eNews

#03 2024

Cross-nodal collaboration – Egagasini and Elwandle Nodes set out to investigate the role of the Agulhas Current in the coastal environment

By Jordan Van Stavel, Tamaryn Morris, Riesna R. Audh, Shaun Deyzel, Jethan d’Hotman and Mfundo Bizani, NRF-SAEON

The Egagasini and Elwandle Nodes have joined forces on a new project of the African Coelacanth Ecosystem Programme (ACEP) to investigate the role of the Agulhas Current in the coastal environment. The project is headed by Dr Tamaryn Morris from the Egagasini Node and the South African Polar Research Infrastructure (SAPRI), in collaboration with the Elwandle Node’s Professor Tommy Bornman, Dr Shaun Deyzel and Jethan d’Hotman of the Shallow Marine Coastal Research Infrastructure (SMCRI).

For the first survey (detailed below), the project was supported by Drs Phumlile Cotiyane-Pondo and Mfundo Bizani, Sifiso Mbambo, Jordan Van Stavel and Riesna R. Audh.

Map showing the transect (green dots) sampled and deployment locations of the Sailbuoy and Seatrec Argo float during the ACEP survey out of Algoa Bay (inset). Bathymetry is indicated by the dotted black lines and the temperature scale bar shown at the bottom (Source: Riesna R. Audh)

CTD instrument being prepared for deployment by the Elwandle Node’s Shaun Deyzel (left) and Jethan d’Hotman (Photo: Koos Smith)

Aim and impacts 

The project was initiated to explore a range of processes and physical anomalies, including meanders, eddies and shelf-edge upwelling occurring in the Agulhas Current which impacts the near-shore and shelf region, particularly Algoa Bay, Gqeberha.

In addition, the work is intended to establish a robust monitoring programme comprising physical, biogeochemical and planktonic components of the southern Agulhas Current through regular boat-based surveys, to gain deeper insights into these phenomena. These anomalies have a significant impact on the adjacent coastal region and Algoa Bay, affecting coastal ecosystems, infrastructure and the livelihoods of local communities.

The new project strives to enhance the collective understanding of biodiversity and productivity in the region while also fostering societal benefits, particularly in areas such as fisheries, tourism, port operations and shipping practices. The project endeavours to establish stronger connections with policymakers and stakeholders through peer-reviewed publications and widespread science communication.

Moreover, the project offers a platform for training postgraduate students across diverse disciplines, encompassing physical oceanography, ocean modelling, ecosystem studies and biogeochemistry, as well as providing technical expertise in sea-going activities, instrument maintenance and data management.

The Sailbuoy after a successful deployment on Station 5 (Photo: Tamaryn Morris)

Bongo net retrieval by Shaun Deyzel (left) and Mfundo Bizani (Photo: Tamaryn Morris)

The first survey 

In May this year, a successful first survey was conducted by a team of eight SAEON staff members on board the RV Observer. The team sampled a transect out of Algoa Bay (see map of stations), targeting the progression of two cyclonic (cold water) anomalies travelling down the east coast of South Africa. Despite gloomy weather conditions and the wrath of seasickness on board the 15-metre vessel, the team radiated enthusiasm for science and conquered the day!

A Conductivity, Temperature and Depth (CTD) instrument was deployed along the transect, collecting an assortment of discrete oceanographic and environmental data and samples. Two autonomous instruments were deployed at two individual stations along the way – a Seatrec Argo float as part of Project FIND and a surface Sailbuoy. Surface waters increased in temperature from Station 1 outwards towards Station 10, with seawater clarity (visibility) increasing with distance offshore.

Zooplankton image taken in the laboratory of a copepod species, Calanoida (order) (Image: Mfundo Bizani)

Zooplankton image taken in the laboratory of a salp species, Salpida (order); Thalia democratica (Image: Mfundo Bizani)

Zooplankton image taken in the laboratory of a squid larva (Image: Mfundo Bizani)

Vertical and obliquely towed bongo nets were used for the collection of zooplankton samples, from which interesting observations were made on board. Most notably, samples were thick with a green slime, not expected to have occurred at such densities beyond Algoa Bay, with nets completely clogged of samples and some very interesting copepod and jellyfish specimens.

A highly productive survey, perhaps linking to the passing cyclonic anomalies, which analyses will hopefully soon reveal. Several species of marine fauna joined in along the way, including seals, dolphins, whales and various seabirds.

Riesna R. Audh collecting samples for microbial analyses on board (Photo: Koos Smith)

On a lighter note – graph of the emotional rollercoaster endured by some team members during the survey (Source: Riesna R. Audh)