Seasonal Assessment of Hydrographic Variables and Phytoplankton Community in the Arabian Sea Waters of Kerala, Southwest Coast of India

Abstract

A B S T R A C TThe seasonal variation of the hydrographic variables and phytoplankton species in the Arabian Sea waters of the Kerala coast, Southern India was investigated during different seasons. The variables such as pH, temperature, salinity, turbidity and chlorophyll-a contents of water were found to be high during pre-monsoon season and the dissolved oxygen content was minimal. The concentration of nutrients viz., nitrate, phosphate, silicate varied independently. In the study a total of 53 species of phytoplankton were recorded. Their density was higher during the post-monsoon season than during other seasons and the diatoms were found to be the dominant species. The major phytoplankton in terms of frequency and abundance were the species namely, Biddulphia mobiliensis, Chaetoceros curvisetus, Licmophora abbreviata, Skeletonema costatum, Prorocentrum micans and Oscillatoria sp. They showed significant positive correlation with pH, temperature, salinity, nitrate, phosphate and chlorophyll-a contents, whereas turbidity, dissolved oxygen and silicate exhibited significant negative correlation. The Principal Component Analysis (PCA) developed two principal components with 84.74% of total variability in the water quality which separated pre-and post-monsoon periods from the monsoon season on axis I, and pre-monsoon and monsoon periods from post-monsoon on axis II. R E S U M OFoi investigada a variação sazonal das variáveis hidrográficas e das espécies de fitoplâncton nas águas do Mar Arábico da costa de Kerala, sul da India, em diferentes estações do ano. Variáveis como pH, temperatura, salinidade, turbidez e conteúdo de clorofila-a das águas mostraram-se altas durante a estação pré-monção enquanto o conteúdo de oxigênio dissolvido foi mínimo. A concentração de nutrientes, tais como nitrato, fosfato e silicato, variaram independentemente da época. Foi encontrado um total de 53 espécies, com picos de densidade durante a estação pós-monção, sendo a dominância exercida pelas diatomáceas. Em termos de frequência e abundância, as espécies mais importantes foram Biddulphia mobiliensis, Chaetoceros curvisetus, Licmophora abbreviata, Skeletonema costatum, Prorocentrum micans and Oscillatoria sp. Estas apresentaram correlação significativa positiva com pH, temperatura, salinidade, nitrato, fosfato e conteúdo de clorofila-a, enquanto que com turbidez, oxigênio dissolvido e silicato exibiram correlação negativa. A Análise de Componentes Principais (ACP) mostrou que os dois primeiros eixos contêm 84,74% da variação na qualidade das águas. O eixo I separou os períodos de pré-e pós-monção do período de monção, enquanto o eixo II separou os períodos de pré-monção e monção do período de pós-monção.

Reproductive traits in dolphinfish Coryphaena hippurus Linnaeus, 1758 along the coastal waters of Karnataka, south-eastern Arabian Sea

“…The peak spawning period observed during the monsoon season coincided well with the slight reduction in water temperature and salinity with the peak monsoon showers in the study area. The peak spawning activity observed during the monsoon period (August-September) in the present study could be linked with the reduction in temperature from a peak water temperature of pre-monsoon summer months in the tropical Arabian Sea, south-west coast of India (Sushanth and Rajashekhar, 2014). In contrast, increased spawning activity was reported in female C. hippurus from southern Gulf of California with the rise in temperature from 25 to 30°C (Zuniga-Flores et al, 2011).…”

Structure of microphytoplankton community and environmental variables in a macrotidal estuarine complex, São Marcos Bay, Maranhão - Brazil

“…Turbidity of water is usually caused by the presence of suspended matter (organic and inorganic matter) in water column that may decrease the light intensity and affect the phytoplankton development. Nevertheless, the elevated turbidity associated with high nutrient loading may enhance the growth of phytoplankton in high hydrodynamic systems (Rai and Rajashekhar, 2014).…”

Distribution and Diversity of Gelatinous Zooplankton in the South Eastern Arabian Sea, Kanyakumari to off Kollam

“…In the present study, AT and DO were inversely proportional and the relationship was found to be signifi cant (table 4). Th is is well explained by the signifi cant negative correlation of dissolved oxygen with salinity and temperature by Rai & Rajashekhar (2014) from the Arabian Sea waters of Kerala, south-west coast of India.…”