Opportunistic, short-lived organisms live in these ecosystems, where conditions change rapidly as lagoon entrances to the open ocean open or close. Periodic opening and closure influences dynamic gradients in salinity, nutrients, temperature, and water level. Algae, invertebrates like shrimps, and small fish rely on nutrients from land and, when open, the sea. Timing of opening or closing depends on transport of sand and mud by currents or freshwater inflow, or on anthropogenic processes.