Environmental drivers of meiofaunal natural variability, Egypt, Southeastern Mediterranean

Abstract

Sandy beaches are challenging ecosystems, in which biota experience extreme physical conditions. We sampled meiofauna in conjunction with environmental factors that are well-known to affect faunal associations to describe the ecological state of sandy beaches that experience natural and human-made disturbances. We applied a random stratified sampling design with monthly collections (1800 cores) at three beaches on the Alexandria, Egypt, coast during two sampling periods over 1 year from November to April and May to September. We used multivariate analyses to compare beaches for water quality, particle size, and meiofaunal assemblages. The environmental analysis explained 60% of the total variation of physical factors among beaches and grouped beaches that moderately sorted fine-grained sand and high water salinity vs. the beach with well-sorted, coarse-grain, and low salinity. Meiofaunal analyses revealed unexpected results. The abundance and temporal variation were low, and the explained proportion of natural variation by the putative environmental factors was small. The natural variation was an indicator of long-term beach ruin and oligotrophic conditions. Our results suggest that a large fraction of natural variation in beach meiofauna is stochastic or that other, non-measured, the natural forces (e.g., storm events) or human-made forces (e.g., tourism activities) are essential contributors to variation. Our best models indicate that meiofauna is more resilient to natural disturbances than to human-made stressors, and the higher the beach exposure to the synergetic effects of natural forces and anthropogenic stressors, the lower the ecological state is.