Seafood Magazine: Human activity puts pressure on marine ecosystem

Shared with permission from Seafood New Zealand Magazine - August 2022

Multiple stressors created by human activity on the land and sea are putting increasing pressure on our marine environment.  

The Sustainable Seas National Science Challenge is researching how stressors interact with each other, and how they might be reduced or mitigated to ensure ecosystems can continue to provide for future generations.  

The project Ecological responses to cumulative effects is bringing together mātauranga Māori and science to identify how ecosystems respond to cumulative effects and how they might be put at risk because of future change. 

The research focuses on soft sediment and rocky reef biodiversity and ecosystem functions that underpin many of our inshore fisheries and affect their long-term viability and market position.   

Marine management practice typically considers stressors like sedimentation, pollution, climate change, coastal engineering, farming, and fishing in isolation, says head of University of Auckland's Institute of Marine Science, and the project’s co-lead, Professor Simon Thrush.  

This is an ineffective way of thinking about cumulative effects because they impact on an ecosystem at multiple levels, and manifest in different ways.  

“It is not a simple cause-and-effect or dose-response relationship.” 

University of Waikato marine sciences Professor Conrad Pilditch is involved in the research and is also part of Sustainable Sea’s leadership team. He notes the way stressors interact also depends on the context of place and time. 

“Take sediment for example: it depends on the actual load of sediment but effects in an open coastal environment or a well-flushed estuary will be different, as will effects in healthy versus degraded seafloors. The system’s capacity for bouncing back from stress will depend on both the local environment and the ecosystem,” he explains.  

“If we want to enhance utilisation of our marine resources within environmental and biological constraints wisely, we need to combine overarching principles with place-based practices. We know managers and industry want certainty that what they’re doing is the right thing, but how a system reacts to stressors depends on the local context.”  

The project is doing field studies, developing models, and working with environmental initiatives across Aotearoa New Zealand that support ecosystem-based management developments. This includes research in Tauranga and Southland on whether adding shellfish into estuaries can help processing the nutrient loads.  

“Our changing land use practice is increasing nutrient load. Our field studies allow us to look at the role animals play in mobilising and removing those nutrients and lowering the risk of algal blooms,” Thrush explains.  

“It is not just about understanding the negative impacts we're having on the system, but also how we might fix it through management, community actions, and kaitiakitanga.” 

Thrush says the way management decisions are made need to be urgently reframed to reflect the way cumulative effects impact on ecosystems.   

“One important thing to bear in mind when considering cumulative effects is that we’re all in the same waka, and what we need to do is work together to fix the problem.”  

Read more: www.sustainableseaschallenge.co.nz/seafood-tools-resources-and-research