Lack of seasonality on macrobenthic assemblages from a shallow sublittoral sandy mud bottom (Ría de Muros, NW Iberian Peninsula)

Abstract One of the bottlenecks to managing ecosystems in sublittoral sediments is the absence of knowledge about their temporal variability that hampers the discrimination between natural and anthropogenic changes. This study investigated how the structure of macrobenthic assemblages and environmental factors in shallow muddy sediments varied according to season. Results showed no evidence of seasonal variability and a low diversity of macrobenthos due to the dominancy of the tube-building annelid Spiochaetopterus costarum. Most of them were burrowers/infauna, which construct burrows in the sediment and can have deep effects on the nearby environment because of bioturbation and bioengineering activities. The main environmental variables responsible for macrobenthic patterns were identified to provide models of abundance, diversity and multivariate structure of assemblages. However, models indicated that most of the variation in macrobenthos remained unexplained by the environmental variables. This study establishes baseline data useful for future monitoring programs, indispensable to detect and ameliorate changes associated with human activities and to design efficient management plans.