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To create carbon efficient sources of bioenergy feedstocks and feedstuff for aquaculture and terrestrial livestock, it is critical to develop and commercialize the most efficient seaweed cultivation approach with a sustainable nutrient input supply. Here, we present data for a novel, onshore tropical macroalgae cultivation system, based on influent deep seawater as the nutrient and carbon sources. Two red algal species were selected, Agardhiella subulata and Halymenia hawaiiana, as the basis for growth optimization. Highest productivity in small-scale cultivation was demonstrated with A. subulata in the 10% deep seawater (64.7 µg N L−1) treatment, growing at up to 26% specific growth rate day−1 with highest yields observed at 247.5 g m−2 day−1 fresh weight. The highest yields for H. hawaiiana were measured with the addition of 10% deep seawater up to 8.8% specific growth rate day−1 and yields at 63.3 g fresh weight m−2 day−1 equivalent. Biomass should be culled weekly or biweekly to avoid density limitations, which likely contributed to a decrease in SGR over time. With a measured 30–40% carbon content of the ash-free dry weight (20–30% of the dry weight) biomass, this translates to an almost 1:1 CO2 capture to biomass ratio. The compositional fingerprint of the high carbohydrate content of both Agardhiella and Halymenia makes for an attractive feedstock for downstream biorefinery applications. By focusing on scaling and optimizing seaweed farming technologies for large-scale onshore farms, the opportunities for yield potential, adaptability to cultivation conditions, and meeting global sustainability goals through novel, carbon-negative biomass sources such as seaweed can be realized. [ABSTRACT FROM AUTHOR]

Laminaria farlowii, golden kombu, is of interest as a novel species for aquaculture in Southern California, USA. Thermal biology and climate change resilience are important to the species' usefulness as a crop for the future. Wild populations of L. farlowii live primarily below the seasonal thermocline but individuals have been successfully cultivated in near surface conditions of light intensity and temperature. We examined the thermal biology of female gametophytes and juvenile sporophytes of L. farlowii. We grew the female gametophytes and juvenile sporophytes across gradients of temperature (9–20 °C) and light intensity (20–80 µmol photons m−2.s−1), finding growth rates were saturated by all light intensities tested and sensitive to temperature. Optimal growth temperatures were 16 °C for the female gametophytes and 15 °C for juvenile sporophytes. In a separate experiment, larger adult sporophytes were exposed to thermal regimes differing in mean temperature (10–20 °C) and thermal variability, under a photoperiod chosen to induce sorus formation. Growth rates were not significantly different from 14–18 °C but sori were formed only at a mean temperature of 15 °C. These results indicate that nursery and cultivation methods developed for a similar kelp, Saccharina latissima, are suitable for L. farlowii, and that the species can grow in the predominant coastal temperatures of Southern California. [ABSTRACT FROM AUTHOR]

Nonetheless, edible seaweed aquaculture production has increased and is projected to continue growth, with the states of Maine and Alaska leading the overall U.S. market share (Kim et al., 2019; Piconi et al., 2020). From February 9 to 12, 2020, we organized a special session at the Aquaculture of America meetings held at the Hawai'i Convention Center in Honolulu on the island of Oahu. Research shows that seaweed aquaculture in the ocean can be carried out sustainably with ecological engineering (Chopin et al., 2001; Chopin & Tacon, 2021) and taking into consideration the value and use of existing marine resources (Araújo et al. 2021). In North America, seaweed harvest accounts for less than 0.001% of total global seaweed production, while in 2019 the total U.S. edible seaweed market was around 7 million kg of dry weight (Piconi et al., 2020). [Extracted from the article]

Our team has initiated a selective breeding program for regional strains of sugar kelp, Saccharina latissima, to improve the competitiveness of kelp farming in the United States. Within our breeding program, we also include an endemic putative species, Saccharina angustissima, locally referred to as skinny kelp. We crossed uniclonal gametophyte cultures derived from 37 wild‐collected blades representing five sugar kelp strains and one skinny kelp strain to produce 104 unique crosses. Each cross was outplanted on a near‐shore research farm located in the Gulf of Maine (GOM). After the first farming season, our results indicated that sugar kelp and skinny kelp were interfertile, and produced mature and reproductively viable sporophytes. Morphological traits of individual blades varied depending on the parental contribution (sugar vs. skinny), with significant differences found in progeny blade length, width, thickness, and in stipe length and diameter. Despite these differences, wet weight and blade density per plot showed no statistical differences regardless of the cross. Given their published genetic similarity and their interfertility shown here, S. angustissima and S. latissima may not be different species, and may each contribute genetic diversity to breeding programs aimed at meeting ocean farming and market needs. [ABSTRACT FROM AUTHOR]

