Crescimento e distribuição de duas espécies de macrófitas aquáticas submersas em diferentes condições ambientais
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Data
2022-01-28
Autores
Taveira, Renan
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Universidade Estadual Paulista (Unesp)
Resumo
A distribuição de espécies vegetais é um tema frequente nos estudos ecológicos de comunidades. Podemos relacionar os padrões de distribuição com diversas variáveis bióticas e abióticas. Em ambientes costeiros do Estado de São Paulo, que possui clima e regime de chuva homogêneos, características geológicas e geomorfológicas distintas, além de diversos tipos de uso e ocupação do solo, encontramos uma grande riqueza de espécies vegetais que respondem a estas diferentes características, inclusive de espécies de macrófitas aquáticas. Neste estudo verificamos a porcentagem de ocorrência de Egeria densa Planch. e Cabomba furcata Schultz. e Schultz., espécies de macrófitas aquáticas submersas, em um trecho do rio Branco, na bacia do rio Itanhaém, litoral sul do Estado de São Paulo, e verificamos como a pluviosidade pode influenciar temporalmente e espacialmente na ocorrência delas neste trecho. Também analisamos como diferentes níveis de radiação fotossinteticamente ativa (Photosynthetically Active Radiation – PAR) podem influenciar no crescimento e desenvolvimento destas duas espécies. Escolhemos o rio Branco para coletar nossos dados pois verificamos variações constantes na distribuição destas espécies neste trecho do rio ao longo do tempo. A coleta dos dados de presença de bancos das duas espécies foi realizada entre os anos de 2012 e 2020 e, em seguida, calculamos a porcentagem de ocorrência de cada uma. Coletamos os dados de pluviosidade acumulada de dias anteriores a cada coleta pela estação pluviométrica do Departamento de Águas e Energia Elétrica de São Paulo (DAEE). Plotamos os dados de ocorrência e pluviosidade em gráficos boxplot para verificarmos a existência destes padrões temporais e espaciais. Em seguida verificamos a significância de cada variável testada e a estimativa que cada uma das variáveis representa através de Análises de Variância (ANOVA fatorial) e Modelos Lineares Generalizados (Generalized Linear Models – GLM). Para verificar o efeito da PAR no crescimento de E. densa e C. furcata, montamos um experimento aleatorizado, com quatro tratamentos de diferentes níveis de luminosidade e dez réplicas de indivíduos de E. densa e C. furcata cada. O experimento teve duração de 30 dias e medimos o comprimento dos rametes a cada dois dias. Calculamos então a biomassa e o ganho de biomassa através de uma regressão linear simples. Aos dados de biomassa, ajustamos as retas de crescimento e obtivemos os coeficientes de inclinação das retas, e aos dados de ganho de biomassa aplicamos uma ANOVA unidirecional para verificar diferenças significativas entre os tratamentos. Nossos resultados mostraram que E. densa e C. furcata tem maior chance de ocorrência no subtrecho superior do que no inferior, apresentando também uma variação temporal, porém sem padrão sazonal e sem influência da pluviosidade nesta distribuição. E. densa apresentou maior crescimento no tratamento com maior luminosidade, enquanto C. furcata se desenvolveu mais no tratamento com menor luminosidade. Nossos resultados apontam que as duas espécies têm diferentes preferências quanto a disponibilidade de luz, que pode influenciar na ocorrência destas espécies nos ambientes aquáticos, porém mais estudos são necessários para tentar entender quais variáveis influenciam na distribuição destas espécies na bacia do rio Itanhaém.
