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You are here: Home eNewsletter Archives 2007 August 2007 Monitoring our oceans to detect early-warning signals of climate change

Monitoring our oceans to detect early-warning signals of climate change

- By Dr Albrecht Götz, SAEON Elwandle Node

The SAEON Elwandle Node is involved in two ongoing monitoring projects of inshore marine resources at Woody Cape Nature Reserve and the Tsitsikamma National Park.

More than 13 000 hours of standardized shore-angling at these two target sites yielded a data set spanning 16 years. Valuable insights into the temporal variability of marine resources were gained from this data during analysis, and publications are currently in progress. Since 2007, observation scientists have been monitoring the intertidal environment of both target sites by means of digital photography quadrates and tidal pool sampling using rotenone, a broad-spectrum piscicide.

There are two projects that target the offshore environment. In Algoa Bay, in a project that started at the beginning of 2006, information is being collected around Bird Island and the St Croix Island group. A new offshore monitoring site was established in the Tsitsikamma National Park in December 2006. Here, an array of permanent automated systems, monitoring climate and oceanographic conditions, is being maintained.

A variety of survey types are conducted biannually at both target sites using standardized methods. Digital underwater photography quadrates and specimen collections are carried out during SCUBA surveys to build up a photographic inventory of invertebrates and determine inter-annual changes in their abundance. Due to an inherently high variability between observers, demersal fish (fish that dwell near the bottom of the ocean) are identified and counted according to strict protocols using SCUBA. To further eliminate bias, digital underwater video sampling is conducted at the same sites. Footage can be stored and analyzed comparatively in order to establish a long-term benchmark and to put observer bias into perspective.

In addition, controlled angling surveys are conducted from ski-boats. These surveys aim to back up long-term trends identified during underwater visual census and allow researchers to gain valuable insights into the state and levels of vulnerability of reef fish species to exploitation by the recreational and commercial fishery sectors.

Collecting the necessary biological data in large Marine Protected Areas will enable oceanographic researchers to link possible changes in biota (plant and animal life) with long-term climate change without complicating any causal relationships by superimposed anthropogenic impacts (exploitation and habitat destruction).

Such information is necessary for early-warning systems which can reduce the social and economic costs caused by changes in marine resources.

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Dr Albrecht Götz is a post-doctoral fellow who currently leads the SAEON Elwandle Node's marine park monitoring.

A researcher gathers underwater digital footage in Tsitsikamma. In the inshore environment, habitat information can be collected using snorkeling gear. The foraging behaviour of many inshore fish is controlled by tidal movement and availability of invertebrate prey organisms.

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Research fishing and diving surveys are conducted in the marine part of the Tsitsikamma National Park. The predominantly rocky coastline is interspersed with sandy beaches.

Core members of the research fishing team at the Tsitsikamma coast have been ‘fishing for data’ for more than 12 years.

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A black musselcracker carries a spaghetti tag (yellow) for long-term identification. Recaptures give insights into movement behaviour and growth rates of exploited linefish species. Black musselcracker are very resident; some specimens have been recaptured three times at the same spot having stayed in the park for more than five years. Such information is crucial in fishery management and conservation using marine protected areas (MPAs).

A 'bird's-eye view' on Bird Island from the lighthouse. Researchers and game rangers from South African National Parks share the island with about 200 000 Cape gannets and 60 000 African penguins . The Bird Island Group is surrounded by extensive and shallow rocky reefs.

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Aerial surveys are ideal to monitor fishing activities at sea and along the shore. The Alexandria dunefields of Algoa Bay shown in the picture are of great importance to the sandy beach-surfzone ecosystem and beyond as they maintain water exchange through an aquifer.

The island St Croix is located only a few kilometres off the Coega Harbour development. Despite being a barren rock it hosts the largest colony of African penguins. Reefs in this area are restricted to the immediate vicinity of the island.

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A researcher monitors invertebrates using a digital underwater camera. Pictures are taken at the same distance from the reef to keep areas comparable for later quantitative analysis on the computer.

Counting fish underwater can be difficult when superabundant species such as Fransmadam are present. As a result, the precision of the diving counts as compared to controlled fishing is often lower. However, diving counts are less selective than fishing and therefore more representative of the actual fish community.

About Dr Albrecht Götz

Dr Albrecht Götz is a post-doctoral fellow who currently leads the SAEON Elwandle Node's marine park monitoring.

Dr Götz gained extensive experience in North Sea ecology (while studying at a German University), in the Caribbean (one year marine field research in Trinidad for his MSc), and locally, where he has spent four years studying the marine ecosystem in the Goukamma Marine Protected Area.

He has published scientific papers and presented at local and international Marine Science Symposia. With completion of his PhD in South Africa, he has produced ground-breaking research in that he was the first to unequivocally demonstrate the broad ecological impacts of linefishing on the marine offshore environment.

Since completion of his PhD he has been involved in a number of long-term monitoring programmes at Woody Cape, Tsitsikamma National Park and Algoa Bay in collaboration with the Department of Ichthyology and Fisheries Science, EnviroFish Africa, the South African National Parks (SANParks) and the South African Institute for Aquatic Biodiversity (SAIAB).



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