Catastrophes such as tsunamis and earthquakes do affect the flora and fauna around any given area temporarily, interrupting and unbalancing the food chain. Fortunately though nature is very good at balancing such things. Larger mammals and trees would take longer to return while smaller, faster growing plants and animals would return to the area much quicker.
After a tsunami you can think of the land as a blank slate. Those that reproduce the quickest and have the food to (insects) would see a large population boom. Others would follow as their food supply increased but all animals and plants would be in a rush to fill the niche left over by the tsunami wiping much of the established ecosystem out. The increase in their populations would be dependent on what they were.
Termites would do really well after a tsunami because of all the wet wood. Therefore birds would do really well because of all the termites and so on and so forth until all the niche’s were filled and the food chain eventually reached its “normal” equilibrium. A tsunami area that once had several large species of mammals might not have large mammals in that food chain for sometime until the lower part of the chain was established enough to maintain a food chain that would include large mammals.