Environmental DNA monitoring has become one of the most effective tools available for non-invasive marine and freshwater ecological assessment. Rather than trawling, netting, or direct observation, marine eDNA sampling captures the genetic traces organisms leave behind in the water column – a more efficient, less disruptive approach to understanding what lives in an environment. If you’re new to the subject, our guide to what eDNA monitoring is and why it’s useful for marine biodiversity research covers the foundations.

Subsea Commercial Services now supplies both DOT eDNA sampler systems: the original autonomous eDNA Sampler and the newly available eDNA Rapid Sampler. Each is built around the same core purpose but optimised for different operational contexts. Understanding the difference is the first step to choosing the right tool for your project.

The DOT eDNA Sampler: built for long-term autonomous deployment

The DOT eDNA Sampler is designed for long-term environmental DNA monitoring in locations that are difficult or impractical to service regularly. It handles sample collection, cleaning, and preservation entirely onboard – a self-priming, self-cleaning, self-preserving system that operates independently once deployed.

Each filter cassette holds 9 DNA filters, and the sampler carries enough reagent chemistry to clean and preserve 3 full cassettes, for a total capacity of 27 DNA filters per deployment. Reagents are stored and deployed onboard, with no external support required.

Triggering is flexible: samples can be scheduled by date and time, activated by depth or pressure, or initiated by a third-party sensor or device via RS-232 serial connection. The self-cleaning cycle between each sample significantly reduces cross-contamination risk – an important consideration when data integrity is paramount.

This sampler is the right choice when access is the primary constraint. For a deeper look at how autonomous eDNA systems perform in practice – including deployment planning, contamination control, and power considerations – see our post on using autonomous eDNA sampling in marine environments.

The DOT eDNA Rapid Sampler: built for high-volume collection

The eDNA Rapid Sampler is the newest addition to the DOT range, and it takes a different approach to marine eDNA sampling. Rather than prioritising long-term autonomy, it’s optimised for high-volume collection in a compact, vehicle-compatible package.

Flow rates of up to 600 mL per minute mean it can collect up to ten times the sample volume per filter compared to the original sampler, in a fraction of the time. Nine dedicated pumps serve nine individual DNA filters, and the power management design to stagger in-rush current supports parallel collection: single, dual, or triplicate samples can be collected simultaneously from the same location.

Removing the onboard reagent system results in a significantly more compact footprint, making the Rapid Sampler well-suited to ROV or AUV payload bays where size and weight are always considerations. Communication options have also been expanded, with RS-232, RS-485, and Ethernet all supported for integration with wider vehicle or monitoring systems.

Environmental DNA monitoring applications

Both samplers support the same range of environmental DNA monitoring applications across marine and offshore environments.

Commissioning and decommissioning surveys for oil and gas infrastructure, offshore wind farms, and aquaculture sites require robust baseline and impact data. Both eDNA samplers are well-suited to generating that data non-invasively and at scale.

Targeted species detection is another core use case – whether monitoring for harmful algal species such as Alexandrium, tracking parasites or pathogens in aquaculture environments, or assessing biodiversity through indicator species.

In all cases, filters are returned for laboratory processing, where DNA extraction can be followed by methods such as qPCR for precise quantification and species identification.

Which eDNA sampler is right for your project?

The decision comes down to deployment context. If the priority is long-term, low-maintenance autonomous monitoring from a fixed or moored position, the autonomous eDNA Sampler’s built-in preservation and cleaning functions are a significant operational advantage. If the priority is collecting large sample volumes quickly – particularly from a mobile platform such as an ROV or AUV – the Rapid Sampler’s throughput and compact design make it the more practical choice.

In some project designs, both have a role: the Rapid Sampler is deployed during active survey passes, with the eDNA Sampler providing continuous background monitoring between visits.

Purchase or rent DOT eDNA samplers through SCS

SCS supplies both DOT eDNA sampler systems for purchase and rental. Whether you need long-term autonomous environmental DNA monitoring capability or high-volume rapid sampling for a specific survey campaign, we can help you identify the right solution and support you through deployment.

Get in touch with the SCS team to discuss your requirements.

