Cumulative stressors reduce the self-regulating capacity of coastal ecosystems

Key points

• Changes in the interactions between biological and chemical processes drive ecosystem function
• Cumulative effects do drive change at every low levels of sedimentation
• Identification of network drivers for ecosystem function can help increase the understanding of degrading ecosystems and their tipping points

Summary

Marine ecosystems, particularly estuaries and coastal areas, are highly dynamic areas that human-based pressures have heavily impacted. When these pressures accumulate in an area, they are referred to as cumulative stressors.

Cumulative stressors can alter the functioning of ecosystems and thus affect the ecosystem services society relies upon. Therefore, the need to understand thresholds and how cumulative stressors interact between themselves and the environment is highly important for environmental managers.

Thrush et al:

• Conducted a nation-wide study assessing how reductions in light at the seafloor due to elevated turbidity disrupts sediment nitrogen processing in estuaries.
• Identified thresholds in light penetration that was related to distinct changes in ecosystem interaction networks that drive nutrient processing.

The results implicate that change in interactions between sediment, nutrient and the environment can alter both biological and chemical processes that drive ecosystem function, giving further evidence that cumulative effects do have the ability to excel tipping points even at low levels.

Identifying network drivers for ecosystem function helps increase the understanding of degrading estuaries and their tipping points and the potential for restoration to influence management interventions.

This work provides empirical validation of the potential for regime shifts and tipping points in ecological systems and justifies to managers and society that these phenomena are real, common, and serious.

The effects observed associated with sediment and nutrient pollution highlight the need for multiple complementary management actions and a move away from approaches that focus on stressors and not ecosystem responses.

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