Discolored Red Seaweed <Emphasis Type="Italic">Pyropia yezoensis</Emphasis> with Low Commercial Value Is a Novel Resource for Production of Agar Polysaccharides

The red seaweed Pyropia yezoensis has been demonstrated to be a novel resource for the production of high-quality agar. P. yezoensis is grown for the food industry in large-scale Japanese mariculture operations. However, discolored P. yezoensis is mostly discarded as an industrial waste, although it has some kind of utility values. Here, we evaluated the utility of discolored P. yezoensis as a resource for agar production. The quality of agar from the discolored seaweed was comparable to that from normal seaweed. In addition, as a distinguishing characteristic, agar yield was higher from discolored seaweeds than from normal types. Moreover, we successfully used agar from discolored P. yezoensis for bacterial plate media and DNA electrophoresis gels without agarose purification. Thus, our results demonstrate that discolored P. yezoensis is suitable for agar production and use in life science research. Diverting discolored P. yezoensis from disposal to agar production provides a solution to the current industrial waste problem in mariculture, as well as a secure source of agar for research purposes.     

Agar extraction process for Gracilaria cliftonii ()

Agar extraction process was developed for Gracilaria cliftonii by investigating the effects of various extraction variables and alkali treatments on agar yield and properties. The tested variables were soaking time, soaking temperature, seaweed to water ratio of, extraction temperatures and extraction time. Alkali treatments were carried out in alkali concentrations of 1%, 2%, 3% and 5% in a water bath at 60, 70 and 80 °C prior to agar extraction. The results showed that agar yield was significantly affected by all the tested variables. The agar yield was maximised when extraction process was carried out with 1 h soaking time at 30 °C with seaweed to water ratio of 1:150 and extracted for 3 h at 100 °C. The alkali-temperature combinations significantly influenced agar yield and properties. Irrespective of temperature, alkali treatments at 3% and 5% significantly increased the gel strength.     

Stability of agar in the seaweed Gracilaria eucheumatoides (Gracilariales, Rhodophyta) during postharvest storage

The status of the cell-wall polysaccharide of the red seaweed, Gracilaria eucheumatoides upon postharvest storage was assessed in this study. The yield, chemical composition, physical and textural properties of alkali-treated agar extract was determined at different time intervals within 31 months of storage at dried state after harvest. Minimal fluctuation in agar yield was observed, ranging from 22.9% to 29.0%. The gel strength of agar extracts averaged 318gcm(-2) until the third month of storage but decreased considerably thereafter. The relative viscosity and molecular weight of the extracts varied inversely with storage time. Results indicated that both physical and textural parameters of agar generally decreased with storage time, likely due to depolymerization as indicated by decrease in molecular weight. Agar extracted from seaweeds up to 3 months of storage could be considered to exhibit gel quality suitable for food applications. Prolonged storage of the seaweed harvest is not recommended.     

Comparison of agarophytes (Gelidium, Gracilaria, and Gracilariopsis) as potential resources for bioethanol production

This study explores the possibility of producing ethanol using the acid hydrolysate of three abundant agar-containing red seaweeds (agarophytes): Gelidium amansii, Gracilaria tenuistipitata, and Gracilariopsis chorda. The main component in the seaweed samples was agar, which ranged from 20 to 51 % (g g^?1 dry weight). After optimizing acid hydrolysis, 100 g of seaweed was hydrolyzed at 130 °C for 15 min with 0.2 M H₂SO₄. Then, 120 mL of a 1:2 mixture of the hydrolysate broth and basal medium was fermented in a 200-mL bottle at 30 °C for 96 h. Of the three seaweeds, G. amansii had the best ethanol yield, producing 0.23 g g^?1 of galactose or 45 % of the theoretical yield. This yield increased to 60 % after detoxification of the hydrolysate with activated carbon.     

The effect of seaweed composite flour on the textural properties of dough and bread

Seaweeds as food and seaweed-derived food flavors, colors, and nutrients are attracting considerable commercial attention. In the baking industries, hydrocolloids are of increasing importance as bread making improvers, where their use aims to improve dough handling properties, increase the quality of fresh bread, and extend the shelf life of stored bread. Seaweeds contain a significant amount of soluble polysaccharides and have the potential function as a source of dietary fiber. In this study, red seaweed (Kappaphycus alvarezii) powder was incorporated (2–8 %) with wheat flour and used to produce bread. The effect of seaweed composite flour on dough rheological properties and the quality of bread was investigated using various techniques. Farinograph tests were applied to determine the effect of seaweed powder on the rheological properties of wheat flour dough, while texture profile analysis (TPA) was used to measure the textural properties of dough as well as the final product. The results showed that the additions of seaweed powder (2–8 %) increased the water absorption of the dough. TPA results showed that the addition of seaweed powder decreased stickiness properties. Bread produced with seaweed composite flour showed higher values of firmness.     

