catchments. The relationship between several environmental variables and the spatial-temporal distribution of the benthic macrofauna was assessed during four seasonal samplings (dry and wet periods of 2007-2009). Sediment replicates were sampled at seven sites for biological identification and analyzes of organic matter, carbonates, phytopigments, grain size and heavy metals. Salinity, dissolved oxygen and redox potential were measured in situ. SJLS was characterized by sandy bottoms with very reducing conditions. Redox potential significantly discriminated between the dry and wet periods and anoxic conditions were observed in the latter. No significant seasonal differences were observed in the macrofauna. A total of 37 taxa were identified, of which Capitella sp, oligochaetes and Laeonereis culveri (Webster, 1880) were the dominant, representing the early stage of community recovery following dystrophic crises. The faunistic pattern seems to be determined by complex combinations of silt+clay with salinity, organic matter and redox potential. On the other hand, the low concentrations of heavy metals found did not seem to influence the structure and distribution of the biota. SJLS is undergoing persistent environmental stress, dominated by first-order opportunistic species linked to organically enriched sediments.

Macrobenthic community structure in a Brazilian chocked lagoon system under environmental stress

Saquarema-Jaconé lagoonal system (SJLS) comprises a sequence of five interconnected shallow brackish lagoons with access to the sea by a single permanent tidal channel. It is a eutrophic system, receiving constant input of organic load from its urbanized catchments. The relationship between several environmental variables and the spatial-temporal distribution of the benthic macrofauna was assessed during four seasonal samplings (dry and wet periods of 2007-2009). Sediment replicates were sampled at seven sites for biological identification and analyzes of organic matter, carbonates, phytopigments, grain size and heavy metals. Salinity, dissolved oxygen and redox potential were measured in situ. SJLS was characterized by sandy bottoms with very reducing conditions. Redox potential significantly discriminated between the dry and wet periods and anoxic conditions were observed in the latter. No significant seasonal differences were observed in the macrofauna. A total of 37 taxa were identified, of which Capitella sp, oligochaetes and Laeonereis culveri (Webster, 1880) were the dominant, representing the early stage of community recovery following dystrophic crises. The faunistic pattern seems to be determined by complex combinations of silt+clay with salinity, organic matter and redox potential. On the other hand, the low concentrations of heavy metals found did not seem to influence the structure and distribution of the biota. SJLS is undergoing persistent environmental stress, dominated by first-order opportunistic species linked to organically enriched sediments.

Population structure and reproductive biology of Uca rapax (Decapoda: Ocypodidae) in a tropical coastal lagoon, southeast Brazil

A population of the fiddler crab Uca rapax (Smith, 1870) found in Itaipu Lagoon, southeast Brazil, was sampled monthly from July 2006 to June 2007 in order to study population and reproductive features. The sex ratio of the population was statistically different from the expected (1:1) in almost every month, with a predominance of males. The reproductive cycle and the recruitment of juveniles were continuous, with two peaks. The fecundity ranged from 1.110 to 13.189 eggs (4.984 ± 2.493.8), not differing statistically among seasons. In contrast, the relative fecundity (F') and the reproductive intensity index (RII) were highest in the summer. Female size at the onset of sexual maturity was estimated as 6.1 mm and egg diameter ranged from 0.20 to 0.28 mm. The anthropogenic impact on the environment of Itaipu Lagoon probably had adverse effects on the local U. rapax population, as inferred by its low fecundity rates, early maturation age and biased sex ratio.

Population structure and reproductive biology of Uca rapax (Decapoda: Ocypodidae) in a tropical coastal lagoon, southeast Brazil

A population of the fiddler crab Uca rapax (Smith, 1870) found in Itaipu Lagoon, southeast Brazil, was sampled monthly from July 2006 to June 2007 in order to study population and reproductive features. The sex ratio of the population was statistically different from the expected (1:1) in almost every month, with a predominance of males. The reproductive cycle and the recruitment of juveniles were continuous, with two peaks. The fecundity ranged from 1.110 to 13.189 eggs (4.984 ± 2.493.8), not differing statistically among seasons. In contrast, the relative fecundity (F') and the reproductive intensity index (RII) were highest in the summer. Female size at the onset of sexual maturity was estimated as 6.1 mm and egg diameter ranged from 0.20 to 0.28 mm. The anthropogenic impact on the environment of Itaipu Lagoon probably had adverse effects on the local U. rapax population, as inferred by its low fecundity rates, early maturation age and biased sex ratio.

Population structure and reproductive biology of Uca rapax (Decapoda: Ocypodidae) in a tropical coastal lagoon, southeast Brazil

A population of the fiddler crab Uca rapax (Smith, 1870) found in Itaipu Lagoon, southeast Brazil, was sampled monthly from July 2006 to June 2007 in order to study population and reproductive features. The sex ratio of the population was statistically different from the expected (1:1) in almost every month, with a predominance of males. The reproductive cycle and the recruitment of juveniles were continuous, with two peaks. The fecundity ranged from 1.110 to 13.189 eggs (4.984 ± 2.493.8), not differing statistically among seasons. In contrast, the relative fecundity (F') and the reproductive intensity index (RII) were highest in the summer. Female size at the onset of sexual maturity was estimated as 6.1 mm and egg diameter ranged from 0.20 to 0.28 mm. The anthropogenic impact on the environment of Itaipu Lagoon probably had adverse effects on the local U. rapax population, as inferred by its low fecundity rates, early maturation age and biased sex ratio.