For anyone already familiar with what eDNA monitoring is and how it works, the next question is usually a practical one: how do you deploy it consistently, in difficult environments, over time? For programmes operating offshore or in locations with limited access, autonomous sampling is increasingly part of the answer. Getting it right requires careful consideration of how, where, and when samples are collected.

Why sampling strategy matters? 

eDNA monitoring is only as useful as the data it produces, and the quality of that data depends heavily on how sampling is designed. Frequency, timing, location, and depth all shape what the results can tell you – and what they can’t. 

A one-off sample gives you a snapshot. It can be useful, but it can’t tell you whether a species is present seasonally, how populations change over time, or whether a particular event had a measurable effect on the local environment. For those questions, you need repeat sampling collected consistently, at defined intervals, from the same locations.

Getting the strategy right before deployment is also important because eDNA results are sensitive to the conditions in which samples are collected. For example, currents can carry genetic material away from its source, warmer water can speed up degradation and samples taken at the wrong time or depth may not reflect what you’re trying to monitor. Therefore, it’s important to plan eDNA monitoring carefully.

Manual vs autonomous sampling 

Manual sampling (collecting water samples by hand, usually from a vessel) is well-established and works well for many applications. It’s straightforward to set up, doesn’t require specialist equipment beyond filtration and storage, and gives you direct control over each sample.

The limitation is access. Offshore sites, remote locations, and environments with unpredictable weather or limited vessel availability make regular manual sampling difficult to sustain. When access is inconsistent, so is the data, and gaps in a time series are hard to recover.

Autonomous sampling systems address this by collecting samples on a programmed schedule without requiring someone to be present each time. Once deployed, they can run across multiple time points, at depth, in locations that would be impractical to visit repeatedly by vessel. They do, however, require more upfront planning and careful deployment to work well. 

The right choice depends on the environment, the monitoring objectives, and the programme’s operational constraints.

Deployment considerations

If autonomous sampling is the right fit, several practical factors need to be worked through before deployment.

Repeat sampling

The main advantage of autonomous systems is their ability to collect multiple samples over time from the same location. To make the most of this, sampling intervals need to be chosen with the monitoring objective in mind. Seasonal studies require different timing to baseline surveys or impact assessments. Deciding this upfront and building it into the deployment plan produces far more usable data than adjusting as you go.

Contamination control

Contamination is a major source of error in eDNA work. In a lab setting, protocols are well established. In the field, it’s more complex. Autonomous systems need to be designed and handled to minimise the risk of cross-contamination between samples, and the retrieval process requires the same care as deployment.

Power and retrieval

Autonomous systems deployed for extended periods require sufficient power to complete the sampling schedule, which affects how they are configured and how long they can realistically be left in the water. Retrieval also needs careful planning, particularly in deeper or more exposed locations, where recovering equipment isn’t straightforward.

Harsh and remote environments

Marine environments can be demanding on equipment. Depth, pressure, biofouling, strong currents, and temperature variation all affect how autonomous systems perform over time. Systems intended for offshore or deep-water should be designed with these conditions in mind.

Where autonomous systems are most appropriate

Autonomous eDNA sampling tends to work best where one or more of the following apply:

●      The site is remote, offshore, or difficult to access regularly

●      The programme requires data across multiple time points or seasons

●      Consistency across sampling events is essential to how results will be used

●      Vessel availability or weather windows make repeat manual sampling unreliable

Applications across sectors

Autonomous eDNA sampling is used across a range of marine contexts. In ocean science, it supports long-term biodiversity programmes and species distribution research in locations that are difficult to monitor otherwise. In offshore energy, it contributes to environmental monitoring programmes that require consistent, repeatable data over the life of a project. In aquaculture, it can provide regular biological data to support ecosystem awareness alongside other monitoring systems. 

Across all of these, the underlying requirement is the same: reliable sampling in variable, limited-access environments.

Thinking about eDNA monitoring for your programme? 

If you’re at the stage of working out what eDNA monitoring could look like in practice – whether that’s understanding the options, scoping a deployment, or finding the right equipment – we’re happy to talk through your requirements.

Understanding what is happening beneath the surface of the ocean is operationally challenging. Marine environments are complex, dynamic, and often difficult to access, yet reliable biodiversity data is increasingly required to support environmental assessment, monitoring programmes, and long-term project planning.

