Changes in survival and growth in response to different combinations of turbidity and duration in eelgrass Zostera marina plants

Increased water turbidity is considered a primary cause of the loss of seagrass meadows. This paper first quantified the interactive influence of different combinations of turbidity and duration on the responses of Zostera marina plants in terms of survivorship, morphology and growth. The recovery potential of Z. marina plants, as well as the degrees of potential correlations between key factors induced by the increased turbidity and the survival and growth variables, were assessed. The LT50 (lethal time that caused an increase in mortality to 50% of that of the control) and EC50 (effect concentration, i.e., turbidity level that caused a decrease in growth to 50% of that of the control) were calculated to reveal the quantitative relationship between turbidity and duration that resulted in limiting effects on the survival and growth of Z. marina plants. Z. marina plants were exposed to different combinations of water turbidity [4 (control), 50, 100, 200, 300 and 400 NTU] and duration (5, 10, 15 and 20 days), and then the plants were transferred to the control condition for over 30 days under laboratory conditions. The results showed that the recovery effort (the percentage of the survival of plants at the end of recovery to that of plants at the end of direct turbidity stress) of Z. marina exposed to different combinations of turbidity and duration was lower than 100%, indicating that short-term periods of increased water turbidity would lead to long-term effects on the survival of Z. marina plants. Water turbidity and duration displayed a significant interactive effect on the survival and growth of Z. marina plants. Regression analysis revealed that the relationship between water turbidity and duration that resulted in limiting effects on the survival and growth of Z. marina could be described as a strong inverse function. Spearman correlation analysis showed that the decrease in survival and growth of Z. marina plants was mostly caused by increased silt load in turbid waters, and subsequently by light reduction. This study will further develop our understanding of the degradation and disappearance of seagrass meadows induced by increased turbidity.

Automated summary

Increased water turbidity is a primary cause of seagrass meadows loss. This study quantified the interactive influence of different combinations of turbidity and duration on Zostera marina plants, revealing a strong inverse relationship between turbidity and duration that affects the survival and growth of the plants. The study indicates that short-term periods of increased water turbidity can have long-term effects on the survival of Z. marina plants.