9.9: positive and negative human interactions

What is biodiversity?

The number of different species in a habitat, and the variation between them

What is fish farming?

Fish are bred and grown to maturity in ponds and managed enclosures in estuaries

What are the advantages to fish farming?

The numbers of predators are reduced so more fish can survive, they grow faster as they have a regular food supply, food can be sold cheaper, it is a sustainable process which doesn’t affect wildlife outside of the farms

What are the disadvantages to fish farming?

Diseases can easily be spread between fish due to the enclosed space, fish are crammed into small enclosures due to the demand of cheap food, wild stocks of fish swimming nearby may be affected by the spread of disease, there is an overuse of antibiotics to keep the fish healthy and pesticides are used to control fish parasites, there is lots of pollution of the water and seabeds around fish farms, eutrophication can be caused with fish excretement or fertiliser carried into the surrounding waters of the pens, farmed fish can escape and breed with wild fish which genetically weakens wild stocks (as farmed fish are less adapted to survive in the wild), salmon often contain high levels of dioxins and PBCs which is harmful to humans and the environment, and farmed fish often have poor texture or flavour

What is eutrophication?

Fertiliser run off causes algal blooms on the surface of water, killing aquatic creatures

What is the process of eutrophication?

Excessive nutrients from fertilisers are washed from the land into rivers through rainfall and surface runoff. These fertilisers cause aquatic plant growth of algae, duckweed and other plants on the surface of the water, called algal blooms. This causes oxygen to be depleted from beneath the water as the plants on top prevent oxygen from dissolving into water, as well as sunlight from reaching other plants beneath the water. The plants die and the oxygen in the water is depleted. Decomposition further depletes oxygen, since the decomposers which break down dead organisms need oxygen to respire. Therefore, oxygen levels reach a point where no life is possible, causing fish and other organisms to die.

How can the introduction of non-indigenous species affect biodiversity?

The new species may become naturalised as their populations become established. These species may outcompete native species and damage or change the interdependence of the community