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 estuarine systems.
Figure 1: Johan Wasserman testing out the Trident ROV in the canals of Thesen Islands Marina.
The Knysna Estuary is the most important estuary in South Africa for biodiversity conservation and is home to rare species like the Knysna seahorse and the Knysna goby. Despite this, the subtidal habitats have not yet been fully assessed. For this reason, we are aiming to produce a map of the subtidal habitats which can be used as a baseline for examining habitat changes over time.
Figure 2: Strap grass (Caulerpa filliformis) is one of the habitat types found in the Knysna estuary.
Due to the generally turbid nature of estuaries, mapping with standard satellite imagery is not viable. The recent advancements of ROVs provide an exciting opportunity to observe an unexplored world. For this project, we are using a Trident ROV, the latest product from OpenROV. OpenROV is a fascinating open source company and community which is constantly innovating new prospects for their ROVs and opening many doors for underwater exploration. With this project, we are attempting to develop a quick and accurate method for mapping subtidal habitats.
Figure 3: The view as seen from the ROV – Red algae (Asparagopsis taxiformis) and eel grass (Zostera capensis).
Ideally, we will produce an accurate GIS map of the Knysna Estuary which shows the distribution of subtidal habitats. This map will be useful for decision making in conservation and management by authorities, and also provide information for future research projects. Additionally, we are aiming to develop a quick and accurate method for mapping submerged habitats in estuaries. If it is viable, this method could be used in other estuaries as a tool for conserving these habitats.
Post written by Johan Wasserman
