Understand how climate, pollution and runoff combine in coastal ecosystems

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Griffith University researchers are discovering how stressors like climate change, pollution, dissolved nitrogen and sediment from runoff have combined effects on coastal ecosystems.

Two studies published in Ecology Letters and Proceedings of the Royal Society B reveal that the combination of increased ocean temperatures, pollution or dissolved nitrogen with reduced light caused by sediment in the water can amplify or reduce the impact of these stressors individually on seagrass beds or algae growth.

“Essentially, we show that the combined effects on seagrass and algal growth can vary greatly depending on the amount of the two stressors and the duration of exposure,” said Dr. Mischa Turschwell, a researcher at the ‘Australian Rivers Institute.

“With the onset of climate change, coastal and marine ecosystems are threatened on more than one front by stressors such as rising ocean temperatures, poor water quality and pollution.

“To effectively care for these coastal ecosystems, managers need a thorough understanding of the effects of these human-induced changes, both individually and in combination.”

Associate Professor Chris Brown, head of the Seascape Models group at the Australian Rivers Institute and the Coastal and Marine Research Centre, lamented that “to date most attempts to uncover how these stressors interact, using data pooled from multiple studies, failed to find consistent information”. predictions for combined effects.”

“Few generalities about the combined effects of these stressors have been observed, with meta-studies based on multiple past studies of the same stressors often yielding conflicting results.”

With far too many combinations of potential stressors for researchers to hope to measure them all, accurate models are needed to predict how potential environmental stressors interact.

Dr. Turschwell and his team built a model to predict how temperature and light interact to affect photosynthesis and seagrass growth, which also included an animal that consumed seagrass.

“Using the model, we assessed the combined effect of temperature and light in the water, changing the amount of both and the exposure time,” Dr Turschwell said.

“Amazingly, our model revealed how the combination of the same two stressors could amplify or attenuate their individual consequences on seagrass growth.

“The combined impact on the seagrass beds was highly dependent on changing amounts of the stressors. For example, when higher levels of light loss were combined with temperature, the interactive impact became stronger.

“When seagrass-eating organisms were added to the model to better simulate real-world systems, the combined effect of temperature and light loss on seagrass growth changed further.”

To determine if these patterns are a true indication of what happens when water quality stressors are combined, Ph.D. candidate Olivia King conducted experimental studies on the interactive effects of three water quality stressors. common stresses; a herbicide (diuron), dissolved inorganic nitrogen and reduced light (due to sediment).

Pollution of coastal waters, such as herbicides in agricultural runoff and sediments from erosion, can affect the growth of important algal species.

Similar to findings using the model, Dr. King’s study of multiple stressors like diuron and reduced light could amplify or reduce their individual effects, depending on changing amounts of these pollutants, duration of exposure or of the biological response examined.

“This research clearly shows why it has been so difficult in the past to get a clear picture of how multiple stressors interact, as their combined effect can vary depending on factors such as duration and amount used.”

“To develop consistent models of these interactions, we need to learn how stressors change with context and develop experiments accordingly that run over extended time scales, with treatments across gradients of stress levels. “

There is an urgent need to better understand the combined impact of multiple simultaneous stressors affecting the marine environment, in order to provide useful predictions of the highest priority stressors that managers of marine ecosystems need to address.

“Water quality on the Great Barrier Reef, for example, is managed using guidelines that currently only consider one pollutant at a time,” said Associate Professor Brown.

“Our work shows the need for and process of updating water quality guidelines for the Great Barrier Reef and other important ecosystems to account for the amplifying effects of multiple pollutants.

“Similarly, the combined effects of pollutants and increased warming make it clear that water quality guidelines need to consider how increasing levels of climate change will interact with pollution.”

Need for better approaches to tackle multiple stressors in European lakes and rivers

More information:
Mischa P. Turschwell et al, The interactive effects of multiple stressors vary depending on consumer interactions, stressor dynamics and magnitude, Ecology Letters (2022). DOI: 10.1111/ele.14013

Olivia C. King et al, Interactions between multiple stressors vary with duration of exposure and biological response, Proceedings of the Royal Society B: Biological Sciences (2022). DOI: 10.1098/rspb.2022.0348

Provided by Griffith University

Quote: Unraveling how climate, pollution and runoff combine in coastal ecosystems (2022, May 24) retrieved May 30, 2022 from https://phys.org/news/2022-05-unraveling-climate-pollution-runoff -combine.html

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