The distribution of plant species is a recurrent subject in ecological studies of communities. We can relate the distribution patterns with several biotic and abiotic variables. In coastal environments in the State of São Paulo, which has homogeneous climate and rainfall, distinct geological and geomorphological characteristics, different types of land use and occupation, we find a great richness of plant species that respond to these different characteristics, including aquatic macrophyte species. In this study we verified the occurrence of Egeria densa Planch. and Cabomba furcata Schultz. and Schultz., two species of submerged aquatic macrophytes, in a stretch of the Branco river, in the Itanhaém river basin, south coast of the State of São Paulo, and we verified how the rainfall can influence the temporal and spatial occurrence of both in this stretch. We also sought to verify how different levels of photosynthetically active radiation (PAR) can influence the growth and development of these two species. The sampling was carried out between the years of 2012 and 2020, in a stretch of the Branco river, as we verified constant variations in the distribution of these species in this over a period of time. Therefore, we calculated the percentage of occurrence of each species in this stretch. Additionally, we gathered data for accumulated rainfall from days prior to each sample in the São Paulo Departamento de Águas e Energia Elétrica (DAEE) rainfall database. We plotted the occurrence and rainfall data into boxplots to verify the existence of temporal and spatial patterns. We then verified the significance of each variable and calculated the estimative that each significant variable represents through an Analysis of Variance (Two-way ANOVA) and Generalized Linear Models (GLM), respectively. To verify the effect of PAR on the growth of E. densa and C. furcata, we set up a randomized experiment, with four treatments of different light levels each and ten replicates of individuals of E. densa and C. furcata. The experiment lasted for 30 days and we measured the length of the ramets each two days. We then calculated the biomass and the gain of biomass using a simple linear regression. To the biomass data, we fitted the growth lines and obtained the slope coefficients of the lines. To verify significant differences between treatments, we ran a one-way ANOVA. Our results showed that E. densa and C. furcata are more likely to occur in the upper subsection than in the lower one, also presenting a temporal variation, however with no apparent seasonal pattern and with no influence of the rainfall in the occurrence. E. densa showed greater development in the treatment with more light availability, while C. furcata had a greater development in the treatment with less light availability. Our results showed that both species have different preferences regarding the light availability, which can influence the occurrence of these species in aquatic environments, but more studies are needed to try to understand which variables influence the distribution of these species in the Itanhaém river basin.
The distribution of plant species is a recurrent subject in ecological studies of communities. We can relate the distribution patterns with several biotic and abiotic variables. In coastal environments in the State of São Paulo, which has homogeneous climate and rainfall, distinct geological and geomorphological characteristics, different types of land use and occupation, we find a great richness of plant species that respond to these different characteristics, including aquatic macrophyte species. In this study we verified the occurrence of Egeria densa Planch. and Cabomba furcata Schultz. and Schultz., two species of submerged aquatic macrophytes, in a stretch of the Branco river, in the Itanhaém river basin, south coast of the State of São Paulo, and we verified how the rainfall can influence the temporal and spatial occurrence of both in this stretch. We also sought to verify how different levels of photosynthetically active radiation (PAR) can influence the growth and development of these two species. The sampling was carried out between the years of 2012 and 2020, in a stretch of the Branco river, as we verified constant variations in the distribution of these species in this over a period of time. Therefore, we calculated the percentage of occurrence of each species in this stretch. Additionally, we gathered data for accumulated rainfall from days prior to each sample in the São Paulo Departamento de Águas e Energia Elétrica (DAEE) rainfall database. We plotted the occurrence and rainfall data into boxplots to verify the existence of temporal and spatial patterns. We then verified the significance of each variable and calculated the estimative that each significant variable represents through an Analysis of Variance (Two-way ANOVA) and Generalized Linear Models (GLM), respectively. To verify the effect of PAR on the growth of E. densa and C. furcata, we set up a randomized experiment, with four treatments of different light levels each and ten replicates of individuals of E. densa and C. furcata. The experiment lasted for 30 days and we measured the length of the ramets each two days. We then calculated the biomass and the gain of biomass using a simple linear regression. To the biomass data, we fitted the growth lines and obtained the slope coefficients of the lines. To verify significant differences between treatments, we ran a one-way ANOVA. Our results showed that E. densa and C. furcata are more likely to occur in the upper subsection than in the lower one, also presenting a temporal variation, however with no apparent seasonal pattern and with no influence of the rainfall in the occurrence. E. densa showed greater development in the treatment with more light availability, while C. furcata had a greater development in the treatment with less light availability. Our results showed that both species have different preferences regarding the light availability, which can influence the occurrence of these species in aquatic environments, but more studies are needed to try to understand which variables influence the distribution of these species in the Itanhaém river basin.
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Palavras-chave
Porcentagem de ocorrência, Egeria densa, Cabomba furcata, Variáveis abióticas, Biomassa, GLM, Percentage of occurrence, Abiotic variables, Biomass