Section 9.5 Wha.t is the key concept for this section? Summarize the threats to aquatic biodiversity resulting from human activities. What is ocean acidification and why is it a major threat to aquatic biodiversity? Define fishery and summarize the threats to marine fisheries. Describe the major industrial fish harvesting methods. What percentage of the world’s commercial fisheries has been fully exploited overfished? Explain how jellyfish can upset marine ecosystems and how human activities affect jellyfish populations. Why is it difficult to protect marine biodiversity? What is a marine protected area? What is a marine reserve? What are three ways to protect marine biodiversity? What percentage of the world’s oceans is strictly protected from harmful human activities in marine reserves? Summarize the contributions of Sylvia Earle to the protection of aquatic biodiversity. Describe the role of restoration in protecting marine biodiversity. What are six ways to apply the ecosystem approach to protecting aquatic biodiversity?

The fundamental concepts of the section and summarize the threats that are faced by the aquatic biodiversity resulting from human activity. The definition of ocean acidification and whether it as a significant threat to biodiversity or not. The definition of fishery and risks that it meets. The industrial fish harvesting methods and the percentage of fisheries that have been overexploited. The effect of jellyfish blooms in disrupting the ecosystem and link it to human influence. The definition of marine protected area and a marine reserve and the percentage of area under marine reserves. The methods used to preserve marine diversity. The efforts of Sylvia Earle in the protection of aquatic biodiversity. The role of restoration in protecting marine biodiversity and six ways in which the ecosystem approach can be applied to protect the aquatic biodiversity.

The section discusses the concepts of a marine and aquatic habitat and how the human activities have to lead to over-exploitation and destruction of marine habitats. Further, the methods to sustain aquatic biodiversity are also discussed.

The trawler fishing boats have destroyed sea bottom habitats. The building of dams and usage of water for water supplies for cities has destroyed the freshwater habitats. Also, due to the deliberate introduction of some invasive species, the aquatic habitats and the native species are at risk of extinction.

The decrease in the pH of the ocean water due to increased CO₂ is called ocean acidification. The increase in the CO₂ levels leads to an increase in the bicarbonate ions. The carbonate ions present in water also form bicarbonate upon reacting with H⁺. It leads to the absence of carbonate ions leaving the sea organisms incapable of making shells. Further, the increased acidity leads to dissolving of the calcium carbonate shells.

Three ways in which marine biodiversity can be protected is:

(i) Protecting endangered and threatened species.

(ii) Establishment of marine protected areas.

(iii) Establishment of marine reserves.

With the advancement of commercial fishing equipment and the amount of catch that can be managed has increased and so has the demand. It has led to overfishing. It is suggested that 87% of the world’s commercial fisheries have been fully exploited or overfished. Also, with the increased fishing of small fish called forage fish the food for bigger fish is depleting, causing a danger to the existence of the marine species of the fisheries.

The bloom in the jellyfish population will disrupt the food web. The disruption of the food web will lead to the perturbation of the ecosystem...