Georg Umgiesser

Assessing confinement in coastal lagoons

Measures of transport scale in aquatic systems can contribute to the formulation of definitions of indicators of the systems ecological properties. This paper addresses confinement, a specific transport scale proposed by biological scientists as a parameter that can capture and synthesize the principal properties that determine the spatial structure of biological communities in transitional environments. Currently, there is no direct experimental measure of confinement. In this study, a methodology based on the accumulation rate within a lagoon of a passive tracer of marine origin is proposed, the influences of different factors in the calculation of confinement are analyzed, and general recommendations are derived. In particular, we analyze the spatial and the temporal variability of confinement and its sensitivity to the seasonal variability of climatic forcing, the inputs from rivers and the parameterization of the tidal exchanges. The Lagoon of Venice is used as a case study.

Connectivity in Three European Coastal Lagoons

The temporal variation and the spatial structure of marine populations strongly depend on the early life stages of the individuals and on their interaction with the environment. The physical dispersion of propagules (eggs and larvae) is a fundamental aspect, conditioning the successful recruitment of juveniles in the adult population. Coastal transitional ecosystems such as lagoons plays a role of nursery for species with economic relevance, such as demersal fishes, mollusks and crustaceans. Those environments promote the recruitment of the early stages for several organisms because they act as area of retention for propagules and concentration for resources. We applied in three different European coastal lagoon a lagrangian particle tracking model coupled with a hydrodynamic model, and developed a method to evaluate the connectivity inside a lagoon and between a lagoon and the sea. Each particle represents a generic passive pelagic larva with a duration of one month. The average connectivity has been estimated after two years of simulation under realistic tide and wind forcings. Our results allow to characterize the lagoons behavior considering different spatial scales and to compare the dynamics of different systems. This study is a first step toward a better knowledge of the factors influencing the ecological role of coastal lagoons.