Report on the Impact of Nutrient and Pharmaceutical Pollution on Freshwater Biofilm Bacterial Communities in the Context of the Sustainable Development Goals

Executive Summary

This report details an in-situ investigation into the effects of nutrient and pharmaceutical pollution on stream biofilm bacterial communities, analyzed through the lens of the United Nations Sustainable Development Goals (SDGs). The study, conducted in montane and urban streams, reveals that anthropogenic contaminants significantly alter the structure and composition of these foundational aquatic communities. Land use, particularly urbanization, was the primary driver of change, directly impacting SDG 6 (Clean Water and Sanitation) and SDG 11 (Sustainable Cities and Communities). Nutrient additions (Nitrogen, Phosphorus, Iron) decreased bacterial richness and promoted the dominance of copiotrophic taxa, posing a risk to the biodiversity and resilience central to SDG 14 (Life Below Water) and SDG 15 (Life on Land). Conversely, pharmaceutical additions (caffeine, diphenhydramine), a challenge linked to SDG 12 (Responsible Consumption and Production), increased bacterial core richness and selected for unique, contaminant-degrading taxa. These findings underscore the distinct and combined pressures of pollution on freshwater ecosystems and highlight the critical need for integrated water resource management to meet global sustainability targets. The study demonstrates that microbial communities are sensitive indicators of pollution and that urban ecosystems may be particularly vulnerable to further contamination.

Introduction: Freshwater Biofilms and the Sustainable Development Goals

Freshwater stream ecosystems are fundamentally supported by biofilms, which are complex communities of bacteria, algae, fungi, and other microorganisms. These communities are the primary form of bacterial life in these environments and are integral to ecosystem health and function. The stability and composition of biofilms directly influence water quality, nutrient cycling, and the overall health of aquatic life, making their study essential for achieving several Sustainable Development Goals.

• SDG 6 (Clean Water and Sanitation): Healthy biofilms contribute to natural water purification processes. Understanding how pollutants disrupt these communities is vital for protecting and restoring water-related ecosystems.
• SDG 14 (Life Below Water): As the base of the aquatic food web, the health of biofilm communities underpins the viability of all life in freshwater systems, which ultimately flow into marine environments.

Biofilm composition is naturally influenced by physicochemical conditions like pH and temperature. However, anthropogenic activities introduce contaminants that can dramatically alter their structure and function, thereby threatening the achievement of sustainability targets.

Impact of Anthropogenic Stressors on Aquatic Ecosystems

Human activities, from agriculture to urban development and consumption, release a variety of contaminants into freshwater streams. This study focuses on two major classes of pollutants: nutrients and pharmaceuticals.

Nutrient Pollution: A Threat to SDG 6 and SDG 15

Nutrient pollution, primarily from nitrogen (N) and phosphorus (P), is a leading cause of global water quality impairment. These nutrients enter waterways through sources directly linked to human land and resource management, impacting key SDGs.

• Sources: Wastewater effluent, agricultural fertilizers, and atmospheric deposition.
• Impact on SDGs:
  1. SDG 15 (Life on Land): Runoff from agricultural and forested lands demonstrates the direct link between terrestrial activities and aquatic ecosystem health.
  2. SDG 6 (Clean Water and Sanitation): Excessive nutrients lead to eutrophication and can alter the balance of microbial communities, impairing ecosystem services.
  3. SDG 11 (Sustainable Cities and Communities): Urban runoff is a significant contributor to nutrient loads in adjacent water bodies.
• Ecological Effect: Nutrient enrichment often favors the growth of opportunistic, copiotrophic species (e.g., Betaproteobacteria, Gammaproteobacteria), which can outcompete other taxa, leading to a reduction in biodiversity and altering ecosystem function.

Pharmaceutical Contamination: A Consequence of Modern Consumption (SDG 12)

Pharmaceuticals are ubiquitous, biologically active contaminants found in surface waters worldwide. Their presence is a direct consequence of modern production and consumption patterns, posing a complex challenge for environmental management.

