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Sep 25

Human Impacts on Underwater Ecosystems

The oceans, lakes, and rivers of this planet form a vast network of aquatic environments, many of which have yet to be explored, remaining more mysterious to researchers than even the moon. Most of the world’s major cities are found along coastlines, and our daily activities have a profound impact on aquatic environments. But all of Earth’s environments are interdependent of each other. What negatively impacts the underwater world has repercussions for the land, and ultimately our own survival. The following are but a few examples of how human activities threaten the underwater environments and the consequences to us.



The current methods of commercial fishing are unsustainable; since 1989, there has been a sharp drop in fish populations world wide. A scientific study conducted in 2003 estimated that the populations of larger ocean fish species is only 10 percent of what it was in the mid-20th century. Another study conducted in 2006 estimates that the world’s fisheries will no longer be in operation by the year 2048.

Besides commercial species, non-targeted species often become the victim of fishing technologies. Seabirds, dolphins, sea turtles, and sharks are but a few of the species that are frequently killed by getting caught on long lines or tangled in nets.



Pollution from human activity eventually makes its way to the oceans. Plastics are a major problem, constituting 60 percent of the 7 billion tons of litter that makes its way to the ocean every year. Plastics are often ingested by aquatic species such as sea turtles, or it can act as a snare as in the case of synthetic ropes or strapping bands. Sewage and chemicals make their way to rivers and oceans via storm drains and industrial run-off, while oil spills can choke the life out of ocean habitats.

All these toxins eventually find their way to the tissues of aquatic organisms. The concentration of these toxins grows greater as it passes through the food chain. A sardine that ingests pollution will have a lesser concentration of toxins in its body than will a larger fish that eats the sardine. The concentration of toxins will become even more so for the grouper that eats the larger fish, achieving its peak concentration when it reaches the top of the food chain, which includes us.



Nutrients are an important component of fertilizer, which makes its way from farm lands into the water table, run offs, or rivers, and finally into the ocean. Nutrients increase the population of phytoplankton, minute organisms that are the foundational source of food for ocean life. They are also the reason why the ocean absorbs a third of all the carbon dioxide found in the atmosphere. The burst in the populations of phytoplankton means more carbon dioxide is absorbed by the ocean; more carbon dioxide in the water leads to changes in the water chemistry, which is harmful to ocean life.


Freshwater Ecology

In a few decades, over 20 percent of known freshwater fish species have become extinct or are threatened to become so. Diverting rivers, building dams, water withdrawal, and habitat destruction have all played a part in the destruction of freshwater species. However, the biggest threat to freshwater environments is agriculture. Agriculture consumes 70 percent of all freshwater use. While farming is vital to human survival, sustainable farming practices are needed to prevent the future threat of a water shortage. The non-sustainable use of water in agriculture is exemplified by the fact that it takes 1,300 gallons of water to produce a little over two pounds of rice.


This article was provided by Miranda Tulsi, environmental studies major and animal lover. If you’re looking for off-shore and marine-based consultant work involving critical issues facing the local environment, Miranda suggests riser analysis from Stewart Technology Associates.

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