Ricky H. Taylor

Ecology and Conservation of Estuarine Ecosystems: Lake St. Lucia as a Global Model

List of contributors Foreword Alan Whitfield Preface 1. South Africas first World Heritage Site Roger N. Porter 2. Management history Ricky H. Taylor 3. Geological history Greg A. Botha, Sylvi Haldorsen and Naomi Porat 4. The marine environment Allan D. Connell and Sean N. Porter 5. Catchment hydrology Derek D. Stretch and Andrew Z. Maro 6. The Wetlands William N. Ellery, Suzanne E. Grenfell, Michael C. Grenfell, Marc S. Humphries and Kirsten B. Barnes 7. Estuary and lake hydrodynamics Derek D. Stretch, Clint P. Chrystal, Robynne A. Chrystal, Christopher Maine and Justin J. Pringle 8. Groundwater hydrology Bruce E. Kelbe, Ricky H. Taylor and Sylvi Haldorsen 9. Physico-chemical environment Renzo Perissinotto, Nicola K. Carrasco and Ricky H. Taylor 10. Microalgae Renzo Perissinotto, Guy C. Bate and David G. Muir 11. Macrophytes Janine B. Adams, Sibulele Nondoda and Ricky H. Taylor 12. Benthic invertebrates Deena Pillay, Sarah J. Bownes and Holly A. Nel 13. Zooplankton Nicola K. Carrasco, Renzo Perissinotto and Hendrik L. Jerling 14. Penaeid prawns Anthony T. Forbes and Nicolette T. Forbes 15. Fish and fisheries Digby Cyrus 16. Birds Jane Turpie, Ricky H. Taylor, Meyrick Bowker and Caroline Fox 17. Crocodiles Xander Combrink, Jonathan Warner and Colleen T. Downs 18. Hippopotamuses Ricky H. Taylor 19. Alien and invasive species Nelson A. F. Miranda and Janine B. Adams 20. Food webs and ecosystem functioning Ursula M. Scharler and Fiona C. MacKay 21. Climate change impacts Andrew A. Mather, Derek D. Stretch and Andrew Z. Maro References Appendix: web page database, 1900-2010 Nuette Gordon Index.

Relinkage of the Mfolozi River to the St. Lucia estuarine system – urgent imperative for the long-term management of a Ramsar and World Heritage Site

The St. Lucia Estuary was separated from the Mfolozi River in the early 1950s following canalisation of the Mfolozi floodplain swamp that resulted in the deposition of large amounts of sediment in the estuary. A separate Mfolozi River mouth has been maintained artificially since then and the deleterious consequences in terms of freshwater supply to the St. Lucia system are now becoming fully apparent, especially following the latest drought. Fish and penaeid prawn stocks in Lake St. Lucia have collapsed and the loss of this major southern African estuarine nursery area for these faunal components has had a significant impact on fish and prawn catches in adjacent coastal waters. It is therefore imperative that a re-linkage of the Mfolozi River to the St. Lucia system occurs so that the health and conservation status of the St. Lucia ecosystem, which is a Ramsar and World Heritage Site, can be assured. This review of the major findings presented at a recent scientific workshop explores the need for, and consequences of, a reconnection between the Mfolozi River and St. Lucia Estuary and makes some preliminary suggestions towards the achievement of that goal. Foremost amongst these proposals is to use the subsiding Mfolozi floodplain as a sink for excess sediment carried by the Mfolozi River before it enters the St. Lucia system, as well as various strategies in terms of reconnection options.

Evidence of a Declining Nile Crocodile (Crocodylus niloticus) Population at Lake Sibaya, South Africa

Formerly widespread throughout the waterbodies of eastern South Africa, viable Nile crocodile (Crocodylus niloticus) populations are now restricted to three disjunct protected areas in KwaZulu-Natal (KZN), Mpumalanga and Limpopo. Growing evidence suggests that protected populations are declining, including the breeding C. niloticus population at Lake Sibaya in KZN. Aerial surveys were conducted at Lake Sibaya from 2003–2004 and 2007–2009, spotlight counts in 2003 and intensive nesting surveys in 2003 and 2004. Seven adults were counted during the 2009 aerial survey; an 89% decrease from the 1985 count (62 adults) and a decline of 95–98% of the estimated 1970 adult population. Likewise, in 1970 30 nests were recorded, compared to three nests in 2003 and no recorded nests in 2004. The non-hatchling population in 2003 was estimated at 48 individuals and decreased to an estimated eight in 2009. The neighbouring community perceives crocodiles as a threat to their lives and livestock, and increasing human pressures on C. niloticus in the area will probably ensure that the population will not recover naturally. Unless crocodiles are perceived as a useful or somehow beneficial natural resource by the surrounding community, the species faces possible extirpation from Lake Sibaya in the future.

