The ocean currents are a continuous, directed movement of water that flows in the earth’s ocean. It is a very powerful physical force in the ocean. These currents are generated through a number of forces acting upon the water that is the wind, Coriolis effect, breaking waves, temperature and salinity differences. Currents flow for great distances and its strength and direction is influenced by the number of factors including depth contours, shoreline configuration, and contacts with other currents. On their journey, the water masses transport both energy (in the form of heat) and matter (solids, dissolved substances and gases) around the globe for the survival of various marine creature and bordering on the ecosystem. The two parameters i.e. temperature and salinity have a particular effect on ocean body which helps in forming the water masses with identifiable physical characters. Water masses has a great impact on the coastal environment and marine life.
On the movement of ocean water, they create conveyor belt, which plays a decisive role in influencing the climate and ecosystem of the regions through which they flow. For example- Gulf Stream which makes northwest Europe much more temperate than any other region on the same latitude. The ocean’s conveyor belt is also known as thermohaline circulation. The adjective thermohaline derives from two-component i.e. thermo means temperature and haline means salinity. These two factors play a crucial role in determining the deep ocean currents (thermohaline circulation). The conveyor belt (which refers to deep density-driven ocean basin currents) have two significant current motion upwelling and downwelling and together they strongly influence the distribution and abundance of marine life and coastal environment.
Thus, ocean current and water masses have varied impact on the life of creature living under the ocean and environment of coastal regions. Their impact is also varied according to their location and movements. A glimpse of their impact on the coastal regions and marine life:
Impact of ocean currents on marine life-
(a) Ocean currents have many great impacts on marine life. In the ocean currents, not only plants and animals are moving but also heat and nutrients are distributed along the way. Many animals and plants drift in the ocean currents during one or more stages of their entire life. It is well known that plankton drifts with currents (plankton means wandering). Many Species drifts with currents to form new colonization.
(b) Currents play a huge role in marine productivity, through the process called upwelling and downwelling. Cold and warm currents are part of larger upwelling and downwelling system which provides nutrition, oxygen mixing from top to bottom layers. Sea life is concentrated in the sunlit waters near the surface, but most organic matter is far below, in deep waters and on the sea floor. The global conveyer belt takes oxygen-rich surface water and spread through the deep sea. When currents upwelled or flow up to the surface from beneath, they sweep vital nutrients back to where they’re needed most.
(c) Different marine species possess different ecosystem i.e. some used to live in euryhaline (able to tolerate a wide range of salinity) and some are stenohaline (marine organisms can only survive in the narrow range of salinity). Most freshwater organisms are stenohaline and will die in seawater. It is to be noted that the salinity and temperature are the gradients of the ocean’s conveyor belt (deep ocean currents) which greatly impact the marine organisms.
(d) Warmer water temperature has some negative effects on the coral reefs. Warmer water can result in coral bleaching. It means when the water is too warm, the coral will expel the algae living in their tissues causing the coral too completely white. For example- In 2005, the U.S. lost half of its coral reefs in the Caribbean in one year due to a massive bleaching event and in 2010, cold water temperatures in the Florida Keys caused a coral bleaching event that resulted in some coral death.
Ocean Currents impact on Coastal Environment-
(a) Ocean currents affect the coastline: Warm and cold ocean currents can affect the climate of coastal regions, but only when local winds blow in from the sea. Warm currents increase the air and bring higher temperatures over the land. Coldwater currents can lower air temperatures and can bring colder temperatures over land. For example- Southern California and Arizona have the same latitude. However, Arizona summers are extremely hot, while Southern California summers are generally quite mild.
(b) Ocean currents mix coastal environment with water at pelagic areas, which acts as a temperature equalizer, nutrients recycler.
(c) Sea ice freezing or melting- Ocean currents of different properties like warm and cold are responsible for the melting and freezing of ice. Warm currents prevent the formation of sea ice even though the region is close to poles. Warm Atlantic Drift keeps Norway coast open in winters also. The region of temperate climates will suffer from sea ice formation which affects coastal navigation leading to loss of economic activity.
(d) Intermixing of cold and warm water are well suited for the fishing. For Example- Cold Labrador with warm North Atlantic Drift at Grand Bank.
Impact of Water Masses on Marine life-
(a) Due to definite physical characteristics and they become immovable leading to stagnation and Hypoxic conditions like phenomena. Hypoxia or oxygen depletion is an environmental phenomenon where the concentration of dissolved oxygen in the water column decreases to a level that can no longer support marine species. As a result, the aquatic living organisms decreases from a particular ecosystem that is created by water masses.
(b) Warm water masses increase the growth of algae (Red Tides), thereby affecting the productivity of marine life whereas, the cold-water masses with nutrients helps in plankton growth which in turn increase the productivity of marine life.
(c) Stationary water masses have ocean stratification effect which has an overall effect on marine life and carbon concentration.
Impact of Water Masses on Coastal Environment-
(a) Water masses affect the local weather condition. The presence of warm water masses increases the temperature and humidity of bordering on regions. Even, the warm water masses near coasts have desertification effect due to dryness. For example- African west coast- Sahara Desert.
(b) Water masses can lead to the formation of cyclone in India in pre and post-monsoon times.
(c) Water masses can lead to sea and breeze and also regulates the sea and land temperature differences.
Hence, both ocean currents and water masses have a different and interconnected impact on marine life and the coastal environment.
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