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The rapid expansion and globalization of the seaweed production industry, combined with rising seawater temperatures and coastal eutrophication, has led to an increase in infectious diseases and pest outbreaks. Here, we propose a novel Progressive Management Pathway for improving Seaweed Biosecurity.

Each year a significant proportion of global food production is lost to pests and diseases, with concerted efforts by government and industry focussed on application of effective biosecurity policies which attempt to minimise their emergence and spread. In aquaculture the volume of seaweeds produced is second only to farmed fish and red algal carrageenophytes currently represent approximately 42% of global production of all seaweeds. Despite this importance, expansion of the seaweed sector is increasingly limited by the high prevalence of recalcitrant diseases and epiphytic pests with potential to emerge and with the demonstrated propensity to spread, particularly in the absence of effective national and international biosecurity policies. Developing biosecurity policy and legislation to manage biosecurity risk in seaweed aquaculture is urgently required to limit these impacts. To understand current international biosecurity frameworks and their efficacy, existing legislative frameworks were analysed quantitatively for the content of biosecurity measures, applicability to the seaweed industry, and inclusion of risks posed by diseases, pests and non-native species. Deficiencies in existing frameworks included the following: inconsistent terminology for inclusion of cultivated seaweeds, unclear designation of implementation responsibility, insufficient evidence-based information and limited alignment of biosecurity hazards and risks. Given the global importance of the cultivation of various seaweeds in alleviating poverty in low and middle income countries, it is crucial that the relatively low-unit value of the industry (i.e. as compared with other aquatic animal sectors) should not conflate with a perceived low risk of disease or pest transfer, nor the subsequent economic and environmental impact that disease transfer may impact on receiving nations (well beyond their seaweed operations). Developing a clear basis for development of robust international biosecurity policies related to the trade in seaweeds arising from the global aquaculture industry, by first addressing the gaps highlighted in this study, will be crucial in limiting impacts of pests and diseases on this valuable industry and on natural capital in locations where seaweeds are farmed.

Farmers are one of the most important components of any plant-based cultivation industry. The Philippines is one of the world’s major producers of red carrageenophyte algae and has tens of thousands of farmers involved in this industry. The production of algae such as Kappaphycus and Eucheuma increased significantly from the early 1970s, when the industry was established, before declining from the mid-2000s, due to a number of reasons, including disease and epiphyte outbreaks. The introduction of biosecurity measures has been one approach used to tackle this decline. Biosecurity-related knowledge, attitude and practices (KAP) of the seaweed farmers were assessed in the four highest seaweed producing regions in the Philippines: (1) Tawi-Tawi, (2) Palawan, (3) Zamboanga and (4) Bohol. Analyses showed that seaweed farmers from Tawi-Tawi had relatively higher KAP mean scores than the other three sites. Palawan and Bohol farmers, however, scored lower on their knowledge, higher on their attitude and highest on their practices compared with the other areas. Farmers from Zamboanga scored the lowest in both their attitude and practice mean scores, although their knowledge score was one of the highest. This is the first KAP assessment applied to the seaweed farming industry globally and the results, in which the farmers’ biosecurity-related knowledge and practices, which scored “Fair” (50–75%) across all the regions, and their attitudes, which scored predominantly “Good” (> 75%) suggest that there is potential to raise the score for biosecurity practices. This assessment highlights how biosecurity challenges are currently addressed by seaweed farmers in the Philippines and suggests how the KAP survey could be used as a tool by policymakers and scientists to address gaps in biosecurity management practices.

Farmed eucheumatoids are the top aquaculture commodity in the Philippines, contributing more than 60% of total national aquaculture production by volume. Despite significant production losses observed in recent years due to pests and diseases, data relating to the temporal and spatial geographic distribution, seasonality, prevalence, and etiology of these critical problems at the farm level are lacking. Here, we assessed the prevalence of pests and diseases at 16 farm sites within several major seaweed growing areas, including Luzon (Palawan), Visayas (Bohol), and Mindanao (Zamboanga City, Davao del Norte, and Tawi-Tawi). Prevalence of pests and diseases were recorded by assessment of individual seaweed plants in situ, comprising ≥5% of the total number of seaweed plants on each farm. Results from this survey revealed “ice-ice” disease (IID) at all sites, albeit at low prevalence rates of below 25%, the exception being one site where prevalence was 100%. No significant difference in the prevalence of IID was found between farms in shallow (≈0.5 m during low tide) and deep water sites (depths exceeding 4 m during the lowest tide) (p>0.05). Moderate prevalence (26–50%) of the macro-epiphyte pests Sargassum and Ulva was reported in Luzon. Further, epiphytic filamentous algae (EFA), black spots, and evidence of grazing were recorded in several farms with low prevalence (0.2–11.2%). The three farms with the highest prevalence of IID and EFA were evaluated to determine the severity of cover on the thallus of infected plants. A very high severity of IID (76–100% coverage) was observed on the secondary and primary branches, while for EFA, low severity (≤25%) was found in all regions of the thallus. Our results suggest the widespread occurrence of yield-limiting diseases and pests affecting eucheumatoid farms in the Philippines. Strategies for the diagnosis, surveillance, and management of yield-limiting pests and diseases are needed to ensure maintenance and sustainable expansion of this important aquaculture sector in the Philippines.