A decade of change in the seaweed hydrocolloids industry

Seaweed hydrocolloid markets continue to grow, but instead of the 3?C5% achieved in the 1980s and 1990s, the growth rate has fallen to 1?C3% per year. This growth has been largely driven by emerging markets in China, Eastern Europe, Brazil, etc. Sales of agar, alginates and carrageenans in the US and Europe are holding up reasonably well in spite of the recession. However, price increases to offset costs in 2008 and 2009 have begun to have a dampening effect on sales, especially in markets where substitution or extension with less expensive ingredients is possible. These higher prices have been driven by higher energy, chemicals and seaweed costs. The higher seaweed costs reflect seaweed shortages, particularly for carrageenan-bearing seaweeds. The Philippines and Indonesia are the dominant producers of the farmed Kappaphycus and Eucheuma species upon which the carrageenan industry depends and both countries are experiencing factors limiting seaweed production. Similar tightening of seaweed supplies are beginning to show up in brown seaweeds used for extracting alginates, and in the red seaweeds for extracting agar. The structure of the industry is also undergoing change. Producers in China are getting stronger, and while they have not yet developed the marketing skills to compete effectively in the developed world markets, they have captured much of their home market. China does not produce the red and brown seaweeds needed for higher end food hydrocolloid production. Stocking their factories with raw material has led to the supply problems. Sales growth continues to suffer from few new product development successes in recent years; although some health care applications are showing some promise, i.e., carrageenan gel capsules and alginate micro-beads.     

Historical context of commercial exploitation of seaweeds in Brazil

Harvested by coastal populations for centuries, seaweeds have played an important role in the economy of a number of countries. In Brazil, they occur along the coastline, but are more diversified and abundant from the northeast to a portion of the southeast coast. Historically, the seaweed industry in Brazil is based on seaweed harvesting of natural beds. This practice continues to this day in a number of coastal communities in Northeastern Brazil. Since the 1960s, species of the genera Gracilaria and Hypnea have been collected in the intertidal zone for extraction of agar and carrageenan. Maximum production was achieved in 1973–1974, a period in which the country exported around 2000 t annually (dry weight) to Japan. Later (1977–1979), there was a sharp drop and annual exports fell to 250 t (dry weight). In 1981, Brazil exported only 150 t of dried seaweed for agar extraction. Between 1990 and 2000, overexploitation, decline in a number of agarophyte populations, poor quality, low price, and lack of a socioeconomic policy led to the almost total disappearance of this industry in Northeastern Brazil. Seaweed harvesting on natural beds is currently in decline, and the population that depended on this resource had to migrate or convert to other economic activities, such as fishing, aquaculture, and underwater tourism. However, the promising results obtained in pilot projects (Gracilaria and Kappaphycus) show that Brazil has significant potential as a seaweed biomass producer.     

A molecular toolkit for the green seaweed Ulva mutabilis

The green seaweed Ulva mutabilis is an ecologically important marine primary producer as well as a promising cash crop cultivated for multiple uses. Despite its importance, several molecular tools are still needed to better understand seaweed biology. Here, we report the development of a flexible and modular molecular cloning toolkit for the green seaweed U. mutabilis based on a Golden Gate cloning system. The toolkit presently contains 125 entry vectors, 26 destination vectors, and 107 functionally validated expression vectors. We demonstrate the importance of endogenous regulatory sequences for transgene expression and characterize three endogenous promoters suitable to drive transgene expression. We describe two vector architectures to express transgenes via two expression cassettes or a bicistronic approach. The majority of selected transformants (50%–80%) consistently give clear visual transgene expression. Furthermore, we made different marker lines for intracellular compartments after evaluating 13 transit peptides and 11 tagged endogenous Ulva genes. Our molecular toolkit enables the study of Ulva gain-of-function lines and paves the way for gene characterization and large-scale functional genomics studies in a green seaweed.

Molecular cloning tools allow generating gain-of-function seaweed lines that will help to study seaweed biology.     

