Background:

In the Gulf of Mexico, the Alvarado Lagoon System (ALS) stands out for its dimensions and fisheries. Rotifers are among the most abundant groups of zooplankton in these ecosystems. Information on its composition, diversity, and seasonal variation is scarce, despite its structural and functional importance.

Objective:

We determined the diversity, seasonal variation, and the influence of pH, transparency, salinity, and temperature in the rotifer community structure in the ALS.

Method:

We collected zooplankton samples and physicochemical parameters from September 2017 to May 2018 in four zones of the ALS along the salinity gradient. Zooplankton was separated into groups, and rotifers identified species level. Shannon-Weiner diversity index and effective diversity Hill numbers Q1 and Q2 were calculated by analyzing differences among seasons and zones. A cluster analysis was performed to determine the similarity in the biological composition between zones and seasons. Canonical correspondence analysis was performed with transformed data of physicochemical parameters and rotifer abundances.

Results:

Oligohaline behavior in the rainy season to mesohaline in the dry season and the influence of the rivers in all the ALS was observed. 24 rotifer species and four cladocerans were identified, all correspond to new records, being Brachionidae the most abundant. The highest diversity occurs during the rainy season in the south zone while the lowest in the dry season. Salinity and turbidity were related to the distribution of the Brachionidae species.

Conclusions:

Hydrological behavior and salinity variation gradient agree with records for ALS.