Frontiers in Marine Science (Jun 2014)
A larval dispersion study using lagrangian simulation of particles
Abstract
The continuous displacement of water allows stabilize the temperature and also distributes nutrients and plankton in the ocean and seas permitting the development of organisms and the transfers of larvae from the spawning areas to the habitat where adult fishes can be found. The area of study covers The North Atlantic Ocean so the principal aim of the study is analyze if released particles at the Florida Strait could cross the North Atlantic Ocean and reach the European shelf. To test this, it has simulated Lagrangian trajectories for different numbers of particles or "larvae" with a passive behavior (fixing at a depth of dispersion). It has analyzed the dispersion of those particles by using the data of the components U, V and W from the speed of currents provided by the database SODA which uses an ocean model based on Geophysical Fluid Dynamics Laboratory MOM2 and data profiles from World Ocean Atlas-94 and from Geosat, ERS-1 and TOPEX/Poseidon satellites. Considering the dispersive nature of the ocean, the simulations were performed by releasing many particles (typically of the order of several thousand) and it was also necessary to perform an interpolation process in time and space so that the position of the particles could evolve. The simulations have been run with 5,000 particles and it has been considered a biological parameter (planktonic larval duration, PLD) that represents the length of larval life. At this study it has been used PLD for a specific starfish larva (Sclerasterias tanneri larvae) that can be found at the Gulf of Mexico at different locations. Particles were released in October at the most oceanward location of the Gulf of Mexico close to the Florida Strait where Sclerasterias tanneri larvae can be found. Those particles have been tracked for 660 days (660 days is the PLD of Sclerasterias tanneri larvae) recording their position every 15 days. That it has done for a period of more than 100 years (1901-2010). The period (1901-2010) let it study the possibility of a significant trend of the dispersion of particles since the twentieth century. To do this it has analyzed the number of particles that cross a finishing line (340 ⁰E) close to European shelf and the statistical analysis showed an increase at the number of particles exceeding 340 ⁰E. To reinforce that result it has clustered the final position of particles. It has also checked if the position of particles had a trend in their displacement. The results showed that particles are moving northeastward.
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