Latitudinal variations of the yield and quality of agar from <Emphasis Type="Italic">Gelidium robustum</Emphasis> (Gelidiales,Rhodophyta) from the main commercial harvest beds along the western coast of the Baja California Peninsula,Mexico

The yield and quality of agar from Gelidium robustum from the main commercial harvest beds along the western coast of the Baja California Peninsula (Mexico) were evaluated within a latitudinal range of about 800 km (31°47′N to 27°05′N). Samples from six locations, Bahía Todos Santos, El Rosario, Isla de Cedros, Islas San Benito, Punta Eugenia, and Bahía Asunción, were analyzed. Bryozoan, protein, and agar content in the seaweed were estimated. The agar quality was determined by the content of 3,6-anhydrogalactose, sulfate, gel strength, and gelling and melting temperature. All the values of these variables were correlated and then with the satellite-derived data of the sea surface temperature (SST), net primary production (NPP), and photosynthetic active radiation (PAR) measured at each harvest bed during the summer months (June, July, and August) of 2000. In the northern and central region, the agar yield was 35% to 37% (Bahía Todos Santos, El Rosario, Isla de Cedros, and Islas San Benito), whereas lower yields were obtained from the southern beds (Punta Eugenia and Bahía Asunción). In contrast, the agar quality increased from the northern to the southern beds. A lower gel strength was obtained from Bahía Todos Santos and El Rosario (268 ± 16 and 205 ± 5 gcm⁻²) with a higher gel strength obtained from Isla de Cedros, Islas San Benito, and Bahía Asunción (384 to 444 ± 25 gcm⁻²). Yield was not correlated with the bryozoan content but was inversely correlated with the protein content in the seaweed. The sulfate content in the agar was inversely correlated with the gel strength and with the melting temperature. The 3,6-anhydrogalactose content showed slight variations among harvested beds. Analysis of satellite-derived data showed an equatorward increase of the SST, NPP, and PAR. The agar content correlated inversely with the equatorward increase of the NPP, whereas agar quality, i.e., gel strength, correlated positively with the NPP and PAR. No significant effects were observed on the yield and quality of agar with the latitudinal change of the SST.     

In Vitro Antibacterial Activity of a Novel Resin-Based Pulp Capping Material Containing the Quaternary Ammonium Salt MAE-DB and Portland Cement

Background

Vital pulp preservation in the treatment of deep caries is challenging due to bacterial infection. The objectives of this study were to synthesize a novel, light-cured composite material containing bioactive calcium-silicate (Portland cement, PC) and the antimicrobial quaternary ammonium salt monomer 2-methacryloxylethyl dodecyl methyl ammonium bromide (MAE-DB) and to evaluate its effects on Streptococcus mutans growth in vitro.

Methods

The experimental material was prepared from a 2∶1 ratio of PC mixed with a resin of 2-hydroxyethylmethacrylate, bisphenol glycerolate dimethacrylate, and triethylene glycol dimethacrylate (4∶3∶1) containing 5 wt% MAE-DB. Cured resin containing 5% MAE-DB without PC served as the positive control material, and resin without MAE-DB or PC served as the negative control material. Mineral trioxide aggregate (MTA) and calcium hydroxide (Dycal) served as commercial controls. S. mutans biofilm formation on material surfaces and growth in the culture medium were tested according to colony-forming units (CFUs) and metabolic activity after 24 h incubation over freshly prepared samples or samples aged in water for 6 months. Biofilm formation was also assessed by Live/Dead staining and scanning electron microscopy.

Results

S. mutans biofilm formation on the experimental material was significantly inhibited, with CFU counts, metabolic activity, viability staining, and morphology similar to those of biofilms on the positive control material. None of the materials affected bacterial growth in solution. Contact-inhibition of biofilm formation was retained by the aged experimental material. Significant biofilm formation was observed on MTA and Dycal.

Conclusion

The synthesized material containing HEMA-BisGMA-TEGDMA resin with MAE-DB as the antimicrobial agent and PC to support mineralized tissue formation inhibited S. mutans biofilm formation even after aging in water for 6 months, but had no inhibitory effect on bacteria in solution. Therefore, this material shows promise as a pulp capping material for vital pulp preservation in the treatment of deep caries.     

