Hydrographical Conditions

Hydrographical conditions are characterized by the physical parameters of seawater: temperature, salinity, depth, currents, waves, turbulence, turbidity (related to the load of suspended particulate matter). They play a crucial role in the dynamics of marine ecosystems and can be altered by human activities, especially in coastal areas. The physical parameters of seawater are essential because they structure the water masses and determine the various habitats that provide the environmental conditions required for marine life. These conditions influence the production and the growth of plankton and fish species. The dispersion and dwelling of larvae for many benthic and pelagic species depend on hydrographical factors. They also play an important role for the exchanges between the sea and the atmosphere and between the various layers of water. For instance, the weakening of the surface mixing process can induce a poor oxygenation of the seawater and sometimes lead to anoxic situations and a sudden mortality of some species. Hydrographical factors also control some features of the seafloor (for instance muddy seabeds require weak currents). Changes in the physical parameters of seawater can then have an impact on the spawning, breeding and feeding areas of marine organisms .