Enteric fermentation from livestock accounts for over a quarter of the United States' methane emissions. A potent greenhouse gas, methane has 80 times the global warming potential of carbon dioxide over a 20-year period. An emerging focus of research is the incorporation of algae (e.g., kelp, seaweed or microalgae) into livestock feed, with several studies documenting dramatic suppression of enteric methane emissions in cattle. As part of a nationwide multidisciplinary study of using algae feed supplements to reduce methane emissions and improve dairy productivity, we used focus groups and individual interviews to measure organic and conventional dairy farmer's knowledge and opinions of algae-based feed supplements. Our goals were to learn what both organic and conventional dairy farmers know about algae-based feed supplements, why they do or do not feed them to their cows and if they were interested in the methane-reducing potential of these algal-based feeds. We also sought to understand where they get valued information about animal nutrition. We found most farmers were aware of algae-based feed supplements on the market, but organic farmers were more familiar with marketing claims. Farmers reported feeding algae-based feed supplements to address herd health concerns, especially reproductive issues and pink eye, but expressed rising costs of the supplements as an obstacle. Both organic and conventional farmers expressed interest in suppressing methane emissions, but only if incentives are provided. Lastly, participants receive trusted information about feed supplements from their dairy nutritionists, who help them make decisions around feed purchasing and rations.

One of the most critical ecosystem functions provided by shallow coastal habitats is as nurseries for the juveniles of fish. Many of the studies that have assessed the nursery function of structurally complex coastal habitats have compared seagrass with unstructured sand and mud and as such, seagrass has emerged as the most important coastal nursery habitat for juvenile fishes. Although considerably less work has focussed on the nursery provision of structurally complex macroalgae within coastal nursery seascapes, recent work has started to highlight that the nursery provision of canopy-forming macroalgae may in fact be comparable with that of seagrass. This review collates research published on the important nursery role of macroalgae within both tropical and temperate coastal seascapes and highlights the importance of smaller canopy-forming brown algae from the Fucalean genera (particularly Sargassum spp.) as core nursery areas for juvenile fishes, particularly emperors (Lethrinidae), rabbitfishes (Siganidae), wrasse and parrotfishes (Labridae), goatfishes (Mullidae), groupers (Serranidae), surgeonfish (Acanthuridae) and damselfish (Pomacentridae) within tropical back-reef systems. Similarly, in temperate nursery seascapes, fucoid (Cystoseira spp.) and macroalgae-dominated reefs were important nursery habitats for damselfish (Chromis chromis), groupers and numerous species of wrasse and sparids (Sparidae). Although the overall density of juvenile fish was not shown to be higher in kelp relative to other temperate nursery habitats, kelp was important in the recruitment of Notolabrus celiodotus (wrasse), Paralabrax clathrus (Serranidae), Brachyistius frenatus (Embiotocidae), Heterostichus rostratus (Clinidae) and Sebastes spp. (Scorpaenidae). Although not interchangeable (fish communities were often different), the nursery function of structurally complex macroalgae was found to be similar to that of seagrass in both temperate and tropical seascapes.

Kelps, fucoids and other large brown seaweeds are common and important features of temperate coastal zones. The British Isles is a centre for seaweed diversity in the NE Atlantic, but, despite numerous surveys, an incomplete picture of the distribution remains. Survey data and herbarium specimens were used to examine the environmental preference of 15 species of large brown seaweeds, covering the orders Laminariales (kelps), Fucales (wracks) and one species of Tilopteridales. Habitat suitability models were developed to estimate broad-scale distribution and area of habitat created by these species around the British Isles. Topographic parameters were important factors limiting distributions. Generally, temperature did not appear to be a limiting factor, probably because the British Isles lies in the centre of the NE Atlantic distribution for most species, and not at climatic tolerance limits. However, for the recent migrant Laminaria ochroleuca, temperature was found to be important for the model, thus range expansion could continue northwards provided dispersal is possible. In contrast, the widespread Alaria esculenta showed a negative association with warmer summer temperatures. The total potential habitat around the British and Irish coastline is more than 19,000 km2 for kelps and 11,000 km2 for wracks, which represents a significant habitat area similar in scale to British broadleaf forest. We conclude that large brown algal species need to be managed and conserved in a manner that reflects their scale and importance.