Optimization of pretreatment conditions and use of a two-stage fermentation process for the production of ethanol from seaweed, Saccharina japonica

Saccharina japonica (Sea tangle, Dasima), a seaweed, was fermented in order to produce bioethanol after thermal hydrogen peroxide (H₂O₂) hydrolysis pretreatment and enzymatic saccharification. The optimal pretreatment conditions of 1% (v/v) H₂O₂ (28%, Dustan Pure Chemicals Co., Ltd, Ansan, Korea) and 10% (w/v) seaweed slurry at 121°C for 60 min were determined using the Response Surface Method (RSM). A reducing sugar yield of 33.4% (w/w) and a viscosity of 520 cP were obtained. Enzymatic saccharification was then carried out; a monosaccharide concentration of 28.5 g/L with a 40.5% (w/w) theoretical yield was obtained after the addition of 2-mL Celluclast® 1.5L to 100 g/L of seaweed slurry after thermal H₂O₂ hydrolysis. Fermentation of a two-stage ethanol production was carried out using Saccharomyces cerevisiae KCCM 1129 in order to ferment glucose in the first stage, and a high level of mannitol-acclimated Pichia angophorae KCTC 17574 to ferment mannitol in the second stage. Acclimation of yeast effectively slowed the uptake of sugar in ethanol fermentation. The overall ethanol yield from S. japonica after the two-stage fermentation was 9.9 g/L.     

The consumption of seaweed as a protective factor in the etiology of breast cancer: proof of principle

Daily consumption of seaweed has been proposed as a factor in explaining lower postmenopausal breast cancer (BC) incidence and mortality rates in Japan. This clinical trial assessed the impact of introducing seaweed- to non-seaweed-consuming American postmenopausal women. Fifteen healthy postmenopausal women were recruited for a 3-month single-blinded placebo controlled clinical trial; five had no history of BC (controls) and ten were BC survivors. Participants ingested ten capsules daily (5 g day^?1) of placebo for 4 weeks, seaweed (Undaria) for 4 weeks, then placebo for another 4 weeks. Blood and urine samples were collected after each treatment period. Urinary human urokinase-type plasminogen activator receptor concentrations (uPAR) were analyzed by ELISA, and urine and serum were analyzed for protein expression using surface-enhanced laser desorption/ionization–time-of-flight mass spectrometry (SELDI-TOF-MS). Urinary creatinine standardized uPAR (in pg mL μg^?1 creatinine) changed significantly between groups, decreasing by about half following seaweed supplementation (placebo 1, 1.5 (95 % CI, 0.9–2.1) and seaweed, 0.9 (95 % CI, 0.6–1.1) while placebo 2 returned to pre-seaweed concentration (1.7 (95 % CI, 1.2-2.2); p?=?0.01, ANOVA). One SELDI-TOF-MS-identified urinary protein (m/z 9,776) showed a similar reversible decrease with seaweed and is reported to be associated with cell attachment. One serum protein (m/z 8,928) reversibly increased with seaweed and may be the immunostimulatory complement activation C3a des-arginine. uPAR is higher among postmenopausal women generally, and for BC patients, it is associated with unfavorable BC prognosis. By lowering uPAR, dietary seaweed may help explain lower BC incidence and mortality among postmenopausal women in Japan.     

Radioisotope Assay for the Quantification of Sulfate-Reducing Bacteria in Sediment and Water

A radioisotope enrichment culture method was developed to estimate the physiologically active component of a population of sulfate-reducing bacteria in environmental water and sediment samples. Aliquots of water or sediment were added to 50-ml serum bottles filled with ³⁵S-sulfate broth incubated for approximately 30 h. After incubation, the disintegration rate per milliliter of spent medium was measured, and the percentage of loss of activity resulting from bacterial sulfate reduction was determined. This loss of sulfate from the medium was then translated to a specific number of Desulfovibrio desulfuricans cells that would reduce an equivalent amount of sulfate in the same incubation time. This comparison was done using a series of growth curves of D. desulfuricans covering a range of inoculum densities between 10² and 10⁷ cells. The radioassay was used to follow the effects of a pulp mill on a small anoxic river in Florida. The activity of the sulfate-reducing bacteria in the river was greatly suppressed when the mill was closed for annual maintenance. The initiation of waste treatment resulted in improved water quality in 1 week, but the river sediments required a month to show a 10-fold reduction in the population of sulfate-reducing bacteria.     