• Sources: Human and livestock excretion, improper disposal, and wastewater treatment plant effluent.
• Impact on SDGs:
  1. SDG 12 (Responsible Consumption and Production): The widespread presence of pharmaceuticals highlights unsustainable patterns of consumption and waste management.
  2. SDG 6 (Clean Water and Sanitation): Even at low concentrations, these compounds can affect non-target organisms like bacteria, altering microbial processes essential for water quality.
  3. SDG 3 (Good Health and Well-being): While pharmaceuticals are vital for health, their environmental persistence raises concerns about ecosystem and, potentially, human health through contaminated water sources.
• Ecological Effect: Pharmaceuticals can have varied effects, from inhibiting microbial respiration to serving as a carbon source for specific degradation-capable bacteria (e.g., Pseudomonas), thereby selecting for unique, specialized microbial communities.

Methodology: Assessing Contaminant Impacts In Situ

To investigate the effects of these pollutants, an in-situ experiment was conducted using Contaminant Exposure Substrates (CES) in montane (less-impacted) and urban (human-impacted) streams across three catchments in northern Utah, USA. This approach provides ecologically relevant data for monitoring and managing water quality in line with SDG targets.

Study Design

1. Sites: Paired montane and urban sites in the Logan River, Red Butte Creek, and Middle Provo River catchments, representing a gradient of land-use impact relevant to SDG 11.
2. Treatments: CES were deployed with four different treatments to assess distinct and combined impacts:
   • Control (no additions)
   • Nutrient (Nu) addition (N, P, Fe)
   • Pharmaceutical (Ph) addition (caffeine, diphenhydramine)
   • Combined (NuPh) addition
3. Analysis: Biofilms colonizing the CES were collected, and their bacterial community composition was analyzed using 16S rRNA gene metabarcoding. Ambient water quality, including nutrient and pharmaceutical concentrations, was also measured.

Key Findings: Land Use and Contaminants as Drivers of Microbial Community Shifts

The study revealed that both land use and specific contaminants create distinct bacterial core communities, with significant implications for ecosystem management and the achievement of SDGs.

Primary Structuring Factor: Land Use (SDG 11)

The most significant factor structuring biofilm bacterial communities was land use. A clear distinction was observed between communities in montane and urban streams, highlighting the profound impact of urbanization on aquatic ecosystems. This finding directly informs SDG 11 by demonstrating that urban development patterns are a primary determinant of the ecological health of local water bodies.

Effects of Nutrient Additions on Bacterial Cores

Nutrient additions consistently altered bacterial communities in a manner that threatens aquatic biodiversity.

• Community Shift: Nutrients enhanced the dominance of copiotrophic families like Pseudomonadaceae and Comamonadaceae.
• Richness Decline: Bacterial core richness was significantly depressed by nutrient additions in both montane (by 19%) and urban (by 26%) streams.
• SDG Implications: This loss of biodiversity (a key target of SDG 14 and SDG 15) can reduce the resilience of stream ecosystems to other stressors and impair their ability to perform essential functions, such as self-purification, which is critical for SDG 6.

Effects of Pharmaceutical Additions on Bacterial Cores

The effects of pharmaceuticals contrasted sharply with those of nutrients, fostering unique communities.

• Community Shift: Pharmaceuticals selected for unique taxa associated with contaminant degradation, such as DR-16 and WCHB1-32, particularly in urban streams.
• Richness Increase: In contrast to nutrients, pharmaceutical exposure increased bacterial core richness, most dramatically in urban streams (38% increase).
• SDG Implications: This suggests that pharmaceutical pollution (an SDG 12 issue) drives the evolution of specialized microbial functions. While this may enhance bioremediation potential, it represents a significant deviation from natural community structures, the long-term consequences of which are unknown for SDG 6 and SDG 14.

Combined Contaminant Effects and Ambient Pollution

When combined, nutrients were the dominant driver of community structure. However, the combined treatment also selected for unique taxa (e.g., Oscillatoriales), indicating complex interactions in multi-pollutant scenarios. Surprisingly, prior exposure to pollution in urban streams did not dampen the effects of the experimental additions. Instead, urban biofilms showed a stronger response to pharmaceutical additions, suggesting that existing pollution may act as an environmental filter, pre-selecting for taxa that can rapidly respond to or capitalize on further contamination. This underscores the heightened sensitivity of urban ecosystems and the urgent need for robust pollution control measures to support SDG 11.

Conclusion and Recommendations for Achieving SDG Targets

This research demonstrates that nutrient and pharmaceutical pollutants, driven by land use and consumption patterns, create distinct and predictable shifts in freshwater bacterial communities. These alterations have direct consequences for the biodiversity, function, and resilience of aquatic ecosystems, thereby impacting the achievement of multiple SDGs.