In many coastal areas substrate is the limiting resource for benthic organisms. Some sessile species can be used as secondary substrate, reducing competition and increasing coexistence. In southern Chile, annual populations of Macrocystis pyrifera recruit and grow on the shells of Crepipatella fecunda. This study describes ecological interactions between the kelp and the slipper limpet over an annual cycle. The degree of kelp overgrowth was established by collecting sporophytes and through in situ submarine photography over a 10 month period (starting when kelp recruits became visible and ending when sporophytes were no longer present). Changes in the biochemical composition of the limpet tissue were also recorded by chemical analyses, to evaluate the potential effects (positive/neutral/negative) of kelp on C. fecunda nutritional condition. The results indicate that both species coexist, although kelp overgrowth may cause a decrease in carbohydrates in C. fecunda tissues, restricted to the period when the kelp forest reaches its maximum biomass. Individually, the short duration of the maximum overgrowth period and the size reached by C. fecunda females (up to 65 mm shell length) may enable rapid limpet recovery, avoiding competitive exclusion. On a population level, the M. pyrifera annual cycle generates the needed ‘break’ for C. fecunda populations, reducing the effects of kelp overgrowth. Thus, in the view of the neutral effect of kelp overgrowth, together with the positive effect of C. fecunda on M. pyrifera recruitment described somewhere else, this ecological interaction can be categorized as commensalism.

The epiphytic bryozoan Membranipora membranacea encrusts the surface of kelp blades, causing recurrent large-scale defoliation events in kelp beds off the Atlantic coast of Nova Scotia, Canada. The gastropod Lacuna vincta grazes kelp, creating perforations that weaken blade tissues and increase the fragmentation rate. We assess the interaction between M. membranacea and L. vincta by measuring the grazing rate of snails on bryozoan-encrusted and non-encrusted kelp (Saccharina latissima) in no-choice and choice experiments in the laboratory conducted in November and December 2010. There was no effect of diet on grazing rate in no-choice experiments. In choice experiments, however, L. vincta grazed significantly more non-encrusted than encrusted kelp (7.1 versus 1.1 mg snail−1 d−1), and grazing rate of non-encrusted kelp was almost twice that in the no-choice experiment (3.8 mg snail−1 d−1), indicating that snails may avoid colonies of M. membranacea on partially encrusted kelp blades. We found no effect of diet on growth, reproduction and survival of snails maintained for four weeks on encrusted or non-encrusted kelp. By concentrating grazing damage on non-encrusted areas of blades, L. vincta may act synergistically with M. membranacea to increase the likelihood of blade breakage and canopy loss. This indirect effect of the invasive bryozoan could augment its direct effect on the standing biomass of native kelp beds and detrital export to adjacent communities.

Marine protected areas (MPAs) have been depicted as a useful tool for improving fisherymanagement and protecting biodiversity. For example, by acting as source populations, MPAsmay provide a spillover of adults/propagules, enhancing recruitment to surrounding,non-protected waters. However, such positive effect will depend on how a MPAs designmatches population biology and dispersal abilities of the target species. High levels ofintraspecific genetic diversity without pronounced structure have been found in manymarine organisms over large spatial scales (from hundreds to thousands kilometres) but donot hold for other ecologically and economically important species such as coral reeffishes, seagrasses and kelps. In particular, the limited potential for dispersal of manymacroalgae suggests the occurrence of self-sustaining, “closed” populations that contrastwith the “open” populations of many fishes and invertebrates. Consequently, the highresilience of fish/invertebrate populations cannot be generalized to the whole marinerealm. In the present work, we use genetic tools to explore the role of the MPAParc naturel marin d’Iroise in the management of the emblematic kelpLaminaria digitata. While kelps have received much more scientificattention than any other seaweed group, there is still critical baseline knowledge whichneeds to be addressed for their effective management. Our genetic survey of 12 L.digitata populations along the Brittany coast, four of them located within theboundaries of the Parc naturel marin d’Iroise, allowed us to assess theconservation value of these kelp populations. In particular, classical genetic metrics aswell as more recent clustering approaches were used to identify and characterizeManagement Units. Moreover, assignment tests were employed to determine contemporarymigration events and source/sink populations. Our results show that populations withinthis MPA have high conservation value. However, we also identify other populations ofconservation interest.

