Aspects of the ecology of sandy beaches along Durban's urbanised coastline.

Abstract

Urban sandy beaches are the primary focus of numerous pressures. Among these are the disruption of sand budgets because of an increasing demand for coastal infrastructure, pollution from landward sources, and recreation and the associated stressors such as trampling and off-road vehicles. More recently, climate change and the manifestations thereof, such as sea-level rise and increased storminess have added to the suite of threats to sandy beach ecosystems. Despite being important natural and economic resources these urban systems have not received adequate research attention and, consequently, the management of sandy beaches has been based on ecologically unsustainably principles. The aims of this study were to provide baseline biodiversity information of urban beaches along the Durban coastline, South Africa, as a step toward the application of improved ecological management procedures for metropolitan beach ecosystems. Macro- and meiofaunal communities of 15 representative beaches along the Durban coastline were quantitatively surveyed using standard sandy beach sampling protocols. This study showed that Durban’s beaches, despite being highly urbanised, harbour rich and abundant faunal communities. This is contrary to previous findings that reported a paucity of life on Durban beaches. A total of 23 macrofauna taxa were identified, with the dissipative Battery Beach having highest diversity with 13 macrofaunal species. La Lucia, a reflective beach, had the highest macrofaunal abundance and was the second most diverse beach, thus departing from global trends that report a poor macrofaunal community of reflective beaches. Twenty higher-level meiofauna taxa were recorded in this study and it was found that meiofauna abundance showed a significant and positive relationship with beach width. Because of the coarse taxonomic resolution, meiofauna diversity may likely be much greater than that recorded in this study. The conventional view that sandy beaches are resilient to exploitation was questioned when it was found that meiofauna assemblages were significantly and negatively impacted by stormwater outlets on two of the sampled beaches, possibly through freshwater intrusion or erosional effects. This raises questions regarding the functioning of beach ecosystems, and the services they provide, when faced with anthropogenic stressors that impact faunal communities. This snapshot survey of aspects of the ecology of Durban’s sandy beaches has provided much needed baseline data for this coastline. These data will be used in conjunction with other available data toward the development of a fine scale systematic conservation plan for Durban to enable the prioritisation of conservation and management efforts. The use of these data will also facilitate the development of guidelines for the integrated ecological management of urban sandy beach ecosystems.