Summary of Findings

1. Land use (SDG 11) is the primary determinant of stream biofilm composition.
2. Nutrient pollution (SDG 6, 15) reduces bacterial diversity, favoring dominant copiotrophs and potentially compromising ecosystem resilience.
3. Pharmaceutical pollution (SDG 12) increases bacterial richness by selecting for unique, contaminant-tolerant, or degrading taxa, fundamentally altering natural community structure.
4. Urban streams are not desensitized to pollution; they may harbor communities primed to respond strongly to further contamination, making them critical management hotspots.

Recommendations

• Integrated Pollution Management: To achieve SDG 6, management strategies must address both nutrient and pharmaceutical pollution concurrently, as they co-occur in urban environments and have distinct and interactive effects.
• Sustainable Urban Planning (SDG 11): Urban and agricultural land-use planning must incorporate measures to mitigate runoff and wastewater contamination to protect adjacent aquatic ecosystems.
• Promote Responsible Consumption (SDG 12): Efforts are needed to reduce the environmental load of pharmaceuticals through public awareness campaigns on proper disposal and innovation in wastewater treatment.
• Microbial Bioindicators: Monitoring the composition of biofilm communities can serve as a sensitive and effective tool for assessing the ecological status of water bodies and tracking progress toward water-related SDG targets.

Analysis of Sustainable Development Goals in the Article

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

The article addresses issues related to several Sustainable Development Goals (SDGs) by investigating the impact of human activities, particularly urbanization and agriculture, on freshwater ecosystems.

• SDG 6: Clean Water and Sanitation

  The core of the article revolves around water quality. It explicitly discusses how “freshwater contaminants” like nutrients (Nitrogen, Phosphorus) and pharmaceuticals from “wastewater, fertilizers, and atmospheric deposition” are “a leading contributor to water quality impairment.” The study’s focus on measuring and understanding the effects of these pollutants directly connects to ensuring the availability and sustainable management of clean water.

• SDG 11: Sustainable Cities and Communities

  The research design fundamentally links to SDG 11 by comparing “montane and urban streams.” It highlights the environmental impact of cities, stating that “Urban nutrient run-off… has dramatically altered biofilms” and that urban streams contain distinct signatures of pharmaceutical pollution. This directly addresses the need to reduce the adverse environmental impact of cities on surrounding ecosystems.

• SDG 12: Responsible Consumption and Production

  The article touches upon this goal by examining pollutants that are byproducts of modern consumption and production patterns. The presence of “pharmaceuticals or their transformation products” in aquatic ecosystems across seventy-one countries and nutrients from “chemical fertilizer inputs associated with agriculture” points to the need for environmentally sound management of chemicals and wastes throughout their life cycle to reduce their release into the water.

• SDG 15: Life on Land

  This goal, which includes the protection of inland freshwater ecosystems and biodiversity, is central to the article. The study investigates the health of “stream biofilm bacterial community composition” in response to pollution. Findings that nutrient pollution “depressed bacterial core richness” and altered community structures directly relate to the goal of halting the degradation of natural habitats and biodiversity loss within freshwater ecosystems.

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

Several specific targets can be identified based on the problems and research questions presented in the article.

