Sea urchin cultivation, genetics and ecology

Dr. Nils T. Hagen (Full Professor)

With the participation of Dr. Brendan McAndrew (Professor II), Dr. Einar Skarstad Egeland (Associate Professor), Åsmund Andersen (PhD student), Ida Jørgensen (Master student), Ellen Sirnes (Technician)

Sea urchin research at HBO is focused on the development of sea urchin aquaculture (echiniculture), and the study of sea urchin outbreak dynamics. Successful sea urchin cultivation holds considerable commercial potential, and is particularly well suited to the natural conditions of Northern Norway. Hatchery production of sea urchins is now well established, and large numbers of larvae are generated for industrial scale growout experiments in both land and sea based cultivation systems. This is the only initiative of its kind in Scandinavia.

Outbreak populations of sea urchins have caused large scale destruction of kelp forest in Northern Norway, and have had an unprecedented negative impact on coastal biodiversity and benthic primary productivity. The ongoing outbreak was initiated 25 years ago. Shortly thereafter it was discovered that sea urchins in the outbreak area were infested by a previously unknown nematode parasite, which castrates and kills infected individuals. This new parasite is now common in the entire outbreak area, where it seriously affects the utilization of wild sea urchins and jeopardizes the prospect of sea based echiniculture. The best solution to this conundrum is to use disease resistant, hatchery-reared juveniles in all future sea based cultivation of sea urchins in Northern Norway. It is therefore a research priority to investigate the genetic basis of hereditary disease resistance in sea urchins, in order to identify a disease resistant variety suitable for both land and sea based cultivation.

Echiniculture and gonad quality

The HBO sea urchin hatchery has been in operation for 10 years, and has recently moved from being an experimental facility to a pilot scale commercial hatchery. It was established as a direct result of international research collaboration in the EU-project “Biology of sea urchins under intensive cultivation (closed cycle echiniculture)” (CT96-1623). Applying the knowledge gained in the husbandry of adult urchins, induced spawning, larval rearing and settlement of juvenile urchins is intended to raise production to 1 million juvenile urchins per annum. In the past year over 200,000 juvenile urchins were reared to a stage ready for commercial ongrowing. Poor or variable gonad colour is a serious quality problem, which has a detrimental effect on the commercial value of wild sea urchins. Current research is focussed on investigating the pigment (carotenoid) content of wild and cultivated sea urchins in order to find novel ways to improve gonad quality (EU-project CT-2004-512627).

Genetics and breeding

Norway has two potential candidate sea urchin species suitable for domestication, Strongylocentrotus droebachiensis and S. pallidus. We keep captive stocks of both species, and have successfully generated interspecific hybrids. Both species show a high level of phenotypic variation for test, spine, epidermis and very importantly, gonad colour. It would be of great importance to determine how much of this variation is genetically or environmentally determined in order to control the quality of cultivated sea urchins. S. pallidus also appears to be completely resistant to the endoparasitic nematode Echinomermella matsi, which castrates and kills wild S. droebachiensis in Northern Norway. The risk of natural infection is high in this region, and successful sea based echiniculture will require access to hatchery reared juveniles of a disease resistant variety. Hatchery production of juvenile sea urchins opens up the possibility to begin a programme of genetic improvement that will help solve some of the problems that are hindering the development of a potentially very profitable echiniculture industry. It is therefore timely to start development of the genetic tools needed to manage and improve hatchery populations and begin to assess the best species or strains for aquaculture.

Ecology

The current sea urchin outbreak has destroyed the kelp forest in Northern Norway, thereby causing the greatest reduction of marine biodiversity and primary productivity ever recorded in Norwegian waters. Kelp forests represent the largest concentration of submerged plant biomass in the marine environment, and harbour an abundance of associated plant and animal life. These aquatic forests flourish on the rocky shores of cool oceans, and reach their peak abundance in the northeast Atlantic along the Norwegian coast. Kelp forests are resilient to severe disturbances including storms and industrial harvesting, but are vulnerable to destructive grazing by outbreak populations of sea urchins. Destructive grazing leads to widespread formation of barren sea urchin dominated grounds with low biomass, low productivity and low biodiversity. Barren grounds may persist indefinitely, are energetically stable, and will require a very long time to restore their former biodiversity when or if they revert to kelp forest after several decades of sea urchin dominance. Sea urchin populations in the entire outbreak area are being castrated and killed by an unprecedented epizootic of the large endoparasitic nematode, Echinomermella matsi. This recently discovered parasite has spread rapidly throughout the outbreak area, and is the only known threat to the persistence of urchin dominated barren grounds in Northern Norway. Current research is focussed on sea urchin disease as a potential regulating mechanism in the coastal ecosystem.