Background:

There are few studies of the effect of Sargassum sp. drift on coastal ecosystems. One of the most obvious changes is the increase in turbidity, however it has been only a few studies of how this is affecting seagrass communities and what changes they can induce in them that can indicate their impact in the ecosystem.

Objectives:

Determine the relationship between the turbidity caused by the Sargassum drift and the morphological variation and cover percentage of Syringodium filiforme, at the reef lagoon of the area of El Castillo, Xcalak, Quintana Roo.

Methods:

Five consecutive 50 m transects were placed perpendicular to the coast. In each transect, 25 x 25 cm quadrants every 10 m were used to obtain cover and morphometric data. Percentage of transparency was estimated. Samples from quadrants, were identified and measured. Significant differences between transparency and plant longitude were tested through nonparametric ANOVA, Kruskal-Wallis test and a simple linear regression analysis used to determine a possible significant correlation between this two parameters.

Results:

At 40% transparency, monospecific meadows were found, as well as larger sizes (58.9 cm) of S. filiforme, while in the areas with greater transparency, specimens with shorter lengths and mixed with Thalassia testudinum were found. Analyzes show a negative direct relationship between turbidity and Syringodium length.

Conclusions:

The existence of a negative direct relationship between the atypical elongation of the canopy and the transparency, with monospecific meadows, show that, a change exist in the seagrass meadows of the reef lagoon. We consider also necessary to investigate other factors that could be also causing this variation.