PhytoMOPS: Phytoplankton Morphology and Optical Properties Sensor

Lead Research Organisation: National Oceanography Centre
Department Name: Science and Technology

Abstract

Algae are present in nearly every body of water on the surface of the earth. These microscopic organisms produce roughly half of the oxygen on earth, and are vital to life on the planet. However, algae can also cause significant and expensive damage to their ecosystem, to human health, and to aquaculture stocks when the local environment changes and promotes the rapid growth of a large mass of algae, known as a bloom. Factors such as the concentration of nutrients, temperature, light conditions, and intentional or unintentional interventions by humans or other species all affect the dynamics of algae species and lead to the formation of harmful algal blooms (HABs).

In the aquaculture context, HABs present a major health and economic hazard. Severe human health problems can arise from the consumption of shellfish which have been impacted by blooms of toxin-producing algae. These blooms also cause negative economic impacts on aquaculture through aquaculture stock mortality and through temporary site closures and bans on harvesting due to local algae prevalence. Large-scale mortalities of cultured fish due to algae blooms have been reported across the world and financial losses per large episode can range into the tens of millions of pounds.

Monitoring of phytoplankton and of the toxins they produce has been undertaken in various forms in the UK for some decades but manual sampling and subsequent off-site analysis can be slow to identify areas with upcoming or rapidly-changing problems. Microscopy, the current standard for performing algae counts, requires trained personnel both in collection and particularly in analysis, and imposes a necessary delay as samples need to be preserved and transported to an analytical facility.

The overall objective of this project is to develop new technology to decrease the economic losses and health risks caused by HABs by decreasing the costs of monitoring algae growth in real-time. This technology will complement and address shortcomings in existing monitoring techniques by providing low-cost, high resolution independent data.

The PhytoMOPS technology is based on previous lab-based research demonstrating that algal cells could be sorted, counted, and classified using carefully-designed microfluidic channels combined with low-cost optical readouts. The sorting technique, known as "inertial microfluidics", relies on a carefully-designed channel geometry and flow rate to sort cells by shape and size. In this project, we will design a novel optical measurement section after the cell sorting region, in which the microalgal cells are counted and classfied according to their size, shape, and optical absorption properties. The technology will initially be built and evaluated in the lab where the results will be used to develop analytical methods for interpreting the data.

In order to be able to make measurements directly in the water, we will adapt the National Oceanography Centre's (NOC's) water chemistry sensor platform which has already been used for long-term autonomous measurements in a wide range of harsh and inaccessible environments. We will combine the well-engineering NOC platform (including microfluidic chips, pumps, valves, and control/communication electronics) with the algae sorting technology to produce a deployable system capable of acting as a standalone, low-cost, low-power monitor of algal species dynamics for early warning of HABS formation.

Lastly, this project involves initial field tests of the system. The deployments will be facilitated by two active HAB monitoring organisations who are also providing expert advice throughout the project: the Scottish Assocation for Marine Science and the Agri-Food Bioscience Institute (North Ireland). The system will will be compared directly against manual sampling and existing algal monitoring technology and will be be evaluated for its technical suitability, usability, and long-term potential.

Technical Summary

This project will provide a novel tool for the low-cost, in situ counting and classification of algal cells for early warning of the formation of harmful algal blooms. It will be based on technique called inertial microfluidics, in which particles are manipulated in a microchannel using only forces arising from the system's fluid dynamics (shear, drag, and lift forces, etc.). In a spiral microchannel with Reynolds number in the tens or hundreds, two counter-rotating secondary flows form perpendicular to the main flow. The combination of drag forces from the secondary flow and the shear and wall lift forces move cells into a size-and-shape-dependent equilibrium position in the channel cross section.

Most previous work using inertial microfluidics for particle sorting have used microscopy to measure particle position. A key novelty in PhytoMOPS is the inclusion of a built-in low-cost optical system which will quantify the cells' positions and measure optical absorption, yielding information about morphology and cell pigmentation. This will be achieved with a post-sorting optical interrogation region with two perpendicular sources of light.

The final device will be based on the autonomous microfluidic sensing platform developed by the Ocean Technology & Engineering Group at the NOC. This proven technology uses a suite of components (optics, electronics, pumps, and valves) that have been developed over the last decade and which have been deployed successfully for periods over a year, to full ocean depth, and in harsh conditions including in deep and polar seas and in highly turbid rivers and estuaries. Adapting this technology for the proposed project dramatically reduces risk and increases cost efficiency and will enable the achievement of the project's ambitious goals and impacts.

The project further includes the development of data analysis methods and, lastly, field trials to quantify the suitability of the device for HABs detection.

Planned Impact

This project will deliver a new technology and associated techniques for monitoring phytoplankton. The core impacts will be 1) the provision of a novel low-cost, deployable system for counting and classifying phytoplankton; 2) analytical methods that we will develop; and 3) benchmarked data on phytoplankton populations samples representative of aquaculture applications. While this project is focused on delivering impact to the aquaculture sector, the technology developed will also benefit the regulatory sector and researchers.

In the aquaculture sector significant financial loss can occur from the loss of stocks or closures of sites due to algae blooms. Direct financial benefits will arise from faster, more detailed knowledge of the formation of HABs in aquaculture sites, enabling rapid and informed decisions about sampling and harvesting.

HABs formation has caused significant economic harm around the world through aquaculture losses, negative impacts to tourism and recreational facilities, treating related illnesses, and through the costs of monitoring and managing blooms. HABs cost an estimated EUR589 million (£517 million) per year in the EU and at least USD82 million (£59 million) per year in the US. Individual episodes of HABs formation can have a massive effect: in China a single algae bloom lasting two weeks caused an estimated loss of £4 million to commercial fisheries in 2005. The UK is responsible for around 15% of the EU27 aquaculture production and produces the second-largest amount of aquaculture (by volume) in the EU. UK finfish and shellfish production combined were valued at around £600 million in 2011. A financially strong aquaculture industry with a high level of consumer confidence can continue to contribute to and grow within the UK economy.

Regulatory agencies, governmental bodies, and academic researchers will be impacted by this project through the lower cost of obtaining high-frequency algae population data directly from tield. This data can also be used to inform policy by providing a clearer understanding of the dynamics of HABs formation through the development and validation of better models of phytoplankton growth.

The instrumentation and data industry will benefit from the technology research and development, the intellectual property developed, and the proof of concept of a new technology. The ultimate goal will be to transfer this technology so that it can be manufactured and sold commercially by a company. This we will promote by engaging with companies (see dissemination) and deliver in subsequent projects through licensing, joint venture or spinout. Additional products such as data, information, servicing or measurement services will also be investigated in collaboration with existing and future (see below) industry partners.

Wider societal impact will be achieved by the reduction of human health risks from the consumption of seafood containing biotoxins produced by HABs. Better data on algae growth can improve consumer confidence in the industry.

The technology developed in this project will also yield positive longer-term economic and societal impacts in areas unrelated to aquaculture such as the monitoring of bathing water for HABs formation, the monitoring of ballast water for the presence of invasive species, and the study of algae cultures grown as feedstock or as a fuel source.

Better understanding and mitigation of HABs will yield long-term environmental benefits. The NOCs core water sensor technology measures common nutrient parameters in situ; coupling this existing technology with the PhytoMOPS device would enable larger-scale detailed studies on the effects of nutrients and other biogeochemical parameters on phytoplankton growth.

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