1. Target 6.3: By 2030, improve water quality by reducing pollution, eliminating dumping and minimizing release of hazardous chemicals and materials, halving the proportion of untreated wastewater and substantially increasing recycling and safe reuse globally.
   • Explanation: The article is entirely focused on the impact of pollution on water quality. It details the release of chemicals and materials, such as “global riverine exports of dissolved inorganic N and P” and the fact that “pharmaceuticals are ubiquitous in human impacted surface waters” due to sources like wastewater. The study aims to understand the effects of these pollutants, which is a prerequisite for managing and reducing them.
2. Target 6.6: By 2020, protect and restore water-related ecosystems, including mountains, forests, wetlands, rivers, aquifers and lakes.
   • Explanation: The study is conducted in “montane and urban streams in three catchments in northern Utah,” which are water-related ecosystems. By assessing how contaminants “dramatically alter biofilm bacterial biomass and composition,” the article provides crucial information needed to understand threats to these ecosystems and to inform protection and restoration efforts.
3. Target 11.6: By 2030, reduce the adverse per capita environmental impact of cities, including by paying special attention to air quality and municipal and other waste management.
   • Explanation: The study’s comparison of pristine montane sites with urban sites directly investigates the environmental impact of cities. It notes that “urban biofilms were exposed to distinct signatures of nutrient and pharmaceutical pollution” from sources like “urban nutrient run-off” and “sewage and septic inputs,” linking urban living and waste management directly to stream degradation.
4. Target 12.4: By 2020, achieve the environmentally sound management of chemicals and all wastes throughout their life cycle… and significantly reduce their release to… water… to minimize their adverse impacts on… the environment.
   • Explanation: The article discusses the widespread environmental contamination by nutrients from fertilizers and pharmaceuticals from human and livestock use. It states that “pharmaceutical pollution is also a global issue” and that these chemicals “are expected to affect non-target organisms, such as bacteria.” This highlights a failure in the sound management of these chemicals, leading to their release and adverse environmental impacts.
5. Target 15.1: By 2020, ensure the conservation, restoration and sustainable use of terrestrial and inland freshwater ecosystems and their services…
   • Explanation: The research is a direct investigation into the health and functioning of “inland freshwater ecosystems” (streams). By studying the “in situ responses of stream biofilm bacteria to nutrient… [and] pharmaceutical… additions,” the article contributes to the knowledge base required for the conservation and sustainable management of these environments.
6. Target 15.5: Take urgent and significant action to reduce the degradation of natural habitats, halt the loss of biodiversity and, by 2020, protect and prevent the extinction of threatened species.
   • Explanation: The article provides direct evidence of biodiversity loss at the microbial level. A key finding was that nutrient additions “depressed bacterial core richness by at least 19 and 26% at montane and urban sites, respectively.” This loss of bacterial taxa is explicitly linked to a reduction in “genetic diversity and, consequently, biofilm resilience to disturbance,” which is a clear example of biodiversity loss due to habitat degradation from pollution.

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

The article mentions and uses numerous quantitative indicators that can measure progress towards the identified targets. These are the core measurements used in the study to assess water quality and ecosystem health.

• Ambient Nutrient Concentrations:

  The study measured concentrations of Total Nitrogen (TN), Total Phosphorus (TP), nitrite + nitrate (NO₃⁻), ammonium (NH₄⁺), and Soluble Reactive Phosphorus (SRP). These are direct indicators of water quality (Target 6.3) and pollution from urban and agricultural sources (Targets 11.6, 12.4). Lowering these concentrations in water bodies would indicate progress.

• Ambient Pharmaceutical Concentrations:

  The study measured the concentrations of 19 different pharmaceuticals, including caffeine and diphenhydramine. These measurements serve as direct indicators of chemical pollution from municipal waste (Targets 6.3, 11.6, 12.4). Tracking the presence and concentration of these “emerging organic contaminants” is crucial for assessing the effectiveness of waste management.

• Bacterial Community Richness and Diversity:

  The study calculated “bacterial core richness as the number of OTUs” and diversity using Shannon’s diversity index. These metrics are direct indicators of biodiversity health within the stream ecosystem. A decrease in richness, as observed with nutrient pollution, indicates habitat degradation and biodiversity loss, directly relevant to Target 15.5. An increase or stabilization of richness would indicate progress in ecosystem restoration.

• Bacterial Community Composition:

  The analysis of the relative abundance of different bacterial phyla (e.g., Proteobacteria, Bacteroidetes) and families (e.g., Pseudomonadaceae) serves as a bioindicator of ecosystem condition. The article shows that nutrient additions “enhanced the dominance of the Pseudomonadaceae and Comamonadaceae,” indicating a community shift towards pollution-tolerant species. Monitoring these compositional shifts can indicate the level of stress on an ecosystem (Targets 6.6, 15.1).

• Biofilm Biomass:

  The measurement of “ash-free dry mass (AFDM) and chlorophyll a concentrations” was used to estimate total organic and photoautotrophic biomass. Changes in biomass in response to contaminants indicate a disruption of fundamental ecosystem processes like growth and productivity, serving as an indicator for the overall health of the water-related ecosystem (Targets 6.6, 15.1).

4. Create a table with three columns titled ‘SDGs, Targets and Indicators” to present the findings from analyzing the article. In this table, list the Sustainable Development Goals (SDGs), their corresponding targets, and the specific indicators identified in the article.

Source: frontiersin.org