Impact of environmental changes on farmed seaweed and farmers: the case of Songo Songo Island,Tanzania

Tanzania, like many other countries where eucheumatoid seaweeds are farmed, is experiencing die-off of Kappaphycus alvarezii. Farming is failing in many cultivation sites in shallow intertidal areas where it used to grow well. Production has fallen dramatically, and in some areas, hardly any seaweed is produced any longer. This study was carried out in Songo Songo Island, southern Tanzania, one of the most affected areas, during February–May 2009. Water temperature averaged 35.7?±?2.4 °C, higher than what had been observed in seaweed farms in other areas in Tanzania. Salinity was normal seawater at 34.7?±?0.5 ppt. In the abandoned farming sites, signs of ice-ice, epiphytic Neosiphonia and “dark spots” were observed on the seaweed. Fouling was also observed. Seaweed production decreased from 423.9 t worth US$82,000 in 2003 to 26 t in 2008 worth only US$4,500, and 28 t in 2012 worth US$4,300. Number of farmers was highest (809) during the production peak in 2003 then decreased to 320 in 2008. The number of fishing vessels decreased with an increase in number of farmers and seaweed production and increased when the number of farmers and seaweed production fell. Thus, high-surface water temperatures coupled with fouling, epiphytism, and ice-ice disease signs have caused dramatic decrease in seaweed production in Songo Songo. The onetime lucrative seaweed farming activity in Songo Songo Island of Tanzania has been reduced to almost standstill.     

Selective Enrichment with a Resuscitation Step for Isolation of Freeze-Injured Escherichia coli O157:H7 from Foods

We studied injury of Escherichia coli O157:H7 cells in 11 food items during freeze storage and methods of isolating freeze-injured E. coli O157:H7 cells from foods. Food samples inoculated with E. coli O157:H7 were stored for 16 weeks at −20°C in a freezer. Noninjured and injured cells were counted by using tryptic soy agar and sorbitol MacConkey agar supplemented with cefixime and potassium tellurite. Large populations of E. coli O157:H7 cells were injured in salted cabbage, grated radish, seaweed, and tomato samples. In an experiment to detect E. coli O157:H7 in food samples artificially contaminated with freeze-injured E. coli O157:H7 cells, the organism was recovered most efficiently after the samples were incubated in modified E. coli broth without bile salts at 25°C for 2 h and then selectively enriched at 42°C for 18 h by adding bile salts and novobiocin. Our enrichment method was further evaluated by isolating E. coli O157:H7 from frozen foods inoculated with the organism prior to freezing. Two hours of resuscitation at 25°C in nonselective broth improved recovery of E. coli O157:H7 from frozen grated radishes and strawberries, demonstrating that the resuscitation step is very effective for isolating E. coli O157:H7 from frozen foods contaminated with injured E. coli O157:H7 cells.     

Evaluation of kappa carrageenan as a substitute for agar in microbiological media

Seventy-one samples of the colloid kappacarrageenan extracted from 12 seaweed species were subjected to a number of standard physical demands of solid bacteriological culture media. All samples had a lower melting temperature (less than 67° C) than agar and a gelling (setting) temperature between 16° C and 51° C, some the same and others lower or higher than agar. Temperature spreads were narrow (ca 10° C) to broad (ca 30° C), depending on the seaweed source, but none were as broad as that of agar (ca 40° C). The majority of commercially prepared samples held a slant when incubated at 37° C, but California seaweed colloids were best at 28° C in this test. The majority of samples released little to no water of syneresis in slant tests as well as in plates. Some plates prepared with the colloid were crystal clear as compared to agar plates. All test microorganisms grew as well on kappa-carrageenan media as on agar media. Some media responses could be attributable to the seaweed species, but others could be traced to chemical extraction methods and modification of the colloid.     

