Quantifying patterns of change in marine ecosystem response to multiple pressures

Area of Science:

• Marine ecology
• Ecosystem-based management
• Ecological modeling

Background:

• Ecosystem-based management requires predicting responses to multiple pressures.
• Quantifying ecosystem reference points is challenging due to complex pressures and responses.
• Ecological indicators can simplify ecosystem status assessment.

Purpose of the Study:

• To quantify the importance of environmental and anthropogenic pressures on ecological indicators in the Northeast Shelf Large Marine Ecosystem (NES LME).
• To identify threshold shifts and nonlinear patterns in ecosystem responses along pressure gradients.
• To evaluate ecosystem reference points for supporting ecosystem-based management.

Main Methods:

• Utilized ecological indicators to represent ecosystem attributes and reduce complexity.
• Employed random forests to assess the predictive power of eight pressure variables (four environmental, four anthropogenic) on ecological indicators.
• Analyzed shifts in ecological indicator responses along pressure gradients to identify thresholds.

Main Results:

• Anthropogenic pressures were more critical than environmental pressures in predicting ecological indicator variation (8-13% vs. 1-5% on average).
• Individual ecological indicators showed significant variation explained by anthropogenic pressures (up to 25-66%).
• Exploitation (commercial landings) emerged as the most important pressure, with critical thresholds at 20% and 60% of total surveyed biomass.

Conclusions:

• Anthropogenic pressures significantly influence the structure and functioning of the NES LME.
• Gradient response curves and identified thresholds provide ecologically informed transformations for pressure variables.
• Ecosystem reference points can be evaluated and utilized for effective ecosystem-based management.