Long Term Ecological Research (LTER) in the Marine Coastal Environment: Basic Concepts and Keystones from the Plankton Communities.

Long-Term Ecological Research (LTER), which focuses on multidecadal observations, provides the correct approach and temporal context needed to avoid misjudgements in our attempts to understand and predict changes in marine ecosystems and to manage them. The LTER approach is particularly important when trend detection is a central issue, as in global change, and it is also critical for testing ecological theories on community dynamics, variability and resilience, enhancing our capacity of forecasting and of managing resources. Coastal marine ecosystems is among the most ecologically and socio-economically vital ecosystems in the planet; they are intrinsically highly variable, as a consequence of their connectivity to both land and open sea. Within these systems plankton is a primary driver of chemical and biological dynamics, directly affecting water quality, biogeochemical cycling and food supply to consumers. In marine costal ecosystems many regulatory processes fluctuate over multiple time scales and human disturbance is intense, making it a challenge the individuation of plankton "patterns". The study of coastal plankton communities, with a LTER perspective and with an across-system comparisons, appears crucial, in order to identify common patterns of variability and how they change with scales. In this paper we review the contribution to these issues coming from the Italian marine LTER sites, with emphasis on the researches carried out in the Northern Adriatic Sea.