Spatial and temporal variations of epiphytic Ostreopsis siamensis on Posidonia oceanica (L.) Delile leaves in Mahdia (Tunisia)
Year: 2012
Type: article
Abstract: In order to study the spatial and temporal variation in abundance of the potentially toxic species Ostreopsis siamensis epiphytic on the leaves of Posidonia oceanica, two dates of sampling were conducted in the region of Mahdia (Eastern Tunisia) in July 2008 and January 2009. Two sites within each of four stations were selected at depths of 3, 5, 8 and 12 m, P. oceanica shoots and seawater samples at two different levels of the water column (bottom and surface) were collected. Utermöhl sedimentation method was used to quantify the abundance of O. siamensis epiphyte on the leaves of P. oceanica and living in the water column. Our results showed that the abundance of this epiphytic species is lower than those found in other areas of Tunisia. Covariance analysis (ANCOVA) of abundance of epiphytic O. siamensis on the leaves of P. oceanica between time, station and site nested within station with depth as covariate showed that spatial differences of this abundance depended on the time of sampling and the highest value are recorded in July. Temperature and life cycle of the host plant seemed to be the important factors responsible for this temporal variation. Linear regression showed a significant relationship between the abundance of this species and Leaf Area Index of P. oceanica. We also found positive significant correlations between the abundance of epiphytic O. siamensis and its abundance in the water column (bottom and surface). These results could indicate a transfer of this species from P. oceanica leaves to the water column.
Source: Cahiers de biologie marine
Authors: MABROUK, Lotfi, HAMZA, Asma, MAHFOUDI, Mabrouka, BRADAI, Mohamed-Najmeddine
Language: English
Subfield: Oceanography
Field: Earth and Planetary Sciences
Domain: Physical Sciences
SDG: Life below water
Open Access status: bronze
OpenAlex ID: W2463220133