Scientific research

The Knysna Basin Project is fundamentally scientifically focused and we pride ourselves in the standard and quality of our research.

Our current research projects include the following:

Knysna Seahorse Status (KySS) project

Description

The Knysna Seahorse Status (KySS) project is a long-term project which investigates the ecology and population dynamics of the endangered Knysna seahorse Hippocampus capensis. The first phase of this project (2014 – 2017) established habitat specific seahorse density and distribution within Thesen Islands Marina and the bay regime of the Knysna Estuary. The use of artificial structures by the seahorses and seahorse behaviour were also assessed. Future research will investigate the home-range and the related population dynamics of the Knysna seahorse.

Current research (2018 – 2020) includes the investigation of the home-range, population size and growth rate of the Knysna seahorse using VIFE tags. Within the Knysna estuary, seahorses are marked and monitored within artificial Reno mattress habitats. In the Keurbooms estuary, monthly monitoring of seahorse populations within eel grass beds has commenced, and a similar marking approach will be conducted in this estuary. This research project is in collaboration with Dr Dave Harasti (https://www.dpi.nsw.gov.au/about-us/science-and-research/staff/staff-profiles/david-harasti; http://www.daveharasti.com/)

Period

2014 – Ongoing

Contact details

Louw Claassens kyss.louw@gmail.com

The animal ecology of seagrass beds at Knysna

  • The spatial ecology of seagrass biodiversity
  • The ecology of seagrass / bare-sediment ecotones
  • The ecology of seagrass microgastropods

Description

The Knysna estuarine bay supports the largest seagrass bed in South Africa and at least 25% of the total area of its Cape eelgrass, Zostera (Zosterella) capensis.  Since 2009, Prof. Richard Barnes has been studying the biodiversity of the animal community that this seagrass supports and the way in which it varies across space.  In general it is clear that, as might be expected, biodiversity decreases upstream and from the main estuarine channel into the fringing backwaters, i.e. the numerous saltmarsh creeks and channels; whilst the total number of individual animals often shows the converse distribution.

Some findings, however, have been more unexpected.  At many other localities around the world and indeed within South Africa, seagrass beds support more biodiversity and greater animal abundance than adjacent areas of unvegetated sediment.  This is not the case at Knysna — where bare sediment may even support significantly greater animal numbers — and it seems likely that this is because the Knysna sediments suffer relatively little bioturbation from species like sandprawns.  The reason that seagrass often supports a richer animal community than unvegetated sediment may not be because seagrass is somehow a more favourable habitat (by virtue of more food, more shelter or more protection from predators, for example), but because when present bioturbators can render sand much less favourable than otherwise.

A second unexpected finding has been that within any given seagrass bed the number of species present per unit area is effectively constant, irrespective of the size of the unit-sample concerned.  Further, these observed values of species density are those that would be expected on a null hypothesis that community composition at any given point is simply a random subset of those species in the locally available pool, granted their overall frequencies of occurrence.  Such stochastic composition will only be found where no species is in a position to affect the distribution of any other, i.e. when populations are held below carrying capacity and competitive interactions do not occur, even if niche overlap is almost total.  In turn, this is likely to be brought about by all the juvenile fish that use the Knysna seagrass beds as nursery areas, feeding indiscriminately on anything small in the surface layers of the sediment.

Current work is focusing on the effect that the recent ‘green-plague’ blooms of the alga Ulva are having on seagrass faunal biodiversity.

Period

2001 – present

Contact details

Prof Richard Barnes rsb1001@cam.ac.uk

Benthic processes and the water chemistry of the Knysna Estuary

Description

The proposed research can be divided into three objectives. The first objective will be based on a routine seasonal sampling of the water column of the estuary. The second objective will investigate the nutrient flux from the sediment and seagrass beds at three deployment sites in the upper, middle and lower reaches of the estuary. The last objective will investigate the carbon sequestration of the seagrass Zostera capensis in the Knysna Estuary. Seagrasses provide many ecosystem services among them is the storage of carbon through the process of carbon sequestration. This so called blue carbon is easily quantifiable and has become one the most accepted payments for ecosystem services. Studies on carbon sequestration, storage and emissions in coastal ecosystems are, however, limited and not representative of different species, coastal ecosystems and geographical regions. There is a lack of representation of Africa, South America and Southeast Asia in recent literature (Macreadie et al.; Howard et al. 2014).

Project aims

  1. Determine if there has been a change in the water chemistry of the main channel and the Ashmead Channel.
  2. Determine the flux of nitrogen and phosphorus from the sediment and seagrass beds of the Knysna Estuary.
  3. The role of Zostera capensis (seagrass) in maintaining water quality and delivering ecosystem services such as water purification and carbon sequestration.

Period

2015 – 2018

Contact details

Dr Lucienne Human Lucienne.Human@nmmu.ac.za

Prof Janine Adams Janine.Adams@nmmu.ac.za

Knysna Bait Project

Description

An investigation of bait worm use within the Knysna Estuary including taxonomic clarification of bait worm species.

The aims of this study are therefore to:

  1. Identify the many different worms used as bait and to develop some consensus around their common names. This study will be conducted at various fishing sites in the Western Cape, including Knysna and Sedgefield.
  2. Clarify the identification of the Diopatra species in the Knysna Estuary.
  3. CapeTalk interview with Dr Carol Simon on the Project can be accessed online here.

Period

2015 – present

Contact details

Dr Carol Simon CSIMON@sun.ac.za