Generators hum loudly in the background as a tour boat bobs past a towering vessel filled with ship fuel, anchored in Algoa Bay, a stone's throw away from the world's largest breeding colony of African penguins.
Mid-way along the Europe-Asia sea route, the bay's deep-water port was an obvious choice for South Africa's first offshore bunkering operation.
Since 2016, mostly cargo ships have pulled in for ship-to-ship (STS) refuelling, allowing them to carry more freight, bypass port fees and save time.
But conservationists, ecotour operators and nature lovers are alarmed about the long-term impact in a marine biodiversity hotspot and major foreign tourist magnet.
A colony of penguins is seen on St. Croix island in Algoa Bay outside Port Elizabeth.
They claim the bunkering takes place too close to foraging and breeding grounds, disrupting the ecosystem and exposing sea animals to oil spills.
The risk has been highlighted by the catastrophic oil spill which began earlier this month into a protected marine park off the pristine coastline of Mauritius, after a bulk carrier ran aground on July 25.
With the main storage tanker in Algoa Bay able to hold 100,000 metric tons of fuel, opponents fear a potentially massive leak.
In two minor spills, in 2017 and 2019, rangers rescued dozens of oil-tarred penguins.
Scientists are also studying whether the noise, pollution and increased ship traffic could affect the marine animals.
Volunteers feed baby African penguins rescued from Algoa Bay.
Follow the sardines
Algoa Bay -- an inlet off the city of Port Elizabeth in the Eastern Cape province -- is home to myriad species of seabirds, including just under half the global population of African penguins, classed as endangered by the International Union for Conservation of Nature.
The world's largest group of bottlenose dolphins was recorded in the bay in 2018, according to a report last year by the Port Elizabeth-based Nelson Mandela University.
The site is also on the path of an annual sardine run, touted as one of the planet's most spectacular marine events.
Sat on a key trade route, sea traffic has increased as a result of the fuelling hub, conservationists said.
A volunteer moves a baby African penguin rescued from Algoa Bay at the SANCCOB Seabird rehabilitation centre.
Argyros stressed that bunkering was a "safe operation" in a "very regulated industry".
When "two vessels are tied together they become like one entity," he told AFP.
Sludge-covered penguins
About 100 oiled penguins were recovered from last year's spill.
Seabird scientist Lorien Pichegru said that, while damage from the incident had been limited, bunkering posed yet another threat to a species whose global population fell below 40,000 last year.
READ MORE
Rare albino penguin makes debut at Polish zoo
Emperor penguin colony in Antarctic disappearing
Eventually they die of "starvation and cold", plus oiled adults tend to abandon their eggs and chicks, she added.
In attempting to clean themselves, the birds also ingest toxins shown to damage their internal organs and breeding capacity.
African penguins, distinct by their bray-like call and black horseshoe marking across their chest, only breed in South Africa and Namibia but are found in Mozambique too.
Over three decades, their numbers have fallen by more than 60 percent due to climate change, oil spills, human activity, overfishing and habitat destruction, experts say.
In Algoa Bay, the population has also fallen sharply -- from 10,900 breeding pairs in 2015, to 6,100 in 2019, according to figures from South Africa's Environmental Affairs department.