Kelpak® is a seaweed extract from the phaeophyte, Ecklonia maxima, used to enhance growth and production of terrestrial plants. It is also beneficial for some red and green seaweeds. As such, we assessed if Kelpak® could enhance growth and thermal tolerance of the brown seaweeds, Saccharina latissima and S. angustissima. Juvenile sporophytes were dipped (30 or 60 min) in Kelpak® solutions of different concentrations (0.001, 0.005, 0.05, 1, and 5 ml L−1). These sporophytes were then cultivated in half‐strength PES at different temperatures (12, 16, 19, 23 and 25°C ± 1) for 20 days. The surviving sporophytes were then moved to 18 ± 1°C and cultivated for 14 additional days. Results show that temperature was the main factor driving survival and growth. Both species exposed to the temperatures of 23 and 25°C died during the first 7 days. Furthermore, no significant differences were observed in growth of sporophytes at the temperatures of 12 and 16°C. Results also show that treated sporophytes exposed to 18°C, the sublethal temperature, particularly of S. angustissima showed a higher survival and overall vigor than nontreated sporophytes. These results indicate that Kelpak® may enhance thermal tolerance and growth of S. latissima and S. angustissima exposed to sublethal temperatures. [ABSTRACT FROM AUTHOR]

Ex situ seed banking was first conceptualized and implemented in the early 20th century to maintain and protect crop lines. Today, ex situ seed banking is important for the preservation of heirloom strains, biodiversity conservation and ecosystem restoration, and diverse research applications. However, these efforts primarily target microalgae and terrestrial plants. Although some collections include macroalgae (i.e., seaweeds), they are relatively few and have yet to be connected via any international, coordinated initiative. In this piece, we provide a brief introduction to macroalgal germplasm banking and its application to conservation, industry, and mariculture. We argue that concerted effort should be made globally in germline preservation of marine algal species via germplasm banking with an overview of the technical advances for feasibility and ensured success. Seaweed germplasm banking is an important resource for biodiversity conservation, human food security, and industry innovation. This Perspective article maintains that an international, coordinative initiative is needed to fully develop and capitalize on this resource. [ABSTRACT FROM AUTHOR]

Acadian Seaplants, Ltd., marine plant extract powder (AMPEP) is a commercially available extract derived from the brown seaweed, Ascophyllum nodosum. This extract is widely applied to increase the performance of land crops and has been reported to enhance growth of some seaweed crops. To assess the effects of AMPEP on the growth and thermal tolerance of Saccharina latissima and S. angustissima cultivars, we performed two experiments. First, juvenile sporophytes were dipped (i.e., 30 or 60 min) in AMPEP solutions of different concentrations (0.001, 0.005, 0.05, 1, and 5 g L−1). Sporophytes were then cultivated in half strength Provasoli's enriched seawater (PES) and allowed to grow at different temperatures (12, 16, 19, 23, and 25 ± 1 °C) for 20 days using a temperature gradient table. Photoperiod was maintained at 12:12 L:D with photosynthetically active radiation (PAR) of 90 ± 10 μmol photons m−2 s−1. Results show a differential response between the two species tested. Sporophytes of both species cultured at 23 and 25 °C died during the first 7 days post dipping in AMPEP. After the 20-day period, the surviving sporophytes were transferred to an incubator set at 18 ± 1 °C (i.e., LT50 after 20 days). These sporophytes remained for 14 additional days to assess for any delayed effect on thermal tolerance, with treated sporophytes showing a higher percentage of survival and growth than control sporophytes never exposed to AMPEP. Furthermore, after the 14-day incubation at 18 °C, treated sporophytes of both species showed blades more than three times thicker than control sporophytes. These preliminary results indicate that AMPEP may enhance the growth capacity of S. latissima and S. angustissima when exposed to suboptimal temperatures, allowing them to overcome heat stress more effectively while maintaining growth. [ABSTRACT FROM AUTHOR]

Anthropogenic disturbances, including coastal habitat modification and climate change are threatening the stability of kelp beds, one of the most diverse and productive marine ecosystems. To test the effect of temperature and irradiance on the microscopic gametophyte and juvenile sporophyte stages of the rare kelp, Saccharina angustissima, from Casco Bay, Maine, USA, we carried out two sets of experiments using a temperature gradient table. The first set of experiments combined temperatures between 7-18°C with irradiance at 20, 40, and 80 µmol photons m-2 s-1. The second set combined temperatures of 3-13°C with irradiance of 10, 100, and 200 µmol photons m-2 s-1. Over two separate 4-week trials, in 2014 and again in 2015, we monitored gametogenesis, the early growth stages of the gametophytes, and early sporophyte development of this kelp. Gametophytes grew best at temperatures of 8-13°C at the lowest irradiance of 10-µmol photons m-2 s-1. Light had a significant effect on both male and female gametophyte growth only at the higher temperatures. Temperatures of 8-15°C and irradiance levels of 10-100 µmol photons m-2 s-1 were conditions for the highest sporophyte growth. Sporophyte and male gametophyte growth was reduced at both temperature extremes--the hottest and coldest temperatures tested. S. angustissima is a unique kelp species known only from a very narrow geographic region along the coast of Maine, USA. The coupling of global warming with high light intensity effects might pose stress on the early life-history stages of this kelp, although, as an intertidal species, it could also be better adapted to temperature and light extremes than its subtidal counterpart, Saccharina latissima. [ABSTRACT FROM AUTHOR]