Micropropagation has proven to be a reliable method to mass produce certain crops. This method also has been applied in macroalgae to produce clones for seaweed farming. Protocols for callus production and shoot regeneration from protoplasts have been established for some seaweed species like Kappaphycus alvarezii. Cells and larger tissues, whether in solid or suspension medium, have been used to propagate clones which were later tested for suitability for farming. Although clonal production was successful, the long duration of culture in vitro limits the production process making the growing of Kappaphycus in vitro an expensive technique to produce clones. In this study, K. alvarezii was grown in vitro to develop a more efficient protocol for the production of clones. Small sections of Kappaphycus were grown in suspension for 1 month under the same temperature, light, and salinity. The type of media, source of explants, length of explants, and stocking density that resulted in the highest growth rate and survival rate were determined. Growth rate of K. alvarezii is significantly higher in media with inorganic nitrogen added than in Grund medium or Ascophyllum nodosum medium only. The appearance of shoot primordia as early as 5 days was observed in media with higher nitrogen concentration. Growth rates of explants approximately 3 and 5 mm are significantly higher than 10 mm sections. Shoots develop significantly faster in explants from tips than sections from older branches. Growth rate of K. alvarezii grown at 0.5, 0.75, 1, 1.25 s 10 mL−1 of medium is not significantly different. This protocol could significantly reduce the (1) time of culture and (2) cost of plantlets production by not using plant growth regulators and formulated media in vitro. Nursery reared plantlets/propagules for farming would be affordable to the stakeholders for sustainability of seaweed production.

The seaweed industry in the Philippines is a significant contributor to aquaculture production, both nationally and internationally. It out-produces the capture fisheries sector and most global producers, with the exception of China and Indonesia. Seaweed species, particularly Kappaphycus and Eucheuma spp., have been farmed throughout the country since the early 1970s. In 2017, the Philippines produced 1.4 million tonnes (fwt) and exported 35,490 tonnes of seaweed and carrageenan with a value of US$174 million. However, a decreasing trend in seaweed production has been observed since the mid-2000s as a result of pest and disease outbreaks, among other factors, which have been exacerbated by climate change. This paper is the first to analyze biosecurity-related national policies and legislation (a.k.a. ‘frameworks’ collectively), which are relevant to the seaweed industry in the Philippines. A total of 12 frameworks were identified, of which a sub-set of seven were compared using defined biosecurity themes, risks, and management measures to evaluate how seaweed biosecurity is incorporated into national policy. The inclusion of biosecurity-related activities in national frameworks was found to be limited to aquatic animal commodities or agricultural crops. Only the Code of Good Aquaculture Practices (GAqP) for seaweed specifically included seaweed cultivation, however, it did not include any biosecurity measures. The results indicated a clear gap in current biosecurity legislation and policy in the Philippines, which if addressed have the potential to reduce the impact of endemic and emergent diseases and pests and support the sustainable growth of this important industry.

A fixed off-bottom Kappaphycus striatus var. sacol farm was monitored for 12 months (June 2019 to May 2020) and the monthly incidence of disease and pests was recorded. Meteorological information in situ, from the nearest synoptic station and online data were collected to determine the relationships between temporal environmental changes and the incidence of seaweed health problems. The results showed that “ice-ice” disease (IID) was observed in dry months (i.e., from February to April 2020) and was significantly influenced by increased irradiance, salinity, sea surface temperature, and wind speed (p=0.004‒0.030). Also, the IID incidence was positively affected by reduced precipitation, storm surface run-off, water current speed, and inorganic nutrient (nitrite and ammonia) levels (p=0.002‒0.019). In comparison, epiphytic filamentous algae (EFA) were observed in wet months (i.e., from September to December 2019), with incidence varying from low to very high (≤25–100%) as the culture progressed. EFA incidence was significantly influenced by reduced salinity and increased storm surface run-off and inorganic nutrient (nitrate and ammonia) levels (p=0.006‒0.040). An intense tropical cyclone struck the farming area in December 2019, resulting in partial die-offs of farmed seaweed. Such seaweed health problems are expected to become more prevalent in the coming years as weather disturbances brought about by changing weather patterns become more frequent and intense. Hence, mitigation and preventative approaches must be fully considered to sustain the industry’s growth while protecting the livelihoods of many coastal communities dependent on seaweed farming.

Short-term immersion of Kappaphycus alvarezii (Doty) Doty in a high-nitrogen-containing medium was tested to increase growth, improve the quality of carrageenan, and decrease “ice-ice” disease occurrence. Tank-reared Kappaphycus were used as explants. Growth, nitrogen assimilation, carrageenan quality, and occurrence of ice-ice disease of enriched (E/N) K. alvarezii were determined. E/N and un-enriched (control) K. alvarezii were planted inside net cages in the sea. Nitrogen assimilation was monitored to determine if nitrogen was incorporated in the tissues after 12 h. Total thallus nitrogen of K. alvarezii doubled after immersion in high nitrogen. Growth rate and carrageenan yield of E/N K. alvarezii were significantly higher than those of the control. Gel strengths of E/N and the control were not significantly different. Ice-ice disease occurrence was significantly higher in the control than the enriched seaweeds. Short-term immersion of K. alvarezii in a high-nitrogen medium before outplanting increased growth rate and decreased the occurrence of “ice-ice”.