All habitats are modified to some extent by the species that live within them. Kelp is known to have a very strong influence on the surrounding environment providing a habitat for a wide range of organisms including marine mammals, fish and invertebrates. Here we examine the consequences of a subtle shift in the relative abundance of two species of kelp, Laminaria digitata and Laminaria ochroleuca, and compare the holdfast epibiont assemblages on both. These species are morphologically very similar and both provide important biologically generated habitats. The distribution of these kelp species is predicted to alter as a consequence of climate change with L. ochroleuca extending its range northward and potentially outcompeting L. digitata in the north-eastern Atlantic. The epibiont fauna common to both species of kelp were predominantly made up of annelids, molluscs and bryozoans. Most of the epibiont flora we found on the holdfasts was from the class Rhodophyceae. Multivariate analysis showed that the richness of epibiont species associated with L. ochroleuca was significantly lower, a mean of 0.62 species per cm3, when compared to the northern species, L. digitata which had a mean of 1.13 species per cm3. Laminaria digitata also had more unique epibiont species indicating that species richness of holdfast assemblages is likely to decline if L. digitata is replaced by L. ochroleuca. These data illustrate the importance of studying biologically generated habitats when considering the potential consequences of climate change on marine assemblages.

Erosion of bedrock from lower intertidal reefs by waves acting on attached plants of bull-kelp (Durvillaea antarctica) was investigated over one year at Macquarie Island, Southern Ocean. At a site on the more sheltered east coast, such erosion occurred during four separate storms, each casting up 834–1078 large kelp plants km−1 of coast, of which 30–45% were still attached to jagged, freshly quarried bedrock fragments over 2.5 cm long. The largest fragment weighed was 74.6 kg; rounded cobbles and boulders attached to kelp plants and weighing up to 102.2 kg (and probably more than 160 kg) were also cast up on beaches. 19–21% of the standing crop of large kelp plants was removed by storms during the year of observation. Break points for 10 kelp stipes were found to be at least 90–161 kg. Total annual erosion by kelp-plucking is at least 1.56 tonnes of rock km−1 of coast. However, in terms of erosion this computes to only 0.1 mm yr−1, far below the rate of uplift of the island.

Previous laboratory studies in species of the Laminariales have revealed that both the onset of growth in early winter and the summer drop in growth rate are controlled by the annual course of daylength synchronizing endogenous, circannual clocks within the thallus. Moreover, it is known for some laminarian species that cultivation in the laboratory in constant short days (SD) leads to arhythmic, continuous growth activity of the blade throughout the year. Such a prolonged SD treatment has now been performed for the first time in outdoor-cultivated Laminaria digitata. Field-grown sporophytes were collected in May from the sea near Helgoland (North Sea) and cultivated on the island of Sylt (North Sea) in temperature-controlled outdoor tanks (300 l) at 10 °C for 1·5 years either in a constant 8 h of light per day, controlled by an automatic blind on top of the tank, or in ambient daylengths. In constant SD, the growth rate remained at a steady-state level of approximately 0·4 cm day−1 from the end of June until mid-October, whereas growth rate in ambient daylengths declined steadily after June to half the rate in SD in October. Growth became light-limited between October and February in both treatments and, in the second year from July onwards, higher growth rates were again observed in constant SD than in ambient daylengths. Further work is required to find out whether SD treatment in summer would also prevent the summer drop in growth rate in other perennial seaweed species, e.g. commercially valuable red algae. This would potentially increase the chance of more constant biomass production throughout the year, and decrease the danger of the cultivated perennial algae being overgrown by annual epiphytes in summer.

The brown algal family Chordaceae contains the single genus Chorda with two terete unbranched species, C. filum and C. tomentosa. They share a similar superficial morphology, but differences in anatomy and reproductive characters have made assignment to a single genus controversial. Comparison of DNA sequences of variable parts of the small subunit of the nuclear ribosomal cistron, and of relatively conserved areas of both internal transcribed spacers, of several taxa of the Sporochnales–Desmarestiales–Laminariales complex revealed that the two species of Chorda are not closely related and do not form a clade. This is taken as support for recognition of Halosiphon tomentosus (Lyngbye) Jaasund, although it was originally based on the erroneous observation of a Streblonema-like gametophyte in the life history of H. tomentosus.