Phycological research in the development of the Chinese seaweed industry

The term seaweed industry is employed in a broad sense and includes production both of commercial seaweeds such as Laminaria and Porphyra by phycoculture and of processed seaweed products, such as algin, agar and carrageenan.Before the founding of the People's Republic, China had a very insignificant seaweed industry, producing small quantities of the purple laver Porphyra and the glueweed Gloiopeltis by the primitive rock-cleaning method and the kelps Laminaria and Undaria by the primitive stone-throwing method, both aiming at enhancing the growth of the wild seaweeds. Also, a small quantity of agar was manufactured by the traditional Japanese method of gelling, freezing, thawing and drying the product. The small production was not sufficient to meet the demand of the Chinese people who for ages have appreciated seaweeds and their products for food. Therefore, large quantities of seaweeds and seaweed products had to be imported from various countries, for instance, Eucheuma and Gracilaria from Indonesia and other southeastern Asian countries, Laminaria and agar from Japan, even Porphyra from the USA. Annual Laminaria import from Japan generally amounted to over 10 000 tons and in some years approached 20 000–30 000 tons. Some quantities of the glueweed Gloiopeltis and the vermifuge weed Digenea simplex were exported, mainly to Japan.Since the founding of the People's Republic of China in October, 1949, China has exerted efforts to build up a self-supporting seaweed industry. Now after a lapse of 30-some years, a sizable seaweed industry has been developed. China is now able to produce by phycoculture more than one million tons of fresh seaweeds, including Laminaria, Undaria, Porphyra, Eucheuma, Gracilaria etc. and several thousand tons of seaweed extracts, including algin, agar, carrageenan, mannitol and iodine. At present, China still imports some quantities of seaweeds and seaweed products from various countries but is able to produce sufficient quantities to meet the people's need and even to export some quantities of the seaweeds Laminaria, Undaria and Porphyra and the seaweed products algin and mannitol.At the Tenth International Seaweed Symposium, I presented a paper on the Marine Phycoculture of China, in which I emphasized on the methods of cultivation (Tseng 1981b). Therefore I would like to take this opportunity to supplement the last lecture by presenting a paper on the role of phycological research in the development of China's seaweed industry.     

Rapid and Pervasive Occupation of Fallen Mangrove Leaves by a Marine Zoosporic Fungus

Samples of leaves of red mangrove (Rhizophora mangle) were incubated on an agar medium selective for pythiaceous oomycetes. Leaves on trees above the water did not contain oomycetes. Marine oomycetes, principally Phytophthora vesicula, had colonized leaves within 2 h of leaf submergence, probably finding them by chemotaxis. The frequency of occurrence of P. vesicula in submerged leaves reached 100% within 30 h of submergence. By 43 h most, if not all, parts of leaves were occupied, and surface treatment with a biocide indicated that leaves were occupied internally. Frequencies of P. vesicula remained near 100% through about 2 weeks of submergence and then declined to about 60% in older (≥4 weeks) leaves. Leaves of white mangrove (Laguncularia racemosa) were also extensively occupied by P. vesicula after falling into the water column, but decaying leaves of turtlegrass (Thalassia testudinum) were not colonized by oomycetes. Ergosterol analysis indicated that the standing crop of living, non-oomycete (ergosterol-containing) fungal mass in submerged red-mangrove leaves did not rise above that which had been present in senescent leaves on the tree; decaying turtlegrass leaves had an ergosterol content that was only about 2% of the maximum concentration detected for red-mangrove leaves. These results suggest that oomycetes are the predominant mycelial eucaryotic saprotrophs of mangrove leaves that fall into the water column and that for turtlegrass leaves which live, die, and decompose under submerged conditions, mycelial eucaryotes make no substantial contribution to decomposition.     

Comparing the Relative Importance of Water-Borne Cues and Direct Grazing for the Induction of Defenses in the Brown Seaweed Fucus vesiculosus

Some seaweed species have been shown to release water-borne cues after herbivore attack, for example, to attract natural enemies of the herbivore. These cues may also be sensed by neighboring seaweeds and used to adjust their defenses in anticipation of a possible herbivore attack. Several studies indicated information transfer between seaweed individuals in the past, including the brown seaweed Fucus vesiculosus. Previous work showed induction of defenses in F. vesiculosus in response to water-borne cues released by isopod-grazed conspecifics. In contrast, another study on induced responses after exposure to cues from isopod-grazed neighbors using the same seaweed species yielded contradictory results. This study reassessed the ability of F. vesiculosus individuals to sense water-borne cues released by isopod-grazed neighbors in a series of experiments that monitored F. vesiculosus palatability in response to direct grazing by Idotea baltica and water-borne cues from isopod-grazed neighbors relative to unmanipulated seaweed pieces. Two-choice feeding assays were conducted with both fresh and reconstituted seaweed pieces. Direct grazing by I. baltica induced a chemical defense in F. vesiculosus, confirming results of previous studies. In contrast, evidence for increased herbivore resistance in seaweed pieces that were located downstream of isopod-grazed F. vesiculosus could not be provided. The lack of defense induction in response to grazing of conspecific neighbors may be explained by the environmental conditions and the scattered distribution of F. vesiculosus individuals in the intertidal zone of Helgoland, which may render resource investment in the emission and/or response to water-borne cues at this site unprofitable.