Keywords: environmental monitoring, macroalgal biomass estimate, opportunistic macroalgae, Orbetello lagoon, remote sensing, macroalgal standing crops, shallow water, ultralight aircraft, macroalgal mats, macroalgal harvesting, Italy
Macroalgal standing crop estimate – fast method using ultralight aircraft
A simple and low-cost method for monitoring macroalgal standing crops in shallow water consists of flying over and photographing the areas in an ultralight aircraft to determine the surface area of macroalgal mats. In the proposed method, photos are analysed by AUTOCAD software and mat density is then estimated in the field. Using mat density and bottom surface covered by mats, a rough estimate of the Standing Crop (SC) can be computed. Total of all estimated SCs in a given period is the Total Macroalgal Standing Crop (TMSC). The method was developed to support macroalgal harvesting operations in Orbetello lagoon. SC and TMSC values were needed to decide places and times of macroalgal harvesting and to estimate the boat work required. Applied to ecological studies, this method called Fast Valuation Method (FVM) and is compared with a more time-consuming Accurate Valuation Method (AVM), which calls for extensive sampling and statistical processing. The t-test did not show significant differences between the results provided by the two methods. The results were more similar in winter, when macroalgal growth is slow and wind concentrates the mats. The results may diverge in summer when floating macroalgae are more evenly distributed, with FVM tending to underestimate TMSC. FVM is in any case of potential interest for monitoring studies.