Study on the effects of temperature elevation on nutritive value of the edible seaweed ulva fasciata

The edible green seaweed Ulva fasciata which is abundant in Tanzania, is highly nutritious and can therefore help to curb severe malnutrition currently reported in the country. This study aimed to investigate the effect of rising temperature on the nutritive value of Ulva fasciata. Samples for the study were collected at the Oysterbay shoreline in Dar es Salaam and grown in a growth chamber at the University of Dar es Salaam. Growth rate and selected nutrients (proteins, vitamin A, carbohydrates, iron, phosphorus, calcium and potassium) were determined using standard analytical methods. Data analysis was done using a computer software program, Paleontological statistics (PAST) version 1.27, 1999-2012 version package. The results show that temperature elevation causes a decline in growth rate of U. fasciata (-0.94 ± 0.2% growth rate per day at 32-33°C). Furthermore, its protein content declined sharply from 19.8% dry weight to only 5.8% dry weight when temperature increased from the range of 28-29°C to the range of 32-33°C. ß-carotene content began to decline at a range of 30-31°Cwith lowest accumulation of 0.055% (wet weight) at 32-33°C. Carbohydrates content decline was progressive and was lowest (6.5% dry weight) at the range of 32-33°C. With the exception of Phosphorus which increased progressively with temperatures rise, other mineral nutrients of Iron, Calcium and Potassium began to decline at temperature ranges of 28-29°C, 30-31°C and 32-33°C respectively. The results indicate that the ongoing global warming will decrease the nutritive value of Ulva fasciata.