Temporal Variations in the Diversity of True Crabs (Crustacea: Brachyura) in the St Lucia Estuary, South Africa

ABSTRACT The St Lucia Estuary is part of the iSimangaliso Wetland Park, which is a UNESCO World Heritage Site. It is characterised by instability and experiences ongoing anthropomorphic change, both of which have a significant impact on the biodiversity of the estuary and surrounding area. Brachyurans (true crabs) play an integral role in the functioning and maintenance of this ecosystem. They are a food source for organisms at higher trophic levels, maintain nutrient balance, regulate trophic flow and aerate dense mud through the construction of burrows. However, since the early survey of Millard and Broekhuysen (1970), no study has focussed on this taxon, the identification of which is confounded by the existence of cryptic and pseudocryptic species. This study provides a census of the brachyuran species inhabiting the St Lucia estuarine lake, highlighting the changes in diversity that have occurred in this region between 1948 and 2012. A total of thirty species were found in the area during this period, five of which have not been recorded in previous literature. The extent to which regional endemic species, such as Paratylodiplax blephariskios, have been affected by the dynamics of the system is discussed. The distribution and abundance of three key species, namely P. blephariskios, Neosarmatium africanum and Hymenosoma projectum, are outlined; and possible reasons for observed changes are discussed. Future scenarios regarding the state of the estuary mouth and the stability of physico-chemical variables are also considered. Lastly, an annotated checklist illustrated by photographs is included to aid in identification of species for research and management purposes.

Diversity of bivalve molluscs in the St Lucia Estuary, with an annotated and illustrated checklist

ABSTRACT Bivalves play a vital role in estuarine ecosystems, but are vulnerable to rapid or prolonged changes in the physico-chemical environment. The St Lucia estuarine lake exhibits sub-decadal changes from wet to dry periods, resulting in fluctuating physico-chemical conditions. This paper represents a census of the diversity of bivalve molluscs in this estuary, emphasising changes associated with climate-induced hydrological states. Twenty-four bivalve species were recorded within St Lucia between 1925 and 2011. Twelve that had not been reported previously from St Lucia in the literature were encountered during the present study. These are Anadara natalensis, Anomia achaeus, Arcuatula capensis, Chambardia wahlbergi, Corbicula fluminalis, Dendostrea sandvichensis, Fulvia fragilis, Mactra cuneata, Martesia striata, Meretrix meretrix, Saccostrea forskahlii and Tellina s.l. bertini. Single shells of another two previously unrecorded species, Anodontia edentula and Timoclea lavrani, were also found, although these may have been introduced dead from the ocean through tidal exchange. Meretrix meretrix, an unexpected yet abundant species, represents a new record for South African waters, but the timing and mode of its introduction into the estuary remain unresolved. Extremely large numbers (>100 ind.m-2)of dead specimens of Barnea manilensis were observed in 2011 along the western shoreline of the estuarine lake, which indicates that the species was a major role-player in the settling of suspended silt within the system. Currently, this function appears to be fulfilled only by Solen cylindraceus. Apart from this species, Brachidontes virgiliae, Dosinia hepatica, Macomopsis moluccensis, Salmacoma litoralis and an undescribed Tellina sp. (reported here as T. cf. rousi) are the only bivalves that were found alive in St Lucia during the latest survey, in March 2011.