Environmental DNA (eDNA) has become a valuable tool in marine biodiversity monitoring, providing a way to detect biological presence without relying on direct observation or physical capture. For those working in challenging marine environments, eDNA offers an additional source of biological data that can complement established monitoring approaches.

Rather than replacing existing survey methods, eDNA monitoring is most effective when integrated into a broader monitoring system.

What is eDNA monitoring?

Environmental DNA monitoring involves collecting water samples and analysing them for genetic material released by organisms into the surrounding environment. This material originates from naturally occurring biological traces such as skin cells, mucus, scales, or waste.

Following sample collection, laboratory analysis is used to identify genetic signatures associated with different species. The results indicate which organisms are, or have recently been, present in a given area, without requiring visual confirmation or physical interaction.

In marine environments, eDNA monitoring is particularly relevant where visibility is limited, access is constrained, or repeated surveys are required across depth or distance.

How eDNA monitoring works in marine environments

While the basic principles of eDNA monitoring are well established, implementation in marine settings requires careful consideration.

A typical marine eDNA monitoring workflow includes:

●      Water sampling at defined locations and depths

●      Sample handling and preservation to reduce contamination and degradation

●      Laboratory analysis to identify genetic material

●      Interpretation of results alongside environmental and operational data

Marine conditions introduce additional variables. Currents, water movement, temperature, and salinity all influence how eDNA disperses and how long it remains detectable. As a result, sampling strategy and deployment design are critical.

From an operational perspective, repeatability, consistency, and integration with other monitoring data are often more important than single-point results.

Why eDNA is useful in applied marine monitoring

When used appropriately, eDNA monitoring can support marine biodiversity programmes by complementing traditional survey methods.

It can help identify species that are difficult to detect visually, including low-abundance or cryptic organisms. It is also well-suited to deep, remote, or low-visibility environments in which conventional surveys are constrained by deployment time, weather windows, or access limitations.

Because eDNA sampling does not require physical interaction with organisms or habitats, it can be applied in sensitive environments where minimising disturbance is a consideration.

This makes eDNA a practical addition to monitoring programmes that already rely on imaging, sensors, or remote platforms.

Limitations and practical considerations

eDNA monitoring effectiveness must be viewed in the context of the deployment environment and project related factors. The presence of genetic material does not always indicate the presence of living organisms at the precise sampling location, as DNA can persist in the environment and be transported by water movement.

Results are influenced by sampling design, contamination control, environmental conditions, and analytical methods. These factors must be considered at the programme design stage to ensure data is interpreted appropriately.

In applied monitoring contexts, understanding these limitations is essential to use eDNA data responsibly and effectively.

Integrating eDNA into wider monitoring systems

In operational marine monitoring, eDNA delivers the most value when integrated with other technologies rather than deployed in isolation.

Optical imaging, environmental sensors, acoustic systems, and physical surveys each provide different data types. eDNA adds a biological dimension that can strengthen overall understanding when aligned with these datasets.

This system-level approach supports more robust monitoring programmes, enabling data to be cross-referenced, validated, and contextualised over time.

Relevance across marine and energy sectors

Although eDNA monitoring is widely associated with ocean science and research programmes, the same principles apply across other marine and energy sectors.

In offshore energy, biodiversity monitoring supports environmental assessment and ongoing operational responsibility. In aquaculture, genetic monitoring can contribute to ecosystem awareness when used alongside imaging and environmental monitoring systems.

Across all sectors, the shared requirement is reliable data collection in harsh and remote marine environments, using monitoring solutions that can be deployed, repeated, and integrated with confidence.

Designing effective eDNA monitoring programmes

Effective eDNA monitoring begins with clearly defined objectives and a realistic understanding of operational conditions. Decisions around sampling frequency, deployment method, and system integration all influence the usefulness of the data collected.

When applied thoughtfully, eDNA monitoring provides a practical way to strengthen marine biodiversity programmes and support informed decision-making in complex marine environments.

eDNA sampling systems for marine deployment
For teams looking to implement repeatable, automated water sampling in operational environments, further information on our eDNA Automated Sampler is available here.