Water quality monitoring in the Knysna estuary

KEMP Knysna Basin Project

The winter of 2017 was somewhat drawn out, cold and occasionally wet which fortunately did not interfere with the necessary sampling of the estuary water column in the vicinity of Thesen Jetty.  At this site KEMP, a part of the overall Knysna Basin Project had set up a Hach Ott multiparameter sonde well below the surface at low water and delivered real time changes in dissolved oxygen acidity (pH), water levels, and measured chla fluorometrically (digitally). (more…)

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Sea Star Sundays

The Spiny sea star Marthasterias glacialis

The Spiny sea star Marthasterias glacialis is widely distributed. However, the South African Marthasterias population has been reclassified as Marthasterias africana. These critters were easy to spot with their vibrant orange and purple colourings and their arms covered in small spines. The spread of M. africana within The Knysna Estuary is suspected to be because of the invasive mussel species Mytilus galloprovincialis, as it is the sea star’s main source of food. (more…)

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Seahorses on your doorstep: an update on what we found!

A female Knysna seahorse

Codium tenue, an aquatic plant, has been found to be a suitable habitat for the Knysna seahorse within Thesen Islands Marina. This project aimed to assess and compare the density and sex structure of the Knysna seahorse within this habitat. Results were also compared to the 2016 assessment of this population. The study ran from March to August 2017 (6 months) at three sites within the marina and the density of seahorses was found to be similar across sites as well as over the six-month period. The overall average density of Hippocampus capensis was found to be 0.32 ± 0.02 seahorses per kilogram of Codium tenue. This density was found to be similar to surveys from 2016. (more…)

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Mediterranean Mussel

Mediterranean mussel (Mytilus galloprovincialis)

My name is James Radloff and I am currently doing my MSc in Marine Biology at Rhodes University. I am working on one of the most alien invasive marine species along the South African coastline, the Mediterranean mussel - Mytilus galloprovincialis. The Mediterranean mussel has the characteristics of a successful invasive species, having a high tolerance to salinity and desiccation, fast growth rate, high reproductive output, they are better competitors than native mussel species and have relatively few predators. Because of these successful characteristics this species has been able to spread extensively along the coasts of South Africa. (more…)

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Jaap Se Bay

Jaap Se Bay at Brenton on Sea is a ‘secret’ cove – around the corner from Castle Rock but tricky to find and a long climb down. But a climb well worth doing as Frances and Peter Smith found when they were introduced to it by Dave and Hannah Edge (Brenton Blue butterfly). At low tide there are rocks after rocks covered in huge brown mussels (Perna perna) and others closely packed with redbait (Pyura stolonifera ) – amazing sights. Sheltering in with the redbait were brightly coloured sponges and sea squirts. Around the bases of the rocks were large sandy anemones that close up into sand covered doughnuts and multi-coloured sea anemones including the striking purple knobbly anemone (Bunodosoma...

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The Truncated Mangrove Snail

The Truncated Mangrove Snail

Each month we feature a new species. This month we discuss Cerithidea decollata (Linnaeus, 1767) (text and photograph by Alan Hodgson). This marine snail is commonly known as the Truncated Mangrove Snail. It has a wide subtropical to tropical distribution in the West Indian Ocean, but in South Africa extends south into the Western Cape. As its common name suggests it mainly lives in mangroves, but south of East London it can be found in the salt marshes of estuaries. (more…)

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An Artful Waste Challenge

Artful Waste Challenge by Knysna Basin Project

The Knysna Basin Project launched the Artful Waste Challenge during last year’s Knysna Oyster Festival. What does this challenge entail, you might ask? First, an estuary clean-up takes place, where teams walk along the Knysna estuary and collect litter (or shall I say art materials) lying around. Once this is done, teams use the litter collected to find their artistic side and create pieces of art with an environmental message. The teams with the best artworks are then rewarded with awesome prizes from our sponsors (Metelerkamps, Ocean Odyssey and Knysna Elephant Park). (more…)

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Starfish Sundays

Spiny starfish by Knysna Basin Project

I am a student at Rhodes University currently doing my honours in Marine Biology. I completed my undergrad at UJ in Zoology and Human Physiology and I must say, Marine Biology is possibly one of the most soul filling subjects you could ever do in my opinion. I am working with the size, biomass, consumption rates and population distribution of the spiny starfish (Marthasterias glacialis). Not to mention that we are also looking if a relationship exists among M. glacialis and the invasive Mediterranean mussel species (Mytilus galloprovicialis). A mouthful I know, but it is one heck of an experience. (more…)

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A Shaggy Tale

The shaggy sea hare by Knysna Basin Project

It’s coming into low tide and in the clear water it’s easy to see the fascinating creatures that live in this Eden under the water. A strange brownish-red ball of shaggy tassels can be found sitting on clumps of Codium tenue, a macroaglae species, the shaggy sea hare (Bursatella leachii).  These odd gastropods have no shell and are named for the two extended ear-like structures on their heads, making them look like the terrestrial hares. They are about 10cm in length and munch on alga or decaying matter. If disturbed they will produce a bright purple ink to deter any predator from eating them. As they prefer low intensity water flow, the canals of Thesen Islands Marina provide a perfect...

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The Green Bubble Shell

Green Bubble Shell

Each month we feature a new species. This month we discuss Haminoea alfredensis Bartsch, 1915 (text by Alan Hodgson, photograph by Peter Smith). This opisthobranch gastropod mollusc (Order Cephalaspidea) is commonly known as the Green Bubble Shell and is endemic to South Africa. It is found all around the South African coastline and is very common in estuaries especially on sea grasses such as the eelgrass Zostera capensis (as shown in the image). (more…)

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