Salinity tolerance of the bivalve Solen cylindraceus (Hanley, 1843) (Mollusca: Euheterodonta : Solenidae) in the St Lucia Estuary

ABSTRACT Solen cylindraceus (Hanley, 1843) is an infaunal bivalve that in the St Lucia Estuary is currently restricted to the southern part of its South Lake, having disappeared from the northern reaches due to persisting hypersaline conditions (>70 ‰) and air exposure at low water levels. The system experiences marked fluctuations in salinity due to quasi-decadal changes from wet to dry periods. In this study, the salinity tolerance of S. cylindraceus is determined using both shock and gradual change tests. Animals were collected at Catalina Bay (eastern shores of South Lake) and acclimated under laboratory conditions to naturally occurring salinities of 50 ‰ and 45 ‰ for the shock and gradual test, respectively. Mortalities were recorded for animals exposed to a sudden change in salinity, using eight different treatments ranging from 0 to 80 ‰. The second test involved exposing bivalves to a gradual change in salinity, using eight different treatments from 0 to 85 ‰. In the shock test, the lower salinity tolerance limit for S. cylindraceus was 30 ‰ and the upper 60 ‰, while in the gradual test, these limits were 15 and 65 ‰, respectively. The time it took for 50 % of animals to die increased from the shock to the gradual test for 10, 20 and 70 ‰, and decreased for 0 and 80 ‰. This knowledge may be useful towards predicting major crises in the S. cylindraceus populations, as drought and flood events alternate in the region. Major losses will be expected when salinities exceed 65 ‰ during dry phases or drop below 15 ‰ during flood events.

In situ Growth Rate of Solen cylindraceus (Mollusca: Euheterodonta: Solenidae) in the St Lucia Estuarine Lake, South Africa

Solen cylindraceus, an infaunal bivalve, can reach a maximum length of 95 mm. However, in the St Lucia estuarine system specimens are seldom larger than 55 mm. Thus, the primary aim of this study was to investigate the growth rate and morphometrics of S. cylindraceus in St Lucia. Growth lines of this species are too indistinct and irregular to be of any use. This study, therefore, adopted a more direct method of monitoring the shell length of individuals, by caging them in situ. Shell measurements were taken from the individuals in cages and the surrounding environment at monthly intervals for one year. Thereafter, salinities decreased below their tolerance range and the experiment was terminated. Caged and uncaged animals had a shell length of 31.0 ± 4.5 and 31.7 ± 2.3 mm after a year of growth, respectively. An overall growth rate of 0.049 ± 0.059 mm/d was derived for the caged animals. In conclusion, first year growth rates appeared lower than previously recorded for S. cylindraceus. Additionally, it appears that animals are unable to survive in the prevailing harsh environment of St Lucia to reach maximum size.

Ecology and Conservation of Estuarine Ecosystems: Taxonomic index

List of contributors Foreword Alan Whitfield Preface 1. South Africas first World Heritage Site Roger N. Porter 2. Management history Ricky H. Taylor 3. Geological history Greg A. Botha, Sylvi Haldorsen and Naomi Porat 4. The marine environment Allan D. Connell and Sean N. Porter 5. Catchment hydrology Derek D. Stretch and Andrew Z. Maro 6. The Wetlands William N. Ellery, Suzanne E. Grenfell, Michael C. Grenfell, Marc S. Humphries and Kirsten B. Barnes 7. Estuary and lake hydrodynamics Derek D. Stretch, Clint P. Chrystal, Robynne A. Chrystal, Christopher Maine and Justin J. Pringle 8. Groundwater hydrology Bruce E. Kelbe, Ricky H. Taylor and Sylvi Haldorsen 9. Physico-chemical environment Renzo Perissinotto, Nicola K. Carrasco and Ricky H. Taylor 10. Microalgae Renzo Perissinotto, Guy C. Bate and David G. Muir 11. Macrophytes Janine B. Adams, Sibulele Nondoda and Ricky H. Taylor 12. Benthic invertebrates Deena Pillay, Sarah J. Bownes and Holly A. Nel 13. Zooplankton Nicola K. Carrasco, Renzo Perissinotto and Hendrik L. Jerling 14. Penaeid prawns Anthony T. Forbes and Nicolette T. Forbes 15. Fish and fisheries Digby Cyrus 16. Birds Jane Turpie, Ricky H. Taylor, Meyrick Bowker and Caroline Fox 17. Crocodiles Xander Combrink, Jonathan Warner and Colleen T. Downs 18. Hippopotamuses Ricky H. Taylor 19. Alien and invasive species Nelson A. F. Miranda and Janine B. Adams 20. Food webs and ecosystem functioning Ursula M. Scharler and Fiona C. MacKay 21. Climate change impacts Andrew A. Mather, Derek D. Stretch and Andrew Z. Maro References Appendix: web page database, 1900-2010 Nuette Gordon Index.

