What lies beneath

What lies beneath by Johan Wasserman

Beneath the surface of the Knysna Estuary lies a rich diversity of plant and animal life which, until now, has been largely unexplored. Due to recent developments in Remote Operated Underwater Vehicle (ROV) technology, we can now discover what lies beneath our estuary. Using an ROV and Geographic Information System (GIS) software, we plan on creating a map that depicts the subtidal habitats of the Knysna Estuary. Estuarine habitats act as nursery areas for many important fish and invertebrate species, providing them with food and shelter for at least a part of their life cycle. As such, the subtidal habitats of estuaries often host diverse communities. It is important to study the distribution of these habitats for conserving and managing...

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What effect has the blanket of Ulva had on the animals of Leisure Island’s Steenbok Channel shoreline?

What effect has the blanket of Ulva had on the animals of Leisure Island's Steenbok Channel shoreline?

In early 2011, when the Steenbok Channel was clothed in a luxuriant and healthy eelgrass bed, Richard Barnes investigated its invertebrate fauna at a series of nine points (at Kingfisher Creek near its junction with the Ashmead Channel, at its head near the Armstrong Causeway, and at a point halfway between the two, adjacent to the Reserve's Indigenous Garden; and at three points down the shore at each of those three sites - low water neap, mean low water, and low water spring).  Early this year, he sampled those same nine points again but in 2018 in areas of bare mud left after loss of the seagrass.  This was a race against time before the bare mud itself disappeared under...

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Progress on identification of the Moonshine baitworm in Knysna Estuary

Progress on identification of the Moonshine baitworm in Knysna Estuary

The Moonshine worm, a popular bait worm that can be found almost anywhere in the Knysna Estuary, now most likely seems to be an alien species. Our work started owing to a rise in popularity in use of the Moonshine worm as bait among local fishermen. Further investigation showed that these worms were not found within the Knysna Estuary during the 1950’s and 90’s, during extensive ecological surveys. This provides strong circumstantial evidence that these worms moved into the Knysna Estuary some time during the last two decades. The question that arose was whether the worms moved in from another local area, such as a nearby estuary or the ocean floor, or whether it was brought here from elsewhere. (more…)

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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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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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Seahorses on your doorstep

Seahorse research by Knysna Basin Project

A curious, ancient looking creature grasps to its Codium anchor as sampling begins every month at low tide in the canals of Thesen Island Marina. This brownish-green resident is the Knysna seahorse (Hippocampus capensis), the only endangered seahorse in the world. This means as a student, and full-time ocean-lover, it is such an amazing experience to study these animals. We set off just before low tide hits in the Knysna Basin Project boat armed with a pool scoop-net, a scale and calipers. Spending around an hour sifting through scoops of Codium tenue (the free floating green-black macroaglae all over the canals) we eventually find a couple of shy individuals. Transferring the surprised animals into a container of water is step...

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