Saccharina latissima is a perennial kelp with a circumboreal distribution from the North Pacific to the North Atlantic coasts. Our study clarified the taxonomy of the morphologically distinct Saccharina latissima forma angustissima (Collins) A.Mathieson from the low intertidal zone on exposed islands and ledges of Casco Bay, Maine, USA. To identify genetic divergence between the two morphotypes, S. latissima and S. latissima f. angustissima, we used a multilocus phylogenetic approach including nuclear-encoded internal transcribed spacer, mitochondrial cox1 and cox3, and plastidencoded rbcL gene sequences. Genetic analysis of the individual markers and combined data set using SVDquartets resulted in p-distance values for all markers of , 1%, suggesting low divergence between the two forms. However, there was as much or more genetic divergence between S. latissima and S. latissima f. angustissima as there were between other taxonomically accepted species of Saccharina. To investigate sexual compatibility between the two forms, we made reciprocal crosses of the gametophytes and observed sporophyte formation. All crosses were successfully grown to the juvenile sporophyte stage, suggesting that the two are reproductively compatible in vitro. It is unknown if the two populations freely hybridize in the field. Last, we compared wave action, the ecological factor most likely driving the unique morphology, at exposed sites with S. latissima f. angustissima and protected sites with S. latissima. The mean wave force at the exposed site was over 30 times higher in magnitude than at the protected site at 160.04 6 32.58 N and 4.75 6 6.75 N, respectively, during the summer. The significant differences in morphology, the lack of specimens with intermediate morphologies, and the results of a common garden experiment suggest that the morphological differences in S. latissima f. angustissima are heritable with a genetic basis. Therefore, on the basis of our molecular evidence coupled with ecological studies, we are elevating S. latissima f. angustissima (Collins) A.Mathieson to specific rank as S. angustissima (Collins) Augyte, Yarish & Neefus comb. nov. & stat. nov. [ABSTRACT FROM AUTHOR]

Consumer interest and demand for North Atlantic sourced sea vegetables drives opportunities for aquaculture development in the northeast USA. The unique morphology and desirable culinary traits of the wild narrow-bladed kelp, Saccharina latissima forma angustissima, were successfully translated into a cultivated crop on two geographically distinct open-water farms in Maine, USA. Environmental conditions, growth, and tissue analysis were quantified. Peak meristematic growth rates for blade length occurred from March through April at 2.85 (±0.34) cm day. The kelp was harvested from May through June with yields of up to 17 (±4.4) kg m of line and plant density of 330 plants m of line at the Bristol farm and yields of 13.3 (±6.2) kg wet weight m line and a plant density of 400 plants m of line at the Sorrento farm. Second season yields at Sorrento were on average 24.1 (±6.3) kg m of line. Both farms grew significantly narrower blades of f. angustissima than of the sugar kelp, S. latissima. Common garden experiments with the two morphotypes identified trait stability for length and width, while blade ruffles and thickness varied with the environment. Calculations estimating the nutrient bioextraction capability of the cultivated f. angustissima kelp harvested in June reveal N removal of 88.7 kg ha and C removal of 1666.7 kg ha (combined farm site averages). Overall, this unique kelp form has the potential as a new aquaculture crop for the Gulf of Maine while providing several coastal ecosystem services. [ABSTRACT FROM AUTHOR]

There are few published studies examining the effects of invasive vascular plants on cooccurring nonvascular species, despite the fact that photoautotrophic algae and cyanobacteria exist at the base of the marine food web. This study tested whether the removal of the invasive dense-flowered cordgrass ( Spartina densiflora Brogn.) resulted in an increase in biomass of micro- and macroalgae in a salt marsh located in northern California. The site was sampled over a two-year time period, and percent cover of benthic algae was measured using a point-intercept technique in treated and control areas. Treatment consisted of selective mechanical removal of S. densiflora. The functional groups green filamentous and green sheet algae as well as diatoms and cyanobacteria were found. Growth peaks in algal biomass were significantly lower in the control compared to the treated areas. In addition, successional trends were observed in treated plots; green filamentous algae and diatoms were first to colonize, followed by cyanobacteria during the second year's growth. Our results suggest that the presence of S. densiflora lowers both algal biomass and functional group diversity in an invaded salt marsh, with implications for resulting trophic cascades. [ABSTRACT FROM AUTHOR]