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According to recent evolutionary theory, many marine species should have evolved a variety of barriers to the rapid combination of sperm and eggs at fertilisation. Empirical observations support these predictions, revealing substancial inter-individual variation in fertilisability. This has profound operational and economic consequences for the viability of developing aquaculture industries that typically minimise costly maintenance of adult spawning stocks. We, in collaboration with Professor Jon Havenhand, will assess the extend of inter-individual variability in fertilisatioon sucess in sea urchins, the subject of an emerging aquaculture industry.

Ultraviolet radiation reaching the Earth's surface has increased dramatically over the last decade. The greatest increases have occured in Antarctica, with unknown consequences for its ecology and species diversity. I will examine worst and best-case scenarios for the impact of UV-B on a keystone species, the Antarctic sea urchin Sterechinus neumayeri, by assessing the chemical and microbial processes that regulate recruitment. Recruitment (larval settlement into an area) is a dynamic research area in marine ecology and incorporates a broad range of disciplines. The results of this work will help model long-term effects of UV-B in Antarctica.

This project addresses key questions of the Australian Antarctic Program. It will test the impact of increasing levels of ultraviolet light on Antarctic ecosystems, using a keystone organism in the Antarctic biota, the sea urchin Sterechinus neumayeri. I will examine the effects of global change on one of the largest and unspoiled ecosystems in the world. As custodians of a large portion of Antarctica, it is in the local and international interest of the country to conduct studies of this type.

For further information regarding this research, refer to Project Number 2501 in the Australian Antarctic Division

S. neumayeri

Aquaculture is Australia’s fastest growing primary production industry, with a growth rate of 15% per annum over the past five years. As well as culturing native species for food, aquaculture also has direct conservation benefits when these species are farmed for restocking. Some hormones have been shown to accelerate developmental rates in a range of vertebrate and invertebrate species.

This study tests the effects of two analogs of a hormone currently used in food production on the growth of barramundi, a hugely popular food fish and valuable native species of Australia. Incorporating these hormones into feed for barramundi has the potential to reduce the time the fish spend in culture prior to sale, and decrease the need to supply dietary supplements that are both costly and labour intensive. The benefits to this industry are significant.

Jane Williamson has been researching the nature and role of cues for settlement and metamorphosis of the sea urchin Holopneustes purpurascens for approximately eight years. This work has combined chemical and biological studies to identify, quantify and test the efficacy of ecologically relevant cues for settlement and metamorphosis of this Australasian urchin. It has addressed the relative importance of recruitment versus post-recruitment events in this organism, and has important implications for the ecology and evolution of invertebrate life histories and benthic communities in general.

Members of the Marine Ecology Group have also been heavily involved in the investigation of naturally derived settlement cues for a range of other invertebrate herbivores; including the sea urchins Heliocidaris erythrogramma and Centrostephanus rodgersii, the abalone Haliotis rubra, the opisthobranch Aplysia parvula, and the gastropod Phasianotrochus eximinus. This work has been done in conjunction with Associate Professor Peter Steinberg (University of New South Wales) and Associate Professor Rocky de Nys (James Cook University), and has been funded by a large ARC Grant (2000—2003) to UNSW. This research also has significant implications for enhancing settlement and development in aquaculture.

Herbivory, and plant-herbivore interactions is a particular focus for members in the Marine Ecology Group. There has been considerable research done on the effects of host plant choice on the performance (i.e., survival, growth and reproduction) of several marine herbivores, particularly sea urchins. Currently, collaborative research projects involving both juvenile and adult sea urchins, abalone and gastropods are underway and encompass a range of topics including the effect of urchin herbivory on temperate subtidal algal assemblages, and abalone herbivory on drift algae.

Jane Williamson is currently contrasting the direct and indirect effects of host plant choice by the gastropod Phasianotrochus eximius. Since P. eximinus preferentially inhabits the kelp Ecklonia radiata in association with the urchin H. purpurascens, it is hypothesized that these urchins may be indirectly responsible for host plant selection for this gastropod. Associational responses to recruitment, herbivory and predation are being investigated.

Past research on plant-animal interactions by Jane Williamson has included extensive research in intertidal and subtidal habitats. She has investigated the demography of the New Zealand crustose alga Pseudolithoderma sp. and its association with the honeycomb barnacle Chamaesipho columna. This involved an intensive study of several life-history stages of the alga, including recruitment, growth and senescence, along with manipulative experiments on both alga and barnacle in laboratory and field experiments. This crustose alga was found to have accelerated growth when occurring on C. columna due to a unique nutritional association between these species.

Jane has also examined the relationship between the sea urchin Holopneustes purpurascens and its two common host plants, the red alga Delisea pulchra and the kelp Ecklonia radiata. This was a subtidal study that involved demographic monitoring and a series of manipulative experiments to assess the relationship between urchin and algae.

Sea urchin gonad (or roe) is an increasingly desirable food item in various parts of the world and fetches very high prices. As an alternative to harvesting field stocks of urchins, which are now decreasing globally, there is considerable interest in sea urchin production through cultivation (echiniculture). The Marine Ecology Group is currently involved in a collaborative study with New South Wales Fisheries and James Cook University where the candidacy of the echinoid Tripneustes gratilla for echiniculture through ranching is being assessed.

Tripneustes gratilla is a highly conspicuous tropical sea urchin with a global distribution. It is large, and is commonly called the “lamington urchin” in Australia due to its black test and white spines (a lamington is a famous chocolate cake with coconut icing!). Although this urchin is currently harvested for roe in many countries worldwide, stocks are decreasing. In Australia, T. gratilla is abundant in tropical north Queensland and steadily decreases in density down the east coast to its temperate extent in southern New South Wales.

We believe that these temperate urchins originate in the tropics and are carried south as larvae in summer by the East Australian Current. Is this is the case, urchins in temperate waters may either not be reproductively viable, or spawning and the development of their larvae may be compromised.

Several studies are underway to examine the potential for ranching T. gratilla in New South Wales and Queensland waters. The first study examines the effect of temperature on the fertilisation kinetics and larval development of T. gratilla. A second study proposes to examine the phylogeography of T. gratilla in locations ranging from Townsville in tropical Queensland to the temperate climate south of Sydney. A further study is determining the effects of natural and artificial diets on somatic growth and reproductive viability of recruited urchins.

Phasianotrochus eximinus on the red alga Delisea pulchra

Jane Williamson has coordinated projects on spatial and temporal variation in the abundances of soft-bottom macro-invertebrates and the effect of storm-induced disturbances on their demography. Moreover, she has studied epifauna associated with different stages of the life history of the intertidal alga Pseudolithoderma sp. in New Zealand, and on common subtidal macroalgal species around Sydney.

The kinetics of ammonium and phosphate uptake in tropical algal turf communities in the southern Great Barrier Reef, and ammonium uptake on a temperate crustose alga in New Zealand have been studied by Jane Williamson. Both studies have focused on how uptake is affected by different nutritional past histories and the consequences these histories have on growth and survival of the algae. Moreover, the relative importance of grazing by fishes versus nutritional deficiencies was briefly assessed in tropical algae.

A further study examining the relative contribution of dissolved nitrogen (ammonium and dissolved free amino acids) to the nitrogen budget of the coral Pocillopora damicornis in different nutrient enriched clines on the Great Barrier Reef has been done in conjunction with Professor Ove Hoegh-Guldberg at Queensland University.