Ecology and Conservation of Estuarine Ecosystems: List of contributors

List of contributors Foreword Alan Whitfield Preface 1. South Africas first World Heritage Site Roger N. Porter 2. Management history Ricky H. Taylor 3. Geological history Greg A. Botha, Sylvi Haldorsen and Naomi Porat 4. The marine environment Allan D. Connell and Sean N. Porter 5. Catchment hydrology Derek D. Stretch and Andrew Z. Maro 6. The Wetlands William N. Ellery, Suzanne E. Grenfell, Michael C. Grenfell, Marc S. Humphries and Kirsten B. Barnes 7. Estuary and lake hydrodynamics Derek D. Stretch, Clint P. Chrystal, Robynne A. Chrystal, Christopher Maine and Justin J. Pringle 8. Groundwater hydrology Bruce E. Kelbe, Ricky H. Taylor and Sylvi Haldorsen 9. Physico-chemical environment Renzo Perissinotto, Nicola K. Carrasco and Ricky H. Taylor 10. Microalgae Renzo Perissinotto, Guy C. Bate and David G. Muir 11. Macrophytes Janine B. Adams, Sibulele Nondoda and Ricky H. Taylor 12. Benthic invertebrates Deena Pillay, Sarah J. Bownes and Holly A. Nel 13. Zooplankton Nicola K. Carrasco, Renzo Perissinotto and Hendrik L. Jerling 14. Penaeid prawns Anthony T. Forbes and Nicolette T. Forbes 15. Fish and fisheries Digby Cyrus 16. Birds Jane Turpie, Ricky H. Taylor, Meyrick Bowker and Caroline Fox 17. Crocodiles Xander Combrink, Jonathan Warner and Colleen T. Downs 18. Hippopotamuses Ricky H. Taylor 19. Alien and invasive species Nelson A. F. Miranda and Janine B. Adams 20. Food webs and ecosystem functioning Ursula M. Scharler and Fiona C. MacKay 21. Climate change impacts Andrew A. Mather, Derek D. Stretch and Andrew Z. Maro References Appendix: web page database, 1900-2010 Nuette Gordon Index.

Ecology and Conservation of Estuarine Ecosystems: Frontmatter

List of contributors Foreword Alan Whitfield Preface 1. South Africas first World Heritage Site Roger N. Porter 2. Management history Ricky H. Taylor 3. Geological history Greg A. Botha, Sylvi Haldorsen and Naomi Porat 4. The marine environment Allan D. Connell and Sean N. Porter 5. Catchment hydrology Derek D. Stretch and Andrew Z. Maro 6. The Wetlands William N. Ellery, Suzanne E. Grenfell, Michael C. Grenfell, Marc S. Humphries and Kirsten B. Barnes 7. Estuary and lake hydrodynamics Derek D. Stretch, Clint P. Chrystal, Robynne A. Chrystal, Christopher Maine and Justin J. Pringle 8. Groundwater hydrology Bruce E. Kelbe, Ricky H. Taylor and Sylvi Haldorsen 9. Physico-chemical environment Renzo Perissinotto, Nicola K. Carrasco and Ricky H. Taylor 10. Microalgae Renzo Perissinotto, Guy C. Bate and David G. Muir 11. Macrophytes Janine B. Adams, Sibulele Nondoda and Ricky H. Taylor 12. Benthic invertebrates Deena Pillay, Sarah J. Bownes and Holly A. Nel 13. Zooplankton Nicola K. Carrasco, Renzo Perissinotto and Hendrik L. Jerling 14. Penaeid prawns Anthony T. Forbes and Nicolette T. Forbes 15. Fish and fisheries Digby Cyrus 16. Birds Jane Turpie, Ricky H. Taylor, Meyrick Bowker and Caroline Fox 17. Crocodiles Xander Combrink, Jonathan Warner and Colleen T. Downs 18. Hippopotamuses Ricky H. Taylor 19. Alien and invasive species Nelson A. F. Miranda and Janine B. Adams 20. Food webs and ecosystem functioning Ursula M. Scharler and Fiona C. MacKay 21. Climate change impacts Andrew A. Mather, Derek D. Stretch and Andrew Z. Maro References Appendix: web page database, 1900-2010 Nuette Gordon Index.