Identify two changes between 2003 and 2011 along the southern shore of the lake between Sandusky and Cleveland.

Outline one environmental problem caused by eutrophication.

Explain one human reason and one physical reason why some areas of a freshwater lake such as this experience high levels of eutrophication.

• Increased severity [1].
• Greater area of water affected [1].
• Increased distance from shore affected [1] / 100-150 km distance [1].

Award [1] for the problem and [1] for development.

For example: Fish die [1] due to oxygen depletion [1].

Possible problems include:

• declining biodiversity
• creation of dead zones
• excessive vegetation on surface.

In each case, award [1] for the reason and up to [2] for development / explanation.

Possible human reasons include:

• agricultural
• industrial
• settlement.

For example: Runoff from farming into particular parts of the lake [1] carries high amounts of nitrates [1] that were used as fertilizer [1].

Possible physical reasons include:

• drainage patterns
• wind / storms / currents
• hydrological flows
• relief
• depth/temperature of water.

For example: An area of water with many rivers draining into it [1] will receive more inputs of dissolved nutrients in solution [1], leading to excessive algae growth in that part of the lake [1].

Most could identify two changes although some commented on areas outside of the requirement (Between Sandusky and Cleveland).

Knowledge of eutrophication was good with most able to outline an environmental problem.

Most identified farming and fertilizer as the human reason, with only a few referring to industry or urbanization. Physical reasons were not explained well and, in most cases, seemed to be guesswork.