From Tasmania to the world: long and strong traditions in seaweed use, research, and development

Abstract

Tasmania is an island state in south-eastern Australia that has a long and rich history of seaweed use, research, and development. It is a cool-temperate system with 750 macroalgal species currently described. Tasmanian Aboriginal peoples have lived on this land for at least 40,000 years utilising seaweed as food, shelter, water carriers and medicine, as well as for ceremonial reasons. Modern taxonomic investigations began with French naturalist Jacques-Julien Houtou de La Billardière in 1791, and there are 184 type specimens of seaweeds originating from Tasmania. Ecological and physiological studies of seaweed in Tasmania have focussed on the dominant large brown seaweeds (Laminariales and Fucales) and have contributed significantly to the global understanding of these systems, particularly related to community resilience, seaweed-urchin interactions, their habitat-forming role for other species, responses to global change, and restoration of lost habitat. Ocean warming and changing oceanography have caused a 95% decline in surface canopy cover of Macrocystis pyrifera in eastern Tasmania since the 1950s and led to a focus on restoring these lost forests. Tasmanian seaweed communities have a uniquely high proportion (up to ∼90%) of seaweeds that rely solely on CO2 for photosynthesis, which has implications for responses to ocean acidification. Tasmania has industries that use brown seaweeds for fucoidan extraction and beach-cast harvest for alginates, fertilisers, and feeds for agriculture. New aquaculture initiatives include integrated multi-trophic aquaculture, offshore kelp mariculture and Asparagopsis cultivation for bioactive products to reduce methane emissions in ruminants, as and the development of unexploited species including Caulerpa spp. for food.

The endemic kelp Lessonia corrugata is being pushed above its thermal limits in an ocean warming hotspot

“…It is possible that L. corrugata could become extinct or severely limited in distribution by 2100, particularly as it is at its geographic limit in Tasmania, as there is no suitable habitat (i.e., shallow rocky reef) further south. Indeed, largescale declines in L. corrugata populations have already occurred along Tasmania's coasts with >30% declines between 2008 and 2018 (Mellin et al., 2021); however, due to the lack of historical data and monitoring, the full extent of their decline is unknown (Hurd et al., 2023). Certainly, ocean warming in Tasmania has already led to extreme declines of another kelp, Macrocystis pyrifera , which has a similar thermal range to L. corrugata (Butler et al., 2020; Layton & Johnson, 2021; Schiel & Foster, 2015).…”

“…This raises concerns for the future of this unique, endemic species, as they appear to be highly sensitive to relatively small increases in temperature. It is possible that the species will be at an extinction risk if ocean warming continues at the current rate, with subsequent effects on entire ecosystems and the communities the kelp supports, which themselves have been almost completely unstudied (Hurd et al., 2023; Nardelli, Visch, Wright, et al., 2023). Moreover, recent studies have shown 100% mortality rates of farmed L. corrugata during summer (Nardelli, Visch, Farrington, et al., 2023); the narrow thermal range identified in our study further suggests that L. corrugata may not be suitable for aquaculture in a future, warmer ocean, particularly as temperatures are already reaching close to their thermal limits.…”

“…The kelp Lessonia corrugata is endemic to Tasmania, with a narrow latitudinal and geographic distribution (approx. 40.6–43.6° S; Nardelli, Visch, Wright, et al., 2023, Hurd et al., 2023). It is one of the few dominant species of kelp that supports diverse communities in shallow rocky reef systems along Tasmania's coasts.…”

Strong seasonal patterns of DOC release by a temperate seaweed community: Implications for the coastal ocean carbon cycle

“…Seasonal growth patterns of the red seaweeds Lenormandia marginata , Plocamium cirrhosum , Hemineura frondosa , Delisea plumosa , and Schottera nicaeensis have not been previously studied (Hurd et al, 2023). Therefore, the drivers of DOC release are considered based solely on their nitrogen status.…”

Thermal performance curves identify seasonal and site‐specific variation in the development of Ecklonia radiata (Phaeophyceae) gametophytes and sporophytes

“…The degree of spatial and temporal variability in zoospore quality and gametophyte development in E. radiata therefore remains a knowledge gap. Closing this gap will clarify the impacts of global warming on early life stages of this habitat‐forming species in Tasmania and enable more accurate predictions of growth and distribution through modeling (Assis et al., 2016; Castro et al., 2020; Davis et al., 2022; Franco et al., 2018; Hurd et al., 2023).…”