A Production Model forPosidonia oceanicaBased on Temperature

Abstract

The leaf growth and plant population dynamics of the Mediterranean seagrassPosidonia oceanicawere investigated in relation to relevant environmental factors, such as temperature and irradiance. Two stands, located at 5 and 22 m in a continuousP. oceanicabed off Lacco Ameno (Island of Ischia, Gulf of Naples), were studied over 1 year. The aims of the study were: (1) to investigate the influence of temperature on the spatial and temporal growth pattern ofP. oceanica, using anad hocsimulation model of the monthly plant production; and (2) to identify the most efficient descriptors of plant growth, and therefore to achieve a simple method by which shoot production could be estimated.Irradiance is low at 22 m in the Lacco Ameno meadow, with the minimum value lower than 80 μE m−2s−1in winter. Temperature also differentiates the two water bodies in summer. The two stands differ for their structure (e.g. leaf area index), for plant production, and for some phenological features (e.g. leaf width).The best biological descriptors of plant production were identified and an equation was derived to estimate plant growth; the equation is based on the growth of the leaf of Rank 2, which describes the growth pattern of the whole plant. Significant correlations between temperature and the production descriptors were found. A numerical model of yearly leaf growth was devised. The model was validated by predicting the growth pattern of several MediterraneanP. oceanicabeds and comparing with observed values. It was also applied to simulate plant growth for the Lacco Ameno bed in preceding years, at both 5 and 22 m depths.