Aquatic environments are affected by human activities, sometimes dramatically and sometimes in more subtle ways. The key to keep track of changes and what measures are most effective, is environmental monitoring.  Through several monitoring programs, large scale impact on, for instance, eutrophication and toxins on biodiversity and ecosystem health are assessed.

" This work is vital, and also critical for researchers. The environmental monitoring is the best tool we have to follow ecosystem scale responses to environmental change", said Francisco Nascimento, Associate Professor at the Department of Ecology, Environment and Plant Sciences, Stockholm University.

At the same time, demands from environmental goals, legislations and directives are increasing, while funding remains unstable and unpredictable. Nascimento finds these things a challenge to meet.

" We can ask ourselves if the traditional methods that we have are sufficient to comply with all new demands and if they can deliver on all these", he said.

In his research, Nascimento investigates the possibilities to complement two of the existing monitoring programs in the Baltic Sea with new techniques.

Francisco Nascimento: Foto: Lisa Bergqvist

Potential in eDNA and new ecological indicators

Today’s monitoring of sediment living communities is directed towards macrofaunal organisms, such as mussels, worms or crustaceans larger than 1 millimeter. This community is the only core indicator for biodiversity according to Helcom, even though it has a naturally low species richness in the Baltic Sea which creates problems when assessing ecological health. To find diversity, Nascimento suggested that we rather examine the smallest organisms.

"If we try to look a bit closer, the Baltic Sea is not really species poor. It is a rich community of meiofauna (animals smaller than 1 millimeter). A fist full of sediments could contain a dozen species and we think there are 200 species of nematodes in the Baltic".

"We actually track the core indicators for biodiversity while ignoring the most diverse communities that we have in the Baltic sediments and this is not mentioning bacteria and protist communities (even smaller organisms) that also have high potential to function as ecological indicators", Francisco Nascimento said.

According to Nascimento, environmental DNA, or eDNA, offers a huge opportunity to contribute to ecological and environmental monitoring. Using eDNA, or traces of DNA, such as skin cells or mucus, that all organisms shed when they move in different surroundings, is proven to be a cost-efficient and non-invasive technique that detect species simply by analysing the genetic material that is left in the sediment.

"The beauty of DNA is that you can capture several communities simultaneously. You can target nematodes, bacteria or protists if you desire. I think eDNA shows great promise in benthic monitoring and can help us deliver these demands of environmental monitoring in more cost-efficient way. But the question is how to up-scale".

In recent research, Nascimento and colleagues evaluated how data based on eDNA could be used to develop indicators for classifying habitat status, with pleasing results – the new technique provides similar classifications as the traditional method.

Using satellites to track marine plants and algae

To follow the distribution and composition of bottom vegetation is another important way to assess the marine environmental status. This heavily relies on divers with good skills in species identification, which limits how large areas could be examined.

"This brings us to the potential of remote sensing. Using satellite imagery makes it possible to cover larger areas than divers can. Tools are existing and are being developed like the Sentinel 2 satellites that can help us try large scale monitoring of macrophyte-covered bottoms", Francisco Nascimento suggests.

New studies from the Estonian bay showed the satellites to be capable of detecting growth of macrophytes and changes in coverage in the spring and summer, and Nascimento sees potential in investigating the opportunities with this technique. Questions remain of how accurate these methods are when you compare the results with diving data.

"Our vision is to improve and leverage these new technologies. We hope we can help Sweden and other EU members to meet their national and international goals", Francisco Nascimento concluded.

Detecting chemicals before it is too late

The EU has set an ambition for zero pollution with the aim of a toxic free environment. A focus for reaching this ambition is to improve and implement better monitoring of chemical pollution in environmental samples. But the rapidly increasing rate of production and release of chemicals makes it impossible to track them with the current assessment methods, said May Britt Rian, PhD student at the Department of Environmental Sciences.

"With the traditional monitoring approaches we usually apply what we call targeted analysis – for instance target a small group of chemicals that we know exist in our sample. We can quantify these and do risk assessments and compare with toxicity values", May Britt Rian explained.

But these methods have never been proactive or able to prevent widespread environmental contamination. Several examples of this are shown in the past, for instance with PCBs the chemicals have been discovered once it is too late to stop widespread environmental contamination.

May Britt Rian. Photo: Lisa Bergqvist.

More than 350 000 chemicals are registered in global commerce. The majority is not monitored in the environment and information on toxic properties, persistence or how they spread in the environment is scarce.

"Only a few hundred are monitored routinely. There is a huge knowledge gap that we have to fill by applying more discovery-based methods", May Britt Rian said.

Instead of screening for a few, targeted substances, these methods can detect over thousands of chemical signals in one sample, including unknown ones. The methods are already applied in research labs, such as Rian’s where drinking water and wastewater have been analysed to detect persistent chemicals.

"We detected over 70 000 signals in wastewater samples, 15 000 persisted through wastewater treatment and could reach the environment".

Even in the drinking water, persistent chemicals was found.

"PFBS (PFAS) could be detected with high detection frequencies in all samples, there was almost 80% frequency in the tap water samples".

According to Rian, the benefits of these non-target approaches are that they can accelerate the discovery of contamination that already exists but also be used to proactively monitor the environment of new or emerging hazards. Applications could include the new EU Urban Waste Water Treatment Directive where these methods could play a crucial role.

"One of the points in this directive is to improve environmental monitoring of chemicals. I think it can be applied in monitoring the effluents after being treated to see what we are releasing, and that could help prioritise which chemicals to add to the monitoring", May Britt Rian concluded.

Text: Isabell Stenson