a b s t r a c tAs a response to growing land and freshwater shortages and climate change, the use of seaweeds as food, their cultivation at sea and its effect on biodiversity are being researched on both the Caribbean and Pacific coasts of Costa Rica. Native species, more plentiful on the Caribbean coast, were collected and pre-selected based on existing information and on criteria including ubiquity, abundance, growth and palatability. These species were then evaluated as food and subjected to floating long-line cultivation using vegetative propagules. After establishing postharvest procedures, use as food involved many preparations to be eaten fresh or after drying, including a dry-ground meal. Ten of these species, which had nutrient contents within expected values including 9.8% crude protein on a dry weight (dw) basis and high iron, were considered adequate as food, both directly and as part of recipes in quantities not exceeding 20% dw of a given dish. Higher concentrations either 'overwhelmed' traditional recipes or their taste was rejected by tested consumers. Near-coast cultivation was in general a simple matter, easily transferred to artisanal fishers. To a great extent due to herbivory and theft of ropes, yield (ranging from 51.7 to 153.2 t ha −1 yr −1 on a fresh weight basis) was quantified for only five species with a mean of 9.3 t ha −1 yr −1 dw, equivalent to 0.91 t ha −1 yr −1 of crude protein-very similar to yields of two grain crops per year. Species of Codium, Gracilaria, Sargassum and Ulva were considered adequate both for use as food and cultivation. Cultivated seaweed plots rapidly attracted biodiversity, including a significantly larger number of fish species and individuals than nearby control areas. Based on this we postulate the need to further explore a 'biodiversity enrichment' service from seaweed cultivation and any effect of this on fisheries enhancement. While noting areas in which further research and international collaboration are needed, it is concluded that tropical seaweeds, besides their many other uses, can at this stage substitute up to 15% of food on a dry weight basis, their cultivation is simple, and effects on biodiversity are a previously undocumented advantage. Given the lack of experience in most of the world excepting some Asian countries, the agriculture-like approach followed here may be of use to others in tropical developing countries who wish to explore seaweed cultivation at sea, for food and other products and for environmental/biodiversity services.

Many taxa use conspicuous colouration to attract mates, signal chemical defences (aposematism) or for thermoregulation. Conspicuousness is a key feature of aposematic signals, and experimental evidence suggests that predators avoid conspicuous prey more readily when they exhibit larger body size and/or pattern elements. Aposematic prey species may therefore evolve a larger body size due to predatory selection pressures, or alternatively, larger prey species may be more likely to evolve aposematic colouration. Therefore, a positive correlation between conspicuousness and body size should exist. Here, we investigated whether there was a phylogenetic correlation between the conspicuousness of animal patterns and body size using an intriguing, understudied model system to examine questions on the evolution of animal signals, namely nudibranchs (opisthobranch molluscs). We also used new ways to compare animal patterns quantitatively with their background habitat in terms of intensity variance and spatial frequency power spectra. In studies of aposematism, conspicuousness is usually quantified using the spectral contrast of animal colour patches against its background; however, other components of visual signals, such as pattern, luminance and spectral sensitivities of potential observers, are largely ignored. Contrary to our prediction, we found that the conspicuousness of body patterns in over 70 nudibranch species decreased as body size increased, indicating that crypsis was not limited to a smaller body size. Therefore, alternative selective pressures on body size and development of colour patterns, other than those inflicted by visual hunting predators, may act more strongly on the evolution of aposematism in nudibranch molluscs.

An assessment of genetic diversity of marine populations is critical not only for the understanding and preserving natural biodiversity but also for its commercial potential. As commercial demand rises for marine resources, it is critical to generate baseline information for monitoring wild populations. Furthermore, anthropogenic stressors on the coastal environment, such as warming sea temperatures and overharvesting of wild populations, are leading to the destruction of keystone marine species such as kelps. In this study, we conducted a fine-scale genetic analysis using genome-wide high-density markers on Northwest Atlantic sugar kelp. The population structure for a total of 149 samples from the Gulf of Maine (GOM) and Southern New England (SNE) was investigated using AMOVA, F ST , admixture, and PCoA. Genome-wide association analyses were conducted for six morphological traits, and the extended Lewontin and Krakauer (FLK) test was used to detect selection signatures. Our results indicate that the GOM region is more heterogeneous than SNE. These two regions have large genetic difference (between-location F ST ranged from 0.21 to 0.32) and were separated by Cape Cod, which is known to be the biogeographic barrier for other taxa. We detected one significant SNP (P = 2.03 × 10 −7) associated with stipe length, and 248 SNPs with higher-than-neutral differentiation. The findings of this study provide baseline knowledge on sugar kelp population genetics for future monitoring, managing and potentially restoring wild populations, as well as assisting in selective breeding to improve desirable traits for future commercialization opportunities.

