JOCARA - Research

RESEARCH

We have worked with Dr. Oliver Wurl before during Jocara Indian Ocean Quest, taking air samples around the Indian Ocean for the study of persistant organic pollutants (or POPs). If you want to read more about this research and see the resulting publications click here.

On this voyage we are again working with Oliver, who now works for the Singapore-Delft Water Alliance (SDWA) at the National University of Singapore. We will collect water samples to study gel particles in the ocean.

What are gel particles?

In the deep ocean, marine snow is a continuous fall down of dead organisms or their fragments, and faecal material from the upper layers of the water column. Marine snow provides food to organisms habiting the deep ocean, which is poor on own food sources.

The origin of marine snow lies in activities of algae within the productive upper surface waters of the ocean. Consequently, the prevalence of marine snow changes with seasonal fluctuations of the abundance of algae and ocean currents. Thus marine snow is heavier in spring, and the reproductive cycles of some deep-sea animals are synchronized to take advantage of this.

The clump- or string-like "snowflakes" are aggregates of dead organism and faecal materials held together by a sugary mucus, transparent exopolymer particles (TEPs). The sticky gel-like TEPs act like glue among the other particles enhancing the formation of aggregations heavy enough to sink into the darkness of the ocean. Natural sugar compounds exuded as waste products by bacteria and algae are the original material for the formation of TEP. TEPs are the most abundant form of marine gel particles.

In the box below is a write-up of the research project.

Gel Particles in the Ocean

Transparent exopolymer particles (TEPs) are the most ubiquitous and abundant gel particles in the oceans. TEPs are mainly formed by coagulation of dissolved carbohydrates, which are released by phytoplankton communities. Due to their surface-active nature and stickiness, TEPs exhibit the characteristics of gel-particles. They have an essential impact on the formation of aggregates as microhabitats colonized by bacteria, which find rich substrates in the otherwise poor water column (Fig.1). Therefore TEPs play a significant role in the biogeochemical cycling of elements, such as nutrients and trace metals. Their high abundance and stickiness enhance and even facilitate the aggregation of solid, non-sticky particles and promote therefore the sedimentation rate of particles. Due to the high carbon content of TEPs, such sinking aggregates accelerate the carbon export to the deep ocean and have an important role in the marine carbon cycle and carbon sequestration. However recent studies suggested that high TEP contents in diatom aggregates can lead to upward flux through their buoyancy and can act as a vehicle in transporting particle-reactive chemicals towards the surface of the ocean.

In this research project, water samples are collected during Jocara's voyage to New Zealand and analyzed on TEP, carbohydrates and chlorophyll-a, a proxy for the abundance of phytoplankton. TEPs collected on membrane filters are stained with a blue dye to make them visible (Fig.1), which is then dissolved in acid for quantitative colorimetric analysis. The samples are drawn from Jocara’s modified seawater water intake in the hull. The data will be used to further optimize a mathematical model to estimate the production rates of TEP in the oceans. The model consist data from different regions of the world, but the data collected during Jocara's voyage are of particular importance as oceanic data are rare, but essential for the verification of the model. With the model, scientists may improve estimations of the particle fluxes down to the deep ocean and therefore the extent of carbon sequestration in sediments.

Figure 1: Stained TEPs and aggregations with solid particles

We will be collecting 18 water samples along the route. On the map below you can see the sample sites.

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