Using multitable techniques for assessing the temporal variability of species–environment relationship in a copepod community from a temperate estuarine ecosystem

This study investigated copepod assemblages' distribution patterns and determined the main hydrological and physical factors structuring it at different temporal scales. Copepod and hydrographic surveys were conducted seasonally during a one-year period, at a fixed station in Mondego estuary. Hourly samples were collected, during a diel cycle from sub-surface and 1 m above the bottom, at spring tides. Temporal variability of copepod community was analyzed using the STATICO method. Seasonal variability of the environmental conditions, linked with periods of higher freshwater flow, were the main drivers responsible for copepod community structure observed. Seasonal changes related to environmental factors showed to be strongest in spring and in winter, which accounted with higher species density. Marine and estuarine copepods showed maximal abundance in spring and summer, while the period of higher river flow, coincidently with autumn and winter, imposed changes in the copepods composition, emphasizing the changes in saline zonation within the estuary due to regime of river discharge. STATICO also emphasized the effects of physical forcing at short-term temporal scales. The stable part of the species–environment relationships resulted from the combination of a salinity gradient linked to a fresh, brackish- and marine species gradient, which was dependent on tidal cycle. The STATICO method proved to be a valuable statistical tool to get a clear representation of temporal organization of the copepod assemblages.

Research highlights
► STATICO proved to be a powerful tool, integrating copepod dynamic and hydrodynamics.
► STATICO identified marine, brackish and freshwater species-affinity assemblages.
► Freshwater flow was the main driver responsible for copepod community structure.
► Winter and spring were important contributors for the biotic organization observed.
► Tides and diel cycles were important source of variation in copepod assemblages.