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,

Though Saccharina japonica cultivation has been established for many decades in East Asian countries, the domestication process of sugar kelp (Saccharina latissima) in the Northeast U.S. is still at its infancy. In this study, by using data from our breeding experience, we will demonstrate how obstacles for accelerated genetic gain can be assessed using simulation approaches that inform resource allocation decisions. Thus far, we have used 140 wild sporophytes (SPs) that were sampled in 2018 from the northern Gulf of Maine (GOM) to southern New England (SNE). From these SPs, we sampled gametophytes (GPs) and made and evaluated over 600 progeny SPs from crosses among the GPs in 2019 and 2020. The biphasic life cycle of kelp gives a great advantage in selective breeding as we can potentially select both on the SPs and GPs. However, several obstacles exist, such as the amount of time it takes to complete a breeding cycle, the number of GPs that can be maintained in the lab, and whether positive selection can be conducted on farm-tested SPs. Using the GOM population characteristics for heritability and effective population size, we simulated a founder population of 1000 individuals and evaluated the impact of overcoming these obstacles on rate of genetic gain. Our results showed that key factors to improve current genetic gain rely mainly on our ability to induce reproduction of the best farm-tested SPs, and to accelerate the clonal vegetative growth of released GPs so that enough GP biomass is ready for making crosses by the next growing season. Overcoming these challenges could improve rates of genetic gain more than two-fold. Future research should focus on conditions favorable for inducing spring reproduction, and on increasing the amount of GP tissue available in time to make fall crosses in the same year.

No abstract

The frequency of marine heatwaves (MHWs) is increasing due to climate change. Although seaweeds are resilient to environmental changes, an increasing body of evidence shows that rising sea surface temperatures have deleterious effects on temperate kelp species. However, information on the vulnerability of juvenile kelp to these stressors and their population stability is limited. This study summarizes findings on the ability of juvenile sporophytes of Macrocystis pyrifera to survive and recover from simulated MHW conditions (22°C, 5 d) in combination with nitrate limitation (<1 µM) by evaluating photosynthetic capacity, nitrate uptake, tissue composition, bio‐optical properties, and oxidative stress of single‐blade juvenile sporophytes (<20 cm). Temperature, nitrate availability, and their interaction had significant effects on the physiological status of juvenile sporophytes after the exposure and recovery periods. Overall, as expected, the photosynthetic capacity of juvenile sporophytes decreased with increased temperature and lower nitrate availability. Short‐term exposure to simulated MHWs resulted in oxidative damage and reduced growth. The termination of the experimental warming allowed partial recovery to control values, indicating high physiological resilience. However, the interaction of both high temperature and nitrate scarcity induced irreversible damage to their photosynthetic capacity, with an increase in compensation irradiance, highlighting potential limitations in the carbon balance of juvenile sporophytes.

This study was designed to understand better if and how juvenile sporophytes of Macrocystis pyrifera can photoacclimate to high‐light conditions when transplanted from 10 to 3 meters over 7 d. Acclimation of adult sporophytes to light regimes in the bathymetric gradient has been extensively documented. It primarily depends on photoacclimation and translocation of resources among blades. Among other physiological differences, juvenile sporophytes of M. pyrifera lack the structural complexity shown by adults. As such, juveniles may primarily depend on their photoacclimation capacities to maintain productivity and even avoid mortality under changing light regimes. However, little is known about how these mechanisms operate in young individuals. The capacity of sporophytes to photoacclimate was assessed by examining changes in their photosynthetic performance, pigment content, and bio‐optical properties of the blade. Sporophytes nutritional status and oxidative damage were also determined. Results showed that juvenile sporophytes transplanted to shallow water were able to regulate light harvesting by reducing pigment concentration, and thus, absorptance and photosynthetic efficiency. Also, shallow‐water sporophytes notably enhanced the dissipation of light energy as heat (NPQ) as a photoprotective mechanism. Generally, these adjustments allowed sporophytes to manage the absorption and utilization of light energy, hence reducing the potential for photo‐oxidative damage. Furthermore, no substantial changes were found in the internal reserves (i.e., soluble carbohydrates and nitrogen) of these sporophytes. To our knowledge, these results are the first to provide robust evidence of photoprotective and photoacclimation strategies in juveniles of M. pyrifera, allowing them to restrict or avoid photodamage during shallow‐water cultivation.