Web of Contamination: Shoreline Spiders Transfer Mercury up the Food Chain

Shoreline Spiders and the Movement of Mercury Contamination

Introduction

Researchers have highlighted the role of certain shoreline spiders, particularly long-jawed spiders, in moving mercury contamination from aquatic regions to terrestrial ecosystems. Mercury, which largely comes from industrial pollution, can enter water systems and be converted into a toxic form, methylmercury. This methylmercury then travels up the aquatic food chain and is consumed by spiders, which are, in turn, eaten by land animals.

Spiders as Mercury Transporters

Sitting calmly in their webs, many spiders patiently await prey to come to them. Arachnids along lakes and rivers eat aquatic insects, such as dragonflies. When these insects live in mercury-contaminated waterways, they can pass the metal along to the spiders that feed on them. Now, researchers reporting in ACS’ Environmental Science & Technology Letters have demonstrated how some shoreline spiders can move mercury contamination from riverbeds up the food chain to land animals.

Origins and Transfer of Mercury

Most mercury that enters waterways originates from industrial pollution and other human activities, but it can also come from natural sources. Once in the water, microbes transform the element into methylmercury, a more toxic form, which biomagnifies and increases in organisms up the food chain.

Scientists increasingly recognize spiders living on lakeshores and riverbanks as a potential link between contamination in waterways and animals that mostly live on land, such as birds, bats, and amphibians, which eat the insects. So, Sarah Janssen and colleagues wanted to assess if shoreline spiders’ tissues contain mercury from nearby riverbeds and establish how these animals could connect mercury pollution in water and land animals.

Research Findings

The research team collected long-jawed spiders along two tributaries to Lake Superior, and they sampled sediments, dragonfly larvae, and yellow perch fish from these waterways. Next, the team measured and identified the mercury sources, including direct industrial contamination, precipitation, and runoff from soil. The team observed that the origin of mercury in the sediments was the same up the aquatic food chain in wetlands, reservoir shorelines, and urban shorelines. For instance, when sediment contained a higher proportion of industrial mercury, so did the dragonfly larvae, spider, and yellow perch tissues that were collected.

Based on the data, the scientists say that long-jawed spiders could indicate how mercury pollution moves from aquatic environments to terrestrial wildlife. The implication of these findings is that spiders living next to the water provide clues to the sources of mercury contamination in the environment, informing management decisions and providing a new tool for monitoring of remediation activities, explain the researchers.

Species Variations and Contamination

The researchers also collected and analyzed tissues from two other types of arachnids from some sites: fishing spiders and orb-weaver spiders. A comparison of the data showed that the mercury sources varied among the three taxa. The team attributes this result to differences in feeding strategies. Fishing spiders hunt near water but primarily on land; orb-weavers eat both aquatic and terrestrial insects; but it’s the long-jawed species that feed most heavily on adult aquatic insects.

According to the researchers, these results suggest that although long-jawed spiders can help monitor aquatic contaminants, not every species living near the shore is an accurate sentinel.

Conclusion

The movement of mercury contamination from aquatic regions to terrestrial ecosystems through shoreline spiders, particularly long-jawed spiders, has significant implications for environmental management and monitoring. By studying the tissues of these spiders, researchers can gain insights into the sources of mercury pollution and make informed decisions about remediation activities. This research contributes to the Sustainable Development Goals (SDGs) by addressing Goal 14: Life Below Water and Goal 15: Life on Land, as it highlights the interconnectedness of aquatic and terrestrial ecosystems and the impact of pollution on wildlife.

Reference

“Mercury Isotope Values in Shoreline Spiders Reveal the Transfer of Aquatic Mercury Sources to Terrestrial Food Webs” by Sarah E. Janssen, Christopher J. Kotalik, Collin A. Eagles-Smith, Gale B. Beaubien, Joel C. Hoffman, Greg Peterson, Marc A. Mills, and David M. Walters, 13 September 2023, Environmental Science & Technology Letters. DOI: 10.1021/acs.estlett.3c00450

Acknowledgements

The authors acknowledge funding from the U.S. Geological Survey Environmental Health Program and the U.S. Environmental Protection Agency Great Lakes Restoration Initiative.

SDGs, Targets, and Indicators

1. Which SDGs are addressed or connected to the issues highlighted in the article?

• SDG 14: Life Below Water – The article discusses the movement of mercury contamination from aquatic regions to terrestrial ecosystems, highlighting the impact on land animals.
• SDG 15: Life on Land – The article focuses on the transfer of mercury pollution from water to land animals through the food chain.

2. What specific targets under those SDGs can be identified based on the article’s content?

• SDG 14.1: By 2025, prevent and significantly reduce marine pollution of all kinds, particularly from land-based activities, including marine debris and nutrient pollution – The article highlights the role of shoreline spiders in transferring mercury contamination from water to land animals, indicating the need to address pollution sources.
• SDG 15.1: By 2020, ensure the conservation, restoration, and sustainable use of terrestrial and inland freshwater ecosystems and their services, in particular forests, wetlands, mountains, and drylands, in line with obligations under international agreements – The article emphasizes the impact of mercury contamination on terrestrial ecosystems and the need for conservation and restoration efforts.

3. Are there any indicators mentioned or implied in the article that can be used to measure progress towards the identified targets?

The article does not explicitly mention specific indicators to measure progress towards the identified targets. However, potential indicators could include:

• Concentration of mercury in shoreline spider tissues – This indicator can provide insights into the level of mercury contamination in aquatic environments and its transfer to terrestrial wildlife.
• Proportion of industrial mercury in sediments and tissues of aquatic organisms – This indicator can help assess the contribution of industrial pollution to mercury contamination in waterways and its subsequent impact on land animals.

SDGs, Targets, and Indicators

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Source: scitechdaily.com

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